Stress-whitening-resistant polyamide composite material as well as preparation method and application thereof

Abstract

The invention discloses a stress whitening resistant polyamide composite material, which comprises the following components by weight: 74-86 parts of polyamide; 0.1-1 part of rice bran wax metal salt; 5-30 parts of a toughening agent; and 0.3 to 0.8 part of carbon black and 0.1 to 0.5 part of aniline black. The rice bran wax salt is used as a nucleating agent to reduce the grain size of the crystal, the aniline black can improve the tinting power to a crystalline region to reduce light reflection at a stress whitening position, the carbon black can also adjust the tinting power to the crystal and an amorphous region, and under the cooperation of the three, the grain size of the crystal is reduced to be smaller than the wavelength of visible light to realize absorption of visible light. Light reflection caused by tiny gaps generated by separation of the flexibilizer and a polyamide resin matrix after the polyamide composite material is bent under stress is improved, and the defect of stress whitening of the polyamide composite material is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly to a stress-whitening resistant polyamide composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Nylon industrial cable ties are used for bundling and fixing cables, wires, and their components, and have requirements for material toughness, heat resistance, weather resistance, resistance to repeated bending fatigue, creep resistance, etc. With the increasing demand for cable ties from various industries such as automotive, electronics, and logistics, the global plastic cable ties will grow significantly in the next few years. According to the statistics of authoritative institutions, the average annual compound growth rate until 2029 is about 5%, and the annual market size is not less than 1.5 billion US dollars. With the advocacy of green and low-carbon economy, improving the service life and durability of industrial consumables has become one of the focus of attention. During the use of industrial cable ties, bending is inevitable. In actual use, it is found that the cable ties turn white during the bending process. Whitening not only affects the appearance, but also is prone to crack propagation and damage under the action of external factors such as light, heat, and oxygen during use.

[0003] During the tensile deformation process of polyamide, the isotropic crystal or spherulite morphology will develop into highly oriented fibrillar crystals, and the fiber structure will break with the increase of the elongation rate. According to the tensile conditions and sample pretreatment, the phenomenon of structural cavitation is often observed during the tensile process. Cavitation structures usually cause a whitening appearance because the pore size reaches the visible light level and causes visible light scattering. This whitening appearance significantly affects the performance and aesthetic appearance of the product.

[0004] Currently, it is generally believed that there are two typical scenarios that cause cavitation and whitening appearance. One occurs around the yield point of semi-crystalline polymers, and this does not require a large strain. Another cavitation stress whitening occurs at the end defects of the fibrillar structure in the later stage of stretching, and the formation of pores can be utilized, such as forming microporous membranes. However, in most cases, the formation of pore structures inside plastic materials belongs to defects and is a precursor to fracture. At the same time, the whitening appearance not only affects the aesthetic appearance but also indicates the initial stage of structural failure. The following methods are mainly used in the prior art to improve the stress whitening defect: CN117178023A discloses a polyamide composition that introduces 10-50% of maleated polyolefin to make the fracture surface have a stress whitening zone thickness of not less than 500 microns.

[0005] CN117024953A discloses a high-toughness and high-metal-bonding polyamide composition, which includes a long-chain polyamide resin, an elastomeric binder, an antioxidant, a color masterbatch, and a light stabilizer. Using polyether block polyamide as the elastomeric binder can improve the stress whitening resistance of the busbar sheath produced from this material after bending.

[0006] CN116063787A Improving stress whitening of thermoplastic composites by using fully vulcanized powder rubber and / or oil-extended fully vulcanized powder rubber as stress whitening resistance aids. Stress whitening is not only an aesthetic defect but also a sign of incipient microcracks and material failure. Summary of the Invention

[0007] The object of the present invention is to provide a polyamide composite with good stress whitening resistance.

[0008] The present invention is achieved by the following technical solutions: A stress whitening resistant polyamide composite, by weight, comprises the following components: 74 - 86 parts of polyamide; 0.1 - 1 part of rice bran wax metal salt; 0.3 - 0.8 part of carbon black; 0.1 - 0.5 part of aniline black; 5 - 30 parts of toughening agent; The nitrogen specific surface area of the carbon black is 100 - 800 m 2 / g.

[0009] The polyamide is selected from at least one of aromatic polyamides and aliphatic polyamides.

[0010] 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.

[0011] The aromatic polyamide is selected from PA MXD6, PA10T, PA10T1010, PA10T66, PA6T, PA6T66, PA9T, etc.

[0012] The aliphatic polyamide resin may also be selected from polycaprolactam, specifically PA5, PA6, PA11, PA12, etc.

[0013] Based on the weight percentage of the stress whitening resistant polyamide composite of the present invention, the weight content of polyamide is not less than 60 wt%.

[0014] The present invention has no particular limitation on the relative viscosity and melting point of the polyamide. Preferably, the range of the relative viscosity is 2.0 - 5.0 (the test method is to measure with an Ubbelohde viscometer, referring to ISO 307), and the preferred melting point range is 170 - 340 °C (the test method is to test with a differential scanning calorimeter, referring to GBT 19466.1 - 2004).

[0015] The rice bran wax metal salt described above is selected from at least one of sodium rice bran wax salt and calcium rice bran wax salt.

[0016] The average particle size of the rice bran wax metal salt is 10 - 800 microns. The average particle size is tested by a laser particle size analyzer.

[0017] Preferably, the nitrogen specific surface area of the carbon black is 190 - 400 m 2 / g. The specific surface area can be determined by the adsorption characteristics of carbon black for a specific gas (such as nitrogen), referring to ASTM D6556.

[0018] The nigrosine described above is selected from at least one of water-soluble nigrosine, alcohol-soluble nigrosine, and oil-soluble nigrosine; preferably oil-soluble nigrosine.

[0019] The water-soluble nigrosine can be CAS No. 8005 - 03 - 6 (the representative substance is Acid Black 2); The alcohol-soluble nigrosine can be CAS No. 11099 - 03 - 9 (the representative substance is Solvent Black 5); The oil-soluble nigrosine can be CAS No. 8005 - 02 - 5 (the representative substance is Solvent Black 7).

[0020] The toughening agent described above is selected from rubber or rubber grafted with active groups. The rubber is selected from at least one of polyolefin rubbers, polyacrylonitrile rubbers, polyacrylic rubbers, and polyester rubbers; the active group can be a maleic anhydride group or a glycidyl methacrylate group.

[0021] The polyacrylonitrile rubber described above is selected from at least one of butadiene-acrylonitrile rubber, hydrogenated butadiene-acrylonitrile rubber, acrylonitrile-isoprene rubber, 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, vinyl chloride rubber; the unsaturated polyolefin rubber is selected from at least one of ethylene-propylene-diene monomer rubber, butadiene-styrene rubber, styrene-ethylene-butadiene-styrene block copolymer, ethylene-propylene-butadiene rubber, styrene-butadiene-styrene copolymer, styrene-isoprene copolymer; the polyacrylic rubber is selected from at least one of ethylene-acrylic acid polymer, ethylene-acrylic acid ionomer; the polyester rubber is selected from at least one of ethylene-acrylate rubber, ethylene-vinyl acetate polymer, butadiene-acrylate rubber, ethylene-butyl acrylate-glycidyl methacrylate, core / shell elastomer of methacrylate-butadiene-styrene type.

[0022] It can be selected whether to add 0-30 parts of additives according to actual needs. The additives are selected from at least one of colorants, lubricants, light stabilizers, ultraviolet light absorbers, heat stabilizers, antioxidants, flame retardants, flame retardant synergists, anti-dripping agents, flow modifiers, mold release agents, antistatic agents, fluorescent brighteners, antibacterial agents.

[0023] The preparation method of the stress whitening resistant polyamide composite material of the present invention includes the following steps: according to the ratio, mix each component evenly, and extrude and pelletize through a twin-screw extruder to obtain the stress whitening resistant polyamide composite material.

[0024] The present invention also lies in a nylon industrial cable tie or equipment housing prepared by using the stress whitening resistant polyamide composite material of the present invention.

[0025] The present invention has the following beneficial effects: By using rice bran wax salt as a nucleating agent to reduce the crystal particle size, aniline black can improve the coloring ability of the crystalline region to reduce the light reflection at the stress whitening part, and carbon black can also adjust crystallization and the coloring ability of the amorphous region. Under the synergy of the three, the crystal particle size is reduced to be less than the visible light wavelength to achieve the absorption of visible light and reduce the light reflection at the stress whitening part. It improves the light reflection caused by the tiny voids generated by the separation of the toughening agent and the polyamide resin matrix after the polyamide composite material is bent under force, and thus significantly reduces the defect of stress whitening of the polyamide composite material. Description of the Drawings

[0026] Figure 1: Stress whitening test result spline diagram. Level 1 is on the left, and almost all of the spline has turned white; Level 8 is on the right, and the whitening is not obvious. Detailed implementation manners

[0027] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0028] The raw materials used in the present invention are as follows: PA66: EPR24, Pingdingshan Shenma, relative viscosity 2.4, melting point 264 °C; PA1012: PA1012, Shandong Guangyin, relative viscosity 2.4, melting point 178 °C; PA56: ECOPENT 1273 Resin, Kaisai Biotech, melting point 254 °C, relative viscosity 2.3; PA510: ECOPENT E-3102, Kaisai Biotech, melting point 214 °C, relative viscosity 2.2; PA6: HY-2500A, Jiangsu Haiyang Chemical Fiber, relative viscosity 2.4, melting point 222 °C; PA11: BMNO, Arkema, relative viscosity 2.4, melting point 188 °C; PA10T: Vicnyl 700, Kingfa Science & Technology, relative viscosity 2.2, melting point 316 °C; PA6T / 66: PA6T / 66 Kingfa Science & Technology, relative viscosity 2.3, 6T content 45 mol%; PA6T / 6I: PA6T / 6I, Kingfa Science & Technology, relative viscosity 2.3; Sodium salt of rice bran wax: R301, Chongqing Hecai Chemical Technology; Calcium salt of rice bran wax: R502, Chongqing Hecai Chemical Technology; Sodium lignite: LICOMONT NAV101, Clariant; Other nucleating agent A: HTPultra5L, Emmi Fabi; Other nucleating agent B: CHB-3C, Chenghe Technology; Toughening agent: Fusabond N493, maleic anhydride grafted ethylene octene copolymer, Dow; Aniline black A: Water-soluble aniline black, Acid Black 2, Jiangsu Bost Chemical Technology Co., Ltd.; Aniline black B: Alcohol-soluble aniline black, Solvent Black 5, Shenyang Shengda Chemical Co., Ltd.; Aniline Black C: Oil-soluble aniline black, Solvent Black 7, Hubei Xinyuhong Biomedical Technology Co., Ltd.; Carbon Black A: Raven 5100 Ultra, Columbian Chemicals Company, nitrogen specific surface area 583 m 2 / g; Carbon Black B: Raven 3500, Columbian Chemicals Company, nitrogen specific surface area 375 m 2 / g; Carbon Black C: Raven 2350 Ultra, Columbian Chemicals Company, nitrogen specific surface area 195 m 2 / g; Carbon Black D: Raven 1185 Ultra, Columbian Chemicals Company, nitrogen specific surface area 100 m 2 / g; Carbon Black E: Carbon Black D: Raven 860 Ultra, Columbian Chemicals Company, nitrogen specific surface area 48 m 2 / g Organic Dye Black: Provided by Kingfa Science & Technology Co., Ltd., CAS#12237-22-8; Lubricant: Ethylene-acrylic acid copolymer wax powder, A-C540A, purchased from ExxonMobil; Antioxidant: Antioxidant 1098, Antioxidant PEP-36, compounded in a ratio of 1:1, purchased from Adeka; Preparation method of stress-whitening resistant polyamide composites in examples and comparative examples: According to the ratio, mix each component evenly, and extrude and pelletize through a twin-screw extruder to obtain stress-whitening resistant polyamide composites. Among them, the maximum temperature of the barrel is the melting point of polyamide + (20 - 25°C).

[0029] Test methods for each item: (1) Stress whitening: A universal testing machine with a video attachment was used to test the tensile specimens at a tensile rate of 50 mm / min according to ISO527-2:2012, and the appearance at different strains during the tensile process was recorded. For the appearance photos at the initial state, 25% (when the fracture strain of the specimen is less than 50%), and 50% (when the fracture strain of the specimen is greater than 50%) strain, the Image J image processing software was used to convert them into 8-bit format, and the gray scale of the specimen in the middle of the extensometer was analyzed. The average gray value GV (0 - 255) was recorded, and the difference in the average gray value ΔGV between the target strain and the initial state was calculated. When ΔGV ≤ 10, the stress whitening resistance grade is 8; when 10 < ΔGV ≤ 20, the stress whitening resistance grade is 7; when 20 < ΔGV ≤ 30, the stress whitening resistance grade is 6; when 30 < ΔGV ≤ 40, the stress whitening resistance grade is 5; when 40 < ΔGV ≤ 50, the stress whitening resistance grade is 4; when 50 < ΔGV ≤ 60, the stress whitening resistance grade is 3; when 60 < ΔGV ≤ 80, the stress whitening resistance grade is 2; when ΔGV > 80, the stress whitening resistance grade is 1; the higher the grade, the better the stress whitening resistance performance. As Figure 1 shown, the left side is grade 1, the right side is grade 8, grade 4 is qualified, and grade 8 is the best.

[0030] Table 1: Weight parts of each component and test results of stress whitening resistant polyamide composites in Examples 1 - 7 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Polyamide type PA66 PA1012 PA56 PA510 PA6 PA11 PA10T Polyamide content 80 80 80 80 80 80 80 Sodium salt of 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 grade 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 Antioxidant 0.5 0.5 Stress whitening, grade 5 5 5 5 5 5 5 Table 2: Weight parts of each component and test results of stress whitening resistant polyamide composites in Examples 8 - 14 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Polyamide type PA6T / 66 PA6T / 6I PA66 PA66 PA66 PA66 PA66 Polyamide content 80 80 80 80 80 80 80 Sodium salt of rice bran wax 0.5 0.5 0.5 0.5 0.5 0.5 Calcium salt of rice bran wax 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 grade 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 From Examples 1 / 11 - 13, it can be seen that when the nitrogen specific surface area of the preferred carbon black is 190 - 400 m 2 / g, the stress whitening resistance performance is better.

[0031] Table 3: Weight parts of each component and test results of stress whitening resistant polyamide composites in Examples 15 - 17 Example 15 Example 16 Example 17 Polyamide type PA66 PA66 PA66 Polyamide content 80 75 85 Sodium salt of 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 grade C A A Aniline black content 0.3 0.1 0.5 Toughening agent 20 30 5 Stress whitening, grade 6 5 5 From Examples 1 / 14 - 15, it can be seen that when the preferred oil-soluble aniline black is used, the coloring ability for the crystalline region is better and the stress whitening resistance performance is better.

[0032] Table 4: Weight parts of each component and test results of stress whitening resistant polyamide composites in Comparative Examples 1 - 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Polyamide type PA66 PA66 PA66 PA66 PA66 PA66 Polyamide content 80 80 80 80 80 80 Sodium salt of rice bran wax 0 0.5 0.5 Sodium lignite 0.5 Other nucleating agent A 0.5 Other nucleating agent 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 grade 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 From Comparative Example 1, it can be seen that when sodium rice bran wax is not contained, crystals with a particle size smaller than the visible light wavelength cannot be obtained, so the stress whitening resistance performance is poor. However, due to the presence of aniline black, the stress whitening can reach level 2.

[0033] As can be seen from Comparative Examples 2 / 3 / 4, other nucleating agents cannot obtain crystals with a particle size smaller than the visible light wavelength.

[0034] As can be seen from Comparative Example 5, crystals with a particle size smaller than the visible light wavelength cannot be obtained without carbon black, and the stress whitening resistance is poor.

[0035] As can be seen from Comparative Example 6, when aniline black is not contained, the light reflection at the stress whitening part is less, so the stress whitening is obvious.

[0036] Table 5: Parts by weight of each component of the stress whitening resistant polyamide composite materials in Comparative Examples 7 - 8 and test results Comparative Example 7 Comparative Example 8 Polyamide type PA66 PA66 Polyamide content 80 80 Sodium salt of rice bran wax 0.5 0.5 Carbon black grade A E Carbon black content 0.5 0.5 Aniline black grade / C Aniline black content 0 0.3 Organic dye black 0.3 Toughening agent 20 20 Stress whitening, grade 3 2 As can be seen from Comparative Example 7, using other non - carbon black organic dye blacks cannot achieve the technical effects of aniline black.

[0037] As can be seen from Comparative Example 8, if the nitrogen specific surface area of carbon black is too low, crystals with a particle size smaller than the visible light wavelength cannot be obtained.

Claims

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

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

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

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

6. The stress-whitening resistant 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; oil-soluble aniline black is preferred.

7. The stress-whitening resistant 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 acid rubber, and polyester rubber, and the active group is selected from maleic anhydride group or methacrylate glycidyl group; 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, vinyl chloride rubber; unsaturated polyolefin rubber is selected from at least one of EPDM rubber, butadiene-styrene rubber, styrene-ethylene-butadiene-styrene block copolymer, ethylene-propylene-butadiene rubber, styrene-butadiene-styrene copolymer, and styrene-isoprene copolymer; polyacrylic acid rubber is selected from at least one of ethylene-acrylic acid polymer and ethylene-acrylic acid ionomer; polyester rubber is selected from at least one of ethylene-acrylate rubber, ethylene-vinyl acetate polymer, butadiene-acrylate rubber, ethylene-butyl acrylate-glycidyl methacrylate, and methacrylate-butadiene-styrene type core / shell elastomers.

8. The stress-whitening resistant polyamide composite material according to claim 1, characterized in that: By weight, it also includes 0-30 parts of auxiliary agents, which are selected from at least one of lubricants, light stabilizers, ultraviolet light absorbers, heat stabilizers, antioxidants, flame retardants, flame retardant synergists, anti-dripping agents, flow modifiers, release agents, antistatic agents, fluorescent brighteners, and antibacterial agents.

9. The method for preparing the stress-whitening resistant polyamide composite material according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: mixing the components uniformly according to the proportion, extruding and granulating the components through a twin-screw extruder, and obtaining a stress-whitening-resistant polyamide composite material.

10. A nylon industrial cable tie or equipment housing prepared using the stress-whitening resistant polyamide composite material according to any one of claims 1 to 8.

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