Page 33 - The Inside Scoop Archive

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l Butene was introduced by Union Carbide and while not as strong or puncture resistant as Octene or
Hexene LLDPE's, it has one great advantage and this is price. It can be .03 to .05 per pound less than
the other LLDPE's. Because of this it is widely used in the manufacture of full gauge hand wrap.
Today Butene is also commonly used to replace LDPE in the manufacture of bags and sheeting. It is
sometimes referred to as a lower alpha olefin.
l Octene LLDPE was introduced by Dow Chemical and had much better properties for the manufacture
of stretch film than did Butene. It offers much greater physical properties such as puncture and tear
resistance. Octene and Hexene are also sometimes referred to as higher alpha olefins.
l Hexene LLDPE was introduced by Union Carbide to provide a counter to Octene. Both Octene and
Hexene have similar properties for the manufacture of stretch film.

Metallocene is a term used for a specific type or family of catalysts used to make polyolefins. Metallocene
resins are stronger, tougher, clearer, and have better adhesive properties than LLDPE. These resins are
more expensive than LLDPE resins and are often used as layers within a formulation to
give it the desired properties. We were one of the first companies to get involved in
a major way with metallocene resins when we developed the first Infinity stretch
film formulations. Through trial and error, we found that if we ran a solid layer of
metallocene approaching 50% of the total structure, we would get tear and pucture
resistance levels up to as much as 100% greater than the same gauge in a conventional
LLDPE stetch film. We also found that blending metallocene into the resin
formulation did not produce any positive results other than better clarity. Metallocene is a primary resin
that is used in many of the new technology stretch film formulations today.

Polypropylene or PP, is another polyolefin that is used in a few stretch films today. It is used primarily as a
separate layer to give a film some desired properties such as in a skin layer to give it more abrasion
resistance. Another great property of PP is that is enhances the TD tear resistance of stretch film. It
also allows the film to be used in certain high temperature work environments. A film made from a high
percentage of PP would have very poor stretch and puncture characteristics.

EVA or ethylene vinylacetate resins played a brief role in the history of stretch film. EVA resins were used
in combination with LDPE in the early days to provide better cling. It also offered improvements to LDPE
films in the area of clarity, toughness, and impact strength. As stretch levels grew, EVA was replaced with
ULDPE which offered superior cling at higher stretch levels.

ULDPE or Ultra Low Density Polyethylene resins offer excellent stretch and cling properties and are used
most often in the skin layers of 1-side cling stretch film. ULDPE also provides good low temperature
flexability.

HMWHDPE or high molecular weight high density polyethylene, has been used a few times in stretch film
primarily as a blended resin in the skin layer of the contructions. It was used to give better abrasion
resistance to the no cling side of the one side cling flm. It was not widely used and has pretty much been
discontinued.

The descriptions of the resins above are somewhat general in nature, and are not intended to be exhaustive
in any sense. I have tried to give you a working knowledge of the resins used in producing stretch film. If
you have any specific questions about any resin used in stretch film, I will be happy to try to provide you
with the answer you require.

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