In order to investigate the heat-degradation of AS resin upon heat-process cycling, several kinds of heat-treated AS samples were prepared by using a hot-pressing or a single-screw extruder, and then, their chemical and/or physical properties were examined. From the results of FT-IR spectrum, it was found that the absorption of C = O group were measured and its intensity increased with heat-process cycles. Such an absorption peak, however, cannot be observed on the samples treated in N2. The molecular weight of the samples decreased with annealing time, and their decline ratios were increased by rising the heat-process temperature. At the same temperature, the molecular weight decline ratios depended only on the heat-process cycle numbers, and not change in spite of the screw speed of the extruder. In N2 atmosphere, however, the molecular weight decline ratios were suppressed about 50% to be compared with that in the air. Although Young’s modulus (E) obtained by stress-strain curves for the heat-process cycled AS samples with their molecular weight (Mw) more than 10,000 were almost the same, the values of E for the heat-recycled AS samples with Mw less than 10,000 decreased with its molecular weight.
