The infrared spectra of methane, +butane-, and n-dodecane-sulfonic acids, their esters, alkali metal, silver and h e salts, amides, and chlorides are compared with analogous structures derived from chlorinated and chlomulfonated polyethylenes.The Bellamy and William's linear relationship between vsoI (asym.) and vso, (sym.) is valid for both the simple alkane sulfonic acid derivatives and those of chlorinated rind chlorosulfonated polyethylenes. DISCUSSIONThe infrared chtiracterization of derivatives prepared from chlorinated and chlorosulfonated polyethylenes (commercially available as Hypalon -20, -30, and -40, from E. I. du Pont de Nemours and Company, Inc.) by comparison with the spectra of simple alkanesulfonic acids and their derivatives has not always been possible, since only sparse and incomplete data concerning the latter are available.'-'The spectra of only a few polymeric sulfonic acid derivatives have been reported,6.6 and the data are insufficiently definitive to permit positive identification. This is particularly true in those cases where the groups in question (402c1, -S02R, -SGNR'R") fall within a narrow spectral range. Of particular help in assigning symmetric and asymmetric S-0 stretching frequencies of compounds containing the 4 0 , group is the correlation reported by Bellamy and Williams.' They have found that any change in vsOr (asym.) is accompanied by a proportional change in V S~ (sym.) such that a plot of vSo, (asym.) versus vso, (sym.) gave a straight line. Since the S-0 stretching frequencies are essentially unaffected by maas and coupling effects, they pointed out that the positions of VSO, (asym.) and vsO, (sym.) depend on the electronegativity of the substituents attached to the-0-group. As the electronegativity of these groups is increased, the stronger are the 6 0 bonds, resulting in a shift to higher vibrational frequencies.Some 97 compounds containing the 4 0 -group have been examined by Robinson* and found to fit the linear relationship of Bellamy and Williams. ' As the carbon atom of the grouping RSO-C was replaced by progn?ssively more electronegative groups (N, 0, C1, F), Robinson observed a propor- 1653

The chlorines in chlorosulfonated polyethylene have been characterized by kinetic analysis according to the method of Salomon. It is found that 2.7% of the total chlorine is primary, 89.8% secondary, 3.5% tertiary, and 4% is sulfonyl chloride. These results are in accord with statistical calculations based on a polyethylene model containing the same methylene‐to‐methyl group ratio as the polyethylene precursor. The types and approximate quantities of dichlorides in the chlorosulfonated polyethylene have been determined by reactions with potassium iodide and zinc dust

SynopsisPolyfunctional alcohols, acyclic, cyclic, and heterocyclic imines, and organotin oxides have been studied as crosslinking agents for chlorosulfonated polyethylene. Mechanisms for the crosslinking reactions involving the sulfonyl chloride moiety have been proposed. Differences in curing activity have been correlated with structural modifice tions of the curing agents consistent with classical chemical reactions for nonpolymeric systems. Of the curing systems examined, the polyols provide nontoxic, low cost, safeprocessing formulations offering excellent physical properties which have found use in practical commercial applications.The curing of chlorosulfonated polyethylene elastomers, commercially available as Hypalon -20, -30, and -40 (Hypalon is the registered trademark of E. I. du Pont de Nemours and Co., Inc.), to obtain optimum physical properties requires the use of both a metal oxide and a sulfur accelerator in the most commonly used systems. Metal sulfonate crosslinks are formed by hydrolysis and neutralization reactions' [eqs. (l), (2), and (3)]. The role of the sulfur accelerator appears to involve the formation of sulfur crosslinks through chain unsaturation arising from dehydrochloriDation [eqs. (4) and ( 5 ) ] . This is supported by the observation that the omission of accelerator results in inferior vulcanizates,' and the fact that the sulfonamide formed by the reaction of a chlorosulfonated polyethylene with a dialkyl anline can be cured with the sulfur curing systems used for butyl rubber. Since this polymeric derivative is devoid of reactive sulfonyl chloride cure sites, sulfur crosslink formation alone is probably responsible for vulcanization. The presence of labile chlorines, such as tertiary chlorines in a branched polymer or chlorines beta to the sulfonamide (or sulfonyl chloride) groups, is the most probable source of this unsaturation.2 where R = polymer chaiii.

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