The effect of sisal fiber surface treatments, plasticizer addition and annealing process on the crystallization and the thermo-mechanical properties of poly(lactic acid) composites

The aim of this work was to study the effect of annealing process on the thermo-mechanical properties of non-plasticized and plasticized composites as well as study the effect of treated sisal fibers addition on the crystallization process of poly(lactic acid) (PLA) and PLA/vegetable oils systems. After annealing process, the crystallinity degree and the thermo-mechanical behavior of the composites were improved. However, tensile strength and modulus values of non-plasticized composites decreased considerably because the annealing process damaged the adhesion between the fiber and the PLA matrix. Regarding plasticized composites, systems plasticized with epoxidized oils showed better tensile properties than systems plasticized with non-epoxidized oils. It should be highlighted that annealed PLA/ELO/sisal fiber system showed an increase of 80% on tensile modulus value respect to non-annealed neat PLA with similar strength and elongation at break values. On the other hand, not significant differences were observed on the crystallization process of PLA and plasticized PLA systems when different sisal fiber treatments were used.