Laminating tile façades
A polymer lamination system for ventilated tile façades improves integrity as well as resistance to tearing, water and UV, say researchers in Spain. They add that the film is faster and cheaper to apply than using traditional wet-chemistry methods.
Shaun Parkinson of Dow Chemical Iberica worked with ceramic specialists at the Instituto de Tecnologia Ceramica in Castellon to develop the coating technique. ‘I had heard that when ventilated façades fracture, they can actually fall off a building, because they are held in place at their four corners,’ explains Parkinson. ‘I have done work with lamination films for the glass industry, and I thought we could copy and paste the technology.’
The system uses a vacuum lamination or an inline hot rolling technique to apply a multilayered thermoplastic polymer film to tiles. Researchers have tested low-density polyethylene, an ethyl-acrylic acid copolymer and maleic anhydride grafted polyethylene.
‘A typical construction [of the foil] could be two layers,’ says Parkinson. ‘The acrylic layer would provide adhesion to the ceramic, while behind that would be a thicker layer which could incorporate different properties such as tear, puncture and impact resistance and, to a certain extent, rigidity.’ Additives such as flame retardants could also be included.
This improves on conventional wet-chemistry epoxy films, claims Parkinson, which cannot produce co-extruded layers and have longer curing times. He also believes lamination is more cost effective than wet curing.
The vacuum lamination batch process takes around 30 minutes. It involves laying the film on the ceramic, placing it in a bag with an applied pressure of one bar and heating it in an oven to 160-170ºC.
The group is also working with a ceramic equipment manufacturer to develop a full-scale inline rolling process that would take just seconds to apply. This would involve passing the tile and film under heated rollers to quickly fuse the materials together.
The researchers have conducted tests similar to those used in the glass industry to verify the integrity of the laminated product.
These involved dropping a 46g steel ball from a distance of 63.5cm onto the tile. Parkinson says the tiles performed as well as their epoxy covered counterparts, allowing manufacturers to develop thinner tiles coated in a cheaper way, also reducing material and energy costs.
The laminated coating has shown no degradation to elements such as UV and water. ‘There are enormous possibilities, not only for façades, but for floor tiles, wall tiles and other composite materials.’
Dr Geoff Edgell, Head of Building Technology at the UK advisory organisation CERAM, says, ‘The concept is interesting, however the testing regime is somewhat limited, especially for UK conditions. I would be interested in [the tiles] resistance to freeze-thaw action and weatherability. I would also want to be sure that any of the likely load and environmental effects has no detrimental effect on the bond of the polymer to the substrate’.