Key takeaways
- Five engineering resins, five very different jobs.
- A working reference for procurement teams who don't moonlight as polymer chemists.
Engineering plastics are the resins that earn their keep on the mechanical side of the spec sheet, not the price side. They are slower-growing than the commodity polyolefins, but margins are higher and substitution risk is lower. Here is a working reference covering the five families that make up the bulk of global trade.
Three monomers, each contributing one property: acrylonitrile for chemical and heat resistance, butadiene rubber for impact, styrene for stiffness and gloss. ABS is what gives you the dashboard panel, the appliance housing, the LEGO brick. It paints, plates, and welds easily.
Buyer notes: ABS is graded by Vicat softening point and notched Izod. "Plating-grade" ABS is a higher-rubber variant. "Heat-resistant" ABS substitutes some styrene with α-methylstyrene to push the Vicat upward.
PC is glass-clear, dimensionally stable, and almost unbreakable. Its weakness is solvent and surface scratch resistance. Polycarbonate dominates safety eyewear, headlight lenses, electronic device housings, and the rigid layer of medical packaging. PC/ABS blends are the standard automotive interior trim.
Buyer notes: PC is graded by MFI and molecular weight. Optical-grade PC is held to tighter yellowness-index limits than mechanical-grade.
Polyamide trades primarily as PA6 and PA66. Both are tough, abrasion-resistant, and absorb water (which is both a feature and a problem). They are the default for under-bonnet automotive parts, gears, fasteners, and textile fibres.
Buyer notes: PA is almost always sold glass-filled for engineering use — typically 30% glass fibre by weight. The glass content is the most important number on the spec. PA6 vs PA66 differs in melt point (~220 °C vs ~265 °C) and water absorption — PA66 is more dimensionally stable in humid air.
POM is the highest-stiffness, lowest-friction commodity engineering polymer. It is what you specify for precision gears, snap fits that have to last a million cycles, and small mechanical parts that have to slide against metal without lubrication. It exists in two flavours, homopolymer and copolymer — the copolymer is more chemically stable, the homopolymer slightly stiffer.
PBT is a polyester that crystallises faster than its cousin PET. That fast crystallisation makes it the default for automotive electrical parts — connectors, ignition components, sensor housings — where dimensional precision out of the mould is non-negotiable. Glass-filled PBT is one of the most frequently traded engineering grades.
Engineering-plastic markets are concentrated in the hands of a few global producers. Substitution between equivalent grades is genuinely possible — a Korean PA66 30% glass and a German PA66 30% glass should run on the same line — but the producer-to-producer additive packages differ enough that requalification is rarely free. That is why buyers tend to stay with one origin until pricing forces a re-test.