The stess yielding mechanism of aged atactic polystyrene(α-PS) was studied by use of mechanical tension, differential scanning calorimetry(DSC) and solvent-swelling. The viewpoint of cohensional entaglement(CE) was empolyed to interpret the experimental results, which indicated that the stress yielding of aged α-PS was the destruction of the CE formed during aging. CE was a kind of ordered structure, which was formed by local parallel alignment of several segments of several nearest neighboring chains. Its interaction energy was so low that heating beyond the Tg region, mechanical drawing over the yield point and solvent swelling all could destroy it completely.%利用机械拉伸、示差扫描量热(DSC)以及溶剂溶胀等方法研究了物理老化后的无规聚苯乙烯(α-PS)的应力屈服行为, 并从凝聚缠结的观点对实验结果进行了解释. 实验结果表明, 经物理老化后的α-PS在拉伸过程中出现应力屈服峰实质上是逐步打开凝聚缠结的过程. 凝聚缠结是聚合物非晶相在物理老化过程中相邻的两三条链的局部链段由于范德华吸引力的作用形成的一种有序结构, 其作用能很弱, 升温至Tg附近, 机械拉伸至屈服点以及溶胀剂都可将其完全破坏.
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