Hello Nidia!
As the acting C2C Care community monitor, I'd like to thank you for posting this question to the community. Although the C2C Care program does not endorse any particular manufacturer or product, I invite members to discuss their equipment experiences and recommendations. I have not used any of these products, but after a quick review of their specifications, they all meet temperature requirements for sealing Mylar, will accommodate up to 8mil (0.008) thickness, and are open throat allowing for a continuous/overlapping seal. The MSC seems the most low-profile, convenient option as it can be placed on a tabletop which would allow for easier handling and maneuvering of large polyester sheets.
Hopefully our community members will be able to share their own experiences with similar devices and projects.
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Sharon Fickeissen
Connecting to Collections Care Monitor
Senior Library Conservation Technician
Hagley Museum & Library
Wilmington DE
sfickeissen@hagley.org------------------------------