By combining a variety
of materials, resins and tackifiers with stretch film’s basic
building block, polyethylene, different types of films have been
developed to obtain a desired set of film properties. Your Signode
salesperson carefully studies how your product is handled, stored,
shipped and received in order to make the best possible recommendation
for your operation.
Cling – the ability of film to adhere to itself. Needed
to bond film layers together and to secure film tail to load.
Tear and puncture resistance – ability to withstand perforation.
Helps prevent total web failure from small holes, nicks and tears.
Yield strength – point at which film will stretch further
with little or no increase in force. High yield strength ensures
consistent stretching of conventional grade films.
Tensile strength – strength of film at its breaking point
Ultimate elongation – percent of stretch at the point
of film failure. Films with low ultimate elongation do not work
well when prestretched.
Non-powered prestretch – Simple prestretch (50-100%)
using fixed gear. Requires film with medium cling. (Moderate
film usage)
Prestretching film – While stretching film makes
it thinner, unitizing strength actually improves as stretch
levels increase. Because prestretched film resists further
stretching, it holds pallets loads better than unstretched
film, which can stretch under the force of transit, causing
products to shift or fall off pallets.
Powered prestretch – Highest prestretch (100-300%). Requires
high performance blown films with high cling. (Low film usage)
Always check rolls
of stretch film for any of the following defects.
Possible
defects
End
result
Spots — gels
caused by bad resin or poor mixing, black specks from foreign
material or charred plastic, and white spots caused by additive
build-up on cast film
Film
breaks during stretching
Collapsed
cores — rolls are wound too tightly, crushing the paper
Mounting
roll becomes difficult
Telescoping — caused
by high tackifier levels or poor winding conditions
Core
slides out of roll
Wrinkling — caused
by poor transition winding
Wrinkled
film
Edge
defects — caused by film layers that extend past the
end of the roll
Tearing
and failure
Gauge
bands — hard, thick bands of film caused by poor gauge
control
Hard,
thick band of film that can be hard to remove
