Solvent impregnated resins stability

There are two basic VPI resin formulations. One is based on epoxy resins, and the other is based on unsaturated polyesters. Both are typically one-part solventless compositions that are completely polymerizable. Volatile, nonpolymerizable solvents cannot be tolerated because these will lead to bubbling in the vacuum impregnation procedure. To control viscosity of the resin formulations, the epoxies contain low-viscosity, reactive diluents of the monoglycidyl ether type the unsaturated polyester formulations contain styrene or vinyltoluene as reactive diluents. Both resin types contain catalysts that become active only at elevated temperatures to insure long-term stability at room temperature. The epoxy resins are frequently catalyzed with metal organic compounds such as titanium complexes, and peroxides are usually the main catalyst in the unsaturated polyester formulations. In addition to the ingredients mentioned here, the compositions may contain additives such as cocatalysts, activators, and accelerators. However, there are no particular fillers used in VPI resins. 

Drying sealants are represented by solutions of rubber blends in organic solvents. As soon as the solution is impregnated into the clearance and the solvent evaporates, the sealant becomes rubbery and gains elasticity. The original compositions contain adhesive additives (coumarone, terpenic and phenolic resins, rosin or its esters), PI and solvents (toluene, xylol, benzine, etc.), fillers (chalk, titanium dioxide, talc, etc.) and stabilizers. These compositions can be easily impregnated with Cl [15]. 

Allylic resins Long pot life, low vapor pressure monomers, high cure temperature, low viscosity for monomers Excellent clarity, abrasion resistant,-color stability, resistant to solvents and acids Safety lenses, face shields, casting impregnation, as monomer in polyester... 

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