Polyvinylidene chloride
Polyvinylidene chloride (PVDC) is a thermoplastic polymer, commonly known as Saran. It is a long-chain vinylidene chloride polymerized from vinylidene chloride with monomers such as acrylates and unsaturated carboxyl groups. The film formed by PVDC has the characteristics of blocking steam, moisture and oxygen. It is most commonly used as a barrier film for packaging.
Processing
Melt-processable VDC copolymers can be used for injection molding, extrusion, blow molding, co-extrusion into film and sheet, and quench roll flat extrusion. Low melt strength hinders conventional single-layer film melt blowing processing, such as film blow molding and extrusion blow molding.
During processing, the melt temperature should be maintained below 400°F to prevent polymer decomposition. For processing equipment, special consideration should be given to the parts in contact with hot polymers. Corrosion-resistant alloys, especially nickel alloys or high-nickel steels, should be used; the equipment should be streamlined to shorten the polymer stagnation time in the equipment, and polymer hanging should be avoided. Heavy metals, such as iron, copper, and zinc, can cause catalytic decomposition of resins and should be avoided.
Applications
It can be made into single-layer films, multi-layer films, sheets and coatings for food packaging to isolate external moisture and certain gases while maintaining food flavor and smell. Food components. Highly barrier copolymers can be heat-processed into rigid packaging containers for packaging volatile substances or for isolating external gases and moisture, such as form-fill-seal packaging and plastic can packaging.
Some single-layer films are widely used as household packaging films, and industrial single-layer films are usually used in laminated forms, such as unit-dose drug packaging, cosmetic packaging, and food packaging.
Recycling of polyvinylidene chloride (PVDC)
Mechanical recycling
Mechanical recycling is the process of physically crushing, cleaning, melting and re-granulating waste polyvinylidene chloride materials. This method is relatively simple and suitable for large-scale recycling, but impurities may be introduced during the recycling process, affecting the quality and application range of the recycled materials.
Chemical recycling
Chemical recycling involves more complex chemical processes, including solvent dissolution recycling. Solvent dissolution recycling uses a solvent mixture to separate contaminants such as dyes, adhesives or metals from plastics, leaving pure polymers for reuse. This method can more effectively remove impurities and improve the quality of recycled materials.
