Tribopolymerization: Anti-Wear Behavior of New High Temperature Additive Classes
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New additives included aromatic compounds with various pendant groups adding the design functionality necessary for in-situ polymerization. The amino, hydroxyl, acid, and ester functional groups underwent studies across several aromatic molecular compositions while new heterocyclic additives, in particular the readily available lactams, underwent exploratory tests as a new class under the tribopolymerization design approach. In concentrations of 1%, additives showed significant wear reductions of up to 99.9 %. Anti-wear behavior persisted in select cases at concentrations as low as 0.1% by weight. Compounds from two new classes demonstrated anti-wear behavior at 6x the frictional heat generation of standard exploratory conditions. This surprising effect partially filled a void in the effective range of operating conditions between 0.25 m/s, 40 N and 1.0 m/s, 160 N. Earlier work by Tritt found a complete absence of anti-wear behavior for the previous additive classes at the high-speed conditions.
In addition, several individual compounds constituent to an A-R-A + B-R'-B condensation polymerization reaction demonstrated significant anti-wear behavior when used alone. In particular, the compound BTDA from DuPont's Kapton Â® exhibited higher wear reductions than any other new additive.
These findings support tribopolymerization as an effective approach to boundary lubricant design. Low wear was often associated with an attached reaction debris layer. This finding is consistent with previous work involving tribopolymerization anti-wear additives with ceramics. Further research into the roles of the debris layer and tribochemistry will help in understanding the complex anti-wear behavior of these new high-temperature additive classes.
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