Composite articles with reduced discoloration and methods for promoting or reducing color change in composite articles - Patents.com

Abstract

Composite articles are described that can resist discoloration or color change. In some cases, the composite articles can include a blended material that is substantially free of antioxidants that changes from a first color to a second color upon exposure to an environment containing an oxidizing agent. The composite articles can also be flame retardant and provide sound reduction.

Description

[Technical field]

[0001] Priority Application This application is related to and claims priority to and the benefit of U.S. patent application Ser. No. 62 / 875,891, filed July 18, 2019, the entire disclosure of which is incorporated herein by reference for all purposes.

[0002] Technical Field Certain embodiments are directed to composite articles with reduced discoloration. In some examples, the composite articles may include one or more materials that inhibit or promote color change. [Background technology]

[0003] Background technology Composite articles have a variety of different performance requirements depending on the end use of the composite article. Environmental conditions or other factors may cause undesirable color changes in the composite article. Summary of the Invention

[0004] Certain embodiments are described below for composite articles that can be designed to resist or promote color change. The exact materials used in the composite article can vary depending on the desired color and end use of the article.

[0005] In one embodiment, a method of preventing color change of a flame retardant thermoplastic fiber reinforced porous core upon exposure to an environment comprising an oxidizing agent includes producing a flame retardant thermoplastic fiber reinforced porous core by combining a mixed material comprising reinforcing fibers, a first thermoplastic material, and a flame retardant mixed with a second thermoplastic material, wherein the flame retardant thermoplastic fiber reinforced porous core comprises a web formed from reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, and wherein the mixed material is substantially free of antioxidants that switch from a first color to a second color upon exposure to an environment comprising an oxidizing agent.

[0006] In certain embodiments, the blended material is substantially free of phenolic antioxidants. In other embodiments, the second thermoplastic material consists essentially of a polyolefin. In some examples, the polyolefin is polypropylene or polyethylene. In some configurations, the second thermoplastic material consists of a polyolefin. In additional examples, the polyolefin is polypropylene or polyethylene. In some examples, the flame retardant thermoplastic fiber reinforced porous core layer is stored in an environment containing an oxidizing agent for at least 24 hours without switching from a first color to a second color. In certain examples, the first thermoplastic material includes a polyolefin. In other examples, the reinforcing fibers include glass fibers, and the polyolefin of the first thermoplastic material includes polypropylene. In additional embodiments, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material includes a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0007] In another aspect, a method of reducing color change in a flame retardant thermoplastic fiber reinforced porous core includes producing a flame retardant thermoplastic fiber reinforced porous core by combining a mixed material including reinforcing fibers, a first thermoplastic material, and a flame retardant mixed with a second thermoplastic material, wherein the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, wherein the mixed material includes an antioxidant that changes from a first color to a second color upon exposure to an environment including an oxidizer present at a first concentration, wherein the antioxidant changes from the second color back to the first color upon exposure to an environment including an oxidizer present at a second concentration less than the first concentration, and wherein the flame retardant thermoplastic fiber reinforced porous core is stored in an environment including an oxidizer present at or less than the second concentration to maintain the flame retardant thermoplastic fiber reinforced porous core at the first color.

[0008] In certain examples, the antioxidant comprises a phenolic antioxidant. In some embodiments, the first thermoplastic material consists essentially of a polyolefin. In certain examples, the polyolefin is polypropylene or polyethylene. In other embodiments, the first thermoplastic material consists of a polyolefin. In certain embodiments, the polyolefin is polypropylene or polyethylene. In other embodiments, the method comprises the step of: removing NOx from the first thermoplastic material; .... In certain examples, the polyolefin is polypropylene or polyethylene. In other embodiments, the method comprises the step of removing NOx from the first thermoplastic material; removing NOx from the first thermoplastic material; removing NOx from the first thermoplastic material; removing NOx from the first thermoplastic material. X and storing the flame retardant thermoplastic fiber reinforced porous core layer in an environment comprising, for at least 24 hours, an antioxidant in the flame retardant thermoplastic fiber reinforced porous core changing from a first color to a second color. X removing the flame retardant thermoplastic fiber reinforced porous core layer from the environment comprising the flame retardant thermoplastic fiber reinforced porous core layer at or less than a second concentration of NO X and storing the flame retardant thermoplastic fiber reinforced porous core layer in an environment comprising: a first thermoplastic material layer and a second thermoplastic fiber reinforced porous core layer, the first thermoplastic material layer and the second thermoplastic fiber reinforced porous core layer having a first color and a second color, the second thermoplastic material layer and the second thermoplastic fiber reinforced porous core layer having a first color and a second color, the second thermoplastic material layer and the second thermoplastic fiber reinforced porous core layer having a first color and the ...

[0009] In an additional aspect, a method of preventing a color change in a flame retardant thermoplastic fiber reinforced porous core that includes a mixed material that includes an antioxidant is described. In a particular embodiment, the method includes shielding the flame retardant thermoplastic fiber reinforced porous core from exposure to an oxidizing agent in an environment surrounding the flame retardant thermoplastic fiber reinforced porous core to prevent the antioxidant from changing from a first color to a second color upon exposure to an environment that includes the oxidizing agent.

[0010] In certain examples, the shielding includes encasing the flame retardant thermoplastic fiber reinforced porous core with a material to prevent the oxidant from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core. In other examples, the shielding includes enclosing the flame retardant thermoplastic fiber reinforced porous core in a substantially airtight container to prevent the oxidant from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core. In some embodiments, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a thermoplastic material, and the porous core includes a coating on a first surface to prevent the oxidant from diffusing into the porous core. In other embodiments, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a thermoplastic material, and the porous core is sealed on each surface to prevent the oxidant from diffusing into the porous core. In certain embodiments, the thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core includes a polyolefin. In some cases, the polyolefin includes polypropylene. In other examples, the antioxidant is a phenolic antioxidant. In some embodiments, the reinforcing fibers of the thermoplastic fiber reinforced porous core include glass fibers. In a particular example, the flame retardant thermoplastic fiber reinforced porous core includes magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material includes a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0011] In another aspect, a method for changing the color of a flame retardant thermoplastic fiber reinforced porous core is described. In a particular embodiment, the method includes forming a flame retardant thermoplastic fiber reinforced porous core by combining a reinforcing fiber, a first thermoplastic material, and a mixed material including a flame retardant, an antioxidant, and a second thermoplastic material to form a web, and exposing the formed web to an environment including an oxidizing agent to change the color of the antioxidant in the flame retardant thermoplastic fiber reinforced porous core layer from a first color to a second color.

[0012] In certain configurations, the web is exposed to an environment including an oxidizing agent prior to compressing the web. In other instances, the web is exposed to an environment including an oxidizing agent after compressing the web. In some embodiments, the web is exposed to an environment including more than 2 ppm of an oxidizing agent prior to placing a skin on the web. In certain cases, the web is exposed to an environment including more than 2 ppm of an oxidizing agent after placing a porous skin on the web. In other embodiments, the first thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core includes a polyolefin. In some instances, the polyolefin includes a polypropylene. In other instances, the antioxidant is a phenolic antioxidant. In certain embodiments, the reinforcing fibers of the thermoplastic fiber reinforced porous core include glass fibers. In some instances, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material includes a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0013] In an additional embodiment, a thermoplastic composite article includes a porous core including reinforcing fibers, a first thermoplastic material, and a blended material including a flame retardant and a second thermoplastic material, the blended material being substantially free of an antioxidant that changes color upon exposure to an oxidizing agent, and the porous core includes a web formed from the reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material.

[0014] In certain examples, the second thermoplastic material consists essentially of a polyolefin. In some embodiments, the polyolefin is polypropylene or polyethylene. In other embodiments, the second thermoplastic material consists essentially of a polyolefin. In some cases, the polyolefin is polypropylene or polyethylene. In other embodiments, the flame retardant comprises magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material comprises a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A. In certain examples, the reinforcing fibers comprise glass fibers, and the polyolefin comprises polypropylene. In other examples, the composite further comprises a first skin disposed on a first surface of the porous core. In certain examples, the blended material does not include a phenolic antioxidant. In other examples, the composite includes a non-phenolic antioxidant in the porous core.

[0015] In another embodiment, a thermoplastic composite article includes a porous core including a first thermoplastic material including reinforcing fibers, a blended material, and an antioxidant, the blended material including a metal hydroxide flame retardant and a second thermoplastic material, the blended material not including a phenolic antioxidant, and the porous core includes a web formed from reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material.

[0016] In certain embodiments, the first thermoplastic material and the second thermoplastic material each include a polyolefin. In other embodiments, the reinforcing fibers include glass fibers. In some examples, the metal hydroxide flame retardant includes magnesium hydroxide, aluminum hydroxide, or both. In other examples, the antioxidant present in the first thermoplastic material includes a phenolic antioxidant, the first thermoplastic material and the second thermoplastic material each include polypropylene, the reinforcing fibers include glass fibers, and the metal hydroxide flame retardant includes magnesium hydroxide. In some embodiments, the phenolic antioxidant turns pink upon exposure to an oxidizing agent. In certain embodiments, the antioxidant present in the first thermoplastic material includes a phenolic antioxidant, the first thermoplastic material and the second thermoplastic material each include polypropylene, the reinforcing fibers include glass fibers, and the metal hydroxide flame retardant includes aluminum hydroxide. In certain examples, the phenolic antioxidant turns pink upon exposure to an oxidizing agent. In some embodiments, the article includes a first skin disposed on a first surface of the porous core and an optional second skin disposed on a second surface of the porous core. In some examples, the article includes an antioxidant or an additive that reacts with an oxidant to prevent color change of the porous core.

[0017] In another embodiment, a thermoplastic composite article includes a porous core including a first thermoplastic material including reinforcing fibers, a polyolefin and an antioxidant, and a blended material including a flame retardant and a second thermoplastic material, the blended material being substantially free of the antioxidant that changes color upon exposure to an oxidizing agent, the porous core including a web formed from reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, and the porous core meets the specifications of ASTM E84, Class A.

[0018] In an additional aspect, a thermoplastic composite article includes a porous core including a first thermoplastic material including reinforcing fibers, a polyolefin and an antioxidant, and a blended material including a flame retardant and a second thermoplastic material, wherein the blended material is substantially free of the antioxidant that changes color upon exposure to an oxidizing agent, and wherein the porous core includes a web formed from reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, and wherein the porous core includes a sound absorption coefficient of at least 0.25, or at least 0.4, or at least 0.5 when tested by ASTM C423-17.

[0019] In another embodiment, a thermoplastic composite article includes a porous core including a first thermoplastic material including reinforcing fibers, a polyolefin and an antioxidant, and a blended material including a flame retardant and a second thermoplastic material, the blended material being substantially free of the antioxidant that changes color upon exposure to an oxidizing agent, the porous core including a web formed from the reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, the porous core including a sound absorption coefficient of at least 0.25, or at least 0.4, or at least 0.5 when tested by ASTM C423-17 and meeting the specifications of ASTM E84, Class A.

[0020] In an additional aspect, a thermoplastic composite article includes a porous core including a first thermoplastic material including reinforcing fibers, a polyolefin, and an antioxidant, and a blended material including a flame retardant and a second thermoplastic material, wherein the blended material is substantially free of the antioxidant that changes color upon exposure to an oxidizing agent, the porous core includes a web formed from the reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, and the porous core includes a sound absorption coefficient of at least 0.25, or at least 0.4, or at least 0.5 when tested by ASTM C423-17, and meets the specifications of ASTM E84, Class A, providing a substantially constant color change value (Delta E) when tested for 72 hours using Test Method AATCC 23 dated 2015.

[0021] In another aspect, a method of preventing color change of a flame retardant thermoplastic fiber reinforced porous core upon exposure to an environment comprising an oxidizing agent includes producing a flame retardant thermoplastic fiber reinforced porous core by combining reinforcing fibers, a flame retardant, and a thermoplastic material to form a web comprising reinforcing fibers held in place by a thermoplastic material, the thermoplastic material being substantially free of antioxidants that switch from a first color to a second color upon exposure to an environment comprising an oxidizing agent.

[0022] In certain embodiments, the thermoplastic material is substantially free of phenolic antioxidants. In other embodiments, the thermoplastic material consists essentially of a polyolefin. In some examples, the polyolefin is polypropylene or polyethylene. In other embodiments, the thermoplastic material consists essentially of a polyolefin. In some examples, the polyolefin is polypropylene or polyethylene. In other examples, the flame retardant thermoplastic fiber reinforced porous core layer is stored in an environment containing an oxidizing agent for at least 24 hours without switching from a first color to a second color. In some examples, the thermoplastic material includes a polyolefin. In other examples, the reinforcing fibers include glass fibers and the polyolefin includes polypropylene. In some configurations, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0023] In another aspect, a method of reducing color change in a flame retardant thermoplastic fiber reinforced porous core includes producing a flame retardant thermoplastic fiber reinforced porous core by combining reinforcing fibers, a flame retardant, and a thermoplastic material to form a web including reinforcing fibers held in place by the thermoplastic material, the thermoplastic material including an antioxidant that changes from a first color to a second color upon exposure to an environment including an oxidizer present at a first concentration, the antioxidant changing from the second color back to the first color upon exposure to an environment including an oxidizer present at a second concentration less than the first concentration, and the flame retardant thermoplastic fiber reinforced porous core is stored in an environment including an oxidizer present at or less than the second concentration to maintain the flame retardant thermoplastic fiber reinforced porous core at the first color.

[0024] In certain embodiments, the antioxidant comprises a phenolic antioxidant. In other embodiments, the thermoplastic material consists essentially of a polyolefin. In some examples, the polyolefin is polypropylene or polyethylene. In additional examples, the thermoplastic material consists essentially of a polyolefin. In some examples, the polyolefin is polypropylene or polyethylene. In certain embodiments, the method comprises storing the flame-retardant thermoplastic fiber reinforced porous core layer in an environment comprising an oxidizer present at a first concentration for at least 24 hours, whereby the antioxidant changes from a first color to a second color. In some embodiments, the method comprises removing the flame-retardant thermoplastic fiber reinforced porous core layer from the environment comprising an oxidizer present at a first concentration, and storing the flame-retardant thermoplastic fiber reinforced porous core layer in an environment comprising an oxidizer at or below a second concentration, whereby the antioxidant changes from the second color to the first color. In some cases, the thermoplastic material comprises polypropylene and the reinforcing fibers comprise glass fibers. In another example, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the ASTM E84, Class A specifications.

[0025] In an additional aspect, a method of preventing a color change in a flame retardant thermoplastic fiber reinforced porous core that includes an antioxidant is described. In some embodiments, the method includes shielding the flame retardant thermoplastic fiber reinforced porous core from exposure to an oxidizing agent in an environment surrounding the flame retardant thermoplastic fiber reinforced porous core to prevent the antioxidant from changing from a first color to a second color upon exposure to an environment that includes the oxidizing agent.

[0026] In certain examples, the shielding includes encasing the flame retardant thermoplastic fiber reinforced porous core with a material to prevent the oxidant from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core. In other examples, the shielding includes enclosing the flame retardant thermoplastic fiber reinforced porous core in a substantially airtight container to prevent the oxidant from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core. In some embodiments, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a thermoplastic material, the porous core includes a coating on a first surface to prevent the oxidant from diffusing into the porous core. In certain embodiments, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a thermoplastic material, the porous core is sealed on each surface to prevent the oxidant from diffusing into the porous core. In other embodiments, the thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core includes a polyolefin. In some examples, the polyolefin includes polypropylene. In certain embodiments, the antioxidant is a phenolic antioxidant. In other embodiments, the reinforcing fibers of the thermoplastic fiber reinforced porous core include glass fibers. In some examples, the flame retardant thermoplastic fiber reinforced porous core includes magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0027] In another embodiment, a method of altering the color of a flame retardant thermoplastic fiber reinforced porous core includes forming a flame retardant thermoplastic fiber reinforced porous core by combining reinforcing fibers, a flame retardant, and a thermoplastic material to form a web, and exposing the formed web to an environment containing an oxidizing agent to change the color of the antioxidant in the flame retardant thermoplastic fiber reinforced porous core layer from a first color to a second color.

[0028] In certain embodiments, the web is exposed to an environment containing an oxidizing agent prior to compressing the web. In some embodiments, the web is exposed to an environment containing an oxidizing agent after compressing the web. In certain examples, the web is exposed to an environment containing greater than 2 ppm of an oxidizing agent prior to placing a skin on the web. In other examples, the web is exposed to an environment containing greater than 2 ppm of an oxidizing agent after placing a porous skin on the web. In additional examples, the thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core comprises a polyolefin. In some embodiments, the polyolefin comprises polypropylene. In certain embodiments, the antioxidant is a phenolic antioxidant. In other embodiments, the reinforcing fibers of the thermoplastic fiber reinforced porous core comprise glass fibers. In some cases, the flame retardant comprises magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0029] In an additional aspect, a thermoplastic composite article includes a porous core including reinforcing fibers, a flame retardant material, and a thermoplastic material, the porous core including a web formed from the reinforcing fibers held in place by the thermoplastic material, the thermoplastic material being substantially free of an antioxidant that turns pink upon exposure to an oxidizing agent.

[0030] In certain examples, the thermoplastic material consists essentially of a polyolefin, e.g., polypropylene or polyethylene. In some examples, the thermoplastic material consists essentially of a polyolefin, e.g., polypropylene or polyethylene. In some embodiments, the flame retardant comprises magnesium hydroxide, aluminum hydroxide, or both, and the porous core meets ASTM E84, Class A specifications. In other embodiments, the reinforcing fibers comprise glass fibers, and the polyolefin comprises polypropylene. In other embodiments, the composite further comprises a first skin disposed on a first surface of the porous core. In some embodiments, the porous core layer does not comprise a phenolic antioxidant. In other examples, the composite comprises a non-phenolic antioxidant in the porous core.

[0031] In another aspect, a thermoplastic composite article includes a porous core including reinforcing fibers and a thermoplastic material, the porous core further including a metal hydroxide flame retardant and an antioxidant, the porous core including a web formed from the reinforcing fibers held in place by the thermoplastic material, and the antioxidant in the porous core including the metal hydroxide flame retardant changes color from a first color to a second color upon exposure to an oxidizing agent and changes color from the second color to the first color upon removal of the oxidizing agent.

[0032] In certain embodiments, the thermoplastic material includes a polyolefin. In some examples, the reinforcing fibers include glass fibers. In other examples, the metal hydroxide flame retardant includes magnesium hydroxide, aluminum hydroxide, or both. In some cases, the antioxidant includes a phenolic antioxidant, the thermoplastic material includes polypropylene, the reinforcing fibers include glass fibers, and the metal hydroxide flame retardant includes magnesium hydroxide. In some examples, the phenolic antioxidant turns pink upon exposure to an oxidizing agent. In other examples, the antioxidant includes a phenolic antioxidant, the thermoplastic material includes polypropylene, the reinforcing fibers include glass fibers, and the metal hydroxide flame retardant includes aluminum hydroxide. In some examples, the phenolic antioxidant turns pink upon exposure to an oxidizing agent. In other examples, the article includes a first skin disposed on a first surface of the porous core and an optional second skin disposed on a second surface of the porous core. In some examples, the article includes an additive that reacts with the antioxidant to prevent the formation of a pink color.

[0033] In another embodiment, a thermoplastic composite article includes a porous core including reinforcing fibers, a flame retardant material, and a thermoplastic material, the porous core including a web formed from the reinforcing fibers held in place by the thermoplastic material, the thermoplastic material being substantially free of antioxidants that turn pink upon exposure to an oxidizing agent, and the porous core meeting the specifications of ASTM E84, Class A.

[0034] In another embodiment, a thermoplastic composite article includes a porous core including reinforcing fibers, a flame retardant material, and a thermoplastic material, wherein the porous core includes a web formed from the reinforcing fibers held in place by the thermoplastic material, wherein the thermoplastic material is substantially free of antioxidants that turn pink upon exposure to an oxidizing agent, and wherein the porous core includes a sound absorption coefficient of at least 0.25, or at least 0.4, or at least 0.5, when tested by ASTM C423-17.

[0035] In another aspect, a thermoplastic composite article includes a porous core including reinforcing fibers, a flame retardant material, and a thermoplastic material, wherein the porous core includes a web formed from the reinforcing fibers held in place by the thermoplastic material, wherein the thermoplastic material is substantially free of antioxidants that turn pink upon exposure to an oxidizing agent, wherein the porous core meets the specifications of ASTM E84, Class A, and wherein the porous core includes a sound absorption coefficient of at least 0.25, or at least 0.4, or at least 0.5 when tested by ASTM C423-17.

[0036] In an additional aspect, a thermoplastic composite article includes a porous core including reinforcing fibers, a flame retardant material, and a thermoplastic material, wherein the porous core includes a web formed from the reinforcing fibers held in place by the thermoplastic material, wherein the thermoplastic material is substantially free of antioxidants that turn pink upon exposure to an oxidizing agent, and wherein the porous core includes a sound absorption coefficient of at least 0.25, or at least 0.4, or at least 0.5 when tested by ASTM C423-17, and meets the specifications of ASTM E84, Class A, providing a substantially constant color change value (Delta E) when tested for 72 hours using Test Method AATCC 23 dated 2015.

[0037] Additional aspects, embodiments, examples, configurations, and features are described in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS With reference to the accompanying figures, certain specific configurations of the composite articles and methods are described. [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 illustrates a reaction in which an oxidizing agent may react with a phenolic antioxidant, according to some embodiments. [Figure 2A] FIG. 2A is an illustration of a composite article including a core layer, in accordance with certain examples. [Figure 2B] FIG. 2B is an illustration of a composite article including a core layer and a skin, according to certain examples. [Figure 2C]FIG. 2C is an illustration of a composite article including a core layer and a skin on each surface of the core layer, according to certain examples. [Figure 2D] FIG. 2D is an illustration of a composite article including a core layer, a skin, and a decorative layer over the skin, according to certain examples. [Figure 2E] FIG. 2E is an illustration of a composite article including a core layer, a skin on each surface of the core layer, and a decorative layer on each of the skins, according to a particular example. [Diagram 3] FIG. 3 is an illustration of two core layers joined together according to some embodiments. [Figure 4] FIG. 4 is an illustration of a composite article that is sealed to protect the underlying core layer from exposure to oxidizing agents, according to some examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] It will be recognized by those of ordinary skill in the art, given the benefit of this disclosure, that the layers and other features shown in the figures are not necessarily drawn to scale, and no particular thickness, dimension, or order is intended to be implied unless it is clear from the description of that particular figure or embodiment.

[0040] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Several example configurations of composite articles that can be configured to resist discoloration (or promote the formation of a particular color) are described. Although various layers are shown in the figures and described below, the thicknesses, sizes, and geometries of the different layers need not be the same and may be thicknesses, sizes, and geometries other than those shown in the figures. Additionally, the exact arrangement or layering of components may be altered, or intermediate layers (e.g., adhesive layers) may be present between the exemplary layers shown in the figures.

[0041] In certain embodiments, the reinforcing material, first thermoplastic material, and mixed flame retardant material of the articles described herein are generally present in a prepreg or core layer. The prepreg may be a core layer that is not fully formed, or may include materials that are processed to form the final core layer. For example, the prepreg may include a thermoplastic material in combination with reinforcing fibers and a mixed flame retardant material, but may not be fully formed, or may be present in a softened state by applying heat. The prepreg may be pressed, compressed, or molded into a desired shape to provide the core layer. Other layers connected to the prepreg layer may be added before or after the core is fully formed. The other layers may be connected to the prepreg or core layer using an adhesive, or in some cases, the prepreg or core layer may be directly connected to the other layers without using an adhesive material between the prepreg or core layer and the other layers.

[0042] In certain examples, the prepreg or core layer can be used in lightweight reinforced thermoplastic (LWRT) articles. LWRT can provide certain desirable attributes, including, but not limited to, high stiffness-to-weight ratio, low part weight, simple and low-cost part forming process, low coefficient of thermal expansion, recyclability, etc. LWRT articles have a wide range of applications in the automotive industry, including various types of soft trim for both interior and exterior applications. Recreational vehicles, commercial truck trailers, and similar applications represent another category of wide applications for LWRT articles. Ceiling tiles, office panels, cubicle panels, and the building and construction industry may also use the LWRT articles described herein.

[0043] Certain composite articles including a first thermoplastic material, a mixed flame retardant, and a reinforcing material are described herein. As discussed in more detail below, one or more additives that may be present in the mixed flame retardant, the thermoplastic material, or the reinforcing material may promote discoloration or some degree of color change in the core layer. For example, there may be a material that can induce a color change (e.g., from white to pink, white to yellow, or white to another color) under certain conditions, such as in the presence of an oxidizing agent or oxidizing material that may cause the composite article to change color. By omitting a material that reacts with an oxidizing agent, a selected color of the composite article can be maintained. Alternatively, the presence of a material that can induce a color change in the composite article can be advantageously utilized to promote a color change under certain environmental conditions. In addition, the composite article may be subjected to selected environmental conditions to avoid or promote discoloration as desired. In some cases, an antioxidant may be omitted from the mixed flame retardant material but still be present in the core layer, for example, the first thermoplastic material may include an antioxidant. For example, as discussed in more detail below, when certain flame retardants are present, conditions may promote a color change in the mixed flame retardant material. In some cases, by using a mixed flame retardant material that does not contain a phenolic antioxidant, the antioxidant may still be present in the final core layer without causing a color change.

[0044] In certain embodiments, a blended flame retardant material typically includes a flame retardant material blended with another material (e.g., a second thermoplastic material). In existing blended flame retardant materials, the overall composition of the blended flame retardant material also typically includes an antioxidant (AO) to prevent oxidation of the thermoplastic material during and / or after the blending process. The AO may react with an oxidizing agent, such as ozone, oxygen, air, nitrogen oxides, etc., to provide a pink or yellow compound, which may impart an overall undesirable color to the core layer. One illustrative example of the reaction is shown in FIG. 1, where a phenolic AO reactant (labeled 100 for reference) reacts with NO XIt is shown to react with compounds (nitric oxide, nitrogen dioxide or other nitrogen oxides) to produce a pink or yellow product (labeled 110 for reference) depending on the particular phenolic AO present. The "R" groups shown in FIG. 1 are typically hydrocarbon groups containing from 1 up to about 8 carbon atoms, although non-carbon groups such as nitrogen, oxygen, and hydroxyl groups may also be present. The reaction is reversible and may depend, at least in part, on humidity, heat, UV light, and other factors. In some instances, the phenolic methides (e.g., quinone methides) produced can be reacted in the reverse direction by exposing them to sunlight / UV or changing humidity conditions, or both. For example, it is possible to convert the product 110 back to reactant 100 by subjecting the product 110 to suitable environmental conditions. In other cases, the presence of alkaline flame retardants such as aluminum hydroxide (ATH) or magnesium hydroxide (MDH), or other metal hydroxides, may promote the formation of the phenolic methide product and enhance the pink or yellow coloration. An alkaline environment may disfavor the reverse reaction of product 110 to reactant 100 by shifting the equilibrium in favor of the formation of product 110.

[0045] In the specific examples described herein, the exact material used as the blended flame retardant material may vary depending on the desired overall properties of the prepreg or core and / or the method used to manufacture the prepreg or core. Blended flame retardant materials typically include a flame retardant agent or material blended with another material (e.g., a polymeric material). For example, a blended flame retardant material may include a flame retardant agent blended with one or more thermoplastic or thermosetting materials. In some cases, the thermoplastic or thermosetting materials are free or substantially free of antioxidants that may cause color changes in the core layer upon exposure to one or more of air, oxidizing agents, high humidity, e.g., relative humidity greater than 50%, UV exposure, or other environmental conditions. When the prepreg or core includes a thermoplastic material in combination with reinforcing fibers, one of the materials present in the blended flame retardant material may also be a thermoplastic material. The virgin thermoplastic material in the prepreg or core may be the same as or different from the thermoplastic material present in the blended flame retardant material. In some cases where a thermoplastic material is present in the blended flame retardant material, the thermoplastic material of the blended flame retardant material may include one or more of polyethylene, polypropylene, polystyrene, acrylonitrile styrene, butadiene, polyethylene terephthalate, polybutylene terephthalate, polybutylene tetrachlorate, and polyvinyl chloride, both plasticized and unplasticized, and may include blends of these materials with each other or with other polymeric materials.Other suitable thermoplastic materials for use in the blended flame retardant material include, but are not limited to, polyarylene ethers, polycarbonates, polyester carbonates, thermoplastic polyesters, polyimides, polyetherimides, polyamides, acrylonitrile-butyl acrylate-styrene polymers, amorphous nylons, polyarylene ether ketones, polyphenylene sulfides, polyarylsulfones, polyethersulfones, liquid crystal polymers, the commercial poly(1,4 phenylene) compound known as PARMAX®, high temperature polycarbonates such as Bayer's APEC® PC, high temperature nylons, and silicones, as well as alloys and blends of these materials with each other or with other polymeric materials. Blended flame retardant materials that include a thermoplastic material blended with a flame retardant material are referred to herein as blended flame retardant thermoplastic materials in certain cases.

[0046] In certain embodiments, the flame retardant agents used in the mixed flame retardant material may include many different materials, including organic and inorganic flame retardant materials. In some cases, these flame retardant materials do not change color upon exposure to certain environmental conditions or materials, such as oxidizing agents. In certain configurations, the flame retardant agents of the mixed flame retardant material may include inorganic materials or inorganic salts. For example, due to restrictions on hazardous substances (RoHS), it may be desirable to select the flame retardant material as an inorganic salt that is substantially free (or free) of any halides. In some embodiments, the flame retardant material may include a Group II metal or a Group III metal in combination with one or more anions. For example, the flame retardant agents of the mixed flame retardant material may include beryllium, calcium, magnesium, or other Group II metal salts. In some embodiments, the Group II metals of the mixed flame retardant material may be present as hydroxide materials. For example, the flame retardant material may be present as beryllium hydroxide, calcium hydroxide, magnesium hydroxide, or other Group II metal hydroxides. In other cases, the flame retardant agent of the mixed flame retardant material may include aluminum, gallium, indium, or other Group III metal salts. In some embodiments, the Group III metal of the mixed flame retardant material may be present as a hydroxide material. For example, the flame retardant material may be present as aluminum hydroxide or gallium hydroxide, or other Group III metal hydroxide.

[0047] In other configurations, the inorganic material present as the flame retardant material may include one or more transition metal salts that may function as a flame retardant material. For example, a transition metal capable of forming a divalent cation in solution may be combined with one or more anions and used as a flame retardant agent. In some cases, the transition metal salt may be present in a non-halide form, e.g., not as a fluoride, chloride, bromide, or iodide salt, to avoid the release of toxic gases if the prepreg or core burns. In certain configurations, the transition metal salt may be present, for example, as a hydroxide.

[0048] In certain embodiments, the exact amount of the mixed flame retardant material used in the prepreg or core may vary depending on which other materials are present, but the mixed flame retardant material is typically present in a weight percent less than the major amount of the prepreg or core, for example, the mixed flame retardant material is typically present at 50% or less by weight based on the weight of the prepreg or core. In certain cases, the mixed flame retardant material is present in more than the minimum amount to provide flame retardancy to the prepreg or core. For example, the mixed flame retardant material may be present at 30% or more by weight, 35% or more by weight, 40% or more by weight, or even 45% or more by weight based on the weight of the prepreg or core. Exemplary mixed flame retardant materials are commercially available from many different suppliers. For example, a flame retardant material (e.g., a Group II metal hydroxide) can be mixed with another material (e.g., a thermoplastic material) using an extrusion process. In some cases, the thermoplastic material is added to an extruder and melted. As shown herein, it may be desirable for the molten thermoplastic material of the blended flame retardant material to be free of phenolic antioxidants that may change color upon exposure to an oxidizing agent. The molten polymer may be extruded or jetted into a barrel where the flame retardant material is then added. The resulting mixture is jetted forward, acting to mix the flame retardant material into the molten thermoplastic material that does not contain phenolic AOs that may change color. The resulting mixture may then be cooled to form a solid material such as particles, fibers, or pellets. In the absence of AOs in the blended flame retardant material, it may be desirable to store the blended flame retardant material under inert conditions to avoid oxidation of the thermoplastic material, for example, under vacuum, or other conditions under which the blended flame retardant material is not exposed to air, UV, or other external factors that may cause degradation of the polymeric components of the blended flame retardant material. In some examples, the blended flame retardant material may include a Group II or Group III metal salt mixed with a polyolefin (e.g., polyethylene, polypropylene, etc.).For example, a Group II metal hydroxide or a Group III metal hydroxide can be mixed with polyethylene, polypropylene or copolymers thereof, for example, MDH or ATH can be mixed with polypropylene or polyethylene.

[0049] In certain embodiments, the specific ratio of the flame retardant material to the thermoplastic material in the mixed flame retardant material can vary. For example, the flame retardant material:thermoplastic material ratio in the mixed flame retardant material can vary from 1:1, 2:1, 3:1, 4:1:5:1, 1:5, 1:4, 1:3, or 1:2. In the case where the mixed flame retardant material includes an inorganic flame retardant salt in combination with a second thermoplastic material, the inorganic salt is typically present in a higher amount in the mixed flame retardant material. For example, the inorganic salt:thermoplastic material ratio can be about 2:1, 3:1, 3:2, 5:2, 7:2, 4:3, 5:3, 7:3, 8:3, 5:4, 7:4, 9:4, 11:4, 6:5, 7:5, 8:5, 9:5, 11:5, 13:5, or other ratios. However, if desired, the second thermoplastic material may be present in the mixed flame retardant material in an equal amount / weight, or in the mixed flame retardant material in a greater amount / weight than the flame retardant material.

[0050] Depending on the particular process used to manufacture the prepreg or core, the mixed flame retardant material may be polished, filtered, sized, or otherwise processed prior to addition to the other materials in the prepreg or core. In some cases where a first thermoplastic particle is used in the prepreg or core, the average particle size of the mixed flame retardant material may be about the same as the average particle size of the first thermoplastic material. In other configurations, the average particle size of the mixed flame retardant material may be smaller or larger than the average particle size of the first thermoplastic material used in the prepreg or core.

[0051] In certain embodiments, the first thermoplastic material of the core layer may be used in the prepreg or core in fiber form, particle form, resin form, or other suitable form. In some examples, the first thermoplastic material may include a polyolefin or other thermoplastic material. For example, the first thermoplastic material may include one or more of polyethylene, polypropylene, polystyrene, acrylonitrile styrene, butadiene, polyethylene terephthalate, polybutylene terephthalate, polybutylene tetrachlorate, and polyvinyl chloride, both plasticized and unplasticized, and may include blends of these materials with each other or with other polymeric materials. Other suitable thermoplastics include, but are not limited to, polyarylene ethers, polycarbonates, polyester carbonates, thermoplastic polyesters, polyimides, polyetherimides, polyamides, acrylonitrile-butyl acrylate-styrene polymers, amorphous nylons, polyarylene ether ketones, polyphenylene sulfides, polyarylsulfones, polyethersulfones, liquid crystal polymers, the commercial poly(1,4 phenylene) compound known as PARMAX®, high temperature polycarbonates such as Bayer's APEC® PC, high temperature nylons, and silicones, as well as alloys and blends of these materials with each other or with other polymeric materials. In certain configurations, the thermoplastic material of the core layer (e.g., the first thermoplastic material) may optionally contain an antioxidant, if desired. By separating the antioxidant from any basic flame retardant material present in the mixed flame retardant material, discoloration can be reduced or avoided in the final formed core layer. In other cases, the first thermoplastic material may be free or substantially free of antioxidant materials that change color upon exposure to an oxidizing agent. Exemplary thermoplastic materials in various forms are described herein and in U.S. Publication No. 20130244528 and U.S. Publication No. US20120065283.The exact amount of thermoplastic material present in the prepreg or core can vary, with exemplary amounts ranging from about 10% to about 90% by weight, such as from about 20% to about 80% by weight, or from about 30% to about 70% by weight, or from about 40% to about 60% by weight.

[0052] In certain embodiments, the reinforcing material present in the prepreg or core layer may be present in the form of fibers, particles, whiskers, or other forms. For example, the reinforcing fibers may be present with the thermoplastic material and the flame retardant to form a web of reinforcing fibers that may be held in place by the thermoplastic material. In some examples, the reinforcing fibers may include glass fibers, carbon fibers, graphite fibers, synthetic organic fibers, particularly high modulus organic fibers, such as para-aramid and meta-aramid fibers, nylon fibers, polyester fibers, or any of the high melt flow index resins described herein suitable for use as fibers, natural fibers such as hemp, sisal, jute, flax, coir, kenaf, and cellulose fibers, mineral fibers such as basalt, rock wool (e.g., rock wool or slag wool), wollastonite, alumina, silica, or mixtures thereof, metal fibers, metallized natural and / or synthetic fibers, ceramic fibers, yarn fibers, or mixtures thereof, and the like. In some embodiments, any of the aforementioned fibers may be chemically treated prior to use to provide desired functional groups or impart other physical properties to the fibers, for example, they may be chemically treated to be capable of reacting with the thermoplastic material, the blended flame retardant material, or both. Alternatively, the flame retardant material may be reacted with the thermoplastic material of the prepreg or core to provide a derivatized thermoplastic material, which is then mixed with the fibers. The reinforcing material content in the prepreg or core may be from about 10% to about 90% by weight of the prepreg or core, for example, from about 20% to about 80% by weight, more specifically, from about 30% to about 70% by weight of the prepreg or core, or from about 40% to about 60% by weight of the prepreg or core. Typically, when reinforcing fibers are used, the fiber content of a composite article including the prepreg or core varies from about 20% to about 90% by weight, more specifically, from about 30% to about 80% by weight, for example, from about 40% to about 70% by weight of the composite. The particular size and / or orientation of the fibers used may depend, at least in part, on the polymeric material used and / or the desired properties of the resulting prepreg or core. Suitable additional fiber types, fiber sizes and amounts will be readily selected by the person of ordinary skill in the art, given the benefit of this disclosure.In one non-limiting example, the fibers dispersed in the thermoplastic material to provide the prepreg or core generally have a diameter greater than about 5 microns, more specifically, about 5 microns to about 22 microns, and a length of about 5 mm to about 200 mm, more specifically, the fiber diameter may be about microns to about 22 microns, and the fiber length may be about 5 mm to about 75 mm. In some configurations, the flame retardant material used in the mixed flame retardant material may also be present in fibrous form. For example, the prepreg, core, or composite may include a thermoplastic material, a reinforcing fiber, and a fiber including the mixed flame retardant material. The mixed flame retardant material fiber may include any one or more of the flame retardant materials described herein (e.g., polypropylene fiber mixed with a metal hydroxide material), which is then extruded and cut into fibers using a suitable die and / or other device.

[0053] In some configurations, the prepreg or core may be substantially halogen-free or halogen-free to meet the limits on hazardous materials requirements for a particular application. In other cases, the prepreg or core may contain, for example, a halogenated flame retardant agent (which may be present in the flame retardant material or may be added in addition to the flame retardant material), such as a halogenated flame retardant agent containing one of many of F, Cl, Br, I, and At, or a compound containing such a halogen, such as tetrabromobisphenol-A polycarbonate, or a monohalo-, dihalo-, trihalo-, or tetrahalo-polycarbonate. In some cases, the thermoplastic material used in the prepreg and core may contain one or more halogens to impart some degree of flame retardancy without the addition of another flame retardant agent. For example, the thermoplastic material of the mixed flame retardant material may be halogenated in addition to being mixed with the flame retardant material, or the virgin thermoplastic material may be halogenated. When a halogenated flame retardant is present, the flame retardant is desirably present in a flame retardant amount, which may vary depending on other components present. For example, the halogenated flame retardant, when present in addition to a mixed flame retardant material, may be present at about 0.1% to about 15% by weight (based on the weight of the prepreg or core), more particularly, about 1% to about 13% by weight, such as about 5% to about 13% by weight. If desired, two different halogenated flame retardants may be added to the prepreg or core. In other cases, a non-halogenated flame retardant may be added, such as a flame retardant agent containing one or more of N, P, As, Sb, Bi, S, Se, and Te. In some embodiments, the non-halogenated flame retardant may include a phosphorylated material, such that the prepreg may be more environmentally friendly. When a non-halogenated or substantially halogen-free flame retardant is present, the flame retardant is desirably present in a flame retardant amount, which may vary depending on other components present.For example, the substantially halogen-free flame retardant may be present at about 0.1% to about 15% by weight (based on the weight of the prepreg or core), more specifically, about 1% to about 13% by weight, e.g., about 5% to about 13% by weight, based on the weight of the prepreg or core. If desired, two different substantially halogen-free flame retardants may be added to the prepreg or core. In certain cases, the prepregs or cores described herein may include one or more halogenated flame retardants in combination with one or more substantially halogen-free flame retardants. When two different flame retardants are present, the combination of the two flame retardants is present in a flame retardant amount, which may vary depending on other components present. For example, the total weight of the flame retardants present (excluding any mixed flame retardant materials) may be about 0.1% to about 20% by weight (based on the weight of the prepreg or core), more specifically, about 1% to about 15% by weight, e.g., about 2% to about 14% by weight, based on the weight of the prepreg or core. The flame retardant agents used in the prepregs or cores described herein can be added to the mixture containing the thermoplastic material and fibers (before the mixture is disposed of on a wire screen or other processing component) or can be added after the prepregs or cores are formed.

[0054] In certain embodiments, the prepregs or cores described herein generally contain a significant amount of open cell structure such that voids are present in the prepreg. For example, the prepregs or cores may contain 0-30%, 10-40%, 20-50%, 30-60%, 40-70%, 50-80%, 60-90%, 0-40%, 0-50%, 0-60%, 0-70%, 0-80%, 0-90%, 10-50%, 10-60%, 10-70%, 10-80%, 10-90%, 10-95%, 20-60%, 20-70%, 20-80% , 20-90%, 20-95%, 30-70%, 30-80%, 30-90%, 30-95%, 40-80%, 40-90%, 40-95%, 50-90%, 50-95%, 60-95%, 70-80%, 70-90%, 70-95%, 80-90%, 80-95%, or any exemplary value within these exemplary ranges. In some cases, the prepreg or core comprises a porosity or void content of greater than 0% (e.g., not fully integrated) up to about 95%. Unless otherwise noted, references to a prepreg or core comprising a particular void content or porosity are based on the total volume of the prepreg or core, and not necessarily based on the total volume of the prepreg or core plus any other materials or layers coupled to the prepreg or core.

[0055] 2A, a composite article 200 is shown that includes a core layer 210. The core layer 210 includes a first thermoplastic material, a reinforcing material, and a blended flame retardant material that typically includes a flame retardant material blended with a second thermoplastic material. The materials combine to form an open cell structure web such that the core layer 210 is highly porous. This high porosity reduces the overall weight of the core layer 210, but allows oxidizing agents to penetrate the core, potentially allowing discoloration of the core layer 210. In some configurations, discoloration or color change can be avoided by constructing the core layer 210 without the presence of antioxidants in the blended flame retardant material. In other cases, the entire core layer 210 may be free or substantially free of antioxidants. Although not required, the flame retardant material present in the blended flame retardant material may be dispersed throughout the prepreg or core 210. For example, the core 210 includes a flame retardant material dispersed substantially throughout the prepreg or core 210. In some cases, the dispersion of the flame retardant material may be substantially homogenous or substantially uniform from the first surface to the second surface of the prepreg or core 210. To achieve such a substantially homogenous or substantially uniform distribution of the flame retardant material in the prepreg or core 210, as described in more detail herein, the components of the core may be mixed together to form a dispersion prior to forming the prepreg or core. Mixing may be performed until the dispersion includes a substantially homogenous or substantially uniform mixture of the flame retardant material, thermoplastic material, and fibers in the dispersion. The prepreg or core may then be formed by, for example, placing the dispersion on a wire screen using a suitable layering process, as described herein, and then compressing and / or curing the thermoplastic material of the prepreg to provide the core. In other configurations, it may be desirable to provide a gradient distribution of the flame retardant material from one surface of the prepreg or core to the other surface of the prepreg or core. In some configurations, a substantially uniform distribution of flame retardant material is present in the prepreg or core, and then additional flame retardant material is added to one side of the prepreg or core to provide a gradient distribution.Such additional flame retardant materials can be added directly to the prepreg or core, for example, by spraying or coating, or by using a solution containing the flame retardant material, or by connecting a skin, additional prepreg or core, or other component containing the flame retardant material to the prepreg or core. For example, a first prepreg or core and a second prepreg or core disposed on the first prepreg or core to provide a composite article. Each of the prepregs or cores may contain a substantially uniform distribution of the flame retardant material, but the amount and / or type of the flame retardant material in the two prepregs or cores may be different, for example, the incorporation rate may be different, or the flame retardant material itself may be different. However, if desired, only one of the prepregs or cores may contain the flame retardant material, and the other prepreg or core may contain no material other than the thermoplastic material and the reinforcing fiber. The thermoplastic material of the prepreg or core can be melted to provide a single combined prepreg or core containing material from the two prepregs or cores. The result of melting the prepregs or cores is a composite core with a gradient distribution of flame retardant material. In other configurations, the distribution of flame retardant material in the prepreg or core can be provided by connecting a skin or other material containing the flame retardant material to the prepreg or core. In other cases, the skin can be melted within the prepreg or core, connecting the skin and the prepreg or core, leaving a connected skin / core composite without any substantial interface. If desired, and as described in more detail below, an additional skin, which may or may not contain flame retardant material, can also be connected to the prepreg or core on the opposite side from the first skin.

[0056] In other cases, the core layer 210 may include an antioxidant, but the antioxidant is not present in the blended flame retardant material. For example, the first thermoplastic material of the core layer 210 may include an antioxidant, or the reinforcing material of the core layer 210 may include an antioxidant, but the blended flame retardant material may be free or substantially free of antioxidants to avoid or reduce the possibility of color change. Alternatively, a separate antioxidant may be added to the core layer during or after formation, if desired.

[0057] In other embodiments, the composite article may also include one or more skins disposed on the surface of the prepreg or core layer. For example, referring to Figures 2B and 2C, a first skin 220 is shown disposed on a first surface of the core 210 (see Figure 2B), and an optional second skin 230 may be disposed on a second surface of the core 210 (see Figure 2C). The skins 220, 230 may be the same or different. For example, the skins 220, 230 may independently include an open cell structure or a closed cell structure. In certain configurations, each of the skins 220, 230 may independently include, for example, a film (e.g., a thermoplastic or elastomeric film), a flim, a scrim (e.g., a fiber-based scrim), a foil, a woven fabric, a nonwoven fabric, or may be present as an inorganic coating, an organic coating, or a thermoset coating disposed on the prepreg or core 210. In other cases, each of the skins 220, 230, independently, may include a limiting oxygen index, as measured according to ISO 4589 dated 1996, of greater than about 22. When a thermoplastic film is present as (or as part of) one or both of the skins 220, 230, the thermoplastic film may include at least one of poly(etherimide), poly(etherketone), poly(ether-etherketone), poly(phenylene sulfide), poly(arylene sulfone), poly(ether sulfone), poly(amide-imide), poly(1,4-phenylene), polycarbonate, nylon, and silicone. When a fiber-based scrim is present as (or as part of) one or both of the skins 220, 230, the fiber-based scrim may include at least one of glass fibers, aramid fibers, graphite fibers, carbon fibers, inorganic mineral fibers, metal fibers, metallized synthetic fibers, and metallized inorganic fibers. When a thermoset coating is present as (or as part of) one or both of the skins 220, 230, the coating may include at least one of an unsaturated polyurethane, a vinyl ester, a phenolic resin, and an epoxy.When an inorganic coating is present as (or as part of) one or both of the skins 220, 230, the inorganic coating may include minerals containing cations selected from Ca, Mg, Ba, Si, Zn, Ti, and Al, or may include at least one of gypsum, calcium carbonate, and mortar. When a nonwoven is present as (or as part of) one or both of the skins 220, 230, the nonwoven may include thermoplastic materials, thermosetting binders, inorganic fibers, metal fibers, metallized inorganic fibers, and metallized synthetic fibers. If desired, one or both of the skins 220, 230 may include expandable graphite materials and / or mixed flame retardant materials.

[0058] In certain configurations, the composite article may also include one or more decorative layers disposed on one of the skins. FIG. 2D shows a first decorative layer 240 disposed on the skin 220, and FIG. 2E shows a second decorative layer 250 disposed on the skin 250. Although not shown, a decorative layer may be disposed directly on the core 210, opposite the surface on which the skin 220 is disposed in FIG. 2A. The decorative layers 240, 250 may independently be thermoplastic films, such as polyvinyl chloride, polyolefins, thermoplastic polyesters, thermoplastic elastomers, and the like. The decorative layers 240, 250 may independently be multi-layered structures including a foam core formed, for example, from polypropylene, polyethylene, polyvinyl chloride, polyurethane, and the like. The fabric may be bonded to the foam core, for example, woven fabrics made from natural and synthetic fibers, organic fiber nonwoven fabrics after needle punching, etc., raised fabrics, knitted products, flock fabrics, or other such materials. The fabric may also be bonded to the foam core with thermoplastic adhesives, including pressure sensitive and hot melt adhesives such as polyamides, modified polyolefins, urethanes, and polyolefins. The facing layers 240, 250 can be independently manufactured using spunbond, thermally bonded, spunlaced, meltblowing, wet laid processes, and / or dry laid processes. In some configurations, the facing layers 240, 250 may independently include an open cell structure or a closed cell structure. The facing layers 240, 250 may be the same or different as desired.

[0059] In some embodiments, two or more prepreg or core layers may be joined together as shown in FIG. 3. Composite article 300 includes a first prepreg or core layer 310 joined to a second prepreg or core layer 320. Layers 310, 320 may be the same or different. In some examples, layer 310 may include a blended flame retardant material that is substantially free of antioxidants, and layer 315 may include a blended flame retardant material with antioxidants present. Discoloration of outer layer 310 may be avoided by placing layer 310 without antioxidants on the outer surface. Even if inner layer 315 discolors, it may be located under layer 310 and generally not cause an overall change in color of article 300. Although not shown, the composite article may include any of the skin and / or cosmetic layer configurations shown in FIGS. 2B-2E, if desired.

[0060] In certain embodiments, the LWRT articles described herein can provide a desired level of flame retardancy and sound absorption or noise reduction. For example, certain articles described herein can meet either FMVSS 302 or SAE J369 test standards. These tests are generally equivalent and are used to determine burn rate measurements. Briefly, the test uses a horizontal flame chamber, a fume hood, a tote large enough to handle a specimen about 12 inches in length, a water source, a timer, a lighter, and a ruler. The specimen size is typically about 4 inches by about 12 inches, and five or more specimens are typically tested. The adhesive side of the specimen is typically subjected to the flame. For FMVSS 302 testing, the fume hood is typically open enough to provide an airflow of about 150 cubic feet per minute. For SAE J369 testing, for example, the fume hood may be open to provide the same airflow or may be open all the time. Unless otherwise noted herein, the FMVSS 302 test may be interchanged with the SAE J369 test. The results of these tests may be classified in several ways, including DNI, SE / 0, SE / NBR, SE / B, B, and RB. DNI refers to materials that do not support combustion during or after the 15 second ignition period and / or do not transmit a flame front across any surface to a selected distance. SE / 0 refers to materials that ignite a surface but the flame itself goes out before traveling to a selected distance. SE / NBR refers to materials that stop burning before burning for 60 seconds from the point of initiation and do not burn more than about 50 mm from the point of initiation. SE / B refers to a flame front that travels a selected distance but goes out before reaching a second distance. B refers to materials that burn the entire distance. RB refers to materials that burn so rapidly that the burn rate cannot be measured. One or more of burn distance, burn time, burn rate, and whether the material is self-extinguishing may also be measured. A specimen may be considered to "meet" or "pass" the FMVSS 302 or SAE J369 test if the flame travels less than about 102 mm / min. A specimen will fail the test if it burns faster than 102 mm / min.

[0061] In some configurations described herein, the presence of a blended flame retardant material in a thermoplastic prepreg or thermoplastic core can provide the prepreg or core with at least some degree of flame retardancy. For example, the prepreg or core (and composite articles including the prepreg or core layer) may meet the Class A standard of ASTM E84, entitled "Standard Test Method for Surface Burning Characteristics of Building Materials," dated 2009. The particular flame retardant material selected for use in the core layer can provide an article that meets the class A or class B requirements of ASTM E84 in the as-manufactured article, e.g., without any molding, or in a molded article, if desired. Class A articles differ from class B articles in that class A articles have a flame spread index (FSI) of about 0-25, while class B articles have a flame spread index of 26-75. In some cases, there is enough intermixed flame retardant material in the final prepreg or core such that the prepreg or core meets Class A standards under ASTM E84 testing dated 2009.

[0062] In certain examples, the LWRT articles described herein may provide sound absorption or noise reduction in addition to being flame retardant. A variety of different sound measurement tests can be performed to evaluate noise reduction, including ASTM C423-17 entitled "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method." For example, a sound absorption average (SAA) value can be measured based on absorption at a set of frequencies. Similar to the SAA, the NRC (Noise Reduction Coefficient) is also based on a set of frequencies. The Sound Absorption Average (SAA) is defined as a single number rating (average) of the sound absorption coefficient of the material for the 12-1 / 3 octave band from 200 to 2500 Hz (inclusive), rounded to the nearest 0.01. The Noise Reduction Coefficient (NRC) is defined from a conventional embodiment of this same test method as the average of the coefficients at 250, 500, 1000, and 2000 Hz, expressed as the nearest integer multiple of 0.05. Specimen mounting methods are also specified for NRC / SAA testing and are set forth in ASTM E795-16 Type E 400 mounting method. In some cases, the composite articles described herein may be flame retardant (e.g., meet E84, Class A specifications) and may include a sound absorption coefficient of at least 0.25, or at least 0.4, or at least 0.5, when tested by ASTM C423-17.

[0063] In certain configurations of the articles described herein where antioxidants are not present in the blended flame retardant material, the articles may provide both flame retardancy and noise reduction. Those of skill in the art, given the benefit of this disclosure, will recognize that the exact level of flame retardancy and noise reduction may depend on the materials used in the composite article and their placement and orientation relative to incident sound waves and / or potential heat or flame sources.

[0064] Although various prepregs, cores and composite articles are described that include a blended flame retardant that is free or substantially free of antioxidants that change color upon exposure to an oxidizing agent, antioxidants that do not change color upon exposure to an oxidizing agent may be used. For example, tocopherol, phosphite, phosphate or phosphorylated materials, Cyanox® 1790 or other Cyanox® materials, or other compounds that can prevent oxidation of the thermoplastic materials present in the blended flame retardant material may be used in place of the phenolic antioxidant. In some embodiments, the non-phenolic antioxidant does not cause an overall color change to the composite article, even when an oxidizing agent is present in the surrounding environment.

[0065] In other cases, the prepreg or core may include one or more acid scavengers. Exemplary acid scavengers include, but are not limited to, metal stearates and metal oxides, such as calcium stearate, zinc stearate, zinc oxide, calcium lactate, or dihydrotalcite. These or other suitable acid scavengers can be used to inhibit discoloration of the prepregs and cores described herein. Alternatively, if discoloration is desired, the prepreg or core may be free of acid scavengers, for example, free or substantially free of metal stearates and metal oxides, such as calcium stearate, zinc stearate, zinc oxide, or calcium lactate.

[0066] In some cases, a phenolic antioxidant is present and may be used to manipulate the color of a composite article. For example, a thermoplastic composite article may include a porous core including reinforcing fibers and a thermoplastic material, the porous core further including a metal hydroxide flame retardant and an antioxidant, the porous core including a web formed from the reinforcing fibers held in place by the thermoplastic material, and the antioxidant in the porous core including the metal hydroxide flame retardant changes color from a first color to a second color when exposed to an oxidizing agent, and changes color from the second color back to the first color when the oxidizing agent is removed. The reaction by which the phenolic antioxidant changes color can be reversed, allowing color to be favored or inhibited depending on the particular environmental conditions present.

[0067] In some embodiments, the prepregs and cores may include additional materials or additives to impart desired physical or chemical properties. The ability to produce non-pigmented or colored articles, depending on the overall composition and environmental conditions, is a substantial attribute of using the flame retardant materials described herein. If a non-pigmented article is produced, the article may then be colored or dyed to provide a desired color, texture, pattern, and the like. For example, one or more dyes, texture improvers, colorants, viscosity modifiers, smoke suppressants, synergistic materials, lofting agents, particles, powders, fungicides, foams, or other materials may be mixed with or added to the prepregs or cores to impart a desired color, texture, or property. In some cases, the prepregs or cores may include one or more smoke suppressant compositions in an amount of about 0.2% to about 10% by weight. Exemplary smoke suppressant compositions include, but are not limited to, stannate, zinc borate, zinc molybdate, magnesium silicate, calcium zinc molybdate, calcium silicate, calcium hydroxide, and mixtures thereof. If desired, synergistic materials can be present to enhance the physical properties of the prepreg or core. For example, synergists can be present to enhance flame retardancy.

[0068] In other cases, the prepregs or cores described herein may include a thermosetting material in a desired amount, for example, a minor amount of less than about 50 weight percent based on the total weight of the prepreg or core, to impart desired properties to the core. The thermosetting material may be mixed with the thermoplastic material or added as a coating on one or more surfaces of the prepreg or core.

[0069] In certain embodiments, the prepregs or cores described herein may be configured (or used) as glass mat thermoplastic composites (GMT) or lightweight reinforced thermoplastics (LWRT). One such LWRT is prepared by HANWHA AZDEL, Inc. and sold under the trademark SUPERLITE® material. SUPERLITE® mats incorporating flame retardant materials can provide desirable attributes including, for example, flame retardancy and enhanced processing capabilities. The areal density of such GMT or LWRT may range from about 300 grams per square meter (gsm) to about 4000 gsm of GMT or LWRT, although the areal density may be less than 300 gsm or greater than 4000 gsm depending on the demands of a particular application. In some embodiments, the upper density may be less than about 4000 gsm. In certain cases, the GMT or LWRT may include a flame retardant material, such as an EG material, in combination with a Group II or Group III metal hydroxide, mixed flame retardant material, etc., disposed or present in the voids of the porous GMT or LWRT and / or on the fibers of the GMT or LWRT. When a GMT or LWRT prepreg or core is used in combination with a flame retardant material, the basis weight of the GMT or LWRT may be reduced, for example, to less than 800 gsm, less than 600 gsm, or less than 400 gsm while still providing adequate flame retardant properties. In some examples, the overall thickness of the GMT or LWRT may be about 35 mm or less after lofting, 20 mm or less after lofting, greater than 3 mm before lofting, or greater than 6 mm before lofting. In some cases, the thickness before lofting may be about 3 mm to about 7 mm, and the thickness after lofting may be about 10 mm to about 25 mm.

[0070] In manufacturing the prepregs and cores described herein, it may be desirable to use a wet laid process. For example, a liquid or fluid medium containing dispersed materials, such as thermoplastic materials, fibers, and mixed flame retardant materials, optionally with any one or more additives (e.g., other flame retardant agents) described herein, may be stirred in the presence of a gas, such as air or other gas, or may be mechanically stirred. The dispersion may then be placed on a support, such as a wire screen or other support material, to provide a substantially uniform distribution of the flame retardant material in the laid down material. To increase the dispersion and / or uniformity of the flame retardant material, the stirred dispersion may include one or more active agents, such as anionic, cationic, or nonionic, such as those sold under the name ACE Liquid by Industrial Soaps Ltd., those sold as TEXOFOR® FN 15 material by Glover Chemicals Ltd., and those sold as AMINE Fb 19 material by Float-Ore Ltd. These agents may aid in the dispersion of air in the liquid dispersion. These components can be added in the presence of air to a mixing tank, flotation cell, or other suitable device to provide a dispersion. Although an aqueous dispersion is desirably used, one or more non-aqueous fluids may also be present to aid in dispersion, modify the viscosity of the fluid, or impart other desired physical or chemical properties to the dispersion or the prepreg, core, or article.

[0071] In certain cases, after the dispersion has been mixed for a sufficient period of time, the fluid containing the suspended material can be placed onto a screen, moving wire, or other suitable support structure to provide a web of laid-down material. Suction or reduced pressure can be applied to the web to remove any liquid from the laid-down material, leaving behind the thermoplastic, flame retardant, and any other materials present, such as fibers, additives, etc. The resulting web can be dried and optionally consolidated or pressed to a desired thickness before being fully formed to provide the desired prepreg or core. A wet laying process can be used, but depending on the nature of the thermoplastic, flame retardant, and other materials present, it may be desirable to instead use airlaid, dry blend, carding, and needling processes, or other known processes used to make nonwoven products. In some cases, additional flame retardant material can be sprayed onto the surface of the prepreg or core after the prepreg or core has been cured to some degree by passing the board under multiple coating jets configured to spray the flame retardant material at an angle of about 90 degrees to the prepreg or core surface. Additionally, one or more skins may be added to the core to provide article 1180.

[0072] In some configurations, the prepregs and cores described herein can be made by combining thermoplastic materials, fibers, mixed flame retardant materials, and the like, in an aqueous solution or foam in the presence of a surfactant. The combined components can be mixed or mechanically agitated for a time sufficient to disperse the various materials and provide a substantially homogenous aqueous mixture of materials. The dispersed mixture can then be placed on any suitable support structure, such as a wire mesh or other mesh, or a support having the desired porosity. The water can then be drained through the wire mesh to form a web. The web is dried and heated to a temperature above the softening temperature of the thermoplastic powder. The web is then cooled and pressed to a predetermined thickness to produce a composite sheet having a void content of about 1% to about 95%. In an alternative embodiment, the aqueous foam also includes a binder material.

[0073] In other processes for manufacturing articles, the blended flame retardant material can also be coated or sprayed onto the prepreg after the web is formed. When a blended flame retardant material is used that includes a flame retardant material blended with a thermoplastic material, the blended flame retardant material can be sprayed or coated onto the heated prepreg to obtain melting of the thermoplastic material of the blended flame retardant material and incorporation of the prepreg including the flame retardant material.

[0074] In certain examples, a porous GMT form of prepreg or core can be produced. In certain cases, GMT can be generally prepared using chopped glass fibers, thermoplastic materials, mixed flame retardant materials, and optional thermoplastic polymer film or films, and / or woven or nonwoven fabrics made with glass fibers or thermoplastic resin fibers, such as polypropylene (PP), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polycarbonate (PC), blends of PC / PBT, or blends of PC / PET. In some embodiments, PP, PBT, PET, PC / PET blends, or PC / PBT blends can be used as the thermoplastic materials. To produce glass mats, the thermoplastic materials, reinforcing materials, flame retardant materials, and / or other additives can be added or metered into a dispersed foam contained in an open-top mixing tank equipped with an impeller. Without wishing to be bound by any particular theory, the presence of trapped air in the foam can aid in the dispersion of the glass fibers, thermoplastic materials, and flame retardant materials. In some examples, the dispersed mixture of glass and resin can be pumped through a distribution manifold to a headbox located above the wire section of a paper machine. The dispersed mixture can then be provided to a moving wire screen using a vacuum, so that the foam, but not the glass fiber, flame retardant material, or thermoplastic material, can be removed, producing a continuous, uniform, fibrous wet web. The wet web can be passed through a dryer at an appropriate temperature to reduce the moisture content and melt or soften the thermoplastic material. As the hot web exits the dryer, a surface layer, such as a film, can be laminated onto the web by passing the web of glass fiber, flame retardant material, thermoplastic material, and film through the nip of a series of heated rollers. If desired, additional layers, such as nonwoven and / or woven layers, can also be connected to one or both sides of the web along with the film to facilitate ease of handling of the fiberglass reinforced mat.The composite can then be passed through tension rolls and subsequently cut (guillotined) to the desired size for formation into the final product article. Further information regarding the preparation of such GMT complexes, including suitable materials and processing conditions used in forming such complexes, is described, for example, in U.S. Patent Nos. 6,923,494, 4,978,489, 4,944,843, 4,964,935, 4,734,321, 5,053,449, 4,925,615, 5,609,966, and U.S. Patent Application Publication Nos. US 2005 / 0082881, US 2005 / 0228108, US 2005 / 0217932, US 2005 / 0215698, US 2005 / 0164023, and US 2005 / 0161865.

[0075] In certain embodiments, a method for preventing color change of a flame retardant thermoplastic fiber reinforced porous core upon exposure to an environment including an oxidizing agent includes producing a flame retardant thermoplastic fiber reinforced porous core by combining a blended material including a reinforcing fiber, a first thermoplastic material, and a flame retardant blended with a second thermoplastic material. The flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a first thermoplastic material and a second thermoplastic material. The blended material may be substantially free of antioxidants that switch from a first color to a second color upon exposure to an environment including an oxidizing agent. In some examples, the blended material is substantially free of phenolic antioxidants. In other examples, the second thermoplastic material consists essentially of a polyolefin (e.g., polypropylene or polyethylene). In other cases, the second thermoplastic material consists of a polyolefin. In additional examples, the blended material consists of a flame retardant material blended with a polyolefin. In some examples, the flame retardant thermoplastic fiber reinforced porous core layer can be stored in an environment containing an oxidizing agent for at least 24 hours without switching from the first color to the second color.

[0076] In some examples, the first thermoplastic material includes a polyolefin. In other examples, the reinforcing fibers include glass fibers and the polyolefin of the first thermoplastic material includes polypropylene. In some examples, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material includes a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0077] In other cases, a method for reducing color change of a flame retardant thermoplastic fiber reinforced porous core includes producing a flame retardant thermoplastic fiber reinforced porous core by combining a mixed material including a reinforcing fiber, a first thermoplastic material, and a flame retardant mixed with a second thermoplastic material, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from the reinforcing fiber held in place by the first thermoplastic material and the second thermoplastic material. The mixed material includes an antioxidant that changes from a first color to a second color upon exposure to an environment including an oxidizer present at a first concentration. The antioxidant changes from the second color back to the first color upon exposure to an environment including an oxidizer present at a second concentration lower than the first concentration. The method may include storing the flame retardant thermoplastic fiber reinforced porous core in an environment including an oxidizer present at or below the second concentration to maintain the flame retardant thermoplastic fiber reinforced porous core at the first color. In some examples, the antioxidant includes a phenolic antioxidant. In other cases, the first thermoplastic material consists essentially of a polyolefin. In some embodiments, the polyolefin is polypropylene or polyethylene. In other embodiments, the first thermoplastic material is comprised of a polyolefin, such as polypropylene or polyethylene. In an additional example, the blended material is comprised of a flame retardant material blended with a polyolefin.

[0078] In certain examples, the method includes storing the flame retardant thermoplastic fiber reinforced porous core layer in an environment including an oxidizer present at a first concentration for at least 24 hours, whereby the antioxidant in the flame retardant thermoplastic fiber reinforced porous core changes from a first color to a second color. In some cases, the method includes removing the flame retardant thermoplastic fiber reinforced porous core layer from the environment including the oxidizer present at a first concentration, and storing the flame retardant thermoplastic fiber reinforced porous core layer in an environment including the oxidizer at or less than the second concentration, whereby the antioxidant in the flame retardant thermoplastic fiber reinforced porous core changes from the second color to the first color.

[0079] In some examples, the first thermoplastic material includes polypropylene and the reinforcing fibers include glass fibers. In other examples, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material includes a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0080] In other cases, a method of preventing color change in a flame retardant thermoplastic fiber reinforced porous core that includes a mixed material that includes an antioxidant includes shielding the flame retardant thermoplastic fiber reinforced porous core from exposure to an oxidizing agent in an environment surrounding the flame retardant thermoplastic fiber reinforced porous core to prevent the antioxidant from changing from a first color to a second color upon exposure to an environment that includes the oxidizing agent.

[0081] In some embodiments, the method of shielding includes encasing the flame retardant thermoplastic fiber reinforced porous core with a material to prevent the oxidizing agent from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core. In other embodiments, the method of shielding includes enclosing the flame retardant thermoplastic fiber reinforced porous core in a substantially airtight container to prevent the oxidizing agent from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core.

[0082] In some embodiments, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a thermoplastic material, and the porous core includes a coating on a first surface to prevent the oxidant from diffusing into the porous core. In other examples, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a thermoplastic material, and the porous core is sealed on each surface to prevent the oxidant from diffusing into the porous core. For example, referring to FIG. 4, an illustration is shown in which a core layer 410 is shown as sealed between two skins 420, 430. The skins 420, 430 can be selected to be substantially impermeable to gases and / or liquids. This configuration can prevent the oxidant from reaching the underlying core layer 410 and changing its color.

[0083] In some embodiments, the thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core comprises a polyolefin. In certain cases, the polyolefin comprises polypropylene. In other examples, the antioxidant is a phenolic antioxidant. In some embodiments, the reinforcing fibers of the thermoplastic fiber reinforced porous core comprise glass fibers. In some embodiments, the flame retardant comprises magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material comprises a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0084] In some examples, a method of changing the color of a flame retardant thermoplastic fiber reinforced porous core includes forming a flame retardant thermoplastic fiber reinforced porous core by combining a reinforcing fiber, a first thermoplastic material, and a mixed material including a flame retardant, an antioxidant, and a second thermoplastic material to form a web. The formed web can be exposed to an environment including an oxidizing agent to change the color of the antioxidant in the flame retardant thermoplastic fiber reinforced porous core layer from a first color to a second color. In some cases, the web is exposed to an environment including an oxidizing agent before compressing the web. In other examples, the web is exposed to an environment including an oxidizing agent after compressing the web. In some examples, the web is exposed to an environment including more than 2 ppm of an oxidizing agent before placing a skin on the web. In other examples, the web is exposed to an environment including more than 2 ppm of an oxidizing agent after placing a porous skin on the web. In some examples, the first thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core includes a polyolefin. In other examples, the polyolefin includes a polypropylene. In a further example, the antioxidant is a phenolic antioxidant. In an additional example, the reinforcing fibers of the thermoplastic fiber reinforced porous core include glass fibers. In some embodiments, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material includes a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0085] In other embodiments, a method for preventing a color change of a flame retardant thermoplastic fiber reinforced porous core upon exposure to an environment including an oxidizing agent includes manufacturing a flame retardant thermoplastic fiber reinforced porous core by combining reinforcing fibers, a flame retardant, and a thermoplastic material to form a web including reinforcing fibers held in place by the thermoplastic material, the thermoplastic material being substantially free of antioxidants that change from a first color to a second color upon exposure to an environment including an oxidizing agent. In some examples, the thermoplastic material is substantially free of phenolic antioxidants, but may optionally include non-phenolic antioxidants. In some embodiments, the thermoplastic material consists essentially of or consists of a polyolefin (e.g., polypropylene or polyethylene). In certain embodiments, the flame retardant thermoplastic fiber reinforced porous core layer is stored in an environment including an oxidizing agent for at least 24 hours without changing from a first color to a second color. In other examples, the thermoplastic material includes a polyolefin. In some embodiments, the reinforcing fibers include glass fibers and the polyolefin includes polypropylene. In another example, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0086] In another example, a method for reducing color change in a flame retardant thermoplastic fiber reinforced porous core includes producing a flame retardant thermoplastic fiber reinforced porous core by combining reinforcing fibers, a flame retardant, and a thermoplastic material to form a web including reinforcing fibers held in place by a thermoplastic material, the thermoplastic material including an antioxidant that changes from a first color to a second color upon exposure to an environment including an oxidizer present at a first concentration. The antioxidant can also change from the second color back to the first color upon exposure to an environment including an oxidizer present at a second concentration lower than the first concentration. The flame retardant thermoplastic fiber reinforced porous core can be stored in an environment including an oxidizer present at or below the second concentration to maintain the flame retardant thermoplastic fiber reinforced porous core at the first color. In some examples, the antioxidant includes a phenolic antioxidant, although non-phenolic antioxidants can also be present. In some embodiments, the thermoplastic material consists essentially of or consists of a polyolefin, for example, polypropylene or polyethylene. In certain embodiments, the method further comprises the step of: X ), for at least 24 hours, wherein the antioxidant changes from a first color to a second color. In another example, the method includes removing the flame retardant thermoplastic fiber reinforced porous core layer from an environment containing an oxidizer present at a first concentration, and storing the flame retardant thermoplastic fiber reinforced porous core layer in an environment containing the oxidizer at or less than the second concentration, wherein the antioxidant changes from the second color to the first color. In other cases, the thermoplastic material includes polypropylene and the reinforcing fibers include glass fibers. In a particular example, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0087] In another embodiment, a method of preventing a color change in a flame retardant thermoplastic fiber reinforced porous core containing an antioxidant comprises shielding the flame retardant thermoplastic fiber reinforced porous core from exposure to an oxidizing agent in an environment surrounding the flame retardant thermoplastic fiber reinforced porous core to prevent the antioxidant from changing from a first color to a second color upon exposure to an environment containing the oxidizing agent. In some examples, the shielding comprises encasing the flame retardant thermoplastic fiber reinforced porous core with a material to prevent the oxidizing agent from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core. In other embodiments, the shielding comprises enclosing the flame retardant thermoplastic fiber reinforced porous core in a substantially airtight container to prevent the oxidizing agent from reacting with the antioxidant in the flame retardant thermoplastic fiber reinforced porous core. In some examples, the flame retardant thermoplastic fiber reinforced porous core comprises a web formed from reinforcing fibers held in place by a thermoplastic material, and the porous core comprises a coating on a first surface to prevent the oxidizing agent from diffusing into the porous core. In additional examples, the flame retardant thermoplastic fiber reinforced porous core includes a web formed from reinforcing fibers held in place by a thermoplastic material, and the porous core is sealed on each surface to prevent oxidizing agents from diffusing into the porous core. In other examples, the thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core includes a polyolefin (e.g., polypropylene or polyethylene). In certain cases, the antioxidant is a phenolic antioxidant, although non-phenolic antioxidants may also be present. In some examples, the reinforcing fibers of the thermoplastic fiber reinforced porous core include glass fibers. In other examples, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0088] In a particular example, a method of changing the color of a flame retardant thermoplastic fiber reinforced porous core includes forming a flame retardant thermoplastic fiber reinforced porous core by combining reinforcing fibers, a flame retardant, and a thermoplastic material to form a web, and exposing the formed web to an environment including an oxidizing agent to change the color of the antioxidant in the flame retardant thermoplastic fiber reinforced porous core layer from a first color to a second color. In some cases, the web is exposed to an environment including an oxidizing agent before compressing the web. In other examples, the web is exposed to an environment including an oxidizing agent after compressing the web. In further embodiments, the web is exposed to an environment including more than 2 ppm of an oxidizing agent before placing a skin on the web. In additional examples, the web is exposed to an environment including more than 2 ppm of an oxidizing agent after placing a porous skin on the web. In some examples, the thermoplastic material of the flame retardant thermoplastic fiber reinforced porous core includes a polyolefin (e.g., polypropylene or polyethylene). In other examples, the antioxidant is a phenolic antioxidant, although non-phenolic antioxidants can also be present. In some examples, the reinforcing fibers of the thermoplastic fiber reinforced porous core include glass fibers. In another example, the flame retardant includes magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets the specifications of ASTM E84, Class A.

[0089] In some instances, colorimetric test methods similar to Test Method AATCC 23, dated 2015, can be performed to determine color change in composite articles. In particular, 1.5 inch by 4 inch specimens can be exposed to atmospheric oxides of nitrogen, such as those derived from the combustion of natural gas. This process reduces the amount of NO XThe concentration will be 2 ppm or more. The test can be performed at a temperature of 60°C, a relative humidity of 60-65%, and an exposure time of 72 hours. A faded control fabric (which does not change color under the test conditions) can be used as a reference to compare the color change of the flame retardant thermoplastic composite article. A colorimeter can then be used to measure the color difference between the control and the sample. The output of the colorimeter is converted to "L", "a" and "b" values. "L" represents lightness and varies from 100 (white) to 0 (black). The "a" value measures red (positive value), gray / neutral (0 value), or green (negative value). The "b" value measures yellow (positive value), gray / neutral (0 value), and blue (negative value). The ColorFlex Colorimeter (Hunter Labs) can be used to measure the color. The overall color difference or color change (ΔE) is calculated as the vector difference between two points in the color solid according to the following formula:

[0090]

number

[0091] In the formula, L o , a o , b o is the value at the first point, and L1, a1 and b1 are the values ​​at the second point.

[0092] In some cases, the composite materials described herein can be used as ex situ sensors for the presence of oxidants or oxidants. For example, pieces of material can be placed in an environment and monitored for color changes. The sensor itself may not be a real-time sensor, but can be used to measure the presence of oxidants (e.g., NO) in the atmosphere. X ) or other species can be monitored for their long-term presence. The simple and inexpensive nature of strip sensors allows for their use in a wide range of applications where electronic sensors may not be suitable.

[0093] Particular embodiments are described to further illustrate some of the novel and inventive aspects of the technology described herein. EXAMPLES

[0094] Example 1 Several test core layers were prepared to determine whether a color change occurs when a mixed flame retardant material including metal hydroxide flame retardant (MDH), polypropylene (PP), and a phenolic antioxidant is present in the core layer. The weight percentages of the materials in the samples are provided in Table 1 below. The mixed material included about 70% by weight of MDH. Glass fiber and polypropylene resin were used with the mixed flame retardant material in a wet lay process to form the core layer.

[0095] [Table 1]

[0096] The flame retardancy of the produced core layers was measured according to the ASTM E84 protocol. The results of the Flame Spread Index (FSI) and Smoke Density Index (SDI) are shown in Table 2 below. All the core layers met the Class A, E84 standard since the FSI value was less than or equal to 25.

[0097] [Table 2]

[0098] The color change of each core layer was measured according to Test Method AATCC 23 dated 2015. The results after different exposure periods of 24 hours, 48 ​​hours, 72 hours, 96 hours, and 120 hours are shown in Table 3 below.

[0099] [Table 3]

[0100] The color change results show that the pink coloration of the core layer increases over time and stabilizes after about 96 hours of environmental exposure.

[0101] Example 2 The core layer was prepared from a blended flame retardant material lacking a phenolic antioxidant. The weight percentages of the materials in the samples are provided in Table 4 below. The blended material contained approximately 70% by weight of MDH and did not contain a phenolic antioxidant. Glass fiber and polypropylene resin were used with the blended flame retardant material in a wet lay process to form the core layer.

[0102] [Table 4]

[0103] The flame retardancy of the produced core layer was measured according to the ASTM E84 protocol. The flame spread index (FSI) and smoke density index (SDI) results are shown in Table 2 below.

[0104] The flame retardancy of the produced core layers was measured for one of the core layers according to the ASTM E84 protocol. The flame spread index (FSI) and smoke density index (SDI) results are shown in Table 5 below.

[0105] [Table 5]

[0106] E84 testing of the PL0263-2 specimen is consistent with the core layer still meeting Class A E84 performance standards.

[0107] The discoloration of the PL0263-2 core layer was measured according to Test Method AATCC 23 dated 2015. After 72 hours of exposure of the core layer to the environment, a Delta E value of 3.8 was obtained, which is similar to the value of the control sample at exposure times of 24 hours or less. This result is also consistent with the removal of antioxidants from the blended flame retardant material, which avoids pinking.

[0108] When introducing elements of the examples disclosed herein, the articles "a," "an," "the," and "said" are intended to mean that one or more of the elements are present. The terms "comprising," "including," and "having" are intended to be non-limiting and mean that there may be additional elements other than the listed elements. Those skilled in the art will recognize, given the benefit of this disclosure, that various components of the examples may be interchanged or substituted for various components in other examples.

[0109] While particular aspects, examples and embodiments have been described above, it will be recognized by those of ordinary skill in the art, given the benefit of this disclosure, that additions, substitutions, modifications and variations of the disclosed exemplary aspects, examples and embodiments are possible.

Claims

1. 1. A method for reducing color change of a flame retardant thermoplastic fiber reinforced porous composite sheet upon exposure to an environment containing an oxidizing agent, the method comprising: producing a flame retardant thermoplastic fiber reinforced porous core by combining a blended material comprising reinforcing fibers, a first thermoplastic polyolefin material, and a flame retardant blended with a second thermoplastic polyolefin material, wherein said flame retardant thermoplastic fiber reinforced porous core comprises a web formed from said reinforcing fibers held in place by said first thermoplastic polyolefin material and said second thermoplastic polyolefin material, said blended material does not include an antioxidant that switches from a first color to a second color upon exposure to said environment comprising said oxidizer present at a first concentration, and said antioxidant changes from said second color back to said first color upon exposure to an environment comprising said oxidizer present at a second concentration lower than said first concentration; Pressing the produced flame-retardant thermoplastic fiber reinforced porous core to a predetermined thickness to provide the flame-retardant thermoplastic fiber reinforced porous composite sheet; and storing the flame retardant thermoplastic fiber reinforced porous composite sheet in the environment containing the oxidizer present at the first concentration without the flame retardant thermoplastic fiber reinforced porous core changing from the first color to the second color.

2. The method of claim 1, further comprising removing the flame-retardant thermoplastic fiber reinforced porous composite sheet from the environment containing the oxidant present at the first concentration, and storing the flame-retardant thermoplastic fiber reinforced porous composite sheet in the environment containing the oxidant at or below the second concentration without changing from the first color to the second color.

3. The method of claim 2 , wherein the second thermoplastic polyolefin material comprises a polyolefin.

4. The method of claim 3 , wherein the polyolefin is polypropylene or polyethylene.

5. The method of claim 1 , wherein the second thermoplastic polyolefin material comprises polypropylene.

6. The method of claim 1 , wherein the second thermoplastic polyolefin material is polyethylene.

7. The method of claim 1, wherein the antioxidant comprises a phenolic antioxidant.

8. The method of claim 1 , wherein the first thermoplastic polyolefin material comprises polypropylene.

9. The method of claim 8 , wherein the reinforcing fibers comprise glass fibers and the polyolefin of the second thermoplastic polyolefin material comprises polypropylene.

10. 10. The method of claim 9, wherein the flame retardant comprises magnesium hydroxide, aluminum hydroxide, or both, and the flame retardant thermoplastic fiber reinforced porous core meets ASTM E84, Class A specifications.

11. 1. A method for reducing color change in a flame retardant thermoplastic fiber reinforced porous core, the method comprising: producing the flame retardant thermoplastic fiber reinforced porous core by combining a mixed material comprising reinforcing fibers, a first thermoplastic material, and a flame retardant mixed with a second thermoplastic material, the flame retardant thermoplastic fiber reinforced porous core comprising a web formed from the reinforcing fibers held in place by the first thermoplastic material and the second thermoplastic material, the mixed material comprising an antioxidant that changes from a first color to a second color upon exposure to an environment comprising an oxidizer present at a first concentration, the antioxidant changing from the second color back to the first color upon exposure to an environment comprising an oxidizer present at a second concentration less than the first concentration, and the flame retardant thermoplastic fiber reinforced porous core being stored in the environment comprising an oxidizer present at or below the second concentration to maintain the flame retardant thermoplastic fiber reinforced porous core at the first color.

12. The method of claim 11 , wherein the antioxidant comprises a phenolic antioxidant.

13. The method of claim 11 , wherein the first thermoplastic material consists essentially of a polyolefin.

14. 14. The method of claim 13, wherein the polyolefin is polypropylene or polyethylene.

15. The method of claim 11 , wherein the first thermoplastic material comprises a polyolefin.

16. 16. The method of claim 15, wherein the polyolefin is polypropylene or polyethylene.

17. NO present at the first concentration. Ｘ 12. The method of claim 11, further comprising storing the flame retardant thermoplastic fiber reinforced porous core layer in an environment comprising:

18. NO present at the first concentration. Ｘ removing the flame retardant thermoplastic fiber reinforced porous core layer from the environment comprising: Ｘ 20. The method of claim 17, further comprising storing the flame retardant thermoplastic fiber reinforced porous core layer in the environment comprising:

19. The method of claim 11 , wherein the first thermoplastic material comprises polypropylene and the reinforcing fibers comprise glass fibers.

20. 20. The method of claim 19, wherein the flame retardant comprises magnesium hydroxide, aluminum hydroxide, or both, the second thermoplastic material comprises a polyolefin, and the flame retardant thermoplastic fiber reinforced porous core meets ASTM E84, Class A specifications.

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