In an improved quick disconnect coupling comprised of operator-actuated coupler and nipple assemblies, the former including an actuating sleeve, with the coupled assemblies having first and second sealing assemblies respectively, wherein the improvement comprises, in combination, that each of the sealing assemblies includes, in addition to the known torodial sealing element, a first non-continuous metallic backup ring and a second non-metallic backup ring interposed between the torodial sealing element and the first backup ring, both backup rings being of generally truncated triangular shape, in cross section; and a metallic insulating sleeve, surrounding the actuating sleeve while being substantially fully radially spaced therefrom, via a peripheral air gap, except for a band portion at one end thereof, this band being interference-fitted on a corresponding portion of the actuating sleeve and including a plurality of axially-extending, spaced, scalloped recesses defining an additional insulating air space and having spaced boundaries that provide surfaces for the interference-fitting.