Paper Title
Influence of Straw with Different Average Size as Biofiller on The Properties of Natural Rubber Composites

Abstract
In the recent years, great attention was dedicated to the application of natural fibres (mainly hemp, flax, sisal and cotton fibers) as reinforcement for thermosetting and thermoplastic materials, replacing glass fibres and other synthetic fillers. The objective of this study was to develop a new type of elastomer material-straw reinforced natural rubber (NR) composite. Cereal straw was mechanically crushed in three different ways: by rotating grinder, mixer and ball mill. Addition of the lignocellulosic materials with different average size modify natural rubber, obtaining multifunctional elastomer composites with meaningly extended applications. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and microscopy techniques were used for characterization of fillers. The kinetics characteristics and rheometric properties of rubber mixtures were determined. The cross-linking density was executed on the basis of equilibrium solvent-swelling measurements applying the modified Flory–Rehner equation. The fragmentation degree of straw influenced the mechanical and physical characteristic of biocomposites. Moreover, the values of hardness, tensile strength, tear strength, elongation at break, relative damping coefficient and thermooxidative aging factor were examined. Straw-reinforced natural rubber offered several advantages such as improved tensile modulus, resistance to tear, damping properties and positive thermal aging properties. The degree of fragmentation influenced the activity of the filler, the small filler particles created an extended spatial network in the elastomer, thus contributing most likely to the increase in the crosslinking density, stiffness and mechanical strength. Furthermore, application of straw in preparation of natural rubber composites is an ecologically, sparingly and economically advantageous solution. Keywords: Natural Rubber, Straw, Fillers, Elastomer Biocomposites, Multifunctional Properties.