Binary and ternary nanocomposites based on PVDF, PMMA, and PVDF/PMMA blends: polymorphism, thermal, and rheological properties

Abstract

Binary and ternary nanocomposites based on poly(vinylidene fluoride) (PVDF), poly(methyl methacrylate) (PMMA), and PVDF/PMMA blends were successfully prepared through a melt-mixing process, using a commercial organoclay (15A) as the nanofiller. The 15A was more finely dispersed (intercalated/partially exfoliated) within the PVDF matrix compared with the PMMA matrix. A higher PVDF content in the ternary composite essentially led to a superior degree of 15A dispersion. The 15A addition induced the polar β-form PVDF crystals, whereas the presence of PMMA in ternary composites reduced the efficiency in promoting β-form formation by 15A. Adding 15A also enhanced the nucleation of PVDF, but the enhancement was inferior while PMMA was present. Conversely, the crystal growth of PVDF was retarded with the existence of 15A, and the PVDF/15A binary composite exhibited the greatest retardation. The equilibrium melting temperature (Tm°) of PVDF in the neat state and in the blends increased after 15A addition. The PVDF/15A binary composite possessed an evidently higher β-form Tm° than the α-form Tm° of neat PVDF (~20.1 °C rise). Similar effects on the individual components, 15A declined the thermal stability of PVDF but increased that of PMMA in the ternary composites. Rheological property measurements revealed that the ternary composites performed in-between that of individual PVDF/15A and PMMA/15A binary composites. A percolation of 15A (pseudo)network structure was developed in the composites, and a more elastic behavior was observed with increasing PVDF content in the composites.