Comparing with 'real' art materials such as woods, stones, and metals, the current evaluationtoward synthetic resins such as epoxy resin is unbelievably low; Many artists believe blindlysynthetic resins are just 'cheap' substitutes for 'real' materials and don't even try to know theirreal characteristics... Especially, epoxy resin has been left in the miserable situation... onlyfew know how to use it. ... This is definitely unfair.This paper is an attempt to shed light on the awful underestimation toward synthetic resins through four practical studies, taking epoxy resin as an example.Through this research, it isclearly showed that synthetic resins possess high potentiality as art materials and further rich possibility to open new horizon of Art making. (Received: May 25,2000)

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Silica-polyacrilicacid (PAA)-epoxy IPN and Silica-epoxy IPN were prepared using the phase separation during the sol-gel transition of alkoxysilane-PAA system. The silica-PAA IPN or silica skeleton prepared by heat treating the silica-PAA IPN at 600℃ or 800℃were soaked with epoxy resin to prepare silica-PAA-epoxy IPN or silica-epoxy IPN. Thermodynamic properties of these IPNs have been investigated. The storage modulus (E') of these IPNs prepared with two different types of epoxy resin remained high even at the temperature range over the glass transition.In addition, silica-PAA-epoxy IPN showed high loss modulus (E") at about 300℃. The high E" value suggests that the silica network protects the polymer at high temperature. The thermogrvimetric measurements have confirmed the protection effect of silica network againstthe thermal decomposition.

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Chemical curing-shrinkage and thermal mismatch generated the residual stresses on bonded structures during curing process and heat cycle process. Evaluating of residual stress is necessary to make sure of the reliability of equipments. But the behavior of residual stress in bonded structures is not cleared. In this study, the residual stress of epoxy adhesives was measured by the bimetal specimen during curing process and heat cycle process. In this experiment, room temperature (20C) curing and 50C after curing were given. Moreover, heating and cooling cycles were given. Relationship between the residual stress and temperature was obtained. As a result, following conclusions were obtained; [1] Chemical curing-shrinkage increases the residual stress during room temperature curing. [2] Retained chemical curing-shrinkage increase the residual stress during heating process of after curing, [3] In case of after curing, the residual stress during heating process is not equal to that during cooling process, because a coefficient of thermal expansion of resin during heating process is larger than that during cooling process. [4] Maximum residual stress generate after cooling process of after curing.

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The relationships between morphology and physical properties of cured epoxy resins blended with thermoplastic polyurethane elastomers (TPUs) were investigated. TPUs with hard segment/epoxy resin blends were prepared by a in-situ polymerization method in the epoxy resin. Adhesion properties of Fe/Fe joint using TPU/epoxy resin blends, bending properties and fracture toughness of cured ones were improved as compared with unblended epoxy resin and they were affected by the amount of TPUs and moreculer weights of macro-glycols. The results of dynamic viscoelastic properties, thermal analysis and scanning electron microscopy photographs of fracture surfaces of cured TPU/epoxy resin blends showed that the morphologies of the cured blends were varied by the amount of TPUs, moreculer weights of macro-glycols and the presence of hard seguments in TPUs.

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Synthesis and properties of novel siloxane-modified epoxy resins (ESDGs) were studied. These epoxy resins were synthesized by the reaction of bisphenol-A type epoxy resin having allyl group with hydride terminated polydimethylsiloxanes. ESDGs were mixed with a commercial epoxy resin (DGEBA) in various ratios. The mixed resins were cured with triethyleneglycoldiamine. The effect of the amount of siloxane units on toughness, heat-resistance and adhesive properties of cured resins were investigated. The addition of 10wt% ESDG resulted in a 40% increase in the toughness (Klc) without reducing heat resistance. SEM showed that the improvement depended on the microphase-separated structure. Peel strength of adhesives were improved by the addition of ESDG.

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Epoxy resin was modified with ethylene-based copolymer. Two types of ethylene-based copolymers were used in this study; ethylene acrylic rubber and ethylene-based ionomer/clay nanocomposite. For　the ethylene acrylic rubber-modified epoxy, three types of hardeners were used and the effect on microstructure and mechanical properties (dynamic viscoelasticity and fracture toughness) was investigated. The hardener considerably affected the microstructure, and this led to the differences in dynamic mechanical properties. The fracture toughness values were not so much improved. For the ionomer/clay-modified epoxy, effect of hardener content on mechanical properties was investigated because ionomer is expected to react with epoxy resin. The dynamic viscoelastic tests showed that the glass transition temperature (Tg) was increasing with decreasing the hardener content. For one resin system, the Tg disappeared and thermal resistance was greatly improved. Fracture toughness was decreasing with decreasing the hardener content. In particular, the fracture toughness value of the system without Tg was 40% less than that of the unmodified system. These results can be explained by increase of crosslink in epoxy matrix which were caused by the reaction with epoxy and ionomer.

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The effect of interfacial adhesion on the mechanical properties of an incompatible polymer blend was investigated. For this purpose, the preparation of uncrosslinked and crosslinked poly(methy lmethacrylate) particles having mean sizes of about 0.8 μm was completed by a seeded emulsion polymerization, and amount of crosslinked points in the particles were varied. The obtained emulsion particles were powdered by a freeze dry method and dispersed into poly(vinyl chloride) matrix, as typical ductile polymer, by a melt blending. The mutual diffusion of the polymer molecules at particle/matrix interfacial regions was restricted by the crosslinked points,because of poly(methyl methacrylate) has a good compatibility with poly(vinyl chloride). And then, the good interfacial adhesion was obtained at the optimum amount of crosslinked points in the particles. The yield stress and the fracture toughness never decreased, when the interfacial adhesion is sufficient. Subsequently, the particles were dispersed into epoxy resin, as typical brittle polymer, which has also a good compatibility with poly(methyl methacrylate). However, the good adhesion was never obtained in the epoxy system, therefore, the fracture strength and the fracture toughness decreased with the incorporation of particles.

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