Study on Sintering of Ptfe

From the perspective of the three factors that determine the properties of PTFE products -- molecular weight, crystallinity and voidage, the voidage is mainly affected by the preforming pressure, and the molecular weight and crystallinity all change with the different sintering conditions. Therefore, sintering process conditions play a decisive role in the final properties of products such as density, hardness, permeability and mechanical properties.

Wang ping found that the sintering process of PTFE was affected by the rising and falling speed, sintering temperature and sintering time. The larger the product, the slower the speed of rising and cooling, the longer the sintering time. The sintering temperature of suspension resin is higher than that of dispersion resin. The sintering temperature of pure material products is higher than that of filled products. In general, the rate of warming is faster than the rate of cooling. In the same sintering furnace, pure material and filling products cannot be mixed; Products with different sintering conditions cannot be mixed. Products of different raw materials cannot be mixed. Taking the production of 3-layer molded circular plate with diameter of 1 m, thickness of 20 mm, double layer as pure ptfe and middle layer as filled ptfe as an example, the compression strength, bending strength, hardness and other mechanical properties of the circular laminated plate produced by this technology have been greatly improved.

Liu xianlan studied the forming process characteristics, forming method and mold design characteristics of PTFE, analyzed the defects and causes of PTFE products produced by cold pressing and sintering, and put forward the treatment methods. PTFE can be molded by a variety of preforming processes, such as molding, extrusion, hydraulic molding, push molding and secondary processing, and then sintered to the final product.PTFE molding is mostly made of suspended resin. When the thickness of sheet is less than 1.5mm, disperse resin is used. Its technological process: resin - sieve (suspension resin after pounding, loose, and the 20 mesh mesh sieve) - press (PTFE powder loading the mould under pressure from 20 to 35 MPa, after press compaction forming) - sintering (in 370 ~ 380 "C temperature sintering in sintering furnace) - moulded products (under free state within the mold or after cooling to finalize the design as required by the board, rods, tubes, gaskets and packing products, etc.).Hydraulic method is also called the equilibrium method or rubber molding in its operating process is: put rubber bag in die - connected to the water pump, filling the water swell the rubber bag into a cylindrical - resin evenly join between bag and external mold mold closing - continue to gradually increase the water pressure, water filling up to 12 ~ 13 mpa pressure maintaining 30 min: after water - decompression, ripping, sintering, cooling is the use of bright and clean appearance. Push is also called the paste extrusion molding, 20 ~ 30 mesh sieve dispersion resin and organic liquid (such as toluene, petroleum ether, the solvent oil) mixture 1:5 paste mixture, preloading into thick wall cylinder billet, push into the compressor cylinder, heating, with a plunger push molding, after drying in the 360 ~ 380 ° C temperature sintering, after cooling products have strong push tube, rod, etc.Extrusion molding can be divided into two types: screw extrusion and plunger extrusion. The pre-sintered resin after crushing and sifted is added to the material cylinder. Through screw rotation or reciprocating push of plunger, the raw material is transported to the extruder at the same time of compaction.

Wang ping studied the forming process of PTFE foam material. Suspended polytetrafluoroethylene is used as raw material, and condensed cyclic aromatic hydrocarbons are selected as pore-forming agent. After mixing, preforming products are preformed and sintered. At the initial stage of sintering, drying process is adopted to make pore-forming agent escape, and then resintering stage is entered. Foam materials with different dielectric constants can be prepared in different proportions to meet various requirements.

Chen xu et al. conducted compression test and sintering test on PTFE, discussed the relationship between density, compression strength and compression modulus, and analyzed the compression strength of specimens under different sintering processes, and obtained more appropriate molding pressure and sintering process. The results showed that the compression strength of PTFE decreased with the increase of pressing pressure, and the compression modulus increased with the increase of pressing pressure. The molding pressure was 27.5mpa, sintering temperature was 380 C, and the insulation time was 4h.

In order to overcome the disadvantages of pure ptfe, such as poor abrasion resistance and large thermal expansion coefficient, Raytheon studied the bronze-filled particles in ptfe, and expanded the application scope of ptfe. The conventional warm pressing molding of ptfe is characterized by long cycle, poor performance, low dimensional accuracy and smoothness, while the warm pressing molding in this study has fewer working procedures, short cycle and significantly improved mechanical properties.

The molding process of the press automatic Moulding Machine

Is moulded plastic processing and molding the application in the city one of the oldest technology. It has a mature production technology, equipment and mold is simple, easy to forming large products, can use multiple modes to improve the production of small parts, etc, in machinery, electronics, transportation and daily life, and many other fields has been widely used.

The market will often see a lot of kinds of Press Moulding Machine, for example: Polymer/PTFE Bush press Automatic Moulding Machine, Polymer/PTFE Flange press Automatic Moulding Machine, Polymer/PTFE gasket automatic Moulding Machine, Semi-automatic Molding Machine and so on.

Molding is widely used in the following fields:

Electrical: insulator, switch box, electrical equipment housing, insulation tools, wiring board, etc.

Automobile: lamp shade, front and rear bumper, battery bracket, engine soundproof board, etc.

Railway: window frame of vehicle, toilet components, seats, table tops, siding and roof of carriage, etc.

Construction: water tank, bath products, door panels, purification tank, building template, etc.

Bathroom: bathtub, integral bathroom equipment, integrated wash basin, etc.

And other areas of industry and agriculture.

Molding technology is a method of putting quantitative molding materials (powder, granular or fibrous plastic) into the metal mold and forming products under the action of temperature and pressure. During the molding process, heat and pressure are required to melt (or plasticize) the molding material, fill the mold cavity with flow, and make the resin solidify. The principle is that the process of pressurizing, shaping and heating depends on the closure of the heated mold.

Moulding Machine technology is the oldest molding method in plastic processing technology. Because of its long history, the molding technology has been quite mature, at present in thermosetting plastics and some thermoplastic plastics (fluoroplastics, uhmwpe, polyimide, etc.) processing is still the most widely used and the main position of the molding method. Moulded thermosetting plastic, placed in the cavity of the thermosetting plastic under the action of heat, first changed from solid to melt, melt flow under pressure with the shape of the cavity and cavity has given, as the crosslinking reaction, resin molecular weight increased, the curing degree rise, moulding material viscosity increase gradually and becomes solid, finally becomes demoulding products. Thermoplastic plastic mold pressure, in the previous stage of the situation and thermosetting Plastic the same, but because there is no cross-linking reaction, so in the flow of full cavity, the mold must be cooled to make its molten plastic into a solid with a constant strength can be demodulated into products. Because thermoplastic plastic mold pressing mold needs to alternately heating and cooling, production cycle is long, so thermoplastic products generally choose injection molding method more economic, only in the mold larger plane of Plastic products or because of the flow of thermoplastic plastic injection molding method is difficult to use molding.

In the mold press material filled with the mold cavity flow process, not only the resin flow, the reinforcement material also to flow, so the mold press molding process molding pressure is higher than other process methods, belongs to the high pressure molding. Therefore, it needs not only the hydraulic press which can control the pressure, but also the high strength, high precision and high temperature resistant metal die.

Production process and application of ptfe film

Ptfe film processing equipment will use a Isostatic Moulding Press Machine, Isostatic Moulding Press Machine production bar, and then sintering, finally using a Skiving Machine for Skiving.

Ptfe films are mainly divided into two types: microporous film and turning film.The biggest difference between the two is the permeability of microporous membrane, which is produced by biaxial stretching.Turning film is cut out of the lathe, it does not breathe.

I do not know about turning film, know that it should be used on the seal more.We're going to talk about microporous membranes.

Polytetrafluoroethylene (ptfe) microporous film is made of polytetrafluoroethylene resin particles, which is expanded and stretched to form a microporous film. It can be divided into the following categories:

1. Air filtration membrane

Polytetrafluoroethylene membranes can be used for atmospheric dust removal, air purification and so on the membrane pore size can be controlled 0.2 um, porosity can reach more than 88%, and the needle felt, mechanism of cloth, non-woven fabric, glass fiber and other filter material with surface phase composite filtering performance of coated fabric, PTFE coated filter material has high peel strength, air volume, uniform pore size distribution, etc.As a dust bag or fold type dust removal filter cartridge installed within the dust removal equipment, will be promptly and efficiently calculated intercept with micron ultra fine dust, dust removal efficiency can reach more than 99.99%, the service life for three years, ventilation rate of up to 3-6 m/min, is currently the world's most advanced air filtration material, all kinds of vacuum cleaners, air filter, air purification equipment, the best choice for high efficiency air filter, etc.

Technical parameters are as follows:

Thickness: 5 um - 15 um

Air permeability: 80-100l /㎡•s

Width: 1800 mm or less

Resistance: pa 80 or less

Efficiency: 99.99%

2. Waterproof and moisture-permeable microporous membrane

Ptfe waterproof moisture permeable microporous membrane is made and approved by a special process the bidirectional tensile membrane surface per square inch can reach billions of a microporous, each pore diameter (0.5 to 0.1 um um) is less than the minimum water molecules in the mist of the minimum value (20 UN um - 100), the diameter greater than the water vapor molecules (0.0004 to 0.0003 um um), the water vapor through the water, and cannot pass, take advantage of the microporous structure can achieve excellent waterproof and moisture permeable function;In addition, because the hole is extremely small and longitudinal irregular bending arrangement, so that the wind can not pass through, and thus has good wind protection and heat preservation characteristics.Since the advent of the membrane through continuous improvement, special treatment on the PTFE film, its fastness and durability greatly improved, after composite with other fabrics, widely used in the greenwood clothing, medical clothing, leisure clothing, fire control, chemical protective, antivirus, flooding operation, such as special protective clothing, outdoor sports clothing, shoes and hats, gloves and other accessories as well as sleeping bags, tents and other materials

Technical parameters are as follows:

Thickness: um 20-50 um

Moisture permeability: 16000g/㎡•24hr

Hydrostatic pressure: 6000mm

Extreme uv resistance: 97 highest

Width: 1700 mm or less

G: 5-10 g/m2

3. teflon bubble point film

It with polytetrafluoroethylene (ptfe) as raw material, after puffing stretch forming a kind of microporous membrane, the membrane with a special process combined with on all kinds of fabric and base material, become a new type of filtration material, the membrane pore size is small, about 0.2 to 0.5 mu m, uniform distribution, porosity, while maintain the air circulation, can filter all of the dust particles, including bacteria, achieve the goal of advanced purification and ventilation, it is widely used in pharmaceutical, biochemical, microelectronics and laboratory consumables, etc.

Technical parameters:

Thickness width bubble point

1600mm ≥1kg/cm2 (5.3m/s 127Pa)

What is the PFA

I. What is the PFA?

The English name of PFA is Polyfluoroalkoxy, or tetrafluoroethylene perfluoroalkoxyethylene ether copolymer (perfluoroalkylate, soluble polytetrafluoroethylene).PFA resin is relatively new fluoroplastic that can be processed by melting. PFA, FEP and PTFE have similar chemical properties, but FEP can only be used below 200 degrees, and PTFE cannot be injected. 【this resource was first published by China fluoroplastics network.】

1. Specific gravity: 2.13-2.167g/cubic centimeter

2. Molding shrinkage rate :3.1-7.7%

3. Molding temperature: 350-400℃

4. The melting point of PFA is about 580F and the density is 2.13-2.16g /cc (g/ cubic centimeter).

II. Features and main USES of PFA

PFA, commonly known as fusible PTFE, is the crown of fluoroplastics with various properties and USES similar to FEP.Widely used in semiconductor industry, as well as medical, chemical corrosion protection, automotive and other fields.

PFA products include granular products for molding and extrusion, and powdery products for rotating molding and coating.Its semi-finished products are membrane, plate, rod and pipe.PFA resin distributed in the American market includes Teflon of DUPOut, Neoflon of Daikin, Hthen of Ansimont and Hostafl of HOechst Celanese.

1. Main USES of PFA:

(1). Suitable for making corrosion resistant parts, wear - resistant parts, seals, insulation parts and medical equipment parts.

(2). High temperature wire, cable insulation layer, anti-corrosion equipment, sealing materials, pump valve bushing, and chemical containers.

2. Molding performance

(1). Crystallization material, small moisture absorption.Products may be processed by the usual thermoplastic processing method.

(2). Poor liquidity, easy decomposition, decomposition produced corrosion gas.It is advisable to strictly control the molding temperature not to exceed 475 degrees, the mold should be heated to 150-200 degrees, the pouring system should have little resistance to the material flow.

(3). Translucent granule, injection molding, extrusion molding.Forming temperature 350-400 degrees, 475 degrees above easy to cause color or bubble.And notice that it's harder to get out of the mold.

(4). Because the molten material on the metal corrosion effect, long-term production, the mold needs to electroplate chromium treatment.

3. Material performance

1. PFA is a copolymer of a small amount of perfluoropropyl perfluoroethylene ether and polytetrafluoroethylene.The melt bond is increased, the solution viscosity is decreased, and the performance is not changed compared with ptfe.The resin can be processed into products directly by ordinary thermoplastic molding.

2, long-term use temperature -80- 260 degrees, excellent chemical corrosion resistance, corrosion resistance to all chemicals, friction coefficient in the lowest plastic, and very good electrical performance, its electrical insulation is not affected by temperature, "plastic king" said.

3. Its chemical resistance is similar to ptfe and better than vinylidene fluoride.

4. Its creep resistance and compression strength are better than ptfe, with high tensile strength and elongation up to 100-300%.Good dielectric property, excellent radiation resistance.

5, non-toxic: with physiological inertia, can be implanted in the human body.

PLC control system of Polymer extruder

The PLC control system of extruder has been widely used in many fields such as cemented carbide, pharmaceutical, food processing and mechanical processing. Extrusion technology is widely used because it can obtain products with uniform density in the direction of extension and high production efficiency. Currently on the market for some extrusion machine, such as: Polymer Teflon Rod extruder, PTFE UHMWPE tube extruder,etc. extrusion machine while there are almost one hundred years of history, but with the rapid development of information technology, all kinds of information technology in the layer, especially the detection technology, PLC control technology,microelectronics technology and modern control technology development puts forward new challenge on the extrusion machine. It is very important to study the application of PLC control system because the control system is developed in high efficiency, high speed and high precision.

With the rapid development of manufacturing industry, industrial aluminum profiles have been widely used in various high-tech industries, such as aviation, bullet trains, ships and so on. The forming technology of metal aluminum profile mainly includes extrusion, forging and calendering. According to the extrusion molding process, such as the whole process will use the Polymer Teflon bar extruder, PTFE UHMWPE tube extruder, MouldingMachine, PTFE Gaskets Press Moulding Machine, Cutting Machine, PTFE Skiving Machine, Dry Grinder, cleaning machine, vibration screen, automatic feeding machine. The control system of extruder is emphasized. This set of control system combines PLC, MES and upper computer to realize online intelligent management, visual management, process control, process analysis and product traceability of production process.

Isothermal extrusion speed control is an important method for high efficiency and high quality production in rare metal processing enterprises. Different raw materials (Polymer, PTFE, Teflon, UHMWPE), extruder extruded products are different, such as color, shape, density, etc. According to the characteristics of the treasure titanium 25M extrusion machine equipment, combined with the actual production condition, titanium simulation of isothermal extrusion speed control system, put forward to simulate the isothermal extrusion speed control system architecture and function of system implementation, is developed based on industrial PC + PLC titanium simulation of isothermal extrusion speed control system, using the prediction algorithm to build the extrusion speed prediction model. The system can achieve isothermal extrusion of titanium, shorten the extrusion time, and operate reliably.