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Processing‐Property interactions in vinylidene fluoride/trifluoroethylene random copolymers
Author(s) -
Khomami B.,
Langton C. A.
Publication year - 1991
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.760311107
Subject(s) - materials science , copolymer , differential scanning calorimetry , composite material , shearing (physics) , melt flow index , glass transition , flow birefringence , extrusion , small angle x ray scattering , crystallization , polymer chemistry , polymer , chemical engineering , scattering , thermodynamics , optics , physics , engineering
The effect of flow history, processing temperature, and exit draw ratio have been studied for copolymers of vinylidene fluoride/trifluoroethylene of molar compositions 66/34 and 75/25%. The copolymers were extruded through an impinging channels film die which produces a mixed extension and shearing flow as well as a slit die. Stress fields during flow were measured using flow birefringence. Differential Scanning Calorimetry (DSC) analyses were used to characterize the thermal behavior; and flat film and Wide Angle X‐ray Scattering (WAXS) were used to evaluate the crystal structure and morphology of the extrudates. Extensional melt stresses on the order of 6.35 × 10 5 Pa were necessary to induce sufficient orientation for crystallization of water‐cooled 66/34 mol % copolymers into the all‐trans configuration. Preorientation of the melt by extensional stresses enhanced the transformation of the 3/1 helical to an all‐trans structure in the 66/34 copolymer as well as producing a more compact unit cell in the 75/25 mol % copolymer leading to as much as a 7°C higher Curie transition temperature.