Sealing technology manual for the process industry

Optimization possibilities of PTFE Unfilled PTFE as a base material has some disadvantageous properties, such as poor cold flow behavior, relatively low wear resistance, low resistance to high-energy radiation and poor adhesion behavior. All of these can be eliminated by the addition of various additives. Reasons for admixing fillers in PTFE: • The wear resistance is increased many times over • The resistance to creep or deformation under load is in- creased to a multiple of the original value • Depending on the filler, the thermal conductivity can be increased significantly • The thermal expansion is reduced • If necessary, the electrical properties of PTFE can be changed by appropriate filler selection • The choice of filler also influences the wear behavior of the opposing surface Processing of PTFE PTFE cannot be processed by injection molding. For the pro- duction of components, different compounds, depending on the desired properties, can be used to produce semi- finished products (pipes, rods and plates), which are further processed into finished products in a subsequent process- ing step. MATERIAL PTFE VIRGIN PTFE + GLAS FIBER PTFE + CARBON PTFE + CARBON FIBER PTFE + BRONZE PROPERTIES TEST STANDARD MEASURING UNIT Filler content % of weight 25.0 25.0 10.0 40.0 Density ASTM D792 g/cm2 2.15 2.22 2.10 2.03 3.0 Ball indentation hardness DIN 2039-1 N/mm2 27.0 34.0 37.0 35.0 41.0 Tensile strength DIN 12086-2 MPa PR 29/UR 33 PR 14/UR 17 PR 12/UR 16 PR 18/UR 19 PR 24/UR 25 Elongation at break DIN 12086-2 % PR 354/UR 357 PR 353/UR 356 PR 120/UR 170 PR 307/UR 295 PR 343/UR 293 Tensile modulus of elasticity In -house standard T= +40 °C (+104 °F) MPa PR 446/UR 383 PR 674/UR 752 PR 925/UR 959 PR 673/UR 670 PR 760/UR 771 Deformation under load at +23 °C (+73 °F), 24 h, 15 N/mm2 comp. to ASTM D621 % PR 13.8/UR 16.4 PR 11.6/UR 13.9 PR 7.0/UR 6.3 PR 11.9/ UR 13.0 PR 8.4/UR 9.1 Irreversible deformation comp. to ASTM D621 % PR 7.0/UR 8.3 PR 6.2/UR 7.8 PR 3.2/UR 2.8 PR 5.9/UR 6.8 PR 4.1/UR 4.8 Tensile yield point 1% ASTM D695 MPa PR 11.0 PR 12.5 PR 13.7 PR 11.9 PR 13.1 Tensile yield point 5% ASTM D695 MPa PR 15.7 PR 16.8 PR 19.6 PR 16.8 PR 19.1 Surface resistance ASTM D257 Ω > 1017 > 1015 > 102 > 1010 > 1012 Thermal conductivity ASTM 1461 W/m·K 0.24 0.30 0.68 0.37 0.47 Coefficient of linear expansion at +50 to +100°C(+122to+212°F) DIN 53752 105 ·K4 10.6 9.8 8.2 11.7 8.8 PR = Pressing direction, UR = Circumferential direction Engineering plastics 50 Filler content % of weight 25.025.010.040.0 2.152.222.102.033.0 27.034.037.035.041.0 Thermal conductivity ASTM 1461 W/m·K 0.240.300.680.370.47 DIN 53752105 10.69.88.211.78.8

Pages Overview