Inventory: Application of engineering plastics and special plastics in automotive interior and exterior parts
Automotive plastics have many advantages that traditional materials do not have. They are mainly characterized by light weight, good decorative appearance, various practical application functions, good physical and chemical properties, easy processing and molding, energy conservation, sustainable use, etc. aspect. Engineering plastics Engineering plastics are widely used in the automotive field due to their good comprehensive mechanical properties. In this paper, polyamide (PA), polymethacrylate (PMMA), polyoxymethylene (POM), polyamide (PU) are mainly introduced. ), polycarbonate (PC). PA Polyamide, commonly known as nylon, is widely used in industrial applications. PA6, PA66 and PA610 are commonly used. PA is easy to print, easy to dye, excellent in electrical properties; resistant to chemicals and oil. The mechanical commonality is tough, both have high surface hardness, good tensile strength, good impact resistance, fatigue resistance, folding resistance and stress crack resistance. The tensile strength of PA changes with temperature and moisture absorption, so water is a plasticizer for PA. After adding glass fiber, its tensile and compressive strength can be increased by about 2 times, and the temperature resistance is also improved. PA itself The wear resistance is very high, so it can work without lubrication. The disadvantages of PA are poor acid resistance, poor light resistance, and poor stain resistance. Due to the influence of thermal expansion and water absorption, the dimensional stability of the workpiece is poor, and the shrinkage rate is 1-2%. It is necessary to pay attention to the dimensional change of moisture absorption after molding. The water absorption rate is 100%, and it can absorb 8% when it is saturated with moisture absorption. The suitable wall thickness is 2 to 3.5 mm. Injection molding performance: PA has strong water absorption and strong water absorption due to the presence of amide group. Therefore, it should be fully dried during injection molding, generally drying at 120 ° C for 3-4 hours; PA viscosity is small, flow speed is fast, to prevent shot If the mouth is flowing, a self-locking nozzle or a nylon-specific nozzle should be used. At the same time, pay attention to the accuracy of the mold. Applications: PA is mainly used in the automotive industry to manufacture hoses (brake hoses, fuel pipes), combustion oil filters, air filters, oil filters, water pump housings, water pump impellers, fans, brake fluid tanks, power Steering tank, white leaf window, headlight shell, seat belt. PMMA Polymethacrylate, commonly known as plexiglass, is resistant to outdoor aging, has excellent light transmission, and does not affect its transparency. It can still pass 92% of sunlight after 240 hours of accelerated aging of light, outdoor There are still 89% in the decade and 78.5% in the ultraviolet. High mechanical strength, certain cold resistance, corrosion resistance, good insulation performance, stable size, easy to form, brittle, easy to melt in organic solvents, insufficient surface hardness, easy to scratch and fluff. Suitable plastic products: transparent structural parts with a certain strength requirement. Injection performance: PMMA has a moisture absorption rate of 0.3%. It must be dried before injection. It is usually dried at 80 °C for 2 to 4 hours. The melt temperature during injection is 240 to 270 °C, and the mold temperature should be controlled at 35 to 70 °C. PMMA is widely used in automotive lighting signs, door glass and lamp glass covers due to its good light transmission properties. Toyota Corolla taillights with PMMA POM POM, commonly known as plastic steel, tensile strength, impact toughness, rigidity and fatigue strength, high creep resistance, good dimensional stability, low water absorption, small friction, excellent friction and wear resistance, high temperature and The water is still very rigid and has the same chemical resistance as PA, but it is cheaper, resistant to repeated twisting and has outstanding resilience. It can be used for a long time between -40 degrees Celsius and 100 degrees Celsius. The shortcomings of POM are: it is susceptible to strong acid corrosion, high temperature resistance and poor thermal stability. Shrinkage rate 2-3.5% Suitable wall thickness: 1.5-2.5mm. Injection molding performance: POM has obvious melting point, melting at 175 °C, decomposition at 240 °C, general processing temperature is 190 °C ~ 220 °C, its processing range is very narrow; POM does not absorb water, generally does not need to be dried during injection molding However, the product with high quality requirements can be dried at 60 ° C for 1 to 2 hours; the temperature should not be too high, otherwise the dyed product will be discolored; its acid resistance is poor, and it can not be dyed with acid dye. Applications: POM uses and manufactures instrument panel glove box accessories, various valves (drain valves, air conditioner valves, etc.), various impellers (water pump impellers, heater blades, oil pump wheels, etc.) and various electrical switches. And small gears on the electrical instrument, various handles and door pins. PC Polycarbonate, with outstanding impact toughness and creep resistance, good heat resistance, good cold resistance, embrittlement temperature of -100 ° C, bending strength equivalent to nylon, and high elongation and elasticity Modulus, but fatigue strength is less than nylon 66. Low water absorption, low shrinkage and good dimensional stability. The wear resistance is comparable to that of nylon and has a certain corrosion resistance, but the molding conditions are high. Good weather resistance, long-term application under high temperature and high load conditions, but can not be used under wet temperature, poor solvent resistance, stress cracking, and poor fatigue strength. The shrinkage rate is 0.5-0.7%, and the suitable wall thickness is 2-3.5 mm. The addition of PC to glass fiber can improve its shrinkage, mechanical strength and temperature resistance. The long-term use of steel at 100 °C will increase, and the internal stress can be improved by annealing. Injection molding performance: PC has obvious melting point, melting at 220 ° C, decomposition at 350 ° C, the general processing temperature is 250 ° C ~ 320 ° C; it absorbs water, a small amount of moisture can cause it to decompose at high temperatures, must be baked during injection molding Dry, drying temperature can be dried at 120 °C for 4 to 5 hours; PC material has a high melt viscosity, which requires a large pressure during injection; PC can be used to improve the mold with mold temperature if the conditions permit. Temperature to reduce the residual stress of the product; PC shrinkage rate is independent of the processing conditions and the wall thickness of the product, and its longitudinal and transverse shrinkage ratio is relatively close, so it can be processed into a highly accurate product; its shrinkage rate is 0.5%. . The main synthetic PC-ABS: PC-ABS is a blending material of PC and ABS, which is usually supplied in the form of pellets after blending. If only two materials are simply mixed, direct injection molding, the effect is very poor, there will be stratification; PC has the advantage of being rigid and tough, the disadvantage is stress cracking, high viscosity; ABS has the advantage of good fluidity, but the surface The hardness is low; the blended material PC-ABS retains the advantages of both; PC-ABS has high surface hardness, high rigidity and toughness, and high resistance to stress cracking; its mechanical properties Between the two. Applications: PC is mainly used in the automotive field to manufacture lampshades, left and right wheel cover guards, instrument baffle body (PC+ABS), left and right wind frame cover, middle wind frame cover (PC+ABS), rear bumper cushion. PU Polyurethane is generally classified into a rigid polyurethane and a flexible polyurethane depending on the polymerization product. The rigid polyurethane has high strength, good toughness, good heat insulation, good waterproof effect, simple molding process and high production efficiency; flexible polyurethane has good elasticity, good sound absorption effect, aging resistance and chemical resistance, etc. Mechanical properties far exceed those of PVC. The polymerization of polyurethane is very convenient, not only can be carried out under normal temperature and normal pressure conditions, but also can be directly foamed or sprayed, repaired, etc. after on-site polymerization. Polyurethane foam is widely used in automotive interiors and vibration absorbing parts, such as coating materials, polyurethane rigid plastic sheets, polyurethane elastomers, seat soft foam materials, decorative parts, sofa leather, roof accessories; It is a variety of soft and rigid polyurethane foam materials, it has vibration isolation, sound insulation, noise reduction, thermal insulation; PU can also be made into automotive polyurethane coatings, adhesives, sealants and so on. The PU on the car represents the instrument panel, rear view mirror, bumper, seat cushion, headrest, steering wheel, instrument panel anti-vibration pad, pillar trim, front roof lining, window frame, ceiling and side top Frame decoration, door lining, sun visor, rear top frame decoration, etc. Special plastic glass fiber reinforced plastic Glass fiber reinforced plastic is based on the original pure plastic, adding glass fiber and other additives to improve the use of the material. In general, most of the glass fiber reinforced materials are used in structural parts of the product, which is a structural engineering material; for example: PP, ABS, PA66, PA6, PC, POM. advantage: 1 After the glass fiber is reinforced, the glass fiber is a high temperature resistant material, so the heat resistant temperature of the reinforced plastic is much higher than before the glass fiber is added, especially the nylon plastic; 2 Limiting the mutual movement between the polymer chains of plastics, so the shrinkage rate of the reinforced plastic is greatly reduced, and the rigidity is also greatly improved; 3 reinforced plastics will not stress cracking, and the impact resistance of plastics will increase a lot; 4 Glass fiber is a high-strength material, which also greatly increases the strength of the plastic (tensile strength, compressive strength, bending strength are improved a lot); 5 Due to the addition of glass fiber and other additives, the flammability of reinforced plastics is much reduced, and most materials cannot be ignited. Disadvantages: 1 It is transparent before it is added to the glass fiber, and it will become opaque; 2 The toughness of the plastic is reduced and the brittleness is increased; 3 The melt viscosity of all materials increases, the fluidity deteriorates, and the injection pressure is much higher than that without glass fiber; 4 Poor fluidity, for normal injection molding, the injection temperature of all reinforced plastics is increased by 10 ° C - 30 ° C before adding glass fiber; 5 The hygroscopic property of the reinforced plastic is greatly enhanced. The original pure plastic will not become absorbent when it absorbs water. Therefore, it must be dried during injection molding; 6 During the injection molding process, the glass fiber can enter the surface of the plastic product, making the surface of the product become rough and spotted (in order to achieve a higher surface quality, it is better to use a mold temperature machine to heat the mold during injection molding, so that the plastic polymer enters The surface of the product, but can not achieve the appearance quality of pure plastic); 7 Glass fiber is a very hard material. It is a highly corrosive gas after high temperature volatilization. It is very wear and corrosion on the screw and injection mold of the injection molding machine. Therefore, the mold and injection molding machine using such materials are produced. Attention should be paid to the surface anti-corrosion treatment and surface hardness treatment of the equipment. Representative of glass fiber reinforced materials, glass fiber reinforced plastic / composite materials in the automotive industry: Body parts: including body shell, hood hard roof, sunroof, door, radiator grille, headlight reflector, front and rear bumpers, etc. This is the main direction of application of FRP/composite materials in automobiles. It is mainly aimed at adapting to the needs of streamlined design and high quality requirements of the body. The current development and application potential is huge. The material of this part is mainly made of glass fiber reinforced thermosetting plastic. Typical molding processes include: SMC/BMC, RTM and hand paste/jetting. Structural parts: including front end brackets, bumper frames, seat frames, floors, etc., the purpose is to improve the design freedom, versatility and integrity of the parts. Mainly use high-strength SMC, GMT, LFT and other materials. Functional parts: Its main features are high temperature resistance and oil corrosion resistance, mainly based on engine and engine peripheral components. Such as: engine valve cover, intake manifold, oil sump, air filter cover, gear chamber cover, air hood, intake pipe guard, fan blade, fan air guide, heater cover, water tank parts, Outlet casing, pump turbine, engine insulation board, etc. The main process materials are: SMC/BMC, RTM, GMT and glass fiber reinforced nylon. On behalf of car companies and models: Plastics for structural parts of cars and interior and exterior decorative parts and their application examples: The Disposable Medical Face Mask is made of 2 layers non-woven fabric and 1 layer melt-blown non-woven fabric, the disposable medical mouth Face Mask has a stronger filtering effect and is comfortable and breathable to wear. This kind of facial mask can block bacteria, dust, and pollen effectively. 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