engleski

Influence of composition and molecular weight of a dispersant polymethacrylate additive on viscometric and rheological properties

The composition and molecular weight of polymers added to lubricating oils in order to improve their viscosity index are the key parameters, which together with temperature and chosen solvent determine size of hydrodynamic coils of polymer molecules. The size and properties of polymeric hydrodynamic coils display the most important influence on the viscosity of diluted solutions and change of oil viscosity with the temperature change. Alkyl methacrylate copolymers are particularly suitable for the optimization of the composition and structure aimed at a particular purpose and kind of base oil, since they are obtained by simple procedure of radical copolymerization. By incorporating even a small amount of functional comonomer the molecular interactions between the polymer and solvent can be affected significantly, therewith the hydrodynamic coil of polymer and the viscosity of the solution, respectively. Here it is important to maintain good properties of the basic polymer structure, such as, e.g. shear stability. In this work the viscometric and rheological properties of dispersive solutions of poly (alkyl methacrylate) and poly (styrene / alkyl methacrylate) with a variable proportion of dispersant components (dimethylaminoethyl methacrylate) are studied. Additives are prepared by radical copolymerization in solution of mineral base oils, with transfer agent. The obtained copolymers have weight average molecular weight in a range from 60, 000 to 250, 000. Kinematic viscosity and viscosity index at 40 oC and 100 oC, shear stability and pour point of polymer solutions in the oil were determined. Sastav i molekulska masa polimera koji se dodaju mazivim uljima za poboljšanje indeksa viskoznosti, ključni su parametri koji uz temperaturu i otapalo određuju veličinu hidrodinamičkog klupka polimerne molekule. Veličina i svojstva polimernog hidrodinamičkog klupka imaju najvažniji utjecaj na viskoznost razrijeđenih otopina i promjenu viskoznosti ulja s temperaturom. Alkil-metakrilatni kopolimeri posebno su pogodni za optimiranje sastava i strukture za određenu namjenu i bazno ulje, budući da se dobivaju jednostavnim postupkom radikalske kopolimerizacije. Ugradnjom već i male količine funkcionalnog komonomera može se znatno utjecati na molekulna međudjelovanja između polimera i otapala, a time i na polimerno hidrodinamičko klupko, odnosno, viskoznost otopine. Pri tomu je važno sačuvati dobra svojstva osnovne polimerne strukture, poput, na primjer, smične stabilnosti. U ovom radu istražena su viskozimetrijska i reološka svojstva otopina disperzantnih poli(alkil-metakrilata) i poli(stiren/alkil-metakrilata) s promjenjivim udjelom disperzantne komponente (dimetilaminoetil-metakrilat). Aditivi su pripravljeni radikalskom kopolimerizacijom u otopini mineralnog baznog ulja, uz prijenosnik rasta lančane reakcije. Dobiveni su kopolimeri raspona masenog prosjeka molekulskih masa od 60000 do 250000. Otopinama polimera u ulju određeni su kinematička viskoznost i indeks viskoznosti na 40 i 100 oC, smična stabilnost i točka tečenja.

dispersant polymethacrylate additive; composition; molecular weight; viscometric properties

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