POLY-FAST™ – CREST FIXING Polycarbonate Roofing Screws & Fasteners
Introducing POLY-FAST™ polycarbonate roofing screws & fasteners. Due to the high Coefficient of Linear Thermal Expansion (CLTE) of polycarbonate, 65~70 x 10–6 m/k, the rate of expansion due to thermal changes must be considered when calculating the size required, and enough room must be left for these changes during installation.
A 3-meter-long sheet of polycarbonate for example will expand by approximately 2.1mm for each 10°C temperature increase. A 5-meter-long sheet restrained at one end by being butted up against a brick wall can have its free end move by over 10mm in the course of a day with a 30°C temperature rise.
Before the introduction of fasteners dedicated to fixing thermoplastics, and when metal-fixing hex washer screws were still used, fixing any plastic sheets required at least 2 steps. First, pre-drilling an expansion hole that is approx. 2 times the diameter of the screw using a standard drill bit, which is followed by screwing down the metal roofing screw.
More often than not, builders will skip the first step and drill through the metal roofing screw directly, which is like a ticking time bomb waiting to explode, because sooner or later, the sheets are bound to deform, craze, crack, and break all the way through.
The Advantages of VULCAN Polycarbonate Roofing Screws
VULCAN Plastics, in collaboration with BDN Fasteners, has come up with POLY-FAST™, a polycarbonate roofing screw with a hassle-free, fail-safe design, and literally the easiest to use skylight fixing fastener on the market.
POLY-FAST™ Crest Fixing Fasteners can be used on all kinds of plastic glazing material and are especially effective when used as polycarbonate roofing screws, with their length designed to accommodate the crest height of VULCAN ROMA and GRECA profiles.
A nominal 11mm diameter hole is created by the Thermal Expansion Hole Cutter during the process. When mated with the Thermal Expansion Hole Cutter, with the Depth Stop Knurls acts as a stopper, the height at where it stops upon coming in contact with the purlins; enough so that it prevents screw over-run or over-drive,provide a perfect seal to the enlarged hole, but not deform the corrugations.
A large Domed Weatherseal EPDM washer with two concentric sealing rims on the washer underside completes the package, covering the expansion hole while providing superior strength against high winds.
*Note that because water, and other liquids flows to the lowest point, POLY-FAST™ Crest Fixing Fasteners have to be fixed at the corrugation crest on roofing sheets.