Properties of Thermoplastic Elastomer Composites Prepared from Para Rubber Wood Sawdust Filled-Polypropylene/Natural Rubber Blends

Abstract

Thermoplastic elastomer composites (TEC) based on blending of polypropylene (PP) and natural rubber (STR5L) filled with Para rubber wood sawdust were prepared by melting polypropylene at 180 °C in the internal mixer followed by adding STR5L and subsequently Para rubber wood sawdust. The size of Para rubber wood sawdust used were less than 800 μm. Thermoplastic elastomer composite compounds were compression molded at 180 °C for 13 min. for specimen preparation. The effect of blend ratios and Para rubber wood sawdust loading on the mechanical and physical properties of TEC were investigated. It was found that tensile strength, Young’s modulus, hardness and flexural strength of TEC decreased with STR5L and Para rubber wood sawdust loading, whereas the impact strength increased with increasing STR5L. It was obvious that loading of Para rubber wood sawdust didn’t change impact resistance and hardness of TEC. Furthermore, it was clarified that TEC (PP:STR5L:Sawdust) with the weight ratios of 90:10:30, 90:10:50, 70:30:30 and 70:30:50 showed the best mechanical properties. Accordingly, they were selected for further measurements of the water absorption and flexural properties for application to flooring. The water absorption of TEC was determined by immersing the composite samples in distilled water for 24 h at room temperature. The results showed that water absorption of TEC with the ratios of 70:30:30 and 70:30:50 was 0.25% and 1.64%, respectively, compared to the standard value of ≤ 3% for low water absorption ceramic tiles, ≤10% for medium absorption ceramic tiles and ≥10% for high water absorption ceramic tiles regarding to Thai Industrial Standards. For flexural properties, all selected TEC showed flexural modulus higher than 700 MPa which was the minimum requirement of Thai Industrial Standard (≥ 700 MPa). However, only TEC with the weight ratio of 90:10:30 gave the modulus strength reach to Thai Industrial Standards value of ≥30 MPa. Morphology of the cracked surface from the notched impact specimens with the weight ratio of 90:10:50 and 70:30:50 was examined by using Scanning Electron Microscopy (SEM). It indicated that the interfacial bonding between Para rubber wood sawdust and the polymer matrix of TEC with 90:10:50 ratio was poorer in comparison with that of 70:30:50 due to the numerous pulled-out sawdust flakes of TEC with 90:10:50 ratio observed much more than TEC with 70:30:50 ratio. This result indicated that adhesion between filler and polymer matrix of TEC with 30% STR5L blending was obvious to be stronger than that with 10% STR5L blending. As a result, it was remarkable that thermoplastic elastomer composites prepared with three immiscible materials showed acceptable mechanical and physical properties for application to flooring product with the economical process.