中文摘要：

采用恒速型双毛细管流变仪对比研究3种线型低密度聚乙烯（LLDPE）熔体的高速挤出流变性能。结果表明,3种LLDPE熔体均出现亚稳定光滑挤出（又称第二光滑挤出）现象;亚稳定挤出速率远大于第一稳定挤出区的挤出速率,而挤出压力并未成比例升高。升高温度后发生亚稳定光滑挤出的临界剪切速率增大,稳定挤出的速率范围扩大。亚稳定光滑挤出的发生与熔体在粘-滑畸变区的行为有关,亚稳定光滑挤出物的表观与粘-滑畸变区中滑段挤出物表观相似。在粘-滑畸变区滑段的长度随挤出速率而增大,当滑段长度比例达到100%时,即发生亚稳定光滑挤出。分析认为,在亚稳定光滑挤出区,熔体/管壁界面发生了整体滑动。

英文摘要：

The rheology properties of LLDPE melts at high speed extrusion were studied by double capillary rheometer of constant speed type.It was indicated that,all the three kinds LLDPE melts showed metastable smooth extrusion phenomenon（the second smooth extrusion）;compared with the stable smooth extrusion phenomenon,the extrusion rate of metastable smooth extrusion phenomenon were much higher,but the extrusion pressure did not inrease in proportion.The critical shear rate and the range of extrusion rate for the metastable smooth extrusion phenomenon increased with temperature increasing.The occurrence of metastable smooth extrusion was involved in the stick-slip distortion;the appearance of metastable smooth extrudate was similar to the smooth section of stick-slip distortion.The length of stick-slip distortion＇s smooth section increased with increasing shear rate.When the extrudate appearance was totally smooth,the phenomenon of metastable smooth extrusion began to appear.By analysis,when metastable smooth extrusion happened,global slip occurred at the melt/wall boundary condition.