RPTFE (modified polytetrafluoroethylene) seals are widely used in the petrochemical, semiconductor, and other fields due to their excellent chemical resistance, low friction coefficient, and wide temperature range. The production process requires strict control of parameters at each step to ensure product performance.
Raw material pretreatment is the first step. The base PTFE resin is mixed with fillers such as carbon fiber and glass beads in appropriate proportions and evenly dispersed using a high-speed blender. The filler content is typically controlled between 15% and 30% to achieve a balance between mechanical strength and sealing performance. The pretreated material is dried in a constant temperature drying oven at 80-100°C for 2-4 hours to remove moisture and prevent molding defects.
Compression molding utilizes a two-step process: cold pressing and sintering. The pre-treated material is placed into a mold and pre-pressed at a pressure of 20-30 MPa to a density of 1.8-2.0 g/cm³. It is then transferred to a sintering furnace for a gradual temperature increase: the temperature is raised at a rate of 100°C/h to 380°C (PTFE's melting point), held for 2-3 hours to allow for full molecular chain rearrangement, and then slowly cooled to room temperature over 10-12 hours to avoid stress concentration that could lead to cracking.
Post-processing is crucial. Sintered parts are precision-machined to the designed dimensions using CNC, with tolerances within ±0.05mm. Surface treatment typically involves impregnation with graphite or molybdenum disulfide to reduce the coefficient of friction to 0.1-0.15. Some products requiring specific application conditions also require plasma treatment to increase surface energy and enhance sealing.
Quality control is implemented throughout the entire process. Each batch undergoes density testing (≥2.1 g/cm³), full dimensional inspection, and helium mass spectrometry leak testing (leak rate <1×10⁻⁹mbar·L/s). Special applications also require cyclic testing from -200°C to 260°C and immersion in acid and alkaline media for verification.
This process combines material modification with precision manufacturing technology to ensure RPTFE seals combine the chemical stability of fluoroplastics with the mechanical properties of reinforced fillers, meeting the requirements for long-term, reliable sealing in demanding operating conditions.
