Can't tell what this is anymore.... other than it was plastic. Didn't reach melting point for the reflectors. Found it a while ago surfin the web. Must've been a decent car fire or building fire. The sheeting melted off the sign on the right
I forget the melting point of cast aluminum but I know that poly signals are injection molded at roughly 300 degrees fareinheit. It looks like this melted due to a nearby building fire and the flames are about 2000 degrees. So even at a little distance your still running really hot
At 1500F steel is 90% melted so At 2000F the steel is melted. Plastic will melt at 300F if the setting if right. I can ask my dad who use to work with melting plastic and steel. Now he works with computers.
Metal signals are cast aluminum though. IIRC aluminum melts at a lower temperature than steel since it's less dense (which is why it's much lighter than steel).
I worked in plastic molding and casting for a few years myself. Metal traffic signals are cast in steel dies. The aluminum ingots come to the factories in blocks the size of bricks. The casting furnace is around 1220 degrees. The molten aluminum is ladled into the machine and a hydraulic arm rams it into the molds at 500 tons of pressure. When its cast, it needs to be trimmed.
Plastic signals follow the injection molding procedure and are made of polycarbonate...which is a thermoplastic that chemically is flame retardant. It will melt but it will not catch fire/ignite itself. This is specific to US/Canadian made signals, cant speak for foreign stuff. Poly resin is dumped into a hopper and then melted at roughly 300 degrees into the machine. A screw then drives the molten plastic material into the mold cavity that clamps shut.
When the plastic part is ejected the sprues need to be trimmed off. These are the little dots you see all over plastic parts, they are used to push the parts out of the molds. The polycarbonate plastic signal heads have hardened plastic caused by the screw injector that is also trimmed off leaving a little "scar" on the signal. These marks are found on the back of each housing directly in the center, and on the center of most plastic molded traffic lenses.
That should clear up the molding, melting points, and how these things are cast
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Plastic signals follow the injection molding procedure and are made of polycarbonate...which is a thermoplastic that chemically is flame retardant. It will melt but it will not catch fire/ignite itself. This is specific to US/Canadian made signals, cant speak for foreign stuff. Poly resin is dumped into a hopper and then melted at roughly 300 degrees into the machine. A screw then drives the molten plastic material into the mold cavity that clamps shut.
When the plastic part is ejected the sprues need to be trimmed off. These are the little dots you see all over plastic parts, they are used to push the parts out of the molds. The polycarbonate plastic signal heads have hardened plastic caused by the screw injector that is also trimmed off leaving a little "scar" on the signal. These marks are found on the back of each housing directly in the center, and on the center of most plastic molded traffic lenses.
That should clear up the molding, melting points, and how these things are cast