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Melting of crystallites in polymers with low degree of crystallinity under shear flow conditions I: Poly(vinyl chloride)
Author(s) -
LyngaaeJørgensen J.
Publication year - 1974
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760140507
Subject(s) - materials science , crystallite , crystallinity , rheometer , degree of polymerization , vinyl chloride , polymer , polymerization , shear (geology) , composite material , polymer chemistry , degree (music) , shear rate , thermodynamics , rheology , physics , copolymer , acoustics , metallurgy
The aggregates found in dilute solutions of nearly atactic PVC have been shown to consist of 10 to 15 single molecules held together by a crystalline nucleus. Based on the postulate that the last crystallites in a PVC melt have the same structure as found in dilute solution, a relation between the melting temperature in shear ( T dyn ), the static melting temperature ( T m ) and the shear stress (τ) is found:\documentclass{article}\pagestyle{empty}\begin{document}$$ {1 \mathord{\left/ {\vphantom {1 {T_{{\rm dyn}} }}} \right. \kern-\nulldelimiterspace} {T_{{\rm dyn}} }} - {1 \mathord{\left/ {\vphantom {1 {T_m }}} \right. \kern-\nulldelimiterspace} {T_m }} = \frac{{\tau ^2 }}{{Q \cdot T_{{\rm dyn}} ^2 }} $$\end{document} where Q is a constant. The model predictions are in accordance with data from a Brabender rheometer and a Rheometrics mechanical spectrometer. Q is found to be a constant for samples with weight average molecular weights in the interval between 70,000 and 160,000 corresponding to polymerization temperatures between 40 and 70°C.