What describes liquid resin material that uses light as a catalyst for polymerization?

The correct answer is photopolymer, as this term specifically refers to a type of resin that undergoes a chemical change when exposed to light, typically ultraviolet (UV) light. Photopolymers are essential in various applications, particularly in 3D printing and other additive manufacturing processes where layered materials are solidified using focused light.

Photopolymers are unique because they can transition from a liquid to a solid state when subjected to certain wavelengths of light, which triggers the polymerization process. This makes them highly effective for applications that require precision and the ability to create complex shapes.

This distinct characteristic of photopolymers sets them apart from the other options presented. For instance, thermosetting materials also harden upon heating but do not involve light for their curing process. Thermoplastics, on the other hand, can be molded and remolded upon heating but do not polymerize through light exposure. Lastly, elastomers are flexible polymers that can stretch and return to their original shape but do not typically involve light as a catalyst for their polymerization. Thus, photopolymer is the most accurate descriptor of the material in question.