Polymorphie, kristallinität und schmelzwärme von poly(ɛ-caprolactam), 2. Kalorimetrische untersuchungen

✍ Scribed by Illers, Karl-Heinz

• Publisher: Wiley (John Wiley & Sons)
• Year: 1978
• Weight: 547 KB
• Volume: 179
• Category: Article
• ISSN: 0025-116X
• DOI: 10.1002/macp.1978.021790224

✦ Synopsis

Abstract

The transition between the amorphous state and 3 crystalline modifications of poly(ε‐caprolactam) (polyamide‐6) has been investigated in Part 1 by IR spectroscopy. With these results as background the relation between heat of fusion Δ__H__* and specific volume v is now investigated as a function of crystallization temperature and time, using isothermal crystallization conditions from the melt as well as cold crystallization. The changes of Δ__H__* and v, which occur in the course of isothermal crystallization, allow qualitative statements on crystallinity changes and transitions between different crystalline modifications as a function of crystallization temperature. Quantitative results are obtained only in rare special cases, if either only one of the 3 crystalline modifications (α, γ, γ*) is formed or if the amount of one further modification is independent of crystallization time. Additionally, the situation is complicated by the fact, that for constant molecular weight and identical crystallization conditions the results strongly depend on (a) the origin of the polyamide‐6 pellets and (b) the mechanical prehistory of the melt. The reasons for these difficulties are differences in the number of (a) heterogeneous and (b) orientation‐induced homogeneous nuclei. This results in strongly varying crystallization rates, which has a considerable influence upon the relation between Δ__H__* and v.