화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.105, No.22, 5139-5143, 2001
Crystal structure of wax lamellar interfaces - A residual petroleum fraction characterized by electron crystallography
After a multicomponent paraffin assembly was constructed to model a petroleum residue wax (M-w/M-n = 1.009), its structure was characterized by electron crystallography. Consistent with a single lamellar spacing, two endotherms in a DSC scan are typical of paraffin chain solid solutions and represent the premelt transition to a "rotator" phase and the true melt. The average chain packing in the crystal structure is that of the paraffin n-C32H66, in space group Pca2(1) with a = 7.42, b = 4.96, and c = 85.0 Angstrom. An attempt to account for the lamellar disorder with a chain-end occupancy model based on the chemical distribution of chain lengths is only partially successful. A better fit is found when lower chain-end occupancies are used. This discrepancy could be due to conformational defects in which the chain end atoms do not lie on strict methylene subcell lattice sites.