Method of fabricating welded PFA-to-PTFE structures

Claim 1

A method of forming a fluorocarbon resin structure in which a body of PFA resin is fused to a body of sintered PTFE resin which comprises the steps of confining a quantity of particulate PGA resin in a zone contiguous to said body of sintered PTFE resin, heating said quantity of PFA resin and at least the PTFE resin which is adjacent said zone to a temperature above the gel point of said PTFE resin and above the melting point of said PFA resin to melt said PFA resin, maintaining said elevated temperature while compacting said PFA resin against said PTFE resin under positive pressure just sufficient to urge said PFA resin melt at a very slow rate without fault producing flow therein into intimate surface contact with said PTFE resin until said former wets the surface of said latter over an area to be fused, after establishing said intimate contact, maintaining the conditions static at the fusing interface by increasing the pressure applied to said PFA resin to a predetermined level at a rate which is sufficiently slow so that there is a minimum tendency for said PFA resin to flow along the surface of said mating PTFE resin, and permitting said resins to cool slowly without force cooling toward ambient temperature while maintaining said pressure near said predetermined level where said predetermined level is chosen sufficient to prevent the formation of sinks and voids in said PFA resin while cooling but below the level at which noticeable flow is induced in said PFA resin, and continuing said cooling at least until said PFA has solidified, thereafter completing said cooling and removing said pressure, whereby said PFA resin becomes fused to said body of PTFE resin at the interface therebetween.

Claim 2

A method of forming a fluorocarbon resin structure in which a body of PFA resin is fused to a body of sintered PTFE resin which comprises the steps of confining a quantity of particulate PGA resin in a zone contiguous to said body of sintered PTFE resin, heating said quantity of PFA resin and at least the PTFE resin which is adjacent said zone to a temperature above the gel point of said PTFE resin and above the melting point of said PFA resin to melt said PFA resin, maintaining said elevated temperature while compacting said PFA resin against said PTFE resin under positive pressure just sufficient to urge said PFA resin melt at a very slow rate without fault producing flow therein into intimate surface contact with said PTFE resin until said former wets the surface of said latter over an area to be fused, after establishing said intimate contact, maintaining the conditions static at the fusing interface by increasing the pressure applied to said PFA resin to a predetermined level at a rate which is sufficiently slow so that there is a minimum tendency for said PFA resin to flow along the surface of said mating PTFE resin, and permitting said resins to cool slowly without force cooling toward ambient temperature while maintaining said pressure near said predetermined level where said predetermined level is chosen sufficient to prevent the formation of sinks and voids in said PFA resin while cooling but below the level at which noticeable flow is induced in said PFA resin, and continuing said cooling at least until said PFA has solidified, thereafter completing said cooling and removing said pressure, whereby said PFA resin becomes fused to said body of PTFE resin at the interface therebetween.