Picking the resin for an electronics enclosure feels like a detail you can defer to the factory. It isn't. The wrong plastic cracks in a winter shipment, deforms next to a voltage regulator, or fails a flammability requirement you didn't know applied. Worse, "ABS" on a quote can mean five different grades with a 3:1 spread in impact resistance. If your drawing just says "plastic, black," you're trusting the factory to optimize for their cost, not your reliability.
Here are the three workhorse materials and where each one actually belongs.
ABS — the default, and why it's the default
ABS is cheap, easy to mold, takes texture and paint well, and has decent impact strength at room temperature. For a consumer gadget that lives indoors, it's usually the right call.
Its limits are real, though:
- Heat: ABS softens around 95-100 °C. Put it next to a hot LDO or a power resistor and it can creep and warp over months.
- Cold impact: below freezing, ABS gets brittle. A product that survives a drop in your office can shatter on a loading dock in Ningbo in January.
- Flammability: standard ABS is HB-rated at best. If you need UL94 V-0, you need a flame-retardant grade, which changes the price and sometimes the color options.
PC and PC/ABS blends — when ABS isn't enough
Polycarbonate (PC) is far tougher and handles heat to roughly 130-140 °C. It's the go-to for anything that takes mechanical abuse or sits near heat. The downside is cost (often 30-50% more than ABS), harder molding, and it scratches more easily.
In practice, the sweet spot for most industrial and outdoor electronics is a PC/ABS blend. You get most of PC's impact and heat performance with ABS's moldability and lower cost. Many laptop chassis and instrument housings are PC/ABS for exactly this reason.
Glass-filled nylon (PA) — for structural parts
When a part is structural — a bracket, a gear, a mounting frame that carries load — unfilled plastics flex too much. Glass-filled nylon (PA6-GF30, PA66-GF30, the "30" meaning 30% glass fiber) gets you stiffness and creep resistance close to die-cast aluminum at a fraction of the weight.
The trade-offs: glass fiber is abrasive (it wears molds faster, so tooling costs more), surface finish is rougher, and nylon absorbs moisture, which shifts dimensions. Don't reach for it on a cosmetic outer shell; reach for it where stiffness under load matters.
The flammability rating buyers forget
UL94 is the rating that quietly fails projects at certification. The common grades:
- HB — slow horizontal burn, the bare minimum.
- V-2 / V-1 / V-0 — vertical burn tests, V-0 being the strictest (self-extinguishes in ≤10 seconds, no flaming drips).
Anything mains-powered, or any enclosure containing a power supply, very often needs V-0 to pass safety certification. Flame-retardant grades cost more and can limit color, so this has to be decided before tooling — not discovered during testing.
How to actually spec it on the drawing
Don't write "ABS." Write the full callout so the factory can't substitute a cheaper grade:
-
Material + grade, e.g.
PC/ABS, Bayblend T65 or equivalentorPA66-GF30. -
UL94 rating + thickness, e.g.
UL94 V-0 @ 1.5 mm(the rating is thickness-dependent — V-0 at 3 mm may be only V-2 at 1.0 mm). - Color and finish, with a Pantone or grain reference.
- A "no substitution without written approval" note. This one line stops the most common cost-down failure.
A concrete example: a client shipping an outdoor sensor specified only "black plastic enclosure." The factory used standard ABS. Units in a cold-climate distributor's warehouse cracked at the screw bosses during winter handling — about 6% of one batch. Switching to a PC/ABS V-0 grade and adding the rating to the drawing added roughly $0.40 per unit and ended the cracking.
This is the kind of detail that's hard to catch from a quote alone. If you don't have an engineer reading the spec on the factory floor, an engineering-led agent like China Sourcing Agents will check the actual resin grade against your drawing during the factory audit — because "equivalent material" on a Chinese quote is where margins quietly get rebuilt at your expense.
Spec the resin, spec the UL94 rating, and forbid silent substitution. Three lines on a drawing prevent the failures that show up six months and one cold winter later.
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