Abstract: A portable heat sealer for sealing heavy grade thermoplastic films comprises a plurality of adjacent, segmented heating elements positioned along the underside of a heated sealing bar. The segmented heating elements are under the control of a microprocessor for controlling the energy applied to the heated sealing bar to avoid the formation of hot spots and to obtain a strong seal. Each heating element is maintained in firm contact with the heated sealing bar by means of a tension spring. A thermoplastic film bag is placed on the heated sealing bar and a movable sealer jaw is lowered on top of the bag. A jaw switch is activated by the sealer jaw which turns-on power to the heat sealer. A latch 32 attaches to a clip on the end of the sealer jaws and secures the sealer jaw in place. Pilot lights are provided to indicate to an operator the cycles of “ready”, “heat” and “cool”.