Rheological Study on Cold and Warm Processings of Polycarbonate

Abstract

The retentivity of shape in uniaxial compression of polycarbonate resin when processing in the cold and warm processing temperature range was investigated experimentally. Iupilon, a polycarbonate resin manufactured by the solvent process, was used as the sample. Strain recovery of test specimens, which were processed by compression at various temperatures, was measured after free annealing by raising the temperature gradually to a temperature higher than the processing temperature. Polycarbonate has superior processability in the vicinity of room temperature and has good strain-freezing properties at temperatures below the glass transition temperature; however, strain is recovered completely at temperatures above the glass transition point. A new Erichsen testing apparatus was developed for measuring the temperature dependence of processability of sheet in the cold and warm temperature range. A punch is pushed into the sheet whose temperature has been made uniform in a constant temperature apparatus at a fixed stroke speed; the Erichsen depth at fracture at the various temperatures is measured. Results indicated that processability of polycarbonate sheet (thickness, 1 mm) improves gradually with temperature rise as high as the glass transition point. Experiments on strain recovery of an Erichsen test specimen were carried out in the same manner as in the case of uniaxial compression. The results for combined stresses, such as in Erichsen bulging, were similar to those of uniaxial compression. An attempt is being made to utilize such Erichsen bulging test specimens for environmental stress cracking tests of polycarbonate.