Investigation of polymer blend formulation and homogenization dynamics in the development of biodegradable, hydrophobic, and heat-resistant seaweed-based bioplastic straws

Abstract

The demand for biodegradable straws has grown in response to environmental concerns regarding plastic waste. This study aimed to develop and optimize seaweed-based bioplastic straws with enhanced hydrophobicity, mechanical integrity, and biodegradability. Four base formulations combining agar, starch, carrageenan, and konjac were evaluated, with the B9 formulation (comprising agar and starch) selected as the most promising due to its superior thermal stability and low water absorption. This formulation was then used in a process optimization stage, where various homogenization parameters (speed, temperature, and time) were tested. The best-performing straw from this stage, referred to as low-speed-S-B9 (B9 processed under low-speed homogenization), demonstrated the most favorable overall performance, achieving a contact angle of 115.31 ± 1.15°, water absorption below 100.27 ± 2.67%, and tensile strength of 60.76 ± 2.78 MPa. SEM analysis revealed a dense and cohesive matrix structure, while FTIR spectra showed the main polysaccharide functional groups in all samples, with additional peaks reflecting each formulation's chemical composition. Thermal degradation profiles confirmed its heat resistance, with delayed onset and higher char residue. Mechanical and flexural tests showed the low-speed straw maintained high elongation and comparable bending resistance to commercial paper straws. Finally, soil burial testing confirmed full biodegradation of the straw within 60 days. These results confirm that low-speed homogenization of seaweed-based formulations offers a scalable and sustainable strategy to produce biodegradable straws with functional properties suitable for real-world use.