2022 Annual Meeting

Optimization of Hybrid Silicone Elastomers

Polydimethylsiloxane (PDMS), a cross-linkable silicone polymer, is widely used in elastomers for its high temperature stability, chemical resistance, insulating properties, and optical transparency. However, PDMS by itself has poor mechanical properties because of its low stiffness and toughness. Interpenetrating polymer networks (IPNs) can offer a solution to this by incorporating a glassy polymer into the siloxane network to form a tougher hybrid elastomer. Several authors have investigated the synthesis of hybrid polymer elastomers with PDMS through IPN synthetic methods and their resulting properties, but these efforts have seldom focused on understanding the impact and interaction of input variables on network physical properties. In addition, fracture properties have not been studied as extensively as thermomechanical properties.

In this study, we formed simultaneous silicone-organic graft IPNs by photocuring a methacrylate-terminated PDMS prepolymer with a series of methacrylate monomers. We took a design of experiments (DOE) approach to form a response surface model of the effects and interactions of various inputs on the mechanical and optical properties of the resulting hybrid elastomers. Analysis of the data indicated significant input effects on the mechanical properties from the type and amount of monomer added, degree of polymerization (DP) of the PDMS, and UV intensity, while the transparency of the material was most impacted by composition and PDMS DP. Conditions for optimizing fracture energy and transparency were selected based on these findings.