A high-strength flame-retardant polyamide 66 composite material and its preparation method and application

Abstract

The present invention discloses a high-strength, flame-retardant polyamide 66 composite material, its preparation method, and application. The raw materials for preparing the polyamide 66 composite material of the present invention include the following components: polyamide 66 resin, glass fiber, aminosilane coupling agent, 2-carboxyethylphenylphosphite, metal hydroxide, and a synergistic flame retardant, wherein the synergistic flame retardant is selected from either aluminum oxide or antimony trioxide. The polyamide 66 composite material prepared using the raw materials of the present invention not only has excellent flame retardancy (vertical burning rating reaches V-0) but also possesses excellent mechanical properties, with a tensile strength of over 155.5 MPa and a flexural strength of over 180.5 MPa. It can be widely used in industrial fields such as automobiles, construction, and aerospace.

Description

Technical Field

[0001] The present invention relates to the technical field of polyamide 66 composite materials, and in particular to a high-strength flame-retardant polyamide 66 composite material and a preparation method and application thereof. Background Art

[0002] Polyamide 66 (PA66), chemically known as poly(hexamethylenediamine adipate), is a polymer material with excellent comprehensive properties, including high mechanical strength, wear resistance, and high-temperature resistance. It is widely used in tire cord, airbag yarn, filter cloth, ropes, fishing nets, industrial conveyor belts, automotive, and electronic components. While PA66 is a self-extinguishing polymer with a vertical combustion rating of UL94 V-2 and a limiting oxygen index of 22% to 24%, it exhibits moderate flame retardancy. However, it cannot meet the demands of increasingly demanding operating environments.

[0003] In the related art, to improve the flame retardancy of polyamide 66, the blending flame retardant modification method is one of the main methods for flame retardant modification of polyamide 66. This method directly adds flame retardants (such as halogenated flame retardants, phosphorus-based flame retardants, and inorganic flame retardants) to the polyamide 66 resin matrix to enhance the flame retardancy. This method has the advantages of simple preparation, low cost, and suitability for industrial production, making it the most widely used in practical applications. However, with the deepening of research, the drawbacks of the blending flame retardant modification method have gradually become apparent. For example, the direct addition of flame retardants to polyamide 66 sacrifices other performance indicators of polyamide 66. During blending, a large amount of flame retardant is required to meet the flame retardant performance requirements. Moreover, a large amount of flame retardant addition will lead to a decrease in the strength of polyamide 66, making it difficult to meet practical needs.

[0004] Based on this, how to obtain a polyamide 66 composite material with high strength and flame retardant effect has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the prior art. To this end, the present invention provides a high-strength, flame-retardant polyamide 66 composite material, its preparation method, and its application. This polyamide 66 composite material not only exhibits excellent flame retardancy (vertical combustion rating reaches V-0) but also possesses excellent mechanical properties, with a tensile strength exceeding 155.5 MPa and a flexural strength exceeding 180.5 MPa. It is widely applicable in industries such as automotive, construction, and aerospace.

[0006] In a first aspect of the present invention, a polyamide 66 composite material is provided, wherein the raw materials for preparing the composite material include the following components:

[0007] Polyamide 66 resin, glass fiber, aminosilane coupling agent, 2-carboxyethylphenyl hypophosphorous acid, metal hydroxide, and synergistic flame retardant, wherein the synergistic flame retardant is selected from any one of aluminum oxide and antimony trioxide.

[0008] The polyamide 66 composite material according to the embodiment of the present invention has at least the following beneficial effects:

[0009] (1) The polyamide 66 composite material of the present invention has excellent flame retardant properties. The present invention uses polyamide 66 as the resin material, and by synergistically combining glass fiber, aminosilane coupling agent, 2-carboxyethylphenyl hypophosphorous acid, metal hydroxide, and synergistic flame retardant (such as aluminum trioxide or antimony trioxide), the vertical combustion grade reaches V-0 level when a small amount of flame retardant (such as 2-carboxyethylphenyl hypophosphorous acid) is added to the polyamide 66 resin base, which is beneficial for saving preparation costs. In addition, the metal hydroxide itself also has a certain flame retardant effect. The metal hydroxide releases water during the heating process (such as aluminum hydroxide decomposes into aluminum oxide and water). This water forms steam under high temperature conditions, which helps to dilute the oxygen in the combustion area, thereby slowing down the propagation speed of the flame, and further promoting the improvement of the overall flame retardant properties of the composite material.

[0010] (2) The polyamide 66 composite material of the present invention has excellent mechanical properties. The present invention uses glass fiber as the main reinforcing filler and effectively improves the interface compatibility between glass fiber and polyamide 66 resin by adding components such as aminosilane coupling agent, 2-carboxyethylphenyl hypophosphorous acid, and metal hydroxide. The amino group in the aminosilane coupling agent can form a hydrogen bond with the amide group (-CONH-) in polyamide 66, while the silane group reacts with the siloxane group on the surface of the glass fiber to form a chemical bond. This double bond enhances the interfacial adhesion between the resin and the glass fiber; 2-carboxyethylphenyl hypophosphorous acid contains a carboxyl polar group, which helps to increase the surface energy of the glass fiber, making it easier to be wetted by the polyamide 66 resin, improving the wettability of the resin to the fiber, and thus improving the interface strength.

[0011] In some embodiments of the present invention, the raw materials for preparing the polyamide 66 composite material include the following components by weight:

[0012] 60-85 parts of polyamide 66 resin;

[0013] 10~30 parts of glass fiber;

[0014] 3-8 parts of aminosilane coupling agent;

[0015] 5-10 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0016] 3-8 parts of metal hydroxide

[0017] 1~5 parts of synergistic flame retardant.

[0018] In some embodiments of the present invention, the addition ratio of the 2-carboxyethylphenylphosphinate, the metal hydroxide, and the synergistic flame retardant is 1-10:1-4:1, preferably 4-8:1.5-3:1.

[0019] In some embodiments of the present invention, the glass fiber is an alkali-free glass fiber; preferably, the length of the alkali-free glass fiber is 8-12 mm, and the diameter of the single fiber is 9-13 μm.

[0020] Using alkali-free glass fiber as a reinforcing filler helps improve the mechanical properties of polyamide 66 composites. In the present invention's preparation raw material system, it was found that using alkali-free glass fiber with a high aspect ratio exhibited even better mechanical properties, presumably due to the increased force-bearing area of ​​the alkali-free glass fiber. Furthermore, in terms of flame retardancy, alkali-free glass fiber with a high aspect ratio also exhibited superior high-temperature stability.

[0021] In some more preferred embodiments of the present invention, the alkali-free glass fiber has a length of 3 to 15 mm and a single fiber diameter of 8 to 15 μm.

[0022] In some embodiments of the present invention, the aminosilane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, and aminoethylaminopropylmethyldiethoxysilane.

[0023] The preparation raw material system of the present invention uses an aminosilane coupling agent as the main reagent for improving the interfacial compatibility between glass fiber and polyamide 66 resin. The present invention finds that compared with conventional alkylsilane coupling agents, aminosilane coupling agents have a better effect on improving the interfacial compatibility of materials. It is speculated that this is because the aminosilane coupling agent contains amino functional groups. These amino functional groups can form hydrogen bonds or covalent bonds with polar functional groups such as carboxyl (-COOH) and hydroxyl (-OH) on the surface of other components, which helps to further improve the interfacial bonding strength and stability, so that the polyamide 66 composite material has more excellent mechanical properties.

[0024] In some embodiments of the present invention, the metal hydroxide is selected from at least one of aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide.

[0025] In the present invention, the metal hydroxide can not only serve as a reaction raw material for the phosphate of the flame retardant protective layer, but also contributes to improving the surface roughness of the glass fiber and the polyamide 66 resin due to its certain corrosiveness.

[0026] In some embodiments of the present invention, the particle size of the synergistic flame retardant is 1-20 μm.

[0027] A second aspect of the present invention provides a method for preparing the polyamide 66 composite material as described in any one of the first aspects, comprising the following steps:

[0028] S1, mixing the polyamide 66 resin, aminosilane coupling agent, 2-carboxyethylphenyl hypophosphorous acid, metal hydroxide and synergistic flame retardant to obtain a mixture;

[0029] S2, extruding the mixed material and the glass fiber using a twin-screw extruder.

[0030] The preparation method according to the embodiment of the present invention has at least the following beneficial effects: the present invention adopts a twin-screw extruder to prepare the polyamide 66 composite material with the advantages of high efficiency, uniformity, and precise control, which helps to produce materials with excellent performance and high consistency.

[0031] In some embodiments of the present invention, the extrusion process uses the mixed material as the feed port raw material and the glass fiber as the fiber feeding port raw material.

[0032] In some embodiments of the present invention, the temperatures of zones one to six of the twin-screw extruder are: 220-240°C, 260-280°C, 265-285°C, 265-285°C, 265-285°C, and 260-280°C.

[0033] In some embodiments of the present invention, the screw speed of the twin-screw extruder is 350-550 r / min.

[0034] The third aspect of the present invention provides use of the polyamide 66 composite material as described in any one of the first aspects in the preparation of automobile or building materials.

[0035] Other features and advantages of the present invention will be set forth in the description that follows. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0037] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0038] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0039] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0040] Example 1

[0041] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0042] 75 parts of polyamide 66 resin;

[0043] 20 parts of alkali-free glass fiber;

[0044] 5 parts of 3-aminopropyltrimethoxysilane;

[0045] 8 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0046] 3 parts of aluminum hydroxide;

[0047] 2 parts of aluminum oxide.

[0048] Among them, the alkali-free glass fiber was purchased from Shenzhen Tianzhitu Technology Co., Ltd., with a length of 8~12mm and a single fiber diameter of 9~13μm; 3-aminopropyltrimethoxysilane was purchased from Sisibo, with the product number SiSiB® PC1110; the particle size of aluminum oxide was about 10μm.

[0049] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0050] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropyltrimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and aluminum oxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0051] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0052] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0053] Example 2

[0054] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0055] 75 parts of polyamide 66 resin;

[0056] 25 parts of alkali-free glass fiber;

[0057] 6 parts of 3-aminopropyltrimethoxysilane;

[0058] 8 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0059] 3 parts of aluminum hydroxide;

[0060] 2 parts of aluminum oxide.

[0061] Among them, the alkali-free glass fiber was purchased from Shenzhen Tianzhitu Technology Co., Ltd., with a length of 8~12mm and a single fiber diameter of 9~13μm; 3-aminopropyltrimethoxysilane was purchased from Sisibo, with the product number SiSiB® PC1110; the particle size of aluminum oxide was about 10μm.

[0062] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0063] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropyltrimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and aluminum oxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0064] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0065] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0066] Example 3

[0067] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0068] 75 parts of polyamide 66 resin;

[0069] 20 parts of alkali-free glass fiber;

[0070] 5 parts of 3-aminopropyltrimethoxysilane;

[0071] 6 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0072] 3 parts of aluminum hydroxide;

[0073] 2 parts of aluminum oxide.

[0074] Among them, the alkali-free glass fiber was purchased from Shenzhen Tianzhitu Technology Co., Ltd., with a length of 8~12mm and a single fiber diameter of 9~13μm; 3-aminopropyltrimethoxysilane was purchased from Sisibo, with the product number SiSiB® PC1110; the particle size of aluminum oxide was about 10μm.

[0075] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0076] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropyltrimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and aluminum oxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0077] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0078] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0079] Example 4

[0080] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0081] 75 parts of polyamide 66 resin;

[0082] 20 parts of alkali-free glass fiber;

[0083] 5 parts of 3-aminopropyltrimethoxysilane;

[0084] 8 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0085] 3 parts of aluminum hydroxide;

[0086] 1 part of aluminum oxide.

[0087] Among them, the alkali-free glass fiber was purchased from Shenzhen Tianzhitu Technology Co., Ltd., with a length of 8~12mm and a single fiber diameter of 9~13μm; 3-aminopropyltrimethoxysilane was purchased from Sisibo, with the product number SiSiB® PC1110; the particle size of aluminum oxide was about 10μm.

[0088] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0089] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropyltrimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and aluminum oxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0090] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0091] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0092] Example 5

[0093] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0094] 75 parts of polyamide 66 resin;

[0095] 20 parts of alkali-free glass fiber;

[0096] 5 parts of 3-aminopropyltrimethoxysilane;

[0097] 5 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0098] 5 parts of aluminum hydroxide;

[0099] 3 parts of aluminum oxide.

[0100] Among them, the alkali-free glass fiber was purchased from Shenzhen Tianzhitu Technology Co., Ltd., with a length of 8~12mm and a single fiber diameter of 9~13μm; 3-aminopropyltrimethoxysilane was purchased from Sisibo, with the product number SiSiB® PC1110; the particle size of aluminum oxide was about 10μm.

[0101] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0102] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropyltrimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and aluminum oxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0103] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0104] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0105] Example 6

[0106] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0107] 75 parts of polyamide 66 resin;

[0108] 20 parts of alkali-free glass fiber;

[0109] 5 parts of 3-aminopropyltrimethoxysilane;

[0110] 8 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0111] 3 parts of aluminum hydroxide;

[0112] 2 parts of aluminum oxide.

[0113] Among them, alkali-free glass fiber was purchased from Shenzhen Yataida Technology Co., Ltd. (item number: ECS-13-4.5), with a length of 4~5 mm and a single fiber diameter of 12~14 μm; 3-aminopropyltrimethoxysilane was purchased from Sisibo, product number SiSiB® PC1110; the particle size of aluminum oxide was approximately 10 μm.

[0114] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0115] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropyltrimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and aluminum oxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0116] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0117] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0118] Example 7

[0119] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0120] 75 parts of polyamide 66 resin;

[0121] 20 parts of alkali-free glass fiber;

[0122] 5 parts of 3-aminopropylmethyldimethoxysilane;

[0123] 8 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0124] 3 parts of aluminum hydroxide;

[0125] 2 parts of aluminum oxide.

[0126] Among them, the alkali-free glass fiber was purchased from Shenzhen Tianzhitu Technology Co., Ltd., with a length of 8~12mm and a single fiber diameter of 9~13μm; 3-aminopropylmethyldimethoxysilane was purchased from Sisibo, product number SiSiB® PC1130; the particle size of aluminum oxide was about 10μm.

[0127] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0128] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropylmethyldimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and aluminum oxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0129] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0130] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0131] Example 8

[0132] This embodiment provides a high-strength flame-retardant polyamide 66 composite material and a preparation method thereof. The high-strength flame-retardant polyamide 66 composite material is prepared from the following raw materials by weight:

[0133] 75 parts of polyamide 66 resin;

[0134] 20 parts of alkali-free glass fiber;

[0135] 5 parts of 3-aminopropyltrimethoxysilane;

[0136] 8 parts of 2-carboxyethylphenyl hypophosphorous acid;

[0137] 3 parts of aluminum hydroxide;

[0138] 2 parts of titanate trioxide.

[0139] Among them, the alkali-free glass fiber was purchased from Shenzhen Tianzhitu Technology Co., Ltd., with a length of 8~12mm and a single fiber diameter of 9~13μm; 3-aminopropyltrimethoxysilane was purchased from Sisibo, with the product number SiSiB® PC1110; the particle size of titanate trioxide is about 10μm.

[0140] The preparation method of the high-strength flame-retardant polyamide 66 composite material comprises the following steps:

[0141] S1. Fully dry the polyamide 66 resin and alkali-free glass fiber at 80° C., and weigh the polyamide 66 resin, 3-aminopropyltrimethoxysilane, 2-carboxyethylphenyl hypophosphorous acid, aluminum hydroxide, and titanate trioxide according to the above weight fractions, and fully mix them in a high-speed mixer for 3 to 5 minutes;

[0142] S2. Add the above mixture to the feeding port of a twin-screw extruder, and at the same time weigh the above-mentioned parts by weight of alkali-free glass fiber and add it through the fiber feeding port, and extrude it from the twin-screw extruder by a melt blending method, wherein the temperature parameters of zones 1 to 6 of the twin-screw extruder during the extrusion process are set as follows: 230° C., 270° C., 275° C., 275° C., 275° C., 270° C., the head temperature is 275° C., and the screw speed is set to 450 r / min;

[0143] S3. After extrusion, the extrudate was placed in a vacuum oven at 85°C and dried for 6 hours, and then molded into various specimens at 280°C.

[0144] Comparative Example 1

[0145] The difference between this comparative example and Example 1 is that the preparation raw material 2-carboxyethylphenyl hypophosphorous acid is replaced by diethyl hypophosphorous acid, and the other raw materials and preparation processes are the same.

[0146] Comparative Example 2

[0147] The difference between this comparative example and Example 1 is that 2-carboxyethylphenyl hypophosphorous acid is not added to the preparation raw materials, and the weight portion of aluminum oxide is increased to 10 parts. The other raw materials and preparation processes are the same.

[0148] Comparative Example 3

[0149] The difference between this comparative example and Example 1 is that aluminum oxide is not added to the preparation raw materials, and the weight portion of 2-carboxyethylphenyl hypophosphorous acid is increased to 10 parts. The other raw materials and preparation processes are the same.

[0150] Test Example 1: Combustion Performance Determination

[0151] This test example measured the combustion performance of the composite material samples prepared in Examples 1 to 8 and Comparative Examples 1 to 3. Specifically, the composite materials prepared above were prepared into strip samples with a length of 100 mm, a width of 10 mm, and a thickness of 0.4 mm. Then, vertical combustion tests were conducted with reference to the standard "GBT 2408-2021 Determination of combustion performance of plastics (horizontal and vertical methods)". The specific test is as follows:

[0152] Apply flame to the composite material sample with reference to the national standard. After 10 seconds, evacuate the flame. At the same time, start measuring the afterflame time t1 with a timer in seconds, and record t1 and whether molten droplets or burning materials appear. If so, indicate whether they ignite the cotton pad.

[0153] When the flame of the sample goes out, immediately re-place the test flame under the sample, keeping the central axis of the blowtorch tube vertical and the tip of the blowtorch approximately 10 mm below the bottom of the sample. Hold this position for 10 seconds. After applying the flame to the sample for the second time, immediately extinguish the blowtorch and simultaneously use a timer to measure the sample's afterflame time t2 and afterglow time t3 to the nearest second. Note and record any particles or droplets dripping from the sample. If so, observe whether the cotton pad ignites.

[0154] If one of the five samples processed in the same state does not meet the classification criteria, another group of five samples processed in the same state should be tested. f If the total afterflame time is between 51s and 55s for V-0 or between 251s and 255s for V-1 and V-2, an additional set of five specimens shall be tested. All specimens in the second set shall meet all the criteria specified for that class.

[0155] Each group of samples was repeated 5 times and the average value was taken. The rating standard of vertical burning test is shown in the following table.

[0156] Table 1: Vertical Burning Rating Standards

[0157]

[0158] The vertical combustion performance test results of the composite material samples prepared in Examples 1 to 8 and Comparative Examples 1 to 3 are shown in Table 2.

[0159] Table 2: Vertical combustion performance test results

[0160]

[0161] The above results show that the flame retardant levels of the high-strength flame-retardant polyamide 66 composite materials prepared in Examples 1 to 8 of the present invention all meet the requirements of relevant flame-retardant materials, and their vertical combustion performance test results reach the V-0 level. Among them, the high-strength flame-retardant polyamide 66 composite materials prepared in Examples 1 and 7 have the best flame retardant performance. After the second application of flame, the afterflame time plus the afterglow time (t2+t3) of a single sample is as low as 16s; the flame retardant performance of the high-strength flame-retardant polyamide 66 composite material in Example 3 is slightly lower than that of other examples, but still reaches the V-0 level, which is presumably related to the reduction of the flame retardant 2-carboxyethylphenylphosphonic acid. As a highly efficient reactive flame retardant, 2-carboxyethylphenylphosphonic acid helps to form a stable carbonized layer during the combustion process, providing excellent flame retardant effect.

[0162] Compared with Example 1, in Comparative Example 1, 2-carboxyethylphenyl hypophosphorous acid was replaced with diethyl hypophosphorous acid. The results showed a slight decrease in its combustion performance, which is presumably related to its inherent properties. Diethyl hypophosphorous acid, as a common flame retardant ingredient, is similar to 2-carboxyethylphenyl hypophosphorous acid. It can combine with metal salts such as aluminum hydroxide or magnesium hydroxide to form phosphates, which exert a flame retardant effect. At the same time, the moisture released during the reaction also helps to improve the flame retardant effect. However, compared with diethyl hypophosphorous acid, 2-carboxyethylphenyl hypophosphorous acid also contains a benzene ring, which is presumably helpful in improving the ability to suppress flames.

[0163] Compared with Example 1, Comparative Example 2 did not add 2-carboxyethylphenyl hypophosphorous acid. The results showed that the flame retardant effect was significantly reduced, and the dripping material ignited the cotton pad during the combustion process. It is speculated that this is related to the formation of phosphate. When 2-carboxyethylphenyl hypophosphorous acid was not added to the system, it was unable to interrupt the combustion reaction by forming a phosphate protective layer with aluminum hydroxide during the combustion process, thus greatly reducing the flame retardant effect. This shows that adding a certain amount of 2-carboxyethylphenyl hypophosphorous acid to the system of the present invention helps to significantly improve the flame retardant effect of the composite material.

[0164] Compared with Example 1, no aluminum oxide was added in Comparative Example 3, and its effect was significantly reduced. In the present invention, aluminum oxide is mainly added as a synergistic flame retardant, which has a synergistic effect with 2-carboxyethylphenyl hypophosphorous acid. On the one hand, it can improve the barrier effect of the carbon layer by changing the carbon slag composition of the composite material, or by absorbing heat during the combustion process under high temperature conditions, blocking the transfer of heat and oxygen, thereby slowing down the combustion process and protecting the composite material; on the other hand, during the combustion process, aluminum oxide can provide thermal insulation and a protective layer, while 2-carboxyethylphenyl hypophosphorous acid can directly participate in the flame retardant process through chemical reactions. This combination can enable the composite material to obtain both physical insulation and chemical flame retardant protection in a high temperature environment, synergistically improving the flame retardant effect.

[0165] Test example 2: Mechanical properties test

[0166] This test example measured the mechanical properties of the composite material samples prepared in Examples 1-8 and Comparative Examples 1-3. The control group was polyamide 66 resin. Specifically, the composite materials prepared above were each prepared into strip specimens with a length of 100 mm, a width of 10 mm, and a thickness of 0.4 mm. The tensile and flexural properties were then tested using the following test methods:

[0167] (1) Tensile properties test: The tensile properties (including tensile strength and elongation at break) of the composite material samples were tested using an electronic universal testing machine at a test speed of 20 mm / min. The specific method was referred to GB / T 1040-2018 standard.

[0168] (2) Bending performance test: The bending performance (including bending strength and bending modulus) of the composite material samples was tested using an electronic universal testing machine. During the measurement, the instrument's operating speed was 2 mm / min, the measuring range was 64 mm, and the sensor output power was 500 N. The specific measurement method was based on the GB / T 9341-2008 standard.

[0169] The mechanical properties test results of the above composite materials are shown in Table 3.

[0170] Table 3: Mechanical properties test results

[0171]

[0172] The above results show that the high-strength, flame-retardant polyamide 66 composite materials prepared using Examples 1 to 8 of the present invention exhibit excellent mechanical properties, with the composite material prepared in Example 2 being the best, with a tensile strength of 169.6 MPa and a flexural strength of 191.5 MPa. The mechanical properties of the composite material prepared in Example 1 were inferior, but still significantly improved compared to the comparative example. Secondly, by comparing Examples 1 and 5, it can be analyzed that when the relative proportions of 2-carboxyethylphenylphosphinate, metal hydroxide, and synergistic flame retardant are reduced, the mechanical properties slightly decrease.

[0173] Compared with Example 1, when low aspect ratio alkali-free glass fiber is used (such as Example 6), the mechanical properties of the composite material obtained are reduced, which is presumably related to the decrease in uniformity of stress distribution. The load-bearing area of ​​low aspect ratio alkali-free glass fiber is reduced relative to that of high aspect ratio alkali-free glass fiber.

[0174] In addition, it is worth noting that in the composite material of the present application, the mechanical properties of the composite material using 3-aminopropyltrimethoxysilane coupling agent are relatively higher than those using 3-aminopropylmethyldimethoxysilane coupling agent (see Examples 1 and 7). This is presumably related to the methoxy functional group (-OCH3). 3-aminopropylmethyldimethoxysilane coupling agent contains three methoxy functional groups, while 3-aminopropylmethyldimethoxysilane coupling agent contains only two methoxy functional groups. The methoxy functional groups can react with glass fibers to form siloxane bonds (-Si-O-Si), thereby promoting the formation of a stable siloxane network, which helps to improve the mechanical properties of the composite material. In addition, since the aminosilane coupling agent contains amino functional groups, these amino functional groups can form hydrogen bonds or covalent bonds with polar functional groups such as carboxyl (-COOH) and hydroxyl (-OH) on the surface of other components, which helps to further improve the interfacial bonding strength and stability.

[0175] Compared with Example 1, in Comparative Example 1, 2-carboxyethylphenyl hypophosphorous acid was replaced with diethyl hypophosphorous acid. The results showed that its mechanical properties were significantly reduced, with the tensile strength decreasing by 9.65% and the flexural strength decreasing by 6.06%. It is speculated that this is related to the absence of the carboxyl functional group. 2-carboxyethylphenyl hypophosphorous acid contains a carboxyl functional group, which helps to improve the interfacial adhesion and interfacial compatibility, thereby promoting the improvement of mechanical properties.

[0176] Compared with Example 1, 2-carboxyethylphenyl hypophosphorous acid was not added in Comparative Example 2, and aluminum oxide was not added in Comparative Example 3. From the above test results, it can be seen that the mechanical properties are significantly reduced, which is presumably related to the reduction in interfacial properties. When 2-carboxyethylphenyl hypophosphorous acid is lacking in the system, the interfacial properties between polyamide 66 and glass fiber will be reduced.

[0177] In summary, the present invention provides a high-strength flame-retardant polyamide 66 composite material, a preparation method and application thereof. The polyamide 66 composite material prepared by the present invention by compounding an aminosilane coupling agent, a metal hydroxide, 2-carboxyethylphenyl hypophosphorous acid and aluminum oxide (or antimony trioxide) not only has excellent mechanical properties, but also has a vertical combustion rating of V-0 level, and has broad application prospects.

[0178] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A polyamide 66 composite material, characterized by: According to weight fraction, the raw materials include the following components: 60-85 parts of polyamide 66 resin; 10~30 parts of glass fiber; 3-8 parts of aminosilane coupling agent; 5-10 parts of 2-carboxyethylphenyl hypophosphorous acid; 3-8 parts of metal hydroxide; 1~5 parts of synergistic flame retardant; The metal hydroxide is selected from at least one of aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide; and the synergistic flame retardant is selected from any one of aluminum oxide and antimony trioxide.

2. The polyamide 66 composite material according to claim 1, characterized in that: The glass fiber is alkali-free glass fiber.

3. The polyamide 66 composite material according to claim 2, characterized in that: The alkali-free glass fiber has a length of 3 to 15 mm and a single fiber diameter of 8 to 15 μm.

4. The polyamide 66 composite material according to claim 1, characterized in that: The aminosilane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane and aminoethylaminopropylmethyldiethoxysilane.

5. The polyamide 66 composite material according to claim 1, characterized in that: The particle size of the synergistic flame retardant is 1-20 μm.

6. A method for preparing the polyamide 66 composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, mixing the polyamide 66 resin, aminosilane coupling agent, 2-carboxyethylphenyl hypophosphorous acid, metal hydroxide and synergistic flame retardant to obtain a mixture; S2, extruding the mixed material and the glass fiber using a twin-screw extruder.

7. The preparation method according to claim 6, characterized in that: The temperatures of zones one to six of the twin-screw extruder are: 220-240°C, 260-280°C, 265-285°C, 265-285°C, 265-285°C, and 260-280°C.

8. The preparation method according to claim 7, characterized in that: The screw speed of the twin-screw extruder is 350-550 r / min.

9. Use of the polyamide 66 composite material according to any one of claims 1 to 5 in the preparation of automobile or building materials.

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