Studying deformation behavior of a single spherulite with in-situ infrared microspectroscopic imaging

The deformation behavior of a single spherulite embedded in quenched isotactic polypropylene (iPP) film is studied with in-situ infrared microspectroscopic imaging (FTIRI) with Focal Plane Array (FPA) detector during uniaxial tensile test. Imaging an area of 250 × 250 μm2 with 4096 Fourier transform infrared (FTIR) spectra, the absorption distributions of crystalline (998 cm−1 band) and amorphous (1153 cm−1 band) phases with radiation polarized parallel and perpendicular to tensile direction are obtained, which are employed to construct the orientation distribution images at different strains. The daughter lamellae in equatorial region are slightly rotated first toward tensile direction, which may postpone the sliding deformation of parent lamellae. The orientation evolution of crystal during tensile deformation suggests that a single spherulite can be divided into three different mechanical zones, corresponding with the crystallinity distribution at different regions of spherulite as estimated through the ratio of 998 cm−1 to the summation of 998 cm−1 and 1153 cm−1. The results may provide a more realistically mechanical model for computer simulation and demonstrate the advantages of FTIRI on the study of structure-property of polymers.