25 Sept 2003
Keeping up appearances with a perfect façade
Over the past two decades architects have increasingly created structural designs, particularly for commercial offices and public buildings, which incorporate cladded exterior surfaces. The aim is to achieve a high level of aesthetic appeal and, generally, those that succeed in this objective share one thing in common. They have perfect surfaces. These façades are free from the spoiling affects of rivets, brackets, screws, weld marks and other unsightly mechanical fixings often used to secure two surfaces together.
According to Heiner Pohl, owner of metal forming and processing specialist Christian Pohl GmbH, headquartered in Cologne, Germany: “The solution is neither complex nor unrealistically expensive. In fact, quite the reverse, it’s simple and economic. You replace mechanical fasteners with double-sided adhesive tape.
“This effective quality solution is one in which the company has absolute confidence, built on years of successful applications particularly in the fastening of high grade stainless steel facings and aluminium sub-structure reinforcement.
“One of the first projects to which we applied this technique was a sky scraper on West Wacker Drive in Chicago,” Pohl explains. “That was 12 years ago and involved more than 11,000 m2 of ultra-finished stainless steel window casings. We selected 3M™ VHB™ adhesive tape as the fixing method as it met all of our criteria for bonding strength and ability to handle the weight loading, as well as weathering and ageing performance. Moreover, at that time it had already been used in building and construction applications for about 10 years and had a good track record. Since then 3M VHB™ tape has been a key part of our toolkit,” he says.
Naturally the advantages 3M VHB™ tape offers designers and engineers extend far beyond its potential to deliver aesthetic improvements. Based on an acrylic copolymer construction, 3M VHB™ tape, unlike mechanical fasteners which concentrate stress, provides a continuous bond that distributes stress over an entire surface.
Even compared with adhesive compounds, 3M VHB™ tape delivers important benefits. These include no required curing time and no after treatment of joints and, essential for all large-scale projects, tape can be positioned with reproducible accuracy time after time.
Moreover, in structures such as stainless steel elements mounted on an aluminium sub-structure, 3M VHB™ tape compensates for the differences in the linear thermal expansion of the two materials. This compensation can be up to three times tape thickness, therefore as much as 3.3 mm. For example, at 50°C the linear expansion of aluminium is approximately 1.5 mm/m and that of stainless steel is 0.85 mm/m – 3M VHB™ tape is therefore easily able to absorb the 0.3 mm/m difference without any adverse influence on structural integrity.
Furthermore, 3M VHB™ tape is characterised by high resistance to heat and UV radiation, with some products rated for short-term peak exposure to temperatures up to 260°C, making it ideal for use in the installation of facings continuously exposed to high heat and UV light. One such project undertaken by Christian Pohl’s jointing team was the cladding of the 56-storey Jumeirah Beach Hotel in Dubai, for which 60,000 meters of 3M VHB™ tape were used.
In addition to its heat stability 3M VHB™ tape delivers outstanding strength with adhesive peel resistance of 120 – 450 N/100 mm and tensile sheer resistance between 42 – 69 N/cm2. This mechanical performance is complemented by its resistance to stress, fatigue, vibration, moisture and a range of solvents to ensure long-term structural bonding.
Enabling the broadest application use, 3M VHB™ product technology embraces transparent adhesive film as well as black, white, grey and transparent adhesive tape. These are available in thicknesses from 0.5 mm – 30 mm and widths from 6.00 mm – 1,200 mm.
Transparent products have a particular fit in glass facings and even in the construction of solar cell modules, such as those in the walkway
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Notes for editors
3M is a $16 billion diversified technology company with more than 40 business units, which are organized into six markets: Transportation, Graphics and Safety, Health Care, Industrial, Consumer & Office, Electro & Communications and Specialty Material. 3M Engineered Adhesives Division provides manufacturers with a broad range of innovative bonding, sealing and fastening solutions to help improve the design, assembly and performance of their products.
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