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 and 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 blending with plasticizer during fabrication. This versatility is a major advantage of vinyl polymers.
PVC film without plasticizer is called rigid vinyl film, whereas plasticized PVC is called flexible vinyl film.1
Flexible Vinyl Film
Flexible vinyl film has good barrier properties to oil and grease but is oxygen permeable. It also has good cling, excellent clarity and puncture resistant. These properties make flexible PVC suitable for food packaging to keep meat and other perishable produce fresh (when FDA approved). However, plasticized PVC has a lower melting point, is less resistant to chemicals, and has a 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 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 and can compromise the strength of the seal. PVC also releases small amounts of hydrogen chloride into the air and produces carbon deposit onto the sealing equipment when heated. 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 and flexibility of PVC is the result of plasticizer molecules migrating between polymer molecules, reducing intermolecular forces.