These days most companies prefer polyolefin shrink wrap. A polyolefin (POF) or its modern term polyalkene, is a polymer produced from an olefin (alkene) monomer. For example, polyethylene is a polyolefin produced by polymerizing ethylene.
POFs are used to make plastic bags, stretch films, shrink wraps, geomembranes, and other plastics. Polyethylene plastics are the most widely used polyolefins.
Two of the most commonly used POFs are low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE).
LDPE is the first grade of polyethylene created and is currently used for plastic bags, trays, and six-pack rings. LDPE is resilient and flexible, but has a low tensile strength; therefore they cannot be stretched far before breaking.
Most stretch films are made of LLDPE. LLDPE stretch films have a substantial number of short molecular branches, but because of its absence of long chain branching it differs structurally from LDPE. LLDPE stretch film is made at lower temperatures and pressures than LDPE films by copolymerization of ethylene and other olefins. LLDPE films have a higher tensile strength, higher impact resistance, and a higher puncture resistance than LDPE which are desired traits for most stretch films. LLDPE stretch films do not strain harden as LDPE films do. As strain increases, LDPE films rise in hardness while LLDPE stretch films do not. LLDPE stretch films remain flexible and elongate under stress. Stretch films made from LLDPE can be downgauged easily while maintaining strength and toughness. LLDPE stretch films are also resistant to environmental stress cracking making them useful for wrapping important products safely and securely. These stretch films are also resistant to chemicals, low temperatures and ultraviolet exposure.
There are two ways of making stretch films: blow or cast. Blown stretch films are air-cooled in a slower process yielding higher quality stretch films. Due to the slower processing and higher quality, these types of stretch films are generally more expensive. Cast stretch films are cooled with rollers producing a lower quality stretch film at a cheaper rate. LLDPE stretch films can be recycled, but only into other things like trash liners and floor tiles.
Another common plastic is polyvinyl chloride (PVC). PVC is durable, cheap, and easily worked. It is used for sewage pipes, window frames, plastic wrap and shrink wrap. PVC is considered to have low toxicity because of its inertness, so shrink wrap made of PVC will not leach into products. The addition of plasticizers does not technically increase the toxicity of shrink wraps made from PVC as the plasticizers are tightly bound into the plastic. There are, however, health concerns of shrink wraps and other plastics made of PVC, because it is difficult to fully polymerize. This means traces of the vinyl chloride monomer may remain potentially causing contamination. Also, PVC shrink wrap releases small quantities of hydrogen chloride into the air and carbon deposits onto the sealer during the sealing process, so proper ventilation is required when sealing PVC shrink wrap. PVC shrink wraps are cheap and are used to package CDs, DVDs, and non-edible items. PVC shrink wrap works well with automated machines, a reason companies often choose PVC shrink wraps over POF shrink wraps, but PVC shrink wrap does react to extreme temperatures more readily than shrink wraps made of POF, which can compromise the strength of the seal. Shrink wraps and other plastics made of PVC are difficult to recycle, but have a recycle symbol of “3.” This is one reason industries are moving towards POF shrink wraps. Today’s market offers the ability to shrink wrap just about anything. This ranges from the commonly shrink wrapped items in local businesses listed in our previous post to some surprising shrink wrapped items including cars, boats, helicopters and buildings.
Shrink wraps, including those sold here, come in various styles, from shrink bags, shrink tubing, and centerfold shrink wraps. Centerfold shrink wraps are convenient because one edge is available to align on your product so the other three sides can be sealed and shrunk together in an efficient manner.
The industry is also moving towards POF shrink wraps because they do not contain traces of potentially toxic additives. LDPE films do not cling as well as PVC but by adding LLDPE, the effect can be achieved. New research is constantly moving the industry towards better shrink wraps and stretch films made of POF.
We still believe that PVC shrink films are ideal for a large variety of uses, but polyolefin shrink wrap is a superior shrink film. We are happy to offer both to our clients at affordable prices. If you have any questions about any shrink wrap or stretch film products, feel free to visit our online store or call us at 1-800-441-5090.