Comprehensive Summary of 11 Types of Plastic Films for Packaging Bags (Part 1)

Plastic films, as a printing material, are used in packaging bags due to their lightweight, transparency, moisture resistance, oxygen barrier properties, durability, smooth surface, and ability to protect goods while showcasing their shape and colors. With the advancement of the petrochemical industry, there's a wide variety of plastic films available, including Polyethylene (PE), Polyvinyl Chloride (PVC), Polystyrene (PS), Polyester Film (PET), Polypropylene (PP), Nylon (PA), and many others. Understanding the characteristics of these films is crucial for custom packaging bag manufacturing.

1. Polyvinyl Chloride (PVC): PVC films share similarities with PET in terms of transparency, impermeability, and resistance to acids and alkalis. Early packaging bags for many food products were made from PVC. However, PVC's production process can release carcinogens due to incomplete monomer polymerization, making it unsuitable for food-grade materials. PET packaging bags are now preferred over PVC, identified by the material code "3."

2. Polystyrene (PS): PS films have low water absorption but good dimensional stability, making them suitable for injection molding, compression molding, extrusion, and thermoforming processes. They are used in construction materials, toys, stationery, and can also be seen in packaging fermented dairy products like yogurt and lactobacillus drinks. PS is categorized as "6."

3. Polypropylene (PP): PP films are commonly produced through blow molding, offering a simple process and low cost. However, their optical properties are slightly lower than CPP and BOPP films. PP's notable feature is its high temperature resistance (approximately -20°C to 120°C), with a melting point of up to 167°C, making it suitable for products like soy milk and rice milk that require steam sterilization. PP is marked as "5" and can be distinguished by its high hardness, glossy surface, and lack of irritating odor when burned compared to PE.

4. Polyester Film (PET): PET is a thermoplastic engineering plastic produced by extrusion into thick sheets and then stretched biaxially into thin films. It offers excellent mechanical properties, high rigidity, hardness, toughness, puncture resistance, friction resistance, temperature resistance, chemical resistance, oil resistance, gas barrier properties, and aroma retention. PET is commonly used as the outer layer material for food packaging bags due to its good printability and is labeled as "1."

5. Nylon (PA): Nylon plastic films (Polyamide PA) come in various industrial varieties, including Nylon 6, Nylon 12, and Nylon 66, used to produce films. Nylon films are tough, transparent, glossy, and have good tensile strength, high/low-temperature resistance, oil resistance, solvent resistance, abrasion resistance, and puncture resistance. However, they have poor water vapor barrier properties, high moisture absorption, and poor heat sealing properties. They are suitable for packaging rigid items like oily foods, fried foods, vacuum-packaged foods, and steamed foods.

Understanding the properties of these plastic films is essential for choosing the right material for packaging bags based on specific product requirements and safety considerations. In part two of this series, we will explore more types of plastic films commonly used in packaging bags.