Unraveling the blend composition influence on crystallization, melting, thermal stability and rheological behavior of PMMA/EVA/MWCNTs nanocomposites

In this research, the thermal behavior and stability as well as the rheological properties of the nanocomposites containing 5 wt% multi-walled carbon nanotubes (MWCNTs) filled poly (ethylene-co-vinyl acetate) (EVA)/poly (methyl methacrylate) (PMMA) blends of different blend compositions were investigated. It was confirmed by employing the Winter-Chambon model that the physical gels were formed for the nanocomposites containing 70 wt% EVA and beyond. Hence, they behaved as shear thinning fluids throughout the angular frequency range examined. Moreover, the relaxation exponent, gel strength and fractal dimension of the critical gel were estimated to be about 0.309, 41,304 Pa.s n and 2.21, respectively. The calculation of the wetting coefficient revealed that the MWCNTs thermodynamically tended to migrate from EVA and locate inside the PMMA phase. The results obtained from the crystallization and melting rate of the materials indicated that the crystallization rate was always higher than that of the melting rate and both progressively decreased with the increase in PMMA loading for the nanocomposites. Thermogravimetric analyzer (TGA) was employed to study the thermal stability of the nanocomposites under air and nitrogen atmosphere. The highest thermal stability for air-scanned materials were found for the nanocomposites containing 85 wt% followed by 70 wt% EVA as if their thermal stabilities were even superior to that of the pristine EVA. For instance, the temperature at 50 and 70 wt% weight loss for the nanocomposite containing 85 wt% EVA was found to be 20 and 23°C higher than those of the EVA alone, respectively.