Characteristics of 11 Types of Plastic Films

There are several methods for plastic film forming, among which the most commonly used are casting, extrusion, and blown film:

Casting method: It produces a non-stretched and non-oriented flat extruded film through the process of rapid cooling of the melt. The film produced by this method has no obvious orientation structure.

Extrusion method: There are commonly used uniaxial stretching and biaxial stretching methods. The basic principle of biaxial stretching: The polymer raw material is first heated and melted by an extruder to form thick sheets. Then, at a temperature range above the glass transition temperature and below the melting point, the sheets are stretched in both the longitudinal and transverse directions to a certain multiple. This causes the molecular chains to align and arrange in an ordered manner parallel to the plane of the film. Finally, the film is heat-set under tension to fix the oriented large molecular structure. The film is then cooled and processed further to become the final product.

Blown film method: It is usually manufactured by the extrusion blown film method. The material is plasticized and extruded to form a tubular blank, which is then inflated and shaped, and finally cooled, drawn, and wound. Blown films have some orientation. The blown film forming process is simple and is the most widely used film forming process.

Characteristics of 11 types of films:

HDPE

HDPE film, also known as geotextile or impermeable film, has a melting point of approximately 110°C to 130°C and a relative density of 0.918 to 0.965 kg/cm3. It is a highly crystalline, non-polar thermoplastic resin. The appearance of HDPE in its original state is milky white, and it appears semi-transparent on thin sections. It has excellent resistance to high and low temperatures and impact resistance, even at temperatures as low as -40°F. HDPE has excellent chemical stability, rigidity, toughness, mechanical strength, and tear resistance. As the density increases, the mechanical properties, barrier properties, tensile strength, and heat resistance also increase accordingly. It is resistant to corrosion from acids, alkalis, organic solvents, and more. Identification: Mostly opaque, waxy texture, and produces a rustling sound when plastic bags are rubbed or friction occurs.

LDPE

LDPE film has lower density, flexibility, low-temperature resistance, and good impact resistance. It has excellent chemical stability and is generally resistant to acids (except strong oxidizing acids), alkalis, and salts. It also exhibits good electrical insulation properties. LDPE is commonly used for plastic bags and is indicated by the material symbol - number 4. LDPE products are often used in civil engineering and agriculture, such as geotextiles and agricultural films (greenhouse films, mulch films, silage films, etc.). Recycled LDPE can be used to make elastic plastic products such as trash cans, toolboxes, bicycle mats, and garbage carts. Identification: LDPE bags are relatively soft and do not produce a rustling sound when rubbed. LDPE packaging films are soft and easy to tear, while PVC or PP films are brittle and hard.

PP

Non-oriented PP film is produced by the blown film process, which has simple production process and low cost. However, its optical properties are slightly lower than CPP and BOPP films. PP has the characteristic of high-temperature