Effects of chemical and supermolecular structures on mechanical properties
of polyurethane/unsaturated polyester compositions
of interpenetrating polymer networks types
Polimery 2004, No 11-12, 790
The compositions being interpenetrating polymer networks of IPN type have been made of unsaturated polyester resin (UP resin, 4 grades), polyurethane (PUR) and styrene (ST). Mathematical model, describing an influence of chemical composition on selected mechanical properties of synthesized IPN systems, was elaborated. The following properties have been taken into consideration: stress at break - y1, unit elongation at break - y2, impact strength - y3, hardness - y4. The model was used to calculate the area of optimum composition in which the compromise in values of basic mechanical properties could be reached. Morphologies of the surfaces of IPN systems, differing in crosslinking density and chemical composition, were studied using SEM method. It was found that all of the samples of compositions from the area of optimum composition show heterogeneous structures. The matrix is built of UP resin while dispersed phase consists of the mixture of UP resin and PUR. The morphology observed is a result of two competing processes of phase separation and polymerization reaction going simultaneously at the stage of UP resin curing with ST. In order to confirm this idea the kinetics of gelation of IPN compositions was investigated and gelation time (tgel.) as well as maximum temperature of curing reaction (Tmaks) were determined. It was found that fast gelation of IPN systems led to formation of homogeneous matrix built of UP resin (compromised mechanical properties were observed) while slow gelation process favored the formation of heterogeneous matrix, built of UP resin and PUR.
Keywords: unsaturated polyester resin, polyurethanes, interpenetrating polymer networks, mechanical properties, composition optimization, mathematical model, morphology, gelation kinetics
Effects of chemical and supermolecular structures on mechanical properties of polyurethane/unsaturated polyester compositions of interpenetrating polymer networks types