ZDDP types

ZDDP type R-group chain structure example Chemical name Abbreviation... 

At the final step of the test, engines from nine taxi cabs operating each on a different oil type, and camshafts and valve filters from the remaining 47 taxi cabs have been removed and inspected. Test results for nine taxi cabs using different ZDDP and ZDDP-type mixtures are presented in Table 6.10 (Smolenski and Kabel, 1983). Other results and observations in a number of performances in the taxi cab test are as follows ... 

Sequence IVA Cam Wear versus ZDDP type and Proprietary Molybdenum... 

Kulczycki, A. and Kajdas, C. (1994) The influence of base oil properties on the efSciency of action of ZDDP-type additives. Ljibr. Sci. 6 161-179. 

The antioxidant nature of ZDDP has often been considered to be antagonistic to its antiwear performance. The most probable reason that can be given for this is the depletion of active ZDDP in the antioxidant action. In the case of diesel engines, special types of interaction are reported. Incomplete combustion of diesel fuel coupled with oil particulates in diesel engines lead to the formation of thick... 

ZDDPs are formed by the reaction of phosphorus pentasulfide (P2S5) dimer with alcohol (ROH) or phenol (dithiophosphoric acid ester formation), followed by reaction with zinc powder or zinc oxide or with zinc chloride and sodium hydroxide solutions (see below). The various types of ZDDPs differing in R-group structures are shown in Table 2.6 (SAE, 1983 Yamaguchi et al., 1966). Scheme of the formation of zinc dialkyldithiophosphate, ZDDP ... 

Table 2.6. Types of ZDDPs (primary, secondaiy) with R-group chain structure (long, medium, short) and examples of alcohols...

Oxidative degradation test ISOT. The oxidative stability of RMs of borates and carbonates with sulfonates and salicylates were evaluated in the presence of ZDDP. The concentration of secondary type zinc dialkyldithiophosphate was 1 wt% and that of the detergents was 2.2 wt% in SAE 10 mineral oil. Table 3.8 shows the results (Inoue, 1993). 

Comparative friction tests under boundary conditions suggest three types of interactions between ZDDP and carbonate-sulfonate RMs in the oil phase (Kapsa et al., 1981) (a) chemical interactions between ZDDP and hard-core RMs of carbonate-sulfonate lead to an effective ZDDP concentration decrease (b) the detergent effect due to the presence of calcium sulfonate molecules prevents materials from agglomeration during running (c) the specific role of the hard-core reverse micelles. 

The antiwear mechanism of ZDDP in the presence of dispersants has been studied and it has been concluded that ZDDP forms an association complex with an amino group of a succinic type dispersant, and this complexation has been proved to be antagonistic to antiwear action (Gallopolous and Murphy, 1991 Rounds, 1986 Shiomi et al., 1986 Willermet et al. 1995b). The solubilization of ZDDP helps the adsorption of ZDDP on the surface, thus improving the antiwear performance of the additives (Forbes et al., 1970b). RMs would decrease the... 

Polar additives in oil formulation What type of interactions can you predict in the engine oil two-component system ZDDP + dispersant (a) in the hydrocarbon formulation, and (b) on the surface Consider the stronger the complexation, the greater adverse effect on wear. 

Temperature effect on reduction of friction. Thermal stabilities of molybdenum dialkyldithiophosphates (MoDDP) are much lower (below 180 °C) than those of the corresponding MoDTC, 300°C. The type of ZDDP must also... 

Equations of this type can describe both the physical dipole/dipole interactions and the subsequent desorption from the film. Since ka and k have different temperature coefficients, increasing temperature can lead to either increased, decreased or unchanged surface coverage. Provided that a critical minimum surface is maintained, wear and friction can be controlled. But once 0 falls below this critical value, believed to be approx 0.5, friction and wear will rise. The adsorption of dilinoleic acid [4], a series of organic sulphur compounds [5] and a ZDDP (zinc dialkyldithiophosphate) [6] has been described in these terms. 

It was also shown that PIBSA/PAM-type dispersants were able to convert basic (more thermally stable) ZDDP to normal (more active) forms [52]. Thus dispersants in general are expected to be beneficial for wear protection and it has been demonstrated that succinimide dispersants can partially remove films formed by ZDDP under rubbing conditions [53]. It is not known whether or not the dispersant used was borated, which may influence this phenomenon significantly. 

In the selection of an appropriate corrosion inhibitor, an important consideration is the problem of adverse competition with other additives designed to adsorb on the liquid-metal interface. Extreme pressure and/or antiwear agents compete for the same sites as the corrosion inhibitor. Eatty amines are good corrosion inhibitors in this type of environment. However, their adverse effect on the performance of ZDDP additives often prohibits their use. Half esters or amides of dodecylsuccinic acid, phosphate esters or thiophosphates are frequently employed. A combination of inhibitors is sometimes used, for example, fatty carboxylic acids or the dimer/trimer analogues of the unsaturated acids, e.g. oleic, used in conjunction with an amine such as an ethanolamine or alkyl amine, or amide such as alkyl imidazoline and sarcosines, Eig. 6.7. Shorter chain carboxylic acid and amines are used as volatile corrosion inhibitors. 

Liu and Park " in their study on deactivated automotive catalysts in the presence of zinc dialkyl dithiophosphate (ZDDP) and Pb showed the formation of AIPO4 by reaction wit the support. The deactivation was due to several types of interaction with the alumina support, including the formation of an impervious layer on the washcoat or sintering of the y-alumina particles in the washcoat. 

Table 6 - Variation of PEI with Type and Preparation of ZDDP...

FIG. 10—Plot of PEI data from Table 6 showing the clear differences of type of alcohol chosen and the chemistry ofpreparation of ZDDP. 

---