Viscosity difference as distributing factor in selective absorption of aluminium borate whiskers in immiscible polymer blends

The distribution of aluminium borate whiskers in blends of polyethylene/polyisobutylene (PE/PIB) was studied with respect to viscosities of the components. Both polymers are non-polar with slightly higher surface energy for the PE, i.e. weak filler-polymer interactions of about equal strength. The significance of the polymers' viscosity disparity can thus be studied in isolation. Two PEs and two PIBs with clearly separated flow curves (eta(PEI) > eta(PIBI) much greater than eta(PE2) > eta(PIB2)) were used. The whiskers were found in the high viscosity phase except when they promoted coherency of the low Viscosity minority phase. However, the PE's slightly higher surface energy ruled the absorption although PIE was slightly more viscous showing the relative weakness of this rheological phenomenon. Furthermore, the viscosity distributing factor was found to be less important than polar interactions. A rheological explanation is presented that supports the observed selective absorption. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.