高密度聚乙烯吹膜挺度与微观结构的关系

Relationship between stiffness and microstructure of high density polyethylene blown films

采用5种国内外高密度聚乙烯(HDPE)树脂在相同的吹膜条件下制备了具有不同挺度的吹膜制品,利用DSC,WAXD,SAXS等方法研究了吹膜试样的微观结构与挺度之间的关系。实验结果表明,树脂的密度或弯曲模量不能完全决定薄膜制品的挺度性能。HDPE吹膜中的大部分晶体排列均沿薄膜纵向方向,少量晶体沿着其他方向无规排列。薄膜的取向度增加,平均杨氏模量越大,挺度越好。薄膜的结晶度越大,平均杨氏模量越大,薄膜的挺度越好。薄膜制品的结晶度和取向度共同决定了制品的挺度性能。

DSC,WAXD and SAXS are used to investigate the relationship between the microstructure and stiffness of the blown film samples of five high-density polyethylene（HDPE） abroad under the same film-blowing condition.The experimental results show that the stiffness of the film products cannot be simply attributed to the density or flexural modulus of HDPE resins.The crystallites in blown films are vertically oriented mainly along the machine direction,while a minority of crystallites are distributed randomly.Moreover,with the orientation degree of the films increased,the average Young modulus and the stiffness increased.Also,with the increase of the crystallinity,the average Young modulus increases and the stiffness of the films becomes better.So the stiffness of the blown film product is determined jointly by its crystallinity and orientation.