Engineering plastics and specialty plastics for automotive applications

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2017-12-19

Automotive plastic has many advantages that traditional materials did not have in the past, mainly in the light weight, good decorative appearance, a variety of practical applications, with good physical and chemical properties, easy molding, energy conservation, sustainable use, etc. aspect. plastic mould

Engineering plastic
Due to its good mechanical properties, engineering plastics are also widely used in the automotive industry including plastic mould industry. In this paper, polyamides (PA), polymethacrylates (PMMA), polyoxymethylene (POM), polyamides ), Polycarbonate (PC).
PA
Polyamide, commonly known as nylon, is widely used in industrial applications. PA6, PA66 and PA610 are commonly used. PA easy to print, easy to dye, excellent electrical properties; resistance to chemicals, oil corrosion. Mechanical commonality is tough, have a high surface hardness, good tensile strength, impact resistance, fatigue resistance, folding, stress cracking. PA tensile strength changes with temperature and moisture absorption, so the water is PA plasticizer, after joining the glass fiber tensile strength can be increased by about 2 times the temperature capability also increased accordingly PA itself The wear resistance is very high, so can work without lubrication.
Disadvantages of PA Acid resistance is poor, poor light resistance, poor resistance to pollution. Due to thermal expansion and water absorption, poor dimensional stability of parts, shrinkage of 1 to 2%, need to pay attention to dimensional changes after moisture absorption. 100% water absorption, relative humidity absorption can absorb 8%, suitable wall thickness: 2 ~ 3.5mm.
Injection Properties: PA due to the presence of amido, strong water absorption and strong water absorption, therefore, in the injection plastic mould should be fully dried, generally dried at 120 ℃ 3-4 hours; PA viscosity is small, fast flow, in order to prevent the shot Mouth flowery, self-locking nozzle or nylon nozzle should be used. At the same time, pay attention to mold accuracy.
Applications: PA is mainly used in the automotive industry for the manufacture of hoses (brake hoses, fuel lines), combustion oil filters, air filters, oil filters, water pump housings, pump impellers, fans, brake fluid tanks, Turn to tank, white window, front headlight shell, seat belt.
PMMA
Polymethacrylate, commonly known as plexiglass, is resistant to outdoor aging and has excellent light transmission, exposure to the sun without affecting its transparency. It can still transmit 92% of sunlight after 240 hours of accelerated light aging. There are still 89% in ten years and 78.5% of ultraviolet rays. High mechanical strength, a certain degree of cold resistance, corrosion resistance, good insulation properties, dimensional stability, easy to shape, the quality of more brittle, easy to melt in organic solvents, the surface hardness is not enough, easy to scratch the fluff. Suitable plastic products: a transparent structure with a certain strength requirements.
Injection performance: PMMA moisture absorption rate of 0.3%, must be dried before injection, usually about 80 ℃ drying 2 ~ 4h; injection molding melt temperature at 240 ~ 270 ℃, mold temperature to be controlled at 35 ~ 70 ℃.
PMMA is widely used in automotive lighting signs, door glass and lamp glass due to its good light transmission properties.
POM
Polyoxymethylene, commonly known as steel, tensile strength, impact toughness, rigidity and fatigue strength, high creep resistance, good dimensional stability, small water absorption, small friction, excellent friction and wear resistance, high temperature and Water is still a lot of rigidity, chemical resistance with the same PA, but the lower the price, resistance to repeated distortion, a prominent resilience. Long-term use can be -40 degrees Celsius -100 degrees Celsius. The downside of POM is: susceptible to strong acid corrosion, high temperature, poor thermal stability. Shrinkage 2-3.5% Appropriate wall thickness: 1.5-2.5mm.
Injection Molding Properties: POM has obvious melting point, melted at 175 ℃ and decomposed at 240 ℃. The processing temperature is generally from 190 ℃ to 220 ℃. Its processing range is very narrow. POM is not water-absorbing. Generally, it does not need to be dried during injection molding , But high quality products, you can use 60 ℃ drying 1 to 2 hours; the temperature can not be too high, otherwise non-staining products will change color; it is poor acid resistance, can not be dyed with acid dyes.
Applications: POM in the car with the manufacture of instrument panel glove box accessories, all kinds of valves (drainage valves, air conditioners valves, etc.), all kinds of impeller (pump impeller, air heater impeller, pump wheel, etc.), all kinds of electrical switches And electrical instruments on the pinion, all kinds of handles and door pins, and so on.
PC
Polycarbonate, with outstanding impact toughness and creep resistance, good heat resistance, cold resistance is also very good, embrittlement temperature of -100 ℃, bending strength and nylon, and have high elongation and flexibility Modulus, but fatigue less than nylon 66. Low water absorption, small shrinkage, good dimensional stability. Abrasion resistance and nylon quite, and have a certain anti-corrosion ability, but the molding conditions demanding. Good weatherability, long-term application under high temperature and high load conditions, but not in wet temperature, poor solvent resistance, stress cracking phenomenon, poor fatigue strength. Shrinkage of 0.5-0.7%, a suitable wall thickness of 2-3.5mm. PC to join the glass fiber can improve its shrinkage, mechanical strength and temperature resistance, long-term use of steel at about 100 ℃ will increase annealing can be used to improve internal stress.
Injection Molding Performance: PC has a clear melting point, melting at 220 ℃, 350 ℃ decomposition, the general processing temperature is 250 ℃ ~ 320 ℃; it absorbs water, a small amount of moisture can cause it to decompose at high temperature, the injection must be baked Drying, drying temperature can be dried with 120 ℃ 4 ~ 5 hours; PC material melt viscosity, the injection requires a larger pressure; PC processing, if conditions allow, you can use the mold temperature to improve the mold Temperature, to reduce the residual stress of the product; PC shrinkage and processing conditions and product wall thickness has nothing to do with its vertical and horizontal shrinkage is relatively close, so that it can be processed into high precision products; its shrinkage of 0.5% .
Main Synthetic PC-abs: PC-ABS is a blend of PC and ABS, usually blended to make pellets. If only two kinds of materials simply mixed, direct injection, the effect is poor, there will be stratification; PC\'s advantage is just and tough, the disadvantage is the stress cracking, viscosity; ABS has the advantage of good fluidity, but the surface PC-ABS has the advantages of retaining both; PC-ABS has a high surface hardness, high rigidity and toughness, but also has high resistance to stress cracking; its mechanical properties Between the two.
Applications: PC is mainly used in the field of automotive manufacturing shade, left and right wheel guard, instrument bezel body (PC + ABS), left and right windscreen cover, middle windscreen cover (PC + ABS), rear bumper cushions.
PU
Polyurethane, according to the different polymerization products, commonly divided into rigid polyurethane and flexible polyurethane. Rigid polyurethane has high strength, good toughness, good heat insulation, good water-proof effect, simple molding process and high production efficiency. The flexible polyurethane has good elasticity, good sound-absorbing effect, anti-aging performance and chemical resistance. Mechanical properties far more than pvc and other materials. Polyurethane is very convenient for polymerization. It can not only be polymerized under normal temperature and pressure conditions, but also can be directly foamed or sprayed or repaired after on-site polymerization.
Polyurethane foam is widely used in automotive interior and vibration-absorbing parts such as coating materials, polyurethane rigid plastic sheets, polyurethane elastomers, seat soft foams, upholstery, sofa leather, car roof accessories; Is a variety of soft and rigid polyurethane foam, which has vibration isolation, noise, noise reduction, thermal insulation; PU can also be made of automotive polyurethane coatings, adhesives, sealants and so on. Automotive PU stands for dashboards, rear-view mirrors, bumpers, seat cushions, headrests, steering wheels, dash pads, pillar trim, front roof lining, window frames, roofs and side roofs Frame decoration, door linings, sun visors, after the top shelf decoration.
Special plastic glass fiber reinforced plastic

Glass fiber reinforced plastic is based on the original pure plastic mould, glass fiber and other additives, thereby increasing the use of materials. In general, most of the glass fiber reinforced materials used in structural plastic mould parts of the product is a structural engineering materials; such as: PP, ABS, PA66, PA6, PC, POM.

What is engineering plastic Die casting injection mold temperature in the plastic auxiliary machine sector is crucial

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