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‘Mould-in-place’ sets a new standard for automotive gaskets

28 June 2010

A new mould-in-place process for the automotive industry enables rapid injection moulding of liquid, high-performance sealing materials that cure rapidly on exposure to UV light. The technique enables components to be manufactured with integrated polyacrylate gaskets, eliminating some of the energy intensive process steps associated with form-in-place silicon rubber gaskets

Automatically dispensed liquid gaskets play a key role in modern vehicle manufacturing, a success that can be attributed to a variety of economic and technical factors, innovative materials not least among them. Applied directly to parts, they offer exceptional performance in key areas, such as the sealing of power train components.

Hitherto, these mechanical assemblies have had gaskets applied using the proven formed-in-place (FIP) technique. The gasket compound is applied in the liquid state directly to the flange face, and the two mating components are then joined together. With its new Loctite mould-in-place (MIP) technology, Henkel offers a novel processing technique that is even better suited to automotive assembly processes, offering the dual benefits of cost-savings and enhanced production flexibility. The technology combines the use of an advanced sealing material with a novel application process that produces components with integrated gaskets.

Material breakthrough
For decades, gaskets have been made from silicone rubber, but the trend today is favouring the use of ‘organic’ gasket materials based on acrylate blends. Polyacrylates have an important advantage over conventional silicone-based rubber gaskets as they are more compatible with the high-additive oils to be found in vehicle power trains. Moreover, these gasket materials offer considerably better environmental performance.

In addition to reducing hydrocarbon emissions from the engine via its exhaust system, a major consideration when designing modern engine gasket installations is permeation through the gasket itself.

Henkel chemists have succeeded in formulating a specialty polyacrylate-based, one-component liquid gasket material, marketed under the Loctite brand. The material is currently being used by leading automotive OEMs in a FIP gasket operation for power train applications. These gaskets are ten times less susceptible to hydrocarbon permeation than silicone gaskets and are therefore particularly suitable for engines that are required to meet LEV (Low Emission Vehicle) or ULEV (Ultra Low Emission Vehicle) specifications.

This material has been re-engineered specifically for the new Loctite MIP process and is now available in a transparent version. The advantage of this polyacrylate liquid gasket is that it cures within seconds when exposed to UV light.

The MIP process
The Loctite MIP gasket process is completed in five steps (see digital issue for illustrations). At the loading/unloading station, a transparent mould is fixed to the component and this assembly is transferred to the injection moulding station, where the polyacrylate gasket material is injected via a dispensing needle at low pressure and at room temperature. The liquid gasket is then cured in place within seconds using UV light, which is passed through the transparent mould. Once the component has been detached from the mould, a brief post-cure UV irradiation is required to dry the surface of the gasket.

One of the most important benefits of this technology is its capability to reduce manufacturing costs. Compared with the manufacturing processes required for conventional elastomeric compression gasket installation, the energy costs are significantly lower because the process eliminates the need for compounding and vulcanization. Nor is any post-vulcanization required, which results in considerable time savings.

Further compelling benefits include faster cycling and the elimination of manual work steps, which ensures consistent high quality results. Enhanced production flexibility is another advantage. The new automatic process permits the moulding of gaskets in many different shapes and sizes, which makes it possible to manufacture even small quantities of components quickly and at low cost.

As a systems supplier, Henkel is able to offer a complete service to OEMs under the Loctite brand. This may range from advice on how to design gaskets for effective sealing, to the integration of the gasket application into the manufacturing process. The company can offer a range of dispensing equipment, and is able to provide full technical assistance during commissioning and subsequent production.

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