Preparation of Calcium Sulfate Hemihydrate and Application in Polypropylene Composites

The calcium sulfate hemihydrate (HH) whiskers were prepared by using phosphogypsum (PG) as raw materials in autoclave-free hydrothermal system. The influences of glycerol content, reaction temperature, and ratio of solid/solution on whiskers growth were detected. The whiskers with smooth surface and high aspect ratio were obtained with 1: 9 ratio of solid/solution in a 50 vol% glycerol solution at 105 degrees C. The influence of whiskers surface treatment on composites (polypropylene (PP) matrix) mechanical properties were detected by using surface modification reagent (stearic acid (SA) and silane coupling agent (SCA), respectively). The influence of whiskers addition content on composites properties also explored. The high tensile strength of composites (37.6 MPa) was obtained with a 10 wt% whiskers addition content, which the whiskers were treated by using SCA.