How Hand Stretch Film is Made
Hand stretch film is produced primarily using the extrusion process, where plastic material is melted and formed into thin films. The key material used in the production of hand stretch film is Linear Low-Density Polyethylene (LLDPE), known for its excellent stretchability, durability, and resistance to punctures. The extrusion process begins with feeding LLDPE pellets into an extruder, which melts the plastic and forces it through a die to form a thin film. The film is then cooled, stretched, and wound onto rolls. This film is used for manual wrapping, providing secure packaging for items on pallets or other products.
The primary focus in hand stretch film production is its ability to stretch significantly (up to 300% of its original length) without breaking, while also offering durability and resistance to tears and punctures. The unique blend of LLDPE material gives the film its desired balance between flexibility and strength.
Differences in Film Production
Cast Extrusion Process
The cast extrusion process is characterized by the way the molten plastic is formed. In this process, the plastic is extruded through a flat die, and the film is immediately cooled by air or chilled rollers. The key features of cast extrusion include:
- Clarity: The film produced through cast extrusion is often clearer and smoother, making it suitable for applications where visibility of the wrapped product is important, such as retail packaging or food products.
- Uniform Thickness: The cooling process in cast extrusion helps achieve a uniform thickness across the film, providing stability and easier handling. This uniformity is ideal for high-volume wrapping and automated packaging lines.
- Lower Stretchability: Cast films generally have lower stretchability compared to blown films, making them suitable for applications like Machine Stretch Film, where uniform thickness and clarity are prioritized in automated wrapping systems.
Blown Extrusion Process
In the blown extrusion process, the molten plastic is extruded through a circular die, where it is inflated into a bubble and cooled in the air. This method results in a film that is thicker and has different properties compared to cast film. Key features of the blown extrusion process include:
- Higher Stretchability: Blown extrusion allows the film to be stretched more extensively, often up to 300% of its original length. This higher stretchability makes the film stronger and more elastic, providing better load stability and strength when wrapping irregular or heavy products.
- Resistance to Punctures: The increased thickness and stronger molecular structure of blown film make it more resistant to punctures and tears, making it a better option for packaging items that may be prone to damage or have rough surfaces.
- Reduced Clarity: While blown films are strong and flexible, they are typically less clear than cast films due to the way the film is inflated and cooled. This can reduce the visibility of the product, which may not be ideal for packaging items that need to be clearly visible to consumers.
Blown extrusion is generally used for applications where strength, stretchability, and puncture resistance are prioritized over film clarity. It is often used for industrial and heavy-duty packaging, such as large or irregularly shaped loads. When combined with VCI Stretch Film, it also provides added corrosion protection for metal items. VCI stretch film releases corrosion inhibitors that form a protective barrier, helping to prevent rust and corrosion during storage or transportation.
Summary of Differences
While both cast and blown extrusion processes use LLDPE material, they result in films with different properties:
- Cast extrusion produces films with better clarity, uniform thickness, and smooth surfaces, making it ideal for visibility-focused applications.
- Blown extrusion produces films that are more stretchable, stronger, and better at resisting punctures, making it suited for more demanding packaging requirements where load stability and strength are important.