When choosing to use injection moulding to create components, you could find yourself with a difficult decision. Different plastic resins each possess different qualities, so you when choosing a plastic for custom moulding, you’ll need to think carefully about the role of the parts you are looking to mould and what qualities you need for them to be successful.

If you’re new to custom injection moulding, you can read more about what custom moulding is and when to use it in last month’s blog ‘What is custom moulding’. However, if you already know what you’re looking for and are trying to work out what plastic resin is best to use, then read on. Here, we’ll look at the main types of plastic resins available for injection moulding, their uses and even their key qualities.

Top custom moulding plastic resins

Acrylic (PMMA)

Acrylic is transparent and, as such, is often used as an alternative to glass. Its exceptional optical clarity enables light to pass through relatively unimpeded. Weatherproof and resistant to the effects of UV, Acrylic is a more common term used for Polymethyl methacrylate.

Key properties of PMMA:

• Thermoplastic
• Lightweight
• Shatter-resistant

Uses OF PMMA:

There are three grades of acrylic commonly in use:

• General purpose acrylic – used in commodity products
• Sign-grade acrylic – stronger and with good light transmission, it’s perfect for external signage.
• Marine grade acrylic – resists constant exposure to water so is used in windshields and windows in boats.

Acrylonitrile butadiene styrene (ABS)

Acrylonitrile butadiene styrene is an easy-to-mould plastic thanks to its low melting point. Its opacity means it works well with a variety of different colours, textures and surface finishes and the butadiene content within Acrylonitrile butadiene styrene makes it exceptionally tough.

Key properties of ABS:

• Strong
• Impact resistant
• Resistant to UV, weather and water
• Smokes burned
• Poor resistance to friction.

Uses of ABS:

• Keyboard keys
• Plug socket surrounds
• Sports equipment and
• Protective headgear

Nylon (Polyamide, PA)

Nylon lends itself to a multitude of uses as it’s both tough and heat resistant with fatigue resistance and even noise-damping properties. Flame-retardant versions are available too. Nylon can degrade in sunlight, but even this can be lessened with the use of a UV stabilizer, making it suitable for outdoor use too. It can also be strengthened with glass fibres.

Nylon comes in 4 grades:

Nylon 11 – this has a greater resistance to dimensional changes and is often used for outdoor applications

Nylon 12 – this has the lowest melting point of all nylon grades and resists water absorption

Nylon 46 – has the highest operating temperature

Nylon 66 – has a high melting point and resists acids used in chemical processing.

Key properties of PA:

• Tough
• Heat resistant
• Prone to shrinkage (which can lead to inadequate mould filling)
• Degrades in sunlight

Uses of PA:

• Casings and snap-fit closures
• Threaded inserts
• Kinetic parts

Polycarbonate (PC)

Polycarbonate is a strong, lightweight and transparent injection moulding material with good light transmission. Polycarbonate maintains its colour and strength when pigmented. It’s stronger than glass but can be prone to scratching.

Properties of PC:

• Maintains physical properties over a wider temperature range
• Requires high processing temperatures which makes it costly to mould
• Allows precise dimensional control for tighter tolerances.

Uses of PC:

• Machine guards
• Windows
• Diffusers and light pipes for LEDs.

Polyoxymethylene (POM)

Also known as Acetal, Polyoxymethylene (POM) is known for its rigidity, low friction and dimensional stability which make it perfect for precision parts.

Properties of POM:

• High rate of thermal expansion
• Re-enforceable with fibreglass or minerals for improved strength
• Low UV tolerance limiting opportunity for outdoor applications.

Uses of POM:

• Bearings
• Gears
• Conveyer belts
• Knives and firearms components
• Glasses frames and lock systems

As you’ve already seen, there are a wide number of resins we can use for custom moulding, so our team here at BPF Online can help you find the right plastics for your project.

In our next blog, we will look at the other 5 resins most regularly used in injection moulding but, In the meantime, if you have any questions about our injection moulding services, you can contact us through the chat on our website.