Processed Low NOx Fly Ash as a Filler in Plastics

Fly ash generated from low NOx burners at American Electric Power's Glen Lyn facility was beneficiated to remove residual carbon, magnetic particles, and cenospheres. The clean fly ash had a mean particle size of about 30 microns, which is coarser than typical commercial fillers used in plastics. To obtain a finer sized fly ash, air classification was used to separate the clean fly ash into its coarse and fine fractions. The resulting fine fraction had a mean particle size of 4.13 microns and accounted for 16.7 wt% of the total clean ash. The brightness of the clean ash was also less than that of typical commercial fillers and efforts to improve the brightness proved unsuccessful. The resulting fine ash was then coated with a silane coupling agent and then added to polypropylene, low density polyethylene, and high density polyethylene at various levels. These mixtures were in turn used to make tensile test specimens by injection molding. For comparison, a commercial CaCO3 filler was also tested under the same conditions. The mechanical properties of these specimens were determined and the results show that the polymers containing fly ash as a filler have equivalent properties to those same polymers when commercial fillers are used in most cases.