This article introduces the performance and advantages of twelve types of flexible packaging materials, covering almost all types of structure in the flexible packaging industry.
1. Single-layer film
It is required to be transparent, non-toxic, impermeable, have good heat-sealing bag-making properties, heat and cold resistance, mechanical strength, grease resistance, chemical resistance, and anti-blocking properties. It can be produced by various methods such as extrusion blown film method, extrusion casting method, calendering method and solvent casting method.
The heat sealing performance of the single-layer film is not only related to the relative molecular mass distribution and molecular disproportionation of the resin, but also related to the process conditions at the time of film formation, such as temperature, cooling rate, and inflation ratio.
2. Aluminum foil
99.5% purity electrolytic aluminum is melted and pressed into a foil with a calender, which is ideal for flexible plastic packaging. It has good gas barrier, water vapor barrier, shading, thermal conductivity and shielding properties.
3. Vacuum evaporated aluminum film
Under high vacuum, low-boiling metals, such as aluminum, are melted and vaporized and deposited on the plastic film on the cooling drum to form an aluminum-plated film with good metallic luster . The thickness of aluminum plating meets certain requirements, which can greatly improve the oxygen resistance and moisture resistance of the substrate. The substrate is corona treated and coated with sol.
4. Silicon coating
Also known as ceramic coating, no matter how high the temperature and humidity, the performance will not change, suitable for making high temperature cooking bags. There are two kinds of coatings: one is silicon oxide SiOx, the smaller the X , the better the barrier property; the second is Al2O3 . Coating methods include physical vapor deposition and chemical vapor deposition.
5. Glue (dry / wet) composite film
Single-layer films have certain advantages and inherent shortcomings. It is often difficult to meet multiple packaging performance requirements. Multiple layers of different substrates are compounded, that is, they can learn from each other's strengths and play their comprehensive advantages.
6. Extrusion coated composite film
On an extruder, the thermoplastic plastic is cast on the paper, foil, plastic substrate to be coated through a T -die, or the extruded resin is used as the intermediate adhesive, and the other film base is heated while hot The materials are pressed together to form a " sandwich " type composite film .
In order to improve the compound fastness, corona treatment is required and anchor coating agent is applied. The extruded composite film can be reverse printed, the thickness of each layer can be accurately controlled, the amount of residual solvent is small, and the price is cheap.
7. Co-extruded composite film
Use two or three extruders, share a composite die, and laminate between several compatible thermoplastics to produce multilayer films or sheets. The co-extruded composite film can only be printed on the front side and not reversed. Compared with dry composite film and extruded cast film, the thickness control of each layer is more difficult. No adhesives and anchor coating agents are used, and no pollution and good hygiene. Coextruded composite film has the lowest cost.
8. High barrier film
The high barrier film is a film with a multilayer structure. This kind of film can effectively prevent the infiltration of oxygen and other gases, thereby causing the reproduction of microorganisms; prevent the wrapped articles from oxidizing; and prevent the outflow of the fragrance and solvent of the goods.
The so-called high-barrier high-strength materials, such as EVAL , PVDC , PET , PAN , selar PA, etc., are made into packaging films, which can significantly extend the shelf life of food, or can replace traditional rigid packaging materials with good barrier properties.
9. Fresh-keeping and sterilization film
â‘ Ethylene gas adsorption membrane, adding zeolite, cristobalite, silica and other substances to the membrane can absorb the ethylene gas exhaled by fruits and vegetables and inhibit its maturity.
â‘¡ Anti-condensation and fogging film, the inner surface of the packaging film of juicy green fruit is more condensed and fogged, which is easy to cause mildew in food. Adding anti-fog and anti-dripping agents such as stearic acid monoglyceride, polyalcohol fatty acid derivatives, sorbitan stearate, etc. to the film material, and adding water-resistant fog agents such as fluorine compounds can effectively prevent food mildew .
③ Antibacterial membrane, synthetic zeolite ( SiO2 + Al2O3 ) with ion exchange function is added to the plastic material , and then the inorganic filler containing silver ions is added, and silver sodium ion exchange becomes silver zeolite, and its surface has antibacterial properties. The co-extrusion composite process can make the film have a 6μm silver zeolite inner layer. When the silver ion concentration reaches 10-50ppm , it can completely kill the bacteria on the surface of the green fruit.
â‘£The far-infrared preservation film is mixed with ceramic filler in the plastic film, so that this kind of film has the function of generating far-infrared rays, which can not only sterilize, but also activate the cells in the green fruit, so it has the preservation function.
 10. Aseptic packaging film
Mainly used in the production of food and pharmaceutical aseptic packaging, it requires: sterilization resistance; high barrier and strength; good heat resistance and cold resistance ( not brittle at -20 ℃ ); good needle resistance and bending resistance The printed pattern will not be damaged in high-temperature sterilization or other sterilization methods.
 11. High temperature resistant cooking bag
High-temperature cooking bags can be divided into transparent type (shelf life of more than one year) and non-transparent type (shelf life of more than two years), high barrier type and ordinary type. According to the sterilization temperature, it is divided into low-temperature cooking bags ( 100 ° C , 30min ), medium-temperature cooking bags ( 121 ° C , 30min ), and high-temperature cooking bags ( 135 ° C , 30min ).
The inner material of the cooking bag is made of various casting and inflation PE ( LDPE , HDPE , MPE ) films, high temperature resistant casting CPP or inflation IPP, etc. EVAL , aluminum foil, and PVDC film are suitable as intermediate layers. Biaxially stretched PET , nylon 6, etc. are suitable for surface layer materials. Polyester two-component polyurethane acid adhesive is suitable for dry composite film adhesive.
 Main advantages of high temperature cooking bags:
①High temperature cooking can kill all bacteria, 121 ℃ / 30min can kill all botulinum; ②Can be stored at room temperature for a long time, no need to refrigerate, can be cold or warm food; ③The packaging material has good barrier properties, no less than Canned food; ④Can be reverse printed, beautiful printing and decoration; ⑤Waste is easy to incinerate.
 12. High temperature resistant packaging film
The melting point of the material is above 200 ℃ , suitable for high-strength hard / soft containers.
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