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Mechanical properties and soil and marine degradation behavior of environmentally friendly polylactic acid/nanochitin composite films
Summary
Scientists mixed a plant-based plastic (PLA) with chitin — a natural fiber found in shrimp and crab shells — to create a stronger, more heat-resistant packaging material that also breaks down faster in soil and ocean water than regular biodegradable plastic. This matters because it could help reduce microplastic pollution, which has been linked to health concerns as tiny plastic particles increasingly turn up in our food, water, and even our bodies. The upgraded material could offer a sturdier alternative to conventional plastics while leaving less lasting waste behind.
Growing concern over microplastic pollution has increased demand for biodegradable polymer composites with high mechanical and thermal performance. In this study, polylactic acid (PLA)/nanochitin (NCh) composite films were prepared using an aqueous dispersion of PLA nanoparticles, enabling homogeneous mixing with NCh and fabrication of phase-separation-free films via a simple drying process. Tensile testing revealed that both the elastic modulus and tensile strength increased with increasing NCh content, reaching approximately 23-fold and 12-fold, respectively, at a loading of 50%. Microscopic observations revealed that NCh was preferentially distributed at PLA particle interfaces, forming an NCh-derived layered structure at high loadings. The addition of NCh increased the glass transition temperature by 9.2 °C and reduced the coefficient of linear thermal expansion to 4 ppm K⁻¹. In biodegradation tests conducted in soil and seawater, the PLA/NCh composite films degraded faster than neat PLA. This behavior is attributed to the preferential degradation of NCh, which promotes pore formation and, at least in the case of relatively low-molecular-weight PLA, accelerates both hydrolytic and microbial degradation.