The problem of particulate pollution is becoming more and more serious, bag dust removal technology has been widely used, and the use and demand of dust removal bags are increasing day by day. It is understood that currently in the field of industrial dust removal, the main battlefield of governance is basically delineated in thermal power, metallurgy, cement, etc., and the mainstream governance technologies are electrostatic dust removal and bag dust removal. Comparing these dust removal technologies, bag dust removal is the most widely used and fastest growing dust removal technology because of its stable and efficient dust removal function in a wide range of particle sizes and high dust removal efficiency for PM2.5. Dust bag is the core component of bag filter, the variety, quality and technical level of bag filter are important conditions for the successful application and rapid development of bag filter. The development and progress of the bag filter is in the final analysis the development and progress of the dust bag. Many domestic scholars are devoted to the research on the dust removal efficiency of dust filter bags, but they have ignored the recycling of dust collector bags after use. The amount of filter material used in the bag filter every year corresponds to how many waste filter bags will be replaced and waited for treatment. The problem of recycling waste filter bags is urgent.

1. Radiation cracking method

The radiation pyrolysis recovery method is suitable for pure PTFE products, because the additives in PTFE are generally glass fiber, molybdenum disulfide, copper powder, etc. Glass fibers will change color when exposed to high-energy rays. The particle size of the added copper powder is generally 40 μm, and high-energy rays cannot further refine the particles to 10-20 μm. Therefore, the radiation cracking method is suitable for defective products, residual materials and scraps in the processing of pure PTFE.

Under the action of accelerated electron rays or high-energy gamma rays, the radiation dose is not less than 100KGy, the carbon-fluorine bond is destroyed, the PTFE molecular chain is broken, and a small molecular weight PTFE product is obtained. Due to the decrease in molecular weight, PTFE becomes very brittle. By jet pulverization or grinding, PTFE ultrafine powder with a particle size of 1 to 20 μm can be obtained.

The radiation cracking process has low requirements on PTFE materials, and under certain atmospheric conditions, high-energy rays act on PTFE products. In the packaging step of the process flow, different products will be obtained due to the different atmospheres used. Degradation under inert gas conditions can yield perfluoroalkanes and perfluoroolefins. It is degraded in the air environment to obtain purer PTFE or its modified products. It is degraded under oxygen conditions to obtain perfluoric acid derivatives. In industrial production, considering the cost and use, degradation under air conditions is generally adopted.

The molecular weight of PTFE will be changed by irradiation, but its melting point will be less affected. The increase of the radiation dose used in the radiation will reduce the molar mass of the PTFE molecule and slightly decrease the melting point. When the radiation dose starts to increase, the molar mass changes obviously, but when the radiation dose reaches 50KGy, the change tends to be gentle. At the same time, the increase of the radiation dose will make the particle size of the final ultrafine powder smaller. The study found that radiation causes PTFE to undergo cross-linking reaction, and the elongation at break and tensile strength of PTFE decrease.

The PTFE ultrafine powder obtained by the radiation method not only has the advantages of acid resistance, alkali resistance, oxidant resistance, and operating temperature of -200 ~ 260 ° C, but also has good dispersibility and can be blended with other materials, but the cohesion is poor. Widely used in coatings, inks, explosives, rocket stationary fuel and other fillers. There are three main application areas:

(1) Used as an additive for coatings: widely used in food, electrical appliances, textiles, packaging and other sectors. Studies have shown that adding 60% of PTFE ultrafine powder to the coating can improve the anti-corrosion, anti-sticking and reduce the coefficient of friction, and improve the performance of the coating.

(2) Used as an additive for printing ink: By adding a certain mass percentage of PTFE powder to the printed ink, the smoothness and gloss of the printed matter can be significantly improved.

(3) Modifier for polymer materials: Add 10%~20% powder to polycarbonate, polyoxymethylene, polyamide, polyphenylene sulfide, silicone rubber, styrene-butadiene rubber and other polymers respectively, which can obviously Improve the flame retardant and wear resistance of finished products.