Single part foam sealant helps produce a better gasket

It might not have the glamour of carbon fibre, but effective seals and gaskets play a vital role in product reliability and longevity. Yet, like mechanical fasteners, specifying them is often done with little thought. Gaskets and seals are not typically associated with innovation, with the default often being whatever was used last time.

"That can be a source of frustration," said Rob Jones, managing director of Ceracon. "We have to convince people about the merits of trying something different and thatit's possible to improve the properties and processes around gaskets and seals."

Getting a gasket or seal specification wrong is asking for trouble, which is perhaps another reason for the hesitance to try something new. But, even if it is tried and tested, the status quo can be far from ideal. Pre-cut gaskets, o-rings and self adhesive foams are fiddly, labour intensive processes that can all get easily damaged during application.

For higher volume applications it's meant an automated alternative has been sought to control quality and reduce cycle times. Many opt for a two-component 'Formed-In-Place-Gasket' system, consisting of a liquid silicone and curing agent to produce flexible silicone foams directly on to parts.

However, it's a less than perfect solution, relying on the correct mix of the two constituent parts. Some variance in the mixture is inevitable and that is cause for concern as it can impact performance later in life and potentially invalidate warranties.

"Our experience is that sealing on parts is generally overlooked in the design process and subsequently it becomes a manufacturing headache in production," said Jones.

It was this that saw Ceracon bring to market a single component sealant known as 'Penguin Foam'. The material, originally developed by Japanese chemical company Sunstar, has been integrated into an automated production machine, Foamply.

"The material is unique" said Jones. "There is no single part, mechanically foamed, material on the market. Our foam can cure within 2s, so it has a very quick cycle time and also good compressive strength, high dimensional stability and low moisture absorption making it ideal for seal applications. It typically becomes water-tight with 10% compression."

Penguin Foam is a solvent-free single component elastomer that can be applied and processed at room temperature. It consists of polyurethane and silicone compounds, and can be moisture or thermally cured.

"Our single-component Penguin-Foam system generates truly closed-cell foam," said Jones. "This means that the foam structure comprises of millions of individual air bubbles. Consequently, even with a damaged foam bead surface, moisture cannot penetrate the encapsulated foam structure."

The Foamply system can adjust the quantity of compressed air bubbles to make the material harder or softer. By keeping the flow of air continuous, but adjusting the speed of the robot, the material can be used to give variable properties on the same seal.

"The seals can be continuous around a part," said Jones. "But you can vary the properties. So you can increase the quantity of foam in one area of a part and have better compression levels in that area, and vary that around the part as needed."

Contract gasketing
Ceracon offers both the complete Foamply system as either an off the shelf unit and also as custom units where required. However, it is finding the UK, in particular, is more suited to a contract gasket service business model. It means it is able to offer the benefits to the lower volume production facilities that dominate the UK market. While the foam is already used by the likes of VW, BMW and Mercedes, Ceracon's contract business is able to do anything from 10's to 10,000's, with work currently including anything from electronic boxes to automotive seals.

"You make the parts, we seal them and deliver 'Just in Time' to the production line," said Jones. "The main priorities are speed and quality and so we have an automated processing facility that uses a robot with a camera recognition system which takes a part, plasma pre treats the surface to allow adhesion of the foam, applies the wet single material that does not drip or run, and then inspects the finished product to ensure it's the required quality."

Author
Justin Cunningham

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