Continuous fiber reinforced flame retardant pa66-based composite material and preparation method thereof

Abstract

This invention discloses a continuous fiber reinforced flame-retardant PA66-based composite material and its preparation method. The composite material comprises, by weight, 80-140 parts continuous fiber, 100 parts PA66 resin, 5-25 parts polyethersulfone (PES) filler, 5-20 parts halogen-free flame retardant, 0.2-0.5 parts antioxidant, and 0.2-3.0 parts lubricant. This invention improves the thermal stability, drip suppression, and flame-retardant synergistic effect of the system by introducing PES as a heat-resistant functional filler, without relying on a large amount of inorganic filler, thus mitigating the adverse effects of traditional high-filler flame-retardant systems on continuous impregnation processing. The use of phosphorus-based and / or nitrogen-based halogen-free flame retardants in synergy with PES can meet flame-retardant requirements with a lower total amount of flame retardant added. The preparation method includes mixing and melt-blending PA66 resin, PES filler, halogen-free flame retardant, antioxidant, and lubricant, then impregnating the continuous fiber with the melt in an impregnation mold, followed by cooling, traction, and winding to obtain the final product. This composite material combines flame retardancy, continuous processing stability, and structural load-bearing potential, making it suitable for applications such as rail transportation, electrical equipment housings, and lightweight structural components.

Description

Technical Field

[0001] This invention relates to the field of continuous fiber reinforced thermoplastic composite materials, specifically to a continuous fiber reinforced flame-retardant PA66-based composite material prepared with PA66 as the main component, polyethersulfone (PES) as the functional filler, and a halogen-free flame-retardant system, as well as a method for preparing the composite material. Background Technology

[0002] PA66 possesses high mechanical strength, wear resistance, heat resistance, and mature melt processing properties, making it a widely used polyamide resin in structural thermoplastic composites. Especially in continuous fiber reinforced systems, the PA66 matrix exhibits both good wetting ability and molding efficiency, making it suitable for applications in rail transportation, electrical and electronic components, and lightweight load-bearing parts.

[0003] However, PA66 itself is a combustible material with a limiting oxygen index (LOI) typically around 21%-24%, making it prone to heat release, dripping, and smoke during vertical combustion. Existing research and reviews on the flame-retardant modification of PA66 indicate that flame-retardant systems for PA66 mainly include phosphorus-based flame retardants, nitrogen-based flame retardants, and phosphorus-nitrogen synergistic flame-retardant systems. Phosphorus-based flame retardants typically achieve flame retardancy by promoting char formation, forming a thermally insulating protective layer in the condensed phase, and exerting free radical quenching effects in the gas phase. Nitrogen-based flame retardants can release inert gases at high temperatures, dilute combustible gases, and inhibit dripping to some extent. The phosphorus-nitrogen synergistic system combines char formation and thermal insulation with gas-phase flame suppression, and is therefore widely used in flame-retardant PA66 materials.

[0004] For continuous fiber reinforced PA66 matrix composites, the flame retardant mechanism itself is not the only challenge; the more prominent contradiction lies in the influence of the flame retardant component on the continuous impregnation processing window. Existing literature and patents generally indicate that additive flame retardants often require high addition amounts to achieve high flame retardancy ratings. Especially when a large number of inorganic fillers or inorganic flame retardant synergists are introduced into the system, it can easily lead to a significant increase in melt viscosity, a decrease in material fluidity, uneven dispersion of the flame retardant, and increased pressure fluctuations during processing. This can further result in insufficient continuous fiber impregnation, dry spots inside the fiber bundles, increased fiber breakage, and a decrease in the mechanical properties of the finished product.

[0005] For example, a public review on the processing modification of flame-retardant nylon materials has pointed out that although additive flame retardants and inorganic flame-retardant fillers can improve flame retardancy, excessive addition will have an adverse effect on the mechanical and processing properties of the nylon matrix. Existing patents on continuous fiber reinforced flame-retardant nylon composites mainly adopt the approach of directly blending nylon resin and flame retardant to form a melt and then impregnating the fiber, focusing on solving the problem of high strength and lightweight. However, a large amount of inorganic filler in the flame-retardant processing of PA66 continuous fibers is not conducive to the stable melt impregnation.

[0006] Continuous fiber reinforced systems differ from ordinary short fiber reinforced or injection molding systems. Continuous fiber impregnation requires the matrix melt to possess sufficient thermal stability and flame retardancy at high temperatures, while maintaining relatively stable flowability and low viscosity fluctuations to ensure that the fiber bundles can be fully opened, uniformly impregnated, and continuously drawn into shape. When a large amount of inorganic flame-retardant filler is used, it not only easily increases the apparent viscosity of the melt and equipment wear, but also weakens the interfacial flow and coating uniformity during the continuous fiber impregnation process, which is not conducive to the formation of high-quality sheets or filaments.

[0007] Therefore, it remains necessary to provide a new continuous fiber-reinforced flame-retardant PA66-based composite material system that minimizes reliance on large amounts of inorganic fillers while ensuring PA66 remains the main resin and maintaining the feasibility of continuous fiber impregnation processing. Polyethersulfone (PES) contains a high density of benzene rings and sulfone groups in its molecular structure, exhibiting high heat resistance and good intrinsic flame-retardant properties. At high temperatures, PES can form a continuous, dense, and stable expanded char layer, effectively isolating oxygen, heat, and droplets, achieving efficient flame retardancy from the condensed phase. On the one hand, PES helps improve the thermal stability, drip suppression, and char formation tendency of the matrix; on the other hand, compared to large amounts of inorganic fillers, PES, as an organic polymer filler, causes less flow interference in the continuous melt impregnation process, making it more conducive to balancing flame retardancy and continuous processing stability. Summary of the Invention

[0008] The purpose of this invention is to provide a continuous fiber reinforced flame-retardant PA66-based composite material and its preparation method, so as to solve the problems of decreased melt flowability, insufficient fiber wetting, poor processing stability and impaired overall performance of products caused by excessive addition of flame retardants and inorganic fillers in the existing PA66 continuous fiber flame-retardant system.

[0009] To achieve the above objectives, the present invention provides a continuous fiber reinforced flame-retardant PA66-based composite material, comprising, by weight, 80-140 parts of continuous fiber, 100 parts of PA66 resin, 5-25 parts of polyethersulfone (PES) filler, 5-20 parts of halogen-free flame retardant, 0.2-0.5 parts of antioxidant, and 0.2-3.0 parts of lubricant.

[0010] In this invention, PA66 serves as the main resin, providing the basic flowability, mechanical properties, and processing adaptability required for continuous fiber impregnation molding; PES is introduced into the system as a heat-resistant functional filler. The aromatic and sulfone structures in PES are beneficial for improving the thermal stability and flame-retardant synergistic effect of the system, and can play an auxiliary role in the flame-retardant performance, drip suppression, and high-temperature processing stability of the PA66 matrix without relying on a large amount of inorganic fillers.

[0011] Preferably, the amount of PES filler added is 10-20 parts. When the amount of PES added is too low, the synergistic effect of thermal stability and flame retardancy is not obvious; when the amount of PES added is too high, it may increase the melt viscosity of the system, which is not conducive to continuous impregnation and traction molding.

[0012] Preferably, the halogen-free flame retardant is selected from aluminum diethylphosphonate, melamine polyphosphate, melamine cyanurate, or combinations thereof. Phosphorus-based flame retardants preferentially exert their char-forming, heat-insulating, and free radical-inhibiting effects in the condensed phase, while nitrogen-based flame retardants preferentially exert their gas-phase dilution and drip-suppressing effects. The two can form a synergistic flame-retardant system, thereby meeting the flame-retardant requirements of the PA66 continuous fiber system at a relatively low total addition amount.

[0013] Preferably, the antioxidant is a compound system of a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is preferably antioxidant 1098 and the secondary antioxidant is preferably antioxidant 168. Since PA66, PES, and the flame retardant all undergo high temperatures during granulation and secondary impregnation, the compound antioxidant helps to inhibit thermo-oxidative degradation, reduce the risk of molecular chain breakage and melt color deterioration, and thus maintain process stability.

[0014] The present invention also provides a method for preparing the above-mentioned continuous fiber reinforced flame retardant PA66-based composite material, which adopts a more direct process route: first, PA66 resin, PES filler, flame retardant, antioxidant and lubricant are mixed and added to a twin-screw extruder for melt blending; then, the mixture is fed into an impregnation die to melt impregnate the continuous fibers; finally, the continuous fiber reinforced flame retardant PA66-based composite material filaments are obtained by cooling, drawing and winding.

[0015] The beneficial effects of this invention are as follows: Compared with the prior art, the present invention has at least the following beneficial effects: 1. Using PA66 as the main resin maintains the basic fluidity and processing adaptability required for continuous fiber impregnation molding.

[0016] 2. By introducing PES as a heat-resistant functional filler, the thermal stability, drip suppression and flame retardant synergistic effect of the system can be improved without relying on a large amount of inorganic fillers, thereby alleviating the adverse effects of traditional high-filler flame retardant systems on continuous impregnation processing.

[0017] 3. By using phosphorus-based and / or nitrogen-based halogen-free flame retardants in synergy with PES, the flame retardant modification requirements of PA66 continuous fiber composites can be met with a lower total amount of flame retardant added, which is beneficial to balance flame retardant performance and mechanical properties.

[0018] 4. The continuous fiber reinforced flame-retardant PA66-based composite material prepared by this invention has flame retardancy, continuous processing stability and structural load-bearing potential, and is suitable for fields such as rail transportation, electrical equipment and lightweight structural components. Detailed Implementation

[0019] To make the technical means and innovative features of this invention easier to understand and achieve their objectives and effects, the invention will be further described below in conjunction with specific embodiments.

[0020] Raw material description: PA66 can be made from extrusion-grade polyamide 66 resin with suitable reinforcement and modification. PES can be either powdered or granular polyethersulfone; Halogen-free flame retardants can be selected from one or more of aluminum diethylphosphinate, melamine polyphosphate, and melamine cyanurate; The preferred antioxidant is a combination of antioxidant 1098 and antioxidant 168; Lubricants such as pentaerythritol stearate and EBS, which are commonly used in this field, can be selected. Continuous fibers can be made of glass fiber or carbon fiber.

[0021] To ensure the processing stability of PA66, it is preferable to dry the PA66 resin before mixing. Example

[0022] The preparation method of continuous fiber reinforced flame-retardant PA66-based composite material is as follows: Weigh the raw materials according to the following formula: 100 parts PA66 resin, 20 parts PES filler, 8 parts aluminum diethylphosphinate, 6 parts melamine polyphosphate, 0.5 parts antioxidant 1098, 0.3 parts antioxidant 168, and 0.8 parts lubricant PETS.

[0023] PA66 resin was dried and then uniformly mixed with PES filler, flame retardant, antioxidant, and lubricant. The mixture was then fed into a twin-screw extruder for co-extrusion. The blend was used for melt impregnation of glass fiber and carbon fiber, respectively, to obtain flame-retardant PA66 glass fiber and carbon fiber reinforced composite materials. The control sample consisted of continuous fiber composite materials prepared using the same processing method, with all raw materials except PES resin in the original formulation.

[0024] The results of the tests on the obtained composite materials are shown in Table 1.

[0025] As can be seen from Table 1, compared with the PA66 glass fiber and carbon fiber reinforced composite material without flame retardant, Example 1 of the present invention shows a significant difference in flame retardancy rating and oxygen index. This indicates that the system of the present invention can more stably carry out continuous impregnation molding of glass fiber and carbon fiber, indicating that its melt flow stability and processing adaptability are better, which is more conducive to the continuous preparation of glass fiber and carbon fiber reinforced flame retardant PA66 materials. Example

[0026] In this example, the raw materials were weighed according to the following formula: 100 parts PA66 resin, 10 parts PES filler, 10 parts aluminum diethylphosphinate, 4 parts melamine cyanurate, 0.5 parts antioxidant 1098, 0.5 parts antioxidant 168, and 0.6 parts lubricant EBS. The rest is the same as in Example 1.

[0027] The results of the tests on the obtained composite materials are shown in Table 2.

[0028] As can be seen from Table 2, the composite material prepared in Example 2 of the present invention has better processing stability due to the reduction of PES content in the formulation, but the limiting oxygen index is reduced.

[0029] Mechanism and Effects Explanation: This invention argues that in PA66 continuous fiber flame-retardant systems, flame-retardant effect and processing stability need to be considered simultaneously. Phosphorus-based flame retardants can promote char formation in the condensed phase and inhibit combustion free radicals, while nitrogen-based flame retardants help release inert gases and reduce dripping tendency. PES, as a heat-resistant organic functional filler, can further enhance the structural stability of the system during high-temperature processing and the initial stage of combustion, improving the heat resistance and synergistic flame-retardant effect of the melt during impregnation. Because PES differs from a large number of inorganic fillers, its flow interference in the continuous impregnation process is relatively small, thus it is more conducive to the stable preparation of continuous fiber reinforced flame-retardant PA66-based composite materials.

[0030] Application instructions: The continuous fiber reinforced flame-retardant PA66-based composite material provided by this invention can be further used in interior and exterior trim parts of rail transit vehicles, housings of electrical equipment, lightweight structural supports, and other scenarios with comprehensive requirements for flame retardancy, continuous processing stability, and structural performance.

[0031] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. For those skilled in the art, various modifications or substitutions can be made without departing from the concept of the present invention, and such modifications or substitutions should all fall within the scope of protection of the present invention.

Claims

1. A continuous fiber-reinforced flame-retardant PA66-based composite material and its preparation method, characterized in that, By weight, it comprises the following components: 80-140 parts continuous fiber, 100 parts PA66 resin, 5-25 parts polyethersulfone PES filler, 5-20 parts halogen-free flame retardant, 0.2-0.5 parts antioxidant and 0.2-3.0 parts lubricant.

2. The continuous fiber reinforced flame-retardant PA66-based composite material and its preparation method according to claim 1, characterized in that, The amount of polyethersulfone (PES) filler added is 5-15 parts.

3. The continuous fiber reinforced flame-retardant PA66-based composite material and its preparation method according to claim 1, characterized in that, The halogen-free flame retardant is selected from one or a combination of aluminum diethylphosphonate, melamine polyphosphate, and melamine cyanurate.

4. The continuous fiber reinforced flame-retardant PA66-based composite material and its preparation method according to claim 1, characterized in that, The antioxidant is a compound system of primary antioxidant and secondary antioxidant. The primary antioxidant is selected from at least one of antioxidant 1098 and antioxidant 1010, and the secondary antioxidant is selected from at least one of antioxidant 168 and antioxidant 626.

5. The continuous fiber reinforced flame-retardant PA66-based composite material and its preparation method according to claim 1, characterized in that, The continuous fiber includes one or more of glass fiber and carbon fiber.

6. A continuous fiber reinforced flame-retardant PA66-based composite material as described in any one of claims 1-5, and a method for preparing the same, characterized in that, Includes the following steps: S1, PA66 resin, polyethersulfone PES filler, halogen-free flame retardant, antioxidant and lubricant are mixed and then added to a twin-screw extruder for melt blending; S2, the flame-retardant PA66-based composite material melt is fed into the impregnation mold, and continuous fibers are continuously fed into the impregnation mold at the same time, so that the melt impregnates the continuous fibers. S3, the impregnated composite material is cooled, drawn and wound in sequence to obtain a continuous fiber reinforced flame retardant PA66-based composite material.

7. The preparation method according to claim 6, characterized in that, In step S1, a high-speed mixer is used to thoroughly mix the mixture.

8. The preparation method according to claim 6, characterized in that, In step S1, the PA66 resin is dried before mixing.

9. The application of the continuous fiber reinforced flame-retardant PA66-based composite material according to any one of claims 1-5 in rail transit, electrical equipment housings, and lightweight structural components.