Stress whitening resistant polyamide composite and method of making and use thereof

Abstract

The application discloses a stress whitening resistant polyamide composite material, which comprises the following components in parts by weight: polyamide 74-86 parts; rice bran wax metal salt 0.1-1 part; toughening agent 5-30 parts; carbon black 0.3-0.8 part; and aniline black 0.1-0.5 part. The application utilizes the rice bran wax salt as a nucleating agent to reduce the crystal particle size, the aniline black can improve the coloring ability to the crystalline region to reduce the light reflection at the stress whitening position, and the carbon black can also adjust the crystallization and the coloring ability to the amorphous region, so that the crystal particle size is reduced to less than the wavelength of visible light to realize the absorption of visible light. The light reflection caused by the tiny gap generated due to the separation of the toughening agent and the polyamide resin matrix after the stress bending of the polyamide composite material is improved, and the defects of the stress whitening of the polyamide composite material are significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a stress-resistant whitening polyamide composite material, its preparation method, and its application. Background Technology

[0002] Nylon industrial cable ties are used to bundle and secure cables, wires, and their components. They require properties such as toughness, heat resistance, weather resistance, resistance to repeated bending fatigue, and creep resistance. Driven by increasing demand from industries such as automotive, electronics, and logistics, the global market for plastic cable ties is expected to grow significantly in the coming years. According to authoritative statistics, the average annual compound growth rate is projected to be approximately 5% until 2029, with an annual market size of no less than $1.5 billion. With the advocacy of a green and low-carbon economy, improving the lifespan and durability of industrial consumables has become a key focus. Industrial cable ties inevitably face bending during use. In practice, it has been observed that cable ties turn white during bending, which not only affects appearance but also makes them more susceptible to crack propagation and damage from external factors such as light, heat, and oxygen.

[0003] During tensile deformation, polyamide crystals, whether isotropic or spherulitic, develop into highly oriented fibrous crystals, which then fracture with increasing elongation. Depending on the tensile conditions and sample pretreatment, structural cavitation is frequently observed during the tensile process. This cavitation typically results in a whitish appearance due to the pore size reaching visible light levels and causing visible light scattering. This whitish appearance significantly impacts the product's performance and aesthetics.

[0004] Currently, two typical scenarios are generally considered to lead to cavitation and a whitening appearance. One occurs around the yield point of partially crystalline polymers, which does not require a large strain. The other type of stress-induced whitening occurs in the later stages of tensile stress, resulting in pores caused by defects at the ends of the fibrous structure. The formation of these pores can be utilized, such as by forming microporous membranes. However, in most cases, the formation of pore structures within plastic materials is considered a defect, a precursor to fracture, and the whitening appearance not only affects aesthetics but also indicates the early stage of structural failure. Existing technologies mainly improve stress-induced whitening defects through the following methods:

[0005] CN117178023A discloses a polyamide composition in which 10-50% maleic acid-modified polyolefin is introduced to give the fracture surface a stress whitening zone thickness of not less than 500 micrometers.

[0006] CN117024953A discloses a high-toughness, high-metal-adhesion polyamide composition comprising a long-chain polyamide resin, an elastomer binder, an antioxidant, a color masterbatch, and a light stabilizer. The polyether block polyamide is used as the elastomer binder to improve the material's ability to prevent stress whitening of the busbar sheath after bending.

[0007] CN116063787A uses fully vulcanized powdered rubber and / or oil-extended fully vulcanized powdered rubber as stress-whitening resistant additives to improve stress whitening of thermoplastic composites. Stress whitening is both an appearance defect and a sign of microcracks and material failure. Summary of the Invention

[0008] The purpose of this invention is to provide a polyamide composite material with good stress whitening resistance.

[0009] This invention is achieved through the following technical solution:

[0010] A stress-resistant whitening polyamide composite material, comprising the following components by weight:

[0011] 74-86 parts of polyamide;

[0012] 0.1-1 part of rice bran wax metal salt;

[0013] Carbon black 0.3-0.8 parts;

[0014] Aniline black 0.1-0.5 parts;

[0015] Toughening agent 5-30 parts;

[0016] The nitrogen specific surface area of ​​the carbon black is 100-800 m². 2 / g.

[0017] The polyamide is selected from at least one of aromatic polyamides and aliphatic polyamides.

[0018] The aliphatic polyamide resin is selected from PA66, PA46, PA610, PA612, PA56, PA510, PA512, PA910, PA912, PA913, PA914, PA915, PA616, PA936, PA1010, PA1012, PA1013, PA1014, PA1210, PA1212, PA1213, PA1214, PA614, PA613, PA615, PA616, etc.

[0019] The aromatic polyamide is selected from PA MXD6, PA10T, PA10T1010, PA10T66, PA6T, PA6T66, PA9T, etc.

[0020] The aliphatic polyamide resin may also be selected from polylactams, specifically PA5, PA6, PA11, PA12, etc.

[0021] Based on the weight percentage of the stress-resistant whitening polyamide composite material of the present invention, the weight content of polyamide is not less than 60 wt%.

[0022] This invention does not impose any particular limitations on the relative viscosity and melting point of the polyamide. The preferred relative viscosity range is 2.0-5.0 (tested by measuring with an Ubbelohde viscometer, refer to ISO 307), and the preferred melting point range is 170-340℃ (tested by measuring with a differential scanning calorimeter, refer to GBT 19466.1-2004).

[0023] The rice bran wax metal salt is selected from at least one of rice bran wax sodium salt and rice bran wax calcium salt.

[0024] The average particle size of the rice bran wax metal salt is 10-800 micrometers. The average particle size was measured using a laser particle size analyzer.

[0025] Preferably, the nitrogen specific surface area of ​​the carbon black is 190-400 m². 2 / g. The specific surface area can be determined by the adsorption characteristics of carbon black for specific gases (such as nitrogen), refer to ASTM D6556.

[0026] The aniline black is selected from at least one of water-soluble aniline black, alcohol-soluble aniline black, and oil-soluble aniline black; preferably oil-soluble aniline black.

[0027] Water-soluble aniline black can be represented by CAS No. 8005-03-6 (represented by Acid Black 2).

[0028] Alcohol-soluble aniline black can be represented by CAS No. 11099-03-9 (represented by Solvent Black 5).

[0029] Oil-soluble aniline black can be CAS No. 8005-02-5 (represented by solvent black 7).

[0030] The toughening agent is selected from rubber or rubber grafted with active groups. The rubber is selected from at least one of polyolefin rubber, polyacrylonitrile rubber, polyacrylic rubber, and polyester rubber. The active group can be maleic anhydride group or glycidyl methacrylate group.

[0031] The polyacrylonitrile rubber is selected from at least one of butadiene-acrylonitrile rubber, hydrogenated butadiene-acrylonitrile rubber, acrylonitrile-isoprene rubber, and acrylonitrile-butadiene-styrene copolymer; the polyolefin rubber is selected from at least one of saturated polyolefin rubber and unsaturated polyolefin rubber; the saturated polyolefin rubber is selected from ethylene-octene copolymer, polyethylene rubber, polypropylene rubber, polyisobutylene rubber, ethylene-propylene rubber, linear low-density polyethylene rubber, ethylene-butene rubber, and vinyl chloride rubber; the unsaturated polyolefin rubber is selected from ethylene propylene diene monomer (EPDM) rubber, butadiene-... At least one of styrene rubber, styrene-ethylene-butadiene-styrene block copolymer, ethylene-propylene-butadiene rubber, styrene-butadiene-styrene copolymer, and styrene-isoprene copolymer; polyacrylic rubber is selected from at least one of ethylene-acrylic polymer and ethylene-acrylic ionomer; polyester rubber is selected from at least one of ethylene-acrylate rubber, ethylene-vinyl acetate polymer, butadiene-acrylate rubber, ethylene-n-butyl acrylate-glycidyl methacrylate, and methacrylate-butadiene-styrene type core / shell elastomers.

[0032] Depending on actual needs, 0-30 parts of additives may be added. The additives are selected from at least one of colorants, lubricants, light stabilizers, ultraviolet absorbers, heat stabilizers, antioxidants, flame retardants, flame retardant synergists, anti-dripping agents, flow modifiers, release agents, antistatic agents, fluorescent whitening agents, and antibacterial agents.

[0033] The method for preparing stress-resistant whitening polyamide composite material of the present invention includes the following steps: mixing each component evenly according to the formula, and granulating by extrusion through a twin-screw extruder to obtain stress-resistant whitening polyamide composite material.

[0034] The present invention also relates to nylon industrial cable ties or equipment housings prepared using the stress-resistant whitening polyamide composite material of the present invention.

[0035] The present invention has the following beneficial effects:

[0036] This invention utilizes rice bran wax salt as a nucleating agent to reduce crystal size, aniline black to enhance the coloring ability of crystalline regions to reduce light reflection at stress-induced whitening, and carbon black to adjust the crystal structure and coloring ability of amorphous regions. The synergistic effect of these three agents reduces the crystal size to below the visible light wavelength, enabling visible light absorption and reducing light reflection at stress-induced whitening. This improves the light reflection caused by the tiny voids resulting from the separation of the toughening agent from the polyamide resin matrix after bending under stress in polyamide composites, thereby significantly reducing the stress-induced whitening defect in polyamide composites. Attached Figure Description

[0037] Figure 1The spline diagram shows the results of the stress whitening test. The left side is level 1, where the spline is almost completely whitened; the right side is level 8, where the whitening is not obvious. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0039] The raw materials used in this invention are sourced from the following sources:

[0040] PA66: EPR24, Pingdingshan Shenma, relative viscosity 2.4, melting point 264℃;

[0041] PA1012: PA1012, Shandong Guangyin, relative viscosity 2.4, melting point 178℃;

[0042] PA56: ECOPENT 1273 Resin, Kaisai Biotechnology, melting point 254℃, relative viscosity 2.3;

[0043] PA510: ECOPENT E-3102, Kaisai Biotechnology, melting point 214℃, relative viscosity 2.2;

[0044] PA6: HY-2500A, Jiangsu Haiyang Chemical Fiber, relative viscosity 2.4, melting point 222℃;

[0045] PA11: BMNO, Arkema, relative viscosity 2.4, melting point 188℃;

[0046] PA10T: Vicnyl 700, Kingfa Science & Technology, relative viscosity 2.2, melting point 316℃;

[0047] PA6T / 66: Kingfa Science & Technology's PA6T / 66, relative viscosity 2.3, 6T content 45 mol%;

[0048] PA6T / 6I: PA6T / 6I, Kingfa Science & Technology, relative viscosity 2.3;

[0049] Sodium rice bran wax: R301, Chongqing Hecai Chemical Technology;

[0050] Rice bran wax calcium salt: R502, Chongqing Hecai Chemical Technology;

[0051] Sodium lignite: LICOMONT NAV101, Clariant;

[0052] Other nucleating agent A: HTPultra 5L, imifab;

[0053] Other nucleating agent B: CHB-3C, Chenghe Technology;

[0054] Toughening agent: Fusabond N493, maleic anhydride-grafted ethylene octene copolymer, Dow;

[0055] Aniline Black A: Water-soluble aniline black, Acid Black 2, Jiangsu Bosite Chemical Technology Co., Ltd.;

[0056] Aniline Black B: Alcohol-soluble aniline black, solvent black 5, Shenyang Shengda Chemical Co., Ltd.;

[0057] Aniline Black C: Oil-soluble aniline black, solvent black 7, Hubei Xinyuhong Biomedical Technology Co., Ltd.;

[0058] Carbon Black A: Raven 5100 Ultra, Columbia Chemicals Company, nitrogen specific surface area 583 m² 2 / g;

[0059] Carbon Black B: Raven 3500, Columbia Chemicals Company, nitrogen specific surface area 375 m² 2 / g;

[0060] Carbon black C: Raven 2350 Ultra, Columbia Chemicals Company, nitrogen specific surface area 195 m² 2 / g;

[0061] Carbon black D: Raven 1185 Ultra, Columbia Chemicals Company, nitrogen specific surface area 100 m² 2 / g;

[0062] Carbon black E: Carbon black D: Raven 860 Ultra, Columbia Chemicals Company, nitrogen specific surface area 48 m² 2 / g

[0063] Organic dye black: provided by Kingfa Science & Technology, CAS#12237-22-8;

[0064] Lubricant: Ethylene-acrylic acid copolymer wax powder, A-C540A, purchased from ExxonMobil;

[0065] Antioxidants: Antioxidant 1098 and antioxidant PEP-36, mixed in a 1:1 ratio, purchased from Adico;

[0066] Preparation method of stress-resistant whitening polyamide composite material in the examples and comparative examples: The components were mixed evenly according to the specified ratio, and then extruded and granulated using a twin-screw extruder to obtain the stress-resistant whitening polyamide composite material. The highest temperature of the screw barrel was the melting point of the polyamide + (20-25℃).

[0067] Test methods:

[0068] (1) Stress whitening: A universal testing machine with video recording attachment was used to test the tensile specimen at a tensile rate of 50 mm / min according to ISO 527-2:2012, and the appearance under different strains during the tensile process was recorded. Images of the appearance at the initial state, 25% (when the specimen's fracture strain is less than 50%), and 50% (when the specimen's fracture strain is greater than 50%) were used for image processing. Using J graphics processing software, the image is converted to 8-bit format. The grayscale of the spline located in the middle of the extensometer is analyzed, and the average grayscale value GV (0~255) is recorded. The difference between the average grayscale value of the target strain and the initial state, ΔGV, is calculated. When ΔGV≤10, the stress whitening resistance level is 8; when 10<ΔGV≤20, the stress whitening resistance level is 7; when 20<ΔGV≤30, the stress whitening resistance level is 6; when 30<ΔGV≤40, the stress whitening resistance level is 5; when 40<ΔGV≤50, the stress whitening resistance level is 4; when 50<ΔGV≤60, the stress whitening resistance level is 3; when 60<ΔGV≤80, the stress whitening resistance level is 2; when ΔGV>80, the stress whitening resistance level is 1. The higher the level, the better the stress whitening resistance performance. Figure 1 As shown, the left side represents level 1, and the right side represents level 8. Level 4 is considered qualified, and level 8 is the best.

[0069] Table 1: Weight parts of each component and test results of stress-resistant whitening polyamide composites in Examples 1-7

[0070] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Polyamide types PA66 PA1012 PA56 PA510 PA6 PA11 PA10T polyamide content 80 80 80 80 80 80 80 Sodium rice bran wax 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Carbon black grade A A A A A A A Carbon black content 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Aniline Black Label A A A A A A A Aniline black content 0.3 0.3 0.3 0.3 0.3 0.3 0.3 toughening agent 20 20 20 20 20 20 20 lubricant 0.5 0.5 antioxidants 0.5 0.5 Stress whitening, grade 5 5 5 5 5 5 5

[0071] Table 2: Weight parts of each component and test results of stress-resistant whitening polyamide composites in Examples 8-14

[0072] Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Polyamide types PA6T / 66 PA6T / 6I PA66 PA66 PA66 PA66 PA66 polyamide content 80 80 80 80 80 80 80 Sodium rice bran wax 0.5 0.5 0.5 0.5 0.5 0.5 Rice bran wax calcium salt 0.5 Carbon black grade A A A B C D A Carbon black content 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Aniline Black Label A A A A A A B Aniline black content 0.3 0.3 0.3 0.3 0.3 0.3 0.3 toughening agent 20 20 20 20 20 20 20 Stress whitening, grade 5 5 5 6 6 5 5

[0073] As shown in Examples 1 / 11-13, the preferred carbon black has a nitrogen specific surface area of ​​190-400 m². 2 The stress whitening resistance is better at / g.

[0074] Table 3: Weight parts of each component and test results of stress-resistant whitening polyamide composites in Examples 15-17

[0075] Example 15 Example 16 Example 17 Polyamide types PA66 PA66 PA66 polyamide content 80 75 85 Sodium rice bran wax 0.5 1 0.1 Carbon black grade A A A Carbon black content 0.5 0.3 0.8 Aniline Black Label C A A Aniline black content 0.3 0.1 0.5 toughening agent 20 30 5 Stress whitening, grade 6 5 5

[0076] As can be seen from Examples 1 / 14-15, oil-soluble aniline black is preferred for its better coloring ability in the crystalline region and its better resistance to stress whitening.

[0077] Table 4: Weight parts of each component and test results of stress-resistant whitening polyamide composites in Comparative Examples 1-6

[0078] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Polyamide types PA66 PA66 PA66 PA66 PA66 PA66 polyamide content 80 80 80 80 80 80 Sodium rice bran wax 0 0.5 0.5 Sodium lignite 0.5 Other nucleating agent A 0.5 Other nucleating agents B 0.5 Carbon black grade A A A A / B Carbon black content 0.5 0.5 0.5 0.5 0 0.8 Aniline Black Label C C C C C / Aniline black content 0.3 0.3 0.3 0.3 0.8 0 toughening agent 20 20 20 20 20 20 Stress whitening, grade 2 2 2 2 2 3

[0079] As can be seen from Comparative Example 1, without the presence of rice bran wax sodium salt, it is impossible to obtain crystals with a particle size smaller than the wavelength of visible light, thus resulting in poor stress whitening resistance. However, due to the presence of aniline black, stress whitening can reach level 2.

[0080] As can be seen from Comparative Examples 2 / 3 / 4, other nucleating agents cannot produce crystals with particle sizes smaller than the wavelength of visible light.

[0081] As shown in Comparative Example 5, it is impossible to obtain crystals with a particle size smaller than the wavelength of visible light without carbon black, resulting in poor stress whitening resistance.

[0082] As shown in Comparative Example 6, when aniline black is not present, there is less light reflection at the stress-induced whitening area, thus the stress-induced whitening is more obvious.

[0083] Table 5: Weight parts of each component and test results of stress-resistant whitening polyamide composites of Comparative Examples 7-8

[0084] Comparative Example 7 Comparative Example 8 Polyamide types PA66 PA66 polyamide content 80 80 Sodium rice bran wax 0.5 0.5 Carbon black grade A E Carbon black content 0.5 0.5 Aniline Black Label / C Aniline black content 0 0.3 Organic dye black 0.3 toughening agent 20 20 Stress whitening, grade 3 2

[0085] As can be seen from Comparative Example 7, other non-carbon black organic dyes cannot achieve the technical effect of aniline black.

[0086] As can be seen from Comparative Example 8, if the nitrogen specific surface area of ​​carbon black is too low, it is also impossible to obtain crystals with a particle size smaller than the wavelength of visible light.

Claims

1. A stress-resistant whitening polyamide composite material, characterized in that, By weight, it includes the following components: 74-86 parts of polyamide; 0.1-1 part of rice bran wax metal salt; Carbon black 0.3-0.8 parts; Aniline black 0.1-0.5 parts; Toughening agent 5-30 parts; The nitrogen specific surface area of ​​the carbon black is 100-800 m². 2 / g.

2. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The polyamide is selected from at least one of aromatic polyamides and aliphatic polyamides.

3. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The rice bran wax metal salt is selected from at least one of rice bran wax sodium salt and rice bran wax calcium salt.

4. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The average particle size of the rice bran wax metal salt is 10-800 micrometers.

5. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The nitrogen specific surface area of ​​the carbon black is 190-400 m². 2 / g.

6. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The aniline black is selected from at least one of water-soluble aniline black, alcohol-soluble aniline black, and oil-soluble aniline black.

7. The stress-resistant whitening polyamide composite material according to claim 6, characterized in that, The aniline black mentioned is selected from oil-soluble aniline black.

8. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The toughening agent is selected from rubber or rubber grafted with active groups. The rubber is selected from at least one of polyolefin rubber, polyacrylonitrile rubber, polyacrylic rubber, and polyester rubber. The active group is selected from maleic anhydride groups or glycidyl methacrylate groups. The polyacrylonitrile rubber is selected from at least one of butadiene-acrylonitrile rubber, hydrogenated butadiene-acrylonitrile rubber, acrylonitrile isoprene rubber, and acrylonitrile-butadiene-styrene copolymer. The polyolefin rubber is selected from at least one of saturated polyolefin rubber and unsaturated polyolefin rubber. The saturated polyolefin rubber is selected from ethylene-octene copolymer, polyethylene rubber, polypropylene rubber, and polyisobutylene. Rubber, ethylene-propylene rubber, ethylene-butene rubber, vinyl chloride rubber; unsaturated polyolefin rubbers are selected from at least one of ethylene propylene diene monomer (EPDM) rubber, butadiene-styrene rubber, styrene-ethylene-butadiene-styrene block copolymer, ethylene-propylene-butadiene rubber, and styrene-isoprene copolymer; polyacrylic rubbers are selected from at least one of ethylene-acrylic acid polymers and ethylene-acrylic acid ionomers; polyester rubbers are selected from at least one of core / shell elastomers of the type of ethylene-acrylate rubber, ethylene-vinyl acetate polymer, butadiene-acrylate rubber, ethylene-n-butyl acrylate-glycidyl methacrylate, and methacrylate-butadiene-styrene.

9. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The toughening agent is selected from rubber or rubber grafted with active groups. The rubber is selected from polyolefin rubber, and the active groups are selected from maleic anhydride groups or glycidyl methacrylate groups. The polyolefin rubber is selected from at least one of saturated polyolefin rubber and unsaturated polyolefin rubber. The saturated polyolefin rubber is selected from linear low-density polyethylene rubber. The unsaturated polyolefin rubber is selected from styrene-butadiene-styrene copolymer.

10. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The product also includes 0-30 parts by weight of additives, wherein the additives are selected from at least one of lubricants, light stabilizers, heat stabilizers, antioxidants, flame retardants, flame retardant synergists, anti-dripping agents, flow modifiers, release agents, antistatic agents, fluorescent whitening agents, and antibacterial agents.

11. The stress-resistant whitening polyamide composite material according to claim 1, characterized in that, The product also includes 0-30 parts by weight of an additive selected from ultraviolet absorbers.

12. The method for preparing the stress-resistant whitening polyamide composite material according to any one of claims 1-11, characterized in that, The process includes the following steps: mixing the components evenly according to the formula, and granulating them by extrusion through a twin-screw extruder to obtain a stress-resistant whitening polyamide composite material.

13. A nylon industrial cable tie or equipment housing made using the stress-resistant whitening polyamide composite material according to any one of claims 1-11.

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