Effect of Maleic Anhydride Grafted Polylactic Acid Concentration on Mechanical and Thermal Properties of Thermoplasticized Starch Filled Polylactic Acid Blends

In the present situation, the disposal of large quantities of petroleum-based plastics has become a major environmental concern. Many polymers, such as polycaprolactone, polylactic acid (PLA), polybutylene terephthalate, have gained significant commercial interest as alternatives to conventional thermoplastics such as polypropylene and high-density polyethylene. Because they are biodegradable. However, their use is limited to specific areas due to high cost and limited availability.

Polylactic acid is synthesized from renewable agricultural products, such as corn starch, and its processing capacity is very similar to that of polyolefin. However, high brittleness, low thermal stability and high cost limit its application in limited products. Economical plasticizers are needed to reduce brittleness in the material, and suitable fillers, preferably natural, are needed to reduce costs. Biodegradable composites were prepared by mixing polylactic acid (PLA) with natural starch or thermoplasticized starch (TPS). However, the poor compatibility between polylactic acid and starch results in the poor mechanical properties of the composites. The effects of maleic anhydride-PLA (GMAPLA) coupling agent and its concentration on the improvement of the physical and thermal properties of PLA-tps blends were investigated. Maleic anhydride was grafted onto polylactic acid as coupling agent. PLA/TPS (wt/wt) blends (70/30 and 50/50) were prepared by double screw extrusion method. The effects of three different levels of GMAPLA containing 5%, 10% and 15% (wt%) PLA on the material properties of the blends were studied. The mechanical properties (tensile, bending and impact strength) of TPS/PLA blends were significantly improved by the presence of GMAPLA. Among the three concentrations, 10% GMAPLA in the blend improved the strength properties the most. Dynamic mechanical analysis and thermogravimetric analysis showed that GMAPLA content had no significant effect on transition temperature and thermal temperature.

(a)Starch, (b)TPS（10000), (c)TPS（25000）