Blown Stretch Film vs. Cast Stretch Film
Stretch wrap is often used in warehouses for packing. There are two main ways: hand wrapping and machine wrapping. The process is divided into cast film and blown film. Figuring out the difference between them is crucial for film selection. Different scenes to pick the right film. Properties such as tackiness and strength are important. Choosing the wrong film may lead to problems during transportation. This article will make clear the production methods, advantages, and differences between the two types of film. Help you pick the right packaging film.
What is cast stretch film?
Cast stretch wrap is a film produced by the cast extrusion process. The molten polymer is extruded from a seamed die. The shape of the mold determines the thickness and width of the film. The film is then cured on a chill roll and formed into large rolls. The molecular structure of this film is unidirectional. This characteristic gives it a very high stretch ratio. Stretch ratios of up to 360% can be achieved when pre-stretched.
How is cast stretch film made?
Cast stretch film is made by cast extrusion. Resin in granular form is put into a heated screw barrel and allowed to melt. The melted resin is extruded through a slot die into a sheet. This flake is then rapidly cooled and hardened into a film by passing it through a chill roll. The size of the die and the speed at which the film is pulled from the die affect the thickness and width of the stretch wrap. Once the resin is extruded, it is then sent over a chill roll for rapid curing. Tension rolls are used to pull the film to where it is wrapped and cut. When the film is wrapped faster than it is extruded, the film reaches its target thickness. The entire process takes place horizontally.
Advantages of cast stretch film
Cast stretch film is produced using the cast extrusion manufacturing process. There are many advantages. It has good transparency and a glossy appearance. Tear resistance and puncture resistance are also very strong, and they can also prevent moisture very effectively. It also prevents the intrusion of gases and aromas. The film has a uniform thickness. There is also a wide range of thickness options to choose from
The membrane has a wide range of choices. The low noise level when unfolding. It can be adhered to the package for a long time. The production cost is low. Compared with other films, it is thinner, more uniform, and has a high utilization rate with less waste. Prevents load transfer and damage during transportation. It is a cost-effective packaging material.
What is blown stretch film?
Blown stretch film is also a commonly used packaging material. It is blown vertically into bubbles after the resin is heated and then made into rolls. It has a bi-directional molecular structure that locks firmly in place when stretched. It is very strong and has biaxial tear resistance. It is difficult to tear even when wrapping items with sharp edges. It is suitable for wrapping irregularly shaped cartons and relatively short goods. Although it is not as transparent as cast film, it has excellent load-carrying, stretching, and adhesion properties. It is also UV resistance, temperature difference, and moisture-proof. Some additives can also be added in some customized scenes. To achieve anti-fog, anti-slip function. Blown stretch film is also commonly used to wrap pulp, paper, wood, and other construction products.
How is blown stretch film made?
The process of making blown stretch film works like this. Granular resin and additives are first added to a heated screw barrel and melted. Then it is blown through a circular die head to form bubbles. The width of the film bubble can be adjusted at this time by controlling the amount of air blown into the tube. The speed at which the air is blown into the die head determines the thickness of the film. As the film bubble rises, it is slowly cooled using air. However, this results in a blurred and dull appearance of the film. It is then flattened into a tube using nip rollers. Either it is rolled up to make bags and pouches. Or it is cut to make a flat sheet of film. The blown film accounts for about 22%-32% of all stretch film produced on the market today.
Advantages of Blown Stretch Film
Blown stretch film also has many advantages. It has a high tear and puncture resistance and is an effective barrier against moisture, gases, and aromas. It also protects against UV rays. This film is both durable and strong, and it protects items well. The tackiness and puncture resistance are also excellent, making it very popular in the packaging field. The utilization rate is also high and does not produce a lot of waste. And the good adhesion of blown waste also facilitates the reduction of manufacturing waste. With a wide range of uses, it is a popular packaging product.
Main Differences between Casting Film and Blown Film
- Cast stretch film: Fast cooling, clear, and glossy appearance.High puncture and tear strength, moderate tensile resistance.Low noise when unfolding, linear alignment of resin molecular structure.Can be tightly attached to objects for a long time.Medium durability and low cost.Suitable for wrapping irregularly shaped objects, but with slightly lower holding power and durability.
- Blown stretch film: Slow cooling, hazy, and dull appearance. Puncture and tear resistance is also very high. High stretch resistance and noise when unfolding.Random alignment of resin molecular structure and high tackiness.Very good durability, but high production cost.Suitable for wrapping heavy goods and goods with sharp edges.However, low transparency and may be wrapped when packing.Not suitable for high-speed operation.
| Property | Cast Stretch Film | Blown Stretch Film |
|---|---|---|
| Cooling Speed | Fast | Slow |
| Appearance | Clear and glossy | Hazy and dull |
| Puncture/Tear Resistance | High | Very high |
| Stretch Resistance | Moderate | High |
| Unwinding Noise | Low | High |
| Resin Molecular Structure | Linear | Random |
| Cling | Long-term cling | High stickiness |
| Durability | Moderate | Very high |
How to choose?
How to choose stretch wrap? You can look at industry data. Stretch wrap for packaging is highly utilized, but the selection has to be combined with the actual application. Blown stretch film is durable. Excellent tear resistance and puncture resistance, good for sharp and heavy objects; stretch wrap is mostly used for light and pallet stacking products. High transparency and easy-to-scan barcodes. There is no advantage or disadvantage between these two types per se, each has its own application scenario. Comparisons can be made in terms of load capacity, film stretching endurance, etc. If stretching is not important, choose blown film; if transparency is more important, choose cast film.
Stretch Packaging Solutions
With a good choice of packaging materials, the business operation is less stressful. BestYPack specializes in manufacturing stretch wrap, and heavy goods can be wrapped securely. Special shapes can also fit perfectly. It is used in the automotive, medical, construction, and garment industries. High efficiency, good quality, and the cost is still low. It is a very good choice!