Heavy-duty bags generally refer to polyethylene bags of 20kg or more, the most common packaging such as 25kg resin raw materials. Due to the large weight of the package, there is a high demand for the performance of the polyethylene film. The film has a wide range of thicknesses, which may range from 130 – 180 microns, depending on the choice of material. The use of higher strength metallocene materials can be made thinner. In addition, the development of multilayer extrusion techniques, such as a five-layer structure, will further enhance the performance of the film. The blown film die size of heavy duty bags is 180 mm, which is relatively small, so it is a challenge for multi-layer extrusion technology.
1.High impact resistance
During the transportation and handling process, the bag will inevitably experience a drop or fall, which requires high impact resistance and can withstand tremendous impact in an instant. The resin having high impact strength is generally a metallocene polyethylene. Generally speaking, the lower the melt index, the lower the density and the higher the impact strength. However, if the density is too low, the film will be too soft and the resistance to denaturation will be poor, so a variety of resins are required to achieve a balance of properties.
2.Strong heat sealing performance
Recycled heavy duty bags are usually packaged in vertical automatic canning lines. Because the filling weight is very large, although there will be a bracket to support the bottom during the packaging process, there is still a certain requirement for the thermal viscosity of the bottom, that is, the ability to bear the weight when the sealing is still hot. Since the heavy-duty packaging bag has a hem, the overlapping area has 4 layers of film, which is relatively thick, so the hem has high requirements for heat sealing, especially after the surface to be printed has been corona treated, the heat sealing performance Will be greatly reduced. In addition, a higher heat seal strength is required to ensure that the seal does not crack during transportation and dropping. Metallocene materials excellent in heat sealing properties are required in terms of resin selection to help improve heat sealability.
3.Strong deformation resistance
At the time of palletizing, the bag below will be subjected to a large amount of gravity. At this time, the film is required to have a good resistance to deformation, so that the excessive stretching does not cause the bag to be thinned or even collapsed.
Generally, the general linear 4-carbon LLDPE, high-pressure LDPE, metallocene material, and low-pressure HDPE are adjusted according to different thicknesses.