Cross-linking in double-bubble plastic film manufacturing

Double-bubble extruded plastic films can be manufactured using special raw materials that can be cross-linked under UV light to enhance their characteristics and performance.

GEW have comprehensive experience of providing engineered UV solutions, usually GEW’s NUVA2 mercury system in such instances, to apply very high dosages of UV energy to correctly expose and cross-link these delicate materials, whilst protecting them from heat damage.

Here, a GEW irradiation unit is installed inline between the extruder where the primary plastic tube is formed and quenched, and the bubble tower where the film is stretched and oriented. 

The flattened primary tube passes through the irradiation unit, which comprises two stacks of UV lampheads mounted against water-cooled rollers to alternately expose and cool both sides of the flattened tube.

Depending on the application and the UV energy dose that needs to be applied, the irradiation stacks can consist of a greater or lesser number of lamps.

To safely contain all UV radiation, the irradiation units are fully enclosed and feature interlocked doors which only allow the lamps to operate when fully closed.

The enclosure also provides thermal protection for the UV lampheads, which often need to operate in ambient temperatures above 50°C. Where the UV irradiators are installed in a high ambient, the lampheads are cooled using GEW’s Positive Purge solution to feed the lamps with cooler air from outside the building.