Production of supertough and semiconductive PLA-based polymer blend nanocomposites by kinetic microstructural control

Abstract

Polymer nanocomposites with superior multi-functional properties can be fabricated by tuning their morphology. In this work, a supertough and semiconductive polylactide (PLA)-based polymer blend nanocomposite (PBNANO) was produced for the first time via melt blending with a core-shell rubber (CSR) and carbon nanotubes (CNT). Reference binary blends (PLA/CSR and PLA/CNT) revealed that, when added separately, 20 wt% of CSR and 0.25 wt% of CNT were the suitable quantities to achieve a supertough and a semiconductive PLA-based material, respectively. Based on the obtained results, PLA/CSR/CNT PBNANOs with 20 wt% of CSR and CNT amounts between 0.15 and 0.50 wt% were prepared in one extrusion step. Although supertoughness was achieved in all the cases, the PBNANOs were insulating due to the selective localization of the CNT in the poly(methyl methacrylate) (PMMA) shell of the CSR and the good dispersion of the CSR nanoparticles. However, a supertough and semiconductive PLA-based PBNANO was obtained by a two-step melt compounding. Using this processing sequence, a worse dispersion of the CSR was obtained, allowing contact between some CSR nanoparticles. The differences in PBNANOs morphology prepared in one or two extrusion steps were determined by TEM and corroborated by rheological measurements. In the case of the two extrusion steps PBNANO, the CNT were located in both the PLA matrix and in the shell of the CSR. This morphological change enabled the PBNANO to be conductive, as the CNT percolation was achieved in this case while still remaining supertough.