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Engine Oil Additive Shear Stability
Sep 07, 2017

engine oil additive Shear stability

In the engine oil additive, the tackifier only plays a part in increasing the thickness of the elastomeric hydrodynamic lubricating film (EHD) for three reasons. (1) In the EHD oil film, the polymer molecules can be aligned in the direction of motion , The spatial size of a tightening trend; ② polymer molecules blocked in the contact area can not enter the entrance of the EHD membrane; ③ polymer molecules were cut.

Shear stability is an important indicator of engine oil additives, especially when compared to other oils, because of the shear stress that has been previously described, the engine oil additive is the largest. On the test method for the stability of the engine oil additive, it is believed that the ultrasonic method (SH / T 0505) is not suitable for the engine oil additive, the first is the harshness is not enough, and the repeatability of the ultrasonic test is not satisfactory; (SH / T 0103), used to deal with internal combustion engine oil and hydraulic oil can be, for the larger viscosity of the engine oil additive is reluctant to the results of the repeatability of the problem; so, FZG gear testing machine ( SH / T 0200) and the engine oil additives more close to the actual conditions, such as the selected test conditions, 6 load, 90 ℃ oil temperature, 3000 r / min, 20 hours, measured before and after the viscosity loss of oil The test sample will have a good distinction, the lack of the test sample size is slightly more. Recently introduced a "transmission lubricant viscosity shear stability of the determination of - tapered roller bearing test machine method", more than a good choice to reduce the amount of the sample, test costs and workload is relatively small, Yes!

In order to ensure the shear stability of engine oil additives, we generally use low molecular weight polymethacrylate, low molecular weight polyisobutylene as a tackifier. Polyisobutylene with a weight average molecular weight of 2000-4000 can be used in industrial engine oil additives to ensure the shear stability of the product, but it should be noted that such polyisobutylene should be hydrogenated to maximize the effect of bis Key to saturation, to ensure that the thermal oxidation of oil stability is no problem. It is interesting to note, however, that the viscosity of the thickened sample tends to be smaller before and after thickening with the non-thickened industrial engine oil additive in the oxidation experiment (SH / T 0123). Thickener molecules caused by pyrolysis. Furthermore, the low viscosity of polyisobutylene is so large that it is not suitable for use as a tackifier for low-viscosity vehicle engine oil additives (eg 75W series). In this case, low molecular weight polymethacrylates are selected. , Which is also the reason for the low use of ethylene-propylene copolymer OCP in engine oil additives.

In short, for the tackifier, in-depth discussion of its structure and mechanism of action and the use of performance, in our case may be too complicated. The following are some of the things we need to know:

1, tackifier Whether it is a chain structure such as OCP or star structure such as CSI (styrene-isobutylene block copolymer), its tackifying capacity depends on its volume in the oil. Possession of the greater the volume, the stronger the ability to enhance viscosity.