of thermoplastics that can be utilized an alternate embodiment of the system is shown in fig8 having an element 30 with a different top surface the construction of the seal element 30 can best be understood with reference to fig3 which shows the element isolated by itself generally the seal 30 is of an annular configuration having a bottom surface a including a groove 34 for low pressure sealing for ease of description the outer peripheral surface of seal element 30 will be described in relation to fig3 in a counter clockwise fashion describing the different angles edges and surfaces starting from the lower left hand side edge points 1 2 3 4 4 u2032 5 6 and 7 generally outline the lower bottom surface of surface element 30 while points 8 9 10 11 12 13 14 and 15 depict the changing contour on the top surface t of seal element 30 generally bottom surface a is located between points 3 and 4 4 u2032 and 5 this surface a is in contact with inner member 19 during a non pressurized state of the seal assembly 13 located between points 5 and 6 is a surface b which creates an increased pressurized contact area during seal pressurization between points 6 and 7 is an extrusion resistant chamfer during pressurization seal element 30 tilts or rotates on point 5 bringing surface b into contact with member 19 between points 7 and 8 is a surface c which is a relief angle to allow seal element 30 to tip.