Agüero Angel, Morcillo Maria Del Carmen, Quiles-Carrillo Luis, Balart Rafael, Boronat Teodomiro, Lascano Diego, Torres-Giner Sergio, Fenollar Octavio
Technological Institute of Materials (ITM), Universitat Politècnica de València (UPV), Plaza Ferrándiz y Carbonell 1, 03801 Alcoy, Spain.
Novel Materials and Nanotechnology Group, Institute of Agrochemistry and Food Technology (IATA), Spanish National Research Council (CSIC), Calle Catedrático Agustín Escardino Benlloch 7, 46980 Paterna, Spain.
Polymers (Basel). 2019 Nov 20;11(12):1908. doi: 10.3390/polym11121908.
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.
本研究旨在探讨再加工循环对聚乳酸（PLA）机械性能、热性能和热机械性能的影响。为此，对PLA进行了多达六次的挤出循环，并通过注塑成型将所得粒料制成片材。力学表征表明，在第三次再加工循环之前，PLA片材呈现出相对相似的性能，而进一步的循环则导致延展性和韧性急剧下降。还通过熔体流动性的变化研究了再加工循环的影响，结果表明，在四次再加工循环后，熔体流动性显著增加。随着再加工循环次数的增加，生物聚酯链的流动性也有所提高，这随后有利于PLA结晶度的增加。目视检查表明，随着再加工循环次数的增加，PLA出现了一定程度的泛黄，片材也变得不那么透明。因此，所得结果表明，PLA在一或两次再加工循环后会发生轻微降解，而在第四次再加工循环以上，性能损害变得更加明显。这一发现表明，PLA进行多达三次挤出循环及后续注塑成型的机械回收在技术上是可行的。
