What is a stretch hood?
A stretch hood is a tube of film sealed on one end, which is stretched over a palletized load to secure the contents to the pallet. The film is cut to the appropriate length, heat sealed on the top end, and gathered on four 'fingers.' These fingers stretch the film in the horizontal (transverse) direction until the film dimensions are slightly larger than the load dimensions, then draw the stretched film down over the pallet, unrolling it as they go. By varying the unrolling rate, a degree of vertical (machine) direction stretch can be obtained to better hold the load on the pallet. At the bottom of the pallet, the fingers release the film, which typically wraps under the pallet bottom.
|The Stretch Hood Advantage
A two-minute introduction to the stretch hood process and the benefits of using the stretch hood palletizing method.
(December 20, 2006)
What market segments and applications use stretch hoods?
Stretch hoods are one of the fastest growing pallet stabilization and packaging systems, with current North American volumes around 60 million lbs/yr and a greater than 20% growth rate. Load stability and the flexibility to control elasticity and holding force make stretch hoods ideal for palletizing many applications - from empty PET bottles (high elasticity and low holding force) to cement bags (low elasticity, high holding force).
Building materials and heavy-duty shipping sacks in particular have seen a rise in popularity of stretch hoods. Specific applications include: bricks, stones, shingles, bagged concrete, and bagged resin. And, appliances have also seen high growth of stretch hoods (at the expense of corrugated board).
Why choose stretch hoods over other palletizing methods?
Stretch hoods offer the most comprehensive list of palletizing benefits, including:
- Logistics management - The stretch hood process is more efficient (100 loads per hour for stretch hood vs. 60 loads per hour for stretch wrap).
- Weatherability - Five-sided protection ensures products stay dry and provides protection against ultra-violet radiation.
- Package integrity - Load stability and abuse resistance mean a greater likelihood products arrive to their final destination unscathed and attached to the pallet.
- Display properties - The clarity of the film and the fact that a stretch hood is a single layer of film (vs. multiple layers of stretch wrap) help the logistics function identify errors or product damage and enable constant brand exposure.
What are the film requirements for stretch hood?
The stretch hood is a demanding application, requiring good tear and/or puncture resistance and a balance of holding force and elasticity. This, of course all starts with the quality of resins and finding the right formulation for specific loads. Dow resin technology for stretch hood film offers excellent abuse resistance and greater independent control over holding force and elasticity to meet the requirements of various load types. Other properties, such as high clarity, printability, and recyclability are also important for certain applications.
Stretch hood films are typically three-layer systems - two outer skin layers and the core. Dow offers DOWLEX™ Polyethylene Resins or ELITE™ Enhanced Polyethylene Resins for the skin layers.
So as you can see, Dow offers much more than a single resin solution in stretch hood film. We have a broad portfolio of plastic resins and technology to deliver formulations tailored to meet specific pallet load requirements.
Read more about stretch hood technology and Dow's focus on offering tailored stretch hood resin solutions in "The Perfect Fit in Stretch Hood" (PDF, 388KB).
Dow products suitable for stretch hood applications include: