What Plastic is Used in Injection Moulding

Feb 16, 2024

Understanding which thermoplastic is the best option for an injection moulded component can be tricky, with so many options available it can be hard to know where to start. With our specialist knowledge and processing experience we will be talking through just some of the material options available.

It is important to consider a few areas when selecting the type of plastic to be used for your product manufacture, strength, durability, flexibility, and resistance to external environments.

What plastic is used in injection moulding?

High-Density Polyethylene (HDPE)

This plastic is a strong all-rounder, used for a range of applications, from plastic bottles to recycling bins. It’s a low-cost option too, so you get the best of both worlds in terms of strength and affordability.

Low-Density Polyethylene (LDPE)

As you might have guessed, the low-density version of polyethylene is a lot softer and more flexible than its high-density counterpart. It’s usually used to form items such as plastic bags and plastic wraps, with the benefit of being food-grade too, so it’s safe to use in catering and food production.

It’s well worth mentioning that this kind of plastic isn’t used around fire; it can be flammable, and doesn’t resist high temperatures well.

Polycarbonate (PC)

Usually transparent, polycarbonate is super strong, and it is often used in engineering, but can also be found in compact discs, safety helmets and telephone hardware. Due to its durability, it’s often used in defensive applications too, such as riot shields, and even bulletproof glass. It’s largely scratch resistant too!


This may be a polymer associated mainly with fabric, but it can be used in injection moulding too. Car tyres, insulators and fish nets can all contain nylon, such is its versatility. Its longevity and elasticity are its main selling points, though it can melt easily, so it’s best avoided around high temperatures without heat stabilisers.

Polyoxymethylene (POM)

Another tough type of injection moulding plastic is polyoxymethylene, otherwise known as acetal. Acetal is often used in automotive parts - and we certainly want those to last a long time! It can also be found in gears, door handles, zips, seat belts and even insulin pens. Its disadvantages include a vulnerability to UV and poor resistance to acid.

Acrylic Poly (Methyl Methacrylate) (PMMA)

Acrylic is a relatively common term even outside of the world of injection moulding, and is recognisable to most as sheet, light in weight and used predominantly for things like lenses, both in glasses and car lights. It’s weather resistant, high gloss, and durable against abrasion. It’s not famed for its heat resistance though, and it is susceptible to cracking under pressure.

Thermoplastic Polyurethane (TPU)

Thermoplastic polyurethane has a variety of properties to its name, including transparency, elasticity, and resistance to grease, oil, impact and tears. Common applications for thermoplastic polyurethane range from footwear and sports watch straps to mobile phone cases, fire hoses, and even medical equipment. For this level of versatility, you do pay a higher price.

Thermoplastic Rubber (TPR)

Otherwise known as elastomer, thermoplastic rubber is loved for its ability to stretch and return to its original shape. It’s often used in cabling, insulation, and home appliances, but can also be used to make certain automotive parts. For the eco-conscious, thermoplastic rubber is a good option, as it does not contain non-toxic recyclable plastics, but again, this is one of the more expensive thermoplastics.

Polypropylene (PP)

This is a very popular thermoplastic polymer and it’s used all over the food and drink industry in packaging and storage thanks to its excellent moisture resistance, and the way it doesn’t allow chemicals to mix with the contents. It’s important not to leave this polymer in the sun as it can degrade when exposed to UV.

Acrylonitrile Butadiene Styrene (ABS)

We see a high volume of this plastic used in injection moulding, as it is strong and durable whilst also being lightweight. It can withstand a certain amount of heat, too, which makes it a popular choice. It is usually used for applications such as pipes, protective headwear and automotive parts - anything that needs to be rigid, but also light in weight.

Choose Pentagon Plastics for your injection moulding project

It is fair to say that we know our plastics here at Pentagon, and it is our pleasure to advise a range of industries on the best material options for their products. It is essential to strike a balance between affordability and the fit-for-purpose nature of the application, and you can be confident that our 50 years in the business and the specialist support network we have developed puts your project in safe hands.

To find out more about our plastic injection moulding process or for material advice in the design stages contact us today.

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