Enhancing poly(lactic acid)/maleated polypropylene blend with magnesium oxide catalyst: a reactive blending approach for improved mechanical properties

Abstract

Some defects of polylactic acid (PLA), especially its poor mechanical properties, were modified using a minimum content of non-biodegradable maleated polypropylene (MAPP). To this end, first, the amount of MAPP was optimized, which was 20 wt.%. Second, MgO was used as a new catalyst to improve the exchange reactions between active groups in both polymers in a reactive blending process. Tensile and izod analyses showed that, compared to neat PLA, with a slight decrease in modulus and tensile strength, elongation at break, and impact resistance were improved in the presence of 20 and 0.1 wt.% of MAPP and MgO, respectively. This improvement in mechanical properties can be related to the exchange reactions between two polymers and the formation of PLA-MAPP block copolymers. MFI and WDCA analyses demonstrated the increase in melt flowability and surface hydrophilicity of the resulting blends, respectively. DSC analysis showed that the T_g values of both polymers approached each other in the presence of catalyst. Also, the elimination of cold crystallization of PLA and the decrease in the T_m and crystallinity of both polymers are clear reasons for the miscibility of the alloy. TEM displayed the proper dispersion of MgO nanoparticles within the polymer matrix, and in addition, the XRD test also proved the decrease in the crystallinity of both polymers and appropriate miscibility of the samples containing 20 and 0.1 wt.% of MAPP and MgO, respectively. These results can promise the design of a compound with the maximum amount of PLA for further use in various industries.