On the effect of the crystallization temperature on the habit and fold length of polyethylene single crystals

In the course of crystallizing polyethylene from octane a number of observations were made on the prism face development and fold length, as a function of crystallization temperature, which are thought to be relevant to the more general problem of polymer crystallization. Prism face development has revealed a trend towards a particular {110}–{100} sector ratio which was found to have the unique properties of ensuring both optimum fold surface fitting and fold plane continuity. The implications of this are discussed. Some relevant problems in spherulite growth are also touched upon. It is concluded from the observed relationships between fold length and temperature of crystallization, explored in two solvents, that the fold length is primarily determined by supercooling in support of kinetically controlled chain folding. The importance of these observations for the more general problems of polymer crystallization is indicated.