Introduction: injection molding process is famous for its wide range of applications. One of the reasons for its success is the many different plastic injection molding material that can be used in injection molding.

In this article, we’re going to talk about some of the most common plastics used in injection molding. We’ll go over what they are, what they’re good for, what they’re not so good for, and what they’re used for. We’ll also talk about the different grades of each plastic.

Acrylic (PMMA)

PMMA Definition

PMMA, or acrylic, is a strong, transparent thermoplastic that is a lighter weight, shatterproof alternative to glass. Because PMMA is transparent and has excellent optical clarity, it lets a lot of light through.

PMMA Definition

Acrylic resin is strong, can handle weight, doesn’t smell, and can be made into things that are exactly the right size. It also doesn’t get ruined by the sun or the weather, so you can use it outside. It doesn’t break down when it gets wet, so it doesn’t let out bisphenol A (BPA), which is a chemical in a lot of plastics that’s bad for people.

Advantages of PMMA

Acrylic resin has some important limitations. They are more expensive than glass and are more susceptible to scratching. They are also easily stained by grease and oil. In addition, PMMA is used at too low a temperature for some industrial applications.

Injection molded acrylics lack strong solvent resistance and are susceptible to stress cracking under particularly heavy loads.

Disadvantages of PMMA

Acrylic resin has some important limitations. They are more expensive than glass and are more susceptible to scratching. They are also easily stained by grease and oil. In addition, PMMA is used at too low a temperature for some industrial applications.

Injection molded acrylics lack strong solvent resistance and are susceptible to stress cracking under particularly heavy loads.

PMMA Applications

Acrylics are used for windows, greenhouses, solar panels, bathroom enclosures, and other transparent stuff for buildings and lights.

PMMA Grades

The cheapest type of PMMA is general-purpose acrylic. It’s used for merchandise, not engineering applications. Sign-grade acrylic is 10 times stronger than general-purpose acrylic.

It’s great for outdoor signage because it lets light through. Marine-grade acrylic is resistant to damage from being in water all the time. Boat builders use it a lot.

Acrylonitrile Butadiene Styrene (ABS)

Definition of ABS

ABS is a thermoplastic that engineers love because it’s easy to mold and has a low melting point. It’s an opaque polymer that can be colored and has different textures and surface finishes. ABS is known for being strong and resistant to impact.

ABS Advantages

ABS has a lot of good things going for it. It’s tough, durable, and strong, which makes it useful in a lot of different industries. It’s got a high tensile strength and can take a hit.

Another thing that makes ABS injection molding very popular is its ductility, which allows it to be easily molded into different shapes. ABS’s ability to stick to other plastics makes it good for coating metals and other materials.ABS is tough, relatively cheap, and has good resistance to heat, oils .

acids, and alkalis. It’s got styrene in it, which makes injection molded parts look shiny and nice, and it’s got butadiene in it, which makes it tough even when it’s cold.

Disadvantages of ABS

ABS is not very resistant to sunlight or weather, so it’s not a good choice for outdoor applications. ABS also produces a lot of smoke when burned, has poor resistance to high friction, and doesn’t resist solvents like water.

ABS Applications

ABS plastic is used to make electronic parts and keys for keyboards, plastic siding to protect helmets, electrical outlets, and car parts like dashboards, hubcaps, and body parts. It’s also used for consumer goods, sports equipment, and industrial accessories.

ABS Grades

ABS can also be mixed with glass fillers for more strength, or with polycarbonate for better low-temperature impact resistance. Some suppliers make filled and unfilled ABS plastics.

Nylon Polyamide (PA)

PA Definition

Polyamides (PA) are a big group of materials that can be either natural or synthetic. However, nylon, a type of polyimide, is always synthetic. Injection molding nylon is hard because this polyamide tends to shrink and underfill.

Advantages of PA

Advantages of nylon PA include toughness and high heat resistance. It’s also got high wear resistance, good fatigue resistance, and it’s quiet. Injection molded nylon is good for high friction and wear applications because it has a low coefficient of friction.

Disadvantages of PA

Nylon doesn’t have flame retardancy, and it burns fast. But you can get flame retardant nylon. Nylon also doesn’t like sunlight, but you can add UV stabilizers to make it better. Nylon doesn’t like strong acids or bases either.

Applications of PA

Nylon is used in strong mechanical parts like bearings, bushings, gears, and slides. It’s also great for housings and snap closures, threaded inserts, power clasps, clamps and fixtures. Other applications range from toothbrushes and wheels to medical implants and electrical connectors.

PA Grades

There are four main grades of nylon: nylon 66, 11, 12, and 46. Each grade has slightly different mechanical properties.

Nylon 66 has a higher melting point and greater resistance to acids and can be used in chemical processing applications. 

Nylon 11 has a higher resistance to dimensional change because it has a higher resistance to moisture. It is used in outdoor applications.

Nylon 12 has the lowest melting point and is pretty good at not absorbing water.

Nylon 46 can handle higher temperatures than other nylons. It’s used in engines and transmissions.

You can add glass to nylon to make it stronger.

Polycarbonate (PC)

Definition of PC

PC plastics are strong, tough materials that are naturally transparent. They’re similar to PMMA, but PC keeps its physical properties over a wider temperature range. When tinted, PC keeps its color over time and keeps its strength.

Advantages of PC

Polycarbonate is one of the toughest plastic resins out there. It’s got a high resistance to impact. It’s also highly resistant to fire and heat, which makes it perfect for places where it gets really hot.

Polycarbonate is super tough and 250 times stronger than glass. With its predictable and uniform mold shrinkage, this injection molding material gives you precise dimensional control. PC plastic is also lightweight and has excellent optical properties to support light transmission.

Disadvantages of PC

Don’t use injection molded polycarbonate for food prep or storage because it has BPA. It also needs higher processing temperatures, which makes molding more expensive. Polycarbonate isn’t scratch-resistant either.

PC Applications

Polycarbonate is used for machine guards, clear or tinted windows, diffusers and light pipes for LEDs, and clear tubing. This material can also be used to produce clear molds for polyurethane and silicone castings.

Polycarbonate can be glass-filled and compounded with ABS to improve impact resistance. Some grades contain a relatively small percentage of stainless steel fibers.

Polyethylene (PE)

Definition of PE

Polyethylene is the most commonly used plastic in the world. There are three main types:

high density polyethylene (HDPE, PEHD) .

low density polyethylene (LDPE) .

Polyethylene terephthalate (PET, PETE) .

PE is the only commercial polymer that can be selected based on its density, and this measurement is important because it controls other material properties. Both HDPE and LDPE have useful properties such as chemical resistance, but they differ in their hardness, flexibility, melting point, and optical clarity. PET plastic is not defined by density.

Advantages of PE

HDPE, LDPE, and PET are all cheap plastics that are resistant to both moisture and chemicals. LDPE is softer and more flexible than HDPE, which is an opaque material. Like LDPE, PET can be as clear as glass. Engineers and designers like these materials because they offer a variety of options in optical clarity and other properties.

Disadvantages of PE

PE plastics are limited by poor UV resistance and can’t handle high service temperatures. HDPE parts with thicknesses less than 0.020 inches are tough to mold. It’s hard to hold tight tolerances with injection molded LDPE. PET absorbs a lot of water and needs resin drying, which adds to production costs.

PE Applications

PE plastics are most commonly used in baby bottles (HDPE), plastic film (LDPE), and water bottles (PET). However, these products are not injection molded. They are made using a different type of molding called blow molding. Examples of injection molded PE include children’s toys, tool boxes, wire and cable insulation, and medical device components.

PE Grades

PE plastics come in numbered grades, with higher numbers generally indicating higher density. For example, HDPE 500 has a higher density than HDPE 300. Both grades have higher densities than LDPE, which also uses a grade numbering system.

Polyoxymethylene (POM)

POM Definition

POM, also known as acetal, is an engineering plastic. It can be injection molded into parts that need low friction, high stiffness, and excellent dimensional stability. POM plastics are naturally opaque and white because they have a highly crystalline structure.

Advantages of POM

POM, also known as acetal, is a type of plastic that’s made by injection molding. It’s got a lot of great qualities, like being really stiff, not melting when it gets hot, and being slippery. It doesn’t soak up water and it’s good at not getting messed up by chemicalschemical resistance.

There are two main kinds of POM to pick from: homopolymer and copolymer. That means you can get acetal with different stuff mixed in to make it do different things.

Disadvantages of POM

POM is weak and expands a lot when it gets hot. It shrinks a lot when it cools down, and it doesn’t like the sun. POM plastics that are made from just one kind of stuff are harder and stronger. But all POM plastics (the ones made from just one kind of stuff and the ones made from more than one kind of stuff) can’t pass fire tests like UL 94.

Applications of POM

Because of its low coefficient of friction, injection molded POM is good for bearings, gears, conveyor belts, and pulleys. Other uses include fasteners, eyeglass frames, knife and gun parts, lock systems, and high-performance engineering parts.

POM Grades

POM comes in grades reinforced with glass fibers or minerals to make it stronger and stiffer. Compounds reinforced with these two materials give you a good mix of mechanical properties.

Polypropylene (PP)

PP Definition

Polypropylene (PP) is similar to polyethylene (PE) in many ways, but it’s stiffer and more heat resistant. It’s the second most commonly used plastic in the world. The density of polypropylene varies with fillers, but pure PP is the lowest density commercial plastic.

Advantages of PP

Polypropylene plastic is great at resisting chemicals and keeping its shape even when you twist or bend it. It also has a high melting point and doesn’t break down when it gets wet. You can recycle injection molded polypro (that’s what some people call this plastic) up to four times. Plus, you can mix recycled PP with other plastic materials.

Disadvantages of PP

PP is a plastic that breaks down in sunlight and burns easily. At temperatures above 100° C (212° F), it turns into chemicals that can hurt you, like benzene and toluene. It’s hard to color PP because it’s hard to stick to, but you can add color to it.

PP Applications

Polypropylene that is injection molded has many uses in the consumer, commercial, and industrial worlds. Some examples are toys for kids, containers for storage, sports equipment, packaging, appliances, and the bodies of power tools.

PP Grades

You can put glass fibers in PP to make it stronger, stiffer, and more stable. There are different kinds of PP with glass fibers in them. One kind is called high crystalline polypropylene (HcPP). It’s stiffer than regular PP.

Polystyrene (PS)

Definition of PS

Polystyrene (PS) is a commodity plastic that comes in two basic types for injection molding:

General purpose polystyrene (GPPS) .

High impact polystyrene (HIPS) .

GPPS is more brittle and has lower dimensional stability than HIPS, which is compounded with butadiene rubber to enhance its material properties. GPPS also has glass-like clarity, while HIPS is opaque. Both types of polystyrene are well suited for injection molding because they have predictable and uniform shrinkage.

Advantages of PS

PS plastics are cheap, light, and don’t get wet or grow germs. They also don’t mind getting zapped with gamma rays, so you can use them to sterilize medical stuff. Injection molded polystyrene also doesn’t mind getting splashed with weak acids or bases.

Disadvantages of PS

Polystyrene is flammable, it can be degraded by UV light, and it can be attacked by hydrocarbon solvents like benzene and kerosene. It is brittle, so GPPS can crack easily. Injection molded polystyrene can be recycled, but it can’t be biodegraded.

Applications of PS

Polystyrene is used in medical, optical, and electrical and electronic applications. HIPS is often used with appliances and equipment because it is stronger. Injection molded GPPS is used in plastic toys, boxes, containers, and pallets.

PS Grades

You can fill polystyrene with glass to make it stronger or mix it with acrylic to make it clearer and more resistant to chemicals and UV light.

Thermoplastic Elastomer (TPE)

TPE Definition

Thermoplastic Elastomer (TPE) or Thermoplastic Rubber (TPR) is a blend of rubber and plastic materials. TPE has the properties and performance of rubber, but processes like plastic.

The elasticity of TPR is part of what makes it attractive to designers and engineers. TPE is also recyclable and can be recycled six times. In addition, other recycled materials can be blended together to produce TPE.

Advantages of TPE

TPEs can be stretched to moderate elongations and, when the stress is removed, they return to nearly their original shape. TPE also has shorter molding cycles, supports overmolding options, and is easier and less expensive to mold than liquid silicone rubber (LSR).

Disadvantages of TPE

TPE is prone to creep under sustained stress, which is when a solid material permanently deforms. It also loses its rubber properties at higher temperatures and is more expensive than other injection molding materials.

TPE Applications

TPEs that are injection molded are used in footwear, medical devices, automotive parts, and pet products. Automotive applications include weather seals and shockproof dust covers. Medical applications include breathing tubes, valves, catheters, and ventilation masks.

Thermoplastic Polyurethane (TPU)

Definition of TPU

Thermoplastic Polyurethane (TPU) is a thermoplastic elastomer (TPE). Like other TPEs, TPU has rubber-like elasticity, but injection molded TPU is harder and can be used as a substitute for hard rubber. TPU is often chosen over TPE because TPU is better suited to extreme temperatures and chemical resistance. On the other hand, TPE is softer and more flexible.

Advantages of TPU

TPU has better corrosion resistance than other TPEs. It is also resistant to abrasion, chemicals, grease, oil, and high temperatures. Injection molded TPU also has good load-bearing capacity and is suitable for environments where the material is exposed to ozone.

Disadvantages of TPU

TPU might be too hard or not flexible enough for some injection molded parts. Thermoplastic polyurethanes also tend to be more expensive and need to be dried before processing. Because some grades have a short shelf life, injection molders may have to throw them away before they can use them.

TPU Applications

TPU is used in footwear, gaskets, casters, and sporting goods. It’s also used for housings or casings for electronic and medical devices. In medical applications, TPU is sometimes used instead of PVC, a plastic that can cause skin irritation.

TPU Grades

There are commercial, medical, and industrial grades of thermoplastic polyurethanes. TPU materials are mainly divided into three categories: polyester, polyether, and polycaprolactone.

Summary

In short, there are different plastic injection molding materials for injection molding, such as acrylic, ABS, nylon, etc. Each material has its own characteristics and applicable scenarios.

Knowing the advantages and disadvantages of each material can help you choose the most suitable material for your design and production, so as to achieve the best performance and cost-effectiveness.

Ztar Mold has first-class injection molding technology. If you have any injection molding project, you can always contact us.