[Chemical Knowledge]：Manufacturing method and process of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) is a kind of high-performance fluoroplastic, with excellent chemical corrosion resistance, high temperature resistance, low temperature resistance, wear resistance, non-stick properties, is widely used in chemical industry, machinery, electronics, medicine and other fields. In the field of chemical production raw materials, the manufacturing methods of polytetrafluoroethylene mainly include suspension polymerization, emulsion polymerization and solution polymerization. This article will introduce the manufacturing method of polytetrafluoroethylene in detail.

1. suspension polymerization

suspension polymerization is one of the most commonly used methods for the preparation of polytetrafluoroethylene. The principle of this method is that polytetrafluoroethylene monomer (TFE) is subjected to a free radical polymerization reaction in an aqueous medium through the action of an initiator to generate polytetrafluoroethylene particles. Polytetrafluoroethylene prepared by suspension polymerization has the advantages of uniform particle size, smooth surface and high density. The process flow of

suspension polymerization mainly includes monomer preparation, initiator preparation, polymerization reaction, aging, washing, drying and other steps. The specific operation steps are as follows:

1. Monomer preparation: a certain amount of TFE monomer is added into the reaction kettle, and a certain amount of deionized water and dispersant are added at the same time, and the mixture is stirred evenly.
2. Preparation of initiator: Add the initiator to an appropriate amount of deionized water and stir evenly.
3. Polymerization: The initiator solution is added to the monomer solution, stirred evenly, and oxygen is introduced to carry out free radical polymerization. During the reaction, it is necessary to control the reaction temperature and pressure while maintaining the stirring speed to ensure uniform particle size of the polymer particles formed.
4. Maturation: After the reaction is completed, the mixture in the reactor is allowed to stand for a period of time to volatilize unreacted monomers.
5. Washing: The polymer particles after aging were washed with deionized water several times to remove residual dispersant and unreacted monomer.
6. Drying: The washed polymer particles are dried to obtain the final polytetrafluoroethylene product.

2. emulsion polymerization

emulsion polymerization is to add TFE monomer, water, emulsifier, etc. into the reaction kettle, through the action of the initiator, under the action of the emulsifier to form an emulsion, and then carry out the polymerization reaction to prepare polytetrafluoroethylene. Polytetrafluoroethylene prepared by emulsion polymerization has the advantages of small particle size, uniform distribution and high surface activity. The process flow of

emulsion polymerization mainly includes monomer preparation, emulsifier preparation, initiator preparation, polymerization reaction, emulsion breaking, washing, drying and other steps. The specific operation steps are as follows:

1. Monomer preparation: a certain amount of TFE monomer is added into the reaction kettle, and a certain amount of water and emulsifier are added at the same time, and the mixture is stirred evenly.
2. Emulsifier preparation: Add the emulsifier to the appropriate amount of water and stir well.
3. Initiator preparation: Add the initiator to an appropriate amount of water and stir evenly.
4. Polymerization: The initiator solution is added to the monomer emulsion to start the polymerization. It is necessary to control the reaction temperature and stirring speed during the reaction to ensure that the generated polymer particles are uniform in size.
5. Demulsification: After the reaction is completed, a demulsifier is added to break the emulsion and the polymer particles are precipitated.
6. Washing: The precipitate was washed multiple times with deionized water to remove residual emulsifier and unreacted monomer.
7. Drying: The washed polymer particles are dried to obtain the final polytetrafluoroethylene product.

3. Solution Polymerization

Solution polymerization is a process in which TFE monomer and initiator are added to an organic solvent for polymerization to produce polytetrafluoroethylene. Polytetrafluoroethylene prepared by solution polymerization has the advantages of high molecular weight and narrow molecular weight distribution, but the production cost is high. The process flow of

solution polymerization mainly includes monomer preparation, initiator preparation, polymerization reaction, precipitation, washing, drying and other steps. The specific operation steps are as follows:

1. Monomer preparation: A certain amount of TFE monomer is added into an organic solvent, and stirred evenly.
2. Preparation of initiator: Add the initiator to an appropriate amount of organic solvent and stir evenly.
3. Polymerization: The initiator solution is added to the monomer solution to start the polymerization. It is necessary to control the reaction temperature and stirring speed during the reaction to ensure that the molecular weight distribution of the produced polymer is uniform.
4. Precipitation: At the end of the reaction, the polymer solution was added to a large volume of deionized water to precipitate the polymer.
5. Washing: The precipitate was washed multiple times with deionized water to remove residual organic solvent and unreacted monomers.
6. Drying: The washed polymer particles are dried to obtain the final polytetrafluoroethylene product.

In short, the manufacturing methods of polytetrafluoroethylene mainly include suspension polymerization, emulsion polymerization and solution polymerization. Different methods have different advantages and disadvantages and scope of application, according to the specific production needs and conditions to choose the appropriate method for production.