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Discuss temperature process of PFA tube extruder with Dan Kai

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Discuss temperature process of PFA tube extruder with Dan Kai

  • Categories:News
  • Author:PFA tube lady
  • Origin:DANKAI
  • Time of issue:2003-05-16 10:05
  • Views:

Discuss temperature process of PFA tube extruder with Dan Kai

  • Categories:News
  • Author:PFA tube lady
  • Origin:DANKAI
  • Time of issue:2003-05-16 10:05
  • Views:

Conical single screw extruder is used for the extrusion production of PFA pipeline. The whole process can be roughly divided into three areas: heating, constant temperature and heat preservation. The heating and constant temperature are mainly located inside the extruder, and are divided into two relatively independent and interrelated parts with the exhaust hole as the boundary. The insulated area process is composed of a flow core, an extrusion die and an extrusion die.

There are two kinds of heat sources in the extrusion process of PFA tube, one is the external heat generated by the electric heater, the other is the shear, calendering and friction of the PFA raw material by the single screw, and the PFA itself is divided into the middle friction generated by the internal heat. The two heat sources play different roles in different parts of extrusion. Temperature control equipment only controls the external heat. There is internal heat and strong shear action, but it does not exceed the compression section required by the plasticization of raw materials and the melting section of key tail gas, which is also relatively stable and easy to control. Shear is relatively weak, mainly rely on external heat heating, but external heat can not consider the material plasticization requirements of the feeding section (external heat configuration is particularly prominent extruder with low); The measuring section where the shear has exceeded the material plasticization requirement is generally not controlled by the temperature control equipment. Therefore, in the whole temperature control process of extrusion, feeding section, measurement is the key and difficult point of temperature control.

Figure 1: Extruder 1    Source: Dan Kai

1. Temperature of the feed part: the feed part transmits heat to the screw cylinder through the electric heater. The temperature displayed is the temperature of the screw cylinder, rather than the temperature of the material. The temperature of the material is usually much lower than the indicated temperature. When the material just enters the extruder through the feed screw, the temperature is only about 30℃-40℃, and there is a large gap between the temperature rise of the material from the shear belt generated by the screw and the plasticization (glass) temperature. At the same time, the material will pass through the exhaust hole after the compression section, and the material needs to complete the glass viscous flow transformation process in the heating area. Requirements are basically orange peel, no powdery substance, and closely covered on the surface of the screw groove, so as not to be extracted or blocked by the vacuum of the exhaust hole. Therefore, the function of the feed section focuses on external heating, and the temperature should be set as high as possible so that the electric heating ring can provide sufficient external heating for the material. At this point, electric heaters are often turned on and off without stopping working.

As the material enters the feed section, there is still some time before the die extrusion. In addition, in order to prevent the material from bridging the feed port or sticking the wall inside the machine, the setting temperature should not be too high. Temperatures above 270 ° C should be displayed. Although the set temperature of the feed section is low, such as the set temperature of about 250℃, or even lower, the product can be produced to meet the internal quality standards. However, because the supply of external heat is relatively small, excessive reliance on shear heat to improve the temperature of the molten body, and the wear of the screw barrel will affect the service life of the extruder screw barrel, so the gains outweigh the losses. In the long-term maintenance of extrusion equipment, we have observed that only one or two years of use (some even less than a year), the screw will produce serious wear. A lot of practice has proved that under the premise of constant feed and extrusion speed and set temperature in the measurement section, increasing the set temperature of the feeding section can effectively reduce the temperature difference between the displayed temperature and set temperature in the measurement section, which fully shows that the temperature of the feeding section plays a role in regulating shear heat to a certain extent.

Figure 2: Extruder 2    Source: Dan Kai

2, compression temperature: the material enters the compression part, has a large shear effect, and under the action of the screw shear force rapidly heating up. Set high temperature, help to reduce the viscosity of the material, speed up the flow, such as the feeding part, can reduce the harm of shear heat.

3. Melting part of the temperature: the melting part of the material is basically melted, melting pressure due to the threaded groove product changes (general compression ratio is less than 1) suddenly drops, can give full play to the role of constant temperature exhaust, set the temperature and compression part remain the same or slightly higher, help to prevent melt cooling, melt temperature will also drop due to melt pressure.

There are many sources of temperature for PFA tube extrusion. Shenzhen Dankai in the production of PFA tube extrusion machine, a comprehensive introduction of many years of PFA tube production experience, reasonable set screw length-diameter ratio, reasonable partition. After the purchase of extruder, customers produce thick and uniform products, can quickly occupy the market.

ShenZhen DanKai Technology Co.,ltd. is an intelligent manufacturing enterprise specializing in the R & D, production, sales and service of FEP, PFA, PTFE,PVDF and other fluoroplastic tube, bar, sheet and film products as well as other insulating materials.

The company has a senior research and development team of international standards and imported fluorine plastic products production line, some fluorine plastic products passed ISO9001, SGS, FDA certification.

The main products are: ① pipe: PTFE polytetrafluoroethylene pipe, FEP pipe, PFA pipe, PVDF pipe; ② Heat-shrinkable tubes: PTFE heat-shrinkable tubes, FEP heat-shrinkable tubes, PFA heat-shrinkable tubes, PVDF heat-shrinkable tubes; ③ Plate and rod films: PTFE plate and rod film, FEP plate and rod film, PFA plate and rod film, PVDF plate and rod film; ④ Insulating materials: silica gel, PE, PVC, UPE, etc.; ⑤ Special class: PFA inlet joint, spiral pipe, spring pipe, rotary cut pipe, welding rod, tee, straight, gasket, joint, taper rod, flaring pipe, sealing pipe, braided pipe, corrugated pipe, etc. At the same time can be customized processing production of various specifications of fluorine plastic products.

This article by the teflon tube little sister original, welcome to pay attention to, take you together long knowledge!

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