Fluoroplastics can be molded into sheets, rods, sleeves […]
Fluoroplastics can be molded into sheets, rods, sleeves, tapes, seal rings, diaphragms and parts with metal inserts.
Molding is divided into three steps of preforming, sintering and cooling. Pre-forming is to uniformly add PTFE powder into the mold and pressurize it into a dense preform (ie, blank) at normal temperature; sintering is to heat the preform to above the melting point, and cooling is a process from the sintering temperature to room temperature.
Some fluoroplastics are formed by pressing at a temperature above the melting point. This molding die is called a hot stamping die. The corresponding PTFE mold is called a cold stamping die.
At the time of molding, attention should be paid to the influence of the compression ratio (generally PTFE is 4-6) and the molding shrinkage ratio (generally 2.6 to 4.5% of PTFE) on the product.
The raw material is preferably a polymerized resin by a suspension method, and a soft fine powder having a particle diameter of 20 to 500 μm is most preferable. The pressing process must be “deflated”. The preforming pressure is 17-35 MPa. The holding time depends on the thickness of the blank. For example, a 100 mm thick blank should be held for 15 minutes.
When sintering, it should be noted that the heating rate can be 20-120 ° C / hour, the larger the product, the slower the heating rate, the higher the sintering temperature of the suspension resin is 370-380 ° C, and the sintering temperature of the dispersion resin is lower, 360- At 370 ° C, the sintering temperature is high, the shrinkage and porosity are increased, and the sintering time should be properly controlled.
Cooling, generally slow down with a speed of 15-25 ° C / hour, in special cases, such as a small thickness of less than 5 mm thin plate or push-formed thin-walled tube, use rapid cooling.
Sometimes the article is annealed at a temperature of 100-120 ° C for 4-6 hours.