Abstract:

Isothermal crystallization behavior of highdensity polyethylene (HDPE) was studied experimentally by using a rotary rheometer with parallel plates fixturesIt was found that the crystallization rate depended on the surface roughness of the fixtures with the same chemical compositionAs the surface roughness increased，the crystallization rate first increased then decreased which meant that there was a range of surface roughness where the crystallization rate could reach a maximum valueSurface roughness effectively enhanced the interfacial area and decreased heat resistance, but possibly trapped air pockets in the valley of the rough surface produced a considerable interfacial heat resistance，both affecting the crystallization rate of HDPEThe isothermal crystallization rate decreased in sequence as the HDPE specimen contacted with aluminum，brass and stainless steel plates whose surface roughness were on the same levelThe sample crystallizes more quickly on the fixtures with higher heat conduction coefficient, thus lowering heat resistance.

Key words: 高密度聚乙烯, 等温结晶, 表面粗糙度, 热阻, 表面能

摘要： 用旋转流变仪研究了高密度聚乙烯的等温结晶行为，发现结晶速率对夹具表面粗糙度存在依赖性，随着表面粗糙度的增加，结晶速率先增加后减小.粗糙度的增加增大了样品与夹具间的接触面积，减小了热阻，同时界面间可能积存的气泡使得界面热阻较大，都影响着结晶速率.对于相同表面粗糙度的铝、黄铜和不锈钢三种材质的夹具，相应的结晶速率排序为：铝最快，黄铜居中，不锈钢最慢.我们研究发现HDPE样品的结晶速率对夹具的表面能不敏感，而夹具的导热系数越大，热阻越小，结晶速率越大.

关键词: 高密度聚乙烯, 等温结晶, 表面粗糙度, 热阻, 表面能