Improvement in thermal stability, elastic modulus, and impact strength of Poly(lactic acid) blends with modified polyketone

We herein report the effect of modified polyketone (PK) on the microstructure, thermal stability, mechanical modulus, and impact strength of poly(lactic acid) (PLA). For this purpose, glycidyl methacrylate-grafted poly -ketone (PKGMA) was fabricated via in-situ melt-compounding and it was melt-mixed with pristine PLA to obtain PLA-dominant blends with 10-50 wt% PKGMA loadings. The electron microscopic images revealed that PLA/ PKGMA blends showed a well-compatibilized microstructure with submicron-sized PKGMA domains in the continuous PLA matrix phase, unlike an immiscible PLA/PK blend. The infrared spectroscopic and melt-rheological analyses confirmed the specific intermolecular interactions and chemical reactions between PLA and PKGMA components in the blends. The differential scanning calorimetric data and X-ray diffraction patterns showed that the PKGMA component serves as a nucleating agent for the crystallization of PLA in the blends. The thermogravimetric analysis demonstrated that the thermal decomposition temperatures and residues of PLA/ PKGMA blends were noticeably improved, compared to pristine PLA and an immiscible PLA/PK blend. The dynamic mechanical analysis exhibited that the elastic storage moduli of PLA/PKGMA blends were higher than that of pristine PLA. Furthermore, the Izod impact strength of PLA blends increased with the PKGMA loading. The PLA blend with 50 wt% PKGMA was found to have a maximum impact strength of-286.4 J/m, which was-94% higher than that (-147.5 J/m) of pristine PLA.

Automated summary

We report the effects of modified polyketone (PK) on the microstructure, thermal stability, mechanical modulus, and impact strength of poly(lactic acid) (PLA). In-situ melt-compounding was used to fabricate glycidyl methacrylate-grafted polyketone (PKGMA), which was then melt-mixed with pristine PLA to obtain PLA-dominant blends with varying PKGMA loadings. The blended PLA/PKGMA materials showed a well-compatibilized microstructure, with PKGMA domains dispersed in the PLA matrix phase. The intermolecular interactions and chemical reactions between PLA and PKGMA were confirmed through spectroscopic and rheological analyses. The addition of PKGMA as a nucleating agent enhanced the crystallization of PLA in the blends. Furthermore, the thermal stability, mechanical modulus, and impact strength of PLA were improved with the addition of PKGMA.