超高分子量聚乙烯冻胶纤维拉伸流变性能的研究

A STUDY OF ELONGATIONAL RHEOLOGICAL BEHAVIOUR OF UHMW-PE GEL FIBER

本文通过恒速拉伸测力仪探讨了超高分子量聚乙烯冻胶纤维的拉伸流变性质,发现它的表观拉伸粘度η_(?)与拉伸形变速率ε之间的关系曲线因温度和拉伸倍数λ的不同可分为三种类型。三种曲线均在ε=0.005s^(-1)左右发生了重大转折,说明ε=0.005s^(-1)处是聚乙烯冻胶纤维在拉伸时,大分子链缠结与解缠这对矛盾的关节点。不仅η_(?)与ε的关系曲线在此处发生重大转折,而且拉伸应力σ_(?)与ε的关系曲线也在此处出现极大值。实验还发现温度对η_(?)的影响可分为二个区。在低温区,拉伸粘流活化能E_(aⅡ)=20～50kJ/mol,对应于纤维内自由体积的收缩和无定形区的变形;在高温区,拉伸粘流活化能E_(aⅠ)=150～330kJ/mol,对应于大分子链的滑移和伸直链结晶的发展,E_(aⅠ)随拉伸倍数的上升而下降。二个温度区之间的转变温度T_D=117～123℃,它受ε和λ的影响而略有变化。λ较大时,T_D较小;ε较大时,T_D就偏向上限。

The elongational rheological behaviour of UHMWPE fibers was investigated by a dynamometer. Three stages of the change of “apparent” elongational viscosity η_e vs. deformation rate for several drawing ratios and drawing temperatures were revealed in which η_e increased,maintained constant and decreased respectively with ε. The deformation rate of ε about 0.005s^(-1) implies a transformation of the elongational rheological behaviour of fibers where the highest draw ratio of the fibers is obtained. The activation energy for viscous flow below 120℃ in the range of 20-50 kJ/tool,indicates that hot-drawing in this region proceeds by a sliding motion of microfibril units, the activation energy above 120℃ in the range of 150-330 kJ/tool,indicates that hot-drawing in this region proceeds by a slipping of chains and development of extended chains. The results suggest that the drawing process can be divided into two stages. The first stage with a temperature of～110℃ and the second stage with a temperature of～130℃.