November 22nd, 2006 by Team Member

by Jeremy Faludi

Now that we’re using a metal extrusion for most of the main body, we also need to use some glue to stick plastic bits to it (such as the window you see the display through), since there just isn’t enough room in the tiny body for strong snap-fits. This makes recycling harder, for two reasons: first, because now the device is harder to disassemble into its component materials; and second, because now the component materials will have some gunk on them (adhesive residue) that cause problems in recycling the metal or plastic.

Don’t Be Too Strong

Fixing the first problem is fairly simple: you just use weak enough glue (or a small enough amount of strong glue) that whoever disassembles the device can just pop the parts out by hand, overwhelming the strength of the glue. This way, disassembly doesn’t take significantly longer than it would with snap-fit parts. If the glue is too strong, you have to pry things out with a tool, or (if the glue is stronger than the plastic itself) you have to release the glue somehow. Most glues can be released by dissolving them in nasty solvents like acetone, or burning them off in a furnace, but some glues dissolve in water, and other glues melt at low enough temperatures that your plastic parts won’t be affected. The advantage of dissolving or melting your adhesives is that then they can be removed from your parts, avoiding the problem of getting gunk in the recycling furnaces.