PTFE Has Good Physical And Chemical Properties

Although PTFE has good physical and chemical properties, it also has some defects, such as its poor mechanical properties, large coefficient of linear expansion, poor creep resistance, easy cold flow, poor wear resistance, difficult molding and secondary processing, etc. subject to certain restrictions. With the rapid increase of PTFE production capacity in my country, strengthening the research and application of PTFE modification technology and developing new and efficient PTFE composite materials have become the current research and development direction of PTFE in China. PTFE can be modified by various means such as reinforcement, filling, compounding and blending to make up for its own defects. The main methods are surface modification, filling modification and blending modification.

1. Surface modification

The extremely low surface activity and non-stickiness of PTFE limit its compounding with other composite materials, so certain surface modification must be carried out on the PTFE material to improve its surface activity. Common technologies include (a), surface activation technology: the surface can be defluorinated by radiation of high-energy rays, and fluorinated and grafted with other materials under certain equipment and conditions; PTFE materials are treated with low-temperature plasma of some inert gases to generate carbon - The cleavage of fluorine or carbon-carbon bonds generates a large number of free radicals to increase the surface free energy of PTFE and improve its wettability and adhesion; PTFE is immersed in molten potassium acetate and treated at a suitable temperature to form a certain activity The active layer of PTFE; PTFE is heated in a certain proportion of sodium hydroxide and dipropylene melamine mixture to improve its surface activity; PTFE can form a glueable active layer after corona treatment of certain strength and time. (b), chemical corrosion modification: PTFE can be treated with certain chemical reagents to improve its surface activity. These chemical reagents can be ammonia solution of sodium metal, sodium naphthalene tetrahydrofuran solution, alkali metal amalgam, pentacarbonyl iron solution, etc. (c) Surface deposition modification: PTFE is immersed in a colloidal solution of some metal hydroxides, so that colloidal particles are deposited on the surface of PTFE, thereby increasing its wettability, improving its surface activity, and being easy to compound with other materials . The above surface modification methods are mainly suitable for PTFE films, and the modified films are widely used in the design and manufacture of chemical anti-corrosion linings, sealing products and lubricating devices.

2. Filling modification

At present, filled PTFE products are PTFE resin products with large output. By filling PTFE resin with different fillers such as inorganic, metal and organic polymers, the pressure resistance, wear resistance and cooling performance of PTFE are improved. These fillers are required to withstand the sintering temperature of PTFE, not to react with PTFE, to have a certain particle size, and to improve some physical and chemical properties of PTFE. It is worth noting that in foreign countries, PTFE filling technology is completed by PTFE resin manufacturers, while in my country, it is completed by processing and production enterprises.

Filling materials mainly include: inorganic filling materials, mainly glass fiber, graphite, molybdenum disulfide and carbon fiber, etc.; metal filling materials, usually iron, copper, lead, molybdenum, tungsten, silver and other metals and their oxides to fill PTFE, Especially copper and its alloys are commonly used; the organic filling materials are mainly organic fibers and high molecular polymers.

3. Blending modification

Blending modification mainly uses the excellent characteristics of PTFE to alloy some resins, and the current research and application prospects are promising, such as PTFE/PA, PTFE/POM, PTFE/PC, PTFE/PI, PTFE/PPO, PTFE/PEEK , PTFE/PPS, PTFE/PES and other alloy products emerge in an endless stream.

PTFE modified polyoxymethylene (POM): POM has excellent mechanical, chemical and electrical properties and is widely used in automobiles, electronics, precision machinery and building materials. In China, a series of POM/PTFE blends with different PTFE contents have been developed by the cold pressing-hot sintering process, which can significantly improve the friction and wear properties, toughness, creep resistance and appearance; The compatibilized and modified POM is extruded and granulated to obtain alloy pellets, which improves the friction and wear properties of the modified POM. The improvement mechanism lies in the formation of PTFE transfer film. Various POMs are prepared by mechanical blending abroad. /PTFE blend, that is, POM is blended with PTFE, PTFE coated with coupling agent, chemically treated PTFE, etc. Strong adhesion and excellent performance.