CRYSTALLIZATION AND FUSION OF SELF-SEEDING POLYMERS .I. POLY-1-BUTENE POLYETHYLENE AND POLYOXYETHYLENE OF HIGH MOLECULAR WEIGHT

The self-seeding technique for obtaining homogeneous single crystal preparations from solution has been applied to the crystallization of molten polymers. It has been shown that the growth of spherulites can be initiated almost simultaneously by submicroscopic crystallin fragments, which were stabilised by annealing. The concentration and the size of these fragments depend on the thermal history of the sample, in particular on the maximum temperature Ts, at which the sample was melted before recrystallization. Nevertheless, a fraction of the nuclei, related to some impurities in the specimens, appeared to persist permanently, since their number was independent of the temperature Ts. Thus the total concentration of these two types of nuclei, estimated from crystallization kinetics (as determined from dilatometry) and from the spherulitic growth rate (as measured microscopically), varies discontinuously with Ts. The critical temperature Tf* is near, but smaller than, the equilibrium melting point Tf0, the difference being related to the volume of the nuclei produced by selfseeding. These various effects were analysed and discussed on the basis of extensive experimental data obtained with high molecular weight samples of (isotactic) polybutene-1, polyethylene and polyoxyethylene. In addition the changes in nuclei concentration produced some specific effects on the isothermal crystallization kinetics of these samples. These effects were related to the structural features of the spherulites. © 1969 Dr. Dietrich Steinkopff Verlag.