A creep-resistant ultra-high molecular weight polyethylene fiber and preparation method thereof

Abstract

The present invention discloses a creep-resistant ultra-high molecular weight polyethylene fiber and a preparation method thereof, which comprises the following steps: polyethylene powder, solvent, antioxidant and biochar powder are mixed and stirred to form a spinning solution; the spinning solution is placed in a container for spinning to form jelly yarns; the jelly yarns in the container are allowed to stand and pre-extracted; the extract after pre-extraction is extracted, dried and subjected to multi-stage hot stretching treatment; and creep-resistant ultra-high molecular weight polyethylene fiber is obtained. The method adds biochar powder to the spinning solution formula for filling and modification, utilizes the exchange between the extractant and the spinning solvent to introduce the coupling agent and the thermal initiator into the fiber network structure, and induces internal cross-linking during hot stretching to improve the creep resistance of the fiber.

Description

Technical Field

[0001] The invention relates to the field of polymer technology, and in particular to a creep-resistant ultra-high molecular weight polyethylene fiber and a preparation method thereof. Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber, also known as high-strength high-modulus polyethylene fiber, is a high-performance fiber developed in 1970. It is white in appearance and is considered one of the three high-performance fibers that can be industrialized at present, along with aromatic fiber and carbon fiber. Due to its excellent properties such as high strength, high modulus, low density, good impact resistance and chemical corrosion resistance, ultra-high molecular weight polyethylene fiber is widely used in lightweight bulletproof helmets, soft bulletproof clothing and other fields.

[0003] Under conventional production formulas, since ultra-high molecular weight polyethylene fiber molecules have no side chains and have a symmetrical methylene structure, there are no hydrogen bonds between fiber molecules and the van der Waals force only acts as a dispersion force, resulting in very small intermolecular forces in ultra-high molecular weight polyethylene fibers, and intermolecular slippage is prone to occur, causing creep. Summary of the invention

[0004] One purpose of the present scheme is to provide a method for preparing creep-resistant ultra-high molecular weight polyethylene fibers, which method comprises adding biochar powder to the spinning solution formula for filling and modification, utilizing the exchange effect between the extractant and the spinning solvent to introduce the coupling agent and the thermal initiator into the fiber network structure, and inducing internal cross-linking during thermal stretching to improve the creep resistance of the fiber.

[0005] Another object of this scheme is to provide ultra-high molecular weight polyethylene fiber prepared by the above method.

[0006] To achieve the above objectives, this plan is as follows:

[0007] A method for preparing creep-resistant ultra-high molecular weight polyethylene fiber, the method comprising the following steps:

[0008] Polyethylene (PE) powder, solvent, antioxidant and biochar powder are mixed and stirred to form a spinning solution;

[0009] Placing the spinning solution in a container for spinning to form jelly filaments;

[0010] The jelly strands in the container are allowed to stand and undergo pre-extraction treatment;

[0011] The extract after pre-extraction is subjected to extraction drying and multi-stage heat drawing treatment;

[0012] Creep-resistant ultra-high molecular weight polyethylene fibers are obtained.

[0013] In this preparation scheme, biochar powder is added to the spinning solution formula for filling and modification, so that an interaction force is generated between the biochar powder and the ultra-high molecular weight polyethylene fiber molecular chain, thereby improving the heat resistance and creep resistance of the ultra-high molecular weight polyethylene;

[0014] Preferably, the biochar powder includes one or more of corn straw charcoal powder, wheat straw charcoal powder and rice straw charcoal powder.

[0015] Preferably, the mass ratio of the polyethylene (PE) powder to the biochar powder is 70-97:3-30.

[0016] When the amount of biochar powder added exceeds 30% of the total weight of polyethylene powder and biochar powder, the mechanical properties of the fiber will be significantly reduced. The reason may be that the biochar powder may agglomerate in the filler. The agglomeration phenomenon will cause the biochar powder to be unevenly dispersed in the matrix, causing the stress of the fiber to concentrate at the agglomeration point during the test, which is prone to fiber breakage.

[0017] Preferably, a thermal initiator and a coupling agent are added to the container during pre-extraction.

[0018] Since the time that the jelly yarn stays in the extractant and the extraction ratio determine the efficiency of the extraction exchange, if the conventional jelly yarn drawing process is used, the extraction efficiency may be insufficient in the extraction section, which in turn affects the degree of crosslinking. In order to reduce the pressure in the extraction section, a pre-extraction process is added to the process flow, and the coupling agent and thermal initiator are introduced into the fiber network structure by utilizing the exchange effect between the extractant and the spinning solvent, which triggers internal crosslinking during thermal drawing to improve the creep resistance of the fiber.

[0019] Preferably, the thermal initiator is any one of tert-butyl peroxy-2-ethylhexanoate (TBPO), benzoic acid ester (TBPB), and benzoyl peroxide (BPO); the amount of the thermal initiator is 0.5-5% of the amount of ultra-high molecular weight polyethylene.

[0020] The free radicals generated by the thermal decomposition of tert-butyl peroxy-2-ethylhexanoate capture hydrogen atoms on the ultra-high molecular weight polyethylene molecular chain to form ultra-high molecular weight polyethylene molecular free radicals.

[0021] Preferably, the coupling agent is a silane coupling agent, and the silane coupling agent is any one of γ-(methacryloyloxy)propyltrimethoxysilane (KH570), vinyltrimethoxysilane (KH171), γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) and titanate coupling agent (NDZ-201); the amount of the coupling agent is 10 to 25% of the amount of ultra-high molecular weight polyethylene.

[0022] Ultra-high molecular weight polyethylene molecules undergo a grafting reaction with γ-(methacryloyloxy)propyltrimethoxysilane. After γ-(methacryloyloxy)propyltrimethoxysilane is grafted onto the ultra-high molecular weight polyethylene molecular chain, a hydrolysis reaction occurs to form silanols. A dehydration condensation reaction occurs between the two silanols, thereby forming a network cross-linked structure, thereby achieving chemical cross-linking modification of the ultra-high molecular weight polyethylene molecules.

[0023] Preferably, the mass ratio of the thermal initiator and coupling agent added into the container to the ultra-high molecular weight polyethylene in the container is 1-3:5-8:45-55.

[0024] Preferably, the pre-extraction is performed by an ultrasonic generator, and the pre-extraction time is 2 to 5 hours.

[0025] Pre-extraction is to add the prepared extraction liquid into the static frozen gel thread container, and perform vibration extraction by connecting the ultrasonic generator and the transducer interface. The general time is 2-5 hours. During this process, the extraction liquid will be recovered and replenished at a certain speed to ensure the efficiency of pre-extraction.

[0026] In a second aspect, a creep-resistant ultra-high molecular weight polyethylene fiber is provided, which is prepared by the above method.

[0027] The beneficial effects of this program are as follows:

[0028] The presence of biochar powder will limit the slip movement and reorientation arrangement between molecular chains and at the ends. At the same time, during the thermal drawing process, the thermal initiator is thermally decomposed and produces free radicals. The free radicals further capture the hydrogen atoms in the ultra-high molecular weight polyethylene molecules and produce new polyethylene free radicals. The polyethylene free radicals undergo a grafting reaction with silane to form a network structure under the action of environmental moisture. The network structure also greatly limits the slip movement and reorientation arrangement between molecular chains and at the ends. The combination of the two effectively improves the creep resistance of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the implementation of the present scheme, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present scheme. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 The preparation flow chart of this method. DETAILED DESCRIPTION

[0031] The implementation method of this solution is further described in detail below. Obviously, the described embodiments are only part of the embodiments of this solution, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments and features in the embodiments of this solution can be combined with each other without conflict.

[0032] The preparation process of ultra-high molecular weight polyethylene fiber includes the following process steps: preparing spinning solution - adding antioxidant - extrusion spinning by twin-screw extruder - quenching in cold water bath to form frozen collagen filaments - extracting solvent - drying - hot stretching to obtain ultra-high molecular weight polyethylene fiber.

[0033] The inventors of the present application have found that after high-temperature carbonization, the surface of biochar powder is non-polar and is similarly compatible with the ultra-high molecular weight polyethylene (UHMWPE) polymer matrix which is also non-polar. Therefore, biochar powder with a high filling amount can be evenly dispersed in the polymer matrix, and the biochar powder particles have a multi-porous structure and have a good interface bonding effect with UHMWPE. With the increase of the amount of biochar powder added, the restriction of biochar powder on the slip movement and reorientation arrangement between molecular chains and ends when the external load acts on the composite material will also increase accordingly. In particular, the biochar powder distributed in the amorphous region of the matrix contributes to the improvement of the modulus and creep resistance of the amorphous region of polyethylene, which effectively improves the creep resistance of the composite material. At the same time, biochar powder has high thermal stability, plays a thermal barrier role inside polyethylene, and improves the heat resistance of the fiber.

[0034] The inventors also found that the thermal initiator decomposes when heated and produces free radicals, which further capture hydrogen atoms in the ultra-high molecular weight polyethylene molecules and produce new polyethylene free radicals. The polyethylene free radicals undergo a grafting reaction with silane to form a three-dimensional network structure under the action of environmental moisture. The three-dimensional network structure greatly limits the slip movement and reorientation arrangement between molecular chains and at the ends, effectively improving the creep resistance of the composite material.

[0035] like Figure 1 As shown, a method for preparing creep-resistant ultra-high molecular weight polyethylene fiber comprises the following steps:

[0036] Polyethylene (PE) powder, solvent, antioxidant and biochar powder are mixed and stirred to form a spinning solution;

[0037] Placing the spinning solution in a container for spinning to form jelly filaments;

[0038] The jelly strands in the container are allowed to stand and undergo pre-extraction treatment;

[0039] The extract after pre-extraction is subjected to extraction drying and multi-stage heat drawing treatment;

[0040] Creep-resistant ultra-high molecular weight polyethylene fibers are obtained.

[0041] In this preparation scheme, biochar powder is added to the spinning solution formula for filling and modification, so that an interaction force is generated between the biochar powder and the ultra-high molecular weight polyethylene fiber molecular chain, thereby improving the heat resistance and creep resistance of the ultra-high molecular weight polyethylene;

[0042] In one embodiment, the biochar powder includes corn stover charcoal powder.

[0043] In one embodiment, the mass ratio of polyethylene (PE) powder to the biochar powder is 85-97:15-30.

[0044] When the amount of biochar powder added exceeds 30% of the total weight of polyethylene powder and biochar powder, the mechanical properties of the fiber will be significantly reduced. The reason may be that the biochar powder may agglomerate in the filler. The agglomeration phenomenon will cause the biochar powder to be unevenly dispersed in the matrix, causing the stress of the fiber to concentrate at the agglomeration point during the test, which is prone to fiber breakage.

[0045] In one embodiment, the thermal initiator and coupling agent are added to the vessel during pre-extraction.

[0046] Since the time that the jelly yarn stays in the extractant and the extraction ratio determine the efficiency of the extraction exchange, if the conventional jelly yarn drawing process is used, the extraction efficiency may be insufficient in the extraction section, which in turn affects the degree of crosslinking. In order to reduce the pressure in the extraction section, a pre-extraction process is added to the process flow, and the coupling agent and thermal initiator are introduced into the fiber network structure by utilizing the exchange effect between the extractant and the spinning solvent, which triggers internal crosslinking during thermal drawing to improve the creep resistance of the fiber.

[0047] In one embodiment, the thermal initiator is any one of tert-butyl peroxy-2-ethylhexanoate (TBPO), benzoic acid ester (TBPB), and benzoyl peroxide (BPO); the amount of the thermal initiator is 0.5-5% of the amount of ultra-high molecular weight polyethylene.

[0048] In one embodiment, the coupling agent is a silane coupling agent, and the silane coupling agent is any one of γ-(methacryloyloxy)propyltrimethoxysilane (KH570), vinyltrimethoxysilane (KH171), γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) and titanate coupling agent (NDZ-201); the amount of the coupling agent is 10 to 25% of the amount of ultra-high molecular weight polyethylene.

[0049] In one embodiment, the thermal initiator added to the container is tert-butyl peroxide-2-ethylhexanoate, and the coupling agent is γ-(methacryloyloxy)propyltrimethoxysilane; the ratio of tert-butyl peroxide-2-ethylhexanoate, γ-(methacryloyloxy)propyltrimethoxysilane and ultra-high molecular weight polyethylene is 1:6:50, and the crosslinking degree of the formed ultra-high molecular weight polyethylene fiber can reach 80%, and the creep resistance of the fiber is greatly improved.

[0050] In one embodiment, the pre-extraction is performed by an ultrasonic generator, and the pre-extraction time is 2 to 5 hours.

[0051] Pre-extraction is to add the prepared extraction liquid into the static frozen gel thread container, and perform vibration extraction by connecting the ultrasonic generator and the transducer interface. The general time is 2-5 hours. During this process, the extraction liquid will be recovered and replenished at a certain speed to ensure the efficiency of pre-extraction.

[0052] The present application also provides a creep-resistant ultra-high molecular weight polyethylene fiber, which is prepared by the above method.

[0053] The present application is described below through specific embodiments.

[0054] Example 1

[0055] Ultra-high molecular weight polyethylene fiber

[0056] The raw materials are: 8.5 parts of UHMWPE powder (molecular weight 4.2 million), 90 parts of mineral oil, 0.02 parts of antioxidant B225, and 1.5 parts of corn straw charcoal powder;

[0057] Preparation method:

[0058] (1) mixing and dissolving the various components of the above raw materials to form a UHMWPE spinning solution;

[0059] (2) using a spinning machine to perform gel spinning;

[0060] (3) adding 1.02 parts of γ-(methacryloyloxy)propyltrimethoxysilane and 0.17 parts of tert-butyl peroxy-2-ethylhexanoate to the extractant to prepare a mixed extract, and using the mixed extract to perform extraction and exchange to obtain primary fibers;

[0061] (4) drying the as-spun fiber in a drying oven and recovering part of the extract;

[0062] (5) 4-stage heat stretching, stretching temperature 110-155 degrees, total stretching ratio 30 times, and the result is obtained.

[0063] Example 2

[0064] Ultra-high molecular weight polyethylene fiber

[0065] The raw materials are: 9.5 parts of UHMWPE powder (molecular weight 4.2 million), 90 parts of mineral oil, 0.03 parts of antioxidant B225, and 0.5 parts of corn straw charcoal powder;

[0066] Preparation method:

[0067] (1) mixing and dissolving the various components of the above raw materials to form a UHMWPE spinning solution;

[0068] (2) using a spinning machine to perform gel spinning;

[0069] (3) adding 1.14 parts of γ-(methacryloyloxy)propyltrimethoxysilane and 0.19 parts of tert-butyl peroxy-2-ethylhexanoate to the extractant to prepare a mixed extract, and using the mixed extract to perform extraction and exchange to obtain primary fibers;

[0070] (4) drying the as-spun fiber in a drying oven and recovering part of the extract;

[0071] (5) 4-stage heat stretching, stretching temperature 110-155 degrees, total stretching ratio 30 times, and the result is obtained.

[0072] Example 3

[0073] Ultra-high molecular weight polyethylene fiber

[0074] The raw materials are: 9 parts of UHMWPE powder (molecular weight 4.2 million), 90 parts of mineral oil, 0.02 parts of antioxidant B225, and 1 part of corn straw charcoal powder;

[0075] Preparation method:

[0076] (1) mixing and dissolving the various components of the above raw materials to form a UHMWPE spinning solution;

[0077] (2) using a spinning machine to perform gel spinning;

[0078] (3) adding 1.08 parts of γ-(methacryloyloxy)propyltrimethoxysilane and 0.18 parts of tert-butyl peroxy-2-ethylhexanoate to the extractant to prepare a mixed extract, and using the mixed extract to perform extraction and exchange to obtain primary fibers;

[0079] (4) drying the as-spun fiber in a drying oven and recovering part of the extract;

[0080] (5) 4-stage heat stretching, stretching temperature 110-155 degrees, total stretching ratio 30 times, and the result is obtained.

[0081] Comparative Example 1

[0082] Ultra-high molecular weight polyethylene fiber

[0083] The raw materials are: 9 parts of UHMWPE powder (molecular weight 4.2 million), 90 parts of mineral oil, and 0.02 parts of antioxidant B225;

[0084] Preparation method:

[0085] (1) mixing and dissolving the various components of the above raw materials to form a UHMWPE spinning solution;

[0086] (2) using a spinning machine to perform gel spinning;

[0087] (3) adding 1.08 parts of γ-(methacryloyloxy)propyltrimethoxysilane and 0.18 parts of tert-butyl peroxy-2-ethylhexanoate to the extractant to prepare a mixed extract, and using the mixed extract to perform extraction and exchange to obtain primary fibers;

[0088] (4) drying the as-spun fiber in a drying oven and recovering part of the extract;

[0089] (5) 4-stage heat stretching, stretching temperature 110-155 degrees, total stretching ratio 30 times, and the result is obtained.

[0090] Experimental data

[0091] The ultra-high molecular weight polyethylene fibers prepared in the above-mentioned embodiments were subjected to mechanical property tests respectively, and the test method was GBT 19975-2005. The results are shown in Table 1 below.

[0092] Table 1

[0093]

[0094] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing creep-resistant ultra-high molecular weight polyethylene fiber, characterized in that: The method comprises the following steps: Mixing ultra-high molecular weight polyethylene powder, solvent, antioxidant and biochar powder, and stirring to form a spinning solution; Placing the spinning solution in a container for spinning to form jelly filaments; The jelly strands in the container are allowed to stand and undergo pre-extraction treatment; The extract after pre-extraction is subjected to extraction drying and multi-stage heat drawing treatment; Obtaining creep-resistant ultra-high molecular weight polyethylene fibers; in, The mass ratio of the ultra-high molecular weight polyethylene powder to the biochar powder is (70-97):(3-30); During the pre-extraction, a thermal initiator and a coupling agent are added into a container; the thermal initiator is any one of tert-butyl peroxy-2-ethylhexanoate, benzoic acid ester, and benzoyl peroxide; the amount of the thermal initiator is 0.5-5% of the amount of ultra-high molecular weight polyethylene; the coupling agent is a silane coupling agent, and the silane coupling agent is any one of γ-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and titanate coupling agent; the mass ratio of the thermal initiator and coupling agent added into the container to the ultra-high molecular weight polyethylene in the container is 1-3:5-8:45-55; the pre-extraction is carried out by an ultrasonic generator, and the pre-extraction time is 2-5 hours.

2. The method for preparing creep-resistant ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: The biochar powder includes one or more of corn straw charcoal powder, wheat straw charcoal powder and rice straw charcoal powder.

3. The method for preparing creep-resistant ultra-high molecular weight polyethylene fiber according to claim 1, characterized in that: The thermal initiator added into the container is tert-butyl peroxide-2-ethylhexanoate, and the coupling agent is γ-(methacryloyloxy)propyltrimethoxysilane; the ratio of tert-butyl peroxide-2-ethylhexanoate, γ-(methacryloyloxy)propyltrimethoxysilane and ultra-high molecular weight polyethylene is 1:6:

50.

4. A creep-resistant ultra-high molecular weight polyethylene fiber, characterized in that: Prepared by the method according to any one of claims 1 to 3.

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