Abstract: Two or more layers of nonpolar thermoplastic film are bonded together by application of an RF current. The layers of thermoplastic film are pressed against a thin electrode plate, which lies atop a thin sheet of dielectric material supported on a conductive electrode die having a face or configuration to define the shape of the seal to be formed between the layers. RF current is applied to the electrode plate and to the electrode die, generating localized heat in the portions of the dielectric sheet overlying the die until the thermoplastic material has softened sufficiently to form a seal. A release agent, such as a sheet of polytetrafluoroethylene, can be provided on one surface of the electrode plate to prevent the thermoplastic material from sticking to the electrode plate.

Abstract: An apparatus for use in sealing layers of thermoplastic material together from one side of the layers includes a heat sealing electrode having a first conductive element mounted on a support and adapted to be connected to a source of high frequency energy, and a second conductive element mounted on the same support but in spaced general parallel relation to the first conductive element and adapted to be connected to an electrical ground. The conductive elements are electrically insulated from each other and, when they are applied to one side of the thermoplastic sheet material to be sealed and high frequency energy is supplied to the first electrode, a seal is formed in the material beneath and between the ends of the electrode elements.