Study of the Properties of Polyethylene/Thermoplastic Starch Blends: Determination of the Critical Compatibilizer Concentration

The use of immiscible polymers blends is highly prevalent worldwide in view of their unique properties. Nevertheless, the main technical obstacle in the way of developing novel polymers blends remains the effective compatibilization between their components. In this work, reactive compatibilization blends consisting of thermoplastic corn starch/low density polyethylene (TPCS)/LDPE and thermoplastic corn starch/linear low density polyethylene (TPCS)/LLDPE with different portions of polyethylene-grafted-maleic anhydride (PE-g-MA) as compatibilizer were prepared. The novelty of this study is that commercial PE and starches from the local market were used to determine the critical concentration of PE-g-MA needed to attain the best blend properties. FTIR study proved that in the blends containing 7% of compatibilizer, all the available maleic anhydride groups in the PE-g-MA had reacted with the hydroxyl groups of the starch forming new ester bonds. The MFI measurements showed that when the compatibilizer was added, the melt flow index of the blend decreases down to 7% of PE-g-MA and when more compatibilizer was added no more change in MFI was noticed because of the cessation of ester bonds forming. The thermal stability improved with the increase of (PE-g-MA) concentration till 7% then it decreased again at 9%. The elongation at break and the tensile strength reached the highest value with 7 wt % of PE-g-MA.