The casing construction studied here comprises cord layers-adhesive layerrubber (Figure 1). Owing to the action of external forces and internal tensions, while the cover is in service, separation may occur. Separation takes three forms: (1) the adhesion type, i.e., when the adhesion becomes less than the cohesion of the bonded materials ; (2) the cohesion type, when the adhesion is greater than the cohesion of the bonded materials ; and (3) the combined type when the adhesion approaches the cohesion. In order to eliminate adhesion type separation, it is necessary to increase the bond strength of the system. This can be done by three methods: (1) changing the type of cord; (2) using impregnating compositions; and (3) changing the rubber compound. The type of cord has a marked effect on the bond strength. For example cotton cord results in considerably greater bond strength value than artificial or synthetic fibers. The composition of the rubber compound also shows a marked effect on the strength of bonding with cord. The introduction of a series of plasticizers into the mix results in a fall in the strength of the rubber/cord bonds, and the use of active fillers causes the strength to increase. The effect of cord type and the composition of the casing rubber on the bond strength in the construction studied will be the subject of a separate investigation. The present report deals with the effect of the composition of the impregnating layer on the strength of the bond between the impregnated cord and the rubber.

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