Questions You Should Know about Stretch Film

*Updated 9-6-17*

SMART WASP Product Page

Stretch film or stretch wrap is a highly stretchable plastic film that is used in packaging and shipping to wrap around items to keep them in place. The elastic recovery of stretch wrap keeps the items tightly bound. In contrast, shrink wrap is applied loosely around an item and shrinks tightly with heat. It is frequently used to unitize pallet loads but also may be used for bundling smaller items.

Here you will find some of the most frequently asked questions about Stretch Film. Be sure to contact us if you have a question that is not answered in this section.

What Is Pre-stretch Film?

Pre-stretched film is made with a process that allows film to be stretched before it is applied. The stretch film is pre-stretched by two rollers. The second roller's rotational speed is quicker than the first, thus stretching the film between them.

How Is Film Pre-stretched?

When film is stretched mechanically between the film carriage rollers due to the gearing ratio and diameter of the rollers. it is pre-stretched.

Why Use Pre-stretch Stretch Film?

• Strength: By stretching the film, the tensile strength of the film increases so that it becomes drastically stronger.
• Film Memory: After the film is stretched it wants to return it to its original form. The more you use this pre-stretching process, the worst the film memory becomes. When the stretch film is applied to a load with no force to load, quickly it will be able to detect that the film has tightened due to its memory as it tries to return to it original size. Stretch film memory is what distinguishes stretch film from other means of packaging unitizing. Settling that can happen during shipment can loosen other methods of unitizing products. Stretch film memory takes up the slack and continues to secure the load during shipment.
• Film Economies: Your cost of stretch film is reduced when it is pre-stretched compared to stretch wrapping a load with film that has not been pre-stretched.
• Stretch Consistencies: Using just hand or machine to add tension to stretch film does not provide uniform stretch and is not able to have reliable performance. This type of stretching can lead to intermittent load failures.

What Is Post Stretch Film?

Post stretch is the stretch in the film created by the film tension between the film carriage and the load being wrapped, which is also known as force to load. In post stretch film, if the film tension is increased, the post stretch will be intensified.

How To Post Stretch?

The amount of film force applied is directly proportional to post stretch. Increase film force and the post stretch will also increase.

Benefits of Post Stretch Film?

Pros: Maximizes load retention of the film.

Cons: This "tension" stretch is generally on the corners of a load, which can cause damage too high.

What Is Film Force? (Film Tension)

The tension created in stretch film due to the films attempt to return to its original state after having been stretched.

Why Have Film Force?

Low film force restrains the film from returning back to its original state.

How To Create Film Force?

• Film Force is formed by creating tension between the load and the film carriage that can be produced both mechanically and electrically.
• Electrically reducing the speed of the film leaving the carriage compared to what the load requires increases the stretch film force which causes the film to stretch between the load and the carriage.
• Mechanically postpones the dancer arm which measures the speed demand of the load will reduce the film feed leaving the carriage which increases the force.

What Is Film Feed?

• Provide the stretch film required to wrap a load while keeping the tension of the film constant.
• The carriage must vary the supply of film with the demand of the load while the load revolves.
• A dancer roller reads the demand of the load.

How To Control Film Feed?

• Using a sensor: the stretch wrappers dancer arm rotates a cam shaft which sends a varying signal to the drive board then it sends varying voltage to the motor.
• The larger the dancer size the larger the output voltage.
• The larger the output voltage means the faster the film is fed.

Cost Reduction

Lowers handling costs: By unitizing products with stretch film you handling costs greatly decrease.

Savings in labor: Handling of individual boxes is more time consuming than handling a unitized load. Another benefit of unitization packaged goods is the amount of man hours saved in the movement and shipment.

Transportation savings: Unitizing packaged goods increases the speed at which they are moved, carrier vehicles spend less time at docks. The time saved also offers valuable cost savings.

Additional Benefits Of Unitizing

Inventory Control: Unitizing products speeds up control of inventory since large unitized loads can be recognized, counted and managed more easily and individual boxes.

Customer Service: Unitizing products and goods for your customers allows them to offload and move goods through their warehouse more efficiently.

• Reduce the risk of pilferage and theft because packages are in a enclosed load and are complicated to remove. The loss of packaged goods is much easier to keep track of if they are shipped out in unit loads rather than individually, which reduces the occurrences of lost or stolen items.
• Minimize plant damage by using stretch film. Stretch Film wrapped goods moved by forklift or pallet jack, are less likely to sustain damage than loose boxes carried by hand. Moving a unitized load in a warehouse reduces the risk of product damage.
• Minimize your shipment damages with the proper use of stretch film. It is less likely in shipping that dense and or heavy items will be packed on top of palletized unit loads. You stand a greater chance of not being damaged because of this.

Should I be using Metallocene? 

• Only if it works and is cost competitive.
• A film labeled Metallocene can have any were from 5% to 100% Metallocene.
• Metallocene can improve some properties and decrease others.
• It depends on how the Metallocene is used and what the other layers consist of. There are a as many different ways to use Metallocene as there are different types of film on the market.
• The bottom line is your concern should be focused on how the film performs in your specific application. Being sold on film composition or structure can be a game of "Smoke & Mirrors".

Should I be using 7 Layer film?

• Only if it works.
• Being 7-layer doesn't mean that the film will perform better in your application.
• Some 7-layer films can use the same material in all 7 layers. It depends on the materials used, the quality of the manufacturing technique and equipment design.
• Once again the concern for the film user should be does the film work day-in-day-out in my application at the lowest possible cost.

Will switching down a gauge save money?

• Every situation is different and you may get more benefit from increasing the gauge.
• Some applications require faster cycle times.
• Some applications are only concerned with cost per roll.
• There are many hidden costs to down gauging:
  • Cycle times- Actually increasing the gauge and decreasing the amount of wraps can increase cycle times and decrease costs per load. Increasing wrapping time per stretch wrapper.
  • Film breaking- Lighter gauge films are more likely to have film breaks, either from machine variations, edge damage during handling or film defects. Automated plants have very low tolerance for any type of film breakage, labor costs must be considered in when choosing gauge of the film.
  • Load integrity- Thorough testing should be completed before considering changing to a lower gauge. Remember the old saying "Do not believe anything you hear and only half of what you see". Load retention can change over time, which will affect your package, either during transit or in your customers' warehouse.

Should I be using one-sided cling films?

• One-sided cling films cover a broad range of slip and cling properties.
• High slip films are usually films that allow the wrapped load to slide against each other, even with a lot of force applied.
• Most one-sided cling stretch films do not have high slip, but will prevent pallets from sticking together. This will satisfy a majority of end users.
• If you require your wrapped pallet or product to slide against other wrapped products than a "High Slip" film would be best for your application.
• If you are only concerned with pallet not sticking together, than a common one-side cling film would work well.
• Most applications do not need two-sided cling films a standard one-side cling film will work well.
• Some stretch wrappers rotate backwards and can put the slip side against the stretch rollers, causing the film not to stretch. And resulting in poor yields.

Do I need a UVI film?

• UVI additives can be expensive.
• If you plan to store the film outside for any length of time, you need a UVI film.
• Most UVI films will last for an average of 3-6 months. It requires high concentrations of UVI to guarantee a film to last 12 months, which can increase the cost significantly.
• A UVI Film that will last 9 months from September to May, could only last 3 months during June, July and August.
• A UVI film that will last 6-9 months in Canada, may only last 3 months in Florida.
• Some UVI's can protect the product, but they have limited use and will only last for a short period of time. The best protection for the product is an opaque film or bag.

How can I decide if my film breaks are caused by the equipment or the film?

• One clue may be the pattern of film breaks, if there seems to be a pattern associated with the breaking it is more than likely is the machine causing the breaking.
• Tearing from the edge could be rough handling of the rolls either during transit or during use.
• Film breaks caused by imperfections tend to be random and not related to any position or timing of the wrapping cycle.
• Breaking occurring in the same place repeatedly on different rolls would indicate a machine problem.
• Even slight changes in machine settings can dramatically affect the performance of the stretch film. For example, small adjustments to the force setting can change the force on the film by 100%, causing damage to the load and film breaks.

What exactly does a properly contained pallet look like?

Are you looking to stretch your knowledge about this particular type of flexible film? Want to wrap up any pending questions you have about this material?

OK, two bad puns right off the bat are a bit much but don't worry, the rest of the article is far better than my comedy skills!

Stretch wraps (which are also known as stretch films) are one of the most popular types of flexible packaging materials on the market. Countless businesses use stretch film to palletize and properly contain loads.

But, which type of stretch film is right for your needs? And what are the answers to the other important questions you need to answer before making a purchase?

This article will present the top 5 questions about stretch film and answer each of those questions completely.

With the information in this article, you will be able to figure out which type of stretch film is right for you and your needs.

What Are The Top 5 Questions About Stretch Film?

Should you wrap your feet in stretch film? Just kidding! Boy, I really shouldn't quit my day job, huh? All right, that's enough of these nonsensical attempts at humor; let's get down to business!

Below, we will explore the top 5 questions about stretch film so that you are armed with the proper knowledge required to buy the correct type of film.

What Is The Difference Between Cast And Blown Stretch Wrap?

Stretch films are generally divided into two categories. These categories include cast stretch film and blown stretch wrap.

Below, you will find an in-depth description of each of these films. With the information therein, you will be able to choose the film that best suits your needs.

Cast Stretch Films

Cast stretch film is created via the application of an extensive manufacturing protocol, most commonly known as cast extrusion.

This process operates through the continual thrusting of a substrate with high thermoplasticity inside of a flat die and onto a cool roll.

The thickness of the film (or gauge) forms as the result of how fast the casting roll draws the plastic from the die.

This operation results in cast films boasting superior transparency, allowing end-users to see the wrapped objects within.

Cast films stretch much easier in part due to the molecules of the substrate being aligned during the extrusion process.

Cast stretch film is notably quiet when being taken off of the roll and stretches with relative ease. It also provides a classic two-sided cling that allows the wrapped product to remain firmly wrapped during shipping.

Although cast stretch film features multiple impressive attributes, including a more affordable price point when compared to blown film, it produces no competition to blown varieties in sustained strength or tear resistance.

Want more information on High-Quality Super Stretch Film Wholesaler? Feel free to contact us.

Cast stretch film will usually stretch with ease. Still, it does not feature as robust a stretch memory as blown film.

Blown Stretch Films

Blown stretch films are literally blown into form through a process known as blown extrusion. This procedure involves the use of plastic melt, which is pushed through a circular slit die. In turn, this results in the formation of a subtle tube.

Next, air is thrust into the tube, which in turn causes the volume of air enclosed to broaden the tube to the desired width.

The tube is then capped with a ring of air that is then blown onto the material to cool.

This operation of cooling the substrate gives blown film an increased strength and notably more flexibility than other wraps.

Key Takeaways On Cast VS Blown Stretch Film

Traditionally, blown film was:

1) softer and more flexible

2) less likely to puncture

3) better in cold temps

4) 5-8% more expensive

However, in regards to modern films available today, blown film is only better in cold temps and applications that produce severe tearing. In today's market, it is almost always more expensive.

How much money will you save with automated stretch wrapping?

Which Type Of Stretch Wrap Is Better, Cast Or Blown Film?

Most of the time, the cast film production process will produce a better-quality stretch film with a more uniform gauge and better cling consistency.

However, blown stretch films offer better tear resistance. So, if you are looking to palletize products that are more likely to tear the film, blown films would be a better choice for your needs.

Can A Thinner Stretch Film Be Stronger Than Higher Gauge Wraps?

While it may come as a surprise, there are some thinner films that are stronger than films with higher gauges. This is due to the ongoing evolution in the technology of film manufacturing.

Because of the advancements in these technologies, new thinner films with multiple layers can achieve greater strengths than traditionally thicker or higher gauge stretch films.

From a sustainability standpoint, these thinner yet stronger film formulations use less plastic, making them a more environmentally friendly choice without sacrificing strength.

Why Do Stretch Film Prices Fluctuate So Often?

Stretch wrap is made of plastic. Plastic flexible films are made from plastic resins. Plastic resin is a petroleum by-product.

Because of this, fluctuations in the oil industry will cause changes to the resin markets, which in turn cause further changes to the cost of stretch wraps.

Usually, the price of plastic resins will change anywhere from 3-9 times per year. These price increases or decreases will be reflected in the cost of stretch films.

However, various global supply chain disruptions will often affect these price fluctuations.

For example, due to the recent conflict in Ukraine, oil and gas prices have been rising quickly. These price increases will likely have an effect on the resin market.

As such, you can expect further fluctuations in stretch film prices as the reverberations of this conflict are felt at the gas pump.

Other global supply chain disruptions may also affect the cost of stretch film as time goes on.

What Is The Best Way To Evaluate The Cost Of Stretch Wrap?

Like BOPP film, stretch wrap is sold by the pound. However, the film is utilized by the foot. While a superior stretch film may cost 15% more, it could provide up to 50% better performance than a standard product.

Because of these dynamics, the roll with a higher price point by the pound may yield significantly more wrapped loads per roll.

The best way to choose the proper film for your applications and budget requirements is to speak one-on-one with a packaging specialist.

They will be able to help you identify which brand, gauge, formulation, and type of film are best suited for your needs.

Which Is The Best Brand Of Stretch Film For You?

With the answers above, you should be able to figure out which type of film is right for palletizing and containing your products.

But which brand of film is the proper choice for your business? Would you like to identify the brand that is right for your packaging applications?

If you answered yes, then you would want to consider reading this follow-up article, The Top 7 Absolute Best Brands of Stretch Film For Shipping Protection.

With the information in this article, you will be able to select the perfect stretch wrap for all of your product palletizing requirements.