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Brentwood Plastics Blog

What is Regular Poly Film ? is an oversimplification

Posted by Joel Longstreth on Mon, Dec 19, 2011 @ 12:33 PM

Asking for " regular poly" film is like asking for a regular car, beer, soda, tape or wine. 

The variation within the species of polyethylene film resins has evolved because different PE resins are made to do different jobs.  Just as one would not use a subcompact car to do the same job as a passenger van, it does not make sense to use the same PE resin made for dry cleaner bags to package 50 pounds of rock salt. 

We do have a middle of the road general purpose clear LDPE sheet film called GPC http://www.brentwoodplastics.com/data_sheet_gpc.pdf#zoom=100.  While it is warranted to be only a simple low cost general purpose plastic film, people continue to try to cut costs by using general purpose clear for applications which require specific properties. 

Here are just a few cases of ordering GP clear plastic films to cheap it out and why they ended badly:

Bread bags must have a very low coefficient of friction ( COF ) to load and release without jamming up.  General purpose clear is not a high slip / low COF poly film. 

Potato bags must be stronger than bread bags for obvious reasons.  The bailer bags which hold 10 or so potato bags must be very strong and low slip for stackability.

Ice bags and IQF frozen films must have EVA or metallocene for low temperature stability and strong seals.

Shipping sacks, like bailer bags, must be made from a more durable resin usually having a lower melt index known as a "fractional melt" for durability and must be low slip.  GP clear is not strong and the bags slide all over the place.

Lamination sealing layers must have a fast hot tack achieved only with the addition of EVA or metallocene.

Bank deposit bags must have zero slip or the pressure sensitive tape will not adhere to creat a tamper evident seal.

Last week we had two inquiries for "regular poly" to be used in prolonged and direct contact with human skin in medical devices.  We had to explain that different rules apply for medical applications.

There is no such thing as regular poly.  It is best to tell your PE film supplier what you are doing with the film, then continually test as you scale up to determine suitability for any end use.

Topics: poly film

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