Impulse sealers work by applying a timed amount of heat to seal thermoplastic films such as polyethylene, polypropylene, and PVA (poly bags, or poly lined bags).
Sealers are available depending upon how automated you want the operation to be to have perfect seals. Standard arm sealers are the lowest cost but require the operator to hold the arm down for the seal to congeal (cool down). Table top units have congealing cycles as well as automatic repeat cycles.
Sealers are available as bottom sealers, top sealers, and double sealers.