Particle attrition in the rotary valve of a pneumatic conveying system was studied. The relationship between physical properties of polymer granules and attrition behaviour was compared between intact (fresh/unused) and attrited particles. It was observed that attrited particles become more breakable and have lower flowability. Experiments were conducted in a rotary valve and pneumatic conveying system separately; attrition in each case could be described by the Gwyn function. The influence of particle attrition on electrostatic characteristics was examined. Charge density of attrited particles was higher than that of intact ones, but induced current showed a reverse trend.