POF Shrink Film, Manufacturing ,Introduction, Classification

POF Shrink Film Manufacturing

POF shrink film manufacturing is the double-bubble blown film process, which is a typical process for producing POF shrink films. A typical POF shrink film is a three-layer co-extrusion film. The two skin layers are polypropylene and the core layer is polyethylene. Typical layer thickness ratios are 15:70:15. Its production process is roughly as follows:

1. The terpolymerized polypropylene and polyethylene enter the extruder for the skin layer and the core layer respectively. After screw plasticization, it enters the annular co-extrusion die.

2. The first bubble of PP/PE/PP three-layer co-extrusion is extruded from the ring die, sized and water-cooled, then flattened and pulled out of the water tank.

3. The first film bubble is heated by infrared rays to soften it properly, and inflated with air to form the second film bubble. During the second bubble inflation process, bidirectional stretching of polyolefin molecules is achieved.

4. After the second bubble is air-cooled, it is flattened and enters the trimming and winding process.

Double Bubble Blown Film Process

Since the double-bubble blown POF shrink film manufacturing process is different from the ordinary blown film process, the requirements for production raw materials are quite special. The surface layer of polypropylene usually uses a copolymerized PP with a lower melting point and a wider melting range, especially a terpolymerized PP, so as to facilitate the expansion and stretching of the second bubble and low-temperature heat sealing. The polyethylene of the core layer is usually linear low density polyethylene to provide second bubble stability and high tear strength.


The Classification of POF Shrink Film

POF shrink film (Polyolefin shrink film), also known as BOPE shrink film (bi-oriented polyethylene film), is a shrink film obtained by bidirectional stretching of polyolefin by double bubble method. Compared with traditional polyethylene blown film, POF shrink film has excellent mechanical properties, good transparency, and uniform vertical and horizontal shrinkage. In general, POF shrink films are divided into two categories, ordinary POF and cross-linked POF.

Ordinary POF heat shrink film

Ordinary POF heat shrink film is currently the mainstream product in most markets. It is mostly a three-layer co-extrusion structure, the two surface layers are polypropylene, and the core layer is linear low-density polyethylene. Compared with traditional PP shrink film and PVC shrink film, its film body is softer, and its tear strength, puncture resistance, and low temperature resistance are also better. Therefore, it has largely replaced the market of PP shrink film and PVC shrink film.

Cross-linked POF heat shrink film

Cross-linked POF heat shrink film is a further upgraded product of ordinary POF shrink film. It is different from the PP/PE/PP co-extrusion structure of ordinary POF film. Cross-linked POF is a pure PE structure. After cross-linking, its physical properties and heat-sealing strength are greatly improved compared with ordinary POF films, and it has better adaptability to packaging machines.