High-strength flame-retardant EPE pearl wool composite material and preparation method thereof

Abstract

The invention belongs to the technical field of foaming materials, and particularly relates to a high-strength flame-retardant EPE pearl wool composite material and a preparation method and application thereof. A conductive filler and a flame-retardant filler are added into a formula of the EPE pearl wool composite material, the flame-retardant filler is selected from chemically modified phytic acid, and the phytic acid with high phosphorus content is chemically modified by an epoxy compound, so that the compatibility with an LDPE (Low-Density Polyethylene) matrix is improved, a hydrocarbyl side chain structure can be better embedded into a polyethylene molecular chain, and the flame-retardant property of the EPE pearl wool composite material is improved. Under the action of an initiator, a cross-linking reaction is performed to form a net-shaped structure, so that the shore hardness and tensile strength of the EPE pearl wool composite material are improved while the antistatic and flame-retardant effects are improved. According to the optimized scheme, a reaction system of phytic acid, TGIC and a monofunctional epoxy monomer is used, a triazine ring is introduced into a cross-linked network through chemical reaction, and the mechanical property and the flame retardant effect of the EPE pearl wool are further improved through phosphorus-nitrogen cooperation.

Description

Technical Field

[0001] This application belongs to the field of foamed materials technology, and specifically relates to a high-strength flame-retardant EPE pearl cotton composite material, its preparation method and application. Background Technology

[0002] Low-density polyethylene (LDPE) boasts advantages such as low crystallinity, low softening point, high insulation, good water resistance, chemical corrosion resistance, and acid and alkali resistance. Its wide availability, low price, and ease of processing make it widely used in applications such as insulated cables, thermal insulation, and flame retardancy. When used as packaging material, LDPE is typically a non-crosslinked porous foam structure material produced through physical foaming, also known as polyethylene foam (EPE) or pearl cotton, containing uniformly distributed independent air bubbles. Compared to unfoamed LDPE, EPE offers advantages such as light weight, thermal insulation, sound insulation, and good impact resistance, and is widely used in sports, chemical, construction, packaging, biomaterials, aerospace, and automotive manufacturing industries.

[0003] However, EPE is prone to static electricity generation during transportation. In certain situations, this static electricity can dissipate or generate sparks. Static sparks and static discharge can damage the internal components of micro-precision instruments, ignite flammable materials, and cause explosions. LDPE, on the other hand, has high insulation but lacks conductivity, and its chemical structure is purely hydrocarbon, thus lacking flame retardancy. Therefore, flame retardants and antistatic agents need to be added to EPE formulations to prevent static electricity generated by friction during use, which could lead to fires or explosions, and to improve the flame retardant properties of EPE itself. This also avoids affecting the foaming effect and mechanical properties of EPE. Antistatic and flame-retardant modified EPE can be used in aerospace, precision instrument packaging, and electronic sensors, protecting instruments from static electricity damage and reducing safety hazards such as fires. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application adds conductive fillers and flame-retardant fillers to the EPE formulation. The flame-retardant filler is selected from chemically modified phytic acid. The high-phosphorus phytic acid is chemically modified by epoxy compounds, thereby improving its compatibility with the LDPE matrix. Its hydrocarbon side chain structure can be better embedded in the polyethylene molecular chain and cross-linked under the action of an initiator to form a network structure. This not only improves the antistatic and flame-retardant effects but also increases the Shore hardness and tensile strength of the EPE pearl cotton.

[0005] To achieve the above technical objectives, the technical solution adopted in this application is as follows: Firstly, an EPE pearl cotton composite material, the raw materials of which include: polyethylene resin, epoxy-modified phytic acid, conductive filler, initiator, main foaming agent, auxiliary foaming agent and antioxidant.

[0006] The polyethylene resin includes one or more of the following: low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and metallocene linear low-density polyethylene (mLLDPE). Preferably, the polyethylene resin comprises a combination of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE). The epoxy-modified phytic acid is a phytic acid derivative with a hydrocarbon side chain obtained by ring-opening reaction of epoxy groups with P-OH in phytic acid. The total molar amount of epoxy groups in the epoxy compound is lower than the total molar amount of P-OH in phytic acid. Preferably, the epoxy-modified phytic acid is obtained by reacting a nitrogen-containing heterocyclic epoxy compound and a hydrocarbon compound containing at least one epoxy group with phytic acid, wherein the total molar amount of epoxy groups in the nitrogen-containing heterocyclic epoxy compound and the hydrocarbon compound containing at least one epoxy group is lower than the total molar amount of P-OH in phytic acid. More preferably, the nitrogen-containing heterocyclic epoxy compound is selected from triglycidyl isocyanurate; Preferably, the epoxy group containing at least one epoxy group is selected from any one of alkylphenol glycidyl ether, alkyl glycidyl ether, or cyclic alkyl epoxide; The general structural formula of the hydrocarbon-based phenol glycidyl ether is as follows: R1 is selected from hydrocarbon groups with 1 to 20 carbon atoms; Preferably, R1 is selected from hydrocarbon groups having 1 to 6 carbon atoms; More preferably, the alkylphenol glycidyl ether is selected from either p-methylphenol glycidyl ether or p-vinylphenol glycidyl ether; The general structural formula of the hydrocarbon-based glycidyl ether is as follows: R2 is selected from hydrocarbon groups with 1 to 20 carbon atoms; Preferably, R2 is selected from hydrocarbon groups with 1 to 6 carbon atoms; Preferably, the hydrocarbon glycidyl ether is selected from allyl glycidyl ether; The general structural formula of the cyclic hydrocarbon epoxy group is as follows: The value of n ranges from 3 to 5, and R3 is selected from hydrocarbon groups with 1 to 20 carbon atoms. Preferably, R3 is selected from hydrocarbon groups having 1 to 6 carbon atoms; More preferably, the cycloalkyl epoxide is selected from 1,2-epoxy-4-vinylcyclohexane; Preferably, the specific steps of modifying phytic acid with the epoxy compound include: adding a hydrocarbon compound containing at least one epoxy group and phytic acid into a reaction vessel and reacting at 80-130°C; Further optimization involves conducting the reaction at 100-120℃; Preferably, quaternary ammonium compounds are used as catalysts to catalyze the reaction of epoxide compounds with phytic acid; More preferably, the specific steps of modifying phytic acid with the epoxy compound include: adding the nitrogen-containing heterocyclic epoxy compound and phytic acid into a reaction vessel and reacting them at 80-130°C; subsequently adding a hydrocarbon compound containing at least one epoxy group and phytic acid into the reaction vessel and reacting them at 80-130°C.

[0007] The conductive filler is selected from one or more combinations of conductive carbon black, conductive graphite, graphene and carbon nanotubes. Preferably, the conductive filler is selected from graphene or carbon nanotubes; Preferably, the conductive filler is selected from an aqueous dispersion of graphene or carbon nanotubes; The initiator is selected from one or more combinations of dicumyl peroxide, 2,5-di-tert-butylperoxide-2,5-methylhexane, and tert-butylperoxide benzoate; The main foaming agent is selected from azo compounds; Preferably, the azo compound is selected from azodicarbonamide; The foaming agent is selected from a combination of stearic acid and zinc oxide; The antioxidant is selected from one or a combination of two of hindered phenolic antioxidants and phosphite antioxidants; Preferably, the hindered phenolic antioxidant is selected from antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]); Preferably, the phosphite antioxidant is selected from antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite); Furthermore, by weight, the EPE pearl cotton composite material comprises the following raw material formulation in parts by weight: 90-110 parts by weight of polyethylene resin, 5-15 parts by weight of epoxy-modified phytic acid, 1-5 parts by weight of conductive filler, 0.5-2 parts by weight of initiator, 5-15 parts by weight of main foaming agent, 1-5 parts by weight of auxiliary foaming agent, and 1-5 parts by weight of antioxidant.

[0008] Secondly, the preparation method of the above-mentioned EPE pearl cotton composite material includes three steps: filler blending, open milling compounding, and molding foaming. The filler blending includes: mechanically pre-dispersing an aqueous dispersion of conductive filler, adding phytic acid modified with an epoxy compound, and then mechanically dispersing it again to obtain a paste-like filler; Preferably, the dynamic viscosity of the paste filler at room temperature is 40,000-70,000 cps; Preferably, the conductive filler content in the aqueous dispersion of the conductive filler is 5-20 wt%. Preferably, the amount of epoxy-modified phytic acid used is 30-70 wt% of the aqueous dispersion of the conductive filler; The open mill compounding process includes: mixing polyethylene resin, antioxidant and foaming agent in the prescribed amounts and adding them to an open mill; after the polyethylene resin melts, adding paste filler, main foaming agent and initiator to it and mixing to obtain a raw material mixture; The molding foaming process includes: placing the raw material mixture into a hot press for molding foaming, with the temperature set at 160-220℃ and the pressure at 5-15MPa.

[0009] Thirdly, the above-mentioned EPE pearl cotton composite material has applications in aerospace, precision instruments, electronic sensor packaging, as well as in heat insulation and sound insulation.

[0010] Fourthly, a paste-like filler is prepared by mechanical dispersion of an aqueous dispersion of a conductive filler and phytic acid modified with an epoxy compound; The amount of phytic acid modified with the epoxy compound is 30-70 wt% of the weight of the aqueous dispersion. The dynamic viscosity of the paste filler at room temperature is 40,000-70,000 cps; Preferably, the conductive filler is an aqueous dispersion of graphene or carbon nanotubes with a solid content of 5-20 wt%.

[0011] The beneficial effects of the technical solutions proposed above in this application are: 1. Using DCP crosslinking agent to crosslink LDPE, LLDPE and epoxy-modified phytic acid, phosphorus-rich phytic acid is introduced into the crosslinking network of polyolefin, thereby significantly improving the tensile strength and flame retardant properties of EPE pearl cotton composite material. 2. The design utilizes an epoxy compound to initiate a ring-opening reaction with the P-OH group in phytic acid, thereby introducing hydrocarbon side chains into the phytic acid, which improves its compatibility with polyethylene. Under the action of an initiator, it cross-links with the LDPE matrix to form a network structure, improving both antistatic and flame-retardant properties while also enhancing the Shore hardness and tensile strength of EPE pearl cotton. The optimized scheme uses a reaction system of phytic acid + TGIC + monofunctional epoxy monomers to introduce triazine rings into the cross-linking network through a chemical reaction, further improving the mechanical properties and flame-retardant effect of the EPE pearl cotton composite material through phosphorus-nitrogen synergy. 3. For the treatment of conductive fillers, an aqueous dispersion of the conductive filler is selected to avoid the loss of the conductive filler during the mixing process due to its light weight. Based on the aqueous dispersion, the phytic acid modified by epoxy compounds is easily soluble in water and is added as a thickener to the aqueous dispersion of the conductive filler, thereby obtaining a paste-like filler that is convenient to be blended with LDPE and LLDPE granules. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 The ATR-FTIR spectra of phytic acid modified with epoxy compounds prepared in Examples 1-2 and Examples 5-6 are shown, where (a) is the vibrational peak of POP, (b) is the vibrational peak of POC and CO, (c) is the vibrational peak of P=O, (d) is the vibrational peak of benzene ring and unsaturated vinyl group, and (e) is the vibrational peak of carbonyl C=O. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention. It should be noted that the terminology used herein is only for describing specific implementations and is not intended to limit the exemplary implementations of the present invention.

[0015] Unless otherwise specified, the experimental conditions in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0016] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings: The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0017] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0018] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0019] In this application, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions containing the listed features.

[0020] Example 1 316.8 g (0.24 mol) of phytic acid and 23.8 g (0.08 mol) of triglycidyl isocyanurate were added to a reaction vessel. The mixture was heated to 110 °C under continuous nitrogen purging and stirring. Then, 1.5 g of tetrabutylammonium bromide was added as a catalyst, and the reaction was carried out at 110-120 °C for 2 hours. The reaction was considered complete after the epoxy group-labeled absorption peak at 910-920 cm⁻¹ disappeared, as monitored by infrared spectroscopy. Then, 118.2 g (0.72 mol) of p-methylphenol glycidyl ether was added, and the reaction was carried out at 110-120 °C for 3 hours. The reaction was also stopped after the epoxy group-labeled absorption peak at 910-920 cm⁻¹ disappeared, as monitored by infrared spectroscopy. The temperature was then lowered.

[0021] Preparation of paste filler: 100 parts by weight of aqueous graphene dispersion NC-GP-02 (Jiaxing Nake New Materials, graphene content 10wt%) was pre-dispersed for 10 minutes using a high-speed disperser at 1000 rpm. At this speed, 45 parts by weight of the product prepared above were slowly added. After the addition was completed, the speed was increased to 1500 rpm and the dispersion was continued for 30 minutes to obtain paste filler. The rotational viscosity was tested at room temperature and found to be 58000 cps.

[0022] Example 2 4-Vinylphenyl glycidyl ether was used instead of p-methylphenol glycidyl ether, and the amount of 4-vinylphenyl glycidyl ether was 126.9 g (0.72 mol). The rest was the same as in Example 1.

[0023] Example 3 Allyl glycidyl ether was used instead of p-methylphenol glycidyl ether, and the amount of allyl glycidyl ether was 82.2 g (0.72 mol). The rest was the same as in Example 1.

[0024] Example 4 1,2-Epoxy-4-vinylcyclohexane was used instead of p-methylphenol glycidyl ether, and the amount of 1,2-epoxy-4-vinylcyclohexane was 89.4 g (0.72 mol). The rest was the same as in Example 1.

[0025] Example 5 316.8 g (0.24 mol) of phytic acid and 113.5 g (0.96 mol) of p-methylphenol glycidyl ether were added to the reaction vessel. The mixture was heated to 110 °C under continuous nitrogen protection and stirring. Then, 1.5 g of tetrabutylammonium bromide was added as a catalyst. The reaction was carried out at 110-120 °C for 4 hours. After the epoxy group marker absorption peak at 910-920 cm⁻¹ disappeared, the temperature was lowered and the reaction was stopped by infrared spectroscopy.

[0026] Preparation steps of paste filler: 100 parts by weight of aqueous graphene dispersion NC-GP-02 (Jiaxing Nake New Materials, graphene content 10wt%) were pre-dispersed for 10 minutes using a high-speed disperser at 1000 rpm. 60 parts by weight of the product prepared above were slowly added at this speed. After the addition was complete, the speed was increased to 1500 rpm and dispersion was continued for 30 minutes to obtain paste filler. The rotational viscosity was tested at room temperature and found to be 47000 cps.

[0027] Example 6 4-Vinylphenyl glycidyl ether was used instead of p-methylphenol glycidyl ether, and the amount of 4-vinylphenyl glycidyl ether was 169.2 g (0.96 mol), and the rest was the same as in Example 5.

[0028] Example 7 Allyl glycidyl ether was used instead of p-methylphenol glycidyl ether, and the amount of allyl glycidyl ether was 109.6 g (0.96 mol), and the rest was the same as in Example 5.

[0029] Example 8 1,2-Epoxy-4-vinylcyclohexane was used instead of p-methylphenol glycidyl ether, and the amount of 1,2-epoxy-4-vinylcyclohexane was 119.2 g (0.72 mol), the rest was the same as in Example 5.

[0030] Example 9 The raw materials of EPE pearl cotton composite material, by weight, include: 90 parts by weight of low-density polyethylene 2420K (CNOOC Shell, melt index 4 g / 10 min @ 190℃ / 2.16 kg), 10 parts by weight of linear low-density polyethylene (Shanghai SECCO, with 1-butene as the comonomer, melt index 2.5 g / 10 min @ 190℃ / 2.16 kg), 12 parts by weight of azodicarbonamide, 2 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 1 part by weight of dicumyl peroxide, 30 parts by weight of the paste filler prepared in Example 1, 2 parts by weight of antioxidant 1010, and 1 part by weight of antioxidant 168.

[0031] The formulated amounts of LDPE granules, LLDPE granules, zinc oxide, stearic acid, antioxidants 1010 and 168 are mixed and then added to a two-roll mill at a temperature of 120°C. After milling for 5 minutes, the LDPE and LLDPE granules soften and adhere to the rolls, melt, and form sheets on a rubber mixing mill. Then, the formulated amounts of paste filler, azodicarbonamide, and dicumyl peroxide are added and the mixture is blended for another 10 minutes. Finally, compression molding and foaming are performed.

[0032] The flatbed hot press is heated to 170℃. The mixed raw materials are removed from the open mill and placed into the flatbed hot press for molding and foaming. The temperature is set at 170℃, the pressure at 8 MPa, and the foaming time at 15 minutes. This process yields foamed EPE pearl cotton.

[0033] Example 10 The raw materials for the EPE pearl cotton composite material include 30 parts by weight of the paste filler prepared in Example 2, and the remaining raw material formulations are the same as those in Example 9, and the preparation steps are the same as those in Example 9.

[0034] Example 11 The raw materials for the EPE pearl cotton composite material include 30 parts by weight of the paste filler prepared in Example 3, and the remaining raw material formulations are the same as those in Example 9, and the preparation steps are the same as those in Example 9.

[0035] Example 12 The raw materials for the EPE pearl cotton composite material include 30 parts by weight of the paste filler prepared in Example 4, and the remaining raw material formulations are the same as those in Example 9, and the preparation steps are the same as those in Example 9.

[0036] Example 13 The raw materials for the EPE pearl cotton composite material include 32 parts by weight of the paste filler prepared in Example 5, and the remaining raw material formulations are the same as those in Example 9, and the preparation steps are the same as those in Example 9.

[0037] Example 14 The raw materials for the EPE pearl cotton composite material include 32 parts by weight of the paste filler prepared in Example 6, and the remaining raw material formulations are the same as those in Example 9, and the preparation steps are the same as those in Example 9.

[0038] Example 15 The raw materials for the EPE pearl cotton composite material include 32 parts by weight of the paste filler prepared in Example 7, and the remaining raw material formulations are the same as those in Example 9, and the preparation steps are the same as those in Example 9.

[0039] Example 16 The raw materials for the EPE pearl cotton composite material include 32 parts by weight of the paste filler prepared in Example 8, and the remaining raw material formulations are the same as those in Example 9, and the preparation steps are the same as those in Example 9.

[0040] Comparative Example 1 Preparation steps of paste filler: 100 parts by weight of aqueous graphene dispersion NC-GP-02 (Jiaxing Nake New Materials, graphene content 10wt%) was pre-dispersed for 10 minutes using a high-speed disperser at 1000 rpm. At this speed, 60 parts by weight of phytic acid (which had not undergone chemical modification) were slowly added. After the addition was completed, the speed was increased to 1500 rpm and the dispersion was continued for 30 minutes to obtain paste filler. The rotational viscosity at room temperature was 37000 cps.

[0041] Comparative Example 2 The raw materials for the EPE pearl cotton composite material include 32 parts by weight of the paste filler prepared in Comparative Example 1, and the formulation of the remaining raw materials is the same as that in Example 9, and the preparation steps are the same as those in Example 9.

[0042] Performance testing Infrared spectral analysis of epoxy monomer-modified phytic acid: ATR-FTIR was used to test the spectra of epoxy-modified phytic acid prepared in Examples 1-2 and Examples 5-6, and the results are listed below. Figure 1 middle.

[0043] Shore hardness is determined by cutting EPE pearl cotton samples into 50×50 mm square samples and testing the surface hardness of the samples using a Shore C hardness tester in accordance with standard ISO 2439-1980.

[0044] Tensile strength was tested according to the standard specimen in GB / T 9641-1988, with a tensile rate of 500 mm / min.

[0045] For surface resistance testing, refer to the method in ASTM D257-2014 and use a four-probe sheet resistance tester to test the surface resistance of the adhesive layer of the antistatic tape.

[0046] The Limiting Oxygen Index (LOI) was tested according to the method in standard ASTM D 2863-2013.

[0047] Combustion test: Refer to the method of horizontal combustion test of foamed materials in standard ASTM D3801. The sample size is a cube of 150×50×10mm. The flame retardancy rating of EPE pearl cotton is evaluated by observing the afterflame time, dripping, and whether it ignites the cotton pad below, using HF-1 or HF-2.

[0048] The above tests were performed on the EPE pearl cotton composite material samples prepared by compression foaming in Examples 9-16 and Comparative Example 2, and the results are summarized in Table 1.

[0049] right Figure 1 Spectral analysis shows that (a) is the vibrational peak of POP, (b) is the vibrational peak of POC and C-O, (c) is the vibrational peak of P=O, (d) is the vibrational peak of benzene ring and unsaturated vinyl group, and (e) is the vibrational peak of carbonyl C=O. This confirms that the TGIC structure was introduced into phytic acid in Examples 1-2, in which the carbonyl vibrational peak appeared. Examples 5-6 did not introduce the TGIC structure and had no carbonyl structure.

[0050] In Examples 1-8, phytic acid was first reacted with a compound containing at least one epoxy group to undergo a ring-opening reaction, and then mixed with an aqueous graphene dispersion to prepare a paste-like filler. The P-OH of phytic acid was not completely reacted off by the epoxy group, and it was water-soluble. Hydrogen bonds were formed between (P=O), P-OH and the C-OH formed by ring opening in the modified phytic acid. After dissolving in the aqueous graphene dispersion, it had a thickening effect, thereby increasing the viscosity of the dispersion and making it less likely to splash and lose graphene during subsequent feeding.

[0051] Table 1 Analysis of the data in Table 1 shows that the EPE pearl cotton in Examples 9-16, which used the paste fillers prepared in Examples 1-8, exhibits higher hardness, tensile strength, antistatic effect, and flame retardant effect. Comparative Example 2, which did not use epoxy monomers to modify phytic acid, showed poor compatibility between phytic acid and the LDPE matrix, affecting the hardness, tensile strength, and flame retardant effect of the EPE pearl cotton composite. From a mechanical property analysis perspective, using dicumyl peroxide (DCP) to initiate free radical crosslinking significantly improves the tensile strength of the EPE pearl cotton. In particular, the phytic acid modified with epoxy monomers shows better compatibility and interfacial bonding with the LDPE matrix, effectively reinforcing the material. The hydrocarbon side chain structure can be better embedded in the polyethylene molecular chain and, under the action of the DCP initiator, crosslinks with the LDPE matrix to form a network structure. Therefore, the EPE pearl cotton in Examples 9-16 has better mechanical properties than that in Comparative Example 2. In addition, the paste filler prepared using the reaction system of phytic acid + TGIC + monofunctional epoxy monomer (Examples 1-4) has a slightly better reinforcing effect than the paste filler prepared using phytic acid + monofunctional epoxy monomer (Examples 5-8). The possible reason is that TGIC introduces a three-dimensional cross-linked structure, which makes the filler itself more rigid.

[0052] Regarding antistatic effects, the EPE pearl cotton composites prepared in Examples 9-16 and Comparative Example 2 all exhibited good antistatic properties, with surface resistivity below 10^9. Examples 9, 10, 13, and 14, containing benzene ring-containing epoxy monomers (p-methylphenol glycidyl ether, 4-vinylphenyl glycidyl ether), showed relatively lower surface resistivity, possibly because the benzene ring structure may facilitate the dispersion of graphene sheets and promote the formation of a conductive network. In contrast, the EPE pearl cotton composites prepared using the paste fillers of Examples 3, 4, 7, and 8, which used aliphatic or alicyclic epoxy monomers, showed slightly higher surface resistivity, while Comparative Example 2, which did not use epoxy monomer modification, had an even higher surface resistivity.

[0053] Regarding the flame retardant effect, the LOI of Comparative Example 2, which did not undergo epoxy grafting modification of phytic acid, was only 22.7%, with a flame retardant rating of HF-2. The LOI of Examples 9-16, which were modified with phytic acid, was increased to over 25%, and the flame retardant rating reached HF-1, thus improving the flame retardant effect. Phytic acid itself has the chemical structure of inositol hexaphosphate (IP6), which can be used as a highly efficient char-forming agent and gas-phase flame retardant. However, it is highly polar and has poor compatibility with the LDPE matrix. After chemical modification and grafting of hydrocarbon groups, it is firmly bonded to the polymer system under the action of DCP initiator. During combustion, it can more effectively promote the char formation of the matrix, forming a dense and stable char layer that isolates heat and oxygen, thereby improving the flame retardant effect of EPE pearl cotton composite material. Among them, the paste filler prepared using the reaction system of phytic acid + TGIC + monofunctional epoxy monomer (Examples 1-4) showed a more significant improvement in flame retardancy. This is because TGIC contains a triazine ring, which itself acts as a nitrogen source and produces a phosphorus-nitrogen synergistic flame retardant effect with the phosphorus in phytic acid.

[0054] Finally, it should be noted that the above-described embodiments are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be pointed out that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Furthermore, it should be understood that after reading the above teachings of this application, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the scope of protection of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. An EPE (Expanded Polyethylene) pearl cotton composite material, characterized in that, The raw materials include: polyethylene resin, epoxy-modified phytic acid, conductive filler, initiator, main foaming agent, auxiliary foaming agent and antioxidant; The polyethylene resin includes one or more of the following: low-density polyethylene, linear low-density polyethylene, and metallocene linear low-density polyethylene; The epoxy-modified phytic acid is a phytic acid derivative with a hydrocarbon side chain obtained by ring-opening reaction of epoxy groups with P-OH in phytic acid. The total molar amount of epoxy groups in the epoxy compound is lower than the total molar amount of P-OH in phytic acid. The conductive filler is selected from one or more combinations of conductive carbon black, conductive graphite, graphene and carbon nanotubes. The initiator is selected from one or more combinations of dicumyl peroxide, 2,5-di-tert-butylperoxide-2,5-methylhexane, and tert-butylperoxide benzoate; The main foaming agent is selected from azo compounds; The foaming agent is selected from a combination of stearic acid and zinc oxide; The antioxidant is selected from one or a combination of two of hindered phenolic antioxidants and phosphite antioxidants.

2. The EPE pearl cotton composite material according to claim 1, characterized in that, The polyethylene resin includes a combination of low-density polyethylene and linear low-density polyethylene; And / or, the hindered phenolic antioxidant is selected from antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]); And / or, the phosphite antioxidant is selected from antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite); And / or, the epoxy-modified phytic acid is obtained by reacting a nitrogen-containing heterocyclic epoxy compound and a hydrocarbon compound containing at least one epoxy group with phytic acid, wherein the total molar amount of epoxy groups in the nitrogen-containing heterocyclic epoxy compound and the hydrocarbon compound containing at least one epoxy group is lower than the total molar amount of P-OH in phytic acid. And / or, the azo compound is selected from azodicarbonamide; And / or, the conductive filler is selected from graphene or carbon nanotubes.

3. The EPE pearl cotton composite material according to claim 1, characterized in that, The hydrocarbon compound containing at least one epoxy group is selected from any one of alkylphenol glycidyl ether, alkyl glycidyl ether, or cyclic alkyl epoxide. The general structural formula of the hydrocarbon-based phenol glycidyl ether is as follows: R1 is selected from hydrocarbon groups with 1 to 20 carbon atoms; The general structural formula of the hydrocarbon-based glycidyl ether is as follows: R2 is selected from hydrocarbon groups with 1 to 20 carbon atoms; The general structural formula of the cyclic hydrocarbon epoxy group is as follows: The value of n ranges from 3 to 5, and R3 is selected from hydrocarbon groups with 1 to 20 carbon atoms.

4. The EPE pearl cotton composite material according to claim 3, characterized in that, The alkylphenol glycidyl ether is selected from either p-methylphenol glycidyl ether or p-vinylphenol glycidyl ether; And / or, the hydrocarbon glycidyl ether is selected from allyl glycidyl ether; And / or, the cycloalkyl epoxide is selected from 1,2-epoxy-4-vinylcyclohexane.

5. The EPE pearl cotton composite material according to claim 1, characterized in that, The specific steps for modifying phytic acid with the epoxy compound include: adding a hydrocarbon compound containing at least one epoxy group and phytic acid into a reaction vessel and reacting at 80-130°C.

6. The EPE pearl cotton composite material according to claim 1, characterized in that, The specific steps for modifying phytic acid with the epoxy compound include: adding an epoxy compound containing a nitrogen heterocycle and phytic acid into a reaction vessel and reacting them at 80-130°C; subsequently adding a hydrocarbon compound containing at least one epoxy group and phytic acid into the reaction vessel and reacting them at 80-130°C.

7. The EPE pearl cotton composite material according to claim 1, characterized in that, By weight, EPE pearl cotton comprises the following raw material formula in parts by weight: 90-110 parts by weight of polyethylene resin, 5-15 parts by weight of epoxy-modified phytic acid, 1-5 parts by weight of conductive filler, 0.5-2 parts by weight of initiator, 5-15 parts by weight of main foaming agent, 1-5 parts by weight of auxiliary foaming agent, and 1-5 parts by weight of antioxidant.

8. A method for preparing the EPE pearl cotton composite material as described in any one of claims 1-7, characterized in that, The preparation method includes three steps: filler blending, open mill compounding, and compression molding foaming. The filler blending includes: mechanically pre-dispersing an aqueous dispersion of conductive filler, adding phytic acid modified with an epoxy compound, and then mechanically dispersing it again to obtain a paste-like filler; The open mill compounding process includes: mixing polyethylene resin, antioxidant and foaming agent in the prescribed amounts and adding them to an open mill; after the polyethylene resin melts, adding paste filler, main foaming agent and initiator to it and mixing to obtain a raw material mixture; The molding foaming process includes: placing the raw material mixture into a hot press for molding foaming, with the temperature set at 160-220℃ and the pressure at 5-15MPa.

9. The use of the EPE pearl cotton composite material as described in any one of claims 1-7 in aerospace, precision instrument, electronic sensor packaging, and thermal and sound insulation applications.

10. A paste-like filler, characterized in that, It is prepared by mechanical dispersion of an aqueous dispersion of conductive filler and phytic acid modified with an epoxy compound; The amount of phytic acid modified with the epoxy compound is 30-70 wt% of the weight of the aqueous dispersion. The paste-like filler has a dynamic viscosity of 40,000-70,000 cps at room temperature.

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