Polycarbonate Sheet, Flame Inhibited

Flame-inhibited polycarbonate sheet is the high flame-rating grade: UL 94 V-0 at 0.060 inch and 5VA at 0.118 inch, and it passes FAR 25.853 paragraph 1a(i) at 60 seconds and 1a(ii) at 12 seconds between 0.060 and 0.125 inch. Light transmission is 86% for clear at 0.118 inch. That V-0 at 0.060 inch is the point of the grade - plain polycarbonate sheet is only HB at that gauge and does not reach V-0 until around 0.394 inch.

Two things that come with the flame-retardant package and are almost never mentioned. Notched Izod falls to 2 ft-lb/in, from 12 to 18 for plain sheet - about an 88% loss - so this grade is not the tough one. Unnotched Izod still does not break and instrumented impact is still 46 ft-lb, so for a flat glazing impact it behaves well; for a notched, edge-loaded or fastened-through part it does not. And specific gravity is 1.25 rather than 1.20, so it is about 4% heavier than plain sheet - the shipping weight on these listings accounts for that.

The other thing to know is that this grade is NOT UV stabilised. It is an interior and electrical product - enclosures, barriers, light covers, transit and aircraft interiors, electrical panels. If the panel goes outdoors you want the UV-stabilised flame-retardant grade instead, and getting those two the wrong way round is a warranty claim.

Other properties: tensile 9,500 psi ultimate and 9,000 at yield on a 340,000 psi modulus, flexural 13,500 psi, compressive 12,500 psi, heat deflection 270F at 264 psi and 280F at 66 psi, water absorption 0.15%.

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.