Flexibility Improvement of Poly(L-lactide) by Reactive Blending With Poly(ether urethane) Containing Poly(ethylene glycol) Blocks

Poly( L -lactide) (PLLA) is melt blended with poly(ether urethane) (PEU) based on poly(ethylene glycol) blocks via a chain-extension reaction by diisocyanate as a chain extender to improve its flexibility without sacrificing comprehensive performance. The elongation at break of the blends with triphenyl phosphate (TPP) as a reactive blending additive is much higher than that without TPP by physical blending. When 10 wt% PEU is blended, the former elongation reaches to 298%, while the latter one is only approximately 20%. The reactive blending forms a PLLA–PEU block copolymer, thus improving their compatibility. When the weight-average molecular weight ( M w ) of PEUs is 18–90 kg mol −1 , the effect of M w is very little on tensile properties of blends. The rheological properties of the blends are modified through the content and molecular weight of PEU. The complex viscosity ( η *) of PLLA/PEU blends increases with increasing M w of PEU. The η * of the PLLA blend containing 5 wt% PEU in M w 73 kg mol −1 is higher than that of neat PLLA. The water absorption of the PLLA/PEU blends enhances because of the hydrophilicity of PEUs versus neat PLLA.