The Purpose of Shrink Wrap
Shrink wrap is thin, clear, low cost plastic sheeting. Usually found in a roll stock. Used for protection, product enhancement and for protecting packages from being opened prior to purchase.
- Provide a see-through over wrap for a clear sparkling display
- Used to bundle multiple products together
- Reduces cost of product packaging
Shrink Packaging is typically a two step process:
- Wrapping & Sealing the product
- Applying heat to firmly tighten (shrink) the film around the product
Wrapping & Sealing
The most popular wrapping and sealing machine is the “L” bar sealer. The name derives from the sealing bar in the shape of a backward “L”. The L-Bar sealer which comes in a variety of sizes, and with a variety of options, trim and seal the film with each down stroke or cycle of the sealing bar. By using a center folded film side seals of the package are simultaneously formed, producing a fully sealed individual bag around each product –ready to be heated and shrink-wrapped.
Applying Heat
The most common method of applying heat is a hot air circulating chamber, with a conveyor to move the product, otherwise known as the heat tunnel. Products travel through the tunnel, and are exposed to heat for only a few seconds. While traveling through the tunnel, shrinkage occurs. Since this only takes a few seconds, only the shrink wrap will be affected by the heat, not the product. Occasionally heat guns are used for applying heat and shrinkage.
Polyolefin Versus PVC
Advantages of PVC (PV Clear)
- Available in lower and preferential shrink forces
- Reduced dog ears and less crows feet
- Sparkle and shelf appeal
- Lower sealing temperatures and shorter dwell times
- Low tunnel temperature, higher line speeds
- Unsupported lap seal
- Creep and zipper resistance
- Variety of film stiffness
Advantages of Polyolefin (Sytec 307S, Sytec 701 or MVP)
- Food grade film
- Dimensional stability
- Does not require cool storage
- Does not require shipping by refrigerated truck
- Excellent lie flat properties
- Does not require equipment modifications to prevent smoke
- No corrosion, smoke, or odors
- Creates no build up of material on machine sealing wires