Top 10 Materials for Plastic Injection Molding
The names of plastic injection molding material sound like terms from chemistry class. Choosing the correct injection molding materials means understanding application requirements, which change between prototyping and production. Not everyone has a PHD in chemistry to choose a right material. When it comes to choosing injection molding materials, we need to consider many factors. The first thing is to understand the names and abbreviations of material, the advantages and disadvantages of chosen material, and the applications and grades. The most widely used injection molding materials include PMMA, ABS, PA, PC, PE, POM, PP, PS, TPE and TPU. This article will explain each injection molding materials.
PMMA
Acrylic which is also known as PPMA. PPMA is strong and clear. It is light weight and shatter resistant. As PMMA is clear, it has great optical clarity. It offers a high percentage of light to pass through.
PMMA is high tensile strength so it can withstand load. It does not absorb odors. During injection molding process, PMMA is able to be held to high tolerances. PMMA is sunlight and weather resistant so it is a great material being used in outdoor. PMMA will not degrade in water, it won’t release BPA which has bad effects on human health.
PMMA has limitations. Compared to glass, PMMA is more expensive. And the scratch is more readily. PMMA is stained by oils and gases easily. PMMA has a service temperature which is too low for some industrial applications. Injected molded PMMA is lack of strong solvent resistance and can be prone to stress cracking by heavy loads.
PMMA is widely used in making commodity products like window, solar panel, bathroom enclosures and some clear parts for art and lighting application.
ABS
Acrylonitrile butadiene styrene is also called ABS. It is an engineering-grade thermoplastic with low melting point. ABS is easy to mold. ABS products can be made in any color and with different textures and surface finishes. ABS has high strength and impact resistance.
ABS is strong and tough. It is inexpensive. ABS is heat resistant, oil resistant, acids resistant and alkalis resistant. Injection molded parts made from ABS products can be with a shiny and attractive finish. ABS products are tough even at very low temperatures.
ABS is not sunlight or weather resistant. It is not a good material for making outdoor application. When ABS is burned, it will generate smoke. ABS is not high friction resistant and solvent resistant in water.
Injection molded ABS is widely used in making electronic parts, headgear, plastic wall plate for electrical outlet and automotive parts, wheel covers, dashboard, consumer products, sport equipment, industrial fittings and more. ABS can be combined with glass fillers to add strength or with polycarbonate to make it be low-temperature impact resistant.
PA
Nylon polyamide is also called PA. It a group of materials which can be natural or synthetic? Nylon is always synthetic. Injection molding with nylon is challenging because of shrinkage and inadequate filling.
Nylon PA is tough and high heat resistant. It is high abrasion resistant, good fatigue resistant. It can dampen noise. Nylon PA is a good material for high friction and wear applications.
Nylon is not flame resistant and it can be burned quickly. Nylon can be degraded by sunlight, but it can be added with UV stabilizer to improve performance. Nylon is not resistant to strong acids and bases.
Nylon is widely used in making strong mechanical parts like bearing, bushings, gears, and slide. It is a good material in making casings and snap-fit closures, threaded inserts, jigs, fixtures and more. Nylon applications are ranging from toothbrushes to medical implants and electrical connectors. The four main grade of nylon include nylon 6/6, 11, 12 and 46. Nylon can be filled with glass for better mechanical strength.
PC
Polycarbonate is also called PC. Similar to PMMA, Pc is strong, tough and naturally transparent. When PC is being pigmented, it keeps its color over time and retains its strength.
PC is durable and much stronger than glass. It offers precise dimensional control with its mold shrinkage. PC is lightweight and has great properties to support light transmission.
As PC has BPA, injection molded PC is not good for food products or storage. PC injection molding need high processing temperatures which will make more expensive to mold. PC is not scratch resistant.
PC is widely used in making machinery guards, clear window, diffusers and light pipes. PC can be used to make clear mold for urethane and silicone casting.
PC can be filled with glass or ABS to increase impact resistance. Some grade of PC has stainless steel fiber.
PE
PE which includes HDPE, PEHD, LDPE, PET, PETE is the most commonly used plastic in the world. HDPE and LDPE are chemical resistant but they have differences in hardness, flexibility, melting point and optical transparency.
HDPE, LDPE and PET are inexpensive. They are moisture and chemical resistant. Compared to HDPE, LDPE is softer and more flexible. PET is can be as transparent as glass.
PE is not UV resistant and not able to withstand high service temperature. HDPE is difficult to mold if the thickness is less than 0,02 inches. It is hard to achieve close tolerances with injection molded LDPE. PET can absorb water and need resin during which will increase the production.
PE is widely used to make bottle, plastic films. But these products are not injection molded but blow molding. Application of injection molded PE are toys, toolboxes, electronic wire, cable insulator and more.
POM
Polyoxymethylene is also called POM. It is low frication, high stiff, and dimensional stability. POM is naturally opaque and white as it has a highly crystalline structure. POM has great rigidity, thermal stability and low coefficient of frication. It has low water absorption. POM is chemical resistant.
POM has low impact strength and high rate of thermal expansion. POM injection mold has high shrinkage. POM is not UV light resistant. POM offer high hardness and tensile strength.
POM is widely used for making bearing, gears, conveyor belts, pulley wheel, fasteners, eyeglass frames and more. POM reinforced with fiberglass or minerals are strong and stiff.
PP
Polypropylene is also called PP. It has similar properties to PE. But compared to PE, PP is softer and more heat resistant. The density of PP changes with fillers. Pure PP has the lowest density.
PP has good chemical resistance, it can retain the shape after torsion and bending. PP has high melting point. It will not degrade even in water.
It is difficult to bond and paint PP. Pigments can be added to color PP.
PP is widely used in making consumer, commercial and industrial applications like toy, storage containers, packaging and more.
PS
Polystyrene is a common plastic which comes in GPPS and HIPS. Compared to HIPS, GPPS is brittle and less dimensional stable. GPPS has a glass-like clarity and HIPS is opaque. GPPS and HIPS are suitable for injection molding due to their predictable and uniform shrinkage.
PS is inexpensive, lightweight and moisture resistant. It is also gamma radiation resistant. It is widely used to sterilized medial devices. Injection molding PS is diluted acids and bases resistant.
PS is flammable. Injection PS is recyclable but it is not biodegradable.
PS is widely used in medical, optical, electrical and electronic applications. HIPS is widely used with application and equipment because its high impact strength. Injection molded GPPS is widely used in making toys, cases, container, trays and more.
TPE
Thermoplastic elastomer is also called TPE. Thermoplastic rubber is also called TPR. TPE as similar properties and performance of rubber. TPR has great elasticity. TPE is recyclable. Other recycled materials can be mixed together to make TPE.
TPE can be stretched. It can return to its original shape. TPE has short molding cycles. TPE is easier and inexpensive to mold than LSR.
TPE is widely used in footwear, medical devices, auto parts ad pet parts like weather seal, shock dust boots, breathing tubes, values, catheter and more.
TPU
Thermoplastic polyurethane is also called TPU. TPU has a rubber-like elasticity. Injection molded TPU has a high durometer which can be sued as a replacement for rubber. TPU is better for extreme temperature. TPUS is chemical resistant.
TPU is abrasion resistant, chemical resistant, greases resistant, oil resistant and high temperature resistant.
TPU lacks flexibility. TPU is expensive and need to be dried before processing.
TPU is widely used in footwear, gasket, sporting products and more.
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