Sulfur Compounds Lubricant Additive Action

TABLE 11-6. EFFECT OF DISULFIDE ADDITIVES ON WEAR RATE 

Wear is measured by the increase in the radius of the scar on the end of a conically-tipped pin. From data by Dorinson and Broman [24]. 

Since m and fe are constant for fixed rubbing conditions (fixed pairs, fixed contact pressure, fixed rubbing speed), we can write 1. 

The value of Cfe for di-t-octyl disulfide and for di-n-octyl disulfide at a given temperature can be computed from Eqns 11-la and 11-1b. Because these equations were fitted to data for 25% additive in white oil, adjustment for concentration uses the fact that the rate of a pseudo-zero-order reaction is a linear function of concentration. Let us select 498 K (225 C) as the temperature the computed values of Ck are 

35 x 10 and 4.72 x 10 gram-atom of sulfur per cm per minute for a 23% solution of di-t-octyl disulfide and di-n-octyl disulfide respectively. Let us utilize these values in the analysis of the relative wear rates for hardened AISI 1095 steel at 2586 MPa shown in Table 11-6. From Eqn 11-3b we get 

---

The work of Dorinson [63] on the relation between the basic chemistry and the additive action of sulfurized fatty materials deals with one of the most widely used multicomponent lubricant additives in industry. There are two aspects to the multicomponent nature of products of the sulfurization of ethenoid fatty esters. One is the consequence of the complexity of the sulfurization reaction, so that even if the starting material is a pure fatty ester, the ultimate sulfurized product is a mixture of several species. But the most important aspect of the structure of the sulfurized fatty product is the fact that even were it a single-component substance, it would still be intrinsically multifunctional. For instance, Dorinson [63] reported that the product of the sulfurization of methyl u-undecenoate can be shown to contain at least 50% of the following compounds ... 

Moreover, European regulations in 2005 restricted the sulfur content in diesel fuel to SOmgkg. Sulfur organic compounds are known to provide diesel fuel with a lubricity that will disappear as the regulations take effect. Addition of biodiesel at a level of 1-2% to diesel blends has the effect of restoring lubricity through an antiwear action on engine injection systems, which is specific for polar molecules. 

---