Structure, properties and interfacial interactions in poly(lactic acid)/polyurethane blends prepared by reactive processing

Polyurethane elastomers are promising candidates for the impact modification of PLA producing blends for example for biomedicine. Poly(lactic acid) (PLA)/polyurethane elastomer (PU) blends were prepared by reactive processing and physical blending as comparison. The blends were characterized by a number of techniques including microscopy (scanning electron microscopy, SEM, and atomic force microscopy, AFM), rotational viscometry, thermal (dynamic mechanical analysis, DMA), and mechanical (tensile) measurements. The analysis and comparison of the structure and properties of physical and reactor blends proved the successful coupling of the phases. Coupling resulted in more advantageous structure and superior mechanical properties compared to those of physical blends as confirmed by morphology, macroscopic properties and the quantitative estimation of interfacial interactions. Structural studies and the composition dependence of properties indicated the formation of a submicron, phase-in-phase structure which positively influenced properties at large PU contents. The results strongly support that reactive processing is a convenient, cost-effective and environmentally friendly technique to obtain blends with superior properties.