Selecting the right plastic material for injection molding your parts may not be very straight forward. Depending on your product, industry, end user, and regulations in that field (if any), there are a variety of options to choose from. No matter how good your product idea and how great the design intent, specifying the wrong plastic material to the perfect product will always backfire. A good product should always function as designed, be robust enough to withstand normal (and abnormal abuse in some cases) abuse, and deliver the performance safely to the end user.
Narrowing down the extensive list of injection molding materials can seem like a formidable task. To make your life easier, we’ve prepared a list that outlines the benefits and applications of some of the most commonly injection molded plastics. By choosing the right material, you can improve the form, fit, performance, and function of your molded parts.
ABS (Acrylonitrile Butadiene Styrene)
Summary: Acrylonitrile-butadiene-styrene (ABS) is the largest-volume engineering thermoplastic resin, offering an excellent balance of heat, chemical, and impact resistance with superior processing versatility. Large-volume applications for ABS resins include appliance parts, electronic/electrical, and transportation (automotive) end uses. ABS resins are frequently used in polymer blends for many different applications, to achieve the best of all properties from the combined product.
ABS is a tough, impact-resistant plastic that is widely used across many different industries. It has low shrink and high dimensional stability, and it has good resistance to acids and bases. ABS is a good choice for handheld consumer devices. It’s also relatively inexpensive.
Keep in Mind: ABS injection molded parts may have visible lines and sinks in thicker areas. Rib design can be optimized as well as using an a blend of PC/ABS to reduce these risks.
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ABS/PC
Summary: ABS/PC is a thermoplastic resin commonly used for injection molding applications. Acrylonitrile butadiene styrene polymer (ABS) blended with polycarbonate (PC) resin offers a favorable combination of mechanical and thermal properties. It exhibits high toughness even at cold temperatures, rigidity, dimensional stability, easy processing, good color stability in indoor lighting, and good heat resistance.
PC/ABS alloys process with the ease of ABS materials, yet have a toughness similar to polycarbonate materials. The high heat distortion of the blend is an improvement over ABS, while the low-temperature impact resistance gives it an advantage over polycarbonate. PC/ABS is used in the automotive, consumer electronics, and telecom. industries, and more…
Keep in Mind: PC/ABS is easy to process, it reduces think cross sectional molding issues that are found in PC or ABS alone. Lower cost than PC alone. Has good impact strength and toughness – even at low temperatures. It possess good dimensional stability, good rigidity, thermal stability and color stability. Some limitation including poor chemical resistance, poor weather-ability, and low fatigue endurance.
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PC (Polycarbonate)
Summary: Polycarbonate (PC) is a engineering thermoplastic resin used for injection molding and extrusion applications. It posses great mechanical including high impact strength and good dimensional stability, electrical, thermal (heat resistant), optical properties, as well as light weight (compared to glass).
If you’ve ever walked into a bank or a convenience store in a partially dangerous area and saw “bullet-proof” glass, that is PC. It’s known for glass like transparency, with much stronger properties. Other applications include automotive, aircraft, security components, lighting, cell phones, medical, electrical and medical devices.
Keep in Mind: Additionally, thicker cross sections of PC may show bubbles, sinks, and hallow internals. PC parts possess poor chemical and scratch resistance. Abrasion resistance can be achieved with the application of a hard coating, like on eye-wear like reading/sunglasses and automotive applications like headlights. If transparency is not a deal breaker, PC/ABS blend (see above) is a good option. Acrylic (PMMA) is another option if toughness is not required, and post processing is undesired. Another major disadvantage is the cost, it is fairly expensive.
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Nylons (PA or PPA Aliphatic Polyamides)
Summary: There are many Nylon (PA) options including 4, 6/6, 6, 6/10, 6/12, 12, etc… Nylon is a tough abrasion resistant thermoplastic resin typically used for injection molding applications.
Nylon 6 has improved surface appearance, creep resistance, and processing compared to nylon 6/6.
Once re-enforced, like glass reinforced nylons, provide stiffness retention for automotive, appliance, construction, and computer components.
Nylon 6 is used in applications where toughness, lubricity, and wear are important, such as gear wheels (thin walled parts), bearings, camera components, engine bay parts, and pump components. While Nylon 6/12 has improved impact strength.
Some of the advantages of nylon is light weight with good mechanical properties and extreme toughness. Good impact-absorbing characteristics, remarkable self-lubrication and abrasion resistance across a wide temperature range. Excellent chemical resistance (see exceptions below)
Keep in Mind: Nylon has high water absorption, poor chemical resistance to strong acids and bases. Non-linear shrink make cause warpage.
PPSU (Polyphenylsulfone)
Summary: PPSU is very tough, heat resistant, and is very stable dimensionally at higher temperatures. Polyphenylsulfone is resistance to base acids and alkalis, as well as being resistant to radiation sterilization, it is a great choice for sterilization trays on medical devices. It is used on aircraft interior components, and connectors.
Keep in Mind: PPSU doesn’t fair too well with hydrocarbons and organic solvents. Keep an eye out on sinks, voids, and bubbles in thick cross sectional areas.
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Acetal or POM (Polyoxymethylene)
Summary: POM is referred to as acetal. It has among the stiffest and strongest characteristics of any thermoplastic. Acetal is commonly used in high fatigue, high wear, and high chemical exposure applications and where dimensional stability is key. Acetal maintains great lubricity and resistance to hydrocarbons, organic solvents, making it ideal for replacing higher strength metals like gears and chain guides. Especially given how easy it is to machine and fabricate, withstanding higher temperatures, uninterrupted use at 85 degrees C.
Additionally acetal has low moisture absorption, creep and fatigue resistant. It is used in the automotive, food processing, electronics production, and in food production processing plants. Applications are vast including pistons, valves, timing screws, wear strips, shaver cartridges, automotive door handles, seat belt components, gas tank caps, manifolds, and more…
Keep in Mind: Even though Acetal is immensely resistant to solvents and strong bases, it is fairly weak under tough mineral acids. Designers should allow for shrink when designing acetal components, keeping uniform part wall thickness. Depending on the quantities needed, low quantity parts can be machined instead of molded to achieve high visual quality if needed.
Polypropylene (PP)
Summary: Polypropylene (PP) is a very cost effective thermoplastic that offers outstanding mechanical (tensile), electrical, thermal properties. any other thermoplastic. The low density of PP makes it super light and a go to plastic for packaging. Having a high melting temperatures and high distortion temp, it is a great choice for hot fill applications.
PP is very resistant to organic solvents, degreasing chemicals, corrosives, and electrolytic interactions. It is used for battery cases, acid tanks, machining tubes, ducts, and chemical scrub stations. PP is virtually super low maintenance, it wipes clean, machinable, and is even weldable.
Keep in Mind: Polypropylene suffers from lower impact strength, especially at lower temperatures. It is also hard to paint and not easy to adhere to other objects.
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PEEK (Polyether Ether Ketone)
Summary: PEEK is a high performance engineering thermoplastic. It is very strong, rigid, with low moisture absorption. As of this writing, PEEK the highest tensile strength in the plastics family. This thermoplastic can be continuously used at an impressive 250 degrees C without being distorted or compromised. PEEK is also highly chemical resistant.
No surprise it is used in the aerospace, medical, automotive industries, and oil & glass industries. PEEK is used to produce wires, cables, conveyer components, rollers, wear pants, automotive engine parts, retaining rims, and bearings.
Keep in Mind: High performance of PEEK comes with a high price. Alternatives such as PPSU (Polyphenylsulfone) and PEI (Polyetherimide) are available, with lower performance and corresponding cost.
PEI (Polyetherimide)
Summary: Polyetherimide (PEI) has exceptional rigidity and strength at high temperatures. is valuable in the medical, electronics and other fields that demand exceptional strength and rigidity in high-heat applications. The amber, high performance polymer offers excellent dimensional stability, combined with broad chemical resistance.
PEI is ideal for hot air and water environments and is very hydrolitaclly stable with excellent property retention.
PEI has high-performance electrical properties and resistance to heat for continuous periods of time, without loss of rigidity and performance. A frequent metal substitute. PEI has High-impact strength, it is creep and radiation resistant, FDA compliant, is sterilizable with UV and gamma radiation, is glass reinforceable if needed. As a result of its’ flame retardant properties makes it ideal for the aerospace industry. PEI has high strength and dimensional stability. It is also used in medical devices, electrical enclosures, automotive applications, as well as for food handling serving, electrical lighting and HVAC applications.
Keep in Mind: Cost of PEI is very high. Keep that in mind for your design applications, as it may make more sense to go with solution like PPSU instead.
PBT (Polybutylene Terephthalate)
Summary: PBT is tough and flexible in non-glass filled form. It provides great electrical properties for automotive and power parts. PBT is commonly glass filled, providing moderate to high strength depending on the fill percentage. PBT is resistance to a variety of solvents, fuels, oils, and doesn’t retain flavors. PBT is a great choice for household appliances including toasters, coffee makers, vacuum cleaners, hair dryers, switch gear for electrical cooking equipment, as well as other components like cams and gears.
Keep in Mind: PBT with glass fill has poor resistance to bases, acids, and hydrocarbons. Additionally, parts maybe hard to fill and in many cases warp.
Options and Info
Selecting the right plastic material for injection molding your parts has many implications that will influence the outcome of your product. We will help you with narrowing down plastics, metals, elastomers, and composite materials to fit your product and end user requirements.
To discuss the best material for injection molding your product, create designs, prototypes, contact REQUEST A QUOTE or Call 1-424-206-3909 now.
Results driven degreed Engineer from the University of Michigan with 16 years professional experience split between Design, Stress Analysis, Testing, Project Engineering, Project Management, Product Launch, and Production Support in a variety of Industries such as Aerospace, Automotive, Consumer Products, Electronic Products, and Off-Highway Machinery. Worked at major companies like Dow Chemical, General Motor, Delphi, Kubota Corporation, Zodiac Aerospace, and others. Have since worked on hundreds of independent projects from conception to launch.
Project involvement from concept, design, patenting, prototyping, testing, tooling, production, and timely customer delivery. Over 15000 hours combined design experience in surface and solid modeling in CATIA, Solid Works, Autodesk Inventor, Fusion 360, Pro E and more. As an inventor and multiple patent holder, my goal is to help customers design, test, and produce the highest quality products, and successfully launch them to market. Contact me here.
