Specialized welding equipment has been developed in which the pressure and the rate and area of
heating are precisely controlled in order to provide strong, tight bonds. The strength of the welds,
however, can differ widely among the various plastics. Hot-gas welding is generally performed only on
thermoplastic materials having thickness of 1/16 inch or more. Thermoplastic sheeting and films that are
used primarily for packaging are often heat-sealed. Heat-sealing will not be discussed here because it is
not used in structural fabrication.