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Brentwood Plastics Blog

Melt Fracture in PE film

Posted by Joel Longstreth on Mon, Apr 14, 2014 @ 05:57 PM

Melt fracture a/k/a "sharkskin" or "applesauce" occurs in LLDPE film.

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To say that much has been written on the subject is an understatement.  Entire books and dissertations abut melt fracture have been written by polymer chemists a lot smarter than me.  Still there is not total agreement on the causes.  Personally, I have a hypothesis that it has something to do with susceptibility to degradation in the transition section of the screw.  

Going back to the early days of LLDPE  http://www.brentwoodplastics.com/blog/bid/131888/LLDPE-Linear-Low-Density-Polyethylene-varieties melt fracture was just expected in butene LLD but not Octene.  Carbide advocated a return to shorter L/D ratios for shorter residence time.  This and granular resin never really took off.

No matter the cause, melt fracture results in a very irregular scaly texture to the film.  In most cases, this is considered an undesirable quality because it detracts from the cosmetics.  In a few cases such as forearm protectors it is considered a plus but i don't know why.

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Topics: LLDPE melt fracture

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