The effect of deformation rate on fundamental deformation-structure relationships in melt cast amorphous Poly(lactic acid) (PLA) films was investigated using a stretch birefringence apparatus that allows for direct measurement of true stress, true strain, and birefringence. Crystalline phase behavior was elucidated with WAXD and DSC. Relationships between stress, strain, and birefringence are strongly affected by stretching rate. The effect of stretching rates on the molecular mechanisms of uniaxial deformation in rubbery state PLA films and its affect on the various levels of structure are elucidated in this study.
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