Three‐component IPN systems made from polyurethanes, epoxies, and poly(methacrylates) containing charge groups in the backbones of the constituent networks have been prepared. Specific attractive forces that occurred among the various networks helped to compatibilize them and aided in the formation of true homogeneous topologically interpenetrating polymer networks. These three‐component polymer alloys, including full‐IPN's, pseudo‐IPN's, and graft‐IPN's, were characterized by means of mechanical spectroscopy, electron microscopy, and stress–strain properties. In addition, some adhesion studies were carried out (lap shear strength and peel strength). A comparison of the different types of three‐component polymer alloys showed that better properties were generally exhibited by the graft‐IPN's and full‐IPN's containing opposite charge groups.
Recent investigations on interpenetrating polymer networks (IPNs) have included two component IPNs from polyurethanes and poly(methacrylates) and two component IPNs from polyurethanes and epoxies. All the IPNs were prepared by the simultaneous polymerization technique (SIN‐IPNs). Two types of IPNs, polyurethane‐poly(methyl methacrylate) (PU/PMMA) and polyurethane‐poly(methyl methacrylate‐methacrylic acid) (PU/PMMA‐MAA) were prepared. Improved phase miscibility and decreasing extent of phase separation was observed in both types of IPNs with increasing the NCO/OH ratio, decreasing molecular weight of the polyol in the PU and introduction of charge groups. A comparison was made between full‐IPNs, pseudo‐IPNs, graft copolymers and related homopolymers from polyurethanes and epoxies. Increased compatibility in full‐IPNs and graft copolymers was observed by means of DSC, SEM and was also further substantiated by a shift toward single Tgs as determined by dynamic mechanical spectroscopy. The introduction of opposite charge groups in two‐component IPNs from polyurethanes and epoxies led to improved compatibility (no phase separation) and enhanced mechanical properties.
In this article we review the synthesis and morphology and the physical and mechanical properties of two‐component interpenetrating polymer networks (IPNs) from polyurethane and epoxy polymers; the corresponding pseudo‐IPNs and grafted IPNs are also discussed. A comparison was made of full IPNs, pseudo‐IPNs, grafted IPNs, and related homopolymers by examining their mechanical properties, mechanical spectra, and electron microscopy on an investigation of the effects of interpenetration or permanent entanglement in the IPN and related systems. This interpenetration has resulted in improved compatibility between the two polymer systems and has caused a decrease in the degree of phase separation. An observed shift in the dynamic glass transition temperatures (Tgs) of the two components which yielded a single IPN Tg further substantiates our results.
Two‐component interpenetrating polymer networks (IPNs) that contained charge groups in the backbones of the polyurethane and epoxy networks were studied. IPNs that contained opposite charge groups, similar charge groups, no charge groups, and corresponding pseudo‐IPNs were prepared. A comparison of mechanical properties, water‐resistance data, mechanical spectra, and electron microscopy showed that improved properties and morphologies resulted in IPNs that contained opposite charge groups. Presumably, interactions between the opposite charge groups in the constituent networks resulted in a forced compatibility between the two polymers which decreased the degree of phase separation.
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