Polycarbonate Sheet, Mirrored

Mirrored polycarbonate is a high-optical-quality polycarbonate sheet with a metallised second surface protected by a durable backing coat. It weighs roughly half what a glass mirror of the same size does and it does not shatter, which is why it goes into gyms and locker rooms, schools and childcare, transit and vehicle interiors, retail displays and point of sale, and safety or security mirrors where a glass mirror would be a hazard.

Substrate properties: tensile 9,500 psi ultimate and 9,000 at yield on a 340,000 psi modulus with 110% elongation, flexural 13,500 psi on 345,000, compressive 12,500 psi, shear 10,000 psi ultimate, instrumented impact 47 ft-lb at 0.125 inch, thermal expansion 3.75 x 10^-5 in/in/F, heat deflection 270F at 264 psi and 280F at 66 psi, brittleness temperature minus 200F, specific gravity 1.20.

Two things not published for this product that you might expect: a reflectivity percentage, and a notched Izod or Rockwell hardness figure. No source publishes any of them, so there are no numbers for them here. What matters more in practice is that the mirror coating is the vulnerable part rather than the polycarbonate: clean only the front face and only with mild soap or an ammonia-free cleaner, keep solvents and moisture away from the coated back and the cut edges, and seal or frame the edges in any damp location. Mirrored sheet is also more prone to showing optical distortion than glass if it is mounted on an uneven substrate or clamped too tightly - mount it flat and let it move.

Chemical compatibility and cleaning, which is where most polycarbonate failures start. Clean it with mild diluted dish soap and a soft microfibre cloth, or an ammonia-free glass cleaner. Do NOT use ammoniated glass cleaner - the common blue kind - because ammonia attacks polycarbonate, and the resin maker's own testing shows 0.1% ammonia is enough to do damage in the presence of water. Also avoid abrasive or high-alkaline cleaners, scrapers and squeegees, dry rubbing, and solvent in direct sun. Isopropyl alcohol diluted 50/50 with water handles oil and tar. Acetone, MEK, methylene chloride, chloroform, toluene, xylene and aromatic fuels all attack it, and so do amines and the plasticisers that migrate out of flexible PVC - which is why PVC gasket, tape and cable tie contact is a real failure mode. The important subtlety is that chemical resistance is not a fixed property: stress cracking only develops where the part is in tension, so a cold-bent, over-torqued or tightly framed part will fail with chemicals a compatibility chart calls safe.