1)where vJV is the secondary crosslink concentration, A a constant, R the general gas constant, T the absolute temperature, and E,, is the activation energy of bonding. The equilibrium modulus of a rubtkrlike species, U J U , is related to the primary crosslink density, v,/V, and the absolute temperature T in accordance with the kinetic theory of elasticity,* U,/U = (ve/V)RT(2)

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Butyl rubber vulcanized with 2,6-dimethylol-4-hydrocarbylphenols or condensation polymers derived therefrom shows exceptional thermal stability. This offers a means of obtaining economical and highly heat resistant vulcanizates. Vulcanizates prepared in this manner resist aging from four to ten times as well as do vulcanizates prepared with sulfur and sulfur vulcanization accelerators. It is estimated that the upper temperature limit of serviceability of butyl rubber may be increased by 100° F through the use of this vulcanization system.

Ethyl Methyl Cetyl Malonate.-To a solution of 5.2 g. of sodium in 100 cc. of absolute alcohol, 40 g. of ethyl methylmalonate was added. Then, 77 g. of cetyl iodide was added and the mixture refluxed until neutral. The alcohol was distilled in vacuo and the residue extracted with ether. The oil obtained after concentration was fractionated at reduced pressure: at 1 mm., b. p. 185-190°; yield 63 g.