CN115418102B

CN115418102B - high-GWIT high-CTI halogen-free flame-retardant PA66 material and preparation method thereof

Info

Publication number: CN115418102B
Application number: CN202211170983.4A
Authority: CN
Inventors: 张文证; 李静
Original assignee: Suzhou Kingchen Plastic Technology Co ltd
Current assignee: Suzhou Kingchen Plastic Technology Co ltd
Priority date: 2022-09-24
Filing date: 2022-09-24
Publication date: 2023-10-20
Anticipated expiration: 2042-09-24
Also published as: CN115418102A

Abstract

The application relates to the field of plastics, in particular to a halogen-free flame-retardant PA66 material with high GWIT and CTI and a preparation method thereof, wherein the halogen-free flame-retardant PA66 material with high GWIT and CTI is prepared from the following raw materials in parts by weight: the composite material is prepared from the following raw materials in parts by weight: 70-80 parts of PA66 resin, 20-30 parts of flame retardant, 0.3-0.7 part of EBS, 0.1-0.3 part of calcium stearate, 0.3-0.5 part of zinc stearate and 0.1-0.5 part of antioxidant; the flame retardant is expandable graphite/modified vermiculite. According to the application, the modified vermiculite and the expandable graphite are compounded to form the expandable graphite/modified vermiculite as the flame retardant, so that the flame retardance and mechanical properties of the PA66 material are improved, and meanwhile, the influence of the flame retardant on CTI is reduced, so that the product has high GWIT and high CTI at the same time.

Description

high-GWIT high-CTI halogen-free flame-retardant PA66 material and preparation method thereof

Technical Field

The application relates to the technical field of plastics, in particular to a halogen-free flame-retardant PA66 material with high GWIT and high CTI and a preparation method thereof.

Background

PA66 (nylon 66) is one of the engineering plastics with more application at present, and has good mechanical strength, wear resistance, corrosion resistance and molding processability, thus being widely applied to the fields of household appliances, electric appliances, new energy automobile chargers, charging guns, battery related control systems and the like.

However, the polar oxygen index of PA66 is only about 22%, so that the phenomenon of molten drops is particularly easy to occur when the PA66 is burnt by heating, and other combustibles are ignited. Current flame retardant products of PA66 can be broadly divided into two families, halogen-containing flame retardant and halogen-free flame retardant. The halogen flame retardant is mainly a bromine-antimony compound flame retardant, but the halogen flame retardant is toxic and not suitable for use and popularization; the halogen-free flame retardance mainly comprises red phosphorus flame retardance, diethyl aluminum phosphinate flame retardance and nitrogen flame retardance, and the red phosphorus flame retardance is limited in use due to the color problem, and the diethyl aluminum phosphinate flame retardance is difficult to popularize due to the cost problem. The nitrogen flame retardation can have side effects on the CTI of the product, so that the CTI of the product is reduced.

In summary, the above flame retardant system cannot meet certain electronic products with very high requirements on GWIT and CTI, and limits the use and development of the electronic products.

Disclosure of Invention

In order to reduce the influence of flame retardant in the PA66 material on the CTI of the product and meet the requirements of the product on high GWIT and CTI, the application provides a halogen-free flame-retardant PA66 material with high GWIT and high CTI and a preparation method thereof.

In a first aspect, the application provides a halogen-free flame-retardant PA66 material with high GWIT and high CTI, which adopts the following technical scheme:

the halogen-free flame-retardant PA66 material with high GWIT and high CTI comprises the following raw materials in parts by weight: the composite material is prepared from the following raw materials in parts by weight: 70-80 parts of PA66 resin, 20-30 parts of flame retardant, 0.3-0.7 part of EBS, 0.1-0.3 part of calcium stearate, 0.3-0.5 part of zinc stearate and 0.1-0.5 part of antioxidant; the flame retardant is expandable graphite/modified vermiculite.

By adopting the technical scheme, the vermiculite has excellent high temperature resistance, and can still maintain the original structure and strength at a high temperature of 100 ℃. The high-content interlayer water and structural water content, the release of water vapor when heated, the flame retardation, the good high temperature resistance and the unique nano-layer structure indicate that the vermiculite is an excellent flame retardation material; the vermiculite is modified, so that a large number of uniform nano micropores are formed in the vermiculite layer, the vermiculite has good adsorptivity, and meanwhile, the compressive strength of the vermiculite is improved.

The expandable graphite has high temperature resistance, namely, when the expandable graphite is at high temperature, the expandable graphite rapidly expands, chokes flame, and meanwhile, the generated graphite expansion body material covers the surface of the base material, so that the contact between heat energy radiation and oxygen is isolated, acid radicals in the interlayer are released during expansion, and carbonization of the base material is promoted, so that the expandable graphite has a good flame retardant effect; meanwhile, the expandable graphite has rich pore structure, so that the expandable graphite has excellent adsorption performance.

The application combines the modified vermiculite and the expandable graphite which all have adsorption performance to form the expandable graphite/modified vermiculite, has good combination property and is beneficial to improving the synergistic flame retardant effect; the expandable graphite/modified vermiculite is used as a flame retardant to be added into the PA66 material, so that the flame retardance of the material is improved, the influence on CTI index is reduced, and the GWIT and CTI of the product are improved; does not contain toxic and harmful halogen components, and improves the use safety.

Preferably, the preparation method of the expandable graphite/modified vermiculite comprises the following steps:

crushing raw ore vermiculite, and screening to 100-300 meshes to obtain vermiculite powder; adding the vermiculite powder into an acidic solution, and heating and stirring to obtain a solid-liquid mixture; drying and grinding the solid obtained by filtering the solid-liquid mixture to obtain modified vermiculite powder;

the expandable graphite and the modified vermiculite powder are mixed according to the mass ratio of (2-20): 1, uniformly mixing to obtain a mixture, dispersing the mixture into deionized water, and carrying out ultrasonic treatment to obtain a pasty solution, wherein the mass ratio of the mixture to the deionized water is 1: (5-15); ball milling is carried out on the pasty solution to obtain suspension; and standing the suspension for 20-30h, removing the supernatant, and drying to constant weight to obtain the expandable graphite/modified vermiculite.

By adopting the technical scheme, the expandable graphite/modified vermiculite is prepared by taking the modified vermiculite and the expandable graphite as raw materials and adopting a mechanical ball milling method, the preparation method is simple to operate and mild in condition, and other toxic solvents are not required to be used; meanwhile, the prepared expandable graphite/modified vermiculite has excellent combination property and flame retardant property.

Preferably, the drying temperature is 80-100 ℃ and the drying time is 8-12h.

By adopting the technical scheme, the preparation efficiency can be improved by optimizing the temperature and time during drying, and the prepared expandable graphite/modified vermiculite can be ensured to have excellent flame retardant property.

Preferably, the average particle size of the expandable graphite/modified vermiculite is less than 1 μm and the thickness is 3-4nm.

By adopting the technical scheme, the size of the expandable graphite/modified vermiculite is controlled, so that the uniformity of the expandable graphite/modified vermiculite during mixing with other components in the PA66 can be improved, and the comprehensive performance of the PA66 material is further improved.

Preferably, the antioxidant is a mixture of antioxidant 1098 and antioxidant 168, and the mass ratio of the antioxidant to the antioxidant is (1-3): 1.

by adopting the technical scheme, the antioxidant 1098 is an excellent extraction-resistant low-volatility hindered phenol antioxidant, has good thermal stability and compatibility, and has the characteristics of no initial coloring, no pollution and extraction resistance; and when acting on PA66, the oxidation resistance and the thermal stability are particularly outstanding. The antioxidant 168 is used as an auxiliary antioxidant and is combined with an antioxidant 1098 phenolic antioxidant to have synergistic effect; and meanwhile, the antioxidant performance of the antioxidant 1098 is prolonged.

Preferably, the anti-dripping agent is also contained in an amount of 0.1 to 1 part by weight.

By adopting the technical scheme, the anti-dripping agent is fibrillated through the shearing action of the extrusion screw, a network structure is formed in the PA66 material, and the material is prevented from melting and dripping due to heat shrinkage when the material burns, so that the flame retardance of the PA66 material can be further improved.

Preferably, the anti-dripping agent is one of C60 fullerene, C70 fullerene and silicon carbide whisker.

By adopting the technical scheme, the fullerene is in a fourth crystal form of carbon elements subsequent to diamond, graphite and linear carbon; the silicon carbide whisker has excellent high temperature resistance and high strength. Compared with the traditional polytetrafluoroethylene anti-dripping agent, the anti-bacterial dripping agent prepared from the fullerene and the silicon carbide whisker has better effect than the traditional anti-dripping agent under the condition of the same content.

Preferably, the diameter D of the silicon carbide whisker is 0.5-1.5 mu m, and the length-diameter ratio L/D is (20-30): 1.

by adopting the technical scheme, on one hand, the silicon carbide whisker with proper length-diameter ratio can be fully dispersed in the PA66 material, and the excellent heat resistance of the whisker is exerted; meanwhile, due to the surface energy and electrostatic action of the silicon carbide whisker, the whisker can generate an agglomeration phenomenon, especially long whisker, and can be tangled, so that the self advantage of the silicon carbide whisker is reduced. On the other hand, the silicon carbide whisker is not suitable to be too fine, and especially when the service environment has an oxidizing atmosphere, the diameter of the silicon carbide whisker is properly increased, so that the oxidation resistance of the silicon carbide whisker is improved, and the service temperature of the PA66 material and the compatibility of the service environment are improved.

In a second aspect, the application provides a preparation method of a halogen-free flame-retardant PA66 material with high GWIT and CTI, which adopts the following technical scheme:

the preparation method of the halogen-free flame-retardant PA66 material with high GWIT and high CTI adopts the following technical scheme:

uniformly mixing the corresponding raw materials in parts by weight to obtain a mixture;

and carrying out melt extrusion and granulation on the mixture.

By adopting the technical scheme, the preparation method has simple process, does not need special equipment and is suitable for industrial production; meanwhile, the prepared PA66 material has excellent flame retardance and environmental protection advantages, is good in environmental compatibility, and is particularly beneficial to being applied to the fields of household appliance switches, electronic appliances, new energy automobile chargers, charging guns, battery related control systems and the like.

Preferably, a parallel double-screw extruder is adopted when the mixture is subjected to melt extrusion, the screw shape is double-thread, and the ratio L/D of the length L of the screw to the diameter D of the screw is 30-40.

By adopting the technical scheme, the lead of the double-thread screw is large, the material residence time during extrusion is short, the material degradation is reduced, and the production efficiency is improved; meanwhile, the plasticizing and dispersing capacity of the double-thread screw is stronger than that of the single-thread screw, so that the dispersing degree of the expandable graphite/modified vermiculite is improved. The too large length-diameter ratio of the screw can cause the heating time of the polymer to be prolonged, the expandable graphite/modified vermiculite to be degraded, and the manufacturing and the installation of the screw and the extruder are increased; too small length-diameter ratio of the screw is unfavorable for improving the generation efficiency due to poor dispersing capability.

In summary, the present application includes at least one of the following beneficial technical effects:

1. according to the application, the mechanical strength of the vermiculite is improved by modifying the vermiculite, and simultaneously the modified vermiculite with adsorptivity and the expandable graphite are combined to form the expandable graphite/modified vermiculite flame retardant, so that the flame retardance of the PA66 material is improved, the influence on CTI index is reduced, and the GWIT and CTI of the product are further improved;

2. the expandable graphite/modified vermiculite is prepared by adopting a mechanical ball milling method, the preparation method is simple, the conditions are mild, other toxic solvents are not required to be used, and the method has safety and environmental friendliness;

3. according to the application, C60 fullerene, C70 fullerene and silicon carbide whisker are added into the PA66 material as anti-dripping agents, a network structure is formed in the material during preparation, and the material is prevented from melting and dripping due to heat shrinkage during combustion, so that the flame retardant property of the PA66 material can be further improved.

Detailed Description

The present application will be described in further detail with reference to examples and examples.

Preparation example

Preparation example 1

The preparation example discloses a preparation method of expandable graphite/modified vermiculite, which comprises the following steps:

s10, selecting raw ore vermiculite with the particle size of 0.7-2mm, crushing by a ball mill, and screening to 100-300 meshes to obtain vermiculite powder, wherein the raw ore vermiculite is purchased from the company of Wanzhu mineral products of Ministry of life;

s20, adding 30g of the vermiculite powder into H ⁺ In 1000ml of acid solution with the concentration of 6mol/L, heating to 100 ℃, and rapidly stirring for 3 hours to obtain a solid-liquid mixture;

s30, filtering the obtained solid-liquid mixture to obtain vermiculite solid, repeatedly washing the vermiculite solid by using deionized water until the pH value of the washed deionized water is 7, drying the washed solid at 120 ℃ for 12 hours, and grinding to obtain modified vermiculite powder;

s40, uniformly mixing 2g of expandable graphite and 1g of the modified vermiculite powder, adding the mixture into 15ml of deionized water, and performing ultrasonic dispersion in a water bath at 60 ℃ for 30min to form a pasty solution; then placing the graphene into a ball milling tank containing zirconia, wherein the ball-material ratio is 30:1, and ball milling the graphene for 48 hours at 2500rpm/min by using a wet ball mill to obtain a suspension of graphene; standing for 20h, removing supernatant, placing in an oven at 80deg.C for 12h, and oven drying to constant weight to obtain black powder with average particle diameter smaller than 1 μm and thickness of 3-4nm, which is expandable graphite/modified vermiculite, wherein the expandable graphite is 80 mesh, expansion degree is 300, and is purchased from mineral product processing factory of LINGHW county.

Preparation example 2

This preparation differs from preparation 1 in that in S40, 10g of expandable graphite and 1g of the modified vermiculite powder described above are mixed uniformly and added to 110ml of deionized water.

Preparation example 3

This preparation differs from preparation 1 in that in S40, 20g of expandable graphite and 1g of the modified vermiculite powder described above are mixed uniformly and added to 315ml of deionized water.

Preparation example 4

The difference between this preparation example and preparation example 1 is that in S40, standing for 30 hours, removing supernatant, and drying in a 100 ℃ oven for 8 hours to constant weight, the black powder obtained is expandable graphite/modified vermiculite.

Examples

Example 1

The embodiment discloses a halogen-free flame retardant PA66 material with high GWIT and high CTI, which is prepared from 70Kg of PA66 resin, 20Kg of expandable graphite/modified vermiculite, 0.3Kg of EBS, 0.1Kg of calcium stearate, 0.3Kg of zinc stearate, 0.05Kg of antioxidant 1098 and 0.05Kg of antioxidant 168, wherein the expandable graphite/modified vermiculite is prepared in preparation example 1, and the PA66 resin is marked as EPR27, CAS of EBS: 110-30-5, calcium stearate CAS:1592-23-0, zinc stearate CAS:557-05-1, CAS of antioxidant 1098: 23128-74-7, CAS of antioxidant 168: 1570-04-4.

The embodiment also discloses a preparation method of the halogen-free flame-retardant PA66 material with high GWIT and high CTI, which comprises the following specific processes:

s1, weighing the components according to a formula, adding the components into a high-speed kneader, and uniformly mixing to obtain a mixture;

s2, adding the mixture into a parallel double-screw extruder, and granulating after melt extrusion to obtain a PA66 material; wherein the rotation speed of the twin-screw extruder is set to 400rpm/min, and the extrusion temperature of one to eight zones is as follows: 180 ℃/185 ℃/190 ℃/185 ℃/185 ℃/185 ℃/180 ℃/180 ℃; the temperature of the machine head is 200 ℃; vacuum degree is-0.04 Mpa; the extruder screw length L to diameter D ratio L/D was 30:1.

Examples 2 to 18

This example differs from example 1 in the amount of raw materials used for the PA66 material, as shown in table 2.

TABLE 1 proportions of raw materials of examples 1-18PA66 Material

Examples 19 to 21

This example is essentially the same as example 1, except that the expandable graphite/modified vermiculite was prepared using a different preparation, as shown in Table 2. TABLE 2 preparation examples of expandable graphite/modified vermiculite of examples 19-21

Example 22

This example is substantially the same as example 1, except that the C60 fullerene is replaced with a C70 fullerene, and the C60 fullerene and the C70 fullerene CAS:131159-39-2 from the Seamantadine biotechnology Co.

Example 23

This example is substantially the same as example 1 except that C60 fullerene is replaced with silicon carbide whisker having a diameter D of 0.5 to 1.5 μm, a length L of 10 to 45 μm, and an aspect ratio L/D of (20 to 30): 1, available from Shanghai lane field nanomaterials, inc.

Example 24

This example is essentially the same as the example except that the extruder screw length L to diameter D ratio L/D is 40:1.

Comparative example

Comparative example 1

This comparative example differs from example 1 mainly in that the expandable graphite/modified vermiculite is replaced with expandable graphite.

Comparative example 2

This comparative example differs from example 1 mainly in that the expandable graphite/modified vermiculite was replaced with modified vermiculite.

Comparative example 3

This comparative example differs from example 1 mainly in that the vermiculite is not modified in the process of preparing expandable graphite by replacing expandable graphite/modified vermiculite.

Comparative example 4

The main difference between this example and example 1 is that in the preparation method of expandable graphite by replacing expandable graphite/modified vermiculite with expandable graphite, in S40, 1g of expandable graphite and 1g of the modified vermiculite powder are mixed uniformly and added into 2ml of deionized water.

Comparative example 5

The main difference between this example and example 1 is that in the preparation method of expandable graphite by replacing expandable graphite/modified vermiculite with expandable graphite, in S40, 30g of expandable graphite and 1g of the modified vermiculite powder are mixed uniformly and added into 620ml of deionized water.

Comparative example 6

This example differs from example 1 mainly in that the C60 fullerene is replaced with a polytetrafluoroethylene-type anti-dripping agent, polytetrafluoroethylene-type dripping agent CAS:9002-84-0, commercially available from south sea silver of Buddha, inc.

Performance test the PA66 material obtained in examples 1-24 was used as test samples 1-24, and the PA66 material obtained in comparative examples 1-6 was used as control samples 1-6 in the same weight as the test samples. The test samples and the control samples were subjected to performance test, the results are shown in Table 3, and the specific test procedures are as follows:

flame resistance: 1.6mm thick bars were tested against the UL94 standard.

GWIT:1.6mm thick bars were tested with reference to IEC60695 standard.

CTI: samples were 2×2×4mm, tested according to IEC60112, with 0.1% anhydrous ammonium chloride as electrolyte and a calibration current of 1A.

Tensile strength: the test is performed with reference to ASTM D638.

Flexural strength: the test is performed with reference to ASTM D790.

Notched impact strength: the test is performed with reference to ASTM D256 standard.

Oxidation resistance: the color fastness was determined to be 2500kJ/m according to SAE J2527 by experiments with high gloss stains ² The color difference Δe was tested.

Table 3 table of performance test data

Referring to Table 3, in combination with examples 1-3, it can be seen that the mechanical properties of the samples are improved as the content of the PA66 resin is increased, but the flame retardance and GWIT of the PA66 material are reduced due to the poor flame retardance of the PA66 resin.

Referring to Table 3, in combination with examples 2, 4 and 5, it can be seen that the flame retardancy and GWIT of the samples are increasing with the continued addition of expandable graphite/modified vermiculite in the PA66 material. The strength of the vermiculite is improved after the vermiculite is modified, and simultaneously the expandable/modified vermiculite formed by combining the modified vermiculite with adsorption force and the expanded graphene has excellent flame retardant property, so that the flame retardant property of the PA66 material is improved.

Referring to Table 3, in combination with examples 4, 6 and 7, it can be seen that adding an appropriate amount of EBS to the PA66 material can improve the overall performance of the test sample. The EBS is added into the PA66 as a dispersing agent, so that the dispersibility and stability of each component can be promoted, the mixing property of the mixture is better, and the mechanical property, flame retardance, GWIT and CTI of the sample are improved.

Referring to Table 3, in combination with examples 6 and 8-11, it can be seen that the addition of appropriate amounts of calcium stearate and zinc stearate to the PA66 material resulted in samples with good mechanical properties and flame retardancy. The calcium stearate and the calcium stearate are added into the PA66 material as the lubricant, have the effects of smoothness and processing, improve the processability of the PA66 material during extrusion molding, enable the PA66 material to have better free radical recombination resistance, and have promotion effect on the color stabilization and corrosion resistance of the PA66 material.

Referring to Table 3, in combination with examples 10, 12-15, it can be seen that adding appropriate amounts of antioxidant 1098 and antioxidant 168 to the PA66 material increases the oxidation resistance of the test sample, especially when the mass ratio of antioxidant 1098 to antioxidant 168 is 2: in the case of 1 (example 12), the oxidation resistance of the sample is better than that of the antioxidant 1098 and the antioxidant 168 in a mass ratio of 1:1 or 3:1; with the increasing of the content of the antioxidant, the oxidation resistance of the sample is also improved. The antioxidant is added into the plastic resin, so that the thermal oxidation reaction speed of the plastic macromolecules is inhibited or reduced, the thermal and oxygen degradation processes of the plastic comb are delayed, the heat-resistant function of the plastic resin can be obviously improved, the antioxidant 1098 is used as a main antioxidant, the antioxidant 1689 is used as an auxiliary antioxidant, and the two antioxidants are combined for use, so that a good synergistic effect is achieved.

Referring to Table 3, in combination with examples 14 and 16-18, it can be seen that adding an appropriate amount of C60 fullerene to PA66 can improve the flame retardancy of the test sample. The C60 fullerene is added into the PA66 as an anti-dripping agent, and after a network node is formed in the PA66 material, the material burns and is melted and dripped by placing the material under heat shrinkage, so that the flame retardant effect of the sample can be further improved.

Referring to Table 3, in combination with examples 1 and 19-20 and comparative examples 4 and 5, it can be seen that when preparing expandable graphite/modified vermiculite, the mass ratio of modified expandable graphite to modified vermiculite and the mass ratio of the mixture formed of the two to deionized water are improved within a proper range, and the flame retardancy, GWIT and CTI of the obtained samples are more excellent.

Referring to table 3, in combination with examples 1, 21 and 24, it can be seen that the obtained samples still have excellent overall properties by changing the process conditions in the preparation of expandable graphite/modified vermiculite or the process parameters in the preparation of PA66 material within the appropriate ranges.

Referring to table 3, in combination with examples 1, 22 and 23 and comparative example 6, it can be seen that when C60 fullerene is replaced with C70 fullerene or silicon carbide whisker, the samples are excellent in flame retardancy, GWIT and CTI; however, when C60 fullerene is replaced with a conventional polytetrafluoroethylene anti-dripping agent, the flame retardant effect of the sample is significantly reduced.

Referring to Table 3, in combination with comparative examples 1 to 3 of example 1, it can be seen that modifying vermiculite can improve the strength and adsorptivity of vermiculite, thereby improving the binding property of expanded graphite with modified vermiculite and the mechanical strength of the obtained flame retardant expanded graphite/modified vermiculite, and further improving the flame retardance and mechanical effect of PA66 material. Meanwhile, the modified vermiculite or the expanded graphite is independently used as a flame retardant to be added into the PA66 material, so that the comprehensive performance of the obtained sample is reduced more, and particularly the flame retardant performance, GWIT and CTI are outstanding.

The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.

Claims

1. A halogen-free flame-retardant PA66 material with high GWIT and high CTI is characterized in that: the composite material is prepared from the following raw materials in parts by weight: 70-80 parts of PA66 resin, 20-30 parts of flame retardant, 0.3-0.7 part of EBS, 0.1-0.3 part of calcium stearate, 0.3-0.5 part of zinc stearate, 0.1-0.5 part of antioxidant and optionally 0.1-1 part of anti-dripping agent;

the flame retardant is expandable graphite/modified vermiculite;

the preparation method of the expandable graphite/modified vermiculite comprises the following steps:

the expandable graphite and the modified vermiculite powder are mixed according to the mass ratio of (2-20): 1, uniformly mixing to obtain a mixture, dispersing the mixture into deionized water, and carrying out ultrasonic treatment to obtain a pasty solution, wherein the mass ratio of the mixture to the deionized water is 1: (5-15); ball milling is carried out on the pasty solution to obtain suspension; standing the suspension for 20-30h, removing supernatant, and drying to constant weight to obtain expandable graphite/modified vermiculite;

the anti-dripping agent is one of C60 fullerene, C70 fullerene and silicon carbide whisker.

2. The high GWIT high CTI halogen-free flame retardant PA66 material according to claim 1, characterized in that: the drying temperature is 80-100 ℃ and the drying time is 8-12h.

3. The high GWIT high CTI halogen-free flame retardant PA66 material according to claim 1, characterized in that: the average grain diameter of the expandable graphite/modified vermiculite is smaller than 1 mu m, and the thickness is 3-4nm.

4. The high GWIT high CTI halogen-free flame retardant PA66 material according to claim 1, characterized in that: the antioxidant is a mixture of an antioxidant 1098 and an antioxidant 168, and the mass ratio of the antioxidant to the antioxidant is (1-3): 1.

5. the high GWIT high CTI halogen-free flame retardant PA66 material according to claim 1, characterized in that: the diameter D of the silicon carbide whisker is 0.5-1.5 mu m, and the length-diameter ratio L/D is (20-30): 1.

6. the method for preparing the halogen-free flame retardant PA66 material with high GWIT and high CTI in any one of claims 1 to 5, which is characterized in that:

and carrying out melt extrusion and granulation on the mixture.

7. The method for preparing the halogen-free flame-retardant PA66 material with high GWIT and CTI as set forth in claim 6, wherein the method comprises the steps of: the mixture is melt extruded by adopting a parallel double-screw extruder, the screw is in a double-screw thread shape, and the ratio L/D of the length L of the screw to the diameter D of the screw is (30-40): 1.