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The orientation of cross-linked poly(vinylidene fluoride) crystallized from oriented amorphous melts
Radiation crosslinked samples of poly(vinylidene fluoride) (PVF$\sb2$) were obtained from the Raychem Company, heated to above their crystalline melting point, stretched and isothermally recrystallized at 100$\sp\circ$C.^ The crystalline and amorphous orientation functions were studied as a function of crosslink density and extension ratio by X-ray diffraction and birefringence. The crystalline phase orients with its c-axis parallel to the deformation direction and the amorphous phase orients perpendicular to the deformation direction. The degree of orientation increases with both the crosslink density and the extension ratio.^ Values of both the crystalline and amorphous intrinsic birefringences of PVF$\sb2$ are offered. The intrinsic birefringence of the amorphous phase, calculated from bond polarizabilities and birefringence measurements using rubber elasticity theory, equals 0.098 $\pm$ 0.017. The intrinsic birefringence of the alpha crystalline phase is calculated from bond polarizabilities using the differentiated Lorentz-Lorenz equation and is equal to 0.145 $\pm$ 0.002.^ Each of the samples are characterized in terms of their polymorphic form by wide angle X-ray diffraction, their molecular weight using Flory-Rehner theory, and their degree of crystallinity from density measurements. In addition a value of 0.15 is offered for the polymer-solvent interaction parameter in N,N-dimethylacetamide.^ Finally, attempts at drawing a correlation between the amorphous orientation functions of molten PVF$\sb2$ samples and the orientation functions of these same samples after crystallization indicate that the crystalline orientation functions indeed depend upon the amorphous orientation functions of the deformed molten network rather than upon the crosslink density or extension ratio of the samples taken separately. ^
Polymer chemistry|Materials science|Plastics
Spector, Kenneth Steven, "The orientation of cross-linked poly(vinylidene fluoride) crystallized from oriented amorphous melts" (1989). Doctoral Dissertations Available from Proquest. AAI9001569.