Created on 01.04

Overview of ZDDP (Zinc Dialkyl Dithiophosphate) on Temperature Adaptability, Type Differences, Thermal Degradation Mechanism, and High-Temperature Performance

Overview of ZDDP (Zinc Dialkyl Dithiophosphate) on Temperature Adaptability, Type Differences, Thermal Degradation Mechanism, and High-Temperature Performance
Temperature Adaptability of ZDDP:
ZDDP, due to its unique chemical structure,can remain stable at higher temperatures, which is crucial for engine oilsoperating at high temperatures. The thermal degradation temperature of ZDDPmainly occurs between 130-230 ℃, and it is generallybelieved that the rate of thermal degradation accelerates beyond 150 ℃, which coincides with the upper limit temperature that engine oilscan come into contact with.
Type Differences of ZDDP:
The type differences of ZDDP mainly stemfrom the variations in its alkyl part, which are typically introduced bydifferent alcohols. The differences in the raw alcohols used for various ZDDPsdetermine their distinct characteristics. For example, the ZDDP in dieselengine oil and gasoline engine oil differ because their oil requirements aredifferent.
Thermal Degradation Mechanism of ZDDP:
The thermal degradation of ZDDP is anautocatalytic process, mainly divided into three steps:
  1. Oxygen-sulfur exchange, where ZDDP, upon heating, has S replaced by O.
  2. Nucleophilic cyclic reaction, resulting in the formation of -SR (alkylthio), which continues to attack P, producing phosphates and R2S.
  3. In the presence of metal contact surfaces, a thermal film of ZDDP is formed.
The thermal degradation products mainlyinclude solid precipitates of zinc phosphate, alkyl sulfides, thiols, olefins,and H2S, among which some volatile substances are known as ZDDP thermalvolatiles.
Performance of ZDDP:
Thermal stability: Arylalkyl >Long-chain n-alkyl > Short-chain n-alkyl > Isoalkyl.
Anti-wear properties: Isoalkyl >Short-chain n-alkyl > Long-chain n-alkyl > Arylalkyl.
Hydrolytic stability: Arylalkyl > Alkyl> Isoalkyl.
Oxidation resistance: Isoalkyl > Alkyl> Arylalkyl.
The longer the alkyl carbon chain, thebetter the solubility of ZDDP, and the coefficient of friction will decrease.
Application of ZDDP:
In actuallubricating oil products, to balance performance, different types of ZDDP areoften used in combination to achieve a balance between cost and performance.
The interaction between ZDDP (zincdialkyldithiophosphate) and MoDTC (molybdenum dithiocarbamate) and its impacton tribological properties also demonstrates the performance differences ofZDDP. The presence of MoDTC can enhance the friction-reducing ability of ZDDP.This synergistic effect may stem from the rough film formed by ZDDP, whichprovides areas of enhanced pressure and shear stress, allowing MoDTC to reacton what would otherwise be a smooth surface.
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