Polyethylene/ poly(3-hydroxybutyrate-co-3-hydroxyvalerate /carbon nanotube composites for eco-friendly electronic applications

Abstract

The development of new conducting composites, for electric and electronic applications, with lower environmental impact is an increasingly relevant issue. Blending poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), a bio-based and biodegradable polymer, with conventional high-density polyethylene (HDPE), one of the most common polymers in the polymer industry and a conductive filler, such as multiwalled carbon nanotubes (CNTs), represents a suitable strategy for improving sustainability of conducting polymer composites, while maintaining procesability and functional performance. In this work conducting polymer composites based on 50/50 HDPE/PHBV matrix, an immiscible blend that can favours a segregated structure, with CNT as a conductive filler (3, 5 and 7,5%) was performed. In addition, a grafted PE was included with the aim of improving the dispersion of nanotubes within the composites. The study focuses on thermal, mechanical, morphological rheological and electrical properties. The effectiveness of the new composites for EMI shielding applications was also evaluated. Composites show a continuous structure in which CNTs remain in HDPE matrix. From rheological tests, a percolated structure for all composites is observed that is related to the fact that all composites show a certain level of conductivity. Without compatibilizer, only the composite with 7,5% of CNTs achieves a conductivity value suitable for reaching 20 dB of electromagnetic shielding. In composites with PE grafted with maleic anhydride (0.5%) the electrical conductivity substantially increased, achieving a suitable EMI shielding level with small proportion of nanotubes (5 wt%) probably related with an improvement in the interfacial adhesion between polymer phases and CNT dispersion. Summarizing, composites with reduced environmental impact have been obtained suitable for EMI applications with a reasonable amount of CNTs.