Poly(l‐lactic acid) nanocomposites based on silver nanoparticles (PLA/AgNP) were prepared by melt blending using a twin screw extruder. Nanocomposites at low concentrations were prepared with 0.1, 0.2, and 0.3 wt% of AgNP to enhance the crystallinity and improve the thermal and mechanical properties of PLA. AgNPs smaller than 100 nm which increased the crystallinity of PLA upon the addition were detected by UV–Vis. Crystallinty index of nanocomposites was estimated reaching a maximum of 0.52, where the AgNPs acted as heterogeneous nucleating agent which is correlated with the Ag content. The α and α′ crystals were observed by temperature modulated differential scanning calorimetry and wide angle X‐ray diffraction, thus lattice spacing of more ordered and distorted crystals were corroborated obtaining a higher fraction of α structures when a high content of nanoparticles was added. Moreover, strain at break and toughness of pure PLA were increased from 4.3% to 16.9% and 2.1 to 7.3 MJ/m3, respectively, modifying the inherent brittleness of PLA. Finally, with the obtained results a correlation was established where more disordered crystals show less resistance to deformation that lead to an enhancement of elongation at break observed in the nanocomposites. POLYM. COMPOS., 39:2368–2376, 2018. © 2016 Society of Plastics Engineers

Binary and ternary composites of poly(lactic acid) (PLA), poly(ether‐block‐amide) (PEBAX) and copper nanoparticles were prepared by melt blending in an internal mixer. Compatibility and molecular interactions between the three components of the nanocomposites were evaluated using scanning electron microscopy and Fourier transform infrared spectroscopy. It was found that the carbonyl groups of the PLA and copper nanoparticles interact. Also, PLA and PEBAX are compatible and develop molecular interactions between the C=O of PLA and the C=O and NH of PEBAX, forming dipole–dipole bonds and hydrogen bonds. The compatibility and molecular interaction between PLA and PEBAX are reduced by copper nanoparticles. The reduction of compatibility between PLA and PEBAX produced a lower storage modulus and lower strain at break in the ternary systems than in the blend PLA‐PEBAX. Copper nanoparticles enhanced the crystallinity of PLA. PLA responded more strongly to the nucleating effect of copper when PEBAX was added indicating a synergistic effect. The strain at break of PLA was enhanced by the addition of PEBAX but was severely reduced by the presence of nanoparticles. © 2020 Society of Chemical Industry