This research work aims to study the influence of the reprocessing cycles on the mechanical, thermal, and thermomechanical properties of polylactide (PLA). To this end, PLA was subjected to as many as six extrusion cycles and the resultant pellets were shaped into pieces by injection molding. Mechanical characterization revealed that the PLA pieces presented relatively similar properties up to the third reprocessing cycle, whereas further cycles induced an intense reduction in ductility and toughness. The effect of the reprocessing cycles was also studied by the changes in the melt fluidity, which showed a significant increase after four reprocessing cycles. An increase in the bio-polyester chain mobility was also attained with the number of the reprocessing cycles that subsequently favored an increase in crystallinity of PLA. A visual inspection indicated that PLA developed certain yellowing and the pieces also became less transparent with the increasing number of reprocessing cycles. Therefore, the obtained results showed that PLA suffers a slight degradation after one or two reprocessing cycles whereas performance impairment becomes more evident above the fourth reprocessing cycle. This finding suggests that the mechanical recycling of PLA for up to three cycles of extrusion and subsequent injection molding is technically feasible.

During the last decades, the increasing ecology in the reduction of environmental impact caused by traditional plastics is contributing to the growth of more sustainable plastics with the aim to reduce the consumption of non-renewable resources for their production

This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener and a reactive diluent derived from plants at 31 wt %. The highest performance was obtained for the resins cured at moderate-to-high temperatures, that is, 80 ${}^{°}\mathrm{C}$ and 90 ${}^{°}\mathrm{C}$ , which additionally showed a significant reduction in the gel time. This effect was ascribed to the formation of a stronger polymer network by an extended cross-linking process of the polymer chains during the resin manufacturing. Furthermore, post-curing at either 125 ${}^{°}\mathrm{C}$ or 150 ${}^{°}\mathrm{C}$ yielded thermosets with higher mechanical strength and, more interestingly, improved toughness, particularly for the samples previously cured at moderate temperatures. In particular, the partially bio-based epoxy resin cured at 80 ${}^{°}\mathrm{C}$ and post-cured at 150 ${}^{°}\mathrm{C}$ for 1 h and 30 min, respectively, showed the most balanced performance due to the formation of a more homogeneous cross-linked structure.

This study reports the effect of poly(butylene succinate-co-adipate) (PBSA) on the mechanical performance and shape memory behavior of poly(lactic acid) (PLA) specimens that were manufactured by injection molding and hot-press molding. The poor miscibility between PLA and PBSA was minimized by the addition of an epoxy styrene-acrylic oligomer (ESAO), which was commercially named Joncryl^®. It was incorporated during the extrusion process. Tensile, impact strength, and hardness tests were carried out following international standards. PLA/PBSA blends with improved mechanical properties were obtained, which highlighted the sample that was compatibilized with ESAO, leading to a remarkable enhancement in elongation at break, but showing poor shape memory behaviour. Field Emission Scanning Electron Microscopy (FESEM) images showed how the ductile properties were improved, while PBSA loading increased, thus leading to minimizing the brittleness of neat PLA. The differential scanning calorimetry (DSC) analysis revealed the low miscibility between these two polymers and the improving effect of PBSA in PLA crystallization. The bending test carried out on the sheets of PLA/PBSA blends showed the direct influence that the PBSA has on the reduction of the shape memory that is intrinsically offered by neat PLA.