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Temperature‐dependent effects in base oils: Carbon‐13 NMR spin‐lattice relaxation time and viscometry studies
Author(s) -
Kapur G. S.,
Sarpal A. S.,
Bhatnagar A. K.
Publication year - 2002
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.3010140302
Subject(s) - microviscosity , viscometer , viscosity , arrhenius equation , thermodynamics , viscosity index , base (topology) , chemistry , relaxation (psychology) , carbon 13 nmr , materials science , analytical chemistry (journal) , organic chemistry , activation energy , base oil , scanning electron microscope , psychology , mathematical analysis , social psychology , biochemistry , physics , mathematics , membrane , composite material
Carbon‐13 NMR spin‐lattice relaxation time (T 1 ) data have been used to study the molecular dynamic aspects of base oils with different physical properties. Relaxation time measurements have been carried out on a few model compounds and a number of mineral base oils at various temperatures (273–373 K). Effective correlation time (° C ) and rotational mobility data obtained for the model compounds and base oils have provided evidence of relationships between molecular flexibility and the temperature dependence of viscosity. It is possible to determine the average carbon alkyl chain lengths and the molecular weights of the base oils from the ratio of the T 1 values of C β and C int carbons and the optimised value of the microviscosity factor (f r ), respectively. A qualitative correlation between Arrhenius energies (E a ) for microscopic motion and macroscopic bulk properties such as viscosity and viscosity‐temperature characteristics has been observed. Base fluids having better viscosity‐temperature characteristics were also associated with lower values of E a for micro‐ as well as macroscopic processes.