复合拉伸力场挤出HDPE片材的力学性能

Mechanical properties of HDPE sheet extruded at compound tensile force field

利用收敛-发散口模挤出制备了高密度聚乙烯(HDPE)片材,研究了挤出温度对片材力学性能的影响。结果表明:在复合拉伸力场作用下,熔态挤出(140℃)片材的纵、横向屈服拉伸强度分别为28.3,27.0 MPa,固态挤出(112℃)片材的纵、横向屈服拉伸强度分别为181.4,51.3 MPa,纵、横向屈服拉伸强度分别增加了540%和90%。与固态挤出相比,熔态挤出片材纵、横向断裂伸长率分别增加了760%和124%。扫描电子显微镜显示,熔态挤出HDPE片材由球晶结构构成;固态挤出片材由大量垂直于挤出方向规整排列的片晶组成,并有少量的串晶生成,片晶厚度增加,这种结构有利于改善制品的双向力学性能。

The authors prepared self-reilfforced high density polyethylene （HDPE） sheet by means of the convergence-divergence die and studied the effect of extrusion temperature on mechanical properties of the extrudate. The results show that under the action of the compound tensile force field, the tensile yield strength in longitudinal and transverse direction of the sheet prepared in melt state extrusion at 140 ℃ is 28.3 MPa and 27.0 MPa, respectively; the corresponding values of the sheet prepared in solid state extrusion （SSE） at 112 ℃ is 181.4 MPa and 51.3 MPa respectively, increasing by 540% and 90%, respectively. The elongation at break in longitudinal and transverse direction of the MSE sheet rises by 760% and 124%, respectively, compared with the SSE sheet. The observations by scanning electron microscope （SEM） reveal that spherulite structure predominates in the MSE HDPE sheets while the thicken lamellas, which are arranged regularly and vertical to the extrusion direction, comprises the SSE sheet, besides the shish-kebab crystalline structure existed in small quantity. The structure featuring lamellar crystal is beneficial to improving the longitudinal and transverse mechanical properties of the HDPE articles.