Silicone and Silicone-Like Elastomers in Vat Photopolymerisation: Polysiloxane Chemistry, Silicone-Free Functional Analogues, Thermal-Service Limits and Qualification

True silicone elastomers derive their material identity from crosslinked polysiloxane chains, most commonly poly(dimethylsiloxane), rather than from softness, Shore hardness or tactile feel alone. Vat photopolymerisation imposes low-viscosity, optical and rapid-gelation requirements that can conflict with the long flexible chains and reinforcing strategies used in conventional silicone rubber. Primary studies demonstrate several routes through this conflict, including thiol-ene crosslinking of vinyl- and thiol-functional polysiloxanes, simultaneous chain extension and crosslinking, sequential photo and thermal cure, and orthogonal silicone double networks. These routes prove that genuine silicone structures can be printed, but their reported properties remain formulation- and process-specific. Silicone-like photopolymers form a separate category: non-silicone networks may reproduce selected room-temperature functions such as softness, elastic deformation, shape recovery, tactile response or cushioning, yet functional overlap does not establish chemical identity or equivalence in heat resistance, compression set, tear propagation, permeability, fluid exposure, ageing or biological response. A defensible comparison must therefore proceed by declared function, controlled state and matched tests rather than by label. The proposed qualification stack combines chemistry verification, print-state control, tensile and tear response, time-dependent compression, cyclic durability, thermal ageing, fluid exposure and geometry-representative testing. Manufacturer statements are segregated from independent science. No proprietary formulation, product ranking, direct replacement claim or intended-use approval is provided.

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