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Poly(ε-caprolactone) (PCL) is a ductile, bioabsorbable polymer that has been employed as a blend partner for poly(L-lactic acid) (PLLA). An improvement of the material strength and impact resistance of PLLA/PCL polymer blends compared to pure PLLA has been shown previously. To use numerical simulations in the design process of new components composed of the PLLA/PCL blend, a constitutive model for the material has to be established. In this work, a constitutive model for a PLLA/PCL polymer blend is established from the results of compressive tests at high and low strain rates at three different temperatures, including the body temperature. Finite element simulations of the split Hopkinson pressure bar test using the established constitutive model are carried out under the same condition as the experiments. During the experiments, the changes in the diameter and thickness of the specimens are captured by a high-speed video camera. The accuracy of the numerical model is tested by comparing the simulation results, such as the stress, strain, thickness and diameter histories of the specimens, with those measured in the experiments. The numerical model is also validated against an impact test of non-homogenous strains and strain rates. The results of this study provide a validated numerical model for a PLLA/PCL polymer blend at strain rates of up to 1800 s(-1) in the temperature range between 22°C and 50°C., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

This study investigated important mechanical properties, the flexural strength and flexural modulus, of polyglycolic acid (PGA) fiber-reinforced polylactic acid (PLA) composites fabricated by melt-mixing. The flexural strength and flexural modulus were estimated using three-point bending tests conducted at 37°C. Both the flexural strength and flexural modulus were increased by PGA fiber reinforcement. Viscoelastic properties were also investigated using dynamic mechanical analysis (DMA) under tensile loading. Results show that PGA fiber, which acts as the nucleate agent of PLA, restrains the molecular chains of PLA. That restraint reduces deformation at the same stress condition, thereby improving the PLA flexural properties. [ABSTRACT FROM AUTHOR]

The article focuses on the effect that lysine triisocyanate (LTI) has on the fracture behavior of poly(butylene succinate-co-L-lactate) (PBSL) and poly(L-lactic acid) (PLLA). It states that the fracture properties of PLLA are better than of polystyrene and other brittle polymers but is significantly lower than high-toughness engineering polymers. It mentions that the addition of LTI can result in a dramatic improvement in the immiscibility in blended systems of PLLA and poly(butylene succinate). It comments that the incorporation of LTI into PLLA/PBSL will improve the immiscibility between the two polymers and suppress spherulite formation of PBSL.

LTI was attempted to modify the microstructure of poly ( l-lactic acid) (PLLA) and to improve its mechanical properties in this study. Bending modulus, strength and fracture toughness of PLLA/LTI were evaluated, and compared to those of the base PLLA to assess the effectiveness of LTI blending. Effect of LTI addition on fracture micromechanism was also investigated by observing and comparing the fracture surfaces of PLLA/LTI and PLLA using a field emission scanning electron microscope (FE-SEM). Experimental results showed that the bending properties such as the bending modulus and the strength are effectively improved due to polymerization of PLLA molecules by LTI blending. The fracture toughness value was also improved due to increase of ductile deformation, i.e., energy dissipation in the crack-tip region. [ABSTRACT FROM AUTHOR]

The blends of poly (lactic acid) (PLA) and poly (ε-caprolactone) (PCL) were prepared by melt blending using lysine triisocyanate (LTI) as a compatibilizer to improve blend miscibility. Critical J-integral at crack initiation, Jin, was measured as a fracture energy parameter, and crystallinity, xc, PLA, and molecular weight, Mw, were evaluated by DSC and GPC, respectively. Jin and Mw tend to increase, while xc, PLA decreases, as the LTI content increase. Increased Mw and reduced xc, PLA are both considered to be due to crosslinking reaction of added LTI. It is also found that the decreased size of spherical PCL phase results in the improvement of Jin indicating that the size change of dispersed PCL phase due to LTI addition plays an important role in determining Jin value. [ABSTRACT FROM AUTHOR]

The article investigates on using lysine triisocyanate (LTI) as an additive for Poly (lactic acid) (PLA)/Poly (ε-caprolacton)(PCL) polymer blend to improve impact fracture properties. Impact fracture properties of PLA/PCL/LTI blend is evaluated and compared to those of PLA/PCL blend to assess the effectiveness of LTI addition. Effect of LTI addition on fracture micromechanism is also investigated by observing their fracture surfaces using a scanning electron microscope.