Rheological investigation of shear-enhanced crystallization for polylactide composites with different aspect ratio carbon nanotubes

摘要

Crystallization processes of polylactide (PLA)/acid oxidized multiwalled carbon nanotube (A-MWCNT) composites were detected by dynamic rheological measurements. The influences of pre-shear, crystallization temperature, concentration and aspect ratio of A-MWCNT, on the crystallization kinetics of PLA, were investigated. The addition of small amounts of A-MWCNT, can more or less accelerate the crystallization of the PLA matrix. Composites with smaller aspect ratio A-MWCNT (A-MWCNT-S) show faster crystallization rates than those with larger aspect ratio A-MWCNT (A-MWCNT-L), due to the more heterogeneous nucleation sites of the former. Pre-shear can significantly promote the crystallization process of PLA composites, and with the increase in shear rate, the crystallization rate becomes faster. Pre-shear results in an accelerated crystallization compared to PLA/A-MWCNT-S composites at the same concentration, without pre-shear, due to a more serious deformation from entanglement to orientation of A-MWCNT-L.