PC (polycarbonate) sheets are known as the “king of plastics,” but they are also a very temperamental material, primarily due to their extremely high coefficient of thermal expansion.

The Deadly Rule of Expansion and Contraction: The thermal expansion rate of PC sheets is approximately 5 times that of steel and 3 times that of aluminum. If a 2-meter-long sheet is exposed to direct sunlight for 40°C in summer, its length will increase by nearly 6 millimeters. If the diameter of the screw hole and the screw cap are “just right,” when the sheet expands due to heat, there is nowhere for it to stretch. The enormous thermal stress will directly press against the screw, causing the sheet to crack from the center of the hole outwards, or the entire sheet to warp and deform like a wave.

The Correct Installation Logic: The professional approach is “enlarged hole installation.” You must first drill an extra-large hole in the sheet, 3 to 5 millimeters larger than the screw diameter, and then use a large-diameter waterproof gasket and cap for fixing. The screw should only be lightly screwed in; never tighten it completely. The sheet should be able to slide freely within the hole, like wearing a garment that is one size too big.

Choosing the right gasket is also crucial. Gaskets containing EPDM (ethylene propylene diene monomer) must be used. This material is waterproof and does not release chemicals that cause PC to crack, unlike ordinary rubber.

**If you would like to know the advantages of polycarbonate sheets, please kindly check the post [What are advantages of polycarbonate sheets?]