The compatible and mechanical properties of biodegradable poly(Lactic Acid)/ethylene glycidyl methacrylate copolymer blends

The Fourier transform infrared results suggest that the carboxylic acid groups of poly(lactic acid) (PLA) molecules react with the epoxy groups of molecules of Ethylene Glycidyl Methacrylate Copolymer (EGMC) during the reactive extrusion processes of PLA(x)EGMC(y) specimens. The tensile and tear strength values of PLAxEGMCy blown-film specimens in machine and transverse directions improve significantly, and reach their maximal values as their EGMC contents approach an optimum value of 6 wt.%. The melt shear viscosity values of PLAxEGMCy resins, measured at varying shear rates, are significantly higher than those of the PLA resin, and increase consistently with their EGMC contents. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) of PLA and PLAxEGMCy specimens reveal that the percentage crystallinity, peak melting temperature, and onset recrystallization temperature values of PLAxEGMCy specimens reduce gradually as their EGMC contents increase. In contrast, the glass transition temperatures of PLAxEGMCy specimens increase gradually in conjunction with their EGMC contents. Demarcated porous morphology with several connected fungi-decomposed cavities was found on the surfaces of the PLAxEGMCy specimens after being buried for specific amounts of time, in which the sizes of the fungi-decomposed cavities found on the surfaces of buried PLA(x)EGMC(y) specimens reduce significantly as their EGMC contents increase. Further DMA and morphological analysis of PLA(x)EGMC(y) specimens reveal that the EGMC molecules are compatible with PLA molecules at EGMC contents equal to or less than 2 wt.% because no phase-separated EGMC droplets and tan delta transitions were found on fracture surfaces and tan d curves of PLA(x)EGMC(y) specimens, respectively. The possible reasons for these remarkable properties of the PLA/ EGMC specimens are proposed in this study.