Amorphous and Semicrystalline Blends of Poly(vinylidene fluoride) and Poly(methyl methacrylate): Characterization and Modeling of the Mechanical Behavior

After extensive studies starting in the 1970s in relation to miscibility and piezoelectric properties, the blends of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) have been revisited with the aim of assessing their mechanical behavior. Depending on the amount of PVDF, either amorphous or semicrystalline blends are produced. Typically, the blends remain amorphous when their PVDF content does not exceed 40 wt. %. Blend composition influence on the values of the glass transition temperature, T_g, and on its mechanical expression, T_α, is extensively discussed. Then, emphasis is put on the stress-strain behavior in tension and compression over the low deformation range covering the elastic, anelastic, and viscoplastic response. The reported data depend, as expected, on temperature and strain rate and also, markedly, on blend composition and degree of crystallinity. Molecular arguments, based on the contribution of the glass transition motions are proposed to account for the observed behavior. Thanks to the understanding of phenomena at the molecular level, accurate models can be selected in the view of mechanical modeling.