Why Does Shrink Wrapping Film Shrink

Why Does Shrink Wrapping Film Shrink

Let’s just set the scene a little….. you are on your way home a very happy bunny with a copy of the latest game or your favorite band eager to listen or play your little treat for yourself. Once through the door you arrange your supplies a drink a bowl of crisps or even bowl of popcorn at the ready, lights turned down low, it time to open your little package of joy. You try and try...  but slowly this simple operation turns harder and harder until you begin to think that this little bit of heat shrink wrap must be ADULT proof. Be it a shrink wrapped video game, music cd or even a bottle of tablets do they really have to shrink wrap them in plastic so tight in fact shrink wrapping film will form tightly to any size and shape of consumer products. And this can be done with a simple chamber shrink wrapping machine like those from Minipack Torre.

All heat shrink wrapping films are made from one polymer or another so let’s take one molecule of this polymer and look at it before it is for simplicity’s worked or sent through the process of making shrink wrapping film. Basically one molecule of film is like a piece of string that your average cat has played with for a while it looks like a small ball of string. So imagine that you have 1000 single balls of string all in one big mess.

By working the polymers when blowing the pvc or polyolefin into a big bubble all these messy balls of coiled up strings stretch and line up all in order giving you a lovely flat clear material brrrrrrrr lets cool it quickly and behold the molecules stay lined up perfectly straight.

This material can now be made into bags and center folded shrink wrapping film just like we use on our Heat shrink wrap machines (the clue is in the name) such as the semi and fully automatic l sealers and our world beating Minipack Torre chamber machine. So back to the film…. Right if you remember our film is now all stretched out perfectly straight all in line but one thing still on its mind is to get back to that comfy jumbled up mess!. If we apply a heat then these polymers soften and through the force of nature it will retract back to how it was hence shrink in size we call this the films softening point. What these shrink wrap films do is convert the energy from the heat applied into the motion or force required to recoil or retract back to how it was. This is the reason why if used and selected correctly very little heat from the wrapping machine and process transfers into the shrink wrapped product.


Dan packaging machinery have a full range of shrink wrapping machines from Minipack Torre and a fantastic range of center fold shrink wrapping films in PVC and Polyolefin from Darnell so why not visit us at Dan Packaging.


Posted by Steve Holt