The Effect of Water Ingress on the Thickener Structure in Bio-based Greases By: Johanna Larsson and Roland Ardai Axel Christiernsson International AB ABSTRACT
Environmentally adapted greases are coming into contact with water in most applications where they are used. Even when they are contaminated with water these greases are expected to provide lubrication, protect component surfaces and keep contaminants out of bearings while maintaining their rheological properties. Additionally, in the event of release into the environment, these greases need to decompose without any, or at least minimal, impact. Previous studies performed by the authors evaluating different types of bio-greases contaminated with water have shown superior performance of anhydrous calcium greases. The ability of a grease to keep its technical performance after water ingress is related to how water interacts with and affects the thickener structure. This paper presents how different oil and thickener combinations respond to water and how this affects grease performance as lubricants at both normal operating conditions and at low temperatures.
INTRODUCTION
The more stringent government regulations worldwide have led to an increased number of enquiries and requests for bio-greases. For a grease producer, this leads to the need for continuous product development of high performing bio-greases, designed to be suitable for specific applications. Even in regions without regulations, the availability of a wide range of bio-greases makes it possible for the end-users to have the choice of using a grease with less environmental impact. But how can an end-user be sure that a good choice is made? To combine the demand for environmental behaviour and technical properties of lubricants, many countries have introduced local and general labelling programs based on voluntary schemes called ecolabels. Ecolabels identify the environmentally preferable products within a product category, and the authorization to use an ecolabel is granted by an independent body. The purpose of the labels is primarily to provide a guide for consumers searching
for “greener” products for their applications. The first ecolabelling program was set up in Germany 1977 and called the Blue Angel (Der Blaue Engel). The Nordic Swan was started in 1989, and the European ecolabel, called EU Flower, in 1992. In North America, the Environmental Choice program was started in 1998 in Canada and the US Green Seal in 1989. Also Japan set up its eco-labelling programme, EcoMark, in 1989 [1]. The world´s first government regulation requiring environmentally acceptable lubricants (EALs) for marine use is the Vessel General Permit or VGP 2013. This regulation is strongly impacting the marine industry, saving our waters and growing the EAL market. According to VGP 2013, all lubricants used in an oil-sea interface must either be EALs or compliant with an approved international eco-labelling scheme. This means that even though criteria may be different, all international eco-labelling schemes are valid for products to be considered as EALs by VGP 2013. Therefore, not only products for the marine industry are covered within VGP, but those suitable for land-based applications too. Even though the market share of bio-based greases is low overall, the need for development work is high as new regulations force a greater volume of EALs to be used [2]. And who knows what is to come? For example, VGP will be revised during 2018, and EU ecolabel is under revision already. According to the 2015 NLGI Lubricating Grease Production Survey Report, 0.68% of the total reported global grease production used bio-based fluids. The survey shows that the demand for bio-based greases is on the rise, from a share of 0.54% in 2012, which represents a worldwide increase of 26% over a period of 4 years. Europe has the largest share of 2.44%, which reflects an increase of 39% when compared with the reported volumes from 2012 [3]. Due to the stringent government regulations and environmental concerns, research on bio-based lubricants is increasing. In addition, depleting petroleum reserves are leading to greater interest in research and development of
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