POLYFAST & POLYXPAND™ Crest Fixing Fasteners can be used on all kinds of plastic glazing material and especially effective when used as a polycarbonate roofing screw, with its length designed to accommodate the crest height of our ROMA and GRECA profiles.
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.
VULCAN POLYFAST & POLYXPAND™ are designed to work seamlessly with VULCAN Polycarbonate sheets. Consult VULCAN or your local dealer before using any non-conforming accessories. Failure to do so could result in damaging VULCAN Polycarbonate sheets and void warranty.