The sky’s the limit

Written by: Tim Fryer | Published:

Even relatively simple products can be engineered better by using elegant design solutions. Such was the case when Sunsquare looked to improve performance and processes by use of alternative adhesives.

Sunsquare is the brainchild of technical director James Boughton, a design engineer who could see that roof and skylight design was stuck in a rut. In 2004 he sold his house and car for the funds to set-up Sunsquare in opposition to the then market leader of flat roof skylights.

Eight years ago, Justin Seldis bought-in to Sunsquare as managing director and today, under the partnership of the two owners, Sunsquare has a turnover of around £5m, a workforce of nearly 50 and two factories.

It also boasts a notable number of ‘firsts’. Sunsquare rooflights were the first to be kitemarked. It was also the first manufacturer to opt for heat soaked, toughened glass to exclude impurities for better performance and the first to have its products CE Marked. And this commitment to continuous improvement endures with traditional methods frequently making way for innovative processes.

“For example, just because the industry has always used neutral silicone to seal its glazed units, that’s no reason to presume it’s the only way or, more importantly, the best way to do it,” Boughton explained. “The biggest problem with silicone is its life expectancy and this is one of the benefits we have gained by working with Henkel.”

Indeed, when Sunsquare first opened discussions with Henkel at a trade exhibition this was one of several practices that proved ripe for change. Since that first meeting, four applications for Henkel engineering adhesives have been proposed, extensively tested and proven.

Shortening time-to-market

Although there are standard Sunsquare designs, most of the company’s products are manufactured to architects’ specification. The framework, which comprises designed-for-purpose elements rather than off-the-shelf profiles, is constructed in the first of the company’s two factories in Bury St. Edmunds. To minimise airborne contamination, glazing and assembly are conducted in a separate factory. An important driving force behind changing bonding and sealing methods was the need to equalise the output of both production units.

Around 35 frames can currently be produced per day, but glazing and assembly can only be completed on 25, a problem that could be largely attributed to the handling and curing times of the previously used bonding and sealing adhesives. Sunsquare has 48-hour turnaround in its sights so speed and efficiency, both in terms of the adhesive’s characteristics and its method of application, are now more important than ever.

The first of the Henkel products employed to address this need is most commonly used to bond windscreens in trains, buses and other vehicles facing harsh environments. It is a single-part, polyurethane Teroson direct glazing adhesive with built-in UV stability which, when applied to a vehicle, gives a drive-away time of just one hour. The product’s credentials for use in the safety-critical automotive industry together with its cure speed and ability to bond without the need for a primer, proved very attractive qualities for Sunsquare.

The only preparation that’s needed is for the frame to be cleaned with Teroson VR20, a product that had been specially developed to remove any silicone residues that remain on the glass surface and which can compromise the efficiency of the bonding process.

“By comparison with our previous glass bonding adhesive, the Teroson adhesive gives us longer open time but cures much quicker,” Boughton confirmed. “The bondline is sufficiently hardened for us to clean off any excess within the hour and a good degree of cure in just four hours.”

Further and significant production time savings have also been made by replacing the neutral silicone, traditionally used in this rooflight industry to weatherproof bond lines, with another Teroson product. Unlike silicone which is simply a sealant, the Teroson alternative is both a sealant and an adhesive that boosts the durability and performance of the end product.

The chemical basis of this product is a silane modified polymer which reacts with moisture in the air and cures to form a high performance polymer. This opaque, black adhesive and sealant is now applied as a bead to the parallel edges of each glazed joint. A polyurethane foam packer is then put in the channel and the adhesive flooded over the top to encase it. A thin film of spray solvent is then applied to the surface to make the adhesive a little more spreadable so that any excess can be skimmed off to create a flat and clean seam. The solvent also enables the adhesive to be easily removed from the glass.

“The silicone we used before took over 2.5 hours to skin over and even longer when the ambient temperature was lower. Not only does Teroson outperform the silicone, it skins over in just 20 minutes and is sufficiently hardened for us to move the glazed unit in an hour. This means it can be moved to a crate to cure fully, so we can increase our throughput,” said Boughton.

Protecting the workforce and environment

Another successful application for Henkel has been the use of one of its Teroson black windscreen primers to apply an opaque mask around the edge of the glazed frame to protect upstands from UV light. It also makes the unit more aesthetically pleasing at it effectively hides the mechanism.

After application, the previously-used primer dried to form a very uneven surface but, as the new primer can be roller-applied, it is both smooth and gives a clearly defined edge. Furthermore, it cures in just 20 minutes. The success of this application isn’t judged purely in terms of its efficiency, however. Another big benefit is VOC reduction as the it is free from chlorinated hydrocarbons and aromatic solvents.

Time and component savings

The final Henkel adhesive application is in the assembly of the framework. Cleats made from Zamac and aluminium have, for some time, been bonded into the frame to provide additional strength at points of stress. Although the adhesive Sunsquare had been using was sufficiently strong for the purpose, it was described as being ‘gloopy’. Consequently, it oozed from the joint after application, wasting product and involving additional clean-up time.

To address this issue, Henkel recommended a Loctite acrylic structural bonding adhesive whose thixotropic formulation would not run out of the joint. To ensure it would provide the necessary bond strength it was also subjected to extensive lab testing by Henkel. Indeed, thanks to the strength of the bond, Sunsquare has subsequently been able to dispense with stainless steel straps that were previously needed to support the structure under stress.

“We are saving the cost of the straps as well as minimising adhesive wastage and eliminating clean-up time,” Boughton concluded. “We can’t yet quantify how all our process changes are benefiting Sunsquare but our newly appointed process manager is working on it.”

For a company which has such sharp focus on innovation, optimising production processes is an essential element in funding further research and development of the next generation of rooflights.


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