The influence of treated eucalyptus microfibers on the properties of PLA biocomposites

Abstract

Eucalyptus sawdust was used for nano and microfibers preparation by a “green” process (ball milling), followed by surface treatments (alkaline and surfactant) and incorporated in PLA, from 1 to 10 wt %, aiming for the preparation of films of biocomposites. The treatments applied exposed the polar groups due to lignin removal or by the surfactant adsorption, respectively. The modification intensified the interaction in the interface region between the fibers and the PLA matrix (SEM), maintaining thermal properties (DSC results). The fibers treatments contributed to the films hydrophobicity concerning the humid environments, as evidenced by the results of moisture absorption and contact angle. However, the decrease in the crystallinity index of the biocomposites (4.2%, obtained by DSC) contributed to the increase of the water molecules diffusion (D, water absorption) caused by the structure disorder, which may favor the post-use biodegradation process. The mechanical properties of the films were promising, presenting values always above the PLA property. In general, the results suggest that the incorporation of eucalyptus fibers, mainly detergent treated, improves not only the mechanical properties of PLA but also favors properties that enhance the biodegradation process of the post-use biocomposites.