Zhejiang Shifang Pipe Industry Co.,Ltd

Zhejiang Shifang Pipe Industry Co.Ltd is one of the most professional manufacturer and exporter of roof drainage system..

Features of commonly used film packaging bags
- Aug 20, 2018 -

Thin film packaging bags are mostly made by heat sealing method, and also made by bonding method. According to their geometry, they can be basically divided into three categories: pillow-shaped bags, three-side sealed bags, four-side sealed bags. It can also be divided into two categories according to whether the bag can stand upright without support: upright and non-upright bags.

Pillow Pouch

Pillow bags, also known as backpack bags, have seams at the back, top and bottom, making them pillow-shaped, many small food bags are often packed in pillow-shaped bags. The back seam of the pillow-shaped bag forms a fin-like package in which the film inner layer is sealed together and the seam protrudes from the back of the packed bag. Another type of seal overlaps the seal, where the inner layer of one side is bonded to the outer layer of the other side to form a flat seal. Because the fin seal is relatively strong, and as long as the inner packaging material is heat-sealed, so widely used. For example, the most common composite membrane bag is PE, and the outer layer is composite substrate. The overlapping seal is relatively not strong enough, and requires the bag's inner and outer layers are heat-sealing materials, so the use of not much, but from the material can be saved. For example, non complex pure PE bags can be packaged in this way. The top seal and bottom seal are bonded to the inner layer of the bag.

Three side pockets

Three side sealing pockets, that is, there are two side joints and one top side seam on the bag. The bottom edge of the bag is formed by a horizontal folding film, and all the seals are made by bonding the inner layer of the film. This kind of bag can be folded or not. When there are hem, they can stand upright on the shelf. A kind of deformation of the three-side sealing pocket is to fold the bottom edge of the original, and realize it by gluing. Thus, it becomes a four-side sealing pocket.

Quadrilateral pocket

The four side sealed pocket is usually made of two materials, which are sealed on the top, sides and bottom edges. Compared with the bags mentioned earlier, it is possible to use two different kinds of plastic resin materials, if they can be bonded to each other, to make a front bonded four-sided sealed bag. The four side sealed pocket can be made into various shapes, such as heart-shaped or oval.

Erect bag

A vertical bag, that is, when it is filled with something, can support the weight to stand upright on the shelf. The upright bag has a folded edge that will spread when something is loaded so that the bag has a relatively flat bottom to stand up. They are widely used to pack liquid products such as kitchen cleaners, because they can replace hard packaging materials such as cans and bottles, so the market and demand is increasing. The design of the erect sack contains a horizontal bottom hem, which can be made of two soft packaging materials. In another product, only one film is used, and the film is folded into a M shape to form a bottom edge; it can also be designed to fold or fold the side edge without the bottom edge, forming an overlapping flat sheet bottom. This bag is not as strong as the bottom folded bag, and it is used for dry goods rather than liquid products. In both cases, a certain product weight folds the edges of the bag open so that the bag can stand on its own.

Large volume bag and high strength bag

It is usually used to pack bulk products with a load of up to 5000kg. This bag has high tensile strength and can be used for both liquid products (such as container liquid bag film introduced in the previous section) and solid products. The bag can be made of HDPE, PVC and polyester fibers, but the most commonly used material is made of flat PP yarn. The bags used for woven bags and liquid products usually contain PE film as the inner liner. When required for better barrier performance, aluminum foil or PVDC copolymer can be used. For waterproof purposes, PVC or rubber material can be used to coat the bag. According to the material and application characteristics, the seal of the bag can be heated or sewn. Usually large-volume bags are filled from the top, discharged from the bottom, can also be fitted with nozzles or other diversion devices, or opened with a simple rough cut. For open-air bags, ultraviolet stabilizers should be added to the resin ingredients to prevent the bags from aging prematurely and reducing their strength.