1. After die filling, the upper punch is lowered into the die and the powder is uniaxially compressed to a porosity of between 5 and 20%.

2. Applying a sliding contact technique the linear isotherm compressibility of uniaxially stretched polycarbonate (PC), Polyvinylchloride (PVC), polymethylmethacrylate (PMMA) and polystyrene (PST) was determined at 22 ‡C in the pressure range from 1 to 3000 kp/cm2.