In this review, toughening of epoxy and other thermosetting resins using vinyl polymer modifiers prepared by in situ radical polymerization is described. Radical polymerization of vinyl monomers can proceed in parallel with non radical curing reactions of epoxy resins without mutual interference, and therefore, vinyl polymer modifiers can be radically generated in curing systems of epoxy resins. Modification of epoxy resins by this "in situ polymerization method" increases compatibility between epoxy matrices and modifier polymers and toughens the cured resins with keeping other properties such as modulus and strength. Viscosity of uncured resins is also decreased and toughening process can be simplified by omitting prior preparation of modifier polymers. In situ radical polymerizations of poly(N-phenylmaleimide-co-styrene) (PMS) and PMS derivatives in curing systems of bisphenol A type epoxy resin/acid anhydride and alicyclic epoxy resin/cationic initiator toughen the corresponding cured resins without sacrificing other properties. Toughening of amine- and phenol-cured epoxy resins is achieved by using in situ generated poly(benzyl methacrylate) modifiers. Benzoxazine, cyanate ester and benzoxazine/cyanate resins are also successfully toughened by in situ polymerization method.

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The concept of increasing thermal conductivity for network polymers is described. Transportation media of thermal conduction is phonon. It is necessary to form a higher-order structure and a crosslinking density in the resin to make it easy to transport phonon. The epoxy resin having mesogen is self-ordered in curing and forms a higher-order structure and network structure, and shows a high thermal conductivity. In the composite of mesogenic epoxy resin and filler, the high thermal conductive region (focal conic domain) is formed around filler. When the content of the filler is low, the focal conic domain does not overlap. When the content of filler is increased, the overlap of the domain proceeds, resulting in high thermal conductivity. This is a technique that has become possible by using a mesogenic epoxy resin. The thermal conductivity of composite would be able to increase higher than that of alumina, using boron nitride. The maximum thermal conductivity of the composite shows 41 W/(m･K). As comparison, the thermal conductivity of the conventional epoxy resin was only 27 W/(m･K). We could confirm the superiority of the mesogenic epoxy resin.

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In order to reduce fire risk, flame retardant polymer materials have been required. Flame retardant epoxy resins also have been demanded, and tetrabromobisphenol A (TBBPA) has been used as a flame retardant. However, the use of halogen-containing flame retardants is concerned to cause the generation of halogenated dioxins during combustion. Hence, alternative halogen-free flame retardants to TBBPA have been required. Phosphorus-containing compounds have been most actively studied and actually used as the halogen-free flame retardant. This review focuses on phosphorous-based flame retardants for epoxy resins, and discusses the flame retardancy of commercially available flame retardants and recently developed flame retardants. In addition, we discuss on flame retardant mechanism for epoxy resin with phosphorous-based flame retardant.

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Epoxy polymer networks had limitations in terms of dismantlability and reworkability, due to the chemical covalent network structures. Recently, the molecular design and the composition design of epoxy polymers to enable the dismantlability and the reworkability have been intensively studied, while maintaining the high reliability of the epoxy networks. This article reviews the following items: Reworkable epoxy resin with controlling the chemical decomposition or the thermal decomposition; Dismantlable epoxy adhesives with heat-expansion agents and controlled viscoelasticity; Dismantlable epoxy polymer blends using the dissolvable property or the ion-conductivity.

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Epoxy resin compounds for encapsulation of semiconductor devices are used to protect the semiconductor devices from mechanical force, humid, heat and ultraviolet rays et al. As semiconductor packages are getting more sophisticated, smaller, and high density, they are required to offer improved performance and functionality. Recently, with the increasing global environmental awareness, the requirements for epoxy resin compounds for encapsulation of semiconductor devices have become environment responsive and energy saving. In this paper, the feature of epoxy resin compounds used for semiconductor molding compound, and the studies on flame retardancy and high heat resistance of epoxy resin compounds used for semiconductor molding compound are described.

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The relationships between crosslink density and physical thermostability or other properties were shown by using cured resin of alkyl phenol novolac type epoxy resins with different density of functional group and the cresol novolac type epoxy resins with different number of average functional groups. The quantitative results of the influences of density and number of functional group on glass transition temperature and other important performances were introduced. On the other hand, chemical thermostability was analyzed by using commercially available epoxy resins with various structures. The elevation of crosslink density for high heat resistant caused deterioration of other performances. This mechanism was explained according to previously reported theories. Additionally, the developments of not only good physical thermostability, but also good chemical thermostability, were achieved by novel epoxy resin with special skeleton.

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