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A new analytical method for the optimization of thermomechanical conditions in zone drawing and its application to polyethylene

 

作者: Z. Pelzbauer,   M. Hoff,  

 

期刊: Journal of Macromolecular Science, Part B  (Taylor Available online 1990)
卷期: Volume 29, issue 2-3  

页码: 221-235

 

ISSN:0022-2348

 

年代: 1990

 

DOI:10.1080/00222349008245775

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

An original method of zone drawing of polymers at constant load and a procedure for the optimization of thermomechanical conditions (stress, temperature) are suggested, allowing high draw ratios and favorable strength values to be obtained. The temperature (or stress) range of necking has been determined in a nonisothermal and in an isothermal regime. The advantage of the method consists in that the increasing orientation in the neck starting from the initiation point and up to fracture allows the morphology and properties to be quickly examined, depending on the varying thermomechanical conditions in different regions of the neck. At a high temperature and low load the mechanism of oriented crystallization from melt becomes operative; in opposite cases, orientation of the solid state takes place. It is shown that in the nonisothermal regime an increased rate of heating allows extreme draw ratios (up to ca. 150) to be obtained, approximately twice as high as those obtained in the isothermal regime. This is interpreted as a gradual improvement of the oriented structure by recrystallization during extension and by a quick fixation on cooling below the zone.

 

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