... outer cover material, which in most cases is coated or laminated, protects the expansion joint from pressure ... requirements, although most joints are ¼" thick with two ply fiberglass reinforcement. Service conditions determine the type of ... layers of TFE (Teflon), fiberglass fabric, TFE impregnated fiberglass fabric, fiberglass insulation, Butyl, EPDM or Viton/Fluorel fabric. There are other materials ...