Fillers

Abstract

Fillers may be broadly defined as solid particulate or fibrous materials, substantially inert chemically, incorporated in plastics compositions (including PVC) to modify the properties or to reduce material cost. Cost reduction is often the primary reason for the use of a filler, and because of this the term is occasionally treated (incorrectly) as if it was synonymous with ‘cheapening extender’. In fact all fillers, when present in the significant quantities in which they are normally used affect in some measure the material and/or processing properties of the plastic: some—which may be termed ‘functional fillers’—are indeed used, often at increased cost, expressly as property modifiers, e.g. glass fibres as reinforcing filler in uPVC compositions, antimony trioxide or alumina trihydrate as flame retardants in pPVC. It may be noted that the functional aspect is emphasised in the standard definitions of a filler (cf. for example, ISO 472–1979; BS 1755: Part 1:1967; ASTM D 883–83).