Phase Transformation of Crystal Form III of Isotactic Poly-1-butene under Ambient Nitrogen and Supercritical Carbon Dioxide

摘要

The phase transformation of the crystal Form III of isotactic poly-1-butene (iPB-1) under ambient nitrogen and supercritical carbon dioxide was studied using differential scanning calorimetry, fourier transform infrared spectroscopy and polarized optical microscope. The results showed the phase transition from Form III to I' under ambient nitrogen or under scCO2 but at a low temperature was a thermodynamic selection process. At 80 o C and under scCO2, all of the Form III transformed to Form I'. The generated Form I' under scCO2 directly melt without recrystallizing to Form II during the melting process. The phase transformation from Form III to Form I' at 80 o C and under 15 MPa CO2 as a function of time was also studied. The crystallinity of obtained Form I' increased with the annealing time increasing. The POM results showed that the spherulite size increased at the early stage of the transformation.