Physicochemical Characterization and Evaluation of Pecan Nutshell as Biofiller in a Matrix of Poly(lactic acid)

The finding of biofillers for the development of biodegradable composite materials (biocomposites) is constantly growing in academic and industrial interest since it promotes sustainability. In this work, biocomposites of polylactic acid (PLA) and pecan nutshell (PNS) at two different concentrations (5 and 7.5 wt%) were prepared in order to study their mechanical, thermal, and morphological properties. Biocomposites were prepared with non-treated and treated PNS and the overall mechanical and thermal properties compared and discussed. The treatment consisted in the extraction by chloroform of fatty acids (lipids, oils, and waxes) present in the PNS. The extraction process adds novel information of the chemical characterization of the PNS. The structural characterization performed by FTIR analyses showed the absence of carbonyl and methyl group signals in treated PNS as compared with untreated PNS, which corroborated the extraction of fatty acids from the PNS. The results obtained have shown that the mechanical properties such as tensile and flexural modulus as well as the impact strength in the biocomposites increased in comparison to the neat PLA, especially when treated PNS was used. Moreover, the dynamic mechanical analysis confirmed that the stiffness in the biocomposites is increased with the use of PNS. The overall results were positively correlated with the rheology tests and melt flow properties. However, thermal stability decreases as the PNS increases in both cases. While the SEM micrographs show gaps and poor adhesion of the two different phases in non-treated PNS, the adhesion with the matrix was improved by using treated PNS, as it was corroborated by the mechanical evaluation. PLA biocomposites loaded by PNS untreated and treated have been investigated; the results suggest that PLA–PNS biocomposites may be used in rigid packaging and other applications.