Surface activity studies on carbon-silica dual phase fillers using flow microcalorimetry and multiple probe temperature programmed inverse gas chromatography

Carbon-silica hybrid particles (or carbon silica dual phase fillers (CSDPF)) are used as high performance fillers for elastomers and were originally developed to combine the best aspects of carbon black and silica in one package. In this work a range of such fillers with differing silicon content have been analysed, together with a range of carbon black and silica samples, using flow micro-calorimetry (FMC) and multiple probe temperature programmed inverse gas chromatography (MPTPIGC). The probe set for FMC comprised: ethyl acetate, pyridine, tributylamine; and propan-1-ol. The linear increase in both heat and level of adsorption (from dry heptane) of all the probes within the CSDPF silicon content range investigated indicated that the interactions in the FMC were with the silica phase of the CSDPFs. FMC data for a variety of silica reference samples clearly indicates that the linear increase in adsorption activity does not continue beyond ca.15% w/w silicon. MPTPIGC data obtained using a range of saturated and unsaturated linear and cyclic hydrocarbons together with benzene and pinacolone showed no clear relationship to silicon content. In fact the retention characteristics of CSDPF resembled those of carbon black more than silica. Differences in the carbon phase of the CSDFS and carbon blacks could be resolved using MPTPIGC. This study therefore highlights the complimentary nature of FMC and MPTPIGC in surface analytical studies of fillers.