Almost every moulded enclosure programme eventually chooses between ABS and polycarbonate, and the choice is usually made on a single property when the decision actually involves three. ABS is cheaper, easier to mould and takes colour well; polycarbonate is tougher, clearer and holds heat better. The PC/ABS blend sits between them and wins most housing applications. This guide covers the trade-offs in the order they matter on the line.
Impact: the drop test decides
Polycarbonate is the toughest of the three by a wide margin, and its impact performance holds at low temperature, which ABS does not: an ABS housing dropped in winter conditions fails in a way the same housing passes in summer. Programmes with a defined drop specification, handheld devices, power tools, outdoor enclosures, usually start with polycarbonate or the blend for that reason. Where the housing is protected by the product design, a recessed face or a rubber boot, ABS impact is often adequate and the cost saving is real.
| Property | ABS | PC/ABS blend | Polycarbonate |
|---|---|---|---|
| Impact, notched | Moderate, drops at low temp | Good, holds better cold | Excellent, cold-stable |
| Heat deflection | Around 95 C class | Around 110 C class | Around 125 C class |
| Mouldability | Easy, forgiving | Good, wider window than PC | Demanding, needs dry resin |
| Surface and colour | Excellent, paints and textures well | Good, slight flow lines | Good, stress crazing risk |
| Cost position | Lowest | Middle | Highest of the three |
Heat: the warehouse and the lamp test
Heat deflection is the second screen, and it bites in two places. The first is service temperature: a housing mounted near a motor, a lamp or a power supply sees local temperatures that ABS does not carry, and the part softens, creeps and eventually deforms under load. The second is the glow-wire or ball-pressure tests that electrical enclosures face; polycarbonate and the blend pass where ABS often does not. If the product carries an electrical certification with a thermal requirement, the material choice has already been made.
Surface: what the eye sees
ABS takes texture and colour better than either alternative, and a textured ABS housing hides flow lines, sink and ejector marks that would show on a glossy polycarbonate part. Polycarbonate is prone to stress crazing in contact with certain chemicals and oils, which matters for housings that get cleaned or handled with sunscreen, and the blend reduces but does not eliminate the sensitivity. Cosmetic programmes with a high-gloss requirement usually end up on ABS or the blend with texture, and structural programmes with a drop requirement end up on polycarbonate with a finish that hides the mould marks.
The moulding differences that reach the quote
Polycarbonate is hygroscopic, and moulding it wet produces parts that look fine and fail later, which is why the resin needs drying and the process needs the moisture spec. ABS moulds in a wide, forgiving window and is the easiest of the three to run on a shared tool. The blend sits closer to polycarbonate on drying and closer to ABS on flow, which is why it has become the default for housings that need both. The quote differences follow the drying requirement, the cycle time and the scrap rate, not the resin price alone.
Choosing in practice
The practical sequence is: check the drop requirement first, because it eliminates ABS for unprotected housings; check the thermal and electrical requirements second, because they eliminate ABS for anything near heat; then choose on surface and cost, where ABS wins if it survives the first two screens and the blend wins if it needs a middle position. A housing programme that writes the drop height, the service temperature and the surface class into the RFQ gets comparable quotes from the first round.
Related reading
The materials category lists the housing grades, the PC versus PP chemical resistance guide covers the adjacent choice, and the recovery device housing programme shows a two-shell ABS assembly.
