Improvement of polyolefin film by alternately stacking different kinds of thin, oriented polymers

制备了取向等规丙烯（iPP）和聚乙烯（PE）交替叠层的复合薄膜，但其拉伸模量和强度等物理性能不够高，在实际应用中难以持久。为了提高性能，我们发现有三个主要的障碍需要克服。首先，iPP和PE各自的层越薄越好，在拉伸前单层可能小于0.1 mm。在本研究中，通过交替堆积iPP和PE的所谓“凝胶”，这些聚合物是由溶液结晶而成的。当iPP和PE凝胶交替堆叠时，各自的凝胶表面相当粗糙，很难使各层厚度均匀，特别是当每层都很薄时。必须开发一种使单个层变薄并使其表面平坦的技术。由于iPP和PE可获得高拉伸比的温度不同，因此如何选择合适的温度同时实现高拉伸是一个问题。实验结果表明，在130 C-140 C的温度范围内，两种聚合物均可同时顺利拉伸。选择和控制合适的拉伸温度是第二个需要解决的问题。另一个需要克服的问题是如何绘制出高度堆叠的凝胶膜。这与上述两个问题密切相关。

The composite films in which oriented isotactic propylene (iPP) and polyethylene (PE) were alternately stacked in layr were prepared, but their physical properties such as tensile modulus and strength were not high enough to be endurable in practical use. To improve the properties, we found there are three main hurdles to overcome.Firstly, it is needed that respective layrs of iPP and PE are as thin as possible, maybe their single layr is less than 0.1 mm before drawn. In the present study, a stacked film was prepared by piling alternately the so-called 'gels' of iPP and PE which were made by crystallization these polymers from solution. When gels of iPP and PE were alternately stacked, surfaces of respective gels were rather rough, and hence it was very difficult to make the thickness of individual layrs uniform, especially when each layr was thin. A technique to make individual layrs thin and their surface flat must be developed.Since tempertature where high draw-ratio can be achieved differs between iPP and PE,it was problem to choose an appropriate temperature to draw them highly at the same time. From the present results, it was found that both polymers were smoothly drawn at the same time in the temperature range of 130ﾟC-140ﾟC.Selection and control of an appropriate drawing temperature are the second problem to be solved.Another issue to be overcome is to draw highly the stacked gel-film thus prepared. This is closely related to the above two issues.