Chemical and Mechanical Evolution of a Volumetric Additive Manufacturing (VAM) Resin Under High-Temperature Storage.

Volumetric additive manufacturing (VAM) is a rapid, layerless photopolymerization process that fabricates three-dimensional (3D) objects by accumulating a projected light dose within a rotating resin vial. Since VAM relies on a polymerization threshold, small changes in resin chemistry, optical attenuation, or inhibition behavior may affect print fidelity and mechanical performance. However, the influence of resin storage history on VAM process stability remains insufficiently understood. This study investigates the chemical, optical, rheological, dimensional, and mechanical evolution of a representative acrylate-based VAM resin subjected to accelerated thermal aging. Resin samples were stored at 50 °C for 6, 12, and 48 days and compared with a non-aged resin. The aged resins were characterized, and the mechanical performance of printed and cast specimens was tested. The results indicate that storage did not cause any observable changes in molecular weight, and viscosity variations remained limited. However, aging produced measurable changes in optical, dimensional, and mechanical properties. The printed cylinder diameter increased from 12.9 mm for the non-aged resin to 14.4 mm after 48 days of aging. The tensile strength of printed samples peaked after 12 days of aging, and the compressive modulus increased with prolonged aging. Resin aging should be treated as an explicit manufacturing input, and routine resin monitoring and exposure recalibration are recommended to improve VAM reproducibility.