Extrusion process of PTFE insulated wire

Ptfe is one of the types of fluorine plastic, used for processing and insulation layer, as a result of ptfe in melting point 327 ℃, and higher than the melting point 360 ℃ using disposable push extrusion sintering molding methods, process is more complex, process quality control involves many factors, once the control is not good, can make the extrusion process to or appear all sorts of quality problem; Once the extrusion and sintering are not successful, it will cause the material part or all scrap, ptfe price is expensive, so it has caused a big waste. Therefore, it is necessary to control the extrusion process of ptfe reasonably, comprehensively and effectively, which is a necessary condition to ensure product quality and reduce waste.

Based on the application and processing practice of ptfe material in electric wires and cables and the practical experience, the paper gives a brief overview of ptfe insulation extrusion process, hoping to help production technicians to make correct selection and control in ptfe extrusion process.

Technological process：                                                                                   

1. Sieve F4 powder    

                                                         

Ptfe powder is the powder particles after polymerization, soft, strength is very small, when in packaging container stored easily by weight or turbulence vibration in transit in the cluster, blending uneven phenomenon, so before mixing must adopt certain specifications of the mesh screen to sieve of ptfe powder, filter out larger knot cooking starch material, the specifications of the mesh screen in 8 and 12 mesh is advisable. If the agglomeration is serious, the powder should be placed in a lower temperature, after a period of time, if the agglomeration shows signs of loosening, then screening. The powder should be stored in a low temperature environment, and should be handled gently in the process of handling, so as to avoid severe agglomeration of ptfe powder and it cannot be used. In addition, environmental hygiene should be ensured and impurities or dust should not be mixed into ptfe powder. Due to the strong electrostatic adsorption of ptfe powder, it is easy to adsorb air or small impurities and dust around, so to keep the environment clean without dust, the packaging container surface should be clean before opening the cover

2. Toner or pulp treatment

When insulation needs coloring for identification, a certain proportion of toner or slurry should be added to ptfe powder. Toner is after fine grinding of high temperature resistant organic or inorganic pigment powder, easy to absorb moisture, agglomeration, so in advance should be heated treatment, remove moisture, and screen, filter out the larger particles. Generally, 180 and 200 mesh screen specifications are appropriate. If the screen screen is smaller than 180 mesh, then the pigment particles after filtering are larger, which is not conducive to the insulation performance of the insulation layer. The screen mesh is more than 200 mesh. Although the insulation performance of insulation layer is guaranteed, it is difficult to filter. Color paste is a mixture of toner and oily liquid, toner in oily liquid suspension state, but stationary for a period of time will precipitate, so before use should be shaken and mixed, so that the precipitate toner particles evenly suspended in oily liquid for use.

3. The ingredients

Batching is an important preparation before mixing, according to the ratio of polytetrafluoroethylene powder and extrusion aid, or color powder or color paste ready, after the mixture.

There are more kinds of extruder, such as yan 20 aviation gasoline, toluene, petroleum ether, or other volatile solvent oil, organic solvent, etc., different extruder volatilization speed is different, according to the actual situation of the equipment, extrusion speed to choose the appropriate extruder. The extrusion assistant volatilizes too fast, although it can shorten the drying time and improve the extrusion speed, it requires strict operation time for the preparation before extrusion, and the preparation operation time should not be too long, otherwise the extrusion assistant of the blank will be ineffective due to excessive volatilization .Extruder is too slow to evaporate, and although there may be sufficient preparation time, the drying time must be extended or higher requirements for the equipment capacity are required. The proportion of extruder should be 18% and 23%, and should be adjusted according to the specifications of the conductor, insulation layer thickness, extrusion speed and extrusion pressure. Generally, the wire specification is larger, the insulation thickness is thicker, the extrusion speed is faster, the compression is smaller, the proportion of the extruder can be appropriately small; On the contrary, the wire specification is smaller, insulation thickness is thinner, extrusion speed is slower, compression is larger, the proportion of the extruder can be appropriately larger.

Toners cost less and are still commonly used today. Using pigments to dye, teflon insulation dispersion in toner as paste, toner and ptfe powder is dry mixing, and toner additives and relatively little, easy to cause mixing cluster, dispersion is poor, is not easy to mix, will lead to serious existence chromatism different part of insulation, so its size as small as possible when choosing toner requirements, general imported toner quality is better. In the toner mixing, should choose the pigment powder temperature tolerance above 400 ℃, otherwise after high temperature sintering (sintering temperature generally basic in 350, 400 ℃) may appear the product fading phenomenon. Generally, inorganic pigments have good high-temperature resistance, while organic pigments have poor high-temperature resistance. Therefore, the use of inorganic pigments as toner is more reliable, but its environmental protection is poor. The matching ratio of toner is generally not more than] %, in the actual production can be according to the type of toner, toner quality, color requirements, insulation layer thickness, etc.

Although the cost of color paste is high, it is conducive to the uniformity of the mixture and is an ideal choice, which can effectively ensure product quality, simple operation, high efficiency and less waste. When mixing the color paste, the color paste can be added to the extrusion aid and premixed evenly. Due to the relatively large amount of extruder, it is wet mixed with ptfe powder, so there is no problem of toner agglomeration, and the dispersion is very good, it is easy to mix evenly. The proportion of color paste is generally between 0.3% and 0.5 ‰, with 3 ‰ being the majority. Only a few special cases require the proportion of 0.5 ‰.When the insulation layer edge layer thickness is relatively thin, the proportion of color paste should be appropriately increased by 0.1%, 0.2.

4. The mixture

Mixing is to mix polytetrafluoroethylene powder with extrusion aid, or color powder or color paste evenly, to ensure that the extrusion insulation lubrication and color uniformity. In order to facilitate uniform mixing, the volume of general mixing bottle (wide mouth bottle) is appropriate to 4, 5 liters, the loading quality is about 800, 1 000 g, the loading volume accounts for about 2/3 of the mixing bottle volume is good, so there is enough space for mixing.

The natural color mixture (mainly used to extrude the insulation of radio frequency cable) does not need to add toner. When mixing, put ptfe powder into mixing bottle first. Used in to make people try not to contact with mixing bottle of bottle wall, in person to squeeze aid available clean sheet tool will gently mixing in a bottle the center of the surface of ptfe powder to bottle wall, make its surface center to form a depth of about 2, 3 c of conical hole, then people directly used in a certain proportion in the taper hole; After that, the mixing bottle shall be capped and strictly sealed to prevent the extruder from volatilizing. Firstly, the mixing bottle shall be shaken and mixed manually for no less than 5 minutes, and then the mixing bottle shall be placed on the mixing machine to swing and roll for more than 30 minutes until the mixing is even.

5. Compact

The effect of pressing (material) billet is to press loose porous polytetrafluoroethylene powder into a relatively compact material billet, eliminating the pores and air contained in it for extruding use. Generally should be in the environment of 20 ℃ above the blank pressing, will be homogenized powder slowly pour into the pressure cylinder cylinder, at the same time should ensure that the heart rod and pressure cylinder cylinder concentric, and gently shake the pressure cylinder in the material surface, and then add pressure cover on it. The pressure should be appropriate, too much or too little will affect the extrusion quality. If the pressure of the blank is too large, the extruder is easy to be overpressed, and the lubrication performance during extrusion is reduced, the extrusion pressure is increased, and the shear stress of the material is larger, leading to excessive fibrosis, which is not conducive to the stability of the outside diameter of the extrusion insulation, and the shrinkage rate of insulation sintering is larger, which is also easy to cause insulation cracking.

6. Squeeze out

The preparation work for ptfe insulation extrusion mainly includes selection of compression ratio, preheating and heating of extrusion cylinder and die, adjustment of needle gap between die sleeve and die core, charging blank, conductor inspection, conductor piercing, adjustment of thread tension, combination sealing of machine head and extrusion cylinder, etc., which will be introduced in the following.

The compression ratio of different brands of ptfe powder during extrusion is also different. the proper compression ratio should be determined according to the properties of ptfe powder to ensure the process performance and quality during extrusion. Extrusion compression ratio refers to the ratio between the annular area of the extrusion die and the annular area of the blank. Generally, extruder cylinders are divided into three sizes: small, medium and large. The diameter of small cylinder is about 38 mm, medium cylinder is about 50 mm, and large cylinder is about 65 mm.In the actual production, the specifications of the extruder cylinder should be selected according to the sectional area of the extruder insulation layer.

In order to maintain a stable temperature of the blank and facilitate the volatilization of the extruder after extrusion, the extrusion cylinder and mold should be preheated properly. The preheating temperature of the extrusion cylinder should be 30 or 40 ℃, and the preheating temperature of the mold should be 50 or 60 ℃.

The extrusion should be according to the specifications of the corresponding matching mold and according to the location of the assembly, and the mold sleeve bearing line neck population and needle tube between the distance (gap) to the appropriate position. Too large or too small clearance will affect the quality of the extruded insulation layer. If the gap is too small, the velocity of extrusion of ptfe material to the outside of the mold will be accelerated, and the material will be excessively cut, leading to excessive fibrosis, resulting in the decrease of the transverse strength of insulation layer, the product is prone to longitudinal cracking or internal cracks of insulation, and the insulation and conductor coating is not tight (there is "loose cover").The gap is too large, will make ptfe material to the outside of the mold extrusion velocity slow down, material pressure on the conductor increases, often occur extrusion instability or cause conductor compression rolling and produce "pine" problem, and the conductor can not pass through the needle plug phenomenon.

Application of vacuum sintering and tunnel furnace sintering

In terms of power chip assembly, the existing main problems are: the assembled chips, due to the bottom of the hollow area is more, thermal resistance is bigger, work have a lot of heat when not through the effective way to transfer to the shell, resulting in junction temperature is exorbitant, while working reliability, reduce the life of the power device, even 1 thermal breakdown failure by junction temperature is too high. In recent years, with the rapid development of the electronics industry, vacuum sintering process has been widely used, and the voidage rate, thermal resistance, connection strength and reliability have been significantly improved, which may become one of the key technologies for power chip assembly.

1.     The sintering mechanism

Two different metals can form eutectic alloys in proportion at temperatures well below their respective melting points. This lower temperature is their low eutectic point. Sintering process is in between the chip and carrier (substrate) or pipe shell of a metal sheet (solder), in a certain vacuum or protective atmosphere heating to the alloy melting point make it melt, melt into liquid alloy infiltrating the whole chip welding metal and carrier surface of substrate, solder welding the weld metal and carrier with the metal physical and chemical reaction, generate a certain amount of intermetallic compound, and then, in the process of cooled to below the melting point of solder and intermetallic compound chip and carrier welded together, form good ohmic contact, thus complete the chip and carrier welding drawing.

In this paper, the tunnel sintering furnace and vacuum sintering furnace are selected respectively to weld the chip and DBC board, and the cavity rate of the two technologies is compared and analyzed through X-ray scanning, which proves that the actual effect of vacuum sintering process is better.

2.  Sintering process test of tunnel furnace

The use of tunnel furnace heating, in DBC board and chip add solder piece, when the solder piece by heat melting, with the help of it on DBC board coated copper part of mutual melting and the formation of metal compound, achieve new alloy surface will chip and DBC board solidly welded together. The test results are as follows:

FIG. 1 (a) shows the control curve of sintering temperature in the tunnel furnace. FIG. 1 (b) is the reflow furnace in FIG. 1, which is a multi-purpose "cold wall" process welding furnace. Under the condition of observation 1 < a), X-ray scan diagram of the back side of the chip completed by the tunnel sintering furnace and benefit window are provided on the top cover of the chamber. Through it, real-time recording of each stage of the sintering process can be achieved. Then, the cavity rate of the chip after sintering can be obtained by the computer as 8, 7%.Adjust the temperature curve in time.

3.  Vacuum sintering furnace process test

Internally open vacuum pump to extract air (vacuum degree 1 × 10 × 5 mbar);Then the vacuum sintering furnace used in the charge test is a kind of welding nitrogen dilution residual air with the function of rapid annealing. When the vacuum reaches its limit and there is basically no residual gas in the chamber, the filled hydrogen begins to heat up. At high temperature using hydrogen reduction, DBC board, solder and chip reduction, remove oxide, improve the penetration rate of solder. After a period of high temperature, the chip has been welded to the DBC board, but there are still many bubbles on the welding surface. After the vacuum pump is started for the third time, residual bubbles on the welding surface can be extracted as much as possible after a period of time, thus reducing the voids in the chip welding and the voids rate.

The whole process can be programmed and controlled by computer. The time, gas flow and temperature of each program section can be precisely set, and the operation is convenient. In addition, because of the use of solder sheet, do not have flux welding, so that the sintered chip can be directly sent to the next process, reducing the cleaning link, reduce production costs. The test results are as follows:

FIG. 2 (a) shows the control curve of vacuum sintering temperature. FIG. 2 (b) is the X-ray scan diagram of the back of the chip completed by vacuum sintering under the conditions of FIG. 2 (). The computer shows that the cavity rate of the chip after sintering is only 0 coincidence 2%.

4.      Interpretation of result

By analyzing and comparing the results of the above two different sintering processes, it can be concluded that:

1)     Sintering time: vacuum sintering time is only 1/4 of the time of tunnel sintering furnace, which greatly improves the production efficiency.

2)     Sintering cavity rate: the vacuum sintering cavity rate (0· 52%) is only 6% of the tunnel sintering furnace cavity rate (8 · 7%), which reduces by 16 times and significantly improves the effective welding area.

From the comparison of the above test results, it can be seen that vacuum sintering can obtain higher quality sintering results than tunnel furnace sintering process, and the production efficiency and product reliability can be connected, so that the sintered chips can be directly sent to the next process, reducing the cleaning link and reducing the production cost. The test results are as follows:

To significant improvement; And the whole sintering process is precisely controlled by computer programming to avoid errors caused by human operation.

5.     Conclusion

With the continuous improvement of semiconductor manufacturing process, vacuum sintering process and related equipment will be updated and improved day by day, gaining wider recognition and market application. However, there are many factors that affect the quality of power chip sintering, which need to be further recognized and explored.

[---This text and text source network, if there is infringement, please contact delete, thank you!---]

Powder Metallurgy Pressed Sintering Integrative Furnace

The physical and mechanical properties of the metal powder can be obtained by sintering. For multicomponent liquid phase sintering, the sintering temperature is generally lower than that of refractory metals, but higher than that of fusible metals.

1.    Powder metallurgy sintering process

After the powder forming process, sintering and post-treatment (such as finishing) are required. Sintering and finishing are generally done separately. That is, sintering finished, and then put on the press finishing. For multicomponent liquid phase sintering, this separate process makes the quality of products difficult to be guaranteed. The sintering temperature is low, the fusible metal is not melted, and the bonding enhancement effect is not obtained. High sintering temperature, fusible metal melting, and easy loss and re-accumulation, will also affect the quality of products. The ideal method is to press in the furnace immediately when the sintering temperature is reached. The following describes the structural principles of some pressurized and sintered integrated equipment used in aviation powder metallurgy for high temperature sealing materials of copper or steel in the range of 500 ~ 900 ℃, pressing in the range of 50 ~ 2 000 kg and controlling accuracy of ±1.5% of the set value.

In order to achieve pressure sintering of powder metallurgy, the following problems need to be solved in the equipment:

(1)  when the products are heated in the reducing atmosphere, the sealing of the furnace cover and the furnace tank must be ensured first, and the gas cannot be leaked. When the furnace tank is expanded by heat, when the tank body extends, there should be expansion and contraction space, can not be gored;

(2)  pressurization is carried out in the 900 ℃ high temperature furnace tank, and the extrusion mechanism is set in the furnace tank. Firstly, the high temperature strength of metal materials should be considered, and secondly, the sealing of sports pairs should be considered. They cannot produce creep, cannot be bitten to death, and the friction resistance should not be too large;

(3)  the melting point of copper alloy is generally more than 750 ℃. Once the sintering temperature reaches, the pressure should be followed up immediately, and the pressure should be given as much as it is set, followed up dynamically, and the pressure should be kept stable.

(4)  the heating process and pressurizing process are controlled by PLC (programmable control) to ensure the repeatability of sintering process.

2.  Equipment structure features

The invention relates to a steel - based product with copper alloy powder as adhesive, pressurized and sintering furnace.

In this furnace, there is a fixed pressure head of metal embedded in the furnace body, furnace frame, elevator, furnace cover trolley, furnace tank and pressure cover. The upper end of the fixed pressure head is connected with the beam of the furnace body, and only the pressure plane inside the furnace is exposed. The furnace body, furnace frame, beam and fixed pressure head are rigidly connected. When the bottom plate of the furnace frame is welded with the ground embedded iron, a rigid frame member is formed. The vertical distance between the bearing plane of the upper constant pressure head and the ground is fixed.

The elevator is set in the pit below the furnace. The upper plane of the elevator is welded with two tracks, flush with the ground track, to facilitate the access of the furnace cover trolley. The surrounding plane of the furnace cover trolley is equipped with two sealing grooves, the inner ring is sand seal, and the outer ring is liquid seal (emulsion).There are N pressure springs in the liquid seal tank, which can carry the weight of the furnace.

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.

An sintering oven used for producing ptfe

A used in the production of teflon sintering oven, drying oven, including housing, the top surface of box body is set with solar tank and vent, solar-thermal box right side set solar monitoring device, before the end of box set oven door, the right side of box body is provided with electric control cabinet, electric control cabinet set a timing device, temperature control device, inlet valve, exhaust valve and switch button, box body including shell and inner cavity, and setting of between shell and inner cavity has a heat preservation cotton, inner chamber set on two cooling board, two fans and purification device, casing set inside the rack and put tray, put aside content disc set for both have cooling hole, The bottom center of the shelf plate is provided with a connecting disk. The utility model has a simple structure and strong practicability. 

Through the combined heating method of solar energy and electric energy, not only the styling effect is improved, but also the service life is extended, the yield rate is increased, the energy consumption is reduced, the cost is saved, and the comprehensive utilization efficiency is improved.

Sintering oven used in the production of ptfe, whose character is: the Sintering oven including enclosure, as described in the top surface of box body is set with solar tank and vent, solar-thermal box right side set solar monitoring device, in the right side of the hole is located in the solar energy collection hot box, the box body front end face of the oven door, oven door includes the first oven door and the oven door and the oven door and described the oven door all set door the mouth and observation, the right side of box body is provided with electric control cabinet, electric control cabinet set timing device, temperature control device, Air intake valve and exhaust valve and switch button, temperature control device is set on the first heating button and the second heating button, switch the power button, button, and explosion-proof fan button button, box includes shell and inner cavity, with mentioned lumen between shell and a heat preservation cotton, inner chamber set on two cooling board, two fans and purification device, both on the heating panel Settings have mica heat sink, purification plant is located in between two mentioned fan, box set inside the rack and put tray, the bottom of the rack set wheels, put aside content disc set for both have cooling hole, Plate center set up at the bottom of the shelf are connecting disk, disk and a partition at connections, on the other side of the baffle plate and described shelf plate connected, put aside material plate is divided into four equal, connecting the center of the disk set has a hole, the bottom of the box body set with wheel groove HeJinKong, wheel to match the wheel groove and the stated, air inlet connected with the outside world.

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)

Introduction to ptfe teflon pipes

Ptfe teflon tube extrusion machine is divided into many kinds, exactly say ptfe tube forming process has push and pressure method, extrusion method, hydraulic method, welding method, winding method, etc., which is mainly push and pressure method.Generally dispersed PTFE resin with particle size of 500 microns and apparent density of 0.45g/ml ~ 0.55g/ml is adopted.The small diameter tube chooses the compression quite big resin, the medium and large diameter tube chooses the compression quite small resin.Extruder usually choose 200 and 260 solvent oil.PTFE thermal shrinkage tube, PTFE spiral tube, PTFE steel wire reinforced hydraulic tube and so on can be produced by the secondary processing of PTFE tube.

1.1 common ptfe teflon pipe

Ptfe ordinary tube is made of ptfe dispersion resin at room temperature with organic solvent as extruder, and then through drying and sintering.According to the size of the pipe diameter can be divided into two types of ordinary pipe and micro pipe.Ordinary tube inner diameter > 4mm, micro tube inner diameter ≤4mm.

Typical formula for PTFE tube production:

Dispersed PTFE resin: 100 (weight)

Extruder: 18 ~ 24

Production process:

PTFE, extruder - mixing - pushing - pressing - drying - sintering - cooling - products.

Production process parameters:

Mixing: temperature ≤19 ℃, time 10min ~ 20min, mixed at 25 ℃ ~ 30 ℃ for more than 24h.

Blank: compression rate is about 50mm/ min, pressure is 0 ~ 3MPa.

Pushing pressure: the cavity temperature is 30 ℃ ~ 50 ℃, and the die temperature is 50 ℃ ~ 60 ℃.

Drying: under 210 ℃,2h ~ 3h

Sintering: batch sintering, temperature rise rate of 60 ℃/ h,375 ℃±5 ℃ insulation for 4h.

Continuous sintering, dry area 100 ℃ ~ 250 ℃, preheating area 250 ℃ ~ 330 ℃, sintering area 380 ℃ ~ 420 ℃, cooling area less than 300 ℃.

Main equipment: mixing machine, preforming machine, vertical pushing press, drying and sintering furnace.

USES: as insulation and fluid conduit.

1.2 polytetrafluoroethylene heat-shrinkable tube

PTFE thermal shrinkable tube has the property of being heat-shrinkable, so it can be tightly coated on the surface of other workpieces, making the workpieces resistant to corrosion, electrical insulation and viscosity.Widely used in electrical, chemical, mechanical, printing and other industries.The maximum shrinkage of PTFE shrink tubes is reported to be more than 75%.

It is processed by disperse PTFE resin. The principle is that PTFE is subjected to stress during processing and produces forced high-elastic deformation, which is reversible and freezes at low temperature. If the forced high-elastic deformation is reheated, it will gradually disappear and return to the original state.

Typical formula for PTFE thermal shrinkable tube production:

Disperse PTFE resin 100 (weight)

Extruder 20 ~ 22

Production process:

PTFE resin, extrusion aid → mixing → storage → pre-molding → pushing and pressing → drying → sintering → cooling → heat treatment → blowing → cooling → product.

Production process parameters:

The front part is the same as ordinary PTFE tube.

Heat treatment: the quenching process of the dried and sintered pipes after further full sintering at high temperature, the temperature is 390 ℃±2 ℃, and the coolant is -5 ℃.

Blowing: at 310 ℃ or so, fill the compressed gas below 0198MPa, the blowing rate is 200% ~ 400%.

Main equipment: blowing machine, other PTFE tube and the same.

1.3 ptfe teflon steel wire reinforced hydraulic pipe

The common PTFE pipe will break under the pressure of about 40kg/ cm2. When it is combined with steel wire, the pressure resistance will be greatly improved. The maximum working pressure abroad reaches 700kg/ cm2.The results show that the compressive strength and pulse strength of the hose are related not only to the steel wire strength but also to the weaving Angle.When the braiding Angle is 54°44 "for single-layer braiding, the steel wire does not extend under internal pressure, the length and diameter of the hose do not change, and the pressure resistance is the best.

When used as hose for hydraulic system in aviation industry, in order to prevent electrostatic breakdown of inner tube caused by hydraulic oil flow, trace conductive carbon black should be added in the manufacture of PTFE inner tube.However, it was found that adding carbon black could not completely prevent electrostatic discharge from passing through the tube wall and increase the gap.

In the 1960s, Attas manufactured composite tubes, in which the inner layer of the tubes was a uniform mixture of conductive carbon black and PTFE, and the outer layer of the tubes was pure PTFE.This form of tube body layer has axial conductivity, so it can not only eliminate static electricity, but also prevent seepage.

The process:

Inner resin (including conductive carbon black), outer resin → blank → pushing → drying → cooling → testing → weaving → fitting joints → testing.

PTFE steel wire composite hose is mainly used in aircraft hydraulic system, air conditioning system, fuel system, lubricating oil system.In civil industry, it is suitable for soft connection of hydraulic pressure, steam pressure and steam transportation in rubber, plastic, pharmacy, clothing, shipbuilding, automobile, machine tool, motor, diesel engine and paper making industries.

1.4 ptfe teflon spiral tube

PTFE spiral tube, also known as PTFE flexible hose, has not only all the excellent properties of PTFE, but also flexible properties.At present, there are two kinds of PTFE spiral tube and chemical fiber, stainless steel wire and plastic coated glass fiber woven reinforcement.

It is made of PTFE through secondary processing. The process is that PTFE thin-walled tube continuously rotates forward through a combination mold with a temperature of 270 ℃ ~ 280 ℃ at a certain speed.

It is mainly used for the inlet and outlet pipes of the shock parts such as the soft connection dislocation connection, serpentine pipes, pump engines and so on.Used for shielding cable and protecting cable sleeve of aircraft engine.