Silica concentration dependence of the kinetics of polydimethylsiloxane adsorption on aggregates

The kinetics of adsorption of pure polydimethylsiloxane or of bimodal mixtures, onto silica aggregates, was observed from the melt as a function both of polymer weight fraction (2.5 to 20 g/g) and of the specific area (50, 150 and 300 m(2)/g). Attention was focused on filled polymers wherein silica aggregates are connected to one another by adsorbed chains to form a network. Results were analysed according to a molecular approach. All observed kinetics curves were found to obey a property of superposition by using a suitable reduced time variable defined as : <t(M)over bar>(n)/Qi; <(M-n)over bar>, is the number average molecular weight and Q(i) is the initial amount of polymer per unit mass of silica. The rate of adsorption is proportional to 1/Q(i).