Silicone-thermoplastic semi-interpenetrating silicones

Hybrid versions of silicone-thermoplastic semi-IPNs have been developed (19). A hybrid interpenetrating network is one in which the cross-linked network is formed by the reaction of two polymers with structurally distinct backbones. Hydride-functionalized siloxanes can be reacted with organic polymers with pendant unsaturated groups such as polybutadienes (5) in the presence of platinum catalysts. Compared with the polysiloxane semi-IPNs discussed earlier, the hydride IPNs tend to maintain mechanical and morphologically derived properties, whereas properties associated with siloxanes are diminished. The probable importance of this technology is in cost-effective ways to induce thermoset characteristics in thermoplastic elastomers. 

A commercial blend consisting of a thermoplastic polyamide (PA-6 or PA-66) and 5-25 wt% of a crosslinkable silicone, which forms a semi-interpenetrating network (semi-IPN) upon curing, has been offered under the trade name of Rim-... 

Commercial interpenetrating polymer networks (not including thermoplastic compositions) include artificial teeth (Dentsply) made Ifom crosslinked PMMA mixed with MMA monomer and polymerized (sequential IPN), sound and vibration damping compositions (e.g., vinyl-phenolic Hitachi) and sheet molding compositions (acryhc/urethane/polystyrene Ferro Chemical) [164]. Water-borne acrylic methane semi-IPNs are commercial Ifom several sources where acrylate monomers are polymerized in the presence of a polymethane water dispersion. A silicone/polytetrafluoroethylene composition described as an IPN is offered by Biomed Sciences under the Silon tradename. The fluoropolymer provides the mechanical strength and the silicone rubber offers the softness and oxygen and moisture permeability for applications in the wound care area. 

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