Hybrid phosphorus flame retardant and halogen-free flame-retardant polyamide 6 composite

Abstract

In order to overcome the shortcomings and deficiencies existing in the prior art, the application discloses a hybrid phosphorus flame retardant and a halogen-free flame-retardant polyamide 6 composite material, and belongs to the field of high polymer composite materials.The hybrid phosphorus flame retardant is prepared by the following method: step 1.1, stirring single element phosphorus and hypophosphite in anhydrous ethanol uniformly at room temperature; step 1.2, placing the suspension obtained in step 1.1 in a ball mill tank and performing in a nitrogen gas atmosphere, and ball milling for a period of time to obtain a hybrid; and step 1.3, drying the hybrid obtained in step 2 at a certain temperature to obtain the hybrid phosphorus flame retardant.The halogen-free flame-retardant polyamide 6 composite material comprises, by weight, 70-91 parts of polyamide 6 resin, 8-20 parts of the hybrid phosphorus flame retardant, 0.5-3 parts of an antioxidant and 0.5-7 parts of a coupling agent.The halogen-free flame-retardant polyamide 6 composite material has excellent flame-retardant performance, excellent hot wire performance and excellent tracking resistance performance under the interaction of various phosphorus flame retardants, and thus has a good application prospect in the fields of new energy automobile high-voltage components, charging piles and electrical connectors.

Description

Technical Field

[0001] This invention relates to the field of flame retardants and flame retardant materials, specifically to a hybrid phosphorus-based flame retardant and a halogen-free flame retardant polyamide 6 composite material. Background Technology

[0002] Polyamide 6, as an important engineering plastic, possesses excellent mechanical strength, abrasion resistance, and chemical corrosion resistance, and is widely used in electronics, automotive, and home appliances. However, polyamide 6 has a limiting oxygen index of only about 22.1%, making it a flammable material; the dripping phenomenon during its combustion further exacerbates the risk of flame spread. These inherent defects significantly limit the further application of polyamide 6 in high-voltage components of new energy vehicles, smart grid equipment, and other high-reliability electrical systems.

[0003] While traditional brominated flame retardants can achieve a UL-94 V-0 rating for polyamide 6, they generate dioxin-like toxic products during combustion, making it difficult to meet environmental regulations such as RoHS and REACH, and even more so for the new energy vehicle and electrical equipment sectors. Inorganic hydroxide flame retardants require addition levels as high as 50-60 wt% to achieve effective flame retardancy, but this leads to a significant decrease in material impact strength and melt flowability, thus affecting injection molding and part reliability. Therefore, the application of this type of flame retardant system in polyamide 6 is limited.

[0004] In recent years, phosphorus-based flame retardants have attracted widespread attention due to their advantages such as low smoke, low toxicity, and high efficiency. Among them, red phosphorus, with its high phosphorus content, can promote rapid char formation during combustion, improving the condensed phase flame retardancy and glow wire resistance of the material; diethylaluminum hypophosphite has the dual functions of gas-phase flame suppression and condensed phase char formation, while also improving the material's tracking performance and reducing the risk of electrical insulation failure. However, in existing polyamide 6 flame retardant systems, red phosphorus suffers from poor dispersibility and insufficient compatibility with the matrix interface; diethylaluminum hypophosphite may also reduce the mechanical properties of the material at high addition levels, and the synergistic flame retardant effect of the two in traditional physical mixing systems is not significant, with obvious limitations in improving glow wire and tracking performance.

[0005] Therefore, how to further improve the glow wire resistance and anti-tracking performance of polyamide 6 while ensuring its flame retardant properties has become the core challenge in current research on the flame retardant modification of polyamide 6. If a higher degree of synergy and interface reconstruction between elemental phosphorus and hypophosphite can be achieved at the microscale, it is expected that more efficient flame retardant and electrical safety performance can be achieved at lower addition levels, promoting its widespread application in high-voltage electrical components such as relays, switches, and charging pile housings. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a phosphorus-based flame retardant to improve the glow wire performance and tracking resistance of halogen-free flame-retardant polyamide 6 composite materials.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A hybrid phosphorus-based flame retardant is prepared by the following method: Step 1.1 At room temperature, mix elemental phosphorus and hypophosphite in anhydrous ethanol until homogeneous.

[0008] Step 1.2 The suspension obtained in Step 1.1 is placed in a ball mill jar and milled in a nitrogen atmosphere for a period of time to obtain a hybrid.

[0009] Step 1.3 The hybrid obtained in Step 2 is dried at a certain temperature to obtain a hybrid phosphorus flame retardant.

[0010] Further, the elemental phosphorus mentioned in step 1 is at least one of red phosphorus and black phosphorus, preferably red phosphorus; the hypophosphite is at least one of aluminum hypophosphite, diethyl aluminum hypophosphite, and isopropyl aluminum hypophosphite, preferably diethyl aluminum hypophosphite.

[0011] Further, the mass ratio of elemental phosphorus and hypophosphite in step 1 is (0.5~3): (0.5~3), preferably (1.5~3): (1~2).

[0012] Further, in step 2, the ball-to-material ratio is (10~40):1, the ball milling speed is 200~500 rpm, and the ball milling time is 0.5~8 h, preferably the ball-to-material ratio is (20~30):1, the ball milling speed is 300~400 rpm, and the ball milling time is 2~4 h.

[0013] Furthermore, the drying temperature in step 3 is 70~120 °C, the drying time is 12~24 h, preferably the drying temperature is 80~90 °C, and the drying time is preferably 16~20 h.

[0014] In addition, the present invention provides a halogen-free flame-retardant polyamide 6 composite material, which, by weight, comprises: 70-91 parts of polyamide 6 resin, 8-20 parts of hybrid phosphorus flame retardant, 0.5-3 parts of antioxidant, and 0.5-7 parts of coupling agent.

[0015] Further, the antioxidant is at least one of 1098 and antioxidant 168, preferably antioxidant 1098; the coupling agent is at least one of KH550, KH560 and KH570, preferably KH550.

[0016] In addition, the present invention provides a method for preparing a halogen-free flame-retardant polyamide 6 composite material, comprising the following steps: Step 2.1 Mix the hybrid phosphorus flame retardant and antioxidant evenly to obtain the first premix; Step 2.2 Mix the first premix, coupling agent and polyamide 6 resin evenly to obtain the second premix; Step 2.3 The second premix is ​​added to an extruder for melt blending, extrusion granulation, and tableting to obtain the halogen-free flame-retardant polyamide 6 composite material.

[0017] Furthermore, in step 2.3, the heating temperature of the twin-screw extruder during extrusion granulation is controlled as follows: Zone 1 is 180~200 ℃, Zone 2 is 200~240 ℃, and Zone 3 is 220~260 ℃; the screw speed of the twin-screw extruder is 30~150 rpm. Furthermore, the tableting conditions described in step 2.3 are 200~270 ℃, 3~25 MPa, and holding pressure for 3~20 min.

[0018] The beneficial effects of this invention are as follows: The polyamide 6 composite material provided by this invention utilizes a ball milling process to pretreat red phosphorus and aluminum diethylphosphite (ADP), effectively solving problems such as poor flame retardant dispersion, weak interfacial compatibility, and insufficient synergistic efficiency in traditional physical blending systems. Compared with pure polyamide 6, conventional physical blending flame retardant systems, and single phosphorus-based flame retardant systems, the material of this invention can pass the UL-94 V-0 rating test with a significantly reduced amount of flame retardant added; in the cone calorimetry test, its peak heat release rate and total heat release are significantly reduced; simultaneously, the material's resistance to tracking and glow wire resistance are significantly improved. Attached Figure Description

[0019] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0020] Figure 1 This is a scanning electron microscope image of the ball-milled hybrid phosphorus flame retardant of the present invention.

[0021] Figure 2 Images of the vertical combustion test of the sample from Example 1 and Example 3 of this invention.

[0022] Figure 3 The heat release rate and total heat release of the sample in Example 1 and Example 3 of this invention are given.

[0023] Figure 4 The TG / DTG curves are for the sample of Example 2 of the present invention and for Comparative Examples 2, 3, and 6.

[0024] Figure 5These are microscopic images of the carbon residue from the sample of Example 2 of the present invention and from Comparative Examples 3, 4, and 6. Detailed Implementation

[0025] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0026] Example 1 This embodiment provides a method for preparing a halogen-free flame-retardant polyamide 6 composite material: Polyamide 6 resin, hybrid phosphorus flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, the polyamide 6 resin and hybrid phosphorus flame retardant were dried in an oven at 80 °C for 20-24 h to remove moisture completely before use. By weight fraction, the raw material composition was: 88 parts polyamide 6 resin, 9 parts ball-milled hybrid phosphorus flame retardant (red phosphorus and diethylaluminum hypophosphite in a mass ratio of 1:1, ball-milling time of 3 h), 1 part antioxidant 1098, and 2 parts coupling agent KH550. The hybrid phosphorus flame retardant and antioxidant 1098 were thoroughly mixed to obtain the first premix. The first premix, polyamide 6 resin, and coupling agent KH550 were then thoroughly mixed to obtain the second premix. The second premix was added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder were as follows: zone 1: 190~200 ℃, zone 2: 220~240 ℃, zone 3: 240~250 ℃, and the screw speed was 50~100 rpm. The obtained granules were pressed into tablets for 10~15 min in a tablet press at a temperature of 230~240 ℃ and a pressure of 9~13 MPa to obtain halogen-free flame-retardant polyamide 6 composite material.

[0027] Example 2 This embodiment provides a method for preparing a halogen-free flame-retardant polyamide 6 composite material: Polyamide 6 resin, hybrid phosphorus flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, polyamide 6 resin and hybrid phosphorus flame retardant were dried in an oven at 80 °C for 20-24 h to remove moisture completely before use. By weight fraction, the raw material composition was: 86 parts polyamide 6 resin, 11 parts ball-milled hybrid phosphorus flame retardant (red phosphorus and diethylaluminum hypophosphite in a mass ratio of 1:1, ball-milling time of 3 h), 1 part antioxidant 1098, and 2 parts coupling agent KH550. The hybrid phosphorus flame retardant and antioxidant 1098 were thoroughly mixed to obtain the first premix. The first premix, polyamide 6 resin, and coupling agent KH550 were then thoroughly mixed to obtain the second premix. The second premix was added to a twin-screw extruder for melt blending, extrusion, and granulation. The temperatures of each zone of the twin-screw extruder were: zone 1 190~200 ℃, zone 2 220~240 ℃, and zone 3 240~250 ℃, with a screw speed of 50~100 rpm. The obtained granules were then pressed into tablets for 10~15 min at a temperature of 230~240 ℃ and a pressure of 9~13 MPa to obtain halogen-free flame-retardant polyamide 6 composite material.

[0028] Example 3 This embodiment provides a method for preparing a halogen-free flame-retardant polyamide 6 composite material: Polyamide 6 resin, hybrid phosphorus flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, the polyamide 6 resin and hybrid phosphorus flame retardant were dried in an oven at 80 °C for 20-24 h to remove moisture completely before use. By weight fraction, the raw material composition was: 84 parts polyamide 6 resin, 13 parts hybrid phosphorus flame retardant (red phosphorus and diethylaluminum hypophosphite in a mass ratio of 1:1, ball-milled for 3 h), 1 part antioxidant 1098, and 2 parts coupling agent KH550. The hybrid phosphorus flame retardant and antioxidant 1098 were thoroughly mixed to obtain the first premix. The first premix, polyamide 6 resin, and coupling agent KH550 were then thoroughly mixed to obtain the second premix. The second premix was added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder were as follows: zone 1: 190~200 ℃, zone 2: 220~240 ℃, zone 3: 240~250 ℃, and the screw speed was 50~100 rpm. The obtained granules were pressed into tablets for 10~15 min in a tablet press at a temperature of 230~240 ℃ and a pressure of 9~13 MPa to obtain halogen-free flame-retardant polyamide 6 composite material.

[0029] Comparative Example 1 This comparative example provides a method for preparing pure polyamide 6: Comparative Example 1 Polyamide 6 resin was dried at 80 °C for 20–24 h to completely remove moisture before use. Specifically, the polyamide 6 resin was dried in an oven at 80 °C for 20–24 h to completely remove moisture, obtaining the dried components. Subsequently, the polyamide 6 resin was added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder were: zone 1 190–200 °C, zone 2 220–240 °C, and zone 3 240–250 °C, with a screw speed of 50–100 rpm. The obtained granules were then pressed into tablets for 10–15 min in a tablet press at a temperature of 230–240 °C and a pressure of 9–13 MPa to obtain pure polyamide 6 material.

[0030] Comparative Example 2 This comparative example provides a method for preparing a polyamide 6 composite material: Polyamide 6 resin, red phosphorus flame retardant, diethylphosphite flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, polyamide 6 resin, red phosphorus flame retardant, and diethylphosphite flame retardant were dried in an oven at 80°C for 20-24 hours to fully remove moisture before use. By weight fraction, the raw material composition was: 86 parts polyamide 6 resin, 5.5 parts red phosphorus flame retardant, 5.5 parts diethylphosphite flame retardant, 1 part antioxidant 1098, and 2 parts coupling agent KH550. The first premix was obtained by thoroughly mixing red phosphorus flame retardant, diethyl aluminum hypophosphite flame retardant, and antioxidant 1098. The first premix, polyamide 6 resin, and coupling agent KH550 were then thoroughly mixed to obtain the second premix. The second premix was added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder were as follows: zone 1: 190~200 ℃, zone 2: 220~240 ℃, and zone 3: 240~250 ℃, with a screw speed of 50~100 rpm. The obtained granules were then tableted for 10~15 min in a tablet press at a temperature of 230~240 ℃ and a pressure of 9~13 MPa to obtain a halogen-free flame-retardant polyamide 6 composite material.

[0031] Comparative Example 3 This comparative example provides a method for preparing a polyamide 6 composite material: Polyamide 6 resin, red phosphorus flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, the polyamide 6 resin and red phosphorus flame retardant were dried in an oven at 80 °C for 20-24 h to remove moisture completely before use. By weight fraction, the raw material composition was: 86 parts polyamide 6 resin, 11 parts red phosphorus flame retardant, 1 part antioxidant 1098, and 2 parts coupling agent KH550. After thoroughly mixing red phosphorus flame retardant and antioxidant 1098, a first premix is ​​obtained. Then, the first premix, polyamide 6 resin, and coupling agent KH550 are thoroughly mixed to obtain a second premix. The second premix is ​​added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder are as follows: zone 1 is 190~200 ℃, zone 2 is 220~240 ℃, and zone 3 is 240~250 ℃, with a screw speed of 50~100 rpm. The obtained granules are then tableted in a tablet press at a temperature of 230~240 ℃ and a pressure of 9~13 MPa for 10~15 min to prepare samples, thus obtaining a halogen-free flame-retardant polyamide 6 composite material.

[0032] Comparative Example 4 This comparative example provides a method for preparing a polyamide 6 composite material: Polyamide 6 resin, diethylphosphite flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, polyamide 6 resin and red phosphorus flame retardant were dried in an oven at 80 °C for 20-24 h to remove moisture completely before use. By weight fraction, the raw material composition was: 86 parts polyamide 6 resin, 11 parts diethylphosphite flame retardant, 1 part antioxidant 1098, and 2 parts coupling agent KH550. After thoroughly mixing red phosphorus flame retardant and antioxidant 1098, a first premix is ​​obtained. Then, the first premix, polyamide 6 resin, and coupling agent KH550 are thoroughly mixed to obtain a second premix. The second premix is ​​added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder are as follows: zone 1 is 190~200 ℃, zone 2 is 220~240 ℃, and zone 3 is 240~250 ℃, with a screw speed of 50~100 rpm. The obtained granules are then tableted in a tablet press at a temperature of 230~240 ℃ and a pressure of 9~13 MPa for 10~15 min to prepare samples, thus obtaining a halogen-free flame-retardant polyamide 6 composite material.

[0033] Comparative Example 5 This comparative example provides a method for preparing a polyamide 6 composite material: Polyamide 6 resin, red phosphorus flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, polyamide 6 resin and red phosphorus flame retardant were dried in an oven at 80 °C for 20-24 h to remove moisture completely before use. By weight fraction, the raw material composition was: 86 parts polyamide 6 resin, 5.5 parts ball-milled red phosphorus flame retardant (ball-milling time 3 h), 5.5 parts ball-milled diethylaluminum hypophosphite flame retardant (ball-milling time 3 h), 1 part antioxidant 1098, and 2 parts coupling agent KH550. After thoroughly mixing red phosphorus flame retardant and antioxidant 1098, a first premix is ​​obtained. Then, the first premix, polyamide 6 resin, and coupling agent KH550 are thoroughly mixed to obtain a second premix. The second premix is ​​added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder are as follows: zone 1 is 190~200 ℃, zone 2 is 220~240 ℃, and zone 3 is 240~250 ℃, with a screw speed of 50~100 rpm. The obtained granules are then tableted in a tablet press at a temperature of 230~240 ℃ and a pressure of 9~13 MPa for 10~15 min to prepare samples, thus obtaining a halogen-free flame-retardant polyamide 6 composite material.

[0034] Comparative Example 6 This comparative example provides a method for preparing a polyamide 6 composite material: Polyamide 6 resin, red phosphorus flame retardant, ammonium polyphosphate flame retardant, antioxidant 1098, and coupling agent KH550 were mixed evenly in a certain proportion, melt-blended in a twin-screw extruder, extruded and granulated, and then pressed into sheets to obtain halogen-free flame-retardant polyamide 6 composite material. Specifically, polyamide 6 resin, red phosphorus flame retardant, and ammonium polyphosphate flame retardant were dried in an oven at 80 °C for 20-24 h to remove moisture completely before use. By weight fraction, the raw material composition was: 86 parts polyamide 6 resin, 5.5 parts red phosphorus flame retardant, 5.5 parts ammonium polyphosphate flame retardant, 1 part antioxidant 1098, and 2 parts coupling agent KH550. The first premix was obtained by thoroughly mixing red phosphorus flame retardant, ammonium polyphosphate flame retardant, and antioxidant 1098. The first premix, polyamide 6 resin, and coupling agent KH550 were then thoroughly mixed to obtain the second premix. The second premix was added to a twin-screw extruder for melt blending, extrusion granulation, and the temperatures of each zone of the twin-screw extruder were as follows: zone 1: 190~200 ℃, zone 2: 220~240 ℃, and zone 3: 240~250 ℃, with a screw speed of 50~100 rpm. The obtained granules were then tableted for 10~15 min in a tablet press at a temperature of 230~240 ℃ and a pressure of 9~13 MPa to obtain a halogen-free flame-retardant polyamide 6 composite material.

[0035] The combustion performance, electrical properties and thermal stability of polyamide 6 composite materials were tested according to the following standards, and the results are shown in Tables 1 and 2.

[0036] Combustion performance: LOI standard test according to GB / T 2406-2015, UL-94 standard test according to GB / T 2408-2008; cone calorimetry test according to ISO 5660.

[0037] Electrical performance: GWIT and GWFI standard tests are conducted according to GB / T 5169.11-2017, and CTI standard tests are conducted according to GB / T4207-2022.

[0038] Thermal stability: TG / DTG tests were conducted according to GB / T33047.2-2021 standard.

[0039] Figure 1 These are scanning electron microscope (SEM) images of red phosphorus and aluminum diethylphosphite after ball milling. Figure 1 As shown, after high-energy ball milling, the two materials achieved close physical mixing and surface composite at the micron scale.

[0040] Figure 2 This is a comparison diagram of the effects of vertical combustion in Example 2 and Comparative Example 1. Figure 2 As can be seen, the Comparative Example 1 sample exhibits a V-2 flammability rating: it continues to burn (<30 s) after the flame is removed, accompanied by significant dripping. The dripping can ignite the absorbent cotton below, indicating that the material has a high fire risk. In contrast, the Example 2 sample exhibits a V-0 rating: it self-extinguishes rapidly (<10 s) after the flame is removed, no dripping is observed during combustion, and the absorbent cotton is not ignited. This phenomenon confirms that the ball-milled hybrid phosphorus flame retardant can effectively promote the formation of a stable char layer on the polyamide 6 matrix, achieving a gas-phase-condensed phase synergistic flame retardant mechanism by isolating heat and oxygen transfer, thereby significantly inhibiting dripping and blocking the combustion chain reaction.

[0041] Figure 3 The data provided are the cone calorimetry test data for Example 2 and Comparative Example 1, including the heat release rate (HRR) and total heat release (THR). Example 2 comprises a composite material consisting of 86 parts polyamide 6, 11 parts ball-milled hybrid phosphorus flame retardant (where the mass ratio of red phosphorus to diethylaluminum hypophosphite is 1:1, and the ball milling time is 3 h), 1 part antioxidant 1098, and 2 parts coupling agent KH550. Figure 3 As can be seen, compared with Comparative Example 1, Example 2 exhibits better flame retardant behavior, with its HRR and THR values ​​reduced by 50.4% and 8.4%, respectively. The heat release rate and total heat release of the material are significantly reduced, improving the flame retardant performance of the material.

[0042] Figure 4 The TG / DTG curves for the sample of Example 2 and Comparative Examples 2, 3, and 6 are shown. Referring to the data in Table 2, the TTG of the sample of Example 2 is... 5% With T max All of them were significantly higher than the comparatives, indicating that its thermal stability was better; at the same time, its experimental char residue was 6.5%, which was also higher than each comparative, indicating that the hybrid phosphorus flame retardant can effectively promote the char formation of polyamide 6 and increase the char residue.

[0043] Figure 5 Microscopic photographs of the combustion residues of the sample from Example 2 and Comparative Examples 3, 4, and 6 are shown. As shown, the char layer in Comparative Example 3 is thin and cracked; the char layer in Comparative Example 4 is significantly damaged with numerous cracks; and the char layer in Comparative Example 6 has a more fragmented structure. In contrast, Example 2 formed a dense, complete, and continuous char layer structure.

[0044] The flame retardant and electrical properties of the polyamide 6 composite materials in Examples 1 to 3 and Comparative Examples 1 to 6 were tested using the appropriate standards, and the results are shown in Table 1. Table 1. Test results of flame retardant and electrical properties of polyamide 6 composite materials in Examples 1 to 3 and Comparative Examples 1 to 7. Table 2. Thermal stability test results of polyamide 6 composite materials in Comparative Examples 3, 4, 6 and Example 2. in conclusion: 1. The test results of Examples 1-3 show that as the amount of ball-milled hybrid phosphorus flame retardant added gradually increased from 9 parts to 13 parts, the LOI increased from 27.6% to 28.1%, and the GWIT increased from 775℃ to 800℃ and then stabilized. Simultaneously, the material maintained its UL-94 V-0 flame retardant rating, and its electrical properties at GWFI 960℃ and CTI 600V remained constant. Overall, Example 2, with an addition amount of 11 parts, showed the most balanced and outstanding performance.

[0045] 2. The test results of Example 2 and Comparative Example 1 show that the flame retardancy rating of Example 2 was improved from V-2 to V-0, and the LOI increased to 27.9%; at the same time, the peak heat release rate decreased by 50.4%, and the total heat release decreased by 8.4%. In addition, the glow wire performance and tracking resistance of the material were also significantly improved, indicating that the solution has excellent electrical properties while being highly effective in flame retardancy.

[0046] 3. As can be seen from the comparative analysis of Example 2, Comparative Example 2 and Comparative Example 5, red phosphorus and diethylaluminum hypophosphite form a hybrid structure through ball milling. Compared with samples that are ball-milled alone or not ball-milled, its tightly interlocked structure can promote the formation of a dense and continuous char layer during combustion, enhance the flame retardant synergy between the gas phase and the condensed phase, and significantly improve the flame retardant and glow wire performance. At the same time, the dense char layer also helps to slow down the formation and spread of char marks, thereby improving the resistance to tracking.

[0047] 4. A comparison of Examples 2, 3, 4, and 6 shows that the combined ball milling of red phosphorus and diethylaluminum hypophosphite significantly improves flame retardancy and electrical properties compared to using them alone. However, replacing diethylaluminum hypophosphite with a conventional red phosphorus synergist, ammonium polyphosphate flame retardant, results in a decrease in both flame retardancy and electrical properties. (See Table 2 for details.) Figure 3 Data analysis shows that: T in Example 2 5% The temperature was 390.5℃, T max The temperature was 444.5℃, R max The pyrolysis temperature is 1.8% / ℃, and the char residue rate reaches 6.5%. Its higher thermal decomposition temperature indicates improved thermal stability, which helps to improve flame retardant and glow wire performance. Figure 4 Microscopic images further show that Example 2 forms a denser carbon layer structure, which can effectively suppress the formation of conductive pathways and provide a structural basis for improving tracking resistance.

[0048] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A hybrid phosphorus-based flame retardant, characterized in that, It is prepared by the following method: Step 1.1 At room temperature, mix elemental phosphorus and hypophosphite in anhydrous ethanol until homogeneous; Step 1.2 The suspension obtained in Step 1.1 is placed in a ball mill jar and milled in a nitrogen atmosphere for a period of time to obtain a hybrid. Step 1.3 The hybrid obtained in Step 2 is dried at a certain temperature to obtain a hybrid phosphorus flame retardant.

2. The hybrid phosphorus-based flame retardant according to claim 1, characterized in that, The elemental phosphorus mentioned in step 1 is at least one of red phosphorus and black phosphorus.

3. The hybrid phosphorus-based flame retardant according to claim 1, characterized in that, The hypophosphite mentioned in step 1 is at least one of aluminum hypophosphite, diethylaluminum hypophosphite, and isopropylaluminum hypophosphite.

4. The hybrid phosphorus-based flame retardant according to claim 1, characterized in that, In step 1, the mass ratio of elemental phosphorus to hypophosphite is (0.5~3):(0.5~3).

5. The hybrid phosphorus-based flame retardant according to claim 1, characterized in that, In step 2, the ball-to-material ratio is 10~40:1, the ball mill speed is 200~500 rpm, and the ball milling time is 0.5~8 h.

6. The hybrid phosphorus-based flame retardant according to claim 1, characterized in that, The drying operation described in step 3 at a certain temperature is as follows: drying in an oven at 70~120 °C for 12~24 h.

7. A halogen-free flame-retardant polyamide 6 composite material, characterized in that, The product comprises, by weight: 70-91 parts of polyamide 6 resin, 8-20 parts of hybrid phosphorus flame retardant, 0.5-3 parts of antioxidant, and 0.5-7 parts of coupling agent; wherein the hybrid phosphorus flame retardant is any one of the hybrid phosphorus flame retardants described in claims 1-6.

8. The halogen-free flame-retardant polyamide 6 composite material according to claim 7, characterized in that, The antioxidant is at least one of 1098 and antioxidant 168; the coupling agent is at least one of KH550, KH560 and KH570.

9. The halogen-free flame-retardant polyamide 6 composite material according to claim 7, characterized in that, The halogen-free flame-retardant polyamide 6 composite material was prepared by the following method: Step 2.1 Mix the hybrid phosphorus flame retardant and antioxidant evenly to obtain the first premix; Step 2.2 Mix the first premix, coupling agent and polyamide 6 resin evenly to obtain the second premix; Step 2.3 The second premix is ​​added to an extruder for melt blending, extrusion granulation, and tableting to obtain the halogen-free flame-retardant polyamide 6 composite material.

10. The halogen-free flame-retardant polyamide 6 composite material according to claim 9, characterized in that, The extruder mentioned in step 2.3 is a twin-screw extruder. The heating temperature of the twin-screw extruder during extrusion granulation is controlled as follows: Zone 1: 180~200 ℃, Zone 2: 200~240 ℃, Zone 3: 220~260 ℃; the screw speed of the twin-screw extruder is 30~150 rpm. The tableting conditions described in step 2.3 are 200~270 ℃, 3~25 MPa, and holding pressure for 3~20 min.

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