up to 60 u00b0 to 65 u00b0 c melting points of from approximately 65 u00b0 to 85 u00b0 c are preferred typical materials are waxes and synthetic thermoplastics of which waxes are preferred waxes suitable for use herein include 34 duron petroleum micro wax 170 180 34 a microcrystalline wax melting at 170 u00b0 to 180 u00b0 f 76 u00b0 to 82 u00b0 c with a viscosity of 75 sus at 210 u00b0 f 99 u00b0 c 34 loobwax 0597 34 a paraffinic wax of a type known to the industry as 34 165 wax 34 melting at 71 u00b0 c with a viscosity of 7 cs at 100 u00b0 c and 34 duron pure ozokerite 71 74 34 a wax with pronounced iso paraffinic properties melting at 73 u00b0 to 74 u00b0 c of which the last is preferred these are marketed by dura commodities corporation of new york other suitable waxes include candelilla wax mp of 67 u00b0 to 69 u00b0 c and cotton wax mp of 68 u00b0 to 71 u00b0 c when freon 500 trademark of e i du pont de nemours and company is the propellant the normal operating pressure in the container is approximately 103 psia 709 kpa at 70 u00b0 f 21 u00b0 c 34 duron pure ozokerite 71 74 34 above is the preferred plug material and the container is constructed so that its.