FR ABS FR PC FR PC ABS Flame Retardant Electrical Enclosures Your enclosure needs UL 94 V-0. You spec a flame-retardant grade. Then the real trouble starts.

The part comes out brittle. Surface looks like orange peel. Your cycle time doubled, and you’re scrapping 15% of the first run. I’ve seen this pattern more times than I can count. Here’s the thing: flame-retardant additives change everything about how a material behaves. The base resin you choose determines how well the part survives that transition.

FR additives reduce impact strength by 15-30% across the board. But retention curves are different for every base resin. FR-PC holds 85-90% of its toughness. FR-ABS can lose 30% or more. FR-PC/ABS splits the difference. Price follows the same pattern — PC costs roughly 2x ABS, with PC/ABS in the middle. Your application’s thermal, mechanical, and cost requirements will tell you which one wins.

FR-ABS

Lowest cost. Halogenated FR systems are standard here, and they’re effective — UL 94 V-0 at 1.6 mm with a clean pass. Surface finish is good, which matters for visible enclosures. But there’s a cost beyond the price tag.

Impact drops 30% versus unfilled ABS. That notched Izod of 5-6 ft-lb/in falls to 3-4 ft-lb/in. HDT drops to 85-95°C, so you’re limited to indoor environments with no significant heat load. The process window is narrow — roughly 10°C between adequate fill and material degradation. Run at 200°C and you risk poor flow. Push it to 230°C and you’re knocking on decomposition. Plate-out on the mold is common after 50,000 cycles.

Cost runs $2.50-3.50/kg. If your enclosure lives in a conditioned space and V-0 is the only requirement, this is your cheapest path.

FR-PC

Polycarbonate starts with natural flame resistance — a V-2 rating without any additives. Adding FR pushes it to V-0 at 0.8 mm. That’s half the wall thickness FR-ABS needs. Thinner walls mean less material per part, which can offset the higher per-kg cost.

Mechanical retention is the best of the three. Impact drops only 10-15%, so you’re looking at 12-15 ft-lb/in notched Izod. HDT stays at 125-135°C, making FR-PC the only real option if your enclosure sees heat. The FR package is also more thermally stable — less plate-out, less corrosive gas evolution during processing. CTI hits 200-300 V, which matters for creepage requirements in higher-voltage equipment.

The trade-off is processing. FR-PC needs melt temperatures of 290-320°C. That means a barrel capable of those temps, precise thermal control, and a tool designed for higher shrink. Drying is non-negotiable: 120°C for 4 hours minimum. Skip it and your parts come out with splay and properties that don’t match the datasheet.

Cost is $4.50-6.00/kg. But if you can thin the wall from 1.6 mm to 0.8 mm, the per-part cost might be competitive with FR-ABS.

FR-PC/ABS

This blend exists because neither FR-ABS nor FR-PC is the right answer for most applications. FR-PC/ABS gives you impact retention of 75-80% — better than FR-ABS but short of straight PC. Notched Izod lands around 8-10 ft-lb/in. HDT is 100-115°C, enough for warm indoor environments but not for under-hood duty.

What FR-PC/ABS does best is surface quality. It flows better than FR-PC and gives a glossier, more uniform surface than FR-ABS. For a consumer-facing enclosure where appearance matters, this is often the winner. It processes at 240-270°C, which fits standard molding equipment without needing high-temperature barrels. No special drying beyond what standard PC/ABS requires.

Cost is $3.50-5.00/kg, about 1.4x FR-ABS. For most indoor electrical enclosures — power supplies, control boxes, IT equipment — this is the material I recommend first. It handles the balance better than anything else at this price.

Property Comparison

How to Pick

Choose FR-ABS when cost is the primary driver and the enclosure stays indoors with no significant heat load. Your part needs V-0, but it doesn’t need thin walls, high CTI, or elevated temperature ratings. Surface finish is acceptable. The narrow process window is manageable with a stable production setup and tight temperature control.

Choose FR-PC when you need V-0 at the thinnest possible wall, or when the operating environment exceeds 100°C. If you’re designing a compact enclosure with dense electronics, the 0.8 mm V-0 rating lets you save space and material. FR-PC is also the pick for high-CTI requirements — 300 V puts it ahead of the other two.

Choose FR-PC/ABS for the best all-around balance. It processes well, looks good, holds reasonable mechanical properties, and costs less than PC. For the majority of electrical enclosure applications — wall-mount boxes, power supplies, IT equipment, control panels — this is where I start the conversation.

I’ve tested all three at various wall thicknesses and heat exposures. The patterns hold consistent. FR-ABS works when you need to hit a price point. FR-PC works when the environment demands it. FR-PC/ABS works when you need a material that doesn’t force you to compromise on everything else.

Not sure which one fits your enclosure requirements? Talk to our engineering team about your operating conditions, wall thickness targets, and volume.