Can you use relative density as a parameter?
Many plastics like PVC are relatively dense and will sink in water unless there is entrained air in the sample. This is because their solid density is higher than H2O. OTOH the most of common resins (cheap plastic) - which includes all the polyolefins - will float on water and cannot sink. Obviously, with waste plastic, this parameter is more difficult to implement, due to entrained air, so it would not work without first reducing the resins which are to be tested - to pellets. You can also make the water density significantly higher by adding salt - so that nylon would float and polycarbonate will sink. Both would normally sink. There is a fairly wide spread of density in resins between .9 and 1.4 g/cc (water is 1) but it would only be possible to use this kind of testing on samples which are not aerated. From: fznidar...@aol.com I am still working on my plastic detector. It can't discriminate between #1 and #5 plastic. The #5 plastic produces a rainbow of colors when placed between two linear polarizes. The #1 does not. #1 randomizes the polarization and the light path and becomes clear. The effect is dramatic. I assumed that the colors in #5 came from a rotation of the angle of polarization with frequency. I tried a circular polarizer. It did not, as I had hoped, produce a detectable affect of this rotation. #5 still passes a lot of light in a rainbow of colors. All of the colors go through so that a color cap does not work. Bottles at the dump are a little dirty so that I need a robust detection technique. I need a rainbow of colors detector. I am now stuck. Where to the colors come from? Maybe I am wrong about the rotation of the angle of polarization with frequency. I learned something useful for cold fusion. The #2 milk bottle plastic passes terahertz radiation freely. I used my motion detector light as a sensor for terahertz radiation. #2 will work as terahertz window in cold fusion experiments. Frank Z
