1. Significance of plastic soft bag material combination
As the packaging of goods generally divided into transport packing and sales packing, plastic bags is a kind of plastic film as raw materials, used in the production of the packing bag of all kinds of products, widely used in daily life and industrial production, a lot of goods need both outsourcing bags to protect the goods from being damaged in the process of circulation, need more bags for keeping fresh, with good quality, prevent pollution and prevent death, especially like video, flowers, vegetables, aquatic products, cosmetics, etc., to the inner packing must pray treasure goods in a certain period of time not bad, not contaminated, the action of keeping fresh. Plastic flexible packaging belt should ensure the visual effect of product packaging, colleagues should also achieve moisture-proof, sun-proof, gas-proof, mildew proof, long shelf life, easy to use and other purposes. At the same time, consideration should also be given to storage convenience, transport safety and, most importantly, to ensure food safety and hygiene, which is a type of packaging for sale.
Therefore, for the material combination of plastic flexible packaging bags, the varieties, characteristics, functions and thickness of composite packaging materials should be considered first, and then the material combination should be considered, and the theory, shelf life and shelf life of the designed packaging should be estimated. Therefore, the following points should be noted:
1) functional layer material: refers to the shelf life period that can guarantee product quality and content safety. For example, PET and BOPA, which are good barrier materials, AL which prevent from sunlight and PA which prevent oil penetration, etc.
2) strength supporting layer material: generally refers to materials that strengthen resistance to content weight and strengthen protection content, such as EVOH, AL, etc.
3) heat seal layer: generally used in the market, CPP, RCPP, PE and so on can guarantee the heat seal strength.
2. Selection basis of plastic flexible packaging composite materials
1) select suitable packaging materials according to the characteristics and USES of the packaged materials:
2) calculate the moisture permeability coefficient of the composite based on the maximum allowable moisture absorption of the packaging contents; Choose packaging materials according to the maximum allowable barrier (moisture absorption and inhalation) of the object to be packed;
3) calculate the law of microbial reproduction and growth according to the volume (volume) of the packaging, so as to determine its air permeability;
4) there are products that need to be filled with air to inhibit the growth and reproduction of microorganisms, and the oxygen permeation coefficient and carbon dioxide permeability coefficient of composite materials are calculated to determine which film and thickness to use.
5) choose packaging materials according to their safety, storage, transportation shelf life, shelf life and economic benefits;
The outer layer allows food to be separated from oxygen, water vapor, stains, etc., preventing leakage is also a necessary factor in packaging design. Some packages include deoxidizer and nitrogen for extended shelf life. The vacuum packing or the air in the packing bag is also the main food packing method. Keeping food clean, fresh and safe during the shelf-life is the primary function of packaging bags. Secondly, food stored in packaging bags should avoid squeezing, collision, vibration, temperature difference and other phenomena.
1) for example, for rice packaging bags, millet packaging bags and seed packaging bags, if more than 2KG, the handout adopts BOPA/PE or PET/PE. BOPA has strong tensile resistance, high oxygen resistance and soft texture.
2) high-temperature retort packaging bags: halogen egg packaging bags, roast chicken inside packaging bags, roast duck inside packaging bags, chicken leg inside packaging bags and other cooked food inside packaging bags, mostly use BOPA/RCPP, because both BOPA and RCPP have high temperature resistance, BOPA/AL/RCPP can also be used at 121 degrees, 30 minutes of high temperature.
3) chemical packaging bags; PET/BOPA/AL/CPP is mostly used in packaging bags of pesticide and chemical corrosive products, but CPP is still air permeable due to the use of anti-corrosion adhesive compound, which may cause delamination.
Iii. Barrier arrangement of common packaging materials:
1) blocking performance from superior to inferior order: AL>MA-PVDC>EVOH>PVDC>MXD6>PA>PET>PP>PE
2) odor blocking performance: ma-pvdc >PVDC>AL>PET>PA>EVOH>PP>PE
3) chemical resistance: ma-pvdc >PVDC>EVOH>PET>PA>PP>HDPE>LLDPE
4) protective packaging: ma-pvdc >AL>PVDC>EVOH>PA>PET>PP>PE
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