Abstract
Experimental data are provided on the molecular structure of paracrystalline samples of quenched melts (glasses). We propose that rods of helical molecules are present in the ‘glasses’, their length being sensitive to the temperature of the melt from which the ‘glass’ is produced, the amount of time held in the melt and the rate of quenching. A comparison is made between samples crystallized from the melt and those crystallized via the glassy phase. By measuring the lamellar thickness, from Raman spectroscopy, and calculating the absorbance ratio A 998 A 973 from infra-red spectroscopy, longer helical sequences were shown to exist to a greater extent in the samples crystallized from the melt. Samples crystallized from the glassy phase contained shorter helical sequences. In investigating the effect of the surrounding temperature on solid polypropylenes, we have shown that the density of the material can be related to the temperature of storage. We comment on the relevance of this observation to dimensional stability in mouldings.
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