Study on related properties of ptfe

1.  Properties of polytetrafluoroethylene modified epdm rubber

 EPDM modified by polytetrafluoroethylene (PTFE) and nano silicon dioxide (SiO2) was prepared by vulcanization. Scanning electron microscope and infrared spectrum showed that PTFE and EPDM had good compatibility. DSC test showed that the composite had a unique glass transition temperature. When PTFE is added in 5 parts, PTFE and EPDM have a good compatibility. At this time, mechanical properties of epdm-ptfe reach the highest, and its tensile strength, elongation at break, hardness and tear strength are 22.42mpa, 588.91%, 82.0° and 49.60 kN/m respectively. Thermogravimetric analysis and aging experiments show that the aging and heat resistance of PTFE are improved. The mechanical properties of EPDM were also significantly improved after adding 5 parts of nano SiO2.

 2.  Structure and properties of polytetrafluoroethylene hot-rolled fiber membrane

 PTFE fiber membranes were prepared by hot rolling process and orthogonal design. Scanning electron microscope (SEM) was used to observe the surface morphology of the fiber membrane, and its thickness, permeability, aperture, porosity, tensile properties, acid and alkali corrosion resistance were tested and evaluated. The results showed that PTFE hot-rolled fiber film thickness was 0.12 ~ 0.15 mm, permeability was 80 ~ 101 mm/s, pore diameter was 14 ~ 17 ms, porosity was 14.57% ~ 27.04%, fracture strength was 38 ~ 59 N, elongation at break was 30% ~ 38%.In the 9 kinds of fiber membranes, there are still a lot of fibrous structures except the fiber melting on some surfaces. After acid and alkali treatment, the tensile properties of the fiber membrane remained unchanged. According to the orthogonal test results, the fiber mesh density has the greatest influence on the thickness, permeability, pore diameter and tensile properties of the fiber membrane, and with the increase of fiber mesh density, the permeability and pore diameter of the fiber membrane decrease, while the thickness and fracture strength increase.

 3.  Structure and properties of polytetrafluoroethylene/polypropylene hybrid melt jet filter material

 In order to extend the storage time of static charge on the surface of polypropylene (PP) melt-blown materials, the storage capacity of static charge was improved by organic hybridization. In the experiment, PTFE ultrafine powder and PP slice were mixed to granulate in a certain proportion, and different nonwoven materials were obtained by melt-jet molding process. The structure and performance of the nonwoven materials, such as apparent morphology, micropores, surface electrostatic potential and filtration efficiency, were studied, and external corona electret technology was adopted to make the material surface carry static charge. The test results show that adding PTFE can effectively improve the storage capacity of static charge of melt-jet PP nonwoven materials, and when PTFE mass fraction is 0.1%, the surface static voltage is the highest, the filtration performance is the best and the static charge stability is the best.

 

Introduction to steel lined teflon tube

Firstly, imported PTFE powder is used to push (squeeze) the teflon tube, and then it is forced into seamless steel tube (liner outer diameter is slightly larger than tube inner diameter 1.5-2mm) to form a tight liner without clearance.In order to eliminate the pressure, it is put in the furnace, heated to 180℃ for constant temperature treatment, so that it can be used in the temperature below 180℃.At the same time, the axial tensile strength of push tube is better than that of wound tube.The pipeline has ideal positive and negative pressure resistance.

PTFE powder moulding method is a kind of body, such as pressure, such as isothermal manufacturing technology, through the extruded tube (loose lining, lining) of PTFE, PTFE belt winding and winding plus steel wire, and steel net within process of evolution, the PTFE lining powder compression molding technology is by far the PTFE lining the latest fifth-generation products, can be at a higher pressure, high temperature, strong corrosion under the conditions of use, the temperature below 200 ℃ and vacuum is 0.096 MPa, quenching heat or alternating operation, won't make PTFE grassroots fall off, the drum, expansion deformation of flat, thereby the fluorine steel body.

Chemical properties of steel lined teflon tube:

Air aging resistance: radiation resistance and low permeability: long-term exposure to the atmosphere, the surface and performance remain unchanged.

Non-flammability: the oxygen limit index is below 90.

Acid and alkali resistance: insoluble in strong acids, strong bases and organic solvents.

Oxidation resistance: resistant to corrosion of strong oxidants.

Steel lined teflon tube working characteristics:

Performance: working temperature of medium: -100℃~-250℃

Working pressure of medium: positive pressure: 2.5mpa, with negative pressure of 70KPa at normal temperature

Corrosion resistance: steel ptfe composite pipe, in addition to molten metal lithium, potassium, sodium, chlorine trifluoride, high temperature trifluoride oxygen, high flow rate of liquid fluorine, it can resist almost all chemical media, including concentrated nitric acid and aqua aqua corrosion, it can work for a long time in the temperature of 230℃-250℃.Steel polyvinylidene fluoride or other vinylidene fluoride composite pipe, halogen, halogenated hydrocarbon, strong oxidant, boiling acid, alkali, a variety of organic solvents have good corrosion resistance, but not resistant to smoke sulfuric acid, concentrated hot sulfuric acid and nitric acid, 90℃ above ketone, ester, amine and high temperature sulfonating agent corrosion.

Application fields of steel lined teflon pipeline:

Steel lined tetrafluoroethylene pipe is suitable for strong corrosive gas and liquid under high temperature, other types of steel plastic composite pipe and metal pipe are not suitable for conveying medium, steel ptfe composite pipe is suitable for all.In addition, steel polyvinylidene fluoride composite pipe suitable for the transport of corrosive media at the working temperature of -40℃~+150℃.

 

 

PTFE (teflon) coating

PTFE high performance special coating is based on polytetrafluoroethylene resin fluorocoating, the English name is Teflon, because of the pronunciation, often called Teflon and so on (all for Teflon translation). PTFE (teflon) coating is a unique high performance coating, combining heat resistance, chemical inertia, excellent insulation stability and low friction, with comprehensive advantages that no other coating can compete with, its application flexibility makes it can be used in almost all shapes and sizes of products.

Teflon is divided into PTFE, FEP, PFA and ETFE basic types:

· Teflon PTFE: PTFE (Polyfluortetraethylene) non-stick coating can be used continuously at 260℃, with maximum operating temperature of 290-300℃, extremely low friction coefficient, good wear resistance and excellent chemical stability.

· Teflon FEP: FEP (Ethylene fluoride propylene copolymer) non-stick coating forms non-porous film in the melting flow during baking, with excellent chemical stability and excellent non-stick characteristics, and the maximum operating temperature is 200℃.

· Teflon PFA: PFA (Perfluoroalkylate) nonstick coating, like FEP, forms nonporous film by melting flow during baking.PFA has the advantage of higher continuous service temperature of 260℃ and stronger toughness, especially suitable for use in the field of anti-viscosity and chemical resistance at high temperature.

· Teflon ETFE: ETFE is a copolymer of ethylene and tetrafluoroethylene. The resin is the strongest fluoropolymer and can form a highly durable coating with excellent chemical resistance and can work continuously at 150℃.

After coating with teflon, it has the following characteristics:

1, Non-viscosity: almost all materials do not bond with PTFE film.Very thin film also shows good non - adhesion properties.

2, Heat resistance: PTFE coating film has excellent heat and low temperature resistance characteristics.It can withstand high temperature to 300℃ in a short time and can be used continuously between 240℃ and 260℃ in general. It has remarkable thermal stability. It can work at freezing temperature without embrittlement and without melting at high temperature.

3, Sliding: PTFE coating film has a lower friction coefficient.The friction coefficient changes when the load slides, but the value is only between 0.05 and 0.15.

4, Moisture resistance: PTFE coating surface does not stick to water and oil, and it is not easy to stick to solution during production operation. If there is a small amount of dirt, it can be removed simply by wiping.Short downtime, save time and improve work efficiency.

5, Wear resistance: under high load, with excellent wear resistance.Under a certain load, it has the double advantages of wear resistance and non-adhesion.

6. Corrosion resistance: teflon is almost impervious to drugs and can protect parts from any kind of chemical corrosion.

Ptfe is a polymer of tetrafluoroethylene.The abbreviation is PTFE. It's called teflon. It is known as the "king of plastics".The basic structure of ptfe is. - cf2-cf2-cf2-cf2-cf2-cf2-cf2-cf2 - ptfe is widely used in a variety of acid and alkali resistance and organic solvents, it is not toxic to humans, but perfluorooctanoic acid ammonium (PFOA), one of the raw materials used in the production process, is thought to have carcinogenic effects.

Study on ptfe tape as root canal isolation material in oral cavity

PTFE tape, which is commonly used as plumber’s tape is an inorganic, non-fibrous, ribbon like material. The aim of this study was to evaluate PTFE tape as endodontic spacer material and to compare it with commonly used spacer material that is cotton, in primary teeth.;Seventeen children undergoing pulpectomy of lower second primary molar bilaterally were included in the study. 

Cotton and PTFE tape were placed as spacers on each side randomly. Samples were taken from the access cavity at baseline and after seven days to check for microbial leakage. Spacer materials were also checked for microbial contamination.;The results revealed that there was a significant increase in the bacterial colony count after seven days in cotton group. The access cavities were also positive for microbial leakage in the cotton group where the spacers showed positive growth. In PTFE group only two samples showed microbial contamination of spacer and out of two only one sample showed contamination of access cavity along with spacer.;Within the limitations of this study, it can be concluded that PTFE tape performed better than cotton as endodontic spacer material. 

Thus, PTFE tape can be recommended as an endodontic spacer material as an alternative to cotton in primary teeth. 

 

Introduction of ptfe welding process

Steel lined ptfe equipment is usually made with discharge port, feed port, perspective mirror, etc., but how to successfully apply this kind of pipe port in the complex head intersecting line, of course, our answer is welding, then how to welding?How to control the temperature of ptfe welding?Below we tell one by one.

1, ptfe head pipe mouth production

PTFE pipe welding on sealing head to first of all, we should make PTFE sealing head nozzle, according to the size of the nozzle diameter steel head and according to certain proportion by using powder moulding process manufacturing nozzle, 8 hours of sintered under the 380 plus or minus 5 degrees Celsius, after the completion of the sintering good nozzle with lathe car to the right size, to the congratulations of PTFE tube at this moment you have finished.

2, ptfe head opening

Put the extracted head into the steel head, and use the principle of light transmission to accurately open the head, pay attention to the ptfe head must be consistent with the steel head, or the final equipment is prone to bulge, rupture and other potential hazards.

3, ptfe pipe mouth welding

By the first two steps, we can carry out PTFE welding. Here we know that there are two ways of welding (hot pressure welding and hot air welding). We will explain them one by one.

(1) hot pressure welding

Before hot pressure welding we should know the necessary theoretical knowledge, hot pressure welding is a kind of hot welding, provide sufficient heat and enough pressure.Here, we must ensure that the welding interface temperature must reach 673.15k and the pressure reaches 1-2mpa. Therefore, in order to ensure the welding, we need to make corresponding molds to ensure the successful completion of the thermal pressure welding.When all is done, the FEP film can be welded by pressurizing and heating the interface between the nozzle and the head.

(2) hot air welding

Similarly, ptfe hot air welding is a kind of hot welding, which is much simpler than hot pressure welding and does not require so many molds. After placing the pipe mouth, PFA welding rod and hot air welding gun higher than 713K are used to preheat PFA first and then place it on the welding seam for continuous welding.

Note: whether it's hot pressure welding or hot air welding welding temperature will be higher than the melting point of ptfe, ptfe is possible under the temperature cracking, produces in the process of pyrolysis perfluorinated isobutylene and other poisonous gases, so the welding should be in a ventilation environment, when the condition does not allow such as the four fluorine lining tank welding in production must use the fan air supply air flow assurance and wearing a gas mask to ensure security at the same time.