Roles of Unsaturated Polyester in the Epoxy Matrix System

Abstract

ABSTRACT:A study of the interpenetrating polymer network (IPN) as a polymer blend matrix was carried out using different compositions of unsaturated polyester (UP) to epoxy (EP) resins. It was observed that 5 wt% UP in the blend provides maximum mechanical properties, particularly the impact strength for optimum casting. Fourier transform infrared (FT-IR) spectroscopy was used to investigate the intermolecular hydrogen bonding and functional group change. In this work, changes of physical property, e.g., viscosity and specific component of interfacial tension were evaluated before and after cure, respectively. Increase of the physical properties was observed in 5 wt% UP in the blend, probably due to the effects of hydrogen bonding, resulting in higher toughness properties of the casting specimens.KEY WORDS Interpenetrating Polymer Network I Epoxy I Unsaturated Polyester I Viscosity I Interfacial Tension I Mechanical Properties I Epoxy resins have been largely used in a matrix for fiber reinforced plastic (FRP) composites due to their excellent thermo-mechanical properties, thermal stability, chemical resistance, electrical properties and dimensional stability. 1 In real application, a study of the improvement of matrix resin properties is important in the development of high performance composites, together with studies of high strength/modulus fibers and fiber-matrix interface. 2 Although numerous chemical modifications on epoxy resins have been reported, the interpenetrating polymer networks (lPN s) by introducing some selective moieties may be economically considered as a physical interlocking system for desired properties. 3 · 4 IPNs are special blends defined as a mixture of two or more cross-linked polymer networks without any chemical combination between polymer chains. 5 During cure, network interlocking between two different polymers takes place and affects the physical properties of blends, such as viscosity 6 and interfacial tension. 7 In the present work, an lPN blend system of epoxy resin (EP) and unsaturated polyester resin (UP) was prepared as different compositions of UP in the blend. Then, we report the effects of network interlocking and intermolecular interaction on viscosity change and interfacial tension during lPN formulation. The final mechanical properties are discussed with different compositions of UP in the blends, particularly impact strength for the optimum casting. EXPERIMENTAL Materials and Sample PreparationEpoxy resin used in this experiment was diglycidylether ofbisphenol A (DGEBA, YD-114, supplied from Kukdo Chern. Co. of Korea). Epoxide equivalent weight of DG EBA was 190-210 g eq-1 and the density was 1.16 gem-3 at 25°C. Triethylene tetramine (TET A) was used as hardener for DGEBA. UP resin was orthophthalic acid type resin (R-235, supplied from Seiwon Chern. Co. of Korea). Methyl ethyl ketone peroxide t To whom all correspondence should be addressed. 28(MEKP) in the presence of cobalt-octoate as accelerator was used as the free radical initiator for polymerization of UP r...

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