Preparation method and application of polytetrafluoroethylene stretched film

A preparation method of a modified polytetrafluoroethylene stretched film, comprising the following steps:

• (1) uniformly mixing a modified polytetrafluoroethylene emulsion and a lubricant, and carrying out extrusion calendaring;
• and
• (2) longitudinally stretching and then transversely stretching at a first temperature, and sintering and curing at a second temperature for 5-15 minutes after stretching is completed, to obtain the modified polytetrafluoroethylene stretched film;
• wherein the lubricant in the step (1) is polytetrafluoroethylene (PTFE), and usage amount of the lubricant is 10-15% of mass of the modified polytetrafluoroethylene emulsion;
• and the first temperature is 210-230° C., and the second temperature is 350-370° C.;
• the modified polytetrafluoroethylene emulsion comprises the following raw materials in parts by weight:
• 0.5-2 parts of an ammonium salt polymer dispersant, 0.2-1 part of an emulsifier, 1-1.5 parts of a 2-isocyanatoethyl acrylate (AOI) modified monomer, 0.5-3 parts of an initiator, 40-60 parts of a tetrafluoroethylene monomer, and 30-60 parts of water;
• a preparation method of the modified polytetrafluoroethylene emulsion comprises the following steps:
• (1.1) adding the dispersant, the emulsifier and deionized water into a high-pressure emulsification reactor, stirring, heating up to 40-60° C., and increasing system pressure to 3-4 MPa;
• and
• (1.2) respectively adding the tetrafluoroethylene monomer, the AOI modified monomer, and the initiator into the high-pressure emulsification reactor, heating up and reacting for 2-4 h to obtain the modified polytetrafluoroethylene emulsion;
• a structure of the ammonium salt polymer dispersant is as follows:
• wherein x is an integer of 2-5, y is an integer of 5-8, and * is a connection site of a chemical bond;
• and
• a preparation method of the ammonium salt polymer dispersant comprises the following steps:
• (1.1.1) adding a first solvent into a reactor, heating up to a third temperature, and dropwise adding perfluorohexanol acrylate, acrylic acid, and a first initiator into the reactor, and keeping the third temperature to react for 2-4 hours;
• and
• (1.1.2) adding diethanolamine into a product obtained in the step (1.1.1) for reaction, removing the first solvent after the reaction ends to obtain the ammonium salt polymer dispersant;
• a structure of the AOI modified monomer is as follows:
• wherein m is an integer of 1-2, n is an integer of 10-20, and * is a connection site of a chemical bond;
• and
• a preparation method of the AOI modified monomer comprises the following steps:
• (1.2.1) adding a second solvent into a reactor, heating up to a fourth temperature, and dropwise adding the perfluorohexanol acrylate, hydroxyethyl acrylate, and the initiator into the reactor, and keeping the fourth temperature for 2-4 hours after dropwise adding is completed;
• and
• (1.2.2) adding AOI into a product obtained in step (1.2.1) for reaction, removing the second solvent after the reaction ends, to obtain the AOI modified monomer.