Polymerzusätze in wälzlagerfetten

verfasst von

Matthias Gatzen, Gerhard Poll

Abstract

An experimental study was made of the effect of polymer additives in ball bearing greases using model and full-scale ball bearing test rigs. The discussion covers introduction; experimental setup (ball-disk apparatus to determine lubricating film thicknesses; test stand to study rapidly running ball bearings); one reference and five model greases; results of ball-disk measurements/rheometry; results of length of time of grease use; results of friction and lubricating film thickness measurement; and summary and outlook. Polymer additives influenced rapidly running ball bearings. The polymers did not increase the service life of the bearing grease. There were clear differences among polymers despite their same nominal viscosity. Polymer addition yielded lower operating temperatures. In short term tests at low rates of rotation the operating frictional moments and lubricating film thicknesses corresponded to the viscosity and therefore the addition of polymer in the grease was advantageous. At average rates of rotation there were starvation effects in the film thickness especially with the presence of polymer additives. At high rates of rotation the polymer additives had a favorable effect on friction because the loss of lubricant outside the bearing contact dropped in importance. At low and high rates of rotation the reduction of friction occurred by the formation of polymer boundary layers. The question remains whether a grease with a base oil without polymer additive but with comparable increased viscosity would have behaved similar to the model greases studied. The reference grease was made of a PAO ester base oil and 23% lithium 12-hydroxystearate thickener. Each of four greases with polymer additives (Polymer II, III, IV, and VI) contained polyalkylmethacrylate (PAMA) and the grease with Polymer V contained polyisobutene (PIB) all from Evonik RohMax Additives Co. The mol. wt. of polymers II, II, and V was 50,000 gm/mole, of polymer IV 200,000 gm/mole, and of polymer VI 15,000 gm/mole. The kinematic viscosity of all polymer greases was about 25.5 sq mm/sec and of the reference grease 17.6. The polymer content of greases II, III, IV, V, and VI was respectively 5.2, 5.2, 3.4, 1.2, and 8.6%.

Organisationseinheit(en)

Institut für Maschinenkonstruktion und Tribologie

Typ

Artikel

Journal

Tribologie und Schmierungstechnik

Band

58

Seiten

42-46

Anzahl der Seiten

5

ISSN

0724-3472

Publikationsdatum

03.2011

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Werkstoffmechanik, Maschinenbau, Oberflächen und Grenzflächen, Oberflächen, Beschichtungen und Folien