Determination of composite substrate film The substrate film for compounding must compound the following requirements: 1. The surface of the substrate film should be smooth and flat, with good gloss and transparency, without excessive black and yellow spots, stiffness, no holes, and no wrinkles. 2. The deviation of the thickness of the substrate film should be within the specified standard range. The calculation method is to make a measurement point every 500px across the entire width , measure its maximum thickness and minimum thickness, and then calculate it by the following formula: Average thickness deviation = (average thickness - nominal thickness) ÷ nominal thickness × 100% 3. The surface tension of the composite substrate film must be above 38dyn / cm . The surface tension of various plastic films is shown in Table 1 . Table 1 Surface tension of various plastic films Film type Surface Tension PE 35.6 PP 29.8 PVDC 45.8 PVDC 44.0 PET 43.8 PA 46.5 The surface tension of some materials has reached or exceeded 38dyn / cm , it can be used for dry compounding without corona treatment, but in order to further improve the adhesion of the film to the adhesive, this film is also corona treated. Because the corona treatment can also remove the dust, moisture and other oil dirt adsorbed on the film surface, so that the surface has a good roughness, which can further improve the composite fastness. In addition, the slip agent added in the plastic particles may It migrates to the surface and can be eliminated by corona treatment to improve the adhesion of the adhesive. The quality of the corona treatment can be obtained by dipping the cotton with standard wet reagents and wiping the surface of the film with cotton wool. If the prepared reagents can be evenly distributed on the film and do not shrink within 2s , it will be called water drops It indicates that the film has reached the labeling factor of the reagent, otherwise, the surface tension cannot reach the labeling factor of the reagent. Determination of base film width The base film width is determined based on the following principles: 1. The width of the glue film when compounding is generally 5mm wider than the effective graphics of the slitting and bag making . The purpose is to avoid the delamination of the edge of the glue film after the slitting due to the slight deviation of the glue film. 2. The width of the glue film is generally 5 ~ 10mm longer than the effective length of the glue roller . The purpose is to avoid the deviation of the glue film and make the glue on both ends of the glue roller. The glue glued on the glue roller is transferred to The back of the glue film is then glued to the guide roller and the composite pressure roller in the drying tunnel, and some even cause sticking after rewinding. After solidification or secondary compounding, it cannot be unrolled normally. 3. When the adhesive film passes through the drying tunnel, due to the drying and blowing, the parallelism of the base film and the fluctuation of tension relatively have a certain degree of lateral deviation, at this time the second unwinding film should be 10mm wider than the width of the adhesive film In order to effectively avoid the occurrence of the fault of rewinding and sticking. Of course, due to the different performance of the machine, the fluctuation degree and size of the glue film before compounding are different. Sometimes, increasing the width of the second unwinding film under the circumstances of last resort is also one of the methods to avoid the frequent occurrence of adhesive edge failures. Determination of the glue film Which film to use as the carrier film depends on the structure of the product and the nature of the base film. 1. The laminating film is generally BOPP , BOPA , BOPET , VMPET film with high tensile strength and good thermal stability , while CPP , VMCPP , PE , CPP are prone to elongation under the action of heat, and produce larger Heat shrinkage stress is generally not used as an adhesive film. 2. Aluminum foil is prone to tearing and is generally not used as a carrier film. 3. Due to its strong absorption effect, paper is generally not used as a laminating film. For the dry lamination of paper / AL / PE structure products, only the method of paper gluing can be used. At this time, the amount of gluing can be guaranteed to be more than 4g / ㎡ (depending on the absorption of paper to the glue layer, the purpose is Ensure that the surface is not devoid of glue due to the absorption of paper, and that adhesion cannot occur due to the majority of the amount of glue infiltration), and the machine speed must be opened very slowly to ensure that the solvent absorbed in the paper fiber can fully evaporate. 4, AL PE composite, with a PE glue, but the great extensibility of PE there is inevitably large shrinkage stress after winding, composite products have a lot of wrinkles, tunneling phenomenon. 5, when the BOPET VMPET compound, the carrier film should be done so VMPET, because BOPET film printing, the ink in order to avoid interaction with the binder, while, due to its surface an ink, poor smoothness, the glue requires more many. 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There is a lot of knowledge in the preparation of dry composite base film