Thermoplastic Elastomeric Composites Filled with Lignocellulose Bioadditives. Part 1: Morphology, Processing, Thermal and Rheological Properties

Thermoplastic elastomer blends based on natural rubber (NR) and ethylene-vinyl acetate copolymer (EVA) with different weight ratios (30, 40, 50, 60 and 70 parts per hundred rubber (phr) of NR) and 10, 20 and 30 phr of straw were prepared and characterized. Current environmental problems were the motivation to produce this type of system, namely: the need to replace plastics at least partly with natural materials; increasing the amount of renewable raw materials and managing excess straw production. When using this bioadditive in traditional materials, the high processing temperature can be problematic, leading to the degradation of straw fibers. The solution can be polymer mixtures that are prepared at significantly lower temperatures. Scanning electron microscope (SEM) imaging was used to investigate the particle size of fibers and phase morphology of composites. Moreover, determination of the thermal properties of the filler and composites showed that the processing temperature used in the production of NR/EVA blends reduces the risk of degradation of the natural filler. Differential scanning calorimetry (DSC) was used to determine the thermal behavior of the filled composites. Finally, rheological tests of materials allow the determination of optimal processing parameters and properties of materials in dynamic conditions. The proposed blends exhibit elastic properties, and due to the lack of chemical cross-linking they can be processed and recycled like thermoplastics. In addition, they offset the disadvantages and combine the advantages of natural rubber and ethylene-vinyl acetate copolymer in the form of thermoplastic elastomeric biocomposites.