Lube-Tech
the presence of organic friction modifiers, such as glycerol monooleate and pentaerythritol [21]. The goal of this study was to determine the tribological and synergistic differences between sulphur-free, sulphur- and phosphorus-free molybdenum additives with OFMs. For testing, friction coefficients and engine wear on a model block-on-ring test ring were measured [21]. Also, interactions between these additives were observed to determine the most effective combination. Results indicated an increase in temperature with glycerol monooleate in MoDTC increased the friction coefficient, while N,N-Dimethylhexadecylamine and Pentaerithryol showed a dramatic decrease in coefficient. Also, all OFMs reduced material wear except in the BO-MA-PT formulation. Synergies for lubrication were best observed in the BO-MC-PT combination, which combined base oil with MoDTC and Pentaerythritol additives, compared to other additive combinations [21]. For applying these results to the inverse relationship between efficiency and thickness, low-friction coefficient results and anti-wear synergies indicate excellent results. However, creating lower friction oils through advanced friction modifiers can lower film thickness [22]. Future research should continue observing these synergies with an emphasis on how general friction modifier properties and their synergies affect film thickness. By preventing film thickness decline, there will be an increase in engine longevity and overall satisfaction for any application.
Functionalised Polymers
Functionalised polymers (FPs) have also been the subject of exciting advancements within tribological fields. Due to their molecular structure and observations in anchoring chemistry, functionalised polymers as friction modifiers have shown promising advancements for maintaining film thickness for engines. Advancements in ZDDP friction modifiers were seen in a study by Dawczyk et al., where they noted that an appropriate amine/functional group is imperative to friction reduction and their harmful
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
No.155 page 5
effects on ZDDP tribofilms [22]. Observations looked specifically at ethoxylated alkylamines OFMs working synergistically with ZDDP. Results from testing for friction coefficient and film thickness after ethoxylated alkylamines were combined to show any possible effects indicated that some boundary film is removed with a reduced friction coefficient. Ethoxy groups were shown to remove much of the ZDDP-tribofilm, but greatly increase friction [22]. Figure 4 below demonstrates this trend across several manufactured blends, along with surface roughness in nanometers [22]. As such, maintaining an optimal blend between ZDDP and the appropriate amount of ethoxylated alkylamines within friction modifier additives is paramount to future research. As it applies to the inverse relationship, an increase in ethoxylated alkylamines advances engine wear and, potentially, engine failure; combinations of both ethoxylated alkylamines and engine wear increase engine failure chances, given that the engine is used as intended. For synergies, the relationship between ZDDP and ethoxylated alkylamines Researchers also indicate that synergistic interaction between ethoxylated alkylamines and ZDDP indicates that their combination resulted in enhanced friction reduction and film thickness maintenance for engines. Such results prompt the formulation of lubricants and additives for low boundary friction and improved fuel economy.
Figure 4: Change in ZDDP mean film thickness and roughness (nm) 3 hours after rubbing into surface with BB (base blend) and various OFM solutions [22]
LUBE MAGAZINE NO.184 DECEMBER 2024
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