A series of stretch modes: uniaxial free width (UFW) stretching, uniaxial constant width (UCW) stretching, simultaneous equall biaxial(SEB) stretching and sequential equally biaxial (SEQEB) stretching, were applied to cast amorphous films of PLA in order to investigate the effect of processing on the structure and properties.
It is found that UFW stretching leads to higher crystallinity. SEQEB stretching is found to induce very high stress during this resulted in higher crystallinity development in the sequentially stretched films as compared to simultaneously stretched ones of comparable stretch ratios. This was attributed to the increased efficiency of strain induced crystallization in the sequential deformation mode stemming from the first stretching stage.
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