OT: help identifying a plastic

First, my apologies for a plastic question in a metal group, but this seems to be a knowledgable crowd and likely the best to ask.

I purchased some quarter inch thick plastic sheet from a surplus store. They had it labeled as polystyrene, but I wouldn't trust that. I'm trying to identify it and am having difficulty.

I have gone through identification charts such as one at

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The material is solid (ie not spongy like styrofoam), black, opaque, with a relatively smooth but not glossy surface. It is generally firm, but can be dented slightly on a corner with a firmly pressed fingernail. The sheet flexes but to break it requires pliers and a vise. Then it snaps leaving a rough edge.

It is a thermoplastic. It floats but does not flame like PE or PP is described in the chart, so I hesitate to call it either. Expanded polystyrene also floats but would lead down the wrong path in the chart, so I'm not sure this is a good test.

When subjected to a butane torch there is an orange flame. The material itself never flames or drips. While exposed to the butane flame there is a dense black smoke with an odor perhaps like diesel. It just smells like typical burning plastic to me. Not acidic or rancid, etc.

After being exposed to flame, the burned material is charcoal like, crumbly and leaves a black soot like substance on hands.

It cuts nicely with a table saw as that is how I cut samples.

I tried ABS cement (MEK) and it stuck pieces together enough that they didn't fall apart but a firm pull separated them. There was no welding or fusing of the pieces.

Ultimately I would like to know what this is so I can determine if there is a good adhesive or if I need to use fasteners.

Any assistance is greatly appreciated. Thanks.

Reply to
Al
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Polystyrene has a very distinct metallic sound when you tap it, it's also difficult to saw as it melts and jams the blade. Was there any distinctive smell when you cut it? Martin.

Reply to
Martin Whybrow

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