Tianjin Tiansu Binhai Fluoroplastic Film Rod Sheet

Date:2022/8/18 8:57:16 /Read: /Source:本站

Tianjin Tiansu Binhai Fluoroplastic Film Rod Sheet http://www.tjtsjt.net//

Expanded PTFE molding process

 The molding of expanded PTFE is done in two stages. In the first stage, the PTFE bulk resin and the lubricating additive are mixed in a certain proportion. After a certain period of time, it is preformed, and then the paste is extruded into a longitudinally arranged fibrous preform, which is dried to remove additives; in the second stage, high-speed stretching is performed at a temperature below the melting point of PTFE, and then the The expanded polytetrafluoroethylene product can be obtained by heat-setting the stretched polytetrafluoroethylene semi-finished product at the temperature of the melting point. The process flow is as follows:

        (1) Mixing The polytetrafluoroethylene resin and the extrusion aid are mixed uniformly according to a certain mass ratio. Using dispersing resin, it has good fiber-forming properties, and the cohesion between particles is low, and the molecular chain will be arranged along the long axis of the particles after a small shearing action, forming linear crystals. Adding extrusion aid can increase the adhesion between particles, reduce the friction between resin particles and between resin and container, and improve processing performance. Extrusion aids are usually available in petroleum ether, toluene, acetone, kerosene, paraffin and the like.

        (2) Preforming Press the mixture into a blank with the same shape as the film cavity of the pusher.

        (3) Pushing Put the green body into the film cavity of the pusher and push it to obtain a bar at the push port.

        (4) Calendering rolls are used to calender the bar to obtain a strip of desired width and thickness.

        (5) Drying The tape is heated and dried to remove the extrusion aid on the tape to obtain a polytetrafluoroethylene film.

        (6) Expansion The polytetrafluoroethylene film is rapidly stretched, and the stretching temperature should be controlled between the glass transition temperature (115° C.) and the melting point (327° C.) of the polytetrafluoroethylene. Because the polymer chain has enough vitality when it is higher than the glass transition temperature, it can be pulled apart from the random group, straightened, and then moved with each other. When the temperature is higher than the melting point, the PTFE particles have melted and become A dense whole destroys the original folded shape of the fiber bundles of the particles, and it is difficult to be pulled apart.

  (7) Styling Put the expanded polytetrafluoroethylene film on the template, then put it into the mold towel, and integrate it by heating and pressure. The shaping process needs to be heated to above the melting point (327°C) at a certain heating rate , and then hold it for a period of time under a certain temperature and a certain stress to make the network structure formed after stretching the same. This process needs to be carried out under a certain stress, otherwise the fibers will shrink during the heat treatment process.

        Simple process flow chart: (dispersed polytetrafluoroethylene resin + lubricating extrusion aid) - mixing - pre-forming. Pushing-calendering-drying-expanding to shape.

        In the above process, the PTFE resin grade, stretching ratio, heating rate, and heat setting temperature are the main factors affecting the performance of the product.

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