Bio-Based Polyricinoleate and Polyhydroxystearate: Properties and Evaluation as Viscosity Modifiers for Lubricants

• Published in: ACS applied polymer materials Vol. 3; no. 2; pp. 811 - 818
• Main Authors: Méheust, Hélène, Le Meins, Jean-François, Grau, Etienne, Cramail, Henri
• Format: Journal Article
• Language: English
• Published: American Chemical Society 12.02.2021
• Subjects: Chemical Sciences; Polymers; thickeners; viscosity index; polyhydroxystearate; lubricant; viscosity modifiers; polyricinoleate
• ISSN: 2637-6105; 2637-6105
• DOI: 10.1021/acsapm.0c01153

This paper aims to design bio-based polyester as a viscosity modifier for lubricant properties. Bio-based polyricinoleate (PRic) and its saturated homologous polyhydroxystearate (PHS) have been synthesized from fatty acid methyl esters. The polycondensation performed in bulk in a one-step reaction without any purification leads to two series of polyesters within a large range of molecular weights, with M w between 3 and 130 kg·mol–1. Their thermal properties were investigated. Good thermal stability was observed with degradation temperatures above 300 °C. As expected, PRic appeared to be amorphous with a particularly low glass-transition temperature, while PHS is semicrystalline. A rheological study determined that polyricinoleate entangled when its molecular weight was above 25 kg·mol–1. These two bio-based and biodegradable polymers were then evaluated as viscosity modifiers in both organic and mineral oils. PHS with high molecular weights appeared to be an excellent thickener as well as a good viscosity index improver with a viscosity index (VI) increase above +50 in organic lubricant oil and +64 in mineral oil.