PCTFE (Polytrifluorochlorotrifluoroethylene) and polytetrafluoroethylene (PTFE) have significant differences in molecular structure, physical properties, chemical properties, processing techniques, and application fields. The details are as follows:
1. Molecular Structure
PCTFE: The molecular chain contains one chlorine atom and one fluorine atom for every three carbon atoms (-CF₂-CFCl-). The introduction of chlorine atoms enhances the polarity of the molecule and reduces its crystallinity (approximately 35%-45%).
PTFE: It is composed of pure carbon-fluorine bonds (-CF₂-CF₂-), with extremely high molecular symmetry, and its crystallinity can reach over 90%.
2. Physical Properties
PCTFE:
Mechanical Properties: The tensile strength (40-50 MPa) is twice that of PTFE (20-30 MPa), the bending modulus reaches 1.4 GPa (PTFE only 0.5 GPa), and its hardness and strength are superior to PTFE.
Thermal Properties: The melting point is 215°C, and the long-term usage temperature limit is 175°C. The thermal expansion coefficient is relatively large (4.5×10⁻⁵/℃).
Barrier Properties: It has excellent gas barrier capabilities, and the water vapor permeability of its membrane products is the lowest among all transparent plastic membranes.
PTFE:
Mechanical Properties: The mechanical strength of pure PTFE is relatively low, and it needs to be enhanced through filling modification.
Thermal Properties: The melting point is 327°C, and the long-term usage temperature can reach 260°C. The thermal expansion coefficient is relatively small (1.2×10⁻⁴/℃).
Friction Properties: The friction coefficient (0.05-0.1) is the lowest among all solid materials, and it is superior to PCTFE (0.3-0.4).
3. Chemical Properties
PCTFE:
Chemical Resistance: Due to the high fluorine content, it can resist the erosion of most chemical substances and oxidants, but its chemical stability is slightly inferior to PTFE. For example, PCTFE will react with strong oxidants (such as concentrated nitric acid) at high temperatures.
Weather Resistance: It has excellent gas barrier properties, with extremely low water vapor permeability, and can be used for long-term stable use from -196°C to 155°C.
PTFE:
Chemical Resistance: It is almost not eroded by any acid, alkali (including aqua regia), or organic solvents, and has excellent chemical stability.
Weather Resistance: It has excellent weather resistance and no significant changes in performance when exposed to outdoor sunlight for a long time.
4. Processing Techniques
PCTFE:
Processing Methods: It can be processed using conventional thermoplastic processing methods, such as injection molding (melt temperature 230-280°C), extrusion molding (used for pipes and films), etc.
Processing Characteristics: The melt viscosity is relatively low, and the processing window is wide, but attention should be paid to the equipment corrosion caused by chlorine elements.
PTFE:
Processing Methods: Due to its extremely high melt viscosity (10¹¹-10¹² Pa·s), it cannot be processed by melting. The main processes include cold pressing sintering (pressure 20-50 MPa, sintering temperature 360-380°C), etc.
Processing Characteristics: Special equipment design is required to meet the high-temperature sintering needs.
5. Application Fields
PCTFE:
Chemical Field: Used for making corrosion-resistant pumps, valve components, and equipment linings, as well as structural materials.
Electronic and Electrical Field: Used as insulation for wires and cable sheaths, as well as connectors and printed circuit boards used in humid environments.
Optical Field: Transparent PCTFE (transmittance 90%) is used for infrared windows and laser components.
Other Fields: Such as pharmaceutical packaging, food packaging, and other demanding scenarios.
PTFE:
Chemical Field: Used as pipes, containers, pumps, valves, and corrosion-resistant materials for making radar, high-frequency communication equipment, and wireless electrical equipment.
Electronic and Electrical Field: Used as insulation layers for power and signal lines, corrosion-resistant, wear-resistant materials, and can be made into films, tube plates, bearings, washers, etc.
Mechanical Field: Used as lubricating materials for mechanical components to reduce friction and wear. Other fields: such as artificial organs for medical use, environmental protection filter materials, etc.
