By In-Situ Polyurethane Polymerization

In this technique a di- or polyisocyanate is mixed with di- or polyhydroxy materials and the combination is (a) partially prereacted or (b) allowed to 

TYPICAL ADHESION STRENGTHS BETWEEN FABRICS AND RUBBERS TREATED IN SITU 

An isocyanate-terminated, viscous linear prepolymer is prepared from 2 mol of hexamethylene diisocyanate and 1 mol of hydroxyl-terminated linear polyester prepared from diethylene glycol and adipic acid. Two 

In this, one part consists of a polyester or polyether dissolved in an inert solvent and this is mixed with its molar equivalent of a diisocyanate dissolved in solvent. Usually ethyl acetate is the solvent and typical solution concentrations are 70% total solids. A suitable diisocyanate would be Desmodur HH (see Fig. 8.6) in ethyl acetate at 75% solids content. At room temperature such a cement has a pot life of 1-2 days and with accelerator, only 3 h. The setting time of this cement, containing accelerators, in wood adhesion, is 4-5 h at 10°C, 7h at O C, overnight at less than 0°C. 

Similar types of adhesive formulations are satisfactory for bonding metals such as steel, soft iron, aluminium and magnesium to themselves and to each other. 

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