Wrap film, also known as stretch film and heat-shrinkable film, is the first PVC winding film produced in China with PVC as the substrate and DOA as plasticizer and self-adhesive. Due to environmental protection problems, high cost (relative to PE ratio, less packing area per unit), poor tensile property and other reasons, PE stretch film was gradually eliminated when domestic production began in 1994 ~ 1995. First, EVA is used as self-adhesive material for PE stretch film, but its cost is high and it has a taste. Later, PIB and VLDPE are developed as self-adhesive materials. Now LLDPE is the main substrate, including C4, C6, C8 and metalcene PE(MPE).

The use form of the winding film:

Sealed packaging; Full width packaging; Manual packaging; Stretch film winding machine packaging; Horizontal mechanical packaging; Paper tube packaging; The packaging of small items; Packaging of pipes and cables; Stretch form of pallet package.

First, start from the bottom of the circle a little bit up, wrapped to the top of the time, the need to wrap the whole top, and finally with scissors will be cut off the packing belt.

Stretch form of pallet package

Stretch film packaging must be stretched, the stretching form of tray machinery packaging has direct stretching and pre-stretching. Pre-stretching is divided into two kinds, one is roller pre-stretching, one is electric stretching.

Direct stretching is completed between the tray and the film. This method has a low tensile strength (about 15%-20%). If the tensile strength exceeds 55%-60%, which exceeds the original yield point of the film, the film width will be reduced, the puncture performance will be lost, and the film will be easily broken. And at 60% of the tensile rate, the tension is also very large, for light goods, is likely to make the goods deformation.

Pre-stretching is done by two rollers. The two rollers are connected together by the gear unit, the stretching rate can be different according to the gear ratio, the tension is generated by the rotary table, because the stretching is generated in a short distance, the friction between the roller and the film is large, so the film width does not shrink, the original piercing performance of the film is also maintained. No stretching occurs during actual winding, reducing breakage due to sharp edges or corners. This pre-stretching can increase the stretching ratio to 110%.

The tensile mechanism of electric prestretching is the same as that of roller prestretching, but the two rollers are driven by electricity, and the stretching is completely independent of the rotation of the tray. Therefore, the adaptability is stronger, light, heavy, irregular goods are applicable, because of the low packing tension, so this method of pre-stretching rate up to 300%, a large section