The heat sealing temperature of the composite film is determined by the heat sealing temperature of the heat sealing material, but it should be noted that the heat sealing temperature cannot exceed the heat setting temperature of the printing film, otherwise the heat setting of the biaxially stretched film will be damaged, and the shrinkage of the packaging bag after heat sealing will be caused and wrinkle.
BOPP/CPP bags are excellent in transparency and firm in bags, and are widely used in food packaging. However, the heat setting temperature of BOPP is close to the heat sealing temperature of CPP, and the BOPP film can easily cause wrinkling during heat sealing, and the heat sealing strength is not good, and the heat sealing portion is brittle. Therefore, design should pay attention to the thickness of the BOPP film is close to or greater than the thickness of the CPP, or the vertical layout of the printing and typesetting to the lateral printing layout, to reduce the phenomenon of necking at the transverse seal, you can also use low temperature CPP, to reduce the sealing temperature, Smooth the heat seal area without wrinkling. Destruction often occurs at the weakest place of the composite film after heat sealing. Due to the lack of interlayer composite strength of the composite film, the reinforcing effect of the printing material and the barrier material is lost, so that the heat sealing material alone withstands the destructive tensile force, resulting in the heat seal strength. The greatly reduced damage is more common.
The composite strength of the composite film depends on the choice of the composite substrate and the control of the composite process. When the aluminum-plated PET film is compounded with other materials, the composite strength is low because the adhesion of the aluminum plating layer is too low; the composite strength of BOPP and CPP is also lower because the molecular rigidity of the CPP is larger. Therefore, the choice of composite substrate is more important, but we must also pay attention to the composite surface tension of the film, the adhesive ratio and coating amount, composite temperature, pressure, tension and other technological factors. The effect of printing and typesetting on the quality of heat seals.