Mechanism of EPR-Carbon Black Mixing in an Internal Mixer
1983 Volume 11 Issue 2 Pages 55-65
Details
1983 Volume 11 Issue 2 Pages 55-65
The mixing mechanism in a Brabender Plasti-Corder was studied on EPM- and EPDM- carbon black recipes by measuring the changes in maximum tensile strength, Mooney viscosity, extrusion shrinkage, resistivity, and morphology of the compounds during mixing. The molecule-level mechanism was also examined by correlating the above observations to the changes in free induction decay of pulsed NMR of the compounds and also to the molecular structure of EPR. The following conclusions were obtained. 1) Mixing process consists of four steps-subdivision, incorporation, dispersion, and simple mixing-as suggested by Palmgren. 2) The third dispersion step may be regarded as scraping of aggregates, either individually or collectively, on the surface of agglomerates. This is named the“onion”model. 3) Immobile polymer layer adsorbed by carbon black founds a huge net work which restricts dispersion. 4) The chance of adsorption of a polymer fraction might be proportional to the existing amount in matrix and the square of the molecular weight. Therefore, a large amount of large molecules results in ill performance of mixing. 5) The effect of branched molecules on PI value, one of mixing-processability indices, is equal to that of the linear polymer of smaller molecular weight by the conversion factor which is estimated at about 0.6 powers of the Zimm-Stockmayer g-factor of the molecule. 6) With the lapse of mixing time, adsorbed molecules are orderly rearranged, making dispersion more difficult.
EPRs were characterized by GPC-LALLS. For the accuracy, GPC-inherent phenomena such as molecular scission in columns, polymer plugging on a filter, sample-preparation method, and concentration effect of polydisperse samples have been successfully investigated. Particularly, we demonstrated that exponent b of EPR in the equation g′=gb (where g′=[η]br[η]l) is determined 1.1 by computer simulation of GPC and characterization of gamma-ray-irradiated EPM as the model of the branched polymer.
