Application of laser particle size analyzer in polytetrafluoroethylene particle size detection

1.Polytetrafluoroethylene and its applications

Polytetrafluoroethylene, abbreviated as teflon, is generally called "non-stick coating" or "easy-to-clean material. This material is acid and alkali resistant, resistant to various organic solvents, and is almost insoluble in all solvents. At the same time, PTFE has the characteristics of high temperature resistance and its friction coefficient is extremely low, so it can not only provide lubrication, but also become an ideal coating for easy cleaning of the inner layer of water pipes.

Polytetrafluoroethylene is known as the "King of Plastics." Roy Plunkett, the father of fluororesin, began researching substitutes for Freon at DuPont in the United States in 1936. They collected part of the tetrafluoroethylene and stored it in cylinders to prepare for the second They conducted the next experiment the next day, but when they opened the pressure reducing valve of the cylinder the next day, no gas escaped. They thought it was a gas leak, but when they weighed the cylinder, they found that the cylinder had not lost weight. They sawed open the cylinder and found a large amount of white powder, which was polytetrafluoroethylene.

Its emergence has solved many problems in chemical industry, petroleum, pharmaceutical and other fields. PTFE seals, gaskets, and gaskets. PTFE seals, gaskets, and gaskets are molded from suspension polymerized PTFE resin. Compared with other plastics, PTFE is chemically resistant and has been widely used as sealing and filling materials.

The dispersion can be used as an insulating impregnation liquid for various materials and as an anti-corrosion coating on the surfaces of metal, glass, and ceramics. Various PTFE rings, PTFE gaskets, PTFE packing, etc. are widely used in various types of anti-corrosion pipeline flange seals. In addition, it can also be used for spinning polytetrafluoroethylene fiber - fluoronon (foreign trade name is Teflon).

2. Development of PTFE in China

    The production and research of polytetrafluoroethylene (PTFE) in China started early, but due to various factors restricting the production scale and the overall level of process technology is relatively low. China's PTFE has basically relied on its own strength to gradually develop from small to large, especially since the 1980s, it has developed rapidly. Economic-scale production equipment has now begun to be formed, and monomer production technology has reached a new level. In 1991, China's total PTFE installation capacity was 3,040 tons/year, with an output of 2,529 tons; in 1992, the installation capacity was 4,540 tons/year, with an output of 3,074 tons. Since then, Jinan Chemical Plant has used its own developed technology to build a 1,000-ton PTFE production device. The electrochemical plant of Shanghai Chlor-Alkali Chemical Co., Ltd. built a 1,200-ton/year PTFE production unit in June 1993 and officially put it into production, increasing its PTFE production capacity to 2,000 tons/year.

3. Differences in particle size between polytetrafluoroethylene micropowder and fine powder

    PTFE micro powder is a dispersed PTFE micro powder obtained by telomerization reaction of PTFE. The average particle size is less than 5μm, the specific surface is greater than 10m2/g, the friction coefficient is 0.06~0.07, it has good lubricity and can be well dispersed in many materials. PTFE ultrafine powder can be used alone as a solid lubricant, or as an additive in plastics, rubber, coatings, inks, lubricating oils, greases, etc. When mixed with plastic or rubber, various typical powder processing methods can be used, such as blending, etc., and the addition amount is 5 to 20%. Adding polytetrafluoroethylene micropowder to oil and grease can reduce the friction coefficient. Just add 5% A few, can extend the life of lubricating oil. Its organic solvent dispersion can also be used as a release agent. PTFE micropowder is mainly used as an additive. Can be added to other plastics, inks, lubricants, coatings, or used directly as a lubricant.

The purity of PTFE micropowder products is 100%, the molecular weight is less than 10,000, and the PTFE micropowder series with a particle size of 0.5-15μm not only maintains all the original excellent properties of PTFE, but also has many unique properties: such as No self-agglomeration, no electrostatic effect, good compatibility, low molecular weight, good dispersion, high self-lubricating, significantly reduced friction coefficient, etc.

     PTFE fine powder is generally processed into solid finished products by molding process. PTFE fine powder can be filled with other reinforcing agents. Generally, fine powder is used as the base material to fill with copper powder, carbon fiber, graphite, glass fiber, etc., of course. Fine powder can also be made directly into finished products.

PTFE fine powder is composed of particles (primary particles) with an average particle size of 0.05~1μm, an apparent density of 0.52~0.70g/ml, and a standard specific gravity (SSG) of 2.14~2.23 , polytetrafluoroethylene fine powder with an average secondary particle diameter of 100 to 1000 μm and excellent fluidity, a dripping inhibitor using this fine powder, a flame retardant resin composition containing this fine powder, and a flame retardant resin composition containing this fine powder. The dust suppressing composition of polytetrafluoroethylene fine powder.

A kind of polytetrafluoroethylene fine powder with excellent powder flowability, consisting of particles (primary particles) with an average particle size of 0.05 ~ 1μm, an apparent density of 0.52 ~ 0.70g/ml, and a standard specific gravity (SSG ) is 2.14~2.2 3. The average particle size of secondary particles is 100~1000μm.

PTFE medium particle size is a general-purpose molding resin. It is obtained by suspension polymerization and crushing of PTFE monomer. The average particle size is about 130 μm. It has a wide range of high and low temperature applications and outstanding comprehensive performance. It is an ideal choice for national defense and civilian applications. Excellent engineering materials for industry. The main features are high molecular weight, high tensile strength, low standard relative density, and low thermal instability index. Medium-grained PTFE is generally processed into solid finished products through a molding process. Medium-grained PTFE is generally made into finished products alone without filling reinforcing agents.

    Medium-grained PTFE is suitable for processing sealing rings, rings, films, plates, rods, gaskets, bearings, etc. It can process turning plates and pre-sintered materials, and first-class products can be used as electrical materials.