Fluoroplast: technical characteristics, GOST

Fluoroplast is a synthetic polymer material widely used in the chemical, electrical and food industries, mainly as coatings. Its advantages include first of all the possibility of using in a wide range of temperatures and a low coefficient of friction.

Definition and types

Fluoroplasts call several types of fluorine-containing plastics. Most often in industry and everyday life, polytetrafluoroethylene is used. Depending on the manufacturer, this material can be called differently. In specialized stores in Russia, including imported polytetrafluoroethylene. Material made in the US is called "Teflon", in England - "Floyon", in Germany "Gostaflon". In Russia, it is known as fluoroplast-4.

Other varieties of this material are not widely distributed, but are also quite popular. It:

• Polytrifluorochloroethylene (fluoroplast-3);
• Polyvinylidene fluoride (fluoroplast-2);
• Other copolymers of fluorine derivatives of ethylene.

Preparation method

Get all these varieties by chemical means. In fact, they are polymers to which fluorine atoms are added. Hence their name.

Fluoroplast-4 is synthesized as a white powder, and then pressed and sintered at high temperature. Other grades of this material are usually obtained by quenching.

At manufacturing of many innovative modern products the fluoroplastic is used. Technical specifications are really just wonderful. The merits of this material include:

• High chemical resistance. Fluoroplast-4 does not dissolve even when boiled in royal vodka.
• Inertness and low porosity.
• Very low coefficient of friction. This figure for a fluoroplastic remains virtually unchanged at any temperatures.
• Excellent dielectric properties. This material remains an insulator even at a temperature of 200 g.
• Stability. The chemical properties of PTFE-4 do not change at temperatures up to -300 g.
• Fire resistance is another advantage of such a material as fluoroplastic. Characteristics (heat-resistant polymer is characterized by the ability to self-extinguish) it is allowed to use it in places with increased fire hazard.
• Gas tightness.
• Biological compatibility. This type of plastic is often used to make prosthetic devices.

Disadvantages of PTFE

As you can see, the material is very high quality and almost universal - fluoroplastic. Characteristics it has is simply wonderful. However, of course, he also has some drawbacks. To such it is possible to carry:

• High cold flow. This property somewhat limits the use of fluoroplastic in electronics.
• The ability to release harmful substances when heated above +300 g.
• The weight in comparison with other polymers and not too good durability.

Where to use

Fluoroplastic is used in many areas of the national economy. Very often it is used:

• In the automotive industry. Since the friction coefficient of this material is very small, quality bearings, friction points, support racks, etc., are obtained from it.
• In the electrical industry and electronics. The fluoroplastic insulator is also simply excellent. Therefore, it is often used in the manufacture of cables, boards, radio components, etc.
• In medicine. In addition to prostheses and fluoroplastic implants, storage tanks for serum and plasma are made. Produce from it and packaging for medicines.
• In the food industry. Very good this material is suitable, for example, for the manufacture of rolls of dough, used in bakeries, pumps for pouring milk, etc. Teflon on the inner surface of the frying pan is also one of the types of fluoroplastic.
• When assembling water pipes and sewer systems (FUM tapes).

Thus, the material is very popular, and in some cases simply irreplaceable - fluoroplastic. Characteristics (its applicability is in fact very broad), stipulated by GOST, we will consider below.

Coefficient of friction

This figure is very small in PTFE. The kinetic and static friction coefficient for steel in it is only 0.04. However, as already mentioned, fluoroplastic - the material is not too wear-resistant. Therefore, after 100 passes the properties of its surface change. The static coefficient of friction increases to 0.13, and the kinetic coefficient to 0.08.

The fluoroplastic surface undergoes irreversible changes and at a very high sliding speed. In this case, the friction coefficient rises by 2-3 times. In this case, the value of this indicator can vary greatly from temperature fluctuations.

The coefficient of friction of fluoroplastic can decrease as the load increases. So, for example, under pressure:

• In 20-30 kg / m ^{2 the} value of this indicator is 0.1;
• In the 150-300 kg / m ² - 0.02.

The material is soft enough - fluoroplastic. Its characteristics are such that when used for manufacturing, for example, bearings, it is necessary to add powdered fillers to it. This can be coke, fiberglass, molybdenum disulphate, etc.

Optical properties

In thin films, fluoroplastic freely transmits light, that is, it is transparent. It looks about the same as polyethylene. In thick films, this material is translucent.

The transparency of fluoroplastic for UV rays, depending on the variety, is 2000-4000 A, for infrared - in the wavelength range from 2 to 7.5 μ.

Exposure to high temperatures

When the fluoroplastic is heated above 327 degrees, its crystals are destroyed, as a result of which it passes into an amorphous form. In the normal state, thick parts made of this material are opaque. After transition to an amorphous form, the fluoroplastic begins to freely transmit light. The material remains not viscous, but highly elastic. When heated to 415 degrees C and higher, the decomposition process begins. That is, a viscous-flowing PTFE does not happen at any temperatures.

This affects the technology of the process of manufacturing parts from it. Fluoroplast (technical specifications GOST determines with maximum accuracy) can not be used for processing by traditional methods for plastics. For example, it is impossible to make a product out of it by injection molding or by extrusion. Produce details and assemblies from this material using sintering technology, using "tablets" compressed at low temperatures.

Chemical properties

Fluoroplast-4 is a chemically stable substance. This material does not dissolve even in very aggressive substances - dilute and strong acids. Do not exert any influence on it and concentrated alkaline solutions.

The only thing with which it does not tolerate contact is solutions of alkali metals in ammonia, as well as elemental fluorine and trifluoride chlorine. The effect of these chemicals at elevated temperature.

Coefficient of expansion

For this parameter, the PTFE PT4 characteristics are also simply excellent. However, the coefficient of its expansion varies with temperature. How exactly, is shown in the table.

Recrystallization

As already mentioned, one of the drawbacks that the fluoroplastic possesses (the technical characteristics of which are generally quite good) is a sufficiently high degree of cold flow. In practice, this is reflected in a change in the shape of articles made from it at elevated pressure. If they are used at not too high temperatures - from +80 to +100 degrees C, the load on them should not be more than 10 kg / m ² . At greater pressure, noticeable deformations will remain on the product. With increasing temperature, the load must also decrease.

At a strong pressure (100-200 kg / m ² ), a sample made of PTFE can be crushed into a plate with a thickness reduction of 3-5 times depending on the temperature. When this material is deformed, it usually does not crack it and no other damage occurs.

In the table below you can see what technical characteristics (compressing under certain loads) in this regard.

It is possible to use a photoplastic for the manufacture of parts used and at a pressure greater than 30 kg / m ² . However, in this case, the design of the interfaces in the product should be as tight as possible. Do not allow the presence of cavities or significant gaps in it. In this case, the fluoroplastic will simply have nowhere to flow out. Material fluoroplastic - not too elastic. Therefore, in order to achieve a close fit, it is added to the rubber during production. Sometimes special joint springs are also used at the junction points.

Fluoroplastic: technical specifications

In the production of PTFE-4, the requirements of GOST 10007-80 are compulsorily observed. The most significant physico-chemical properties of this material are presented in the table below.

Here are such wonderful fluoroplast-4 characteristics. The properties of this material make it possible to use it for the manufacture of parts of the highest quality.

Stamps of fluoroplast-4

As already mentioned, polytetrafluoroethylene is the most popular variety of polymers of this type. At the moment, there are several grades of fluoroplast-4:

• F-4PN. Used for the manufacture of high reliability products.
• F-4O. Used in the manufacture of general-purpose products.
• F-4D. Thin-walled tubes, cable insulation, hoses and FUM tapes are made of this type of PTFE.
• F-4D. It is a highly technological material used for the manufacture of products of precise size.

Sheet Fluoroplastic

Products of this type are very in demand in modern industry. For the production of electrical insulating, antifriction and gasket products, a polymer such as fluoroplastic, technical characteristics is very good. The sheet version of its manufacturing technology is classified into:

• C grade material (planed);
• Brand "P" (pressed).

This fluoroplastic is sold in rolls without a coil. Its thickness is also determined by GOST and, depending on the width, can be 2-4 mm.

Fluoroplastic, whose technical characteristics are simply excellent, is a modern material used for the manufacture of a wide variety of components and components. In comparison with conventional plastic, it has a lot of undeniable advantages. Both the fluoroplastic itself and its products, in view of the increased requirements for quality, must be manufactured in strict accordance with GOST.