Films, as versatile materials, play a crucial role in numerous industries and daily life. Made from polymers like polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and other resins, they exhibit diverse properties and applications. This article aims to provide an overview of various types of films, their characteristics, and their uses.
1. PE Films
Polyethylene films are the most widely used plastic packaging films, accounting for over 40% of total plastic film consumption. Although they may not excel in appearance or strength, PE films offer good toughness, moisture resistance, and heat-sealing properties. Their ease of processing and low cost make them ideal for a wide range of applications, including food packaging, medical packaging, and industrial uses.
2. LDPE and HDPE Films
Low-density polyethylene (LDPE) films are flexible and transparent, non-toxic and odorless, with a thickness typically ranging from 0.02 to 0.1mm. They possess excellent water resistance, drought resistance, and chemical stability, making them suitable for general moisture-proof packaging of food, pharmaceuticals, and daily necessities. High-density polyethylene (HDPE) films, on the other hand, are semi-transparent with a matte appearance. They exhibit superior tensile strength, moisture resistance, heat resistance, oil resistance, and chemical stability compared to LDPE films. HDPE films are commonly used to make shopping bags, trash bags, and various food packaging bags.
3. PP Films
Polypropylene films are classified into unoriented and biaxially oriented films, which differ significantly in performance. Unoriented polypropylene films, including blown polypropylene film (IPP) and cast polypropylene film (CPP), offer better transparency, gloss, moisture resistance, heat resistance, and oil resistance than PE films. They are widely used in food, pharmaceutical, and textile packaging. Biaxially oriented polypropylene (BOPP) films boast improved transparency, gloss, mechanical strength, cold resistance, and reduced moisture and gas permeability. They are often used as a substrate for composite films and in packaging for food, pharmaceuticals, cigarettes, and textiles.
4. PVC Films
Polyvinyl chloride films are divided into soft and rigid types. Soft PVC films, due to their plasticizer odor and migration issues, are generally not used for food packaging. However, soft PVC films produced through internal plasticization can be used for food packaging. Rigid PVC films, also known as PVC cellophane, are transparent, stiff, and tear-resistant, with good gas tightness, aroma retention, and moisture resistance. They are suitable for industrial products and non-food packaging but not for frozen food packaging due to their poor cold resistance.
5. Specialized Films
Specialized films include high-barrier films, such as ethylene-vinyl alcohol (EVAL) and polyvinylidene chloride (PVDC), which effectively prevent the infiltration of oxygen and other gases, thus prolonging the shelf life of food. Antimicrobial films incorporate silver zeolite to kill bacteria on the surface of fruits and vegetables. Ethylene adsorbing films can absorb ethylene gas emitted by fruits and vegetables, inhibiting their over-ripening. Far-infrared preservative films, incorporating ceramic fillers, can kill bacteria and activate cells in fruits and vegetables, preserving their freshness.
6. Composite Films
Composite films are created by combining two or more different substrate materials to enhance overall performance. They can be produced through dry lamination, wet lamination, extrusion coating, or co-extrusion processes. Composite films offer a combination of properties such as gas barrier, moisture resistance, heat resistance, and mechanical strength, making them ideal for a wide range of packaging applications.
In conclusion, films are indispensable materials in modern society, with diverse types, characteristics, and applications. Understanding their properties and uses helps us make informed choices and utilize them more effectively in various fields.
