IntroduetionIn curing conventional epoxy resins, considerable study has been devoted to the effect of structure of polycarboxylic acid anhydrides on reactivity and resin properties. The resistance of cured resins to stress at elevated temperatures, for example, increases as the functionality or the compactness of the anhydride increases.' Pyromelletic dianhydride,2 chlorendic anhydride13 and methyl Nadic anhydride4 have been developed as curing agents leading to high softening resins. More recently, attention has also been given to the synthesis of new types of epoxides as another method of modifying the resin forming properties. The approach was stimulated by the development of economical and efficient methods of epoxidation with the use of peracetic acid.6 This paper is concerned with one of these epoxides, namely endo-dicyclopentadiene dioxide (Union Carbide Chemicals Co., Unox epoxide 207, m.p. 185OC.) : Unox 207 Anhydride Curing AgentsA variety of polycarboxylic acid anhydrides is available as curing agents for polyepoxides. The reactivities of anhydrides toward epoxides differ greatly and are related to 'the strength of the respective acids and to steric hindrance. Maleic anhydride, which is derived from a strong acid, reacts very rapidly, whereas alkenylsuccinic anhydride reacts slowly because of the bulky side chain. We have observed that maleic anhydride and Unox 207 have several unique and desirable properties in forming resins.The thermal stability of resins from Unox 207, maleic anhydride, and 2-ethyl-2-(hydroxymethyl)-l,3-propanediol (trimethylolpropane) was examined as a criterion for optimum formulations. The polyol was added to initiate the reaction. The mixtures, which are homogeneous, mobile

Resistive elements that slowly vary in time enhance the operational bandwidth of small antennas to help overcome their performance limits.

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The first study of a rare earth element-based HEO’s band structure revealed that heat treatment under different atmospheres allows reversible tuning of band gap energy.

An optical fiber coated with molybdenum disulfide can distinguish between ultralow concentrations of 12 different organic vapors