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Rapeseed oil and its derivatives are successfully used in formulations of eco-friendly MWFs, hydraulic oils, process oils, industrial gear oils and greases [1]. For instance, ISO 15380 compliant biodegradable hydraulic oils of HETG category of ISO VG 46 formulated from Nuspec HELP oil significantly outperform conventional HEAR based formulations in terms of oxidation stability.
new environmentally-safe alternatives to chlorinated paraffins remains an actual challenge. Polymerised vegetable oils in combination with certain classes of Extreme Pressure (EP)/AW additives and friction modifiers can in some cases replace chlorinated products. Nanoparticle-based friction-modifiers such as silica, titania and inorganic fullerene-like structures have demonstrated encouraging results in trials with advanced high-strength steel and stainless steel. In hot-forging applications, such as forging of aluminium and some superalloys, polymerised rapeseed oil can be used to stabilise graphite dispersions in phosphate esters. Eco-friendly soluble forming oils can be produced by mixing vegetable oil with various bio-surfacants, such as sorbitol monooleate.
Figure 1: Oxidation stability of conventional and ultra-low PUFA high-oleic rapeseed oil, with and without DI packages (Brad-Chem DP3101 or BD351).
In general, biolubricant formulations deploy the same additives classes as found in conventional petroleum- based products, though the additivation strategy is often reviewed to meet specific performance and environment, health, and safety (EHS) objectives. Commonly used additive classes include anti-oxidants, anti-corrosives, extreme-pressure/anti-wear. (EP/AW) additives and friction modifiers, rheology modifiers, pour point depressants and anti-foams.
One well-established application of rapeseed oil is in metal-forming lubricants. Forming oils are expected to meet a number of sometimes self-excluding requirements regarding lubricity, low misting and smoke, corrosion protection, tool life, ease of cleaning, EHS profile, and price. The forming lubricant helps reduce friction and wear of the tool and workpiece, and dissipate heat generated by the process. Currently, many stamping operations use petroleum-based vanishing oils. Fast-dry stamping oils use light petroleum distillates with flash point 40 to 80°C. Non-dry oils include oiliness additives that remain at the surface after the solvent evaporation. Some demanding stamping operations such as high-speed and stainless steel stamping require higher viscosity heavy-duty, extreme-pressure oils that often contain chlorinated paraffins. Hence, finding
10 LUBE MAGAZINE NO.174 APRIL 2023
It is well known that rapeseed oil beats mineral oil in terms of oiliness and lubricity [3-5]. However, polymerised rapeseed oil (PRO) has been shown to provide an even greater lubricity boost due to its higher affinity to metal surfaces. By co-polymerising rapeseed oil with more surface-active molecules, such glycerol mono-oleate (GMO) or oleic-acid ethoxylates, the effect becomes even more pronounced. In fact, environmentally-benign bio-based formulations can outperform conventional petroleum-based medium- duty cutting oils (see Figure 2).
Figure 2: Comparison of tapping efficiency for various oil types.
In broaching oils, high lubricity and good foam release properties of vegetable oil help prevent overheating and warping of the workpiece during machining. Nuspec HELP rapeseed oil and polymerised rapeseed oil can be used in chlorine- and sulphur-free formulations of medium-duty neat broaching oils for carbon steel. To achieve an acceptably high-weld load without using active sulphur, fatty-amine phosphates can be used.
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