MATERIAL DEVELOPMENTS
3 Fast Facts: Cohesive Peel Technology How might a cohesive peel system help with variability in seal strength? KEREN SOOKNE, DIRECTOR OF EDITORIAL CONTENT While many in the medical device packaging industry are familiar with adhesive peels, cohesive peel technology can offer advantages in reducing the variability in seal strength, reducing fiber tear, and offering a consistent peel for the end user. DuPont and PAXXUS representatives held a webinar to discuss the technology. Adhesive vs. cohesive Adhesive peel: As the film is peeling, it typically leaves both surfaces in the same state that they were in before they were sealed, explained Doug Dodrill, Chief Technology Officer at PAXXUS. As is shown by the light green section of sealant (next page, top image), it’s strictly separating without transfer of molecules between the surfaces. Cohesive peel: When the surface peels away from the Tyvek®, the sealant splits in the middle of the layer (see the light green section—next page, bottom image). “Basically, it’s sacrificing the ‘skin layer’ and transferring the skin over to the Tyvek surface, rather than peeling cleanly,” said Dodrill.
1. How is a cohesive sealant created? The main principle: start with one polymer and add an additional incompatible polymer (or two) to disrupt the polymer matrix. “That weakening of the polymer matrix is actually what creates the cohesive peel. Polybutene is a common one but there are many other combinations of incompatible polymers that will create the same effect,” said Dodrill. Jose Arevalo, Global Business Development Manager at DuPont, added, “The additive you put in creates a weak point in that film structure, so when you go to open it, it will break along that weak point that you’ve designed into the film layer.” The sealant is designed so that when the bonds within the sealant layer itself are weaker than the adhesive seal bonds, it will split and leave the polymer behind, rather than separating completely from the Tyvek (or other material). There are various ways to tailor cohesive film behavior to an application. Adding a colorant to the seal offers the ability to see the transfer occurring against the white Tyvek background. A key
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