Blends of Poly(butylene glutarate) and Poly(lactic acid) with Enhanced Ductility and Composting Performance

Blends of poly­(lactide) (PLA) with poly­(butylene glutarate) (PBG) have been investigated with a focus on the improvement of PLA brittleness and an enhancement of the degradation rate under industrial composting conditions. PBG was synthesized by melt polycondensation between 1,4-butanediol (C4) and glutaric acid (C5). The effect of the odd carbon atom number in the dicarboxylic acid monomer caused a decrease in melting temperature (T m) and crystalline content, and subsequently an increase in composting degradation rate. The films of PLA blended with various compositions of PBG were prepared by solution casting and hot pressing. Physical, mechanical, and viscoelastic behavior along with morphology of the blends were investigated using a variety of techniques. All PLA/PBG blends showed a decrease in both glass transition temperature (T g) and tensile strength, but showed an increase in the % elongation at break. The composting degradability of PBG and selected PLA/PBG blends were investigated using respirometry. Considering all of the analyses performed, adding PBG to PLA improved the brittleness of PLA and accelerated the rate of degradation in industrial composting. PLA/PBG blends exhibited higher ductility than the blends of PLA with poly­(butylene succinate), a polymer commonly compounded with PLA in many thermoplastic applications. The compatibility of PBG in a PLA matrix was dependent on the concentration of PBG in the PLA matrix, with phase separation evident above 3 wt %.