Polythene shrink film is typically thicker, more durable and it behaves differently in the shrinking process when compared with polyolefin film; this means it requires more heat to shrink. In addition, most packs shrink wrapped in polythene tend to be substantially heavier than packs shrink wrapped in polyolefin, so we reflect this in the specification of the shrink tunnel used.
For Polythene applications we always recommend a steel mesh belt complete with an under belt blower and an after pack cooler. We use a steel mesh belt with side chains as this is better on heavy packs compared to the cheaper method of using just a friction drive at the end of the shrink tunnel. This is because whilst a friction drive is acceptable for a lot of packs, the belt over time will stretch and with heavier packs in particular this can lead to the need to change the belt.
Side chains prevent the belt ever stretching and provide a much more positive method of driving the belt. The under belt blower simply blows cool air onto the belt whilst it completes its full cycle. This prevents a critical temperature being reached on the belt, so that there is no possibility of polythene sticking to the belt if it gets too hot.
Their variable speed control provides complete control of production speeds and the adjustable air-flow system helps to achieve the best possible presentation. The double insulated curtains improving consistency and reducing running costs.
Finally the after pack blower cools the pack down immediately after it leaves the heat tunnel. This completes the shrinking process on polythene and ensures that the packs reach maximum handling strength in the shortest possible time. Polythene shrink film reaches full strength once it has cooled.
We have worked with ULMA Packaging, a highly trusted, reliable shrink wrapping machine supplier for over 40 years and are also able to custom modify these machines alongside YPS built machines in order to create automated packaging systems specific for each customer needs or factory format.