Water absorption behavior and physico-chemical and mechanical performance of PLA-based biopolymers filled with degradable glass fibers

Poly(lactic acid) (PLA)-based biopolymers filled with degradable glass fibers were submitted to real life conditions, selected based on their potential applications as beverage containers, to evaluate the feasibility of their usage at the required operational conditions. To do so, several media (i.e., buffer solutions at pH = 3, 5, 7.5, 12 and alcoholic solution) and temperatures (25, 37, 55 and 70 degrees C) were applied to mimic the storage of food, beverage, and detergents inside or in direct contact with the bio-based prototypes. Their mechanical, spectroscopic (FTIR) and morphological (SEM) features were evaluated and compared with samples after immersion. Water absorption increased with the increasing temperature, with maximum values achieved in alcoholic solutions indicating a more severe interaction of media with the functional groups of the samples. The diffusivity, D, increased with temperature, indicating faster water diffusion rate, especially in strong alkaline media. Treatments at pH 12 led to the most relevant degradation. This behavior was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis that evidenced a strong decrease of the ester band at 1755 cm (-1) and the dissolution of the external layer of the polymeric matrix, which became more evident at higher temperatures, where several glass fibers emerged from the bulk. Tensile and flexural tests indicated a softening of the material and an increase in the plasticity of the samples with the increasing temperature. Evident embrittlement of samples was observed at higher temperatures, suggesting an increase in the crystallinity degree of the biopolymer. The obtained results showed the suitability of the PLA-based biocomposites for applications that do not require high temperatures for long periods of time. Also, the tested materials were proved to resist washing with mild detergents. These results will help in the designing of the new improved PLA-based biocomposites to meet with the target objectives on their applications.