Heat-aging-resistant flexible polyamide composite material and preparation method thereof

Abstract

The invention provides a heat-aging-resistant flexible polyamide composite material and a preparation method thereof. Comprising the following components in parts by weight: 45-83 parts of polyamide; 5 to 15 parts of polypropylene; 0.5 to 3 parts of a compatilizer; 8-25 parts of a toughness modifier; 3-15 parts of a flexible modifier; 0.1 to 2 parts of an antioxidant; and 0-1 part of a chain extender. The flexible long-carbon-chain polyamide material provided by the invention keeps excellent toughness and processing flexibility, and also obtains excellent long-term thermal aging resistance, the notch impact strength retention rate can reach 70% or above at 150 DEG C / 500 h, the tensile elongation at break retention rate can reach 50% or above, and the long-term thermal aging resistance can reach 70% or above at 150 DEG C / 500 h. The composite material is suitable for structural parts or functional parts around an automobile engine used under high temperature and vibration, and is especially suitable for being applied to parts such as automobile air pipes, oil pipes and cooling liquid pipelines.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a heat-aging-resistant flexible polyamide composite material and a preparation method thereof. Background Art

[0002] With the rapid development of automobile lightweighting, the application scope of non-metallic products is also expanding. Among them, plastic products are the most widely used. The application of plastics has expanded from interior decoration to parts and components. Lightweighting has become a trend.

[0003] Nylon is oil-resistant, pressure-resistant, corrosion-resistant, shock-resistant, cold-resistant, has good flexibility, and has a low fuel expansion coefficient. It is also very easy to process, so it is an ideal material for manufacturing automotive oil pipes. In addition, compared to rubber pipes, nylon has the advantages of being light, environmentally friendly, and recyclable.

[0004] Among them, long carbon chain nylon refers to nylon with a methylene length of more than 10 in the chain segment, including PA11, PA12, PA1012, PA1010, PA1212, PA612, PA610, PA513, PA515, etc. In the automotive field, in order to adapt to the limited interior layout space, the pipe bends need to have large bendability. If the material modulus is too high, it is easy to cause hard pressure damage. Long carbon chain nylon still has good toughness and softness under low temperature conditions. Therefore, in low temperature areas, long carbon chain nylon can be used to prepare soft products and cold-resistant parts.

[0005] In developed countries, 60% to 70% of long-chain nylon is used to produce automotive hoses, such as brake pipes, oil pipes, clutch hoses, etc. 70% of automotive hoses in Europe are made of PA12, and half of automotive hoses in the United States are made of PA12. PA12 can be widely used in automotive fluid delivery pipelines, including fuel lines, clutch lines, vacuum brake booster lines, air brake lines, battery coolant lines, and the joints of the above lines. Because of its safety and reliability, it is an excellent automotive lightweight material.

[0006] Furthermore, as a polyamide composite material for automobile engine peripheral parts, it must not only have the toughness to be used in complex environments, the flexibility to facilitate processing and molding and assembly in narrow spaces, but also have good long-term heat aging resistance under harsh working conditions, especially the strength and toughness (tensile elongation at break and impact strength) cannot decay too quickly, because the engine peripheral parts need to be exposed to high temperature environments during their service life, and are in a long-term vibration state during operation. If the strength and toughness decay too quickly, it will directly cause the parts to fail prematurely before the normal service life, posing huge safety hazards and economic risks. For this reason, the OEMs have successively increased the heat aging standards for materials, such as from 120°C to 150°C. Therefore, it is very necessary to research and develop polyamide composite materials that have both toughness, softness and heat aging resistance, which has great practical significance.

[0007] DOWSIL was the first to develop silicone polyamide elastomers, thermoplastic silicone elastomers formed by vulcanized silicone rubber particles on a polyamide substrate. They can still maintain high mechanical strength after high-temperature aging at 150°C and can be used continuously at high temperatures of 140°C. They can be used in products in consumer electronics, cosmetics, food, and automotive industries. However, their price is more than five times more expensive, and their application in the field of automotive pipelines is obviously not economical. Summary of the invention

[0008] To solve the above problems, the present invention provides a heat-resistant and aging-resistant flexible polyamide composite material, which maintains excellent toughness and processing softness, and also obtains excellent long-term heat-resistant aging performance. At 150°C / 500h, the notched impact strength retention rate can reach more than 70%, and the tensile elongation at break retention rate can reach more than 50%.

[0009] To achieve the above object, the present invention adopts the following technical solution:

[0010] A heat-aging-resistant flexible polyamide composite material comprises the following raw materials in parts by weight:

[0011] Polyamide 45-83 parts;

[0012] Polypropylene 5-15 parts;

[0013] Compatibilizer 0.5-3 parts;

[0014] 8-25 parts of toughness modifier;

[0015] 3-15 parts of flexibility modifier;

[0016] Antioxidant 0.1-2 parts;

[0017] Chain extender 0-1 part.

[0018] The polyamide is selected from one or more of PA11, PA12, PA610, PA612, PA1010, PA1012, PA1212, PA510, PA513, and PA515.

[0019] The polypropylene is a composition of polypropylene A and polypropylene B; the polypropylene A is a random copolymer polypropylene, and its melt flow rate is 0.2-3g / 10min at 230°C / 2.16KG; the polypropylene B is a homopolymer polypropylene, and its melt flow rate is 0.2-3g / 10min at 230°C / 2.16KG; the weight ratio of the polypropylene A to the polypropylene B is 10:1-3:1.

[0020] The polypropylene is a widely used general-purpose plastic because of its light weight, wide source and low price. It is currently known to be used in polyamide systems mainly as a lightweight and low-cost compound, and it is often also required to be used under the premise of a large performance margin. However, there is no report on using it to improve the heat aging resistance of polyamide systems. In addition, due to the compatibility problem between polypropylene and polyamide, those skilled in the art will exclude it at the first time when designing a formula for the purpose of improving the long-term heat aging resistance of the polyamide system. The inventors have unexpectedly found through a large number of experimental verifications that the introduction of suitable polypropylene into a flexible polyamide system can significantly improve the heat aging resistance of polyamide-based composite materials.

[0021] The compatibilizer is polyacrylamide. The polyacrylamide has good compatibility with both polypropylene and polyamide, can play an excellent bridge role, and compared with the compatibilizers such as silane coupling agents in traditional tests, it can give the composite material better interface bonding and dispersed distribution.

[0022] The toughness modifier is any one of maleic anhydride grafted octene ethylene copolymer, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene, or a combination of two or more thereof.

[0023] The flexibility modifier is any one of N-butylbenzenesulfonamide, dioctyl phthalate, dibutyl phthalate, bisphenol A bis(diphenyl phosphate)\resorcinol bis(diphenyl phosphate) or a combination of two or more thereof.

[0024] The antioxidant is one or a combination of multiple of copper salt antioxidants, phosphate antioxidants, amine antioxidants, phenolic antioxidants and ester antioxidants.

[0025] The chain extender is an epoxy chain extender, preferably an acrylic acid and styrene copolymer containing epoxy functional groups.

[0026] The preparation method of the above-mentioned heat-resistant and aging-resistant flexible polyamide composite material comprises the following steps: (1) weighing the raw materials respectively according to the dosage of the formula; (2) putting the other components except the liquid flexibility modifier into a high-speed mixer and mixing them until they are uniform to obtain a premix; (3) then putting the obtained premix into a twin-screw extruder for melt mixing, and the flexibility modifier adopts a liquid pump side feeding process for extrusion granulation; wherein the extrusion temperature is 200-250°C, and the screw speed is set to 250-500rpm.

[0027] The inventors adopt the modified long carbon chain polyamide by blending and compounding, and the obtained composite material meets the requirements of toughness and softness, but its heat aging resistance is not ideal. After a large number of experiments and verifications, it is surprisingly found that the use of the technical means recognized in the art to improve the heat aging resistance of polyamide - adding heat stabilizers such as copper salt antioxidants, phosphate antioxidants, amine antioxidants, phenolic antioxidants, etc., the heat aging resistance of polyamide pipeline composite materials is not satisfactory, especially the toughness decays too fast, specifically, the notched impact strength retention rate after 150℃ / 500h heat aging drops to less than 40%, and the tensile elongation at break retention rate drops to less than 30%.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention introduces polypropylene into the long-chain polyamide system to give the flexible long-chain polyamide composite material excellent long-term heat aging resistance. After heat aging at 150°C for 500 hours, the notched impact strength retention rate can reach more than 70%, and the tensile elongation at break retention rate can reach more than 50%. The composite material is suitable for structural parts or functional parts around automobile engines used under high temperature and vibration, which not only broadens the application field of polyamide materials, but also broadens the application of polypropylene in the polyamide system.

[0030] (2) The synergistic combination of acrylamide compatibilizer enables the flexible long-chain polyamide material to maintain excellent initial flexibility and possess high initial notched impact strength and low-temperature notched impact strength. DETAILED DESCRIPTION

[0031] In order to make the technical solution of the present invention clearer and more specific, the present invention is further described below. Any equivalent replacement of the technical features of the technical solution of the present invention and any solution derived by conventional reasoning shall fall within the protection scope of the present invention.

[0032] The materials used in the present invention are as follows:

[0033] Polyamide: PA12, Wanhua Chemical

[0034] Polyamide: PA1012, Shandong Dongchen Engineering Plastics

[0035] Polyamide: PA612, Shandong Dongchen Engineering Plastics

[0036] Polypropylene 1: Random copolymer polypropylene, MFR 0.3g / 10min, ExxonMobil

[0037] Polypropylene 2: Random copolymer polypropylene, MFR 2.5g / 10min, ExxonMobil

[0038] Polypropylene 3: Random copolymer polypropylene, MFR 60g / 10min, ExxonMobil

[0039] Polypropylene 4: Homopolymer polypropylene, MFR 0.5g / 10min, Sinopec

[0040] Polypropylene 5: Homopolymer polypropylene, MFR 30g / 10min, Sinopec

[0041] Compatibilizer 1: polyacrylamide, commercially available

[0042] Compatibilizer 2: Silane, KH560, commercially available

[0043] Toughness modifier: N413A, commercially available

[0044] Flexibility modifier: Proviplast 024, commercially available

[0045] Antioxidant 1: Copper salt, H3386, commercially available

[0046] Antioxidant 2: phenol, 1098, commercially available

[0047] Chain extender 1: ADR-4400, commercially available

[0048] Chain extender 2: dioxazoline, commercially available

[0049] Colorant: Commercially available

[0050] The material preparation method is as follows:

[0051] According to the specific embodiment described in Table 1 and the formula dosage (weight parts) of the comparative example in Table 2, the raw materials are weighed respectively, and the components except the liquid flexibility modifier are put into a high-speed mixer for mixing until uniformity to obtain a premix; then the obtained premix is ​​put into a twin-screw extruder for melt mixing, and the flexibility modifier adopts a liquid pump side feeding process for extrusion granulation. The extrusion temperature is 200-250°C, and the screw speed is set to 250-500rpm.

[0052] Product performance test method:

[0053] The particles obtained in the examples and comparative examples were dried in an oven at 100-110°C for 2-4 hours and then injection molded at 220-250°C. The mold temperature was controlled at 60-90°C. The relevant performance tests were carried out according to the following test methods. The test results are detailed in Tables 1 and 2.

[0054] (1) Tensile modulus: according to ISO 527 method, sample size 170*10*4mm, test speed 1mm / min;

[0055] (2) Tensile elongation at break: according to ISO 527 method, specimen size 170*10*4mm, test speed 50mm / min;

[0056] (3) Notched impact strength: according to ISO 179 / 1eA method, specimen size 80*10*4mm;

[0057] (4) Low-temperature notched impact strength: The specimen size is 80*10*4 mm. The specimen is placed in a -30°C freezer for 24 hours, then taken out immediately and tested according to ISO 179 / 1eA standard method. The test of a single specimen must be completed within 10 seconds.

[0058] (5) Heat aging resistance: 1) The performance (strength or elongation) of the injection molded specimens after conditioning in a laboratory environment is recorded as the pre-aging performance according to the standard test method; 2) After the standard test specimens are placed in a 150°C oven for 500 hours, they are conditioned in a laboratory environment (23°C, 50% RH) for 24 hours and tested by the standard method and recorded as the post-aging performance; 3) Performance retention rate = post-aging performance / pre-aging performance * 100%.

[0059] Table 1 Example composition ratio (weight parts) and performance test results

[0060]

[0061] Table 2 Comparative Example Group Distribution Ratio (Parts by Weight) and Performance Test Results

[0062]

[0063]

[0064] From the performance test results of Examples 1 to 10 in Table 1 and Comparative Examples 1 to 13 in Table 2, it can be clearly seen that the present invention, by introducing polypropylene into the flexible polyamide system, endows the polyamide composite material with excellent long-term heat aging resistance. The retention rate of notched impact strength after 150°C / 500h can be maintained at more than 70%, with the highest reaching more than 90%, and the retention rate of elongation at break can be maintained at more than 50%, with significant technical effects. However, only adding antioxidants and chain extenders (Comparative Examples 1 and 2) makes little contribution to improving the heat aging resistance of the flexible polyamide system. Moreover, polypropylene is only helpful for improving the heat aging resistance of the flexible polyamide system, and has almost no effect on improving the heat aging resistance of the non-flexible system (Comparative Example 12).

[0065] Compared with the silane coupling agent used in traditional modification (Comparative Examples 6 and 9), the synergistic combination of acrylamide compatibilizers makes the flexible long-chain polyamide material mixed and dispersed evenly, tightly combined, maintains excellent initial toughness and processing softness, and obtains excellent long-term heat aging resistance.

[0066] Chain extenders are optional. Adding a suitable chain extender can further improve some long-term heat aging resistance properties (Examples 1 and 10). However, inappropriate types and addition amounts will not work, but will deteriorate and damage flexibility (Comparative Examples 1 and 13).

[0067] Although the above embodiments provide a relatively detailed textual description of the design ideas of the present invention, these textual descriptions are only simple textual descriptions of the design ideas of the present invention, rather than limitations on the design ideas of the present invention. Any combination, addition or modification that does not exceed the design ideas of the present invention shall fall within the protection scope of the present invention.

Claims

1. A heat-resistant and aging-resistant flexible polyamide composite material, characterized in that: The invention comprises the following raw materials in parts by weight: Polyamide 45-83 parts; Polypropylene 5-15 parts; Compatibilizer 0.5-3 parts; 8-25 parts of toughness modifier; 3-15 parts of flexibility modifier; Antioxidant 0.1-2 parts; Chain extender 0-1 part.

2. The heat-aging-resistant flexible polyamide composite material according to claim 1, characterized in that: The polyamide is selected from one or more of PA11, PA12, PA610, PA612, PA1010, PA1012, PA1212, PA510, PA513, and PA515.

3. The heat-aging-resistant flexible polyamide composite material according to claim 1, characterized in that: The polypropylene is a composition of polypropylene A and polypropylene B; the polypropylene A is a random copolymer polypropylene, and its melt flow rate is 0.2-3g / 10min at 230°C / 2.16KG; the polypropylene B is a homopolymer polypropylene, and its melt flow rate is 0.2-3g / 10min at 230°C / 2.16KG; the weight ratio of the polypropylene A to the polypropylene B is 10:1-3:

1.

4. The heat-aging-resistant flexible polyamide composite material according to claim 1, characterized in that: The compatibilizer is polyacrylamide.

5. The heat-aging-resistant flexible polyamide composite material according to claim 1, characterized in that: The toughness modifier is any one of maleic anhydride grafted octene ethylene copolymer, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene, or a combination of two or more thereof.

6. The heat-aging-resistant flexible polyamide composite material according to claim 1, characterized in that: The flexibility modifier is any one of N-butylbenzenesulfonamide, dioctyl phthalate, dibutyl phthalate, bisphenol A bis(diphenyl phosphate)\resorcinol bis(diphenyl phosphate) or a combination of two or more thereof.

7. The heat-aging-resistant flexible polyamide composite material according to claim 1, characterized in that: The antioxidant is one or more of copper salt antioxidants, phosphate antioxidants, amine antioxidants, phenol antioxidants, and ester antioxidants.

8. The heat-aging-resistant flexible polyamide composite material according to claim 1, characterized in that: The chain extender is an epoxy chain extender.

9. The heat-aging-resistant flexible polyamide composite material according to claim 8, characterized in that: The chain extender is a copolymer of acrylic acid and styrene containing epoxy functional groups.

10. The method for preparing the heat-aging-resistant flexible polyamide composite material according to any one of claims 1 to 9, characterized in that: The steps are as follows: (1) weighing raw materials according to the dosage of the formula; (2) putting all components except the liquid flexibility modifier into a high-speed mixer and mixing them until they are uniform to obtain a premix; (3) then putting the obtained premix into a twin-screw extruder for melt mixing, and the flexibility modifier adopts a liquid pump side feeding process to perform extrusion granulation; wherein the extrusion temperature is 200-250°C, and the screw speed is set to 250-500rpm.

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