Aggregation behaviour of PE-PEP copolymers and the winterization of diesel fuel

Results from multicontrast SANS investigations of aggregates that form on cooling a solution of polyethylene(PE)-polyethylenepropylene(PEP) block copolymer in decane are reported. The PE-cores form extended crystalline platelets covered by a "brush" of PEP-"hairs" on both sides. Added wax (paraffin) is taken up by these aggregates. Decane may be considered as a model for diesel fuel and the waxes as contaminants in diesel fuel that crystallize at low temperatures and clog the filters of engines. It is explained why compounds of the PE-PEP family efficiently reduce the minimum temperature down to which these fuels may be used by directing the walt precipitation/nucleation into aggregates that are small enough to pass the filters. (C) 2000 Elsevier Science B.V. All rights reserved.