Effect of modified tapioca starch on mechanical properties of styrene-grafted natural-rubber/starch composites

摘要

Styrene-grafted natural rubber (SNR) latex was prepared using in-situ polymerisation, and tapioca starch was modified using poly(butyl acrylate) (PBA) grafting. Unmodified starch (ST) was also used as a comparison to the modified starch (MST). Both the rubber and starch components were blended at different starch loading from 0 to 100 parts per hundred rubber (phr), and then casted at room temperature. Mechanical tests of the SNR/ST and SNR/MST blends revealed that unmodified starch decreased the tensile strength of the rubber-starch composite. However, modified starch increased the tensile strength of the composite up to an optimum loading of the starch. Modified starch has better reinforcing properties than unmodified starch due to better miscibility with the rubber component. It is believed that the PBA chain grafts inhibits the starch's ability to form intra-molecular hydrogen bonding and inhibits crystallisation in the starch, thus improving the interaction between the modified starch and rubber molecules.