A composition including a particulate solid, a plastic material and a polymer, wherein the polymer is a polyamide with fatty terminal end groups; wherein the polyamide is a condensation reaction product of a diamine and a diacid; wherein the polymer has from 5 to 13 monomer units; wherein the diamine is a saturated C2-C12, linear, branched, or cyclic diamine; wherein the amine groups of the diamine are primary or secondary; wherein the diacid is a saturated C20-C50 branched carboxylic diacid; and wherein each of the fatty terminal end groups are independently a C6-C36 linear or branched carbon chain which is attached to the polyamide via an amide or an imide bond.