Processing and structure–property relationships of natural rubber/wheat bran biocomposites

Krzysztof Formela,Mohammad Reza Saeb,Aleksander Hejna,Łukasz Piszczyk,Xavier Colom

doi:10.1007/s10570-016-1020-0

Abstract

In this work, wheat bran was used as cellulosic filler in biocomposites based on natural rubber. The impact of wheat bran content [ranging from 10 to 50 parts per hundred rubber (phr)] on processing, structure, dynamic mechanical properties, thermal properties, physico-mechanical properties and morphology of resulting biocomposites was investigated. For better characterization of interfacial interactions between natural rubber and wheat bran, achieved results were compared with properties of biocomposites filled with commercially available cellulosic fillers—wood flour and microcellulose. It was observed that wheat bran, unlike commercial cellulosic fillers, contains high amount of proteins, which act like plasticizers having profitable impact on processing, physical, thermo-mechanical and morphological properties of biocomposites. This is due to better dispersion and distribution of wheat bran particles in natural rubber, which results in reduction of stiffness and porosity of the biocomposites. Regardless of cellulosic filler type, Wolff activity coefficient was positive for all studied biocomposites implying reinforcing effect of the applied fillers, while tensile strength and elongation at break decreased with increasing filler content. This phenomenon is related to restricted strain-induced crystallization of NR matrix due to limited mobility of polymer chains in the biocomposites. Furthermore, this explains negligible impact of particle size distribution, chemical composition and crystallinity degree of applied cellulosic filler on static mechanical properties of highly-filled NR biocomposites. The conducted investigations show that wheat bran presents interesting alternative for commercially available cellulosic fillers and could be successfully applied as a low-cost filler in polymer composites.

Highlights

Limited petroleum resources, continuously increasing amount of polymeric wastes and higher awareness of the society, are the main economic and environmental factors causing dynamic development of biodegradable polymeric materials
In the light of above mentioned studies, we aimed to examine the effects of the Wheat bran (WB) content [in range 10–50 parts per hundred of rubber] on curing characteristics, chemical structure (FTIR analysis), thermal properties (TGA), dynamic mechanical properties (DMA), static mechanical properties, physical properties, swelling properties, and morphology (SEM) of Natural rubber (NR)/ WB biocomposites
Natural rubber based biocomposites filled with varying content of wheat bran were prepared using internal mixer and followed by cross-linking with sulfur curing system

Summary

Introduction

Continuously increasing amount of polymeric wastes and higher awareness of the society, are the main economic and environmental factors causing dynamic development of biodegradable polymeric materials. Special group of biocomposites are wood polymer composites (WPCs) which are defined as materials consisting of one or more cellulosic filler and one or a mixture of polymers. High amount of cellulose-rich by-products, generated from wood and agriculture industry, can be successfully applied as biofillers in polymeric matrix, to reduce material costs and provide specific properties of biocomposites, e.g. low density, high stiffness, corrosion resistance, low hazard, renewable characteristics and biodegradability (Gurunathan et al 2015; Mohammed et al 2015; Sobczak et al 2013). Mentioned factors account for commonly usage of WPCs as building and automobile products and as environmental friendly alternative for pure polymers (Korol et al 2015b; Teuber et al 2016)

Objectives

Results

Conclusion