Shear stability is a pivotal characteristic in lubricant performance, as it gauges the ability of a lubricant to preserve its protective properties under mechanical duress. This attribute is especially critical in the context of diesel engines, which are subject to high shear conditions. The Bosch Injector Test (ASTM D6278) is engineered to evaluate the permanent shear stability of lubricants—a factor for safeguarding of engine components.
Modern engine lubricants are heavily reliant on sophisticated additive packages, as alone, base oils do not meet all the required lubricating functions. These additives frequently include polymers that are prone to shear thinning, which can downgrade the viscosity grade and escalate the risk of wear or failure in engine parts.
Employing a diesel injector apparatus, the ASTM D6278 test method is tailored to measure the shear stability of polymer-containing fluids. This test gauges the percentage of viscosity loss at 100°C, which reflects the extent of polymer degradation due to shear at the nozzle. The lubricant undergoes mechanical shearing by being forced through a pintle orifice under pressures of 13 to 18 MPa. The protocol calls for 30 injection cycles, positioning it as the least severe shearing method compared to other tests, generally reserved for engine oils and hydraulic fluids.
The ASTM D6278 test acts as a crucial quality control tool for manufacturers of viscosity modifiers and lubricant blenders, ensuring that lubricants retain their viscosity and lubricative properties even under extreme conditions. Moreover, shear stability serves as an influential predictor for the performance of multi-grade, polymer-thickened lubricants.
To quantify the test’s impact, the viscosity of the fluid is analysed both before and after the test to determine the Permanent Shear Stability Index (PSSI), in accordance with ASTM D6022. This index offers an assessment of a fluid’s efficiency and effectiveness after experiencing shear, providing essential insights for formulators and technical managers.
The Bosch Injector Test (ASTM D6278) stands as a crucial evaluation for assessing the shear stability of polymer-rich lubricants. It plays an instrumental role in ensuring that lubricants can withstand the mechanical stresses they will face in service, thus protecting engine components from excessive wear and potential failure. For manufacturers and users alike, this test is an integral component of the quality control process and is vital for predicting lubricant performance, particularly in diesel engines.
At Valorem Chemicals, our commitment to excellence ensures our products not only meet but exceed the stringent requirements set by tests like ASTM D6278, safeguarding your engine’s performance against even the most challenging conditions.
Menu