Preparation of a removable polyurethane encapsulant

The preparation of polyurethane encapsulants, based on polyether diol/diisocyanate prepolymers and 1,4-butanediol, which are soluble in several organic solvents, was investigated. Since these materials can be easily removed, repair of electronic circuitry found defective in potted units can be readily accomplished. Polyether diols of varying molecular weights were reacted with toluene diisocyanate (TDI) and methylene diphenylisocyanate (MDI) to produce stable prepolymers. Several properties of both the isocyanate prepolymers and 1,4-butanediol cured polyurethane encapsulants are presented.