What Is Stretch Film Wrap?

What is Stretch Film Wrap?

Stretch film is a highly stretchable plastic film that can be used to securely wrap around goods. The elastic restoring force keeps the objects tightly together. In contrast, shrink wrap paper is loosely covered around the items and only to shrink tightly as a result from heat.

Stretch film is used in the sales and transportation of various products, and its main function is to stabilize, cover and protect the product.  The shrink film must have high puncture resistance, good shrinkage and a certain shrinking stress. When being stretched, the film should not produce holes.  Since shrink film is often put to outdoor uses, it is usually necessary to add anti-ultraviolet agent.

General specifications of Stretch film

a. Thickness:  15 - 50 microns
b. Width:  5cm - 150cm 
c. Elongation:  200% - 400%  
d. Color:  transparent (other colors can be customized according to customer requirements)

What is stretch wrap film made of

The most common material for stretch wrap film is linear low-density polyethylene or LLDPE, which produces copolymerized ethylene and α-olefins, the most common being butene, hexene and octene. The use of higher alpha-olefins (hexene or octene) can enhance the properties of the stretched film, especially in terms of elongation at break and puncture resistance. Other types of polyethylene and PVC can also be used. Many films have an elongation at break of about 500%, but they can only be stretched to 100-300% in use. After stretching, elastic recovery will be the force to keep the wrapped items tight.

Control of stretch film's adhesiveness

Good stickiness is the key property that makes the stretch wrap film cling securely over the packaged goods and make them a solid and stable whole. There are two main ways to obtain the stickiness of the stretch wrap film: one is to add PIB agent or its masterbatch to the polymer and the other to blend VLDPE in.

(1) PIB (Polyisobutylene) is a translucent viscous liquid and extremely difficult to manipulate in its natural state, direct addition of which requires special equipment or modification to the equipment. Therefore, PIB masterbatch is mostly used instead. There is a process for the transfer of PIB, which usually takes three days. Besides, its stickiness is also affected by temperature. The adhesiveness is strong at high temperature and weakened when the temperature is low. Also, the stickiness is greatly reduced after stretching. The finished film is preferably stored in a certain temperature range (suggested storage temperature is 15℃～25℃). 

(2) Blended with VLDPE (Very low density polyethylene).  Its adhesiveness is slightly poorer, but no special requirements for the equipment to add it. And its adhesiveness is relatively stable, and not limited by time, but also affected by temperature. It is relatively stickier when the temperature is higher than 30°C, and slightly worse when the temperature is lower than 15°C. The desired adhesiveness can be achieved by adjusting the amount of LLDPE in the adhesive layer. This method is mostly used for three-layer co-extrusion.

What is pallet stretch wrap

Pallet stretch wrap or pallet cling wrap is one of the major applications of stretch film. Pallets are used in goods shipping to greatly facilitate the loading and transit of goods.  As each pallet is handled as a unit, stretch wrap is a must to guarantee that all cartons on the pallet hold firmly as one block. You can either hold a pallet wrap handle to wrap pallets manually (as in the below picture) or employ a pallet stretch wrapping machine to automatically wrap the pallets when there's a regularly large quantity.

Some people seem to be confuse stretch wrap with Shrink Wrap Packaging. Although they are similar in terms of packaging and protecting goods, they are quite different!