Application of PTFE material in wire and cable industry

 PTFE has excellent electrical insulation properties. The dielectric loss tangent tga and relative permittivity Er change very little from the power frequency to 109 Hz. From room temperature to 300°C, the dielectric loss tangent tga of PTFE changes very little.

The relative permittivity Er decreases with increasing temperature. The insulation resistivity of PTFE is relatively high, its volume resistivity Pv is generally greater than 1015Ω·m, and the surface resistivity Ps is generally greater than 1016Ω. Even if it is immersed in water for a long time, the change is not significant, and the temperature change is not large.

Impedance of PTFE raw material tape insulated radio frequency cable

Attenuation is one of the most important parameters of radio frequency cables. It reflects the loss of electromagnetic energy transmitted along the cable. The greater the attenuation of the cable, the more serious the loss of the transmission signal and the worse the transmission efficiency of the cable. In order to improve The transmission efficiency of radio frequency cables should be as low as possible. The attenuation of coaxial radio frequency cables is mainly caused by conductor attenuation and medium attenuation.

After PTFE raw tape replaces solid PTFE insulation, it can greatly reduce the attenuation of radio frequency cables, which can be reduced by 15~30%. However, due to the high price of PTFE raw tape, its price is about 3 to 4 times that of PTFE.

Increasing the manufacturing cost of the cable, it can only be used in a special environment where the outer diameter of the cable is small, the attenuation is relatively low, and the temperature resistance level is high. With the continuous development of fluoroplastic production and processing technology, the price of PTFE raw tape will gradually decrease, and it will be more widely used in the wire and cable industry.

Application of PTFE in Batteries

The application of PTFE in batteries is a 60% solid PTFE emulsion. Mainly used in power batteries such as nickel-metal hydride, nickel-cadmium, lead acid, and fuel cells. The network formed by the fibrillation of PTFE emulsion can contain active substances well, but if the single addition amount is too large, it will produce a large impedance and affect the charge and discharge performance.

Experiments have proved that the compounding of PTFE emulsion and sodium carboxymethyl cellulose can make up for this shortcoming. The carboxymethyl cellulose solution produces water evaporation during the forming process of the pole piece, which increases the porosity of the pole piece, increases the true specific surface area of ​​the electrode, and effectively reduces the electrochemical polarization of the electrode, thereby increasing the electrode’s Discharge capacity. Experiments show that the dosage of 60% PTFE emulsion is 1.5~2.5 parts. The CMC concentration ratio is stable at 2%.

Application of PTFE in Capacitors

The application of PTFE in capacitors is a 60% solid PTFE emulsion. Mainly used for super capacitors. Electrochemical capacitor (referred to as electrochemical capacitor) is a new type of energy storage device between traditional capacitors and batteries. It has the advantages of high specific power, good reversibility, and long cycle life. It is usually used to meet instantaneous high-power requirements to compensate for the lack of high-current discharge of the battery. ).

Now supercapacitors are generally multi-water systems, one is environmental protection, the other is large capacity, one is low cost, and the process control is relatively simple. After mixing the active material, conductive agent, binder, thickener (CMC) and 60% PTFE emulsion, it is directly applied to the nickel foam. It is better to add 60% PTFE emulsion to the two components. PTFE emulsion is a dispersion of PTFE, polymerized into an aqueous dispersion, its solid content is about 60% of PTFE, and it is stabilized by a nonionic surfactant. It has excellent heat resistance, cold resistance and abrasion resistance, as well as excellent electrical insulation properties, and is not affected by temperature and frequency.

In addition, it also has the characteristics of non-stickiness, non-absorption, non-burning, etc., and fibrosis occurs after high temperature. The formed network structure can be uniformly coated with active materials, and the effect is very good. In the state of repeated oxygen release from the positive electrode, the anti-oxidation effect is good.

Application of PTFE in non-stick cookware

 

For the convenience of cooking, many families have used “non-stick pan”, but it is not always clear what material is coated in the pan. In fact, this layer of material is PTFE known as the “Plastic King”. Polytetrafluoroethylene has many advantages that ordinary plastics can’t compare: it will not become brittle in liquid air, and will not become soft in boiling water, and it can be used from low temperatures of -369.3°C to high temperatures of 250°C.

Its chemical stability exceeds that of glass, ceramics, stainless steel, as well as gold and platinum. What’s interesting is that because the surface of PTFE is smooth, the adhesion to any substance is very small, even the paste can not stick to it. Therefore, in the food industry, it is used as cakes and candy molds without even a little bit of flour or syrup.

The advent of non-stick pans has brought great convenience to people’s lives. After adopting “non-stick pans”, people don’t have to accidentally burn the pan when cooking meat or if the fish skin sticks to the wall when frying fish.

Because this non-stick pan is coated with a layer of polytetrafluoroethylene on the inner surface of the ordinary pan, it is made of excellent thermal, chemical and easy-to-clean properties of polytetrafluoroethylene. It will not stick to food, so it is deep. Welcomed by everyone.

However, PTFE starts to decompose slowly after being heated to 415°C, and the gas generated by the decomposition is toxic. Therefore, when using a non-stick pan, it cannot be dry-burned. The temperature must be kept below 250°C to be safe.

When consumers buy non-stick pans, they need to pay attention to whether the product is marked as free of PFOA and PFOS. If it is clearly marked, the product can be purchased with confidence. In addition, PTFE can work stably at 260 degrees Celsius for a long time, and the short-term temperature resistance can reach 327 degrees.

A comprehensive number of studies on polymer coatings for non-stick pans have shown that they may release trace amounts of perfluorinated compounds at high temperatures, but the possibility of release during cooking is unlikely. For example, boiling with salt water and water for 2 hours, or heating to 280 degrees with soybean oil, did not find typical decomposition and dissolution of perfluorinated compounds.

PTFE Applications on Medical Industry

PTFE Coating Applied on The Surface of Medical Equipments

• According to the mass percentage, 40-60 percent of PTFE emulsion, 0.5 percent of defoamer, 0.5 percent of wetting agent, 0.5 percent of flow agent and rest water are mixed to crank out PTFE hydrophilic paint applied to medical appliance;
• The PTFE hydrophilic paint applied to medical appliance is coated to positions needing to be coated on the medical appliance;
• Under the room temperature, after water content in the PTFE hydrophilic paint waiting for being applied to the medical appliance evaporates, the paint is solidified and sintered under a temperature of 120-350 DEG C, namely, the PTFE lubricating hydrophobic coating is formed on the medical appliance.

The application of e-PTFE in the medical

Expanded PTFE (expanded PTFE) is a new type of medical polymer material. It is made of PTFE resin by special processing methods such as stretching. It has a network structure formed by connecting fine fibers. These fine fibers Numerous pores are formed, so that the expanded PTFE can be bent at will, has good blood compatibility, and is resistant to biological aging. It is used to manufacture artificial blood vessels, heart patches and other medical products.

From a medical point of view, it is the most ideal substitute for biological tissue. Due to its special molecular structure, expanded polytetrafluoroethylene is an artificial material with extremely stable physical and chemical properties. At the same time, it has passed 6 million clinical applications for 40 years, including artificial blood vessels (replacement of human diseased arteries and veins), artificial There is no report of clinical rejection after implantation of various parts including dura mater and heart patch, which fully proves that the material has good biocompatibility.

Expanded polytetrafluoroethylene has become an important medical filler and is currently one of the most ideal materials for biological tissue substitutes.

Rhinoplasty Application

According to the specific characteristics of the nose, the expanded polytetrafluoroethylene is carved into an e-PTFE surgical patch, which is placed in the corresponding part of the nose to construct a nasal prosthesis bracket, thereby improving the shape of the nose, and practice indicates that the plastic surgery effect is good.

Especially in the most critical part of the back of the nose and the tip of the nose, implanted with elongated expanded polytetrafluoroethylene that has excellent compatibility with human tissues, and human tissue cells grow into the elongated expanded polytetrafluoroethylene micropores Inside, there will be no adverse reactions such as material movement, collapse or rejection, and at the same time it can prevent the reflection of light, making the facial shape after plastic surgery more natural and realistic.

Application in Heart Valve Surgery

The researchers first sewed a sheet of ultra-microporous expanded polytetrafluoroethylene material on a specific elastic stent to make a synthetic heart valve.

The test results show that the artificial mitral valve synthesized by expanded polytetrafluoroethylene can be completely opened and closed during the cycle of the cycle, and the chordae of each expanded polytetrafluoroethylene artificial mitral valve are in tension. The valves are tightly aligned between the large and small valves, with no visible gaps.

This indicates that the expanded polytetrafluoroethylene artificial mitral valve has good hydrodynamic properties and durability in vitro.

e-PTFE Has Also Successful in Other Body Parts' Medical Applications

Varicose veins of the lower extremities are a common occurrence in human surgery. With the promotion of expanded polytetrafluoroethylene in human medical treatment, researchers have used expanded polytetrafluoroethylene synthetic vascular sheets to perform superficial femoral vein valve annulus Very satisfactory results have been achieved in the treatment of primary deep venous valve insufficiency of the lower extremities.

PTFE Can Be Applied in Mechanical Engineering

 

1. Sliding rail

Sliding guide rails are often the installation foundation of metal cutting machine tools, medical equipment and many other systems and devices. The accuracy foundation and positioning foundation are an important part of the machine. In the machine tool manufacturing industry, most of the machine tool guide rail pairs use cast iron-cast iron, cast iron-quenched cast iron, cast iron-quenched steel, etc. However, due to its physical properties, the coefficient of friction between metals is large, it is not wear-resistant, and cannot work under dry friction. It crawls at low speeds and small displacements. This crawling affects machine tools, especially precision machine tools, and affects the feed accuracy and Repeat accuracy. When using filled PTFE guide rails, the low-speed stability of the machine tool is greatly improved.

Because the plastic guide rail has the feature of burying foreign objects, iron filings and sand particles can be embedded in the plastic, avoiding its own abrasion, preventing napping and scratching the metal surface, and can protect the bed guide. PTFE containing bronze powder and other fillers has excellent friction properties. After the transfer film is formed on the metal surface, the friction coefficient is greatly reduced, the load-bearing capacity of the transfer film is greatly improved, and the effective working life is also extended. If matched with a metal machine tool guide, the friction coefficient remains unchanged with the increase of sliding speed. Therefore, this kind of filled PTFE guide rail will not produce crawling phenomenon at low speed and micro feed, and it also has vibration absorption and cushioning properties. The friction coefficient of PTFE guide rail is 0.05 when dry friction, and 0.03 when there is oil lubrication.

No matter whether the machine tool guide has lubricating oil or not, its working movement is the same. When the PTFE guide rail needs to be repaired after it is worn out, the repair work is very labor-saving and can be interchanged, and it is easy to maintain the dimensional accuracy. Especially when the guide rail is damaged and needs to be repaired, it is better to use plastic for partial repair.

2. Friction parts

There are many PTFE friction parts commonly used in mechanical engineering, such as bearings, piston rings and gears. PTFE is an ideal material for piston rings and is widely used in air compressors and water compressors. PTFE piston ring acts as a compression ring to block liquid or gas. It is often used in occasions where lubricants or other harsh conditions cannot be used. If it is severely corrosive and has high safety requirements, it can greatly reduce the wear of the cylinder inner wall and repeated boring. The number of holes prolongs the service life of the cylinder.

Almost all piston rings play a hermetic role in reciprocating motion and start frequently. Therefore, the static friction coefficient is required to be small. Under small load, the static friction coefficient of PTFE is 25% to 75% lower than that of other materials. The larger the load, the more its superiority can be exerted. This has incomparable superiority in light starting and light reciprocating. As a result, it reduces energy consumption, reduces vibration and noise, and helps protect the environment.

At the same time, PTFE can be used as a motion transmission and power transmission component in industries such as textiles, printing and dyeing, paper making and food, which have a wide range of working conditions and a very harsh environment.

3. Seals

The use of PTFE film compounded on the surface of the rubber sealing material can improve the solvent resistance and medium resistance of the rubber seal, and the price is relatively low. It has been used for the sealing requirements of various mechanical occasions. Filled FE sealing material has excellent high and low temperature resistance, and is currently the main substitute for traditional asbestos gasket materials.

Carbon fiber reinforced PTFE sealing material has high strength, high modulus, fatigue resistance, creep resistance, high thermal conductivity, low thermal expansion coefficient and low friction coefficient. These comprehensive properties are unmatched by any kind of sealing material, and it is an ideal advanced sealing material.

4. Anticorrosive parts

Modified PTFE has good chemical stability to acid, alkali, and salt corrosive media. It can replace metal ceramics for anti-corrosion engineering. It is especially suitable for high temperature and strong corrosion situations, such as anti-corrosion equipment, pipelines and pipe fittings in chemical plants. Corrosive friction materials, valves, pumps, heat exchangers, porous plates and filter materials for strong corrosive media, linings and coatings for chemical equipment.

PTFE Rubber Bearing Plates Applied in Bridge Engineering Industry

 The PTFE rubber bearing plates have the characteristics of simple structure, low price, no maintenance, easy replacement, low building height, etc., so it is very popular and had been widely used in the field of the bridge engineering industry.

The PTFE rubber bearing plate is a layer of 1.5mm-3mm thick PTFE plate glued on the surface of the plate rubber bearing. In addition to the vertical rigidity and elastic deformation of ordinary plate rubber bearings, the ability to withstand vertical loads and adapt to beam end rotation, the use of low friction coefficient (μf≤0.08) between the PTFE plate and the stainless steel plate can make the bridge superstructure The horizontal displacement is not restricted.

Large-span bridges with spans greater than 30 meters, multi-span continuous beam bridges can be used as movable supports; continuous beam push, T-beam lateral movement and large equipment slip can be used as sliders.​ Due to the low coefficient of friction (μ≤0.03) between the PTFE plate and the stainless steel plate at the bottom of the beam, the horizontal displacement of the bridge superstructure can be unrestricted.

Advantages of PTFE rubber bearing plates:

1. Simple structure, convenient processing, less steel consumption, low cost, and convenient installation;

2. Reliable working performance, good elastic damping, can absorb the deformation of the upper structure in all directions, reduce the impact of dynamic loads on the bridge span structure and piers, and improve the bridge’s mechanical performance;

3. It has sufficient vertical stiffness to withstand vertical loads and has good elasticity to adapt to the rotation of the beam end; and has a large shear deformation to meet the horizontal displacement of the superstructure.

4. The PTFE rubber bearing plates are convenient to install, and directionality can be ignored;

5. The PTFE rubber bearing pads/plates hardly needs regular maintenance, reducing the maintenance workload;

Application of PTFE in Chemical Anticorrosion Industry

 In today’s industrialized countries, the annual economic loss caused by corrosion accounts for about 4% of the total national economic output. A considerable number of accidents in chemical production is caused by chemical reactions caused by equipment corrosion and medium leakage.

It can be seen that the damage caused by corrosion is serious and has attracted people’s attention. PTFE material overcomes the shortcomings of ordinary plastics such as poor corrosion resistance and has become the main corrosion-resistant material in the petroleum, chemical, textile and other industries.

Anti-corrosion performance of PTFE coating material:

• The highest operating temperature is 300℃.
• Continuous use temperature 260℃.
• The sintering temperature used for PTFE coating is 380～420℃.
• PTFE can only be used for a lining when used in corrosion protection, not suitable for coating.
• Very low coefficient of friction, good wear resistance, and excellent chemical stability.
• Corrosion resistance: PTFE is hardly corroded by chemicals and can protect the product from any kind of chemical corrosion.

Application of PTFE Microfiber Membrane in Chemical Industry

The PTFE microfiber membrane is prepared by a biaxial stretching process. It has a microstructure with interlaced fibers, forming a certain shape and size of pores, and has high porosity.

Therefore, it has excellent filtration performance, good air permeability and It can retain dust particles and is widely used in air filtration, medical and food filtration.

Preparation method of PTFE microfiber membrane

1. Melt stretching method

Melt-stretching method The melt-stretching method is to blend PTFE and co-extruding agent, heat and melt, extrude to form a sheet-like sample, and then heat-stretch to form a microporous film.

According to the different stretching directions, it is divided into unidirectional stretching and bidirectional stretching. The microporous structures of the products obtained by the two stretching methods are different: the pores of the PTFE microfiber membrane prepared by the uniaxial stretching method are oblong, and the pores of the PTFE microfiber membrane prepared by the biaxial stretching method are spherical.

2. Thermally induced phase separation method

Thermally induced phase separation is an emerging method for preparing microfiber membranes in recent years. In this method, PTFE is blended with some compounds, heated to dissolve PTFE in it to form a uniform system, phase separation occurs during the cooling process, and the product obtained by cooling is stretched to obtain a PTFE microfiber membrane.

The microfiber membrane prepared by thermally induced phase separation is thinner, the pore size is smaller, and the micropore distribution is more uniform. However, the thermally induced phase separation method requires a large amount of solvents, which will cause environmental pollution, and the process is relatively complicated, so industrial production has not yet been realized.

PTFE microfiber membrane has stable properties and low surface energy, and can be used as a microfiltration membrane in industry. When the PTFE microfiber membrane is used in the dust collector of a cement plant, the air handling capacity will be increased by 15% to 30%, which can achieve high-throughput continuous work, and the PTFE membrane has no adhesion to the cement dust, and the dust can quickly pass through the dust collector , Reducing the dust explosion rate of the factory.

Application of PTFE Gasket in Chemical Industry

PTFE gaskets are made of PTFE as the main material. Because of its high corrosion resistance, stable physical properties, and high and low temperature resistance, it has achieved good sealing performance and is widely used in petroleum and chemical industries. Applicable media include water, oil, acid solution, alkali solution and almost all chemical components.

Taking into account the high price of raw materials for chemical products, any leakage will bring great losses to users. Chemical products are more flammable and explosive, and leakage is likely to cause immeasurable and serious losses such as explosions, fires, and casualties. Therefore, the petroleum and petrochemical industry places such high requirements on sealing products.

The medium in the petroleum and petrochemical the industry is mostly a variety of liquids and gases with different corrosive properties, such as aromatic hydrocarbons, rust inhibitors, sour gas, drilling fluid, seawater, carbon dioxide, hydrogen sulfide, etc., and these media are often mixed together and have high temperatures The characteristics of high pressure require the use of sealing products such as PTFE gaskets to have excellent quality and good chemical properties.

Introductions of sintering furnace

What is a Sintering Furnace? 

A PTFE sintering furnace is used during the sintering process, which involves the heating of powder compacts in order to increase the product's mechanical strength, density, and translucency. This type of oven must be able to maintain heating temperatures below the product's melting point, as the goal is not to liquefy the material. Rather, a sintering furnace is used more to shape materials into their final product. 

How Sintering Furnaces are Used Sintering furnaces are used within the manufacturing industry when producing metals, ceramics, plastics, and other materials:
• Metal sintering is used to develop a wide variety of products including shotgun shells used by the military, aircraft hydraulic systems, and stainless steel tools.
• Ceramic sintering uses substances like glass, aluminum, zirconia, and silica to develop pottery and other ceramic products.
• Plastic sintering is used to develop products that require wicking properties, as well as materials used as ski and snowboard bases.

Introduction of PTFE welding process

Steel-lined PTFE equipment usually has a discharge port, a mirror, etc. in the production, but how to successfully apply this type of nozzle to the complicated head intersection line, of course, our answer is welding So how do you weld it? How to control the temperature of PTFE welding? Let us tell you one by one.

1. Production of Teflon head nozzle

      To weld the Teflon nozzle to the head, we should first make a PTFE head nozzle, according to the inner diameter of the steel head nozzle and use a powder molding process to make the nozzle at a certain ratio, at 380 plus or minus Sintering is carried out at 5 degrees Celsius for 8 hours. After the completion, the sintered nozzle is turned to the appropriate size with a lathe. At this point, congratulations on the production of the Teflon nozzle are complete.

2, the opening of the PTFE head

      Put the drawn head into the steel head, and use the principle of light transmission to accurately open it. Note that the Teflon head must be matched with the steel head when it is placed, otherwise the drum will be easy to appear when finalizing the equipment. Potential hazards such as rupture.

3. Welding of Teflon nozzle

      We can carry out the welding of PTFE through the first two steps. Here we know that there are two ways of welding (hot pressure welding, hot air welding).

(1) Hot pressure welding

      Before the hot pressure welding is carried out, we need to know the necessary theoretical knowledge. Thermal pressure welding is a kind of hot-melt welding that provides sufficient heat and sufficient pressure. Here we must ensure that the welding interface temperature must reach 673.15K, the pressure reaches 1-2MPa, so in order to ensure the welding progress, we need to do the corresponding mold to ensure the successful completion of the hot pressure welding. After all is completed, the FEP film can be welded by pressurizing and heating the interface between the nozzle and the head.

(2) hot air welding

      The same hot-air welding of PTFE is also a kind of hot-melt welding. It is much simpler than hot-pressure welding. It does not need so many molds. After the nozzle is placed, the PFA electrode and the hot air welding gun higher than 713K are used first. Preheating is then carried out on the weld for continuous welding.

Note: Whether the temperature of hot-pressure welding or hot-air welding is higher than the melting point of polytetrafluoroethylene, PTFE may be cracked at this temperature, and highly toxic gases such as perfluoroisobutylene may be generated during the cracking process. Therefore, the welding should be carried out in a ventilated environment. When the conditions are not allowed, such as lining the PTFE tank, the wind must be blown by the fan to ensure the air flow and at the same time wear a gas mask to ensure safety.