In-situ FTIR imaging on the plastic deformation of iPP thin films

The plastic deformation behavior of isotactic polypropylene (iPP) film is studied with in-situ Fourier transformation infrared microspectroscopic imaging (FTIRI). During uniaxial tensile test, spatial distributions of crystallinity and orientations are obtained in necking region (NR), transition front (TF) and non-necking region (NNR). A low valley of crystallinity exists at TF, while both NNR and NR have crystallinities at a high plateau. This provides a direct evidence of deformation-induced melting-recrystallization mechanism of plastic deformation. The non-monotonic evolution of amorphous orientation from NR, TF to NNR further supports the occurrence of deformation-induced melting-recrystallization. The decrease of amorphous orientation behind TF is attributed to recrystallization.

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