Page 19 - The Inside Scoop Archive

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l The PIB can move toward the edges and cause the outside edges of the film
to hang up and result in film breaking and tearing.
l The PIB can cause the film layers to slide on themselves and "telescope" on
the core. The picture on the left shows a roll of stretch film with a
tackifier problem that is sliding off the core on one end.

I once visited a distributor in St Louis who had 18,000 lbs of stretch film in his warehouse that was sliding
off the core. It was not a pretty sight. Other horror stories include telescoping hand wrap pushing the
cases open and coming out of the box in a warehouse; and telescoping machine rolls pushing the cores out of
the rolls and making holes in the sheetrock walls next to where it was stored. To be fair on this issue, PIB
tackified blown film is very useful when pallets are stretch wrapped in low temperature environments,
where it's more liquid nature allows it to continue to provide cling where many conventional cast film
formulations do not work well.

So much for the tackifiers, there are a number of very good cling agents being used today that are resins
themselves and are part of the structure and do not cause the problems associated with PIB. They are
being used to produce great stretch films where cling is never an issue. Here are a few definitions of cling
stuctures that you should be familar with in considering films for your requirements.

Two Side Cling is still the most widely used film structure today. Both sides of the stretch film have cling
on them that provide good bonding of the film on the pallet. Most of these films usually have low cling, or
require more force to unwind them on the machine.

One Side Cling became possible with 3 layer co-extrusion and is used with the cling side wrapped "in" to the
pallet and the no-cling side wrapped "out" on the pallet. The no cling on the outside helps prevent pallets
from sticking together inside the trucks or warehouse, and pulling the film off the pallets.

Differential Cling actually has cling on both sides of the film structure but it has more on one side and less
on the other side. The use of less cling on the film side that is wrapped "out" on the pallet helps to prevent
pallets grabbing each other in the truck etc . Some blown films containing PIB are cooled in such a way that
the greater part of the cling is forced to one side can also be characterized as differential cling films.

Cling-No-Cling is essentially the same as One Side Cling. There is cling on one side and no cling on the other
side.

Slip Side has become highly popular in recent years. In this formula, the no-cling side of the structure has
a surface that is not just no-cling but is actully somewhat slippery. This is important for products such as
carpet or non-wovens that are wrapped as rolls and then need to be stored in a horizontal position in the
racks. The slip on the outside of the film is important to be able to pull the rolls from the racks without
the film being pulled from the product. This type of slip stretch film requires an even more aggressive cling
agent on the cling side in order to adher to a slippery surface on the other side of the film.

No-Cling is usally a cast film that is produced without the use of any cling. The absence of cling is
important in industries such as wrapping P.E.T. bottles where you do not want the film to adhere to the
bottles being wrapped. When the film bonds with the bottles it will pull them off the pallet as the film is
being removed at the production facility.

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