INDUCTION TIME AS A MEASURE FOR HETEROGENEOUS SPHERULITE NUCLEATION -QUANTITATIVE-EVALUATION OF EARLY-STAGE GROWTH-KINETICS

A theory is proposed indicating that the induction time characterizes the nucleation process in polymer crystallization. A microscopic metho d has been developed to monitor early stages of the spherulite growth. Using the method, based on photometric measurement of the depolarized light intensity during isothermal crystallization from the melt, nonz ero nucleation induction time values were found for polypropylene (PP) . From comparison of the theory with the experimental results obtained from polypropylene crystallization, it follows that the formation of PP crystal nuclei on admixtures is affected both by the formation of t he first crystalline layer and by the size of the critical nucleus.