Tunable enhancement of polyester biocomposites via extrusion with fungi-derived chitin

Abstract

Chitin is a polysaccharide that serves as a useful filler component to blend with conventional plastics and afford melt-compounded biocomposites with tunable properties. However, chitin is typically isolated under harsh conditions from crustacean exoskeletons, limiting large-scale production and jeopardizing its environmental sustainability. Agricultural sources, such as fungi, offer a more sustainable and reliable feedstock for the upscaled production of chitin. Yet, the use of chitin obtained from these feedstocks remains underexplored as a filler component in melt-compounding applications. Herein, we describe the first use of fungi-derived chitin nanofibrils, which are harvested from commercially cultivated mushrooms, as a melt-compounding additive for polyester-based biocomposites synthesized using twin-screw extrusion. A Design of Experiments approach surveyed extrusion parameters such as screw speed, mixing time, and filler loading to develop structure-processing-property relationships. The fungi-derived chitin nanofibril biocomposites generally feature enhanced stiffness compared to benchmark materials which incorporate commercially sourced shrimp shell-derived chitin. Interestingly, the fungi-based materials also display enhanced alkaline degradability as compared to the benchmark biocomposites, opening the door towards the design of mechanically functional yet easily degradable materials that could be useful in sustainable packaging applications. This study shows that fungi, which are widely cultivated under controlled conditions, yield a viable source of chitin that can be used as a competitive filler in polyester biocomposites.