In-situ infusion molding method for fiber-reinforced thermoplastic composite materials

Abstract

The invention discloses a fiber-reinforced thermoplastic composite in-situ impregnation molding method, belonging to the technical field of resin-based composite material preparation. The present invention solves the problems that the existing methacrylate resin has a large volume shrinkage, the fiber volume content of the molded thermoplastic composite is low, and the fiber impregnation effect is poor. The present invention first adopts a prepolymerization method to prepare a prepolymer resin with a viscosity of 100-900mPa·S, realizes the regulation of the viscosity of the resin system, and then mixes the prepolymer resin, initiator, internal mold release agent, filler and dispersant uniformly, pours into a glue injection device and impregnates the fiber in the molding mold, heats up and polymerizes, and obtains a fiber-reinforced thermoplastic composite. The thermoplastic methacrylate resin system for in-situ impregnation molding of fiber-reinforced thermoplastic composite provided by the present invention has a simple preparation method, a greatly shortened molding cycle, a significantly improved economic benefit, and a product with good mechanical properties, weather resistance, etc., is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to an in-situ impregnation molding method for a fiber-reinforced thermoplastic composite material, belonging to the technical field of preparation of resin-based composite materials. Background Art

[0002] Polymer-based composite materials are composed of resin (matrix) and fiber (reinforcement). They have the advantages of light weight, high strength, corrosion resistance, fatigue resistance, and small temperature deformation. They have been maturely applied in aerospace, automotive industry, construction, energy, energy storage and other fields. Compared with fiber-reinforced thermosetting resin composites, fiber-reinforced thermoplastic resin composites have higher toughness, higher impact strength and recyclability, which are in line with the "dual carbon" strategic goals. However, thermoplastic resins such as polyamide, polycarbonate, and polyvinyl chloride have high viscosity, and high temperature and pressure are required to prepare composite materials, resulting in complex molding processes and high energy consumption. The products have low fiber content, small specifications, and single shapes. Therefore, thermoplastic resins have not been widely promoted and applied.

[0003] Thermoplastic methacrylate resin has low viscosity, and its in-situ polymerization provides a new way for the molding of fiber-reinforced thermoplastic resin composites, realizing the preparation of thermoplastic composites with high impregnation degree, high fiber content and high performance. However, the large heat release of methacrylate resin leads to excessive temperature in the mold cavity and explosion, and the high curing shrinkage rate reduces the molding quality of the composite material, which restricts the development of fiber-reinforced methacrylate resin-based composite materials. In addition, the existing thermoplastic methacrylate resin system for in-situ polymerization molding mainly uses a single methyl methacrylate monomer, such as patents: CN202010654354.3, CN202010654404.8, but due to the low glass transition temperature of methyl methacrylate, the weather resistance of the product is poor. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a thermoplastic methacrylate resin system for in-situ infusion molding of fiber-reinforced thermoplastic composite materials, a preparation method and an in-situ infusion molding method.

[0005] The technical solution of the present invention:

[0006] One of the purposes of the present invention is to provide a fiber reinforced thermoplastic composite material in-situ impregnation molding method, the method comprising the following steps:

[0007] S1, preparing a prepolymer resin with a viscosity of 100-900 mPa·S;

[0008] S2, the prepolymer resin, initiator, internal mold release agent, filler and dispersant are mixed uniformly to obtain a thermoplastic resin for in-situ impregnation molding, the resin is poured into a glue injection device and impregnated into the fibers in the molding mold, and the temperature is increased to polymerize to obtain a fiber-reinforced thermoplastic composite material.

[0009] It is further defined that the prepolymer resin in S1 is prepared by polymerization of methyl methacrylate, butyl methacrylate and isobornyl methacrylate.

[0010] It is further defined that the initiator in S2 is one or a mixture of tert-butyl perbenzoate, nitrogen-nitrogen dimethyl-p-toluidine, dibenzoyl peroxide, and azobisisobutyronitrile.

[0011] It is further defined that the internal release agent in S2 is one or a mixture of silicone oil, zinc stearate, and magnesium stearate.

[0012] It is further defined that the filler in S2 is one or a mixture of aluminum hydroxide, precipitated silica, light calcium carbonate, heavy calcium carbonate, clay, organic clay, and mica powder.

[0013] It is further defined that the dispersant in S2 is a modified polyurethane solution.

[0014] It is further defined that the modified polyurethane solution is BYK-W974, a BYK chemical wetting and dispersing agent.

[0015] It is further defined that S2 contains 100 parts of prepolymer resin, 0.5-7 parts of initiator, 1-3 parts of internal release agent, 0.5-100 parts of filler and 0.5-3 parts of dispersant.

[0016] It is further defined that the method of pouring the resin into the injection device and impregnating the molding mold in S2 is to continuously prepare in-situ infusion injection pultrusion molding or vacuum-assisted in-situ infusion transfer molding.

[0017] The second object of the present invention is to provide a method for preparing a prepolymer resin used in the in-situ infusion molding of the above-mentioned fiber reinforced thermoplastic composite material, which comprises: stirring methyl methacrylate, butyl methacrylate and isobornyl methacrylate uniformly, adding an initiator, and stirring under nitrogen protection and 30°C-90°C water bath conditions until the viscosity is 100-900mPa·S.

[0018] It is further defined that methyl methacrylate is 90 parts, butyl methacrylate is 2-4 parts, and isobornyl methacrylate is 6-8 parts.

[0019] It is further defined that the initiator is one or a mixture of tert-butyl perbenzoate, nitrogen-nitrogen dimethyl-p-toluidine, dibenzoyl peroxide, and azobisisobutyronitrile, and the amount of the initiator is 0.5-3 parts.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The thermoplastic resin system for fiber in-situ impregnation molding prepared by the present invention has a viscosity maintained below 1000 mPa·S, good fluidity, low shrinkage, long application period, excellent mechanical properties and durability after curing, and its comprehensive performance is greatly improved compared with a single methyl methacrylate monomer system.

[0022] (2) The present invention firstly adopts a prepolymerization method to prepare a prepolymer resin with a viscosity of 100-900 mPa·S, thereby achieving the regulation of the viscosity of the resin system and reducing the heat release and curing shrinkage rate in the subsequent product molding process.

[0023] (3) The prepolymer resin provided by the present invention is obtained by polymerization of methyl methacrylate, butyl methacrylate and isobornyl methacrylate, wherein methyl methacrylate is used as a prepolymer monomer to improve hardness; butyl methacrylate is used as a prepolymer monomer to improve solvent resistance and flexibility; and isobornyl methacrylate is used as a prepolymer monomer to increase the glass transition temperature.

[0024] (4) The present invention uses tert-butyl perbenzoate, nitrogen-nitrogen dimethyl paratoluidine, dibenzoyl peroxide, and azobisisobutyronitrile composite initiator to make the polymerization rate, polymerization time, polymer average molecular weight and molecular weight distribution meet the requirements of industrial composite material in-situ polymerization molding production and product performance requirements. The internal release agent migrates to the interface between the product and the mold during molding to play a demoulding role; the filler adjusts the viscosity of the resin system, reduces the shrinkage rate of the product, and improves the surface finish, impact strength and compression strength of the product; the dispersant prevents filler agglomeration and prevents sedimentation.

[0025] (5) The thermoplastic methacrylate resin system for in-situ impregnation molding of fiber-reinforced thermoplastic composite materials provided by the present invention has good processability, a long applicable period, storage at room temperature can reach more than 72 hours, and the viscosity is maintained below 1000mPa·S, with excellent process performance, and is suitable for in-situ polymerization molding. In addition, the raw material of the resin system is methacrylate prepolymer, and the viscosity of the resin system can be dynamically regulated for a specific in-situ impregnation molding method. The molding cycle of the composite material prepared by the resin system is greatly shortened, and the economic benefits are significantly improved. The volume shrinkage of the product is ≤0.8%, the fiber impregnation degree is ≥90%, and the fiber volume fraction is ≥60%. It has good mechanical properties, weather resistance and other comprehensive properties, which are greatly improved compared with the single methyl methacrylate monomer resin system, and solves the problems of large volume shrinkage of existing methacrylate resins, low fiber volume content of molded thermoplastic composite materials, and poor fiber impregnation effect. It has extremely broad application prospects in the fields of aerospace, automobile industry, construction, energy, energy storage, etc.

[0026] (6) The thermoplastic methacrylate resin system for in-situ infusion molding of fiber-reinforced thermoplastic composite materials provided by the present invention has a simple preparation method, greatly shortens the molding cycle, significantly improves the economic benefit, and the product has good mechanical properties, weather resistance, etc., and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of in-situ infusion injection pultrusion for continuous preparation of fiber-reinforced thermoplastic methacrylate resin-based composites;

[0028] Figure 2 Schematic diagram of vacuum-assisted in-situ infusion transfer molding of fiber-reinforced thermoplastic methacrylate resin-based composite materials. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0031] The parts in the following examples are all by mass, and all raw materials in the examples are commercially available.

[0032] Embodiment 1:

[0033] This embodiment adopts Figure 1 The continuous preparation of fiber-reinforced thermoplastic methacrylate resin-based composite materials by in-situ infusion injection pultrusion molding is shown in the following specific steps:

[0034] The first step, pre-molding process:

[0035] Yarn threading: draw the glass fiber bundle from the fiber yarn rack and pass it through the yarn guide plate, pultrusion die and traction device; fiber tensioning: use the traction device to clamp and tension the fiber bundle and control the bundle tension within the limited value range; pultrusion die preheating: heat the pultrusion die to 120℃.

[0036] The second step is to prepare a thermoplastic methacrylate resin system:

[0037] Weigh 90 parts of methyl methacrylate, 3 parts of butyl methacrylate and 7 parts of isobornyl methacrylate; after mixing the above three resins evenly, add 0.5 parts of NN-dimethyl-p-toluidine and 1 part of dibenzoyl peroxide, stir at 50°C until uniform, and prepolymerize at 50°C (prepolymerization temperature) for 100 minutes to obtain a mixture with a viscosity of 500mPa·S, then quickly cool the uniform mixture obtained to 20°C, add 2 parts of dibenzoyl peroxide, 2 parts of zinc stearate, 1 part of magnesium stearate, 20 parts of filler nano-aluminum hydroxide, 10 parts of precipitated silica and 2 parts of dispersant, and mix well to obtain a thermoplastic methacrylate resin system for in-situ dip molding.

[0038] The third step is in-situ impregnation injection pultrusion:

[0039] The thermoplastic methacrylate resin is transferred to the glue injection machine, and the injection gun is connected to the glue injection port of the pultrusion die.

[0040] Injection and impregnation, the thermoplastic methacrylate resin is pumped into the mold from the injection machine to complete the fiber impregnation in the pultrusion mold; pultrusion molding, start the traction device, pull the fiber bundle through the pultrusion mold, the thermoplastic methacrylate resin undergoes polymerization reaction in the pultrusion mold (the temperature in the mold is 120°C), and forms an integral composite material part with the fiber to complete the molding.

[0041] According to standard GBT3365-2008, the fiber impregnation degree of the product was measured to be 92% and the fiber volume fraction was 65%. According to standard GBT13096-2008, the tensile strength of the product was measured to be 1240MPa and the bending strength was 1290MPa. According to ASTMD955, the volume shrinkage of the product was measured to be 0.15%.

[0042] Comparative Example 1:

[0043] The difference between this comparative example and Example 1 is that a non-prepolymerized thermoplastic methacrylate resin system is used for in-situ impregnation, injection and pultrusion of glass fiber composite materials. The specific preparation process is as follows:

[0044] The first step, pre-molding process:

[0045] Yarn threading: draw the glass fiber bundle from the fiber yarn rack and pass it through the yarn guide plate, pultrusion die and traction device; fiber tensioning: use the traction device to clamp and tension the fiber bundle and control the bundle tension within the limited value range; pultrusion die preheating: heat the pultrusion die to 120℃.

[0046] The second step is to prepare a thermoplastic methacrylate resin system:

[0047] Weigh 90 parts of methyl methacrylate, 3 parts of butyl methacrylate, 7 parts of isobornyl methacrylate, 3 parts of dibenzoyl peroxide, 2 parts of zinc stearate, 1 part of magnesium stearate, 20 parts of filler nano-aluminum hydroxide, 10 parts of precipitated silica, and 2 parts of dispersant, and mix them thoroughly to obtain a thermoplastic methacrylate resin system for in-situ dip molding.

[0048] The third step is in-situ impregnation injection pultrusion:

[0049] The thermoplastic methacrylate resin is transferred to the glue injection machine, and the injection gun is connected to the glue injection port of the pultrusion die.

[0050] Injection and impregnation: Thermoplastic methacrylate resin is pumped into the mold from the injection machine to complete fiber impregnation in the pultrusion mold. In pultrusion molding, the traction device is started to pull the fiber tow through the pultrusion mold, and the thermoplastic methacrylate resin undergoes polymerization reaction in the pultrusion mold to form an integral composite material part with the fiber, completing the molding.

[0051] According to standard GBT3365-2008, the fiber impregnation degree of the product was measured to be 85% and the fiber volume fraction was 52%. According to standard GBT13096-2008, the tensile strength of the product was measured to be 968 MPa and the bending strength was 990 MPa. According to ASTM D955, the volume shrinkage of the product was measured to be 3.41%, which is larger than that of the product in Example 1.

[0052] Embodiment 2:

[0053] This embodiment adopts Figure 2 The vacuum-assisted fiber-reinforced thermoplastic methacrylate resin-based composite material is formed by in-situ impregnation transfer molding. The specific steps are as follows:

[0054] The first step is raw material processing before molding:

[0055] The required number of fiber layers is calculated based on the target sheet size and carbon fiber volume fraction, and the fiber cloth is cut to the required size.

[0056] The second step is to prepare thermoplastic methacrylate resin:

[0057] Weigh 90 parts of methyl methacrylate, 2 parts of butyl methacrylate and 8 parts of isobornyl methacrylate; after mixing the above three resins evenly, add 1 part of dibenzoyl peroxide, stir at 50°C until uniform, and prepolymerize at 50°C (prepolymerization temperature) for 30 minutes to obtain a mixture with a viscosity of 100 mPa·S, then quickly cool the uniform mixture obtained to 20°C, add 2 parts of dibenzoyl peroxide, 1 part of zinc stearate, 20 parts of filler nano-aluminum hydroxide and 1 part of dispersant, and mix well to obtain a thermoplastic methacrylate resin system for in-situ dip molding.

[0058] The third step is resin in-situ impregnation transfer molding:

[0059] Thermoplastic methacrylate resin is transferred into a glue injection tank, and connected to the glue injection port of the mold with a PTFE tube.

[0060] Evacuate the glue outlet of the mold, control the vacuum degree to 0.02MPa, and the vacuum time to 40min. After the gas in the mold cavity is exhausted, open the glue injection valve, and use partial vacuum to suck the resin in the glue injection tank into the mold cavity to impregnate the fiber. Control the filling time to 30min. After completing the mold filling and impregnation, close the glue outlet valve, and control the temperature according to the pre-set heating program. In this example, the temperature is kept at 50℃ for 1 hour and 110℃ for 0.5 hour to form a composite material sheet.

[0061] According to standard GBT3365-2008, the fiber impregnation degree of the product was measured to be 95% and the fiber volume fraction was 63%. According to ASTMD3039, the tensile strength of the product was measured to be 2000MPa. According to ASTMD7264, the bending strength of the product was measured to be 2100MPa. According to ASTMD955, the volume shrinkage of the product was measured to be 0.2%.

[0062] Comparative Example 2:

[0063] The difference between this comparative example and Example 1 is that a non-prepolymerized thermoplastic methacrylate resin system is used for in-situ impregnation, injection and pultrusion of glass fiber composite materials. The specific preparation process is as follows:

[0064] The first step is raw material processing before molding:

[0065] The required number of fiber layers is calculated based on the target sheet size and carbon fiber volume fraction, and the fiber cloth is cut to the required size.

[0066] The second step is to prepare thermoplastic methacrylate resin:

[0067] Weigh 90 parts of methyl methacrylate, 2 parts of butyl methacrylate, 8 parts of isobornyl methacrylate, 3 parts of dibenzoyl peroxide, 1 part of zinc stearate, 20 parts of filler nano-aluminum hydroxide, and 1 part of dispersant, and mix them thoroughly to obtain a thermoplastic methacrylate resin system for in-situ dip molding.

[0068] The third step is resin in-situ impregnation transfer molding:

[0069] Thermoplastic methacrylate resin is transferred into a glue injection tank, and connected to the glue injection port of the mold with a PTFE tube.

[0070] Evacuate the glue outlet of the mold, control the vacuum degree to 0.02MPa, and the vacuum time to 40min. After the gas in the mold cavity is exhausted, open the glue injection valve, and use partial vacuum to suck the resin in the glue injection tank into the mold cavity to impregnate the fiber. Control the filling time to 30min. After completing the mold filling and impregnation, close the glue outlet valve, and control the temperature according to the pre-set heating program. In this example, the temperature is kept at 50℃ for 1 hour and 110℃ for 0.5 hour to form a composite material sheet.

[0071] According to standard GBT3365-2008, the fiber impregnation degree of the product was measured to be 87% and the fiber volume fraction was 53.6%. According to ASTMD3039, the tensile strength of the product was measured to be 1330 MPa. According to ASTMD7264, the bending strength of the product was measured to be 1370 MPa. According to ASTMD955, the volume shrinkage of the product was measured to be 4.2%, which is larger than that of the product in Example 2.

[0072] The embodiments of the invention disclosed above are only used to help illustrate the invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the invention, so that those skilled in the art can understand and use the invention well.

Claims

1. A fiber reinforced thermoplastic composite material in-situ infusion molding method, characterized in that: include: S1, preparing a prepolymer resin with a viscosity of 100-900 mPa·s; Methyl methacrylate, butyl methacrylate and isobornyl methacrylate were stirred evenly, an initiator was added, and the mixture was stirred in a water bath at 30°C-90°C under nitrogen protection until the viscosity reached 100-900 mPa·s; 90 parts of methyl methacrylate, 2-4 parts of butyl methacrylate, 6-8 parts of isobornyl methacrylate; The initiator is one or a mixture of tert-butyl perbenzoate, nitrogen-nitrogen dimethyl para-toluidine, dibenzoyl peroxide, and azobisisobutyronitrile, and the amount of the initiator is 0.5-3 parts; S2, mixing the prepolymer resin, initiator, internal mold release agent, filler and dispersant uniformly, pouring into the injection device and impregnating the fibers in the molding mold, heating and polymerizing to obtain a fiber-reinforced thermoplastic composite material.

2. The fiber reinforced thermoplastic composite in-situ infusion molding method according to claim 1, characterized in that: The prepolymer resin is prepared by polymerization of methyl methacrylate, butyl methacrylate and isobornyl methacrylate.

3. The fiber reinforced thermoplastic composite in-situ infusion molding method according to claim 1, characterized in that: The initiator is one or a mixture of tert-butyl perbenzoate, nitrogen-nitrogen dimethyl p-toluidine, dibenzoyl peroxide, and azobisisobutyronitrile.

4. The fiber reinforced thermoplastic composite in-situ infusion molding method according to claim 1, characterized in that: The internal mold release agent is one or a mixture of silicone oil, zinc stearate and magnesium stearate.

5. The fiber reinforced thermoplastic composite in-situ infusion molding method according to claim 1, characterized in that: The filler is one or a mixture of aluminum hydroxide, precipitated silica, light calcium carbonate, heavy calcium carbonate, clay, organic clay, and mica powder.

6. The fiber reinforced thermoplastic composite in-situ infusion molding method according to claim 1, characterized in that: The dispersant is a modified polyurethane solution.

7. The fiber reinforced thermoplastic composite in-situ infusion molding method according to claim 1, characterized in that: 100 parts of prepolymer resin, 0.5-7 parts of initiator, 1-3 parts of internal release agent, 0.5-100 parts of filler, and 0.5-3 parts of dispersant.

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