What is the manufacturing process of calendered PVC shrink film and the calendering technology used?

The manufacturing process of calendered PVC shrink film includes the following steps:

Mixing: Polyvinyl chloride (PVC) resin is mixed with plasticizers, stabilizers, colorants and other additives in a high-speed mixer. The mixture forms a compound that can be used for processing.

Extrusion: The compound is then fed into an extruder, where it is melted and homogenized. Molten PVC is forced through a mold to form a flat sheet or film.

Calendering: The extruded film passes through a series of heated rollers called a calender. The calendering process uses multiple rollers (usually 3 to 5) to gradually reduce the thickness of the film to its final size.

Calendering techniques used in the PVC shrink film manufacturing process include:

Three-roll or multi-roll calender: This is the most common type of calender used in PVC shrink film production. It consists of three or more rollers rotating at different speeds. The upper roller usually has a larger diameter than the lower roller and runs at a faster speed. As the film passes through the rollers, it is compressed and stretched, forming a thin, uniform film of controlled thickness.

Temperature control: Use steam, hot oil or electric heater to heat the calender roll to a specific temperature. This controlled temperature softens the PVC and ensures an even process.

Cooling: After the film passes through the heating roller, it is cooled by a cooling roller or a water cooling system. It helps solidify the material and stabilize its dimensions.

Thickness control: Calendering technology allows precise control of film thickness by adjusting the gap between rollers. This ensures consistent and accurate shrink characteristics of the final product.