COMB-TYPE POLYMERS AND THEIR INTERACTION WITH WAX CRYSTALS IN WAXY HYDROCARBON FLUIDS - WIDE-ANGLE X-RAY-DIFFRACTION STUDIES

We report the results of our wide-angle X-ray diffraction (WAXD) studies on the interaction of various comb-type acrylate polymers, synthesized in our laboratories, with waxes crystallizing out below the cloud point of an indigenously available high-wax commercial diesel fuel. These copolymers were made from monomers from C-8 to C24 carbon numbers, which covers the average carbon number, viz., C-16-C22, of most of the commercial diesel fuels. The influence of the pendant chain on the crystallization process of n-alkanes below the cloud point of the fuel has been assessed, for the first time, to the best of our knowledge, by this method. Wax crystals, isolated by this procedure, are basically hexagonal, with some features relating to mal-structures and have similarity to the comb-type polymers with more than eight carbon atoms in their side chains. Effective pour-point depressants showed distinctive changes in the diffraction pattern of the low-angle, i.e., larger than van der Waals (LVDW) peaks, usually a general shift to higher angles, and in some cases, a distinct split. (C) 1994 John Wiley & Sons, Inc.