How Is Crosslinked Shrink Film Made?

Before diving into how it's made, it helps to understand what Crosslinked Shrink Film actually is. Unlike regular shrink film, which simply heats and shrinks around products, this film undergoes a special chemical process called "crosslinking" This process connects polymer chains within the material, enhancing durability and resistance to heat and tears. The result is a more stable, flexible film that performs well under various packaging conditions.

The film is created by exposing plastic to high-energy radiation, causing polymer chains to link together and form a stronger structure. This irradiation improves the durability and shrink performance significantly.

The Base Material: Polyolefin Resins

Most of these films start with polyolefin resins, usually polyethylene or polypropylene. These resins are prized for flexibility and clarity, making them ideal for shrink applications. However, these base materials alone don't have the strength and heat resistance needed for demanding packaging tasks, which is why crosslinking is introduced.

Step 1: Film Extrusion

Production begins by melting polyolefin resin pellets in an extruder. This machine heats the pellets until they melt into a thick liquid, which is then pushed through a die to form a thin sheet or tube of film. This extrusion can be done by the blown film method—where molten plastic inflates into a bubble and cools—or the cast film method—where molten plastic spreads on a chilled roller. The blown film method is often preferred here for strength and clarity.

Step 2: Crosslinking – The Key Difference

Once extruded, the film undergoes the crucial crosslinking process. This step creates chemical bonds between polymer chains, improving mechanical properties. Two common methods are:

Electron Beam Irradiation: High-energy electrons bombard the film, breaking some molecular bonds and creating new ones. This method is chemical-free and offers precise control.

Chemical Crosslinking: Crosslinking agents are added before extrusion, then activated by heating afterward. This can be cost-effective but requires careful chemical handling.

Step 3: Orientation and Cooling

After crosslinking, the film is stretched in one or two directions (monoaxial or biaxial orientation), aligning polymer molecules to boost strength and shrink properties. It's then rapidly cooled to lock in the structure, ensuring uniform thickness and preventing defects.

Step 4: Slitting and Finishing

Finally, the cooled film is wound onto large rolls and slit into various widths to meet customer needs. Additional coatings may be applied to improve slip, anti-fog, or sealing properties, depending on the packaging application.

Why the Manufacturing Process Matters

This manufacturing process directly impacts the film's performance. Crosslinking enhances toughness, puncture resistance, and heat tolerance, which are key to protecting products during shipping and storage. The film's ability to shrink uniformly without brittleness ensures a tight, secure wrap on various shapes.

JTPackage and Quality Assurance

At JTPackage, our crosslinked shrink film is crafted with advanced extrusion and crosslinking technologies to deliver reliable, consistent quality. We carefully control irradiation and orientation to preserve polymer integrity, resulting in films that protect your products efficiently without excess weight or waste.

Understanding how crosslinked shrink film is made helps explain why it's a dependable choice for many packaging needs. The combination of polyolefin resins, advanced extrusion, and precise crosslinking creates its unique strength and flexibility.