A summary of the characteristics of 11 types of plastic films used in packaging bags!

Plastic film, as a printing material, is used as packaging after printing bags It has the advantages of being lightweight and transparent, moisture-proof and oxygen-resistant, good airtightness, toughness and fold resistance, smooth surface, ability to protect goods, and ability to reproduce the shape and color of goods. With the development of the petrochemical industry, more and more types of plastic films have emerged. Commonly used plastic films include polyethylene (PE), polyvinyl chloride (PVC), polystyrene （ PS ） polyester film (PET), polypropylene (PP), nylon （ PA ） etc. In addition, there are many other types of plastic films. Shunxingyuan Packaging, a professional flexible packaging manufacturer, believes that it is necessary to understand the characteristics of plastic films before customizing packaging bags, so we have specially compiled the characteristics of 11 types of plastic films for packaging bags for your reference.

1.  Polyvinyl chloride （ PVC ）

PVC film has similar advantages to PET, both are transparent, airtight, and acid and alkali resistant early some food packaging bags used PVC packaging bags 。 However, PVC due to the manufacturing process may release carcinogens due to incomplete polymerization of some monomers, so it is not suitable for packing filling food-grade substances, now it has been replaced with PET packaging bags The material code is No. 3.

2.  Polystyrene （ PS ）

PS film has low water absorption, but good dimensional stability. It can be processed by injection molding, compression molding, extrusion, and thermoforming. Generally, it is divided into foamed and unfoamed types according to whether it has undergone a foaming process. Unfoamed PS is mainly used in due to building materials, toys, stationery, etc. It is also commonly used to make containers for fermented dairy products (such as Yakult, Jianjianmei, Duoduo, etc.), and in recent years it has also been widely used to make due to disposable tableware. The material code is No. 6.

3.  Polypropylene (PP)

Ordinary PP film is made by blow molding, which is simple and low in cost, but its optical properties are slightly lower than CPP and BOPP. The biggest advantage of PP is its high temperature resistance (about -20℃~120℃) and a melting point as high as 167℃, making it suitable for filling soy milk, rice milk, and other products that require steam sterilization. Its hardness is higher than PE, and it is mostly used to manufacture container bottle caps. The material code is No. 5. Identification method: Generally speaking, PP has higher hardness and a brighter surface. When burned, it does not produce a pungent smell, while PE has a heavier candle-like smell.

4.  Polyester film (PET)

Polyester film (PET) is a thermoplastic engineering plastic. It is made into thick sheets by extrusion and then into film material by biaxial stretching. Polyester film is characterized by excellent mechanical properties, high rigidity, hardness and toughness, good puncture resistance, friction resistance, high and low temperature resistance, chemical resistance, oil resistance, airtightness and aroma retention, and is one of the commonly used barrier composite film substrates, but its corona resistance is poor and the price is high. The film thickness is generally 0.12mm, and it is often used as the outer layer material for food packaging bags and has good printability. In plastic products, the material code is No. 1.

5. Nylon （ PA ）

Many types of nylon plastic films (polyamide PA) are currently industrially produced, and the main types used for film production include nylon 6, nylon 12, and nylon 66. Nylon film is a very tough film with good transparency and good gloss. It has excellent tensile strength, elongation strength, high and low temperature resistance, oil resistance, organic solvent resistance, wear resistance, and puncture resistance, and the film is relatively soft, with excellent oxygen barrier properties, but poor water vapor barrier properties, high moisture absorption and permeability, and poor heat sealing properties. Suitable for packaging hard objects such as oily foods, fried foods, vacuum-packed foods, and steamed foods.

6. High-density polyethylene （ HDPE ）

HDPE film is called geomembrane or anti-seepage membrane. Its melting point is about 110℃-130℃, and its relative density is 0.918-0.965kg/cm3. It is a highly crystalline, non-polar thermoplastic resin. The appearance of virgin HDPE is milky white, and it is translucent to a certain extent in a thin section. It has good high and low temperature resistance and impact resistance, even at -40 ℃ low temperatures. Its chemical stability, rigidity, toughness, mechanical strength, and tear strength are excellent, and as the density increases, the mechanical properties, barrier properties, tensile strength, and heat resistance will increase accordingly. It is resistant to corrosion by acids, alkalis, and organic solvents. Identification method: Mostly opaque, waxy to the touch, plastic packaging There is a rustling sound when the bag is squeezed or rubbed.

7.  Low-density polyethylene （ LDPE ）

LDPE film has low density, is soft, has good low-temperature resistance, impact resistance, and chemical stability. Generally, it is resistant to acid (except strong oxidizing acids), alkali, and salt corrosion, and has good electrical insulation properties. LDPE is mostly used in plastic packaging bags, marked with the material symbol No. 4. Its products are widely used in civil engineering and agriculture, such as geomembranes, agricultural films (greenhouse films, ground films, silage films, etc.). Identification method: Plastic bags made of LDPE are softer and do not make a rustling sound when rubbed. Soft and easily torn outer packaging plastic films are LDPE; those that are brittle and hard are PVC or PP films.

8.  Polyvinyl alcohol （ PVA ）

Polyvinyl alcohol (PVA) high-barrier composite film is a film with extremely high barrier properties, made by coating a modified polyvinyl alcohol water-soluble liquid onto a polyethylene plastic substrate. Because polyvinyl alcohol high-barrier composite films have good barrier properties and meet environmental requirements, this type of packaging material has a very bright market outlook and has broad market space in the food industry.

9.  Cast polypropylene film （ CPP ）

Cast polypropylene film (CPP) is a non-oriented, unstretched flat film produced by melt extrusion and rapid cooling. Its characteristics are high production speed and output, good film transparency, gloss, barrier properties, softness, and uniform thickness. It can withstand high-temperature steaming (steaming temperature above 120℃) and low-temperature heat sealing (heat sealing temperature below 125℃), and has excellent overall performance balance. Subsequent processes such as printing and lamination are convenient. It is widely used in the packaging of textiles, food, and daily necessities, as the inner layer substrate for composite packaging, which can extend the shelf life of food and enhance its appearance.

10. Biaxially oriented polypropylene film （ BOPP ）

Biaxially oriented polypropylene film (BOPP) is a transparent flexible packaging material developed in the 1960s. bags 材料， It is made by using a special production line to mix, melt, and blend polypropylene raw materials and functional additives to form a sheet, which is then stretched to form a film. This film not only has the advantages of low density, corrosion resistance, and good heat resistance of the original PP resin, but also has good optical properties, high mechanical strength, abundant raw material sources, excellent printing performance, and can be compounded with paper, PET, and other substrates. It has high clarity and gloss, excellent ink absorption and coating adhesion, high tensile strength, excellent oil barrier properties, and low static electricity characteristics.

11. Aluminum plating

Aluminum-plated film combines the properties of plastic film and metal. The role of aluminum plating on the film surface is to block light and prevent ultraviolet radiation, which extends the shelf life of the contents and improves the brightness of the film. To a certain extent, it replaces aluminum foil and also has the advantages of low price, good appearance, and good barrier properties. Therefore, aluminum-plated film is widely used in composite packaging, mainly used in the packaging of dry and puffed foods such as biscuits, and the outer packaging of pharmaceuticals and cosmetics.

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