Degradation of ABS during repeated processing and accelerated ageing

An ABS-material has been subjected to a series of six combined cycles of extrusion and ageing in air at an elevated temperature. Each cycle consisted of conventional extrusion processing followed by ageing in air at 90 degreesC for 72 h. Large changes in the tensile and flow properties were observed. From the second to the sixth cycle, the elongation at break decreased markedly due to the ageing and increased as a result of the extrusion step. Further analysis showed that the large reductions in elongation at break could be. attributed to physical ageing of the SAN-phase and to thermo-oxidative ageing of the polybutadiene phase, as shown by further tensile measurements and infrared spectroscopy. SEM-measurements indicated no significant changes in the size and shape of the polybutadiene particles. No significant changes in the molar mass of the SAN-phase were observed. (C) 2003 Elsevier Science Ltd. All rights reserved.