Ana Paula Pena Almeida, Ana Paula Lelis Rodrigues de Oliveira, Cynthia D’Ávila Carvalho Erbetta, Ricardo Geraldo de Sousa, Roberto Fernando de Souza Freitas, Maria Elisa Scarpelli Ribeiro e Silva^*

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Polymer Science and Technology Laboratory, Chemical Engineering Department, Engineering School, Federal University of Minas Gerais, Belo Horizonte, Brazil.
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Abstract: In this work, a rheological study of automotive lubricant oils, neutral light paraffinic (NLP) and neutral medium paraffinic (NMP), additivated with two commercial viscosity index improvers-VIIs, based on hydrogenated poly (isoprene-co-styrene), at different concentrations, was carried out. The study included the determination of the kinematic viscosity of the mixtures, the calculation of the viscosity indexes and their behavior when subjected to various rheometric experiments, including stress sweep, steady state flow, creep and recovery, and temperature ramp oscillatory tests. The obtained results showed the efficacy of the additives as viscosity index improvers, enabling a significant increase in the viscosity index of the pure oils at relatively low concentrations. The determination of the storage (G’) and of the loss (G”) moduli for the mixtures oil/VII additives showed a large predominance of the viscous effect over the elastic one. Except when under low shear stress, the mixtures showed a pseudoplastic behavior, with the flow curves being adjusted to fit the Ostwald-de-Waele model (Power Law), with negative flow behavior indexes.

Keywords: Viscosity Index Improvers, Automotive Lubricants, Rheology, Viscosity Index, Polymer Additives

Cite this paper: Almeida, A. , Oliveira, A. , Erbetta, C. , Sousa, R. , Freitas, R. and Silva, M. (2014) Rheological Study of Polymers Used as Viscosity Index Improvers for Automotive Lubricant Oils. Journal of Modern Physics, 5, 1085-1093. doi: 10.4236/jmp.2014.512110.

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