Polyvinyl, also known as poly(vinyl chloride) or PVC, is the third most widely produced synthetic plastic. It is a very versatile and cost-efficient thermoplastic of good dimensional stability, good impact strength (when plasticized), and excellent weathering properties. It can be easily extruded, calendered, and die-cut, and is printable with conventional screen and offset printing methods. Depending on the composition, it can be clear or matt, colored or white, and rigid or flexible. It can also be easily reprocessed using heat.
PVC has a rather polar backbone with strong intermolecular interactions. It is, therefore, rigid at room temperature. However, it can be easily softened (plasticized) by adding plasticizer during fabrication. This versatility is a major advantage of vinyl polymers.
PVC film without plasticizer is called rigid vinyl film, whereas PVC film that is plasticized is called flexible vinyl film.1
Flexible Vinyl Film
Flexible vinyl film has good barrier properties to oil and grease but is oxygen permeable and is puncture resistant. It also has good cling and excellent clarity, which makes it suitable for food packaging to keep meat and other perishable produce fresh (when FDA approved). This type of PVC has a lower melting point and is less resistant to chemicals, and typically has lower ultimate tensile strength than rigid vinyl.
Rigid Vinyl Film
Rigid vinyl, also known as unplasticized polyvinyl chloride (uPVC), is a strong and lightweight film. It is one of the most durable, low-cost films and is resistant to many chemicals. Generally, uPVC can be used at temperatures up to 60°C. It has higher tensile strength and modulus than flexible PVC, but is also has low impact toughness, and is subject to stress cracking depending on the environment.
PVC has several limitations and drawbacks; the plasticizer can harden in cold conditions and soften under hot conditions, which lead to a change in properties, which can compromise the strength of the seal and the plastic. PVC also releases small amounts of hydrogen chloride into the air and carbon deposits onto the sealing equipment. For this reason, good ventilation is required when sealing PVC shrink-wrap.
PVC film is used as shrink and stretch wrap for industrial and consumer goods and as pallet wrap, however, on a much smaller scale than polyolefin films. Other uses include bags, liners, bottle sleeving, adhesive tape backing, labels, blood bags and I.V. bags. It is often PVDC coated when improved moisture barrier properties are required.
FDA approved PVC is a good choice to package fresh red meat because it is semi-permeable, meaning, it is just enough oxygen permeable to keep meat products fresh and to maintain its bright red color. When transparency is important, PVC is often used.
1”The softness or flexibility of PVC is the result of plasticizer molecules migrating between polymer molecules, reducing intermolecular forces.