In this study, bio-composites were developed using polylactic acid (PLA) as the matrix and sisal fibers (SFs) derived from agave sisalana leaves as the reinforcement. The bio-composites were prepared through injection molding with the addition of tributyl 2-acetylcitrate (ATBC) plasticizer. The mechanical, thermal, and rheological properties of these bio-composites were investigated to understand the effects of fiber and plasticizer contents. The results showed that the addition of SFs improved the tensile and flexural moduli of the bio-composites but led to a decrease in tensile strength compared to neat PLA. The flexural strength initially decreased with low fiber content but recovered to the level of neat PLA as the fiber content increased. The impact strength increased with the incorporation of SFs and ATBC. However, the presence of ATBC had a negative impact on the tensile and flexural properties of the bio-composites. The thermal conductivity of the materials was influenced by the fiber content and processing temperature, increasing with SFs inclusion but decreasing with temperature. Differential scanning calorimetry analysis revealed increased crystallinity of PLA with the presence of SFs and ATBC. The specific heat capacity increased with ATBC but decreased with increasing SFs. Dynamic mechanical property testing showed variations in storage and loss moduli of the bio-composites at different temperatures. The storage modulus increased with higher fiber content and abruptly dropped around glass transition temperature. Rheological characterization demonstrated effective interactions between the fibers and matrix with good fiber dispersion, resulting in uniform shear viscosity versus shear rate for different capillary dimensions. The shear viscosity of the SFs/PLA mixture increased with increasing fiber content but decreased with the addition of plasticizer. Furthermore, the compounding and molding processes had a notable impact on the microstructure of the fibers, specifically resulting in fiber breakage and fiber separation during processing.

Biocomposites are promising candidates for some engineering applications owing to the growing environmental and economic challenges to replace petrochemical-based polymers with biodegradable polymers. Herein, sisal fiber reinforced polylactic acid (PLA) composite specimens were fabricated using an injection molding machine with and without plasticizer. The weight percentage (wt%) of the sisal fiber varied between 5% and 20%. The effect of the sisal fiber wt% on water absorption resistance and mechanical properties was investigated experimentally using water ageing, mechanical, and morphological studies. The results revealed that tensile and flexural specimens after water ageing exhibited lower tensile and flexural strengths with higher water absorption behavior at 20 wt% sisal fiber than 5 wt% sisal fiber, while the impact strength increased after water ageing. In addition, the sisal fiber/PLA composites exhibited higher water absorption behavior and lower strength and modulus at 20 wt% sisal fiber after water ageing. Moreover, the water absorption decreased with the incorporation of the plasticizer.

Gaining an understanding of how chemical treatment affects the mechanical properties of natural fiber reinforced polymer composites is essential to enhance their performance and broaden their applicability across various engineering domains. The objective of this study was to develop bio-composites by combining polylactic acid with sisal fibers that have undergone chemical treatments and evaluating the mechanical properties at different temperatures to determine their suitability for high-temperature applications. For this purpose, sisal fibers were chemically treated using alkali, acetylation, and alkali/acetylation solution before composite processing. The results revealed that tensile strength slightly improved by alkali treatment, while both alkali/acetylation and acetylation treatments decreased the tensile strength and tensile modulus. Alkali treatment significantly enhanced flexural strength, while the effect of acetylation and alkali/acetylation treatments on flexural strength was less pronounced. All chemical treatments led to a slight increase in flexural strain at failure, but resulted in a decrease in tensile strain at failure and tensile modulus. Alkali treatment slightly increased flexural modulus, while acetylation and alkali/acetylation treatments significantly reduced it. The impact strength of the bio-composites was increased by alkali and acetylation treatments, but significantly reduced by alkali/acetylation treatment. Furthermore, the flexural strength of all bio-composites decreased as temperature increased, especially in plasticized bio-composites using tributyl 2-acetylcitrate plasticizer. The flexural strain at failure decreased with the addition of tributyl 2-acetylcitrate at room temperature. In plasticized bio-composites, the flexural strain at failure increased at 35°C, but decreased at 45°C. On the other hand, the flexural strain at failure of non-plasticized bio-composites remained constant up to 35°C, slightly increased up to 45°C, and then significantly increased at temperatures above 45°C. These bio-composites could be suitable for packaging industry as biodegradability is the criteria for such applications.