In recent years, multi-layer co-extrusion barrier packaging has been widely used in the life and industry, such as food packaging, barrier bottles, cosmetic hose and so on. As the name suggests, multilayer co-extrusion barrier packaging film is composed of multilayer polymer materials, including polyethylene, nylon, ethylene-vinyl alcohol copolymer and other adhesive resins. Most of the above materials are polar materials, but polyethylene is non-polar materials, which means that the two are incompatible and there is no bonding between each other. Therefore, it is necessary to bond the two through polyethylene adhesive resin.
High-performance hot melt adhesive resin can be obtained by mixing polyethylene with other raw materials in a high-speed mixer, then adding a twin screw extruder to melt and extrude, followed by drying, cooling and a series of operations. The multi-layer co-extrusion composite film can be obtained by using the adhesive resin and other polymer materials.
According to experiments, the adhesive resin shows different adhesive strength under the same screw speed and different extrusion temperature. With the increase of temperature, the performance of adhesive resin is greatly improved. After 180 ℃, the adhesive strength increases slowly, and approaches the maximum value at 200 ℃, and then begins to decline. The reason is that the appropriate temperature can activate the reactivity of the anhydride, thus increasing the bonding strength.
In conclusion, the proper increase of screw extrusion temperature is helpful to improve the bonding strength of adhesive resin and enhance the quality of multi-layer co-extrusion barrier packaging film. The extrusion temperature should be controlled above 180 ℃.