Fly ash (FA) is a fine powder collected as residue in the exhaust gases from combustion chambers of pulverized coal fired boilers at thermal power plant stations. It is usually solid, irregularly spherical in shape; at times, it is a cenosphere with a hollow spherical shape. The size, chemical composition and the colour of fly ash vary depending on the coal type used in coal power stations.

Generally, fly ash particles are light to dark-grey in colour with sizes range up to several hundred microns. Fly ash normally consists of predominantly aluminium silicates with a range of other metal oxide being present. It has been used in several areas, such as cement and concrete applications, bricks, highway pavement, road bases, and backfills. In most countries, fly ash is usually under-utilized.

In this study, as received fly ash from Cement Australia owned coal-power furnaces and subsequently modified into near whitened fly ash (with 96 % whiteness of calcium carbonate) – a UNSW developed technology - were utilized as reinforcement in virgin white polymer polyethylene, using up to 50 weight wt. % of fly ash.

Results indicate that near whitened fly ash produces filled polypropylene composites visibly almost as white as the neat PP polymer. Also, tensile modulus and notched Charpy impact properties of the fly ash filled composites are substantially enhanced by the fly ash addition.

Scanning electron microscopy of notched impact fracture surfaces show smaller size fly ash particles are embedded in the interlamellar textural matrix of the polymer, thereby absorbing / transferring significant mechanical energy under impact.