Effect of annealing on the mechanical properties of PLA/PCL and PLA/PCL/LTI polymer blends.

The effects of annealing on the mechanical properties of polymer blends of poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) were investigated. The bending strength and modulus of PLA/PCL tend to increase due to crystallization of the PLA phase by annealing. The mode I fracture energy, J(in), of PLA/PCL decreases dramatically due to the suppression of the ductile deformation of the spherical PCL phase by annealing. The immiscibility of PLA and PCL can be improved by adding lysine triisocyanate (LTI) as a result of additional polymerization. The phase transformation due to LTI addition reduces the size of the spherical PCL phase, resulting in higher fracture energy. An annealing process applied to PLA/PCL/LTI further strengthens the microstructure, resulting in effective improvement of the fracture energy.