HOW TO ENHANCE THE PROPERTIES OF A BROMOBUTYL BASED INNER LINER BY THE USE OF PRECIPITATED SILICA .2. INFLUENCE OF MAGNESIUM-OXIDE AND COUPLING AGENTS

A new high dispersibility low specific surface area precipitated silic a (S-BET = 74 m(2)/g) have previously been shown to be an attractive f iller for inner linear compound. Such a silica offers, after adjustmen t of the formula, one solution to the problem of fatigue and improves most of the properties of an inner linear compound compared to carbon black. Various coupling agents are investigated. The dominant ageing m echanism of all silica filled Bromobutyl is obviously different from t he mechanism of the black compound. A correct adjustment of the MgO co ntent improves ageing resistance of white compounds. We confirm that t he higher the modulus 300% (coupling), the higher the fatigue resistan ce is before ageing of a silica-filled compound in contrast to black c ompounds.