Thermal Degradation and Thermomechanics of Castable Photopolymer Resins After Curing

The quality of castings using the technology of investment casting depends on the thermophysical and thermomechanical properties of photopolymer models. Determining the dependence of mechanical parameters on temperature will rationalize the process of burning out photopolymer models from casting molds. The current work considers six specialized castable photopolymer resins from different manufacturers: Harz Labs Dental Cast Cherry; Gorky Liquid Castable; Gorky Liquid Dental Castable; JAMG HE Ultra Cast UV Resin (90% WAX); JAMG HE Jewelry Casting Resin (25% WAX); Siraya Tech Cast Royal Blue. The additive growth parameters of the structures were selected to provide quality indicators of photopolymer models. Thermogravimetric analysis and dynamic mechanical analysis were chosen as the main methods of experimental analysis. Thermogravimetric analysis was performed at temperatures up to 700°C. Thermal decomposition of castable photopolymers has several stages of decomposition with different rates of destruction. Gorky Liquid Castable has the fastest thermal decomposition. The material has less than 1% of the residual weight at 530°C. The minimum ash content is in Siraya Tech Cast Royal Blue (less than 0.1%). Dynamic mechanical analysis was performed at temperatures up to 225°C for samples grown in different printing directions. The printing direction affects the storage modulus, the loss modulus, and the tangent of the angle of mechanical losses of photopolymer materials, on average by no more than 35%. Glass transition temperatures of materials and zones of relaxation transitions are established. The glass transition temperatures depend little on the direction of printing of the samples. JAMG HE Ultra Cast UV Resin (90% WAX), a photopolymer with a maximum wax content, has the minimum glass transition temperature of 30–32°C. JAMG HE Ultra Cast UV Resin (90% WAX) does not have a pronounced relaxation transition zone. The established temperature dependencies of destruction, the storage modulus, the loss modulus, and the tangent of the loss angle are necessary for the formation of a numerical model of materials and stages of the technological process of investment casting.