EPOXIDATION OF STYRENE-BUTADIENE BLOCK POLYMERS .2.

Epoxidation of styrene–butadiene block polymers considerably improves their resistance to hydrocarbon oils. Use of peroxyformic acid generated in situ appears to be simple and practical. Although no problems exist when the reactions are carried out in toluene, polymer molecular weight and reactant stoichiometry are important in determining the properties of polymers epoxidized in cyclohexane. In fact, epoxidations in cyclohexane of linear and tapered block polymers of molecular weights in excess of 60,000 with peroxyformic acid invariably lead to gelation. Replacing half or more of formic acid with acetic acid, however, alleviates the problem without adversely affecting the tensile or oil resistance of the resulting polymers. This recipe has also been successfully applied to the epoxidation of divinylbenzene‐coupled styrene–butadiene radial block polymers. Copyright © 1979 John Wiley & Sons, Inc.