Flame Retardant Plastics

A rating belongs to a grade, not to a polymer

Base resins are not flame retardant; specific compounds from specific makers are. "FR ABS" is not something you can buy against — you buy a certificate naming your grade, wall and colour.

The card is filed per grade

Two compounds sharing a base polymer can carry different ratings, and the unfilled version carries none. Ask for the card with compound and maker printed on it.

Your thinnest wall decides

Burning behaviour changes with section, and thin walls are the hard case. Specify the rating at your thinnest wall.

Colour is inside the listing

Pigments and carriers dilute the package, and not every colourant is listed. Confirm yours is.

Three test regimes buyers confuse

Each answers a different question, and passing one says nothing about the others. Pick the one your market or customer specification cites before asking for a quote.

Halogenated against halogen-free

Different mechanisms

Halogen systems act in the gas phase; many halogen-free systems act in the condensed phase. The gap shows up in loading, and so in mechanics.

Not automatically safer

It is a different trade, not an upgrade: often higher loading, density and cost, with a larger impact penalty. Pay it where smoke toxicity or a ban requires it.

Declare limits, not labels

"Halogen-free" without numbers cannot be enforced. Ask for bromine, chlorine and total halogen limits, plus the standard used.

What the package costs elsewhere

Mechanicals move first

Impact and elongation go first, weld-line strength with them. Ask for notched impact at your wall thickness.

The window narrows

Some packages need lower melt temperatures and short residence; others plate out onto the tool. Ask what the compound tolerates.

Steel and screws

Certain systems corrode steel under heat. Ask which screw, barrel and cavity steel the moulder runs.

Density, regrind, cost

Filler-bearing systems weigh more per litre, so a kilogram buys fewer parts. Ask how density moves piece cost and what regrind will be certified.

Specifying so the certificate matches

• Compound and maker printed on the listing.
• Rating at your thinnest wall, in your colour.
• The regime your market cites: UL94, glow wire or fire class.
• Halogen limits with the measuring standard.
• Impact and flow at your wall, not a test bar.
• Regrind percentage the supplier will certify.

Frequently Asked Questions

Is V-0 always the safe choice?

Only where a rating is required; elsewhere it wastes money and toughness. The rating definitions are set out in our UL94 flame rating guide.

Can I reuse a card issued for another colour?

Only if that colour is named in the listing. Otherwise ask for a letter covering the colour you will run.

Does the EU require halogen-free?

Not as a blanket rule. Ask which rule applies to your market and get the limits in writing. See RoHS and REACH for modified compounds.

Why did impact fall after the switch?

Packages cost impact first. Ask for notched impact at your wall, and redesign ribs before over-specifying the rating.

Which polymer should carry the package?

Choose the base polymer on service conditions, then the package. Start with the engineering plastics routing.

Related Reading

• UL94 Flame Rating Guide: What V-0, V-1, V-2 and HB Mean for Buyers
• Flame Retardant Plastic Grades: Choosing FR PP, ABS, PC and PA by Application
• RoHS and REACH Compliance for Modified PPS: EU Buyer Requirements
• Masterbatch Selection Guide: Carrier Systems, Base Materials and Compliance

Writing an FR specification? Send the rating, thinnest wall, colour and end market to the plastic materials desk. Compare base polymers on PC and PA66, review modified compounds, check the example FR PP compound, and raise melt range and steel questions with custom molding services.