How to choose a composite material reasonably is a key step in doing a good job in packaging. At present, the cooking temperature in the market is above 121 ℃ (inclusive), and the high-temperature cooking packaging containing aluminum foil mainly has the following two material structures, namely BOPET/AL/RCPP and BOPET/AL/BOPA/RCPP. The following author will focus on the analysis of these two structures, and discuss with you together, hoping to attract others and help you to do this kind of packaging well. [Aluminum foil packaging bag] BOPET is a high-grade plastic film with excellent performance, which is mainly made of polyester (PET) slices as raw materials after biaxial stretching. It has high transparency, non-toxic and tasteless, and tensile strength. Large, good stiffness, tear resistance, not easy to break, excellent electrical and optical properties, good oxygen barrier and moisture resistance, cold resistance (-70 ° C), heat resistance (200 ° C), and chemical resistance and shrinkage resistance Stable and excellent characteristics. When choosing BOPET, it should be noted that the thermal shrinkage rate is ≤2% in the longitudinal direction and ≤1.5% in the transverse direction under the conditions of 150 ℃ and 30min, and the surface tension should not be less than 45mN/m. Aluminum foil is the only metal foil in flexible packaging materials, and has a long application time in the packaging field. Aluminum foil is a metal material, and its water resistance, gas resistance, light shading, and taste retention are difficult to achieve by any other packaging material, and it is a packaging material that cannot be completely replaced so far. Aluminum foil is made of 99.0%~99.97% pure electrolytic aluminum after repeated calendering. It is rich in resources and has a considerable price-performance ratio. The aluminum foil for retort packaging should be 9 microns thick A-grade soft aluminum foil. BOPA film has high puncture resistance, impact strength, friction strength and bending strength, and has good barrier properties. As the material of the intermediate layer, double-sided corona treatment is requi, and the surface tension is not less than 50mN/m. Some customers use single-sided treated BOPA for compounding. The strength after compounding will be much lower, which will be compensated by increasing the amount of glue on the non-treated surface. The characteristics of RCPP film are transparency, good flatness, good temperature resistance, certain stiffness, flexibility, and good heat sealability. When making RCPP packaging with aluminum foil, it should be noted that the thermal shrinkage rate should not be too large. The selection should take into account the difference in the content of the material, and have a certain pertinence, especially when making some substances containing oil, acid and alkali in the content, more attention should be paid. It is recommended that the thickness of cooking CPP is not less than 80 microns, and a supplier with better physical control should be selected, and corresponding products should be selected for the special requirements of the content. Special attention should be paid to the selection of inks used in vacuum packaging bags and tea packaging bags for cooking and packaging. Two-component polyurethane inks with good temperature resistance should be selected. Curing agents must be added to two-component polyurethane inks. Otherwise, due to the free hydroxyl groups in the inks Part of the curing agent will be consumed, resulting in insufficient curing agent and main agent to react, so that the adhesive layer cannot be fully cu. The lighter ones after cooking are low peel strength and sticking back of the adhesive layer; in severe cases, the ink layer and the aluminum foil will be delaminated, which will affect the appearance and barrier properties of the package.
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