How Does Cold Shrink Work?

In this article we explain the similarities and differences of heat shrink and cold shrink and how cold shrink works. We also cover one major drawback to using cold shrink over heat shrink.

Heat Shrink
Heat shrink tubing is tubing that is pre-stretched before you buy it. It retains this stretched diameter and only shrinks when you heat it. Some heat shrink tubing requires higher or lower temperatures than others. For example we have a product that starts to shrink when the temperature rises above 70°C. Regardless of the temperature, as long as it requires heat, it is heat shrink.

Cold Shrink
Cold shrink tubing is also pre-stretched. But the difference is that at the time of stretching it is fitted onto a core – a solid tubing that keeps the diameter fixed. This means it can be put into position, the core then removed and the tubing immediately shrinks (as its inner support has gone).

Cold Shrink Inner Core
What exactly is this inner core? It is a plastic cord or ribbon formed into a spiral to make a tube. One loose end is fed back down the tube and out the opposite end. Then, when you have the cold shrink and its core in place, you pull on the loose end. This causes the core to get shorter as it unravels. At the same time, the cold shrink tube (no longer being stretched by the core) shrinks onto the substrate, which is the item you intend to protect. Eventually you will have completely unravelled the core and removed it, leaving the cold shrink tube fully shrunk onto the substrate.

Similarity:
To sum up then, the similarity is that heat shrink tube and cold shrink tube both shrink snugly onto the substrate to protect it.

Differences:
The difference is that heat shrink tube is supplied as it is and requires a heat gun or other tool to apply heat, whereas cold shrink tube is supplied stretched over a temporary core that has to be removed then discarded. In other words, one needs a heat tool and the other needs a bin for the waste plastic ribbon.
Additionally, cold shrink can be fitted in environments where heat cannot be applied.

History:
Who invented cold shrink technology? This was 3M back in 1968. They have continued to develop this technology and their cold shrink information is freely available on the internet.

Sustainability:
Cold shrink creates more waste plastic. In turn this raises questions of environmental cost and sustainability. This must be offset against the possible gains from using cold shrink in your application.

Our focus, at least for now, is on heat shrink rather than cold shrink. If you’d like to discuss this with us or need advice on heat shrink, please contact us.