Blends were prepared from poly(lactic acid) (PLA) and thermoplastic starch (TPS) to study component interactions, structure and properties. Starch was plasticized with glycerol at two levels, at 36 and 47 wt%. The results unambiguously showed that the interaction of the two components is weak. The investigation of the possible partitioning of glycerol in the two phases indicated that most of the plasticizer is located in the TPS phase. Thermodynamic modeling predicted some dissolution of PLA in TPS which was assisted by the presence of the plasticizer, but TPS did not dissolve in PLA at all. No tangible proof was found for the formation of a glycerol rich phase in TPS, the relaxation transition assigned to this phase was rather explained with the movement of smaller structural units of starch molecules. Weak interfacial adhesion does not allow stress transfer through the interface resulting in poor strength and small deformation.

Poly(lactic acid) (PLA) blends and composites were prepared from thermoplastic starch, poly(butyleneadipate-co-terephtalate), polycarbonate, wood flour and CaSO 4 in a wide range of compositions. The thermal transitions of PLA were studied by differential scanning calorimetry. The detailed analysis of the transitions of PLA/thermoplastic starch blends indicated that they all are determined by the molecular mobility of PLA chains. Blending changes molecular mobility, and thus it often decreases glass transition temperature and modifies the extent of enthalpy relaxation. All other transitions and characteristics, i.e. cold crystallization, melting and the corresponding enthalpies, change accordingly. Increased molecular mobility accelerates also the physical ageing of the polymer. The interaction between PLA and the various components used for modification changed in a wide range, but no direct correlation was found between the strength of interaction and molecular mobility.