Thermoplastics
Materials in this group of polymeric materials are made up of long chain molecules that are connected by intermolecular forces, as opposed to thermosetting polymers which undergo a chemical change, forming rigid cross links between the molecules. When heat is applied to a thermoplastic material, the forces holding these molecules together are weakened allowing the material to melt and solidify repeatedly. These properties make thermoplastics particularly appropriate for conventional plastic injection moulding machines where the material is heated until molten and then injected at high pressures into a steel or aluminium mould.
The thermoplastics family can be categorised into two main groups, commodity polymers and engineering polymers, depending on the properties of the particular material.
Commodity Polymers
Generally low-cost materials, commodity polymers are suitable for use in applications where the mechanical properties of the material are not critical to performance, although materials in this group will still have specific desirable properties which they are selected for. Plastics that fall under this classification are widely used in mass-produced items and products of a single-use nature such as drinks bottles or films for packaging. However, these materials are not merely limited to disposable products and can be found in products from water pipes to children’s toys.
Examples and their relevant applications include:
Acrylonitrile Butadiene Styrene (ABS) – children’s toys, casings for electronic products.
Ethylene-vinyl Acetate (EVA) – flip-flop soles, swimming buoyancy aids.
High Density Polyethylene (HDPE) – water pipes, bottle tops, fuel tanks.
Low Density Polyethylene (LDPE) – packaging foam, resealable bags.
Polyethylene (PE) – Plastic bags and packaging film.
Polymethyl Methacrylate (PMMA) – Lenses, skylights, outdoor signs.
Polypropylene (PP) – chairs, luggage, sterile bottles
Polystyrene (PS) – yogurt pots, CD cases, expanded foam packaging.
Engineering Polymers
Materials with mechanical properties suited to particularly challenging applications and environments will fall under engineering polymers. Suitable for low-medium volume manufacture, engineering plastics are not produced in the same high volumes of raw material as commodity plastics but are still very widely used. This broad implementation is due to specific properties such as chemical stability, mechanical strength, heat resistance and self-lubrication which have allowed this group of materials to in some circumstances replace conventional engineering materials such as wood and metal. Engineering polymers are often combined with glass fibres or other materials to enhance their useful properties further. Such levels of performance do however come at a cost and engineering polymers are usually significantly more expensive than commodity polymers.
Examples and their relevant applications include:
Polyamide (PA / Nylon) – carpets, clothing, bearings, gears, bushings.
Polybutylene Terephthalate (PBT) – fibres in swimwear, computer keys, electrical wire connections.
Polycarbonate (PC) – safety helmets and eyewear, mobile phone casings, CDs and DVDs.
Polyether Ether Ketone (PEEK) – parts for pistons and pumps, medical implants.
Polyethylene Terephthalate (PET) – Soft drinks bottles and containers, synthetic fibres.
Polyoxymethylene (POM / Acetal) – springs, gears, hinges, cigarette lighters.
Polytetrafluoroethylene (PTFE / Teflon) – slide plates, clothing irons, non-stick cookware.
In conclusion, understanding the distinctions between commodity and engineering thermoplastics is crucial for selecting the right material for your application. Commodity polymers, with their cost-effectiveness and suitability for high-volume, non-critical applications, offer a broad range of uses from packaging to consumer goods. On the other hand, engineering polymers, known for their superior mechanical properties and suitability for demanding environments, are indispensable in applications requiring high performance, such as in automotive and medical industries. The versatility and adaptability of thermoplastics make them invaluable in modern manufacturing, enabling the production of diverse and innovative products.
If you're considering plastic injection moulding for your components and need expert guidance on choosing the right thermoplastic material, schedule a free consultation with us today. Our team is ready to assist you in optimising your designs and ensuring high-quality production. Let's collaborate to bring your ideas to life with the perfect thermoplastic solutions.
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