Adhesives Based on Interpenetrating Polymer Networks

An interpenetrating network (IPN) can be defined as a mixture of two crosslinked polymers when at least one of them is synthesized and (or) crosslinked with another [114], The components that make up an IPN are thermodynamically incompatible and a transition region of two phases is formed in such a system. The whole complex of IPN properties is determined by the av dlability and features of this region. 

Let us consider the properties of an adhesive based on the following mixture of oligomers an unsaturated polyester resin and a prepolymer with end isocyanate groups (or macrodiisocyanate) based on polydiethylene glycol adipate of molecular weight 800 and on TDI (a mixture of the 2,4- and 2,6-isomers in ratio of 65 35), with the 

The Sprut-5M adhesive consists of unsaturated polyester resin 100 parts by weight, ATG-M 80 parts (a mixture of 50 parts of macrodiisocyanate and 30 parts of ATG), polymerization initiator (MEKP(O)) 2 parts. Usually 1 wt% of CN is integrated additionally into the adhesive base. Sprut-5M can be produced using various polyester resins, but the most apphcable one is the adhesive based on PM-I resin owing to its availability and low cost. For this reason we will consider the properties of the adhesive based mainly on this resin although it has adhesion strength 20-40% lower than that of adhesives based on PN-11, NPS 609-21M, and other resins, especially when cementing in water. 

MP PDEG in the composition of the polyester resin has end hydroxyl and carbojgrl groups capable of interacting with the isocyanate groups. To prevent the chemical interaction of the individual IPN networks, the MP PDEG end groups were pre-blocked with a monofunctional isocyanate (phenyl isocyanate) later this reaction was excluded with almost no effect upon the adhesive properties. 

It has been reported that under the influence of radical polymerization initiators styrene can copolymerize with TDI with the formation of the substitute poly lmide, identified by the IR absorption band of the carbonate group at 1730 cm. In the system under consideration no formation of the substituted polyamide is observed. Thus, the polyester and polyurethane components essentially do not react one with another in the course of the adhesive cure. 

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