3M Very-Low Outgassing Polyester Tape 8439 is a silver-colored polyester film tape for the demanding requirements of electronics manufacturing.A silver-colored polyester film tape for the demanding requirements of electronics manufacturing. The metalized polyester backing offers low static and diffusivity and is complimented with a very low-outgassing acrylic adhesive. This product offers a high level of permanence, yet is cleanly removable from most substrates even after extended heat treatments.