Roping pre-stretched film provides an economical and efficient method to wrap organic products without limiting load stability.
Unitizing pallet loads of product using stretch wrapping film is typically the most efficient and cost-effective way to ensure that product arrives at its destination in the same physical condition as when it was first wrapped. Stretch wrapping pallets is standard practice across many industries, including the shipment of fresh food.
Using pre-stretched film to stretch wrap pallets for transportation provides strength and secure containment, and also protection from the elements.
Most high performance stretch wrapping machines use a powered pre-stretch film carriage that elongates stretch film prior to applying it to the load. This allows the film to exert a tightening force on the load as it tries to return to its original state, stabilizing the load. In most applications, the film is applied as a full web of film that covers and seals all four sides of the load.
Organic products such as fresh-picked fruits and vegetables, however, need to breathe and vent naturally-occurring gases during storage and transportation. This helps preserve their fresh appearance, prevents decay and limits product shriveling and weight loss. These products are commonly packed in vented cases and/or trays, facilitating air flow. Applying a full wrap to these pallets would defeat the purpose of the breathable, vented containers and ultimately speed the rate of product decay.
There are several alternatives to full wrapping which include mesh /netting, vented film, pallet wrapping (clear tape) and roped pre-stretched film. Each provides varying degrees of breathability and load stability. However, only roped stretch film provides the combined benefits of optimum load security, significant cost savings and breathability.
Providing Breathability for Pallet Loads
Fresh products lose their value quickly as their appearance and quality decline, making breathable wrapping of pallet loads to help extend shelf life a profitable investment.
Of the ways to provide breathability, the most practical is by precisely roping the stretch film as it exits the film carriage of the stretch wrapper. This creates an extremely strong and elastic band of film that, when wrapped around the load, creates breathing spaces in the wrap while maintaining load stability. Roping provides cost-effective open airflow through the load while maintaining and often increasing the load stability. Roping the film also increases the overall strength of the stretch film, which can lead to fewer film breaks and an increase in productivity.
Netting one of the alternative methods that allow the pallet load to breathe, is an open work stretch net of plastic similar in overall dimensions to a full wrap film. Most Netting cannot pre stretch as much as conventional machine grade stretch wrap film. Netting is usually applied tightly (using post-stretch/core brake carriages) to secure loads. Using a core brake style carriage to wrap loads uses a considerably larger amount of film. Using post-stretch instead of pre-stretch will also dramatically affect the overall load integrity.
Another significant drawback with netting is that, when removed from a load, it tends to contract into balls and blow around the area. This can potentially become entangled with lift truck wheels, causing costly damage by getting caught up in wheel bearings.
Perforated polyethylene stretch film also provides both the tension of pre-stretched film and easy airflow through perforations cut or punched into the film. The perforations do not usually affect the stretchability of the film but depending on perforation size may reduce the holding power of the film—requiring either the use of more film or a heavier gauge film. Because perforations comprise only a percentage of the film width, the level of breathability is not as high as with roped film that provides more open space for airflow.
The combination of increased film use, handling and recycling handling challenges, and potential loss due to lowered airflow of netting and perforated film can result in a total cost of wrapping significantly more than the cost of comparable standard stretch wrapping film, due primarily to the added operations needed to produce them.
On a cost-per-load basis, netting and perforated film can cost almost four times as much as roped regular pre-stretched wrap film.
A less common alternative is the use of pallet wrapping, applying a clear stretch tape in a pattern that secures a pallet load while allowing airflow. The clear 1½-inch tape does not offer the elasticity of pre-stretched film to exert comparable holding pressure on the load, and the volume of tape required for a load tends to drive up cost.
The technique of roping standard wrapping film has been found to provide superior airflow and load stability while avoiding the potential higher total cost of wrapping with the specialty films and/or tape. Roping standard film further lowers total wrapping cost by allowing use of lighter gauge film than needed for standard pallet wrapping, and by enabling packers to standardize their film inventory.
Where breathability is essential to protecting load value, roping is the preferred method over the alternatives, because it combines maximum breathability with ease of application and removal as well as lowering total pallet load wrapping cost.