Original scientific paper
LUBRICATING MINERAL OIL POLYMERIC ADDITIVES BASED ON STYRENE AND ALKYL METHACRYLATE TERPOLYMERS
Zvonimir Janović
Ante Jukić
Elvira Vidović
Jakov Romano
Ankica Barišić
Meri Picek
Abstract
Abstract
The applicative rheological properties of prepared polymeric additives on the basis of styrene, dodecyl methacrylate and octadecyl methacrylate in the composition range of up to 25 wt. % of styrene in base mineral oil solutions have been examined. In addition, terpolymerization reaction was thoroughly investigated. The monomer conversions were estimated by 1H NMR spectroscopy and the average molecular weights by size exclusion chromatography. The low conversion terpolymers showed a good agreement between experimental and theoretical composition data, calculated from the Alfrey-Goldfinger’s terpolymerization equation. The conversional heterogeneity and lines of unique and binary azeotropic compositions were also established. The high conversion polymerizations as 50 wt. % solution of the monomer mixture in base mineral oil were carried out under isothermal reaction conditions, at 100 ºC, with peroxide initiation. By increasing styrene content in the monomer mixture, both the initial reaction rate and the molecular weight of obtained terpolymers were decreased.
The rheological properties of polymeric additive solutions in base mineral oil were established by kinematic viscosity, viscosity index, shear stability and pour point temperature determinations. It was found that the kinematic viscosity does not change significantly in dependence of terpolymer composition and shows a linear dependence on molecular weight. Increase of styrene content in the additive resulted in a decrease of viscosity index from 176 (wST = 5 wt. %) to 150 (wST = 25 wt. %), while the shear stability index also decreased. The pour point temperature increased first slightly, from -33 ºC to -27 ºC (wST = 15 wt. %), and then sharply. Based on the ratio of specific viscosities at 40 and 100 ºC (Q factor), for investigated additives, the value of 0.95 was obtained, which is very close to that of PAMA (Q = 1.05), showing the similar thickening effect.
The obtained results have demonstrated that the efficiency of additives on the basis of styrene/methacrylate terpolymers is fully comparable with that of purely methacrylic additives and gives prospects for their properties’ optimization through composition and structural changes.
Keywords
aditive for rheological properties of mineral base oils; styrene/DDMA/ODMA terpolymer; azeoztropic terpolymerization conditions; dodecyl methacrylate; octadecyl methacrylate; mineral base oil
Hrčak ID:
7310
URI
Publication date:
30.4.2004.
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