A thin-walled, low-explosion, highly resistant to humid heat, halogen-free, flame-retardant nylon composite material and its preparation method

Abstract

This application relates to the field of polymer materials technology, and in particular to an ultrathin-walled, low-exudation, high-damp-heat resistant, halogen-free flame-retardant nylon composite material and its preparation method. The composite material comprises 40-70 parts aliphatic nylon, 3-8 parts aromatic nylon, 13-20 parts halogen-free flame retardant, 2.5-5.0 parts nano-silicon-based synergistic charring agent, 15-35 parts glass fiber, 1-3 parts hydrolysis-resistant and precipitation-inhibiting stabilizer, 0.3-0.8 parts antioxidant, and 0.3-0.8 parts lubricant. The halogen-free flame retardant is a ternary compound of phosphinate:microencapsulated red phosphorus:melamine polyphosphate, and the hydrolysis-resistant and precipitation-inhibiting stabilizer is a zirconium carbide:vinylsiloxane compound. This composite material achieves UL94 V-0 rating with an ultrathin wall thickness of 0.4 mm, shows no exudation after 1000 hours of double 85 testing, and has a tensile retention rate of ≥86% after 1000 hours at 125℃, making it suitable for applications such as high-voltage connectors for new energy vehicles and charging piles.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and in particular to an ultrathin-walled, low-emission, highly resistant to humid heat, halogen-free, flame-retardant nylon composite material and its preparation method. Background Technology

[0002] Nylon (polyamide, PA) is widely used in electronics, automotive, and other fields due to its excellent mechanical properties, heat resistance, and processability. With the development of new energy industries and micro-precision electronic devices, higher flame retardant requirements have been placed on nylon materials, especially the requirement that the material can stably achieve UL94 V-0 rating with an ultra-thin wall thickness of 0.4mm, while also possessing properties such as low exudation and resistance to damp heat aging.

[0003] However, the following prominent problems exist in the existing technology: Flame retardancy challenges in ultra-thin walls: Conventional halogen-free flame-retardant nylon struggles to achieve a UL94 V-0 rating at a thickness of 0.4 mm. In ultra-thin components, the material burns rapidly and drips excessively, failing to meet the safety requirements of miniature precision electronics and high-voltage connectors.

[0004] Flame retardant precipitation and mold fouling: Halogen-free flame retardants (especially phosphorus-based flame retardants) are prone to migrating to the surface of products during processing and use, causing blooming, poor appearance, and reduced insulation performance. At the same time, severe mold fouling occurs during production, requiring frequent machine shutdowns for mold cleaning, significantly reducing production efficiency and increasing production costs.

[0005] Poor resistance to humid heat aging: Nylon is hygroscopic and is prone to hydrolysis in high temperature and high humidity environments, which leads to rapid degradation of mechanical properties and flame retardant properties, making it difficult to meet the long-term reliability requirements of new energy vehicles, charging piles, high voltage connectors, etc.

[0006] To overcome the aforementioned shortcomings, those skilled in the art have attempted various modification methods, such as adding anti-hydrolysis agents, using compound flame retardants, and introducing nano-synergists. However, existing solutions often struggle to simultaneously achieve flame retardancy, low exudation, and resistance to damp heat aging in ultra-thin-walled structures. For example, Chinese invention patent CN118813040A improves flame retardancy and anti-exudation properties by adding silica-synergistic aluminum diethylphosphinate (ADP), but it does not solve the V-0 flame retardancy problem for 0.4mm ultra-thin-walled structures. Chinese invention patent CN118290934A uses siloxane to coat aluminum diethylphosphinate and adds DOPO derivatives to improve flame retardancy and anti-exudation properties, but it also does not address the 0.4mm V-0 and specific stabilizer system.

[0007] Therefore, developing a nylon composite material that can stably achieve V-0 flame retardancy, zero flame retardant release, and excellent resistance to damp heat aging with an ultra-thin wall thickness of 0.4 mm remains a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0008] This application aims to provide an ultra-thin-walled, low-exudation, high-damp heat-resistant halogen-free flame-retardant nylon composite material and its preparation method, to solve the problems in existing technologies where nylon composite materials are difficult to achieve a V-0 flame retardant rating with an ultra-thin wall thickness of 0.4 mm, flame retardant easily exudes leading to mold fouling and performance degradation, and has insufficient resistance to damp heat aging. This halogen-free flame-retardant nylon composite material is particularly suitable for applications with stringent requirements for flame retardancy, resistance to damp heat aging, and low exudation, such as ultra-thin-walled (0.4 mm) electronic and electrical components, high-voltage connectors for new energy vehicles, and charging piles.

[0009] This application provides an ultrathin-walled, low-exudation, high-moisture-heat-resistant, halogen-free flame-retardant nylon composite material, comprising the following components in parts by weight: 40-70 parts of aliphatic nylon; 3-8 parts of aromatic nylon; 13-20 parts of nano-coated phosphorus-nitrogen ternary flame retardant; 2.5–5.0 parts of nano-silicon synergistic char-forming agent; 15-35 parts glass fiber; 1-3 parts of hydrolysis-resistant and precipitation-inhibiting stabilizer; Antioxidant 0.3–0.8 parts; Lubricant 0.3–0.8 parts; The nano-coated phosphorus-nitrogen ternary flame retardant is a ternary compound of phosphonate, microencapsulated red phosphorus, and melamine polyphosphate, with a weight ratio of phosphonate:microencapsulated red phosphorus:melamine polyphosphate = 4:3:3; the nano-coated phosphorus-nitrogen ternary flame retardant has a nano-coated structure with an average particle size ≤500 nm; the hydrolysis-resistant and precipitation-inhibiting stabilizer is a compound of zirconium carbide and vinylsiloxane, with a weight ratio of zirconium carbide to vinylsiloxane of 2:1.

[0010] In some embodiments, the aliphatic nylon is nylon 66 and / or nylon 6 with a viscosity of 2.0 to 2.4 dL / g; the aromatic nylon is poly(m-phenylene adipamide) with a viscosity of 2.2 dL / g.

[0011] In some embodiments, the nano-silicon synergistic carbonizing agent is selected from one or more of organically modified nano-montmorillonite, nano-silica, and polysiloxane.

[0012] In some embodiments, the glass fiber is either alkali-free short fiber or continuous fiber.

[0013] In some embodiments, the antioxidant is mainly a hindered phenolic antioxidant, and is supplemented by one or more of phosphites, thiols and thiodipropionates.

[0014] In some embodiments, the lubricant is selected from one or more of pentaerythritol ester, butyl stearate, ethylene bis-stearamide, or polyolefin wax.

[0015] This application also provides a method for preparing the ultrathin-walled, low-precipitation, highly resistant to humid heat, halogen-free, flame-retardant nylon composite material as described above, which includes the following steps: (1) Raw material pretreatment: Aliphatic nylon and aromatic nylon resins were vacuum dried at 80-105℃ for 4-6 hours, and the moisture content was controlled to be ≤0.1%; (2) High-speed premixing: Except for glass fiber and nano-coated phosphorus and nitrogen ternary flame retardant, all other components are put into a high-speed mixer according to the proportion and mixed for 1 to 5 minutes to obtain a premix; (3) Melt extrusion: The premixed material is added to the main feed port of the twin-screw extruder, and the nano-coated phosphorus and nitrogen ternary flame retardant and glass fiber are added through the side feed port. High vacuum degassing is carried out during the melt blending process, with a vacuum degree ≥0.08 MPa. The melt is obtained by melt extrusion. (4) Molding: The melt is water-cooled, stretched, air-dried, granulated and dried to obtain the halogen-free flame-retardant nylon composite material granules.

[0016] In some embodiments, the twin-screw extruder has a screw length-to-diameter ratio of 40 to 44:1, a melt extrusion temperature of 200 to 275°C, and a screw speed of 350 to 700 rpm.

[0017] Compared with the prior art, this application has the following beneficial effects: Achieving 0.4mm ultrathin wall V-0 flame retardancy: Through a specific ratio of phosphines, microencapsulated red phosphorus, and melamine polyphosphate ternary nano-coating compound, combined with nano-silicon synergistic charring agents, a dense char layer is formed during combustion, effectively inhibiting dripping and flame spread, enabling the material to stably pass the UL94 V-0 test with an ultimate oxygen index of over 30% at an ultrathin wall thickness of 0.4mm.

[0018] Zero flame retardant precipitation and low mold fouling: An innovative hydrolysis-resistant and precipitation-inhibiting stabilizer is used, formulated with zirconium carbide and vinylsiloxane in a 2:1 ratio. This stabilizer anchors the flame retardant through chemical bonding, inhibiting its migration to the product surface. This results in no surface precipitation or blooming after 1000 hours of dual 85 testing (85℃ / 85% RH), significantly reducing mold fouling and improving production efficiency and product appearance quality.

[0019] Excellent resistance to damp heat aging: The synergistic effect of zirconium carbide and vinylsiloxane not only inhibits precipitation but also improves the material's resistance to hydrolysis under high temperature and high humidity conditions. After 125℃ and 1000 hours of heat aging test, the tensile strength retention rate is ≥86%; after 1000 hours of double 85 test, there is no significant decrease in mechanical properties and flame retardant properties, meeting the long-term reliability requirements of new energy vehicles and high-voltage connectors.

[0020] Excellent processing performance: The side-feeding and high-vacuum degassing process reduces the heat history loss of flame retardants and the hydrolytic damage of moisture to the resin. The resulting granules can be directly used for injection molding. The process window is wide and suitable for industrial production. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] To verify the effectiveness of the proposed solution, the following embodiments and comparative examples are presented. Raw material information for the examples and comparative examples: Aliphatic nylon: PA66 (viscosity 2.4 dL / g), specifically EPR24; Aromatic nylon: MXD6 (viscosity 2.2 dL / g), specifically Beijing Anaiji M30; Phosphite: Aluminum diethylphosphite (ADP), industrial grade, specifically Orip ADP-30P; Microencapsulated red phosphorus: industrial grade, specifically Qingyuan Yicheng FRP-980N; Melamine polyphosphate (MPP): Industrial grade, specifically Sichuan Fine Chemical MPP-C; The nano-coated phosphorus-nitrogen ternary flame retardant is a ternary compound of phosphinate, microcapsule red phosphorus, and melamine polyphosphate, with a particle size ≤500nm and a weight ratio of phosphinate:microcapsule red phosphorus:melamine polyphosphate = 4:3:3. The specific preparation method of the nano-coated phosphorus-nitrogen ternary flame retardant is as follows: ADP, microcapsule red phosphorus, and melamine polyphosphate are added to a high-speed mixer and mixed at a speed of 450 r / min. Nano-silicon synergistic charring agent: Evonik Degussa AEROSIL R972; Glass fiber: Alkali-free chopped glass fiber; The hydrolysis-resistant and precipitation-inhibiting stabilizer is a compound of zirconium carbide and vinylsiloxane, with a weight ratio of zirconium carbide to vinylsiloxane of 2:1; vinylsiloxane: vinyltriethoxysilane; Antioxidants: Hindered phenolic antioxidant 1098 (N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine) and phosphite antioxidant 9228 (3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane) were compounded in a weight ratio of 1:2.

[0023] Lubricant: Pentaerythritol stearate (PETS).

[0024] The formulation information for the examples and comparative examples is shown in Table 1-2: Table 1. Formulation composition (parts by weight) of Examples 1-3

[0025] Table 2. Formulation composition (parts by weight) of Comparative Examples 1-3

[0026] Preparation method (the following steps were used in Examples 1-3 and Comparative Examples 1-3): (1) PA66 and MXD6 were vacuum dried at 90℃ for 5 hours, with a moisture content ≤0.1%; (2) Except for glass fiber and flame retardant, mix the above components in a high-speed mixer for 3 minutes according to the proportions in Table 1 and Table 2 to obtain premix; (3) The premixed material is added to the twin-screw extruder through the main feed port, and the flame retardant and glass fiber are added through the side feed ports respectively. The temperature of each zone of the extruder is set as follows: Zone 1 200℃, Zone 2 275℃, Zone 3 275℃, Zone 4 275℃, Zone 5 275℃, Zone 6 265℃, Zone 7 260℃, Zone 8 260℃, Zone 9 275℃, and the die head 275℃. The screw length-to-diameter ratio is 40:1, the screw speed is 600 rpm, and the vacuum degree of the vacuum exhaust port is ≥0.08 MPa. (4) The melt is water-cooled, stretched, air-dried, pelletized, and dried to obtain nylon composite material granules.

[0027] Performance testing methods: Tensile strength: Tested according to ISO 527-2 standard, specimen type 1A, tensile speed 5 mm / min.

[0028] Tensile retention rate: After aging in hot air at 125℃ for 1000 h, the tensile strength was tested and the percentage of the initial value was calculated.

[0029] Flame retardancy: Tested according to UL94 standard for specimens with thicknesses of 0.4 mm and 1.6 mm.

[0030] Limiting Oxygen Index (LOI): Tested according to ISO 4589-2 standard.

[0031] Surface precipitation / mold fouling: After 1000 h of double 85 test (85℃, 85% RH), observe whether there is white precipitation on the sample surface; at the same time, count the fouling on the mold surface after 200 consecutive injection moldings (no precipitation / slight / obvious / severe).

[0032] The test results are shown in Table 3-4 below: Table 3 Performance test results of Examples 1-3

[0033] Table 4 Performance test results of Comparative Examples 1-3

[0034] Results analysis: As shown in Examples 1-3, within the formulation range of this application, the materials can achieve a flame retardant rating of 0.4 mm V-0 and exhibit excellent resistance to damp heat aging (tensile strength retention ≥86%). No exudates were observed after the double 85 test, and mold fouling was low. With increasing glass fiber content, tensile strength significantly improved, but good performance could still be maintained with appropriate adjustments to the ratio of flame retardant and stabilizer.

[0035] Comparative Example 1 did not add nano-silicon synergistic char-forming agent and hydrolysis-resistant anti-precipitation stabilizer, and only used phosphonate flame retardant. The flame retardancy of 0.4 mm was only V-2, and the tensile retention rate and anti-precipitation performance were poor (severe precipitation).

[0036] Comparative Example 2 did not add a hydrolysis-resistant and precipitation-inhibiting stabilizer. Although a synergistic charring agent was used, the flame retardancy of 0.4 mm was still V-2, the tensile retention rate was only 50%, and there was obvious precipitation.

[0037] Comparative Example 3 added stabilizers and synergistic charring agents, but the flame retardant was a single phosphonate (without using a ternary compound). The flame retardancy at 0.4 mm was still V-2, and the tensile retention rate was only 68%, which was significantly worse than the example.

[0038] The above comparison fully demonstrates that the synergistic effect of the ternary compound flame retardant and the zirconium carbide / vinylsiloxane stabilizer, as well as the combination of the nano-silicon synergistic charring agent, are the key technical features for achieving 0.4 mm V-0 flame retardancy, low precipitation, and high resistance to humid heat aging in this application.

[0039] In addition, comparative examples 4-6 are provided: To verify the irreplaceability of zirconium carbide / vinylsiloxane stabilizers, this application also provides the following comparative examples (the formulations are basically the same as in Example 2, only the stabilizer composition or ratio is changed): Comparative Example 4: The stabilizer was replaced with vinylsiloxane only (in the same amount as in Example 2). The results showed that there was slight precipitation on the surface after the double 85 test, and the flame retardancy was only V-1 for 0.4 mm.

[0040] Comparative Example 5: Replacing zirconium carbide with an equal amount of silicon carbide resulted in significant precipitation (fouling grade "significant"), with a flame retardancy of only V-1 for 0.4 mm.

[0041] Comparative Example 6: The ratio of zirconium carbide to vinylsiloxane was changed to 1:1. The results showed that the precipitation and performance retention were worse than those of Example 2 (slight precipitation, tensile retention decreased to 78%).

[0042] In summary, the test results for comparison ratios 4 to 6 are as follows: Table 5 Performance test results of Comparative Examples 4-6

[0043] In the table, "-" indicates that it has not been tested.

[0044] The above supplementary comparative examples further demonstrate the uniqueness and unpredictability of the 2:1 blend of zirconium carbide and vinylsiloxane.

[0045] Additionally, the preferred range is explained as follows: The amount of aliphatic nylon (PA66) should be 40 to 70 parts. If it is less than 40 parts, the mechanical properties of the material will be insufficient. If it is more than 70 parts, the proportion of MXD6 will be relatively reduced, which will have a limited impact on the crystallinity of the material, but will reduce the fluidity and affect the ultra-thin wall injection molding effect.

[0046] The amount of aromatic nylon (MXD6) used is 3 to 8 parts. If it is less than 3 parts, it will have a limited effect on the crystallinity of the material, but the fluidity will decrease and affect the ultra-thin wall injection molding effect. If it is more than 8 parts, the material cost will increase.

[0047] The dosage of nano-coated phosphorus-nitrogen ternary flame retardant is 13-20 parts. Less than 13 parts will result in insufficient flame retardant effect, while more than 20 parts will lead to a decrease in mechanical properties and an increased risk of exudation. A ternary compound ratio of 4:3:3 is preferred, and deviations from this ratio will result in a decrease in the 0.4 mm flame retardant rating.

[0048] The dosage of hydrolysis-resistant and anti-precipitation stabilizer is 1-3 parts. Less than 1 part results in insufficient anchoring effect, while more than 3 parts increases cost and may affect resin compatibility. The optimal ratio of zirconium carbide to vinylsiloxane is 2:1.

[0049] The dosage of nano-silicon synergistic charring agent is 2.5 to 5 parts. If it is less than 2.5 parts, the charring will be insufficient, and if it is more than 5 parts, it will have a negative impact on mechanical properties.

[0050] Special notes on the preparation process: Maintaining a moisture content of ≤0.1% during raw material pretreatment is crucial to ensuring that nylon resin does not degrade.

[0051] Adding flame retardants and glass fibers using a side-feeding method can reduce the heat residence time of the flame retardant in the extruder, preventing premature decomposition; at the same time, it is beneficial to retain the length of the glass fibers, improving the reinforcing effect.

[0052] High-vacuum exhaust (≥0.08 MPa) can effectively remove small molecule volatiles and moisture, further reducing the risk of precipitation.

[0053] In summary, the industrial applicability of this application is as follows: The halogen-free flame-retardant nylon composite material prepared in this application can be used in electronic and electrical components requiring ultra-thin walls, high flame retardancy, low exudation, and resistance to damp heat aging, such as high-voltage connectors for new energy vehicles, charging piles, miniature circuit breakers, relay housings, and electronic transformer frames. The material can be directly processed through injection molding, which is simple and suitable for large-scale production.

[0054] It should be noted that: In summary, the specific parameters or some commonly used reagents or raw materials in the above embodiments are specific or preferred embodiments under the concept of this application, and not limitations thereof; those skilled in the art can make adaptive adjustments within the concept and protection scope of this application.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A thin-walled, low-extraction, highly resistant to damp heat, halogen-free, flame-retardant nylon composite material, characterized in that, Includes the following components in parts by weight: 40-70 parts of aliphatic nylon; 3-8 parts of aromatic nylon; 13-20 parts of nano-coated phosphorus-nitrogen ternary flame retardant; 2.5–5.0 parts of nano-silicon synergistic char-forming agent; 15-35 parts glass fiber; 1-3 parts of hydrolysis-resistant and precipitation-inhibiting stabilizer; Antioxidant 0.3–0.8 parts; Lubricant 0.3–0.8 parts; The nano-coated phosphorus-nitrogen ternary flame retardant is a ternary compound of phosphonate, microencapsulated red phosphorus, and melamine polyphosphate, with a weight ratio of phosphonate:microencapsulated red phosphorus:melamine polyphosphate = 4:3:3; the nano-coated phosphorus-nitrogen ternary flame retardant has a nano-coated structure with an average particle size ≤500 nm. The hydrolysis-resistant and precipitation-inhibiting stabilizer is a compound of zirconium carbide and vinylsiloxane, with a weight ratio of zirconium carbide to vinylsiloxane of 2:

1.

2. The ultra-thin-walled, low-emission, high-humidity-heat-resistant, halogen-free flame-retardant nylon composite material according to claim 1, characterized in that, The aliphatic nylon is nylon 66 and / or nylon 6 with a viscosity of 2.0 to 2.4 dL / g; The aromatic nylon is poly(m-phenylene adipamide) with a viscosity of 2.2 dL / g.

3. The ultra-thin-walled, low-emission, high-humidity-heat-resistant, halogen-free flame-retardant nylon composite material according to claim 1, characterized in that, The nano-silicon synergistic carbonizing agent is selected from one or more of organically modified nano-montmorillonite, nano-silica, and polysiloxane.

4. The ultra-thin-walled, low-emission, high-humidity-heat-resistant, halogen-free flame-retardant nylon composite material according to claim 1, characterized in that, The glass fiber is either alkali-free short fiber or continuous fiber.

5. The ultra-thin-walled, low-emission, high-humidity-heat-resistant, halogen-free flame-retardant nylon composite material according to claim 1, characterized in that, The antioxidant is mainly hindered phenolic antioxidant, and auxiliary antioxidant is one or more of phosphites, thiols and thiodipropionates.

6. The ultra-thin-walled, low-emission, high-humidity-heat-resistant, halogen-free flame-retardant nylon composite material according to claim 1, characterized in that, The lubricant is selected from one or more of pentaerythritol ester, butyl stearate, ethylene bis-stearamide, or polyolefin wax.

7. A method for preparing an ultrathin-walled, low-precipitation, highly resistant to damp heat, halogen-free, flame-retardant nylon composite material as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Raw material pretreatment: Aliphatic nylon and aromatic nylon resins were vacuum dried at 80–105°C for 4–6 hours, controlling the moisture content to ≤0.1%; High-speed premixing: Except for glass fiber and nano-coated phosphorus and nitrogen ternary flame retardant, all other components are put into a high-speed mixer according to the formula and mixed for 1 to 5 minutes to obtain a premix. Melt extrusion: The premixed material is added to the main feed port of the twin-screw extruder, and the nano-coated phosphorus and nitrogen ternary flame retardant and glass fiber are added through the side feed port. High vacuum degassing is carried out during the melt blending process, with a vacuum degree ≥0.08 MPa. The melt is obtained by melt extrusion. Molding: The melt is water-cooled, stretched, air-dried, pelletized, and dried to obtain the halogen-free flame-retardant nylon composite material granules.

8. The preparation method according to claim 7, characterized in that, The twin-screw extruder has a screw length-to-diameter ratio of 40 to 44:1, a melt extrusion temperature of 200 to 275°C, and a screw speed of 350 to 700 rpm.

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