Engineered porous calcium silicate as paper filler: effect of filler morphology on paper properties

Developing engineered filler with special morphology to increase filler content and deliver paper desirable properties has been deserved much concern. In this work, two engineered calcium silicate fillers with different morphology, namely fly ash based calcium silicate (FACS), fibrous calcium silicate (FCS) were adopted to investigate the effect of filler morphology on paper properties, and natural wollastonite was used for comparison. It is found that FACS exhibits a wrinkled, porous surface while FCS reveals spherical agglomerates composed of needle-like particles. Physical tests demonstrated that in comparison with natural wollastonite with discrete shape, the aggregated porous structure of FACS and FCS showed noticeable improvement in bulk and opacity due to their high specific surface area (112 m2/g v.s 29 m2/g). At around 40 % filler content, the bulk of FACS and FCS filled handsheets increased 59.6 % and 43.8 %, respectively. The findings suggested that the engineered porous calcium silicate can be potentially used as paper filler in light weighted paper.