There are three predominant aspects of the rheological requirements: maximum possible high temperature thickening,minimum possible low-temperature thickening,and high shear stability for automatic transmission fluids....There are three predominant aspects of the rheological requirements: maximum possible high temperature thickening,minimum possible low-temperature thickening,and high shear stability for automatic transmission fluids.High temperature thickening by VI improvers is largely a function of molecular size and high solubility to give extended polymer coil size.On the other hand,the desirable characteristic of minimum low-temperature thickening is a function of somewhat the opposite characteristic;namely relatively poor solubility leading to minimal polymer coil size and thus low viscosity contribution.In addition to not thickening fluids at cold temperatures VI improvers should also provide control of wax-gelation which,if unfettered,can lead to congealed fluids.Finally the third property of high shear stability is in direct conflict with the desirable characteristic of large molecular size for effective high temperature thickening.In this paper we shall attempt to sort out these conflicting properties and provide some insight into how we approach design of VI improvers for the highly demanding world of automatic transmission fluid rheology.展开更多
Pour point depressants(PPDs),also know as wax crystal modifiers,are polymeric materials that when added to a mineral based lubricant can significantly improve the low temperature low shear properties or pumpability of...Pour point depressants(PPDs),also know as wax crystal modifiers,are polymeric materials that when added to a mineral based lubricant can significantly improve the low temperature low shear properties or pumpability of an oil.For many years the lubricant industry has set requirements for pumpability of engine oils,with the most well known requirement being the ASTM D4684 MRV TP-1 specification within SAE J300.ILSAC has gone a step further in their GF-4 and GF-5 specifications by requiring these generations of oil to be tested for pumpability after severe ageing.As the number and severity of pumpability tests increase the need for proper PPD selection becomes very apparent.This paper will present a brief history of pumpability and the tests used to measure low temperature shear viscosity,including the new ROBO test for aged oils.Data will be presented to show that,with proper PPD selection,an oil can easily be formulated to meet all the low temperature low shear requirements of SAE and ILSAC.展开更多
By providing higher in-use viscosity at elevated operating temperatures,hydraulic fluids with high viscosity index improve the efficiency of the hydraulic system.For mobile hydraulic equipment this efficiency can be q...By providing higher in-use viscosity at elevated operating temperatures,hydraulic fluids with high viscosity index improve the efficiency of the hydraulic system.For mobile hydraulic equipment this efficiency can be quantified as an increase in fuel economy.This paper reviews the research that demonstrates these efficiency advantages in gear,vane and piston pumps and presents a method for predicting the overall fuel economy for a fleet of hydraulic equipment in operation.Finally a `Maximum Efficiency Hydraulic Fluid’ performance definition is presented which will enable an equipment operator to easily improve the performance of the system and reduce fuel consumption.展开更多
文摘There are three predominant aspects of the rheological requirements: maximum possible high temperature thickening,minimum possible low-temperature thickening,and high shear stability for automatic transmission fluids.High temperature thickening by VI improvers is largely a function of molecular size and high solubility to give extended polymer coil size.On the other hand,the desirable characteristic of minimum low-temperature thickening is a function of somewhat the opposite characteristic;namely relatively poor solubility leading to minimal polymer coil size and thus low viscosity contribution.In addition to not thickening fluids at cold temperatures VI improvers should also provide control of wax-gelation which,if unfettered,can lead to congealed fluids.Finally the third property of high shear stability is in direct conflict with the desirable characteristic of large molecular size for effective high temperature thickening.In this paper we shall attempt to sort out these conflicting properties and provide some insight into how we approach design of VI improvers for the highly demanding world of automatic transmission fluid rheology.
文摘Pour point depressants(PPDs),also know as wax crystal modifiers,are polymeric materials that when added to a mineral based lubricant can significantly improve the low temperature low shear properties or pumpability of an oil.For many years the lubricant industry has set requirements for pumpability of engine oils,with the most well known requirement being the ASTM D4684 MRV TP-1 specification within SAE J300.ILSAC has gone a step further in their GF-4 and GF-5 specifications by requiring these generations of oil to be tested for pumpability after severe ageing.As the number and severity of pumpability tests increase the need for proper PPD selection becomes very apparent.This paper will present a brief history of pumpability and the tests used to measure low temperature shear viscosity,including the new ROBO test for aged oils.Data will be presented to show that,with proper PPD selection,an oil can easily be formulated to meet all the low temperature low shear requirements of SAE and ILSAC.
文摘By providing higher in-use viscosity at elevated operating temperatures,hydraulic fluids with high viscosity index improve the efficiency of the hydraulic system.For mobile hydraulic equipment this efficiency can be quantified as an increase in fuel economy.This paper reviews the research that demonstrates these efficiency advantages in gear,vane and piston pumps and presents a method for predicting the overall fuel economy for a fleet of hydraulic equipment in operation.Finally a `Maximum Efficiency Hydraulic Fluid’ performance definition is presented which will enable an equipment operator to easily improve the performance of the system and reduce fuel consumption.
