Thermoplastic Starch-Based Composite Reinforced by Conductive Filler Networks: Physical Properties and Electrical Conductivity Changes during Cyclic Deformation.

Hamed Peidayesh,Katarína Mosnáčková,Ivan Chodák,Alena Opálková Šišková,Abolfazl Heydari,Zdenko Špitalský

doi:10.3390/polym13213819

Hamed Peidayesh, Katarína Mosnáčková + Show 4 more

Open Access

https://doi.org/10.3390/polym13213819

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Abstract

Conductive polymer composites (CPC) from renewable resources exhibit many interesting characteristics due to their biodegradability and conductivity changes under mechanical, thermal, chemical, or electrical stress. This study is focused on investigating the physical properties of electroconductive thermoplastic starch (TPS)–based composites and changes in electroconductive paths during cyclic deformation. TPS–based composites filled with various carbon black (CB) contents were prepared through melt processing. The electrical conductivity and physicochemical properties of TPS–CB composites, including mechanical properties and rheological behavior, were evaluated. With increasing CB content, the tensile strength and Young’s modulus were found to increase substantially. We found a percolation threshold for the CB loading of approximately 5.5 wt% based on the rheology and electrical conductivity. To observe the changing structure of the conductive CB paths during cyclic deformation, both the electrical conductivity and mechanical properties were recorded in parallel using online measurements. Moreover, the instant electrical conductivity measured online during mechanical deformation of the materials was taken as the parameter indirectly describing the structure of the conductive CB network. The electrical conductivity was found to increase during five runs of repeated cyclic mechanical deformations to constant deformation below strain at break, indicating good recovery of conductive paths and their new formation.

Highlights

Conductive polymer composites (CPCs) are designed by mixing an insulating polymeric matrix with conductive fillers
This fact indicates that the agglomerates of carbon black (CB) particles are still isolated, and conducting pathways are not formed in the thermoplastic starch (TPS) matrix
TPS–CB composites were obtained in the present study by incorporating CB conductive fillers into the plasticized starch matrix

Summary

Introduction

Conductive polymer composites (CPCs) are designed by mixing an insulating polymeric matrix with conductive fillers. Substantial effort has been devoted in the past decade to understanding the features of CPCs with respect to conductivity changes under external stimuli, such as thermal, electrical, mechanical, or chemical stresses [2]. Mechanical deformation is likely the most important factor that affects the structure of the conductive pathways. It can lead to substantial destruction of the filler network structure. From this point of view, investigation of the dependence of electrical conductivity on mechanical deformation is of particular interest, especially if measured for electroconductive two–phase systems consisting of an insulating flexible polymeric matrix filled with an electroconductive filler. Polymers prepared from renewable resources as matrices for solid conducting composites, including starch [4,5,6,7,8,9,10,11,12], cellulose [13], pectin [14], and chitosan [15], have been investigated

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