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Resins Used In Stretch Film

Today we are going to try and introduce you to some of the more important resins used to manufacture
stretch film. I am not an expert on this subject so let me make that clear going forward. I have had the
opportunity to be involved in the manufacturing and selling of stretch film since 1975 so I do have a lot of
history on this subject. When I first got involved with stretch film in 1975 with Mobil Chemical, we were
making stretch film out of LDPE and our largest competitor was producing it out of PVC. So let's start
there.

LDPE is Low Density Polyethylene. It is a general term for polyethylene ( PE ) resins, and is used in many
types of products such as dry cleaning bags and trash bags. LDPE is a poly-ethylene homopolymer made by a
process that takes ethylene gas and polymerizes it using a relatively inexpensive free
radical catalyst. LDPE has many long branches which entangle during extrusion. This
limits it's ultimate stretch, but provides good load containment in stretch film.
Puncture resistance is low as is the tear strength across the web. It is difficult to
produce films under 1 mil ( .001 or 100 gauge ) with high strength LDPE. Maybe this
is why the first stretch films which were made with LDPE were 1 mil ( 100 gauge ) or
above. Mobil C, anyone here remember Mobil C stretch film?... was a 100 gauge 20" x
4,500' film that would stretch about 20%. This is the point where I entered the
industry.

PVC or polyvinylchloride was the resin that was used to make the high performance stretch film in the early
days of the industry. PVC is best known today as the film that is used for meat wrap at the grocery store,
and for cling film used at your favorite restaurant. It has outstanding clarity and good cling for low stretch
applications. LDPE would stretch about 20%, but PVC would stretch about 30%. Hey, that's 50% more
stretch which made for real tough competition back in the 70's. PVC's weakness was it's poor tear
strength, and it's tendency to zipper quickly when the web was nicked or torn. Once stretch levels moved
beyond 30%, PVC was doomed as a major player in the stretch industry.

Mobil X was the first LLDPE stretch film to be introduced. Mobil had made a deal with Dow for the LLDPE
resin to be used in their retail trash bag line and discovered that its elongation and puncture resistance
properties were also great for stretch film. Mobil pretty much had a one year up on the industry to market
LLDPE stretch film before any of their competitors were able to secure the resin. During that year they
became the dominant force in stretch film which continue for many years.

LLDPE or linear low density polyethylene, is a copolymer of ethylene and another ethylenic monomer such as
butene, hexene, or octene which are known as comonomers. These polymers have many short branches and
offer better untimate stretch, cross directional tear resistance, and puncture resistance. LLDPE has
provided the high ultimate stretch and puncture resistance that have allowed stretch film to migrate from
100 gauge or 1 mil down to 50 gauge or 1/2 mil. LLDPE is the resin that made the rapid growth of stretch
film possible.

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