24th International Colloquium Tribology - January 2024 43 Novel Organic Friction Modifiers with Extended Performance Durability Pieter Struelens 1,* , Marion Kerbrat 2 , Micky Lee 3 1 OLEON NV, Evergem, Belgium 2 OLEON SA, Compiègne, France 3 OLEON Port Klang, Sdn Bhd, Selangor, Malaysia * Corresponding author: pieter.struelens@oleon.com 1. Introduction Tighter emission control has accelerated the progress to roll out new engine oil standards. The commitment towards more stringent greenhouse gas emission standards requires a significant improvement over fuel economy and hence the roll out of ILSAC GF-7, tentatively in Q2 2028 [1]. In the light of the upcoming ILSAC GF-7 standard, the quest remains for high-performance friction modifiers maintaining their performance over an extended period of time, ensuring long-term efficiency and effectiveness. In this study, a series of organic friction modifiers (OFM) were designed, comprising polymerized fatty acid glycerol ester and polymeric friction modifiers, to be compared with metallic friction modifier (molybdenum-based). More specific it has been shown that the use of a specific polymerized organic friction modifier allows to achieve a very low friction coefficient at low speed compared to conventional organic or molybdenum based friction modifier, even after prolonged usage. Methodology Friction reduction performance of the materials was studied using an MTM (Mini-Traction Machine, experimental conditions described in Fig. 1.) Fig. 1: Mini-Traction Machine and test condition The benchmarks used in this study are molybdenum dithiocarbamate (MoDTC) and a typical reference OFM (GMO, 50% monoglyceride). 0.5% of friction modifier (except 1.5% was used for MoDTC) was mixed with Group III base stock and was only tested if it’s fully soluble. In this study, potential chemistries of amide, polymerized glycerol ester and polymeric ester were explored (refer to Table 1). Amide 1 and 2 were fatty amides. PFGE 1, PFGE 2, PF 1 and PF 2 are based on ester chemistry with different extents of repeating units. These are designed to enhance the adsorption of the friction modifiers on the metal surface. Table 1: Properties of friction modifiers studied Friction modifiers Chemistry MoDTC Molybdenum di-thiocarbamate Reference OFM Glycerol ester Amide 1 Amide Amide 2 Amide PFGE 1 Polymerized glycerol ester PFGE 2 Polymerized glycerol ester PF 1 Polymeric ester PF 2 Polymeric ester 2. Results and Discussion Friction reduction performance The impact of temperature was studied to investigate the thermal endurance of tribofilm of different chemistries. In this case, the durability of lubrication film was tested under 100- o C and 130- o C after 8 h of ageing. Figure 2 illustrates the impact of temperature on lubricity performance of GMO and MoDTC. At higher temperature (130- o C), MoDTC did not retain its lubricity as good as it was at 100- o C. On the other hand, GMO exhibited opposite behavior at 130- o C, in which it lowered friction further than it was at 100- o C, particularly at low speed region. By using a higher temperature, this distinguishes the performance of GMO from MoDTC. Therefore, it is crucial to employ a harsher condition (such as this case) to evaluate friction modifier over a prolonged time. This could give a better picture on the performance durability of friction modifiers. Fig. 2: Impact of temperature on MoDTC and GMO 44 24th International Colloquium Tribology - January 2024 Novel Organic Friction Modifiers with Extended Performance Durability Few chemistries were synthesized and compared at 100- o C. As shown in Fig 3., the ranking of performance of friction modifiers can be distinguished as follows: PFGE2, PF2->-Amide-1, PFGE 1, PF 1 > Amide 2. This indicates a careful selection of polymeric friction modifiers could significantly enhance the formation of tribo-film on the metal surface. PFGE 2 and PF2 have generally better friction reduction, from high speed to low speed regions at 100- o C. Fig. 3: Different chemistries at 100- o C after 8 h of ageing The durability of friction reduction was further stretched by a harsher 16 h ageing test (the test began with 8 h test at 100- o C, followed by 8 h test at 130- o C). This should illustrate the lubricity retention in corresponding to part of the criteria of a longer oil interval change better. Referring to Fig 4., 16 h ageing test retarded the performance of Amide 1, PFGE 2 and PF 2. On the other hand, PFGE 1 gives a very low COF at low speed region and the performance has been drastically enhanced as compare with 8-h ageing test earlier. However, this attribute diminished when the speed increased (similar to GMO earlier). The possible mechanism that contributes to this phenomenon is currently under investigation. Fig. 4: MTM test on Amide 1, PFGE 1 and 2, and PF 2 after 16-h ageing Conclusion In response to the urge for improving fuel economy, different chemistries were explored in this study to identify more durable friction modifiers. Polymeric friction modifier, PFGE-1, stands out among the friction modifiers with a unique friction reduction behaviour seen only after 16 h ageing. This could lay a foundation for further improvement on lubricity retention in aged oil by the fine-tuning of polymeric friction modifier. References [1] F+L Magazine, ILSAC GF-7: Implementation “tentatively” planned for Q2 2028, 2022.