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Brentwood Plastics Blog

Metallocene VS EVA

Posted by sam Longstreth on Tue, Jun 21, 2011 @ 12:01 PM

Ethyl Vinyl Acetate (EVA) is a living dinosaur.  It should be extinct but it isn't.  In it's raw state EVA has the consistency of clear rubber.  It smells like vinegar. When added to homopolymer polyethylene in samll percentages (1 to 3%) it can enhance the clarity and sealability of a film.  When added in higher percentages (4 to 6%) it further enhances sealabilty and increases the films's cold stress crack resistance.  At the 4 to 6% loading the optics of the film decrease due to the high amounts of antiblock needed to prevent the film from sticking to itself.  Even higher loadings of EVA are still used for very cold applications and in situations where there is a large amount of contaminate in the seal area.   We stock it because people still buy it even though they would be better off using a very low density metallocene.  

We understand resistance to change but we don't like it.  Metallocenes have better optics, better physicals, a lower heat seal initiation temperature, better cold temperature stress crack resitance, less taste transfer, less expensive and offers a better opportunity for downgauging than EVA's.  When we ask people why they want EVA they say, "Its what we've always used and it is written in the spec.".  Why laminators still call out EVA in their specifications for sealant webs is beyond reason.  In some radio frequency welding applications EVA may be a better choice than metallocenes but we have several brave customers who have made the transition away from EVA to metallocene for RF welding applications.  IF you are still using EVA give us a call and we can show you how metallocenes can improve your life. 

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Topics: metallocene, EVA, PEVA

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