Structure-property relationships in minimally processed insect chitin/carboxymethyl cellulose films

Polymers from renewable resources, e.g., polysaccharides, can decarbonize the materials sector and transform the dominant linear carbon-intensive economies into sustainable biobased models. Chitin - conventionally isolated from crustaceans - enables multiple advances in carbohydrate science. Here, we studied insect exuviae as an emerging source of chitin, and explored how different top-down isolation processes affected its structure and physicochemical properties. NaOH-treatment predominantly removed proteins, allowing control over the chitin-to-protein ratio. The chitin was used to reinforce a model biobased polymer, carboxymethyl cellulose (CMC). Free-standing films containing 1, 2 and 5 wt% chitin were fabricated by aqueous dispersion and doctor-blade casting. The mechanical reinforcing effect was greater for minimally processed insect chitin, where 1 wt% minimally-processed chitin, a protein rich material (14-20 wt%), increased the Young's modulus by 26 %, from 1750 ± 220 MPa for the neat CMC to 2210 ± 190 MPa for the composite. Conversely, higher purity chitin obtained from 1 M NaOH (1-5 wt% protein) increased the elastic modulus by 11 %. Chitin also improved surface hydrophobicity and film opacity, evaluated across chitin concentration in CMC films and treatment severity, totaling nine samples. This research underscores the promise of insect-derived chitin and minimal biomass processing for sustainable yet competitive polymeric materials from renewable carbon.