Effect of nanowhisker-modified zeolites on mechanical and thermal properties of poly(vinyl acetate) composites with pure-silica MFI

The effect of nanoscale surface morphology of pure-silica MFI zeolite on the interfacial, mechanical, and thermal properties of pure-silica MFI zeolite/poly(vinyl acetate) (PVAc) composites was investigated under different annealing conditions. Mg(OH)2 inorganic whisker- or asperity-like nanostructures were achieved on MFI nano- and micro-particle surfaces via Grignard or solvothermal treatment. The creation of nano-roughness on the MFI surface promoted compatibility between the zeolite and the polymer matrix, resulting in void-free interfaces. PVAc composites containing surface-modified particles showed increased tensile strength and elongation at break as compared with composites containing unmodified zeolite. Surface modification of the microparticles exhibited interfacial and mechanical enhancement over a wider range of annealing temperatures than nanoparticles. Differential scanning calorimetry revealed that surface treatment of MFI resulted in broader glass transitions compared to composites containing unmodified MFI. This is explained by improved interfacial adhesion and associated slower chain relaxation dynamics. Furthermore, X-ray diffraction demonstrated that enhanced adhesive interactions between the PVAc and the MFI surface are associated with surface-induced orientation of the MFI particles within the polymer matrix. The optimal surface morphology, associated with the most enhanced mechanical and thermal properties of composites, was produced with the solvothermal method.