Heatshrink film for packaging

I'm not sure about the thin films used for packaging, but the heat-shrink tubing used for covering electrical connectors is made by exposing conventional tubing to a high level of radiation from an electron beam tube to crosslink the polymer chains, then the tubing is mechanically stretched to a larger diameter. When heat is applied, the polymer chains become more free to move relative to each other, and the tubing returns (almost) to the diameter locked in at the time of radiation exposure.

Mark, I think the heatshrink film is different stuff?

Those electrical heat-shr>

Heat-shrink films are common food packaging materials. Call companies like DuPont, AbbeonCal, Popper and Sons, etc.

If you need more names, please let me know.

Niles

Any oriented film will shrink when heated. When the film was made, the polymer chains were taken from a random coil state, elongated and then cooled (crystallized) before they could return to the random coil. Upon heating, the mobility of the chains is restored and they then attempt to return to their original, smaller, random coil. On a macroscopic scale, this is seen as shrinkage.

For films, 1 mil = 0.001 inch = 100 gauge.

Most film making knowledge and equipment is proprietary and is not available on the web. Libraries are only a little bit better.

John

And 3M.