Ash and filler content of a granule: effect on price, strength and production

Two polypropylene or polyethylene granules are offered at different prices per kilogram, and the cheaper one is tempting. But in filled compounds the price per kilogram is only part of the cost. The number to ask for next to it is the ash percentage: how much of the material is actually filler, not polymer.

What does ash percentage mean?

A sample of granule is burnt in a furnace so the polymer burns away, and what remains is weighed; the residue is the mineral part: calcium carbonate, talc, glass fibre and the like. The result is reported as weight percent. On the datasheets of our grades this number appears as “Filler Content” with the ASTM D5630 method.

Why it changes what you pay

• Weight and cost per part: filler raises density, so the same part uses more weight. Compare price per kilogram multiplied by density, not price per kilogram alone.
• Stiffness and brittleness: more filler gives a stiffer, heavier, usually more brittle part.
• Consistency: if the filler level drifts between shipments, so do shrinkage and fit.

How to check it

State the test temperature, because calcium carbonate itself loses mass at high temperatures. Ask for the ash result with its method on the datasheet of your batch, or have the test run on a sample of the shipment. See also batch consistency.

For help, contact the Epic Polymer specialists: +98 919 212 4919 · WhatsApp.