Open AccessCritical specific work of flow for shear‐induced formation of crystal nuclei in poly ( l ‐lactic acid)
Author(s) -
Iqbal Naeem,
Jariyavidyat Katalee,
Rhoades Alicyn M.,
Androsch René
Publication year - 2019
Publication title -
polymer crystallization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.443
H-Index - 9
ISSN - 2573-7619
DOI - 10.1002/pcr2.10073
Subject(s) - shear rate , shearing (physics) , rheometer , shear (geology) , materials science , crystallization , shear flow , kinetics , composite material , thermodynamics , viscosity , rheology , classical mechanics , physics
Shear‐induced formation of crystal nuclei in the poly ( l ‐lactic acid) homopolymer was analyzed by shearing the supercooled melt in a plate‐plate rheometer followed by evaluation of the kinetics of isothermal crystallization via viscosity measurements. The data revealed that shearing the melt for 10 seconds at 135°C and 140°C causes shear‐induced formation of nuclei if the shear rate is higher than about 0.1 s −1 . If the shear rate at these conditions is higher than about 1 s −1 then row‐nuclei, as detected by aligned spherulites, develop. Besides providing comprehensive data about the effects of rate and time of shear at 135°C and 140°C on the crystallization kinetics, the concept of specific work of flow was tested. Shear rate and time compensate each other to drive shear‐induced nuclei formation, and the critical specific work required to form shear‐induced crystal nuclei is around 20 to 50 kPa. Further conceptual work included the analysis of the microstructure along the radius of the sheared discs as it permits evaluation of the effect of a broad range of shear rates in a single experiment.