Influence of Protonic Ionic Liquid on the Dispersion of Carbon Nanotube in PLA/EVA Blends and Blend Compatibilization

Elaine Cristina Lopes Pereira,Bluma Guenther Soares,Ketly Pontes,Maria Eduarda C Fernandes Da Silva

doi:10.3389/fmats.2019.00234

Abstract

In this work, immiscible poly(lactic acid) (PLA)/poly(ethylene vinyl acetate) (EVA) composites with 1 phr of multi‐walled carbon nanotube (CNT) and different concentration of protonic – based imidazolium ionic liquid (mimbSO3H.Cl) were prepared. The protonic ionic liquid (IL) was able to act as dispersing agent for CNT and as compatibilizing agent for the PLA/EVA blend. The multicomponent nanocomposites from the mixture of PLA and EVA containing CNT functionalized with ionic liquid, IL (CNT/ILSO3H) were characterized by mechanical and dynamic - mechanical (DMA) tests, electrical conductivity analyses, differential scanning calorimetry (DSC), X-ray diffraction analysis and rheological measurements, as well as chromatographic gel permeation (GPC), and scanning electron microscopy (SEM). The non covalent functionalization CNT resulted in composites with outstanding electrical and dielectric properties. The high dispersion of CNT promoted by the IL resulted in the formation of a physical networked structure, which was responsible for the higher electrical conductivity and higher melt viscosity. The crystallization process of PLA phase was improved with the presence of CNT/ILSO3H. The degradation process during the transesterification reaction did not significantly affect the mechanical properties. The present work highlights the dual role of the IL as compatibilizing and dispersing agent and opens new perspectives for developing new conducting systems with low percolation threshold based on the good dispersion of CNT and the confinement of the filler within a phase of a multiphasic polymeric system.

Highlights

Due to the widespread use of plastics in the packaging industry, there is a growing interest in the use of biodegradable polymers as a substitute for conventional polymers to reduce the environmental impact of plastic waste
Based on the importance of the theme for the electroelectronic, automobile and packaging industries, the aim of the present study is to investigate the efficiency of the protonic ionic liquid (IL) based on imidazolium cation as a dispersing agent for carbon nanotube (CNT) in Poly lactic acid (PLA)/ethylene-vinyl acetate copolymer (EVA) blends and how the IL-CNT combination should affect the compatibility, morphology, electrical conductivity, mechanical and rheological properties
It is important to investigate the effect of CNT and CNT/ILSO3H on the rheological parameters of the PLA/EVA blends

Summary

Introduction

Due to the widespread use of plastics in the packaging industry, there is a growing interest in the use of biodegradable polymers as a substitute for conventional polymers to reduce the environmental impact of plastic waste. Besides being biodegradable and biocompatible, PLA presents good processability when compared with other biodegradable polymers. It is quite rigid and brittle, CNT Dispersion in PLA/EVA Blends presents low moisture resistance and slow crystallization rate, which in turn limit its applications. The appropriate choice of non-biodegradable polymers as component for PLA-based blends should reduce the biodegradation rate, cost and improve some mechanical properties. In these cases, the PLA phase undergoes a gradual degradation process, known as biodisintegration, resulting in very small pieces of the non-biodegradable polymer (Sarasa et al, 2009). Several papers have used EVA with different vinyl acetate content for the preparation of PLA/EVA blends for different purposes (Yoon et al, 1999; Li et al, 2011; Moura et al, 2011, 2012; Ma et al, 2012, 2015; Aghjeh et al, 2015, 2016; Sangeetha et al, 2016, 2018; Wang et al, 2016; Zhang and Lu, 2016; Lopes Pereira et al, 2017)

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