Shrink wrapping is a particularly well-established form of packaging that has developed over the past four to five decades.

Essentially, material is produced such that molecules are stretched as part of the manufacturing process. When this material is subjected to heat, the elastic memory of the plastic is activated, causing the material to shrink around the product.

This is a traditional division between packaging for transit and packaging for display, whilst the latter has a further division into food and non-food applications.

The key to the application of shrink wrap for transit is cost so that the material and its application provide the lowest cost solution in delivering the product from the manufacturer to the end user.

The conventional definition of a transit wrap involves the use of a sleeve sealer and polyethylene film. An individual or bundled wrap provides the necessary solution of achieving the shipment at the lowest cost.

A typical wrap offers two open sides as a consequence of the use of a sleeve although in certain applications the sleeve may be effectively eliminated by the use of appropriate machinery. Generally, the latter is not a particular requirement.

Polyethylene has the attributes of strength at a certain thickness together with shrink ratios and slip. Accordingly, a user will be able to specify a thickness to provide the necessary pack integrity to the end user and shrink ratios to ensure that the wrap is tight. Slip can be altered to ensure that packs stack appropriately.

There are further benefits of shrink wrap since waste disposal after delivery is relatively insignificant whilst the material has clarity to allow product to be identified. In addition, there are tamper-evidence and moisture-prevention benefits depending on the exact application.

Normal applications involve the collation of products although individual packs are readily benefited from transit wrapping.

The market also offers developments in this area such as coloured and printed films. Polyethylene is not a particularly good medium for product enhancement through printing or pigmentation as it has a naturally soft surface which allows scuffing and dust retention whilst it is also relatively cloudy.

However, polyethylene may frequently offer sufficient optics so that it is acceptable in these applications.

As technology has advanced in this market so have applications crossed over traditional definitions in certain areas.

Consequently, certain transit packs are found using normal display films where the pack and its marketing benefit from the increased investment in a material that offers better optics and machineability.

There are highly specialised display films that are designed to offer the same strength as polyethylene but with far better optics and the marketing benefit is such, in these very specific areas, that the greater film cost can be justified.

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