Interaction of paraffin wax gels with ethylene/vinyl acetate co-polymers

Henry S. Ashbaugh, Xuhong Guo, Dietmar Schwahn, Robert K. Prud'homme, Dieter Richter, Lewis J. Fetters

Research output: Contribution to journalArticlepeer-review

113 Scopus citations


The commercial grades of ethylene/vinyl acetate (EVA) co-polymers have found application as "pour point" depressants in refined fuels. This study focuses on their behavior as additives to crude oils, where the intent is to reduce the yield stress of the gels that can form when the oil exits the reservoir. The model crude oils consisted of 4 wt % wax in decane. At EVA dosage levels of ∼200 ppm, the reduction in yield stress is 3 orders of magnitude for the C36 wax, whereas the reduction is 1 order of magnitude for C32 and only 3-fold for the C28 wax. This decrease in efficiency with decreasing wax carbon number indicates that the EVA materials would not provide an adequate reduction in yield stress to ensure against gelation in pipeline transport. Neutron scattering studies, as a function of temperature, of the self-assembly of the EVA co-polymers show dramatically different aggregated structures in decane. The EVA with the lowest ethylene content shows scattering that increases with a power-law exponent of ∼1.6. This scattering behavior is typical for weakly aggregating polymer gels. In contrast, the EVA with the higher ethylene content shows a transition from surface scattering (found for strongly segregated objects) to a plateau whose height is dependent on temperature. Micrographs of the wax crystal morphology indicate that the ethylene-poor EVA alters the wax crystal habit at higher concentrations more effectively than does its higher-ethylene-content counterpart, whereas the latter EVA grade seems to form more wax crystals at low concentrations.

Original languageEnglish (US)
Pages (from-to)138-144
Number of pages7
JournalEnergy and Fuels
Issue number1
StatePublished - Jan 2005

All Science Journal Classification (ASJC) codes

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology


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