Antioxidants include such compounds as phenols and particularly hindered phenols including Irganox??? 1010 from Ciba Additives of Tarrytown, N.Y.; sulfides; organoboron compounds; organophosphorous compounds; and N,N???-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide), available from Ciba Additives under the trade name Irganox 1098.