Effects of the Chitosan Source on the Properties of 3D Printed Polymer Composites

Chitosan, or deacetylated chitin, is a linear polysaccharide composed of glucosamine and N-acetyl glucosamine units. Chitin is found in the cell walls of crustaceans, fungi, and insects, making chitosan the second most abundant natural polymer on earth. The broad availability of chitosan makes it an attractive material for applications in textile, medical, and agricultural industries as well as for use in environmental waste remediation. Additive manufacturing, or 3D printing, is a technique that can be used to produce polymeric materials on demand based on custom digital designs. Using a digital light projection 3D printer, we incorporated chitosan from different sources into photoresins, considering different sources for their sustainability. We explored how the source of the chitosan (fungal vs crustacean) can affect the mechanical properties, resin incorporation, and printability of the photoresin. The 3D-printed materials were tested to compare the mechanical properties of the polymers with those of chitosan from different sources. The mushroom chitosan with the highest molecular weight (MC600) had the greatest improvement in resin strength, toughness, and ultimate tensile strength. We observing an increase in strength up to 1.8-fold and stiffening up to 167% greater than the control. The crustacean chitosans improved the strength of the printed polymers, with an average improvement of 1.7-fold. Crustacean-sourced chitosans produced increased stiffness and reduced strain capacity. In contrast, the mushroom chitosans MC400 and MC600, have increased strain capacity with increasing loading. The oligomer MCO plasticized the resin formulation, resulting in greater strain at the break and the capability to revert to its original shape after straining. Overall, we show that chitosan with a higher loading and higher molecular weights improved the mechanical properties. However, the source of chitosan affected the incorporation and printability of the composites.