TAIFNO PTFE Sintering Process for PTFE Gaskets,Tubes,Sheets,etc.
Many customers asked "How do you make Teflon into a seal product? What process ?" This is about the characteristics of PTFE. PTFE products are widely used because of their unique properties. But also because of its uniqueness, it does not flow after reaching the melting point, so can not use ordinary plastic injection molding technology. Now commonly use molding and sintering process to make the products.
◆ Molding shrinkage: 3.1-5.0%
◆ Molding temperature: 330-380 ℃
◆ Sintering conditions: the best temperature should not exceed 385 degrees, otherwise the molecules will necrosis, affecting the quality.
◆ Molding pressure: the critical pressure of pure PTFE material is about 27.5 MPa, the compressive strength of PTFE material decreases with the increase of pressing pressure; the compressive modulus increases with the increase of pressing pressure. At last, the forming pressure of PTFE was determined to be 27.5 MPa.
◆ Sintering process: sintering temperature is 380 ℃, holding time is 4 hours, heating rate is 80 ℃ / h below 200 ℃, 60 ℃ / h above 200 ℃, the cooling rate is cooling with the furnace.
◆ Sintering Temperature Curve:
The step 1 drying at 120 degrees
The step 2, such as filling graphite or disulfide ink at 250 degrees for temperature processing
The step 3, processing at 345 degrees
The step 4, processing at 375 degrees
The Step 5 ,do not cool too fast
1. PTFE crystal material, small moisture absorption.
2. PTFE poor liquidity, easy to decompose, decompose produce corrosive gas. Should strictly control the molding temperature, the mold should be heated, pouring system on the flow resistance should be small.
3. PTFE powder often use powder metallurgy molding, using the sintering methods. Sintering temperature should be 360-375 degrees, can not exceed 410 degrees. Emulsion resin can form a coating on the surface . If need product transparency, good toughness, should take rapid cooling. Also can use the mold forming, you can squeeze the tube, rods,etc.
4.PTFE melt viscosity is high, the viscosity decreases with the increasing of shear stress, showing its non-Newtonian fluid properties.
5. Secondary processing, can hot-pressing compound, welding, bonding, enhanced, machining, etc., in order to produce the final product.