Interaction of process variables with the fracture behavior of amorphous polystyrene during attrition

Abstract

AbstractThis study investigates the fracture of oriented general‐purpose polystyrene. Specimen microstructure was controlled using an extrusion‐sheeting technique where draw ratio, polymer melt temperature, cooling roll temperature, and nip roll pressure changed according to a designed experiment. Sharp‐notched tension results display a 4X difference in longitudinal vs. transverse specimen values. Shrinkage measurements show contraction in the machine direction amplifies with increasing draw ratio. Craze formation is visible only in those specimens tested in the longitudinal direction. Fracture mechanisms have strong orientation dependence and the extrusion‐sheeting process produces an ideal system to study the effect on attrition. Comminution studies illustrate draw ratio has an effect on the final median particle size and width distribution of the powder. Increasing the draw ratio reduces the volume median particle size and minimizes the formation of fine particles. A monotonic fracture mechanism was initially considered but rejected in favor of a low cycle fatigue model based on estimates of fracture strength.