Diallyl phthalate resin was modified with an epoxy resin in order to improve adhesive property, using an allylester derivative having an allyl group and carboxyl group (DAPY) as a coupling agent. Lap shear strength of the cured system was markedly improved compared with that of the diallyl phthalate resin system. By adding 10wt% of the epoxy resin, the lap shear strength was improved by four times. This can be explained by the generation of hydroxyl groups, resulting from the reaction of epoxide and carboxyl; that is, introducing hydroxyl groups caused an increase in the adhesion force between the cured resin and a steel surface. Glass transition temperature (Tg) of the modified resin was about the same as that of the diallyl phthalate resin, while thermal decomposition temperature (Td) was decreased with increasing of epoxy resin concentration. By this modification, electrical and mechanical properties were maintained at the level of the diallyl phthalate resin, though its anti-water property was decreased. Fracture toughness (K_IC), especially, was highly improved by the modification.

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The interpenetrating polymer networks (IPNs) formed diglycidyl ether of bisphenol-A (DGEBA) and poly (ethylene glycol) diacrylate (PEGDA) were prepared by simultaneous polymerization techniques. Methylhexahydrophtalic anhydride was used as curing agent for DGEBA. AIBN, BPO or DTBPO was used as radical initiators for PEGDA. The resultant products were analyzed by DMA measurements and AFM observation. As the results, the product induced by AIBN initiators system have phase-separated IPN structure. In the case of BPO initiation systems, sequential IPN was obtained. From, AFM observations, the phase image clearly shows the phase-separated structure between PEGDA and DGEBA domains.

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A synthesis of copolymers containing hemiacetal ester obtained from methacrylic acid with alkyl vinyl ethers and oxetane moieties, as well as their solubility, thermal crosslinking reaction, physical properties of the obtained crosslinked polymers were described.
Results were as follows. The copolymers containing hemiacetal ester and oxetane moieties showed good solubility. The crosslinking of the obtained copolymers based on the thermal dissociation of hemiacetal ester was carried out in the presence of aluminium 2-ethylhexanoate triethanolamine complex as a catalyst to obtain the corresponding network polymers.

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A new synthetic method for an epoxy/silicon hybrid polymer was investigated. The pre-reaction of network formation of alkoxysilane in either an epoxy compound or phenol gave a tack-free product free from byproducts. The molecular weight distribution and flowability of the obtained product depended on synthetic methods. The “reflux” method gave a desirable tack-free product under a controllable reaction condition, such as the amount of catalyst. The resin product obtained by the “reflux” method had a good flowability in a molding process. The elastic modulus and thermal expansion were measured after cured. Results showed a high modulus and a low expansion coefficient, both of which remained even in a high temperature region. This “Tg-less” behavior is called hybrid effect, resulting from the restricted motion of polymer chain by in-situ synthesized single nano-scaled silica particles. These fine particles were observed by a transmission electron microscope-electron energy loss spectroscopy.

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A tetrafunctional epoxy resin was prepared to improve the mechanical properties, especially toughness of epoxy resins. By the reaction of acetonylaceton with phenol catalyzed with hydrogenchloride gas at room temperature, was obtained tetrafunctional phenol, 2, 2, 5, 5-tetrakis-4- hydroxyphenylhexane,. The polyfunctional epoxy resin prepared by epoxydation of the tetrafunctional phenol was characterized by the measurements of epoxy equivalent value and molecular weight distribution by GPC. The thermal and mechanical properties of the cured resin were compared with those of commercial di-and tri-functional resins. The silica-composit resins were prepared by curing the resin/ organosilica-sol mixture system. The reinforcing effect of fine silica particles in the mixed resins was observed, in measurements of the mechanical properties.

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Addition of modified clay of iminobispropylamine or acetylated bishexametylenetriamine into epoxy resin makes low constant of thermal expansion (CTE). The nanocomposites of nano-scale dispersed modified clay into the epoxy resin is able to make lower CTE. By evaluating the thermal property, we found that lower CTE is available in addition to less clay amount compared to using trivial inorganic filler. However, the more nano-dispersing, the system have lower Tg value. Then, we found that dispersing clays modified guanidine, which have three or four amino groups in the chemical structure and short main chains, make lower CTE and high Tg by adding smaller amount in epoxy resin treating by the same matter.

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Material recycling of crosslinked polymers is very difficult, because the crosslinkage is formed by irreversible covalent bonding. In this review, examples of crosslinked polymers using thermoreversible networks and thermoreversible crosslinking rubber using hydrogen bonding networks under developing at Yokohama Rubber are summarized. Examples of covalent bonds and hydrogen bonds, as thermoreversible crosslinkages, are summarized. Application of the Diels-Alder reaction and ester formation reaction, as sources of covalent bonds for crosslinking, and of hydrogen bonds for cosslinking and modification are described.
Next, our proprietary thermoreversible crosslinking rubber using supramolecular hydrogen bonding networks is described. A thermoreversible hydrogen-bonding crosslinking rubber “THC Rubber” was easily synthesized by modification of a rubber with maleic anhydride followed by the addition of 3-amino-1, 2, 4-triazole (ATA). The mechanical properties of the resulting rubber were sufficiently high and more similar to the sulfur-vulcanized rubber than general thermoplastic elastomers. Re-forming could be repeat-ed more than 10 times without significantly changing its mechanical properties. DSC, and SAXS analyses revealed that the superior mechanical properties and good recyclability are attributable to the aggregated structure by strong hydrogen bonding.

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