engleski

The synthesis of PAMA viscosity index improvers and pour point depressants of high shear stability

Recently, the automotive lubricant market undergoes a period of intensive change. New emissions legislation is resulting in new engine designs and after treatment systems that will require development of new generation of advanced engine lubricants in order to meet the performance demands of the future. Oils are formulated to improve fuel economy as well as to provide shear, thermal and oxidative stability at higher operation temperatures. The size of the polymer molecule affects the thickening of lubricating oil at all temperatures: the larger the coil size, the higher the thickening power. However, when polymers are subjected to high shear stress in equipment, the random coil is severely distorted. In extreme cases (shear rate higher than 104 sec−1), bond energies can be exceeded and the polymer chain breaks. If it happens, the molecular weight of the polymer decreases, which causes the reduction of solution viscosity and the VII efficiency. Unfortunately, the higher molecular weight polymers are not only the most efficient thickeners but also the most susceptible to shearing effects. Therefore, two key properties of VIIs that need to be balanced for a specific lubricant application are shear stability and thickening efficiency. In this work poly(alkyl methacrylate) (PAMA) additives (viscosity index improvers and pour point depressants) of improved shear stability were synthesized in solutions of API Group I and III mineral base oils and PAO synthetic base oil. The relationship between molar mass distribution of polymer and concentration of chain transfer agent in reaction mixture was established.

viscosity index improvers ; shear stability

nije evidentirano