Crystallization of Poly(vinylidene fluoride) in Blends with Poly(methyl methacrylate‐co‐methacrylic acid) Copolymers

Abstract

A series of poly(methyl methacrylate-co -methacrylic acid) (PMMA-co -MAA) random copolymers ranging in MAA content from 0-15 mol% is synthesized and blended with poly(vinylidene fl uoride) (PVDF). Using infrared spectroscopy, it is observed that the absorption bands attributed to hydrogen-bonded carbonyl groups increase in intensity as the amount of MAA in the copolymer increases. In DSC analysis, the crystallization temperature of the PVDF in the blend initially decreases by ca. 12 °C with MAA contents ranging from 0 to 5.5 mol%; however, a PVDF blend with a 15 mol% MAA copolymer has a crystallization temperature that is only ca. 3 °C below that of pure PVDF. Similarly, spherulitic growth rate analysis initially shows a decrease in radial growth rate for PVDF in blends with PMMA-co -MAA copolymers containing less than 5.5 mol% MAA. At higher MAA copolymer contents, the spherulitic growth rate approaches that of pure PVDF. It is concluded that the presence of the MAA comono mer in the PMMA-co -MAA copolymer initially (<5.5 mol% MAA) increases the intermolecular interactions between the copoly mer and the PVDF. However, as the MAA content of the copolymer rises above 5.5 mol%, intramolecular hydrogen bonding interactions within the PMMA-co -MAA copolymer cause the copoly mer to be less compatible with PVDF. been used as architectural coatings due to the excellent weathering characteristics of the partially fl uorinated PVDF blend component. [ 1 ] In these coatings applications, the degree of mixing and processing conditions of the coating can alter the crystallinity of the PVDF in the blend. [ 2 ] These variations in the crystallinity can affect the fi nal performance of the architectural coating; therefore, it is important to understand the interaction of the blend components as they pertain to the degree of mixing and crystallization. Due to the low entropy of mixing, most polymer blends will not form miscible blends unless strong intermolecular interactions exist between the blend components. These interactions can cause the blend to exhibit miscibility over a large range of composition. Studies have shown that dipole-dipole interactions between PVDF and the carbonyl group of PMMA can result in melt-compatible mixtures. [ 3 ] Relative to pure

Beta Phase Crystallization and Ferro- and Piezoelectric Performances of Melt-Processed Poly(vinylidene difluoride) Blends with Poly(methyl methacrylate) Copolymers Containing Ionizable Moieties

“…In this context, FDSC consequently suggests good miscibility of PMMA-MAA with PVDF in the concentration range 5–10 wt % PMMA-MAA with slight positive influence of PMMA-MAA compared to PMMA for the β-phase production during cooling from the melt state (in particular at representative cooling rate of the extrusion-calendering process). These effects could be attributed to enhanced PVDF/PMMA-MAA interactions inducing higher miscibility with PVDF, in agreement with findings by Landis et al on PVDF crystallization in the presence of tiny amounts of PMMA-MAA …”

“…This demixing phenomenon in shearing conditions induces complex effects on PVDF crystallization (enhanced β-phase crystallization at 5 wt % PMMA-MAA and inhibited β-phase crystallization at 10 wt % PMMA-MAA). Such conclusions could agree with previous conclusions from Landis et al demonstrating that an elevated quantity of MAA moieties could have a negative effect on the resulting compatibility . Finally, differences in molecular weight between PMMA-MAA (37 500 g/mol) and PMMA (97 000 g/mol) with large subsequent differences in melt viscosity and terminal relaxation times could explain this demixing phenomena in intense shear/elongation flows.…”

“…Such conclusions could agree with previous conclusions from Landis et al demonstrating that an elevated quantity of MAA moieties could have a negative effect on the resulting compatibility. 52 Finally, differences in molecular weight between PMMA-MAA (37 500 g/mol) and PMMA (97 000 g/mol) with large subsequent differences in melt viscosity and terminal relaxation times could explain this demixing phenomena in intense shear/elongation flows. Detailled investigations are required in the future to reproduce this phenomenon in a controlled shear/elongation environment to stabilize and control the microstructure and the miscibility extent of PVDF/PMMA-MAA blends (in particular at elevated PMMA-MAA content.…”

“…These effects could be attributed to enhanced PVDF/PMMA-MAA interactions inducing higher miscibility with PVDF, in agreement with findings by Landis et al on PVDF crystallization in the presence of tiny amounts of PMMA-MAA. 52 3.2. β-Phase Crystallization in PVDF/PMMA-MAA Films Produced by Extrusion-Calendering. Taking into account FDSC results, thin films of PVDF/PMMA-MAA (thickness range of 25−35 μm) were produced by melt-state extrusion-calendering process that provide intense cooling rates (±200 °C/s depending on film thickness and materials).…”