Display shrink wrap is traditionally oriented towards non-food point of sale packaging where the principal goal is product enhancement with some limited pack protection through an overall wrap.

The latter is the main distinguishing feature of display packaging, the partial wrap with a sleeve generally found is replaced with a total wrap involving the creation of a two dimensional bag around the product.

Some years ago, the conventional film used for this purpose was PVC – polyvinylchloride with plasticiser; an amorphous crystalline structure.

PVC has largely been replaced by polyolefin shrink film although PVC continues to be offered.

PVC has particular benefits in that it is the easiest of any films to seal and shrink but it suffers from problems on sealing, whilst it also has strength and storage issues.

PVC’s sealing temperature is very close to its degradation temperature at which a number of by-products are created. These include very small quantities of hydrogen chloride gas and carbon deposits on the sealer.

The HCL may be dealt with through ventilation. It is to be stressed that all materials should be used with regard to good manufacturing practice and as a consequence, polyolefin films will also require ventilation in the same way. The by-products of combustion should always be considered in relation to the use of any specific machine operator.

Carbon deposits require regular cleaning whilst the presence of HCL will give rise to a need for regular maintenance of the sealer. As polyolefin’s have no chlorine, this does not arise with their use.

The plasticiser in PVC will harden in cold conditions and soften in hot conditions and this may well cause strength problems in cold weather and equally machineability problems in hot. Again, as polyolefin material has no plasticiser, these are not issues where this film is concerned.

PVC requires storage at normal room temperature failing which it is likely to start to shrink. Polyolefin will tolerate higher storage temperatures.

The overall machineability of PVC still gives this material some market share but, increasingly, polyolefin has dealt with its lower overall machineability whilst offering the benefits noted above so that it is now by some considerable margin, the principal display material.

Display wrapping involves the creation of a two dimensional bag around the product.

This is conventionally performed using an L Sealer with centre folded film. The sealer allows continuous production of wrapped packs that are then processed through a shrink tunnel.

L sealers are found in a variety of forms – manual, semi and fully automatic. A large part of the manual and semi automatic market has been taken by combined seal and shrink machinery. These machines are commonly referred to as chamber machines.

Fully automatic L sealers have found increasing use as their cost and versatility have improved.

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