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Gaskets To Choose From

2024

Video: Gaskets To Choose From

Video: Gaskets To Choose From
Video: 50HP To 5000HP | Choosing Your Head Gasket | SCE Gaskets [TECH TALK] 2024, March
Gaskets To Choose From
Gaskets To Choose From
Anonim

TECHNICAL ASSISTANCE

Materials

CAR SEALS

GASKETS FOR SELECTION

VYACHESLAV LUKYANOV

It happens that I broke the gasket when disassembling the unit - and try to find a new one on the market! Especially for a rare car. Fortunately, the chemistry of polymers helps the master out in the most seemingly hopeless situations. On sale is full of all kinds of sealants, liquid gaskets - they can seal the most intricate joint.

Let's run to the STORE …

What is there only! Let's start with anaerobic sealants (based on dimethyl acrylate esters). The fact that they polymerize only in the absence of oxygen, in many cases, serves as an important advantage. You can safely apply sealant to one of the joined surfaces and slowly, very accurately set the second on it. When the gaps are less than 0.5 mm, the sealant will begin to polymerize. In other words, it behaves "as it should" - is convenient to use. True, not without reservations. In order for the reaction to go well on glass or non-ferrous metals, it is desirable to treat the surface on which the sealant is applied with an activator.

The compound based on anaerobic sealants is very strong, chemically resistant.

The next group of materials is polymer-based sealants-adhesives (photo 1). Their main purpose is additional sealing of rigid gaskets, as well as gluing of glasses. (We are not considering this application today.)

The largest group of materials is silicone sealants (based on silicone rubbers). They polymerize due to the moisture contained in the air. At an air humidity of not less than 50% and a temperature of 20 ° С, the polymerization rate reaches 2–4 mm per day. It is not recommended to apply these compounds in frost - a normal reaction does not work. By the way, in order for the reaction to go well, the applied composition must be kept in the air for 10–20 minutes and only then connect the parts.

There are also compositions that polymerize under ultraviolet radiation. These are primarily needed in industry where hardening speed is important.

Important advantages of silicone sealants - high adhesion to almost any material, after polymerization - excellent strength and chemical resistance, ease of use and undemanding to the geometry of the joint. Some formulations easily seal gaps up to 6 mm. The resulting gaskets are extremely flexible, withstand even 10-fold elongation.

Some companies produce special compounds based on elastomers - for the formation of removable (reusable) seals. An example is Permatex's Right Stuff. This material is squeezed out of the tube into a special mold, where it polymerizes in a few minutes. The resulting seals in performance often surpass the traditional, carved from a sheet.

Such seals (photo 2) are indispensable where the use of liquid sealants is unacceptable - because of the risk of clogging of channels, drilling, etc. For example, in automatic transmissions.

Most auto sealant manufacturers operate in the United States. These are Abro, Done Deal, Lion, Loktite, Permatex, Sega, Valco, Verdachem, Qulco and others.

AND SKILLED SOMETIMES MISTAKES …

And inept - as a rule. Here are typical mistakes: to the unpurified (from dirt, oil, working fluids) surface the sealant does not stick, and subsequently can squeeze out of the joint; sealant characteristics do not correspond to working conditions (temperature, etc.); the sealant layer is too thick: it is squeezed out and may interfere with the operation of the unit, clogging oil channels, other drills, nozzles, etc.; the same - due to excessive contraction of the joint; sealant is applied to both abutting surfaces, which will complicate subsequent disassembly.

The "universal tool" of many craftsmen is a finger! Small surfaces can be easily coated with an even layer of sealant. But if you need to tighten the big joint, we put up a finger for something else and, having unscrewed the cap from the tube, we will probably dispense. Cut off its tip so that we get a hole of the right size. Now you can squeeze the sealant onto the joint surface with an even strip.

By the way, it is not necessary to scrap off the traces of the previous sealant, there are special tools for this - for example, Gasket Remover.

READ THE TEXT!

Choosing a sealant, carefully read the instructions! Many formulations are applicable with certain limitations. Some, for example, can not withstand prolonged contact with gasoline, water. Others are for very specific tasks. So, Permatex-Water Pump & Thermostat is used mainly in cooling systems.

From the point of view of a chemist, silicone sealants are divided into two groups - acidic and neutral. The former emit acetic acid during polymerization (it gives off a characteristic odor), the latter - alcohol or ketoxime (almost no smell).

Acetic acid is aggressive towards non-ferrous metals. On modern foreign cars, this is taken into account - and only neutral sealants are used. These are Gray compounds, copper-based Cooper, Permatex Ultra (Low Odor) sealants. We regard the Russian Hermesil, Polisil, Avto, and BBF as neutral, but by their characteristics they are not suitable for highly loaded joints.

For engines with converters in the exhaust system, only those sealants that do not emit substances that pollute oxygen sensors, for example, with the designations Safe for sensor, Sensor safe (photo 3), are suitable.

An important indicator is the maximum permissible operating temperature. According to this criterion, sealants can be divided into approximately the following five groups: up to 200 ° C - mainly domestic; up to 260-315 ° С - Blue, Black (blue, black - depending on the manufacturer); up to 345 ° С - Gray, Red (gray, red); up to 380 ° С - Cooper (with copper) (photo 4).

RANGE

In retail, imported sealants are usually packaged in 85 ml metal tubes. The kit includes a dispenser tip.

Professional repairmen can also purchase sealants in larger plastic tubes. A syringe gun is convenient for working with them (photo 5). Aerosol formulations are also available.

With the prices of sealants, everything is logical: the better - the more expensive. Acid sealants cost 60–90 rubles. for a tube of 85 ml, about the same as all domestic. Neutral - from 100 to 140 rubles. One of the most expensive is a high-quality gray sealant at 175 rubles.

As we have noted more than once, not all trading companies accompany the product with instructions in Russian. There are obvious mistakes in the texts. For example, in the English text on the ABRO RED package, the maximum temperature of use is 260 ° C, and in Russian - 343 ° C. The translation claims that the sealant is safe for the oxygen sensor, and not a word about it in the original source (photo 6).

Finish on a sad note: there are a lot of fakes on sale both domestic sealants (for example, Hermesila), and imported. Be careful.

1. Anaerobic Gasket Maket Anaerobic Sealant and Super High Tack Adhesive Sealant.

2. Seals made of Permatex Black and Gray Right Stuff sealants.

3. Sealants for systems with a neutralizer (Safe for sensor or Sensor safe).

4. These preparations are designed for various operating temperatures.

5. Dispenser options.

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