Characterizing the fluid–matrix affinity in an organogel from the growth dynamics of oil stains on blotting paper

Abstract

Fluid–matrix affinity in an organogel is characterized by capillarity-induced oil release using absorbing paper.

A Model Configuration For Studying Stationary Grease Bleed In Rolling Bearings

“…Here, I(i, j) and m(i, j) are the transmitted intensity and the mass of oil in the pixel at position (i, j); Ibg is the average background intensity; Apx is the area of a single pixel; c1 and c2 are constants determined by calibration. The details of the calibration procedure can be found in (31). The values of the calibration constants for the bled oils are given in Table 1.…”

“…A possible explanation for the decreased bleeding rate is the partial collapse of the grease matrix after a considerable A c c e p t e d M a n u s c r i p t amount of oil is extracted during the bleeding process. Our earlier work showed that greases with a partially collapsed microstructure bleed significantly slower (31). Similarly, diluting greases with their own base oil, a reverse process of grease bleeding, is also proven to enhance the rate of bleeding (24).…”

“…Due to capillary forces at the steel surface (32) and/or centrifugal forces caused by rotating balls (33,34), this oil film is gradually pulled towards the center of the track to the EHL contact. In our previous investigation we explained the bleeding dynamics of stationary grease from the perspective of the balance between an external driving pressure and an opposing capillary pressure in the grease matrix (31). In this bleeding model, the grease matrix is described as a porous matrix from which the oil bleeds, base on the Darcy's approach.…”

“…In our previous investigation, we determined p p  for the bleeding of a polyurea grease from a capillary rise experiment (31). However, this experiment requires A c c e p t e d M a n u s c r i p t long-term experimental data close to equilibrium so as to improve the reliability for the best fit-parameters, which is time consuming.…”

“…Based on this idea, we developed a grease-on-paper test configuration for characterizing the capillary pressure inside the grease matrix that slows down bleeding. The affinity A c c e p t e d M a n u s c r i p t of bled oil for the grease matrix, which determines this retaining capillary pressure, is estimated using a Washburn-like model based on Darcy's law, which has been discussed in details in our previous work (31). Here, five commonly used ball bearing greases are studied, confirming the applicability of this model for greases made of a wide variety of thickeners and base oils.…”