Engineering plastic

Engineering plastics are a group of plastic materials that exhibit superior mechanical and thermal properties in a wide range of conditions over and above more commonly used commodity plastics. The term usually refers to thermoplastic materials rather than thermosetting ones. Engineering plastics are used for parts rather than containers and packaging.

Examples of engineering plastics include:

• Acrylonitrile butadiene styrene (ABS)
• Polycarbonates (PC)
• Polyamides (PA)
• Polybutylene terephthalate (PBT)
• Polyethylene terephthalate (PET)
• Polyphenylene oxide (PPO)
• Polysulphone (PSU)
• Polyetherketone (PEK)
• Polyetheretherketone (PEEK)
• Polyimides
• Polyphenylene sulfide (PPS)

Commodity plastics

The more commonly used thermoplastic materials are known as commodity plastics as they are traded and used in great quantities. Examples are polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP) and polyethylene (PE).

Typical applications for commodity plastics are high production volume products such as ‘polythene’ bags (made from polyethylene), vacuum-formed food packaging (low density polyethylene), disposable drinking cups (high-impact polystyrene) and window frames/wire insulation (PVC).

Engineering plastics

Engineering thermoplastics are sold in much lower quantities and are thus more expensive per unit weight. Despite this, they are widely used in everyday products. For example ABS is used to manufacture car bumpers, dashboard trim and Lego bricks, polycarbonate is used in motorcycle helmets and polyamides (nylons) are used for skis and ski boots.

Typically, an engineering plastic is chosen for its range of enhanced physical properties e.g. polycarbonate is highly impact resistant and polyamides are highly resistant to abrasion. In these types of applications, designers are looking for plastics that can replace traditional engineering materials such as wood or metal. The advantage gained is the inherent ‘formability’ (ease of manufacture) of plastics as opposed to metal-working or fabrication.

Other properties exhibited by various grades of engineering plastics include high heat resistance, mechanical strength, rigidity, chemical stability and flame retardency.