Annealing efficacy on PLA. Insights on mechanical, thermomechanical and crystallinity characters

Abstract

Poly (lactic acid) (PLA) is widely used biodegradable thermoplastic in the additive manufacturing, mainly on manufactured products through 3D printing. However, PLA is highly fragile and presents low impact strength; hence improvements on this way are industrially and technologically important. Aiming to develop proper methodology for higher PLA performance, this work investigated the effects of thermal annealing on the mechanical properties (impact, tensile, Shore D hardness), heat deflection temperature (HDT), Vicat softening temperature (VST) and crystallinity (X-ray diffraction) of PLA. Injected specimens were annealed in greenhouses at 70, 80, 90 and 100 °C. Annealing at 70 °C was not effective, without verified significant changes. On the other hand, annealing at 80, 90 and 100 °C provided crystalline peaks in DRX, indicating development of structural organization. Expressive results were achieved, at 90 °C, for impact strength, HDT, VST, Shore D hardness and tensile strength, related to non-annealed PLA. Provided results in this work have scientific and technological importance, since the mechanical and thermomechanical properties of PLA were improved using a simple methodology which may render higher performance products mainly for the 3D printing industry of PLA.