Organic-inorganic synergistic flame-retardant modified PA6 / GF composite material and preparation method thereof

Abstract

This invention discloses a modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy and its preparation method. Based on a total mass fraction of 100%, it comprises the following raw material components: 39-52% PA6 resin, 25-30% modified glass fiber, 15-20% modified ammonium polyphosphate, 5-8% zinc phosphate, 0.05-3% polytetrafluoroethylene, 0-2% lubricant, and 0-2% antioxidant. The modified glass fiber is glass fiber sequentially modified with diethylaluminum hypophosphite and a silane coupling agent; the modified ammonium polyphosphate is ammonium polyphosphate modified with a silane coupling agent. This invention, through the compounding of SAPP and zinc phosphate, synergistically enhances the double-layer interface engineering of glass fiber, significantly improving flame retardant efficiency. The resulting composite material exhibits excellent mechanical properties and good heat resistance, and can be widely used in the automotive and electrical industries to manufacture various parts and electrical materials.

Description

Technical Field

[0001] This invention relates to the field of functional polymer materials technology, specifically to a modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy and its preparation method. Background Technology

[0002] PA6 / GF composites are widely used in the automotive, electronics, and other fields due to their excellent mechanical properties, heat resistance, and processability. However, PA6 itself is flammable, with a limiting oxygen index (LOI) of only 21-22%, and GF produces a "wick effect" during combustion, accelerating flame propagation, posing a serious challenge to flame retardant modification. Flame retardant properties and mechanical properties are contradictory; too little flame retardant will not meet performance requirements, while too much will negatively impact mechanical properties.

[0003] In existing technologies, flame-retardant modification of PA6 / GF composites mainly employs phosphorus-based, nitrogen-based, and inorganic flame retardants. Commonly used flame retardants include phosphorus-nitrogen-based flame retardants such as ammonium polyphosphate (APP), melamine polyphosphate (MPP), and aluminum diethylphosphite (ADP), as well as inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide. Among these, APP is inexpensive and has high flame-retardant efficiency, but it has poor thermal stability, is hygroscopic, and has poor compatibility with the matrix; MPP has good thermal stability, but it is expensive, and its flame-retardant efficiency is limited when used alone; ADP has excellent flame-retardant properties, but it is costly and has a significant impact on the mechanical properties of the material. Traditional flame-retardant modification methods often use a single flame-retardant system or simple compounding, which suffers from problems such as difficulty in achieving both flame-retardant efficiency and mechanical properties, poor interfacial compatibility, and insufficient heat resistance. In addition, the "wick effect" of GF during combustion accelerates flame propagation, further increasing the difficulty of flame-retardant modification.

[0004] For example, patent CN119463164A discloses a flame-retardant PA6 composite material and its preparation method. It uses vanillin, dichlorophosphate and ethylenediamine as raw materials to prepare phosphorus-based flame retardants, and then prepares flame-retardant modified PA6 composite materials. However, the LOI of the material is only 27-30%, and the tensile strength is only 73-96 MPa.

[0005] Patent CN120865700A discloses an MCA / PA6 flame-retardant composite material and its preparation method. It uses MCA and Mg(OH)2 as the main and auxiliary flame retardants, respectively, to prepare a flame-retardant modified MCA / PA6 composite material through melt blending. However, this flame-retardant system requires a large amount of material, which significantly affects the mechanical properties of the material, resulting in a tensile strength of only 101-114 MPa. To address the aforementioned problems of high loss rate in flame-retardant modification and mechanical properties, there is an urgent need to develop a high-efficiency, low-cost, and comprehensively high-performance flame-retardant modified PA6 / GF composite material. Summary of the Invention

[0006] This invention addresses the problems of excessive flame retardant usage or poor flame retardant effect in PA6 / GF composite materials, resulting in significant loss of mechanical properties. It provides a modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy. By using a compounding method of modified GF, modified ammonium polyphosphate, and zinc phosphate, the compatibility between the flame retardant and the matrix is ​​effectively improved, costs are reduced, and synergistic optimization of flame retardancy and mechanical properties is achieved.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy, comprising the following raw material components by 100% total mass fraction: PA6 resin 39-52%, modified glass fiber (A-GF) 25-30%, modified ammonium polyphosphate (SAPP) 15-20%, zinc phosphate (Zn3(PO4)2) 5-8%, polytetrafluoroethylene (PTFE) 0.05-3%, lubricant 0-2%, and antioxidant 0-2%; The modified glass fiber is glass fiber (GF) modified sequentially with aluminum diethyl phosphite (ADP) and silane coupling agent (SCA); the modified ammonium polyphosphate is ammonium polyphosphate (APP) modified with silane coupling agent.

[0008] In this invention, modified ammonium polyphosphate and zinc phosphate are combined, and the interface engineering and flame-retardant functionalization of glass fiber are carried out in combination with diethylaluminum hypophosphite and silane coupling agent to construct a "multifunctional interface layer". While significantly improving the flame-retardant efficiency, it effectively improves the compatibility between the flame retardant and the matrix, reduces the cost, and achieves synergistic optimization of flame retardant and mechanical properties.

[0009] The preparation of the modified glass fiber includes the following steps: adding a solution of silane coupling agent to the glass fiber by spraying, stirring and mixing, then adding diethyl aluminum hypophosphite and continuing to stir, and finally drying to obtain the modified glass fiber.

[0010] More specifically, the preparation of the modified glass fiber includes the following steps: Glass fiber (GF) is preheated at 100-120℃ for 0.5-1 hour to remove surface moisture. The preheated glass fiber is then transferred to a high-speed mixer, where an ethanol solution of silane coupling agent (silane coupling agent mass concentration of 1-5%) is uniformly added via spraying at 60-80℃ and 200-400 rpm. The mixture is stirred continuously for 3-5 minutes to ensure the coupling agent fully coats the glass fiber surface. Diethylaluminum hypophosphite powder is then uniformly added to the treated glass fiber, and the mixture is stirred continuously at 80-100℃ for 5-10 minutes to allow the flame retardant powder to adhere to the surface of the coupling agent-treated glass fiber through physical adsorption and chemical action. The resulting material is dried at 100-120℃ for 2-4 hours to obtain modified glass fiber (A-GF). This method forms a "multifunctional interface layer," endowing GF with both flame retardant and reinforcing properties, effectively overcoming the "wick effect" of GF.

[0011] In the preparation of the modified glass fiber, the mass of diethyl aluminum hypophosphite added is 5%-15% of the mass of the glass fiber; the mass of the silane coupling agent added is 0.5%-1.0% of the mass of the glass fiber; the glass fiber is chopped glass fiber with a length of 3-6 mm.

[0012] The modified ammonium polyphosphate preparation process includes the following steps: adding a silane coupling agent to ammonium polyphosphate via spraying and mixing, followed by drying to obtain the modified ammonium polyphosphate. The silane coupling agent-modified SAPP has a lower surface energy, better matches the polarity of PA6 resin, and significantly improves dispersibility, reducing stress concentration points caused by flame retardant agglomeration. Furthermore, the silane coupling agent on the surface of the modified SAPP and the polar groups on the surface of zinc phosphate can form certain hydrogen bonds or weak chemical interactions with the amine or carboxyl groups at the ends of the PA6 molecular chains. This enhanced interfacial bonding can more effectively transfer stress between the matrix and the filler, thus maintaining high tensile strength and impact strength even with a large amount of flame retardant filling.

[0013] The modified ammonium polyphosphate preparation process more specifically includes: Ammonium polyphosphate (APP) is placed in a high-speed mixer and heated to 60-80°C. Atomized silane coupling agent ethanol solution is sprayed on the mixture while stirring. Stirring is continued for 10-20 minutes, and then dried at 80-100°C for 1-2 hours to obtain silane coupling agent modified ammonium polyphosphate.

[0014] The mass of silane coupling agent added during the preparation of the modified ammonium polyphosphate is 1%-3% of the mass of the ammonium polyphosphate.

[0015] The silane coupling agent includes one or more of the following: diethylaminomethyltriethoxysilane, anilinemethyltriethoxysilane, dichlorodimethylsilane, aminoethylaminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane (KH-540), γ-aminopropyltriethoxysilane (KH-550), and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792).

[0016] The Zn3(PO4)2 is ultrafine zinc phosphate with a particle size of 1-5 μm, approximately 2500-12500 mesh. It exhibits excellent flame-retardant synergistic effects with modified ammonium polyphosphate in this invention. The increased specific surface area of ​​the ultrafine zinc phosphate particles allows for more uniform dispersion in the composite material, resulting in more thorough physical contact and interfacial interactions with the PA6 resin matrix, SAPP, and other components. In the initial stage of combustion, ultrafine zinc phosphate disperses more rapidly and uniformly in the molten polymer, synergistically interacting with the decomposition products of SAPP, and more effectively catalyzing the dehydration and cross-linking of the PA6 matrix, promoting the formation of a more continuous, denser, and stronger expanded char layer. Its high dispersibility and high reactivity allow it to achieve flame-retardant effects comparable to or even better than those achieved with higher addition amounts of traditional coarse particles, while avoiding severe damage to the material's mechanical properties due to excessive addition (>10%).

[0017] The lubricant includes one or more of pentaerythritol stearate, ethylene bis-stearamide, calcium stearate, and zinc stearate.

[0018] The antioxidants include one or more of antioxidants 1010, antioxidant 168, antioxidant 1098, antioxidant 1076, and antioxidant 626.

[0019] The modified PA6 / GF composite material has a limiting oxygen index of ≥30, a vertical burning rating of UL94 V-0, a tensile strength ≥130MPa, a flexural strength ≥190MPa, and a notched impact strength ≥10kJ / m. 2 .

[0020] This invention also provides a method for preparing the organic unmodified PA6 / GF composite material with synergistic flame retardancy, comprising the following steps: The raw materials, excluding the modified glass fiber, are mixed according to the formula and then added to the blending equipment through the main feed port. The modified glass fiber is added to the blending equipment through the side feed port for melt blending. The modified PA6 / GF composite material is obtained by extrusion, pelletizing and drying.

[0021] Preferably, the melt blending temperature is 225-235℃, the blending equipment speed is 130-150Hz, and the drying is carried out at 110-110℃ for 4-6 hours.

[0022] Preferably, the mixing is performed in a high-speed mixer for 3-10 minutes, more preferably 3-5 minutes.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) In this invention, the flame retardant efficiency is significantly improved by compounding the inorganic synergistic flame retardant system (SAPP + zinc phosphate). The resulting PA6 / GF composite material has good flame retardant properties, excellent mechanical properties, good tensile strength retention rate and notched impact strength retention rate, good heat resistance, easy injection molding processing performance and low cost. It can be widely used in the automotive industry and electrical industry to prepare various parts and electrical materials.

[0024] (2) In this invention, a silane coupling agent is used in combination with aluminum diethylphosphite to perform interface engineering and flame retardant functionalization on glass fiber, thereby constructing a "multifunctional interface layer" that effectively improves the compatibility between the flame retardant and the matrix and reduces the negative impact on mechanical properties.

[0025] (3) The PA6 / GF composite material of the present invention has the characteristics of not yellowing at high temperature and good thermal stability. Based on the surface modification of each raw material, the components have good compatibility, good self-lubricating and nucleation crystallization properties, which can improve the shortcomings of conventional flame-retardant modified PA6 / GF composite material such as poor demolding, easy breakage of the gate, slow crystallization and low injection efficiency. Attached Figure Description

[0026] Figure 1 The image shows the carbon residue after heating and combustion of the composite materials prepared in Comparative Example 1, Example 1, and Example 2. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0028] All raw materials used in the following specific embodiments were purchased commercially. The silane coupling agent used was aminoethylaminopropyltrimethoxysilane, purchased from Dow Corning. The obtained composite material was used to prepare specimens for mechanical property testing using an injection molding machine. The injection pressure was 50~80MPa, and the injection temperature was 230~235℃.

[0029] The tensile properties test was conducted in accordance with GB / T1040.2-2022 standard. The test specimen was a standard type 1A dumbbell-shaped specimen with the following dimensions: total length ≥ 150 mm, gauge length (narrow parallel section) 60 ± 0.5 mm, width 10 ± 0.2 mm, and thickness 4 ± 0.2 mm. The test speed was 50 mm / min.

[0030] The bending performance test was conducted in accordance with the GB / T9341-2008 standard. The test specimen dimensions were: length 80±2mm, width 10±0.2mm, and thickness 4±0.2mm. The test speed was 2mm / min.

[0031] The notched impact strength test standard is GB / T1043.1-2008. The test specimen dimensions are: length 80±2mm, width 10±0.2mm, and thickness 4±0.2mm. The notch type is type A (machined), with a notch bottom radius of 0.25±0.05mm and a remaining notch thickness of 2 / 3 of the specimen thickness (approximately 2.7mm).

[0032] The limiting oxygen index (LOI) test standard is GB / T2406.2-2009. The vertical burning (UL94) rating test standard is GB / T2408-2021.

[0033] The preparation process of ADP-modified short glass fiber (A-GF) is as follows: Short glass fibers (GF) with a length of 3-6 mm were preheated at 110°C for 0.5 hours to remove surface moisture. The preheated glass fibers were then transferred to a high-speed mixer, where an ethanol solution of silane coupling agent (silane coupling agent mass concentration of 3%) was uniformly added by spraying at 65°C and 300 rpm. The mixture was stirred continuously for 5 minutes to ensure that the coupling agent fully coated the glass fiber surface. Diethylaluminum hypophosphite powder was added to the treated glass fibers, and the mixture was stirred at 90°C for 10 minutes to allow the flame retardant powder to adhere to the surface of the coupling agent-treated glass fibers through physical adsorption and chemical action. The resulting material was dried at 110°C for 3 hours to obtain modified glass fiber (A-GF).

[0034] The preparation process of modified ammonium polyphosphate (SAPP) is as follows: Ammonium polyphosphate (APP) was placed in a high-speed mixer and heated to 70°C. A silane coupling agent ethanol solution (2% of the mass of APP) was sprayed on the mixture while stirring. Stirring was continued for 15 minutes, and then the mixture was dried at 90°C for 2 hours to obtain silane coupling agent modified ammonium polyphosphate (SAPP).

[0035] Example 1 By weight percentage, PA6 resin accounts for 50%, ADP-modified short glass fiber (A-GF) accounts for 26%, modified ammonium polyphosphate (SAPP) accounts for 16%, zinc phosphate (Zn3(PO4)2) accounts for 5%, polytetrafluoroethylene (PTFE) accounts for 1%, pentaerythritol stearate (PETs) accounts for 1%, antioxidant 1010 accounts for 0.5%, and antioxidant 168 accounts for 0.5%.

[0036] Preparation method: PA6, SAPP, Zn3(PO4)2, PTFE, PETs, 1010 and 168 were added to a high-speed mixer according to the specified ratio and mixed for 3 minutes; the mixed material was fed into a twin-screw extruder through the main feed port, and A-GF (3mm in length) was fed through the side feed port; the main extruder speed was controlled at 130Hz, the glass fiber addition amount was 26wt%, and the heating temperature of all 10 heating zones of the extruder was 225℃; the extruded strip was water-cooled, pelletized and dried at 100℃ for 4 hours; after drying, the sample was prepared by injection molding machine at an injection pressure of 50MPa and an injection temperature of 230℃.

[0037] Example 2 By weight percentage, PA6 resin is 43%, A-GF is 30%, SAPP is 18%, Zn3(PO4)2 is 6%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0038] Preparation method: PA6, SAPP, Zn3(PO4)2, PTFE, PETs, 1010 and 168 were added to a high-speed mixer according to the specified ratio and mixed for 4 minutes; the mixed material was fed into a twin-screw extruder through the main feed port, and A-GF was added through the side feed port; the main extruder speed was controlled at 140 Hz, the A-GF addition amount was 30 wt%, and the heating temperature of the 10 heating zones of the extruder was 230℃; the extruded strip was water-cooled, pelletized and dried at a drying temperature of 105℃ for 5 hours; after drying, the sample was prepared by injection molding machine with an injection pressure of 65 MPa and an injection temperature of 232℃.

[0039] Example 3 By weight percentage, PA6 resin is 47%, A-GF is 25%, SAPP is 20%, Zn3(PO4)2 is 5%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0040] Preparation method: PA6, SAPP, Zn3(PO4)2, PTFE, PETs, 1010 and 168 were added to a high-speed mixer according to the specified ratio and mixed for 5 minutes; the mixed material was fed into a twin-screw extruder through the main feed port, and A-GF was added through the side feed port; the main extruder speed was controlled at 150 Hz, the A-GF addition amount was 25 wt%, and the heating temperature of all 10 heating zones of the extruder was 235 ℃; the extruded strip was water-cooled, pelletized and dried at a drying temperature of 110 ℃ for 6 hours; after drying, a sample was prepared using an injection molding machine with an injection pressure of 80 MPa and an injection temperature of 235 ℃.

[0041] Example 4 By weight percentage, PA6 resin is 45%, A-GF is 29%, SAPP is 15%, Zn3(PO4)2 is 8%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0042] Preparation method: PA6, SAPP, Zn3(PO4)2, PTFE, PETs, 1010 and 168 were added to a high-speed mixer according to the specified ratio and mixed for 4 minutes; the mixed material was fed into a twin-screw extruder through the main feed port, and A-GF was added through the side feed port; the main extruder speed was controlled at 145 Hz, the A-GF addition amount was 29 wt%, and the heating temperature of all 10 heating zones of the extruder was 228℃; the extruded strip was water-cooled, pelletized and dried, the drying temperature was 102℃ and the drying time was 4.5 h; after drying, the sample was prepared by injection molding machine, the injection pressure was 70 MPa and the injection temperature was 233℃.

[0043] Example 5 By weight percentage, PA6 resin is 42%, A-GF is 28%, SAPP is 17%, Zn3(PO4)2 is 5%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0044] Preparation method: PA6, SAPP, Zn3(PO4)2, PTFE, PETs, 1010 and 168 were added to a high-speed mixer according to the specified ratio and mixed for 4 minutes; the mixed material was fed into a twin-screw extruder through the main feed port, and A-GF was added through the side feed port; the main extruder speed was controlled at 135 Hz, the A-GF addition amount was 28 wt%, and the heating temperature of all 10 heating zones of the extruder was 232℃; the extruded strip was water-cooled, pelletized and dried at a drying temperature of 108℃ for 5.5 h; after drying, a sample was prepared using an injection molding machine with an injection pressure of 75 MPa and an injection temperature of 234℃.

[0045] Comparative Example 1 By weight percentage, PA6 is 45%, unmodified short glass fiber GF (3mm) is 30%, ammonium polyphosphate (APP) is 16%, zinc phosphate (Zn3(PO4)2) is 5%, polytetrafluoroethylene (PTFE) is 1%, pentaerythritol stearate (PETs) is 1%, antioxidant 1010 is 0.5%, and antioxidant 168 is 0.5%.

[0046] The preparation method is the same as in Example 1, except that unmodified APP and unmodified short glass fiber GF are used.

[0047] Comparative Example 2 By weight percentage, PA6 is 45%, A-GF is 30%, SAPP is 16%, CaCO3 is 5%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0048] The preparation method is the same as in Example 1, except that calcium carbonate is used instead of zinc phosphate as an auxiliary flame retardant.

[0049] Comparative Example 3 By weight percentage, PA6 is 45%, A-GF is 30%, SAPP is 16%, Zn3(PO4)2 is 5%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0050] The preparation method is the same as in Example 1, except that the glass fiber is not subjected to flame-retardant modification treatment.

[0051] Comparative Example 4 By weight percentage, PA6 is 50%, A-GF is 26%, APP is 16%, Zn3(PO4)2 is 5%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0052] The preparation method is the same as in Example 1, except that unmodified APP is used instead of modified ammonium polyphosphate (SAPP).

[0053] Comparative Example 5 By weight percentage, PA6 is 50%, Silane-modified glass fiber (SCA-GF) is 26%, SAPP is 16%, Zn3(PO4)2 is 5%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0054] The preparation method is the same as in Example 1, except that the glass fiber SCA-GF used is modified only by the coupling agent step, and aluminum diethylphosphonate is not added for the subsequent flame retardant coating step.

[0055] Comparative Example 6 By weight percentage, PA6 is 45%, A-GF is 30%, SAPP is 16%, Mg(OH)2 (particle size 1-3μm) is 5%, PTFE is 1%, PETs is 1%, 1010 is 0.5%, and 168 is 0.5%.

[0056] The preparation method is the same as in Example 1, except that magnesium hydroxide is used instead of zinc phosphate.

[0057] Performance test results and analysis The performance of the composite materials prepared in Examples 1-5 and Comparative Examples 1-3 was tested, and the results are shown in Table 1: Table 1. Flame retardant and mechanical properties of the modified PA6 / GF composites prepared in the examples and comparative examples.

[0058] The residual carbon of the composite materials prepared in Comparative Example 1, Example 1, and Example 2 after heating at a heating power of 50 kW / m² is shown in the following figures. Figure 1 As shown, (a) is Comparative Example 1 (using unmodified GF, wt 30%), (b) is Example 1 (using modified GF, wt 26%), and (c) is Example 2 (using modified GF, wt 30%).

[0059] from Figure 1 The results show that after high-temperature heating, the char residue of the composite material sample using modified GF (A-GF) turns black and becomes denser. During the heating process, a large number of highly reactive P / N-based compounds are formed in the solid phase, which promotes the formation of the char layer. The phenomenon is more obvious with the increase of the amount used, indicating that the modification of GF helps to improve the flame retardant performance.

[0060] Table 1 compares the flame retardant performance: Examples 1-5 all achieved a limiting oxygen index (LOI) of over 30% and a UL94 rating of V-0, demonstrating excellent and stable flame retardant performance. In contrast, Comparative Example 1 (using unmodified APP and GF) had the lowest flame retardant efficiency due to poor compatibility between the flame retardant and the matrix, uneven dispersion, and the "wick effect" of GF, resulting in an LOI of only 25.2% and a UL94 rating of V-2.

[0061] Comparative Example 2 (using CaCO3 instead of zinc phosphate) lost the synergistic flame-retardant effect of zinc phosphate and modified APP, with an LOI of only 26.0% and a UL94 rating of V-2, confirming the importance of specific inorganic synergists. In Comparative Example 3 (GF without flame-retardant modification), the "wick effect" of GF was not effectively suppressed, resulting in a decrease in flame-retardant performance, with an LOI of 28.6% and a UL94 rating dropping to V-1, highlighting the necessity of flame-retardant functionalization of GF.

[0062] Comparative Example 4 (unmodified APP): Due to the weak interfacial bonding between unmodified APP and the PA6 matrix, it is prone to agglomeration, affecting its char formation efficiency and uniformity in the condensed phase. Its LOI drops to approximately 27.5%, and its UL94 rating is V-1. This demonstrates the crucial role of APP surface modification in improving its compatibility and flame retardant efficiency. Comparative Example 5 (GF modified only with silane coupling agent): Although the interfacial adhesion is improved, the GF surface lacks a flame retardant layer, failing to overcome the "wick effect." Its LOI is approximately 28.8%, and its UL94 rating is V-1. This indicates that single coupling agent modification is insufficient to achieve the best flame retardant effect; it must be combined with flame retardant coating.

[0063] In Comparative Example 6 (where magnesium hydroxide replaced zinc phosphate), the flame retardant mechanism of magnesium hydroxide was mainly endothermic decomposition, with weak chemical synergy with modified APP, resulting in a significant reduction in flame retardant efficiency. The LOI was only 26.8%, and the UL94 rating was V-2. This further clarifies the irreplaceable role of zinc phosphate as a synergist in achieving a high flame retardant rating (V-0).

[0064] Mechanical property comparison: The tensile strength of Examples 1-5 remained at 130-135 MPa, the flexural strength at 190-195 MPa, and the notched impact strength at 10.5-11.2 kJ / m. 2 The material exhibits excellent mechanical properties. This demonstrates that the synergistic modification system of this invention effectively maintains the mechanical properties of the material while achieving high flame retardancy. In contrast, Comparative Example 1, due to its poorest interfacial compatibility, suffers the greatest loss in mechanical properties, with a tensile strength of only 115 MPa, a flexural strength of 172 MPa, and a notched impact strength of 8.2 kJ / m. 2 The mechanical properties of Comparative Examples 2 and 3 are between those of the Example and Comparative Example 1. Comparative Example 4 (unmodified APP): Due to stress concentration caused by APP agglomeration, its tensile strength (approximately 122 MPa) and impact strength (approximately 9.2 kJ / m²) are... 2 The results for Comparative Example 5 (GF with only one modification) were significantly lower than those for Example 1, indicating that APP modification is equally important for maintaining mechanical properties. Due to improved interfacial adhesion, its mechanical properties (e.g., tensile strength of approximately 128 MPa) were superior to Comparative Example 1, but still lagged behind Example 1, indicating that ADP coating, while providing flame retardant functionality, did not negatively impact the reinforcing effect of GF. Comparative Example 6 (with magnesium hydroxide instead of zinc phosphate) showed that the large amount of inorganic hydroxide filling caused more fragmentation in the matrix, resulting in a decrease in impact toughness (approximately 8.8 kJ / m²). 2 The example, which was significantly inferior to the one using ultrafine zinc phosphate, demonstrates the advantage of the synergistic system of the present invention in balancing flame retardancy and toughness.

[0065] Based on the data from all examples and comparative examples, it can be seen that modified ammonium polyphosphate (SAPP), ultrafine zinc phosphate, and glass fiber (A-GF) modified with both diethylaluminum hypophosphite and a silane coupling agent constitute an organic-inorganic synergistic flame retardant system. Specifically, the modification of APP improves dispersion and compatibility, the selection of zinc phosphate provides a key flame retardant synergy, and the dual modification of GF simultaneously enhances and suppresses the "wick effect." The combined effect of these three components ultimately achieves a synergistic effect between the flame retardant performance (UL94 V-0, LOI>30%) and mechanical properties (tensile strength ≥130MPa) of the PA6 / GF composite material.

Claims

1. A modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy, characterized in that, Based on a total mass fraction of 100%, the following raw material components are included: PA6 resin 39-52%, modified glass fiber 25-30%, modified ammonium polyphosphate 15-20%, zinc phosphate 5-8%, polytetrafluoroethylene 0.05-3%, lubricant 0-2%, and antioxidant 0-2%; The modified glass fiber is glass fiber that has been sequentially modified with diethylaluminum hypophosphite and a silane coupling agent; the modified ammonium polyphosphate is ammonium polyphosphate modified with a silane coupling agent.

2. The modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy according to claim 1, characterized in that, The preparation of the modified glass fiber includes the following steps: adding a solution of silane coupling agent to the glass fiber by spraying, stirring and mixing, then adding diethyl aluminum hypophosphite and continuing to stir, and finally drying to obtain the modified glass fiber.

3. The modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy according to claim 2, characterized in that, In the preparation of the modified glass fiber, the mass of diethyl aluminum hypophosphite added is 5%-15% of the mass of the glass fiber; the mass of the silane coupling agent added is 0.5%-1.0% of the mass of the glass fiber; the glass fiber is chopped glass fiber with a length of 3-6 mm.

4. The modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy according to claim 1, characterized in that, The modified ammonium polyphosphate preparation process includes the following steps: adding a silane coupling agent to ammonium polyphosphate by spraying and mixing, and then drying to obtain the modified ammonium polyphosphate.

5. The modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy according to claim 4, characterized in that, The mass of silane coupling agent added during the preparation of the modified ammonium polyphosphate is 1%-3% of the mass of the ammonium polyphosphate.

6. The modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy according to claim 1, characterized in that, The Zn3(PO4)2 is ultrafine zinc phosphate with a particle size of 1-5 μm.

7. The modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy according to claim 1, characterized in that, The lubricant includes one or more of pentaerythritol stearate, ethylene bis-stearamide, calcium stearate, and zinc stearate; The antioxidants include one or more of antioxidants 1010, antioxidant 168, antioxidant 1098, antioxidant 1076, and antioxidant 626.

8. The modified PA6 / GF composite material with synergistic organic-inorganic flame retardancy according to claim 1, characterized in that, The modified PA6 / GF composite material has a limiting oxygen index of ≥30, a vertical burning rating of UL94 V-0, a tensile strength ≥130MPa, a flexural strength ≥190MPa, and a notched impact strength ≥10kJ / m. 2 .

9. The method for preparing the organic unmodified PA6 / GF composite material with synergistic flame retardancy according to any one of claims 1-8, characterized in that, Including the following steps: The raw materials, excluding the modified glass fiber, are mixed according to the formula and then added to the blending equipment through the main feed port. The modified glass fiber is added to the blending equipment through the side feed port for melt blending. The modified PA6 / GF composite material is obtained by extrusion, pelletizing and drying.

10. The method for preparing the organic-inorganic synergistic flame-retardant modified PA6 / GF composite material according to claim 9, characterized in that, The melt blending temperature is 225-235℃, and the blending equipment speed is 130-150Hz; drying is carried out at 110-110℃ for 4-6 hours.

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