Effect of ageing the glass of isotactic polypropylene on cold-crystallization/ordering

摘要

Fast scanning calorimetry has been employed to study the effects of temperature and time of ageing the amorphous glass of isotactic polypropylene on the kinetics of cold-crystallization/ordering on subsequent heating. The relaxed melt was quenched into the glassy state at a rate of 104 K s-1 which suppressed both crystallization and mesophase formation on cooling. Subsequently, samples were aged at 220, 230, 240, or 250 K for different time between 0 and 104 s. Ageing of the glass led to classical enthalpy relaxation but also the formation of homogeneous nuclei both as a function of temperature and time. The kinetics of the latter process was quantitatively evaluated by analysis of cold-ordering on subsequent slow heating above the glass transition temperature. It has been found that increasing temperature and time of ageing the amorphous glass of isotactic polypropylene leads to increasing number of homogeneous nuclei which distinctly affects the kinetics of ordering processes above the glass transition temperature. The results obtained on isotactic polypropylene are compared with data collected earlier on poly(e-caprolactone).