Features of commonly used film packaging bags

Film packaging bags are mostly made by heat sealing method, and some are made by bonding method. According to their geometric shape, basically can be divided into three categories: pillow bag, three side sealing bag, four side sealing bag. The bags can also be divided into two categories according to whether they can stand up upright without support: upright bags and non-upright bags.

Pillow bags

Pillow shaped bags, also called back seal bags, bags have after, upper and lower seams, so that they have the shape of a pillow, many small food bags commonly used pillow shaped bags to pack. The back seam of the pillow bag forms a fin-like encapsulation, in which the inner layers of the film are placed together and sealed, and the seam protrudes from the back of the encapsulated bag. Another type of seal is the overlapping seal, in which the inner layer on one side is bonded to the outer layer on the other side to form a flat seal. Fin-shaped seals are widely used because they are relatively strong and as long as the inner layer of the packaging material is heat-sealed. For example: the most common composite membrane bag, the inner layer is PE, the outer layer is a composite substrate. The overlapping sealing is relatively not strong enough, and the inner and outer layers of the bag are required to be heat sealing materials, so it is not used much, but it can save a little from the material. For example: non-composite pure PE bags can be used in this way of packaging. The top seal and bottom seal are bonded by the material of the inner layer of the bag.

Vertical bag

Upright bag, that is, when filled with things, can support the weight upright on the shelf. Vertical bags have ruffled edges that stretch out when something is loaded, allowing the bag to stand up with a relatively flat bottom. They are widely used to package liquid products such as kitchen cleaners, etc., and are increasingly available because they can replace hard packaging materials such as cans and bottles. The design of the upright bag includes a horizontal bottom hem and can be made of two flexible packaging materials. In the other product, only a single film is used, which is folded into an M-shape to form the bottom edge; It can also be designed to fold or fold side instead of bottom flanging to form an overlapping flat sheet bottom. The bags don't stand as firmly as those with a fold at the bottom and are used more for dry goods than liquid products. In both cases, a certain weight of the product pushes the edges of the bag apart, allowing the bag to stand on its own.