Twelve common structural types of packaging film, thoroughly explained

The functional properties of films directly drive the functional development of the packaging industry. Understanding the structure of film materials allows companies to effectively upgrade their packaging.

1 Single-layer film:

Requires transparency, non-toxicity, impermeability, good heat sealing properties, heat and cold resistance, mechanical strength, oil resistance, chemical resistance, and anti-sticking properties. It can be produced by various methods such as extrusion blow molding, extrusion casting, calendering, and solvent casting.

The heat sealing performance of single-layer films is related not only to the relative molecular weight distribution and molecular heterogeneity of the resin, but also to the process conditions during film production, such as temperature, cooling speed, and blow-up ratio.

2 Aluminum foil:

99.5% Electrolytic aluminum with a purity of 99.5%, melted and then pressed into foil using a rolling mill, is an ideal substrate for flexible packaging. It has good gas barrier properties, water vapor barrier properties, light shielding properties, thermal conductivity, and shielding properties.

3 Vacuum-deposited aluminum film:

Under high vacuum, a low-boiling point metal, such as aluminum, is melted and vaporized and deposited on a plastic film on a cooling drum, forming an aluminum-coated film with a good metallic luster. When the aluminum coating reaches a certain thickness, it can greatly improve the oxygen barrier and moisture barrier properties of the substrate. The substrate needs to be corona treated and coated with sol.

4 Silicon coating:

Also known as ceramic coating, its performance does not change under high temperature and humidity, suitable for making high-temperature retort pouches. There are two types of coatings: one is silicon oxide SiOx, the smaller X, the better the barrier properties; the second is Al2O3 。Coating methods include physical vapor deposition and chemical vapor deposition.

5 Coated (dry / wet) composite film:

Single-layer films all have certain advantages, but also inherent disadvantages, often unable to meet multiple packaging performance requirements. Multi-layer composite materials with different substrates can complement each other and give full play to their comprehensive advantages.

6 Extrusion coating composite film:

On an extruder, thermoplastic plastic passes through A T-die and is cast onto a paper, foil, or plastic substrate to be laminated, or with the extruded resin as an intermediate adhesive, another film substrate is pressed together while hot, forming " sandwich ” type composite film.

To improve the lamination strength, corona treatment is required, and an anchor coating agent is applied. Extrusion composite films can be reverse printed, the thickness of each layer can be precisely controlled, the solvent residue is small, and the price is cheap.

7 Co-extrusion composite film:

Using two or three extruders, a common composite die is used to laminate several compatible thermoplastics to produce multi-layer films or sheets. Co-extruded composite films can only be printed on the front side and not on the reverse side.

Compared with dry composite films and extrusion cast films, the thickness control of each layer is more difficult. No adhesives and anchor coating agents are used, resulting in good hygiene and no pollution. Co-extruded composite films have the lowest cost.

8 High barrier film:

It is a multi-layer film. It can effectively prevent the penetration of oxygen and other gases, thereby preventing the growth of microorganisms; preventing the oxidation of the packaged items; and preventing the leakage of the aroma and solvents of the goods.

The commonly referred to high barrier and high strength materials, such as EVAL, PVDC 、 PET 、 PAN 、 selar PA etc., made into packaging films, can significantly extend the shelf life of food, or replace traditional rigid packaging materials with good barrier properties.

9 Preservation and sterilization films:

① Ethylene gas adsorption film. Adding zeolite, clinoptilolite, silicon dioxide, etc. to the film can absorb the ethylene gas exhaled by fruits and vegetables, inhibiting their rapid ripening.

② Anti-condensation and anti-fogging film. The inner surface of the packaging film for many hydro-green fruits often condenses and fogs, easily causing food spoilage. Adding anti-fogging and anti-dripping agents such as monoglyceride stearate, polyol ester fatty acid derivatives, and sorbitan stearate to the film material, and adding fluorinated compounds and other waterproof fogging agents, effectively prevents food spoilage.

③ Antibacterial film. Adding synthetic zeolite with ion exchange function to the plastic material ( SiO2+Al2O3 ), and then adding inorganic fillers containing silver ions, silver sodium ions are exchanged to become silver zeolite, which has antibacterial properties on its surface.

Using co-extrusion composite technology, the film can 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 hydro-green products.

④ Far-infrared preserving film incorporates ceramic fillers into plastic film, enabling it to generate far-infrared rays. This function not only sterilizes but also activates cells in fresh produce, thus providing preservation capabilities.

10 Aseptic packaging film:

Primarily used in the production of aseptic packaging for food and medicine, it requires: sterilization resistance; high barrier properties and strength; good heat and cold resistance (-20℃ without becoming brittle); good puncture and bending resistance; and printing patterns that will not be damaged during high-temperature sterilization or other sterilization methods. Good puncture and bending resistance; printing patterns that will not be damaged during high-temperature sterilization or other sterilization methods.

11 High-temperature retort pouches:

High-temperature retort pouches can be divided into transparent types (shelf life over one year) and non-transparent types (shelf life over two years), high-barrier types and ordinary types. According to the sterilization temperature, they are divided into low-temperature retort pouches ( 100℃, 30min ), medium-temperature retort pouches ( 121℃ ，30min ), and high-temperature retort pouches ( 135℃ ，30min ).

The inner layer material of retort pouches uses various cast and blown PE ( LDPE 、 HDPE 、 MPE ) films, high-temperature cast CPP or blown IPP etc. EVAL aluminum foil, PVDC films are suitable for the middle layer. Biaxially oriented PET nylon 6 etc. are suitable for surface layer materials.

Polyester-type two-component polyurethane acid adhesive is suitable for dry composite film adhesive.

Main advantages of high-temperature retort pouches:

① High-temperature sterilization kills all bacteria, 121℃/30min can kill all Clostridium botulinum;

② Can be stored at room temperature for a long time without refrigeration, can be eaten cold or warm;

③ Packaging materials have good barrier properties, comparable to cans;

④ Can be reverse printed, beautiful printing decoration;

⑤ Waste is easy to incinerate.

12 High-temperature resistant packaging film:

Material melting point above 200℃, suitable for high-strength hard / soft containers.

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