Today's emission requirements have become more stringent since catalytic converters were first introduced in the mid 1970's. As a result, the dynamics and complexity of converter assemblies have changed. Assemblies are being moved closer to the engine and are using thin wall and ultra thin wall substrates. The environmental conditions associated with close coupled catalytic converter applications are higher temperatures, vibration levels, and frequencies. Due to the application requirements and substrate material properties, the mat mount material used in catalytic converter assemblies has also evolved.
One typical mat mount material used in close coupled applications is non-intumescent. The benefits associated with non-intumescent materials include erosion resistance, thermal stability, and low peak pressure. Unfortunately, as temperature and therefore mount gap increase, the holding pressures decrease. This is particularly detrimental with low aspect ratio substrates and may result in monolith movement. The second type of material commonly used in converter assemblies is intumescent. Although intumescent materials provide improved holding pressure, this type of mat mount material is not able to withstand sustained temperatures greater than 950°C (1742°F.) In addition, it is subject to erosion and high peak pressure. These peak pressures are not well suited for ultra thin wall monolith constructions.
This paper discusses the merits of an engineered mat mount that utilizes a multi component construction comprised of intumescent and non-intumescent materials. This construction captures the benefits of both non-intumescent and intumescent materials for close coupled applications. Through the use of accelerated performance testing, the engineered mat mount has been characterized and those results will be discussed.