Rubber selection in the automotive filtration industry

Abstract

Filters have seals to prevent leakage and to attain service intervals at required temperatures. There are various materials and the correct material must be chosen for the filter to operate efficiently and effectively. Material selection is vital as it can effectively reduce cost and if one material is selected but is more expensive and of higher quality the price can be reduced because of purchasing in large volumes. The overall aim of this study was to produce a process to follow for rubber selection for seals and grommets that would eliminate material identification testing at the automotive filter company, make the best choice based on the design of experiments (DOE) software, and to save costs by eliminating the use of over-engineered products. The objectives were to identify current rubber material types used on oil filters, conduct lab tests to determine the limits of parameters that rubber material can withstand, identify trends of testing, and lastly, determine the rubber that could possibly be used across a range of filters by using the DOE software. Materials tested included nitrile-butadiene 321 (NBR 321), nitrile-butadiene 322 (NBR 322), methyl vinyl silicone 332 (VMQ 332), nitrile-butadiene 333 (NBR 333), polyacrylate 334 (ACM 334), Viton 337, hydrogenated nitrile butadiene 338 (HNBR) and ethylene acrylic 336 (AEM 336). These materials were exposed to mineral oil and synthetic oil at operating conditions ranging from 120 °C to 150 °C and 168 h to 500 h which equated to 10 000 km to 30 000 km service intervals. The DOE software was used to develop the models in order to determine the best fit material for the required service interval and temperature. The conclusions drawn from this thesis indicate that when all these materials are exposed to mineral oil, ACM 334, Viton 337 and AEM 336 have the highest resistance to temperature and longest service intervals which is 120 °C to 150 °C at 30 000 km and, when exposed to synthetic oil, Viton 337 has the highest resistance to temperature and longest service intervals which is 130 °C at 30 000 km and 150 °C at 20 000 km. Further conclusions show that synthetic oil is a stronger fluid as it degrades all materials to a greater extent than mineral oil. It was evident from the DOE software that ACM 334 and Viton 337 were found to be the best solutions. The desired solution is closest to material ACM 334 at a temperature of 124 °C and service interval of 172 h (refer to table E.15). The trends observed were an increase of hardness and change in volume as temperature and exposure periods increased and a decrease of tensile strength and elongation as temperature and exposure periods increased. This is an agreement with findings in the literature (Refer chapter 2, section 2.1.6) which validates these trends.