Preparation and Characterization of Gel-like Dispersions Based on Cellulosic Pulps and Castor Oil for Lubricant Applications

Abstract

In this work, the use of different cellulosic pulp samples to prepare new formulations potentially applicable as biodegradable lubricating greases is explored. Cellulosic pulps from different raw materials and submitted to different pulping process and/or several acidic treatments were characterized and used as biothickener agents to formulate gel-like dispersions. Cellulose pulp samples mainly differed in polymerization degree (160−893 cm3/g) and lignin (0.3−27.1% w/w) and α-cellulose (46.0−85.1% w/w) contents. Rheological measurements and some standard mechanical tests usually performed with lubricants were carried out. The rheological response of cellulosic pulp-based gel-like dispersions is mainly a consequence of the balance between the cellulose polymerization degree and lignin and α-cellulose contents, independently on the origin of cellulose samples and pulping treatment. An empirical correlation between a power function of these variables and the plateau modulus has been proposed to predict the rheological behavior of resulting formulations. However, cellulosic pulp-based dispersions studied generally present either poor mechanical stability or low consistency indexes than expected for lubricating greases.