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How Many Layers ( 3,5,7,9 ) Make The Best Stretch Film?

When I first started out in stretch film in 1975 with Mobil Chemical as the Industrial Sales Manager for
the southeast, we were selling a cast 1 layer film that stretched up to 20% at one mil ( 100 gauge ). It was
the best film available at the time. Later stretch film moved to 3 layers making 1-side cling film possible. It
was not until the 1990's when 5 layer dies became available and were teamed with 5 extruders, that true 5
layer stretch film became possible. We were one of the first to take advantage of this new technology,
together with the new resin, metallocene, that was just being introduced. We found that if we ran a 50%
layer of metallocene in the middle of the film structure, we could achieve up to 100% greater tear and
puncture resistance than conventional films of the same gauge. You guessed it. That was the beginning of
Infinity Power Wrap stretch film.

In 1998 dies with up to 7 layers were introduced, and in the past few years there have been several
production lines with 9 layers added to stretch film plants.

So, how many film layers does it take to make good stretch film? If a 5 layer film
is better than a 3 layer film, does it follow that a 7 layer film is better than a 5
layer, and a 9 layer film is better than a 7 layer film? If the salesman you are
listening to is selling a 7 layer stretch film, you can bet your farm that he is going
to tell you 7 layers are better than 5. The same would be true if he is selling a 9
layer film, he will definitely tell you it's better than an old fashioned 7 layer
stretch film.

Ok, are you ready for the Inside Scoop on how many layers it takes to make good stretch film? The answer
is that the number of film layers is not nearly as important as what type of resins are being put into the
layers; the volume percentages of the resins; and the receipe being used to produce the film. The best
films are produced on extruders using 4 or more layers where there is the opportunity to improve certain
film characteristics such as greater puncture resistance, stretch or load containment by burying a layer of
resin to support the desired film characteristic. These 4 plus layer lines also provide the opportunity for
improved cling layers at a lower percentage of the structure and without creating resin gels that were
associated with slower flow rates in the cling layers. Probably the leading machine stretch film in the
industry today is being made on both 5 layer and 7 layer extruders with equal performance. The
performance levels of these films have not been duplicated by any competitor up to this point with either 5,
7, or 9 layers.

To be honest about it, one of the initial promotions for increasing the number of layers in stretch film was
that the manufacturer would be able to "bury" lower cost resins in the film structure. Thus reducing his
overall cost while maintaining an acceptable product. It is my belief that early on this was the case with
many of the manufacturers embracing the new extrusion technology. More recently the tide has turned,

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