Biocomposites made from starch and natural fibers: study of a new processing method and modeling of the biocomposites mechanical properties

Abstract

Biocomposites made from starch and natural fibers were studied in this work. Starch is abundantly produced by fractionation processes of crops and legumes while natural fibers, such as flax and hemp fibers, are largely produced in Europe. A new processing method, through microwave-assisted plasticization, was studied in this work. Thermoplastic starch (TPS) samples were produced from pea starch, glycerol and water. Low percentages of starch (20% (w/w)) and high temperatures (190°C) gave the most optimal results in terms of homogeneous plasticization and ability to be molded. Flax, hemp and microcrystalline cellulosic natural fibers were processed with the selected TPS matrices to create biocomposites. FTIR analyses and optical microscopy highlighted the presence of matrix around the fibers, indicating a good compatibility between the initial components. No degradation of the TPS matrix or the fibers relatable to the microwave process was identified. The fibers and starch composition of biocomposites, as well as their processing parameters, were related to their tensile test measurements through multilinear regression modeling. The database built with TPS and biocomposites data gave models with most of the variability explained when studying the Young’s modulus and tensile strength (R² > 0.96). The analysis of the regression coefficients significance indicated that many variables and interactions had an impact on the mechanical properties of the final material. To help the scientific literature in their further research, a list of significant parameters was produced.