How much does stretch wrap stretch? Is more better?

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The straightforward answer to the question of how much stretch wrap can extend is that high-quality stretch film can generally stretch to three times its original length or more.

However, the more nuanced answer is that it largely depends on the specific characteristics of the stretch film, the type of wrapping machine being used, and crucially, the nature of the product or loads being wrapped and the goals you aim to achieve.

Let’s delve deeper into the details.

Understanding the Difference Between Stretching and Securing

Often, people mistakenly refer to the material used to wrap pallets as shrink film. While that may be understood colloquially, the accurate term is stretch film, which is intentionally designed to be stretched.

The modern formulations of stretch film are crafted to have high stretchability, but possibly not in the way one might expect.

When Pat Lancaster introduced the first stretch wrapping machine, it utilized a 60-inch roll of plastic developed for dry cleaning purposes. The concept was to apply the film to a rotating pallet, relying on a brake that would decelerate the film, allowing it to stretch slightly and thereby compress the load.

This innovation quickly evolved into the spiral wrap systems widely adopted today. The polyethylene stretch films we rely on now became prominent shortly after.

The process of manually wrapping pallets continues in a similar vein, with personnel using 12 to 18-inch wide rolls of hand stretch film.

It's crucial to note that the security of a load is dictated by the containment force, which is derived from the intensity of the wrap force multiplied by the number of film layers used. Interestingly, the degree of stretch is not a relevant factor.

Cost Implications of Stretching Film

The act of stretching film (more technically referred to as pre-stretching) before it exits the delivery system serves as a cost-saving measure. Pre-stretching has revolutionized the stretch-wrapping technology, making it more accessible and economical for businesses today.

Standard pre-stretch percentages (determined by mechanisms within the wrapper’s pre-stretch carriage) usually vary between 150% to 300%. This means every linear foot of film taken from a roll can represent 2.5 to 4 feet of film utilized on the load.

This results in substantial cost savings! Indeed, many companies initially invest in a pallet wrapper based solely on projected film savings.

Is “More” Truly Better? A Conditional Answer

While more film might seem better, various factors need to be taken into account.

Film characteristics encompass:

• gauge
• chemical formulation
• puncture and tear resistance
• length of the roll
• price per pound

On the other hand, load characteristics include:

• weight
• configuration of the load (uniform cube vs. uneven)
• need for securing the load to the pallet
• whether the product’s dimensions are smaller or larger than the pallet
• the containment force that arises from the combination of wrap force (tension) and the number of revolutions around the load

Optimal film usage can be determined by following these best practices:

1. Set clear standards for loads: identify necessary containment force, establish load-to-pallet bonding requirements, and avoid long or dragging film tails to enhance secure shipment likelihood.
2. Identify key settings: choose appropriate film specifications (quality, gauge, cost) and machine adjustments (pre-stretch ratio, wrap force, layer counts at each end, speed adjustments of the film application, and film overlaps) to meet set standards.
3. Implement a system for feedback to ensure consistent maintenance of standards.

It is essential to understand that utilizing thinner film does not consistently equate to actual savings. Reducing the film thickness may lead to diminished wrap force due to increased breakage occurrences. As pinpointing the exact causes of these breaks is often a complex and labor-intensive task, operators frequently compensate by lowering the wrap force until breaks cease. This results in the necessity of applying additional film layers to recover the lost containment force, ultimately leading to increased film utilization.

Every load has its own optimal containment force requirement rather than a single ideal wrap pattern. For instance, a load might require 10 pounds of containment force; this can be achieved using either a belted thin film with multiple layers or a thicker film with fewer layers. While both methods can yield equivalent containment force outcomes, the wrapping processes and overall efficiency can vary considerably.

Understanding Film Specifications vs. Load Specifications

Most machine films available today can be comfortably pre-stretched up to 300%. However, excessive stretching could contribute to higher break rates at load corners, where tension significantly escalates.

Modern technology enables you to stretch your budget as well as the film itself. Nevertheless, savings gained through down-gauging or exorbitant pre-stretching may lead to product damage when containment forces are negatively impacted due to film adjustments.

Ultimately, companies should ask, “What containment force is essential for the safe transport of my load?” With this insight, industry specialists can devise the right film and machine combination tailored to each specific scenario.

In summary, the degree that stretch wrap can stretch depends on the design capabilities of your machine. Although 300% is a common figure, it might not represent the ideal situation. Striking a balance between robust stretch films applied with significant wrap force and fewer layers versus thinner films wrapped with lower force and multiple layers is crucial.

Curious About Potential Savings from Pre-Stretching Your Stretch Film?

This is an important inquiry. It's a key reason many look into acquiring a new stretch wrapper. We offer a free calculator that estimates potential savings from pre-stretching. You can obtain your copy here.

Remember to take other factors into account. In high-speed wrapping situations, excessive stretching can lead to significant downtime due to film breaks, particularly with inconsistent loads or load corners where machine feeding may need adjustment.

For a useful resource, click here to access the Film Cost Savings Calculator.

Explore These Additional Topics of Interest:

FilmCostCalc

This entry was initially published on June 28, and subsequently updated on November 9.

The extent to which stretch wrap can stretch is dependent on multiple factors, including the specific stretch film, the wrapping machine, and the associated product, loads, and objectives in mind.

Thin plastic film used for sealing food

This article discusses a plastic layer used for short-term food preservation. For a type of plastic wrap frequently used in bulk packaging, see Shrink wrap and Stretch wrap.

Plastic wrap, also known as cling film, Saran wrap, cling wrap, Glad wrap, or food wrap, is a thin plastic material primarily used to seal food items in containers, prolonging their freshness over time. Generally distributed on rolls in boxes with cutting edges, plastic wrap adheres to various smooth surfaces, holding securely over open containers without requiring adhesive. The common thickness of plastic wrap is approximately 0.5 mil (12.7 µm).

Materials Utilized

If you want more information about Stretch Roll Packing Machine, feel free to reach out to us.

Originally, plastic wrap was made from polyvinyl chloride (PVC), which remains a prevalent global component. PVC demonstrates a relatively low permeability to water vapor and oxygen, thereby aiding in food preservation. However, concerns have arisen regarding the transfer of plasticizers from PVC into food.

A more affordable alternative to PVC is low-density polyethylene (LDPE), which tends to be less adhesive, though this can be remedied by incorporating linear low-density polyethylene (LLDPE), enhancing the film’s tensile strength.

In the US and Japan, some brands now produce plastic wrap from polyvinylidene chloride (PVdC), although several, like Saran wrap, have shifted to different formulations due to environmental issues.

Utilization in Food Packaging

Functionality

The primary purpose of plastic wrap in food packaging is to safeguard and preserve food products. It provides a barrier that helps prevent food spoilage, extends longevity, and maintains quality. Plastic wrap offers protection across three dimensions: chemical (acting against gases, moisture, and light), biological (shielding against microorganisms, insects, and animals), and physical (deterring mechanical damage). In addition to protection, plastic wrap reduces food waste, provides tagging for information, simplifies logistical processes, and enhances product visibility and microwavability.

Concerns Regarding Health

While plastic materials are favored in the food sector for their cost-effectiveness and convenience, health risks are stirring concern due to potential chemical leaching from plastics into food items. Various additives, like lubricants, plasticizers, UV-absorbers, colorants, and antioxidants, are included in plastic formulations to enhance their quality and characteristics. Additionally, packages might undergo coatings and printing processes that utilize inks and varnishes. Despite the protective properties of plastics, these substances can penetrate food items, posing health risks.

As Edward Machuga, Ph.D., a consumer safety officer with the FDA's Center for Food Safety and Applied Nutrition, clarifies, while it’s feasible for substances from plastics to leach into food, the FDA assesses both the quantity expected to migrate and the toxicity of the chemical concerned during the approval process. A few notable cases of public concern, such as diethylhexyl adipate (DEHA) and dioxins, have sparked discussion, but there is no solid evidence establishing that these plastics pose significant health hazards when used appropriately.

Environmental Implications

The increasing accumulation of plastic waste poses significant threats to wildlife and broader ecosystems. Plastics littering the environment can entrap and endanger wildlife while also introducing toxic substances into ecosystems. This problem is exacerbated in marine environments, where terrestrial plastics get transported to coastal areas and subsequently dispersed throughout oceans, leading to potential harm to aquatic species. Some marine creatures, such as sea turtles, may mistakenly ingest plastics as food, and this ingestion can pose serious developmental challenges and death.

Employing recycled plastic materials can effectively mitigate environmental impacts, mainly by decreasing the demand for natural gas and oil extraction, transport, and processing. Strategies such as reinforcing plastics with fibrous components can also enhance recyclability. Recent life cycle assessments indicate that incorporating such reinforcements can lead to significant reductions in resource consumption and greenhouse gas emissions.

Application in Medical Fields

Related Topics

Citations

• Media related to cling film can be found on Wikimedia Commons.

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