POLYFAST – CREST FIXING 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 Screw
VULCAN Plastics, in collaboration with BDN Fasteners, has come up with PolyFast, a polycarbonate roofing screw with a hassle-free, fail-safe design, and literally the easiest to use skylight fixing fastener on the market.
PolyFast Crest Fixing Fasteners can be used on all kinds of plastic glazing material and are especially effective when used as polycarbonate roofing screws, with its length designed to accommodate the crest height of VULCAN ROMA and GRECA profiles.
The attached round cutting saw creates a much-required 10mm diameter thermal expansion hole on plastic roofing materials which then securely fastens onto the purlin underneath in one-go.
A large domed BAZ washer completes the package, covering the expansion hole while providing superior strength against high winds.
*Note that because water, along with other liquids flows to the lowest point, PolyFast Crest Fixing Fasteners have to be fixed at the crest on roofing sheets.