BOUND RUBBER THEORY AND EXPERIMENT

Adsorption of polymer on filler from bulk is known to result in a partial loss of polymer solubility (''bound rubber''). The existing theories of this phenomenon were critically examined, and the random adsorption model suggested by the author was found to provide the most complete explanation of available experimental data. Theory based on this model and containing one adjustable parameter (filler surface area per adsorption site) correctly predicts the change of molar mass distribution with adsorption on filler and satisfactorily describes the experimental dependence of fraction B of the filler-bound polymer on filler concentration and surface area and on M(w)BAR of the polymer, in both narrow and very broad molar mass distributions. No distinct effect on B of a moderate degree of branching of EPM, EPDM chains could be detected. It is concluded that the modification of the random adsorption model suggested by Shiga is not warranted, neither theoretically nor experimentally. (C) 1993 John Wiley & Sons, Inc.