ABS, polycarbonate and PC/ABS are the workhorses of housings and enclosures. How they really differ in impact, heat, chemical resistance, cost and processing, and the failure modes that decide which one to specify.
A handheld device housing passed every drop test in the lab. Six months after launch, the warranty returns started: cracked housings, always near the screw bosses, almost all from hospitals. The housing was polycarbonate, chosen for its excellent impact strength. Nobody had asked what the product would be cleaned with. Daily wiping with alcohol-based disinfectants was attacking moulded-in stress around the bosses, causing environmental stress cracking. A PC/ABS blend, better boss design and a stress-relieving process change solved it. The material choice was never really about impact strength.
ABS, PC and PC/ABS are the default choices for housings, enclosures and covers. Each has strengths, weaknesses and failure modes that matter far more than the headline datasheet values.
ABS: the economical all-rounder
Acrylonitrile butadiene styrene is easy to mould, has good surface finish and dimensional stability, takes paint, plating and texture well, and costs less than PC.
Watch out for:
- Moderate impact strength, especially at low temperatures.
- A heat deflection temperature typically around 85–100°C, depending on grade.
- Poor UV resistance unless stabilised or painted. Unprotected ABS yellows and embrittles outdoors.
- Limited resistance to some solvents.
Good for: consumer electronics housings, appliance parts, automotive interior trims and products where cost and appearance matter most.
Polycarbonate: tough and heat resistant
PC has outstanding impact strength, high heat resistance with a heat deflection temperature around 130–140°C, good dimensional stability and is available in transparent grades.
Watch out for:
- Notch sensitivity. PC is tough until a sharp corner, scratch or notch concentrates stress, then it can crack. Generous radii are essential.
- Chemical and environmental stress cracking from many solvents, oils, cleaning agents and some plasticised materials, especially where moulded-in or assembly stress exists.
- Higher processing temperatures, drying requirements and higher melt viscosity, which makes thin, long flows harder.
- Higher material cost.
Good for: safety-critical housings, lenses and light covers, electrical components and products that see heat or heavy impact.
PC/ABS: the balanced blend
Blending PC and ABS combines much of PC's toughness and heat resistance with ABS's easier processing and lower cost. Impact strength, especially at low temperature, is usually better than ABS, and processing is easier than PC.
Watch out for:
- Properties vary widely between grades and blend ratios. Compare specific grades, not generic families.
- Chemical resistance is better than PC in many cases but is still not universal. Test with the real chemicals.
- Heat resistance sits between ABS and PC.
Good for: laptop and device housings, automotive interior and electrical enclosures, and medical device housings where toughness, processing and appearance all matter.
Questions that decide the choice
- What temperatures will the part see in use, in transport and in a hot car?
- What chemicals will it contact: cleaners, disinfectants, oils, sunscreens, adhesives?
- What impact and drop requirements apply, including at low temperature?
- Is it outdoors, or under strong light?
- What finish is required: high gloss, texture, paint, plating?
- What flammability rating is needed, such as UL94 V-0, and at what thickness?
- What is the cost target?
Design matters as much as material
Material and design work together. Sharp internal corners, thick bosses and over-tightened screws create the stress that turns a good material into a cracked part. Design with generous radii, the uniform walls we keep returning to, and boss geometry that limits hoop stress. Then test the real part with the real chemicals, at the real temperatures, before release.
