Evident improvement in burning anti-dripping performance, ductility and electrical conductivity of PLA/PVDF/PMMA ternary blend-based nanocomposites with additions of carbon nanotubes and organoclay

Abstract

In this study, carbon nanotubes (CNTs) and organoclay (30B) were introduced into poly(lactic acid) (PLA)/poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) (70/30/30) ternary blend, with PMMA acting as a compatibilizer for the PLA and PVDF phases. Morphological results indicated that PMMA tended to entangle more with PVDF than with PLA, and thus formed a pseudo co-continuous PLA(rich)-PVDF(rich) phase morphology in the blend. The added CNTs and 30B clay were mainly distributed in the PVDF(rich) phase and PLA(rich) phase, respectively, to achieve nanocomposites. The co-continuous bi-phasic morphology was more evident in the composites than in the parent blend. Thermal property results revealed the nucleation effect of CNTs and 30B on the crystallization of PLA and PVDF; the presence of PMMA obviously retarded the crystal growth of PVDF due to their miscibility. Adding CNTs or hybrid CNT/30B evidently improved the anti-dripping performance of the ternary blend in burning tests. The ductility (elongation at break) of PLA/PVDF blend drastically improved with PMMA inclusion, and the composites also showed excellent ductility. The ductility of PLA and PLA/PVDF blend increased by up to 18.9 and 14.4 times, respectively, after forming the 3-phr hybrid CNT/30B-loaded composite. Rigidity of the ternary blend increased after forming the composites; flexural modulus increased by 16% with 3 phr CNT inclusion. Rheological properties revealed the (pseudo)network structure development in the composites. The electrical resistivity of the ternary blend reduced by 11 orders at 2 phr CNT loading (double percolation achieved), and the percolation threshold was at 0.5 phr CNT loading.