Development of bio-composite material from polylactic acid blended with thermoplastic from sago starch and reinforced with pineapple leaf fiber

Abstract

This study analyzes the effects of pineapple leaf fiber (PALF) content on the physical, mechanical, and thermal properties of PLA/TPS and PLA/TPSW composites and material cost. Thermoplastic starch (TPS) is derived from sago starch with glycerol as a plasticizer, while TPSW incorporates water with glycerol. The proportions of TPS and TPSW were set at 0%, 5%, 10%, 15%, and 20% by weight, combined with PLA and PALF at 0%, 2%, 4%, 6%, 8%, and 10% by weight. Results show that PLA/TPS exhibits higher melt flow index and density, indicating better flowability and suitable density. Additionally, PLA/TPS has slightly higher water absorption due to the cross-linked structure of TPSW, while retrogradation reduces water absorption due to increased rigidity and brittleness. The mechanical properties of PLA/TPS are higher with increased PALF content. This significantly enhances resistance to bending and impact due to improved stress distribution, while PLA/TPSW shows minor improvements because of uneven fiber distribution and recrystallization. Increased PALF content reduces tensile strength in both composites. This reduction is more pronounced in PLA/TPSW, as SEM analysis indicates poor adhesion and fiber distribution leading to fiber pull-out. In thermal properties, adding 10% PALF to PLA/TPSW enhances crystallization temperature (Tc) and crystallinity percentage, with lesser effects observed in PLA/TPS. Finally, PLA/TPS demonstrates better physical and mechanical properties, especially with 10% PALF and exhibits the lowest material costs, PLA/TPS composite at PALF (10%) can be molded via injection machine into cups, making it suitable for commercial development with a maximum service temperature not exceeding 50 degrees Celsius.