It’s a stretchy situation, isn’t it? Stretch film, that is. It’s not all about the same level of elasticity, either. Several factors can impact how stretchy your film is, and how much it will expand when exposed to different forces or loads. Let’s take a look at some of the most common elements that play into the elasticity of the stretch film.
The six factors that impact the elasticity of a stretch film are:
- Thickness
- Width
- Chemistry
- Stretching method
- Raw materials
- Climate
This article discusses mainly the factors that affect a stretch film’s elasticity. It also teaches you ways to properly store the film to maintain its quality without costing too much.
Definition of Elasticity of Stretch Film
The elasticity of stretch film is commonly understood as its ability to return to its original shape after being stretched. It is a measure of the material’s resilience and strength about how far it can be stretched before breaking. The degree of elasticity depends on the type, thickness, and formulation of the plastic film used in packaging applications. Generally speaking, the higher the tensile strength and elongation properties, the greater the degree of elasticity. This property enables the stretch film to provide an ideal level of tension for stabilizing different types of loads during shipment or storage. Additionally, it also helps reduce product damage caused by shifting or falling off due to inadequate support. As such, it is considered one of the most important characteristics when selecting a stretch film.
By understanding the elasticity of stretch film, it is possible to make informed decisions when choosing the right product for your packaging needs. With the right type of film, you can ensure your cargo is secure and protected during storage, transportation, and delivery.
How to measure the elasticity of a stretch film
Prepare stretch film and marking ruler
Once the stretch film and ruler are ready, it is time to measure the elasticity of the stretch film. To do this, one must first measure a piece of stretch film with a ruler. Mark two points on the stretch film that are 4 inches apart from each other. Next, hold one end of the marked section firmly and pull the other end until it has reached 8 inches in length. Release the film and measure the distance between the two points again to determine the elasticity of the stretch film. The percentage of the increase in length indicates the elasticity of the stretch film. A higher percentage indicates a more elastic material and vice versa.
Stretch the stretch film and make a mark
Using a ruler, measure the distance between the first mark and the second mark. This measurement is referred to as the stretchable distance (SD). The elasticity of a stretch film can be calculated by dividing the SD by the initial length of the stretched material. This yields an elasticity value, which is a measure of how far a material can be stretched before breaking. A higher elasticity value indicates that the material has greater stretching capacity, while a lower elasticity value indicates that the material has limited stretching capacity.
6 Factors Affecting Elasticity of Stretch Film
Thickness
The thickness of the stretch film is one of the most important factors that determine its elasticity. The thinner the film, the higher its degree of elasticity. This is because thin films are more flexible and able to be stretched further without breaking or tearing. Thicker films, on the other hand, are not as pliable and can only stretch to a limited extent before they become brittle and break. Additionally, thicker films also have lower levels of puncture resistance due to their increased rigidity. It is therefore important to consider the desired stretchability of the film when selecting its thickness to ensure it meets the desired application requirement.
Thicker films also have the advantage of providing higher levels of strength and protection for heavier loads. By using a thicker film, you can ensure that the load is held securely and protected from external forces or damage.
Width
Width is a critical factor that affects the elasticity of the stretch film. The width of the film determines the amount of tension applied to it to achieve its desired level of stretch. If the width is too narrow, the film may not be able to reach its full potential for stretch and will break more easily; if it is too wide, the film may be overstretched, making it prone to damage. Generally, wider UV stretch film should be used when greater stretch is required. Additionally, thicker films can withstand higher levels of stretching without breaking than thinner ones. It is important to choose a width that is appropriate for the application to ensure the optimal performance of the stretch film. When selecting the film force and width for your stretch film, it is important to consider factors such as the size of the load, environmental conditions, and handling requirements.
Chemistry
The chemistry of stretch film has a direct impact on its elasticity. The type of material used in the formulation, such as polyethylene or polypropylene, affects the degree of elasticity and overall performance. Additionally, additives are often included in the formula to enhance certain properties like tensile strength and puncture resistance. These additives can also affect the elasticity of the highly stretchable plastic film. In general, films with higher levels of additives tend to be less elastic than those with fewer additives. Furthermore, the film formulation must be properly balanced to achieve the desired elasticity.
Stretching Method
The stretching method is also known as the drawdown process and plays an important role in determining the elasticity of the stretch film. There are three main types of stretching methods: tenter frame, mechanical pre-stretch, and manual hand wrap. The tenter frame uses a pair of heated clamps to stretch the film at a predetermined temperature and tension levels. Mechanical pre-stretch involves using a machine to stretch the film with adjustable tension settings. Manual hand wrapping is done by manually stretching the film around an object and requires manual labor and experience to achieve optimal results. Each method has its advantages and disadvantages, such as speed of application, cost efficiency, and maximum achievable elongation. Ultimately, the stretching method chosen should be based on the desired application and expected performance.
Raw materials:
A.Environmental protection
Environmental protection is an important consideration when evaluating the elasticity of the stretch film. It has been found that non-degradable stretch films can create significant environmental damage if not disposed of properly, as they are composed of a combination of plastics and additives. Additionally, certain production processes may utilize chemicals or other substances that can be detrimental to the environment. As such, it is important to consider the environmental impact of the stretch wrapping, production process, and any substances required for its manufacture when evaluating the elasticity of the stretch film. Additionally, it is highly beneficial to choose stretch films that are composed of biodegradable or renewable materials and produced using processes that minimize their environmental footprint. This will ensure that the materials are better able to break down in natural environments and less likely to negatively affect the environment.
B.The viscosity of the film
The viscosity of the stretch film is a key factor in determining its elasticity. Viscosity is a measure of the resistance to flow or the internal friction of a liquid. The higher the viscosity, the greater the resistance to flow and therefore more difficult for the material to be stretched. Low-viscosity materials are generally more elastic than those with higher viscosity. Viscosity can be impacted by many factors such as temperature, chemicals, and pH. As temperature increases, the molecules become more active and less viscous; thus allowing for greater stretching of the film. In addition, certain chemicals can act to increase or decrease the viscosity of a material based on its composition.
C.Elasticity
The elasticity and stretch film performance is important in ensuring that the wrap holds its tension when applied to a product and does not sag or break. Various factors can affect the elasticity of stretch film, including the quality of raw materials used, the thickness of the film, and the percentage of elastomer present in the formulation. Higher-quality resins will generally generate a more elastic-colored stretch film. Thicker films will be less likely to break under tension, making them well-suited for heavier loads. Increasing the elastomer percentage in a film also increases its elasticity but at the cost of reduced tear resistance and strength. Careful consideration must be taken when using a stretch wrap machine and selecting a stretch film to ensure it meets specific application requirements. When in doubt, consult a stretch film specialist for advice on selecting the right film for your application.
Climate:
A.In summer, its production will reduce its viscosity
The temperature and humidity of the environment also play an important role in determining the elasticity of the stretch film. In high temperatures, its production will reduce viscosity, meaning it becomes less malleable or stiffer. On the other hand, low temperatures can cause it to harden and become brittle, which can compromise its effectiveness when wrapping pallets. Heat, cold, and moisture can all affect the elasticity of stretch film, making it important to consider these environmental factors when selecting a product.
B.In winter, additives should be added
When the temperature drops, so do the elasticity of stretch films. It is important to adjust the formulation by adding additives to maintain this elasticity in colder climates. The most common additives are tackifiers and plasticizers which help improve elongation at break values, allowing linear low-density polyethylene films to perform better in cold temperatures without compromising other properties such as puncture resistance and cling. The combination of the right additives with a film formulation is paramount to achieving optimal performance even in cold temperatures.
How to store stretch film for keeping elasticity
1.Placed in rolls, not folded
It is important to store stretch film carefully to ensure that its elasticity remains intact. Stretch film roll should be rolled, rather than folded when being stored. This will prevent the film from creasing or cracking, which can cause it to lose its elasticity over time. Additionally, make sure that the rolls are stored in a cool, dry place, away from direct sunlight and extreme temperatures. This will help to keep the material durable and elastic for an extended period.
2.Stretch film should avoid sun and rain
Proper storage of stretch film is key to maintaining its elasticity and ensuring it performs its function as intended. It should be stored away from any direct sunlight or rain, preferably in a dry environment with an average temperature of around 75°F (24°C). The roll should also be kept off the ground by storing it on a pallet or shelf. Additionally, the packaging should remain in its original state and not be opened unless it is being used.
3.It is forbidden to be in contact with acid, alkali, and organic solvents
Stretch film should be stored in a cool and dry place, away from direct sunlight or any other sources of intense heat that can cause damage to the material. It is also important to make sure that the storage area is not in contact with any substances such as acids, alkalis, and organic solvents, as these can degrade the elasticity of the pre-stretch film. It is also recommended to store stretch film in its original packaging or other airtight containers to avoid any exposure to dust and other particles that can affect the film’s integrity.
4.Turn it over frequently
It is essential to maintain the elasticity of pre-stretched film to ensure that it performs its intended function properly. To keep the film elastic, it must be stored carefully. One of the most important steps is to turn the roll of stretch film over frequently to avoid creases and wrinkles from forming on one side.
5.The temperature is best between -15℃~40℃
It is important to store stretch film properly to ensure it retains its elasticity. The ideal temperature range for storing stretch film is between -15℃~40℃.
Conclusion
The elasticity of stretch wrap plays an important role in the packaging process, and various factors can affect its performance. The type of polymer used, level of orientation, and elastic recovery properties all play a role in how effective it is for wrapping products. Additionally, the thickness and width of the film will also have an impact on its capacity to hold a given load. Overall, careful consideration must be taken when selecting a stretch film or shrink wrap, to ensure that it meets the needs of the packaging.
