Chitosan-reinforced blended photopolymers for DLP: Mechanical enhancement and anisotropic shrinkage behavior

Digital Light Processing (DLP) offers high resolution and expedited production in additive manufacturing; nevertheless, the fragility and dimensional inaccuracy of photopolymer resins persist in posing significant constraints. This study investigates the impact of incorporating chitosan (0–10 wt%) into a blended photopolymer system composed of standard resin (epoxy-diacrylate based) and flexible resin (methacrylate-based). Mechanical characterization was conducted using tensile, flexural, impact and hardness testing, supplemented by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and assessment of dimensional shrinkage. The results of this study demonstrated uniform enhancements in tensile strength, flexural strength, and hardness as the content of chitosan increased. In contrast, impact energy specific exhibited a decline at low concentrations (2–4 wt%), followed by a recovery phase at 6–8 wt%, and a substantial surge at 10 wt%, reaching approximately two times the value of the pure blended resin. The SEM and FTIR investigations validated the interfacial interactions and dispersion processes aligned with these mechanical patterns. Dimensional assessment revealed contraction along the X and Y axes; however, an unforeseen expansion transpired in the Z-axis, which was attributed to overcuring. The findings indicate that the chitosan enhances mechanical characteristics and causes anisotropic dimensional responses in DLP printing. These insights offer essential direction for enhancing filler content and processing conditions to produce more robust and dependable photopolymer composites for additive manufacturing applications.