In general, the fixation method threaded connections using various compositions (paint, glue...) is not new for a long time and is widely used in industry, but mainly in unloaded units.
The emergence of specialized products was a real revolution in this area and made it possible to ensure reliable fixation under both normal and increased loads. At the same time, there was no need for large quantities various locking parts, the assembly process has been greatly simplified.
Mechanical fixation of screws using locknuts, spring washers, toothed rings, cotter pins means that the user must have a very large stock of fixing elements for all occasions, which, as is known, do not provide a seal to the thread and do not prevent the appearance of rust, but reuse in most cases it is impossible.
To anyone who knows these problems, it is clear why specialists are increasingly using more modern and reliable method– fixing the thread with glue.
Permabond adhesives not only provide more high reliability threaded connection, in most cases they also provide great savings.
To fix threads, they are used high temperature adhesives, which act as sealants for threaded connections. Such adhesives are new phosphate compositions, which are characterized by high adhesive ability to fireproof materials, increased heat resistance and gas tightness.
High Temperature Adhesive is a high strength anaerobic adhesive that is extremely resistant to high temperatures.
The material hardens in an airless environment between tightly fitted metal parts. Used to secure and seal bolts, nuts and screws where long-term assembly is required.
For example – for use in fire protection systems pipe sealants and Permabond A126 are used. They provide a sealing and hardening gasket that will withstand the critical burst pressure ratings of most pipes.
Fixing and sealing screws
- Fixing screws with Permabond glue replaces a whole warehouse of mechanical fixing elements and frees you from dependence on thread sizes. In addition, the connection using Permabond glue is performed with a conventional tool; without the risk of self-unscrewing
- When the Permabond adhesive cures, it creates a seal that protects the threaded joint from corrosion, which would inevitably cause it to fail.
To fix the threaded connection, anaerobic adhesives are used, which cure only when air is displaced from the gap and in contact with the metal. Otherwise, these adhesives remain liquid.
Application of Permabond glue
When fixing a threaded connection with Permabond products, a drop liquid glue Apply directly from the plastic tube to the threads of a nut or screw. When a screw or nut is tightened, the liquid adhesive fills all the cavities in the threaded joint and cures to form a hard plastic.
The resulting threaded connection can withstand shock and vibration, is leak-tight and corrosion-resistant, and is permanently stable until dismantling, which again is carried out with ordinary hand tools.
Connection characteristics:
- Transforms simple nuts into self-locking
- Ensures complete tightness of the threaded connection
- Most threaded parts can be reused
- Reproducible torque/preload ratio
- Controlled strength of cured adhesive
- Oily screws and nuts (as supplied) may be used for assembly.
Advantages of Permabond glue:
- Simplifies and speeds up installation
- Stops leakage and corrosion
- Savings by reducing the number of fixing elements in stock
- Controlled clamping force on screws, nuts or spacer bolts
- Easy to disassemble - just a simple tool required
Here are some of the list of Permabond adhesives for fixing threads:
Anaerobic Adhesive is an anaerobic adhesive designed to secure and seal threaded or coaxially mounted metal parts where disassembly may later be required. Its controlled strength provides fatigue resistance, vibration resistance and corrosion resistance to large or fragile parts, while still allowing assembly and disassembly using conventional tools.
Ideal for use on parts that need to be removed for maintenance. High stability to vibration makes it possible to use it instead of a wide range of mechanical locking devices. Its excellent chemical inertness makes it suitable means for sealing small parts of pneumatic and hydraulic systems and can significantly reduce the effect of corrosion.
It is a high-strength, medium-viscosity anaerobic adhesive and sealant for threaded connections. This material hardens in an airless environment between tightly fitted metal parts. Cures quickly and reliably on steel, cadmium, zinc and other flat connectors. Used to secure and seal bolts, nuts and screws where long-term assembly is required. Once cured, the material prevents loosening and leakage.
It is an effective replacement for Permabond A130 fixative. In a matter of seconds, it is able to create a strong connection of materials that can later be easily dismantled.
The EFELE 113 retainer retains its properties under mechanical and thermal influences, provides reliable sealing of joints, protects against corrosion and completely replaces various sealing materials and locking mechanical elements.
Thanks to its resistance to various petroleum products, acids, gases and alkalis, EFELE 113 can be used in almost any operating conditions. Resistance to various petroleum products, alkalis, acids and gases allows EFELE 113 to be used in different conditions operation.
Heating and gas supplies must be completely sealed. This can be achieved only due to the quality of the thread itself, without the use additional materials, almost impossible. There are several methods of compaction, but Lately Anaerobic sealant for threaded joints has gained enormous popularity among craftsmen. Why?
Naturally, the main task of such seals is to completely seal the joints. The material used must completely prevent the leakage of water or gas through the threaded gap. But a high-quality seal must have other important properties:
- It should not contribute to corrosion of the elements being connected. On the contrary, the material applied to seal threaded connections is designed to protect these vulnerable areas from damage caused by exposure to water or aggressive substances.
- All sealing materials, including sealants, must have good adhesive properties to prevent them from being squeezed out of joints under pressure of water or gas.
- It must be resistant to temperature changes and withstand vibration vibrations.
- The materials used to seal the pipes should not significantly impede the assembly or disassembly of the connection. It is very convenient if after dismantling the sealant can be easily removed and reapplied.
Another one important feature What you should pay attention to when choosing a sealant or sealant for threads is ease of use. Very often such connections are in hard to reach places where any manipulation is difficult. In such cases, sealants have a clear advantage, since they do not require such careful and thorough application as sealing tapes or linen.
Sealing with linen thread
This method is the oldest. This is exactly how pipe connections were sealed in Soviet apartments. If the store does not have other sealants, then flax and plumbing paste are sure to be found. But this seal has a number of significant disadvantages:
- According to the rules, flax is used in combination with drying oil and red lead. Lead prevents corrosion of the joint, and drying oil fills the pores of flax like a polymer. But finding high-quality ingredients is quite difficult, so red lead is often replaced with iron, which only accelerates the oxidation of metal components. Some craftsmen get out of the situation by using silicone-based automotive sealants.
- The difficulty of laying linen thread on the thread. What is so easy for experienced plumbers can cause a lot of difficulties for a non-specialist. It is unlikely that you will be able to wind the flax correctly onto the joint the first time, and any error in performing this operation will lead to the seal not lasting very long.
- Len does not tolerate changes in working conditions very well. Therefore, in heating systems, its strands will collapse much faster. Also, this type of sealant does not react well to aggressive environments.
- The high hygroscopicity of the material leads to its swelling, which is why connections that are not strong enough can simply burst. For example, it is not recommended to use flax when sealing aluminum radiators.
Sealing with FUM tape or plumbing thread
Due to their ease of use, these materials have gained high popularity. To seal most threaded connections in an apartment, it is enough to wrap the number of turns of tape indicated in the instructions around the pipe and tighten it with a wrench. In this case, special care is not required when laying; on the contrary, many manufacturers recommend winding it slightly obliquely. The connection with such a seal can be easily disassembled if necessary.
At the same time, fum tape does not tolerate vibrations, does not cling well to small threads, and can be damaged by rough cutting. It is not recommended to seal pipes of significant diameter with it.
Use of sealants
Most optimal method on this moment is the use of various sealants. They provide not only complete isolation of the system from leaks, but also protect metal parts from corrosion.
Sealants are very convenient for installation and allow, if necessary, to disassemble a threaded connection without significant effort or damage.
The following types of sealants are distinguished.
Non-curing sealants
They are produced in the form of thick and viscous pastes consisting of polymers and synthetic resins. This consistency allows them to provide high-quality sealing of connections and calmly withstand vibration loads. Such sealants are often used in combination with other sealants.
Important! Non-hardening sealants cannot be used in high-pressure systems - the composition will simply squeeze out of the thread. They also do not tolerate exposure to aggressive materials well.
Hardening compounds
Manufactured using solvents. Such substances are also known as adhesive-sealants, as they provide not only tightness, but also reliable fixation of the joint.
How long does this material take to dry? Typically, the manufacturer indicates the hardening time on the packaging; it can range from several minutes to several hours. It should be remembered that when low temperatures the crystallization time increases significantly.
Their main disadvantage is the presence of shrinkage during hardening, which leads to the need for additional tightening of fittings. Another unpleasant feature is the impossibility of dismantling the connection without destroying the sealing layer. After disassembly, it will have to be removed and reapplied.
Anaerobic sealants
The most convenient and reliable sealants at the moment. Their liquid structure allows them to easily penetrate the narrowest gaps. In air, such a composition does not change its properties, but when it gets into a threaded connection, upon contact with metal and in the absence of air, it sharply changes its properties and crystallizes. The result is a durable plastic that reliably seals the threaded gap. In this case, the excess glue squeezed out after assembling the joint can be used to process the next pipe, and the sealant that gets inside can be easily washed off with water.
Using anaerobic sealants is very simple:
- All surfaces of the threaded connection must be cleaned and degreased. It is enough to wipe new parts with a solvent, old ones - treat them with a special metal brush.
- The solution is applied to several turns of the thread; for convenience, you can use a regular brush.
- The connection is tightened manually, without the use of keys.
- Excess sealant that protrudes from the outside is removed with a napkin. You can use it to seal another connection.
- It will take a couple of hours for the material to harden, after which you can safely use the threaded connection. The manufacturer's recommendations will help you determine the crystallization time more accurately. Do not forget that it increases significantly at low temperatures.
The term “anaerobic” came to technology from biology. This is the name given to microbes that prefer to exist and develop in the absence of oxygen. By the way, this is why all the tubes with anaerobic compounds we purchased are sold half-empty: they need air for storage! And when it enters a limited volume without air flow (for example, into a threaded gap), the composition quickly polymerizes, that is, hardens. Such means are used not only for locking threaded connections, but also for sealing welds, flange seals, .
Why did you need a replacement for growers and other ancient remedies? The class of thread accuracy has increased, optimal tightening torques are used in production, and bolts with an increased bearing surface are used. Therefore, the old-fashioned methods have practically died out: on modern car The grower is almost impossible to find anymore. But fixing compounds are used more and more often - when attaching brake calipers, camshaft pulleys, in gearboxes, and steering mechanisms.
To test anaerobic clamps, we prepared fastening elements with M10×1.25 threads - bolts and nuts. For each test product, we took it together with a nut screwed onto it, having previously cleaned and degreased them, treated the threaded part of the bolt with a fixative, after which a second nut was screwed onto it with a small fixed tightening torque (0.1 N m). A small tightening torque value is chosen so that it does not affect the final measurement, the purpose of which is to determine the loosening torque on an untightened threaded connection. In other words, we tested exclusively the effect of the clamps, and not our own muscles. Each of the threaded connections was numbered according to the conventional number of the fastener with which it was processed.
Manufacturers declare the abilities of drugs in different ways, but color gradation is mainly used. Red color suggests that we have before us a product with the highest possible capabilities - heat-resistant and even “one-piece”. Blue color indicates more modest fixing capabilities - the connection will remain detachable. There are also very weak drugs - green.
We do not recommend focusing only on color: look for exact information about the purpose of the product either on the packaging or in the description. However, not everything is transparent here either. For example, from what moment the connection is declared “inseparable” is not clear from the descriptions. Some manufacturers indicate the moment of resistance that their product provides, but do not talk about the corresponding size of the threaded connection. And this is important, because a tiny screw from glasses requires much less torque to unscrew than a huge hub nut. There is an opinion among people that “you can assemble it with a strong latch and that’s it.” But that's not true. Strong clamps can really kill small fasteners, but no sealant will turn even medium-sized connections into a monolith, for example, those with M10...M14 threads.
That is why we decided to test all purchased drugs using a single method. After 24 hours at room temperature, each connection was clamped in turn on a stationary frame so that the head of the verified torque wrench captured only the upper nut, which had to be unscrewed. The initial torque set on the key is 5 Nm, which is less than 10% of the maximum tightening torque of such fasteners (on M10 connections in cars the torque reaches 80 Nm). If the connection could withstand the specified force, the moment was successively increased in increments of 5 Nm. The higher the moment at which the threaded connection began to unwind, the higher the quality of the fastener being tested.
The final assessment was adjusted taking into account the manufacturer’s promises: those products whose descriptions did not promise anything received a lenient assessment, while powerful “red” ones, which frankly did not live up to the stated indicators, were subjected to harsher criticism. At the same time, the viscosity of the drugs was assessed. They differ noticeably in this parameter, but we did not find a direct relationship between viscosity and professional suitability of the product.
By the way, the clamps protect against oxidation and seal the connection. And sometimes the best fixative is rust. Along with anaerobic fixatives, we decided to test other methods of stopping joints - just for comparison. About them - a little lower.
| approximate price
70 rub. The sealant, liquid as water, gave in at the first test. However, his instructions did not promise anything specific. | approximate price 190 rub. The removable American fastener removed itself at the very first step of testing - with a minimum applied force of 5 Nm. | approximate price 190 rub. The rather thin composition successfully withstood the applied torque of 5 Nm, but gave up at the next threshold - 10 Nm. The result is weak, but the vast majority of drugs failed even this. |
| approximate price 150 rub. The rather thick product promised to last until 35 Nm. It's hard to say what the manufacturers had in mind, but it didn't take more than 5 Nm to unscrew our bolts and nuts. Fail. | approximate price 150 rub. The thick sealant promised to last up to 35 Nm, but in practice it gave up at 10 Nm. Better than many, but essentially it doesn’t matter. | approximate price 150 rub. The product promised to last until 17 Nm, regardless of the thread diameter. And the recommended range of application for thread diameter is not indicated. The result is negative: the connection easily untwisted already at a modest 5 Nm. Fail. |
| approximate price 290 rub. The product of medium consistency withstood a torque of 5 Nm, but gave up at the second step. Well, most couldn't do that either. | approximate price 390 rub. The rather fluid product did not show itself in any way, allowing the nut to unscrew on the first try. But there were no specific promises. | approximate price 310 rub. An expensive American product of modest volume showed nothing but ambition. The medium fluidity fastener gave in at the first contact with the torque wrench. What about the definition of “high-strength”? Failure! |
| approximate price 105 rub. The Russian product is a substance of medium viscosity. The tests ended very quickly: an applied torque of 5 Nm instantly moved the nut out of place. However, the manufacturer did not make any specific promises. | approximate price 105 rub. In practice, the rather thick composition behaved just as poorly as its colleague number 10: on the first try, the nut easily came loose. And this is called “one-piece”? Fail. | approximate price 190 rub. Not the thickest product, prone to dripping, won the competition by a large margin over its competitors! It was possible to move the nut fixed by him only by applying a torque of 30 Nm. Great! |
| approximate price 190 rub. The thin crew refused to fulfill their duties, giving up at the very first stage of inspection. We will assume that this means “medium strength”. | approximate price 160 rub. How to understand the contradictory wording “up to 20 mm or more”? For any thread? It sounds optimistic, and the torque is promised to be at least 35 Nm. But there was no result - the product of heterogeneous consistency gave up on the first step, at the mere sight of the key. Fail. | approximate price 160 rub. The product promised to fix fasteners up to a torque of 35 Nm, but things didn’t work out from the very beginning. The bottle with the screw cap leaked immediately - sealed products are better! The liquid of medium consistency, after the required exposure, gave up at the first touch of the key. Fail. |
| approximate price 160 rub. The thin product declared its readiness to last up to 17 Nm. It didn’t work: the connection came loose at a torque of less than 10 Nm. Our rating: satisfactory. | approximate price 300 rub. This product is not designed for a thread diameter of 10 mm, but we wanted to try it - what if? However, no “suddenly” happened: the nut came loose on the first try. But we won’t find fault: the product is stated to be weak. | approximate price 285 rub. The thick product loosened its grip only at a torque of 25 Nm. This is the second result in our sample. Very good! |
Who recorded who?
Well what can I say? General impression pretty pathetic. Of the twenty-one drugs tested, only six were able to withstand a modest initial torque of 5 Nm, and only two of the remaining ones advanced beyond 10 Nm.
However, the Teflon nut and lock washer also failed at the first stage. And nail polish turned out to be unsuitable for serious matters. The extra-grade glue left over from previous examinations lasted a little longer - it gave in under a load of 10 Nm. And the most curious thing is that at a torque of 30 Nm... the cotter pin was cut off! It would seem that the metal part would last longer, but it only repeated the results of the best drug we tested.
The winner was the American drug IMG MG‑414 High Strength. By the way, it is far from the most expensive. The second result is also from the “American” - this is Permatex 24026. There is no point in awarding third place with such test results.
The results obtained relate to a specific sample of thread lockers and cannot serve as a characteristic of the company’s products as a whole.
And further. Remember: than larger area treated surface, the stronger the clamp will “grab” into it.
But don’t be afraid to use clamps: our experiment showed that, if necessary, you are guaranteed to unscrew any connection processed by them in the car.
What fixes the connections?
Grover. This is a spring split washer used as a locking element. Grovers cannot be used on deformable materials such as aluminum and its alloys, as well as copper or bronze.
Polymer insert. A bushing is inserted into a special groove, which is deformed when the nut is screwed onto the thread. Once tightened, the polymer insert increases friction, preventing the connection from loosening due to shaking. The disadvantage of such fasteners is limited quantity assembly/disassembly operations.
Fold washer. Such washers are usually made of mild steel and equipped with claws. One of the legs is bent to the edge of the nut, which must be secured against unscrewing, and the other is fixed, if possible, on the part being tightened. It is clear that such parts are disposable.
Glue or cosmetic varnish. Nail polish or glue are often used for locking threads. The main advantage of such techniques is simplicity and confidence that things will not get worse. But these do not work for their intended purpose, so you should not expect serious protection from them.
Cotter pin. A metal rod is inserted into the through hole and its ends are bent. As long as the cotter pin is in place, the nut will not come off. It is clear that cotter pins can only be used with special nuts and bolts that have a hole. In addition, they will not help fix the bolt or stud in the body of the part.
Nut with safety collar. Those who dealt with the front hubs of Zhiguli cars probably remember a large nut, the thin collar of which had to be bent into the grooves of the axle in two places. The disadvantage of this solution is the need for a special part such as a bolt and a rather rare nut.
Lock-nut. The most primitive solution in the fight against self-loosening is locknuts. The additional nut is pressed against the main one and locks it. This solution cannot be used everywhere - sufficient space is required on the threaded part of the stud or bolt.
And for other similar purposes, thread sealant is used. Its main task is to make these connections as strong as possible, preventing leaks.
There are several types of such material; when purchasing, it is recommended to familiarize yourself with technical characteristics product to understand which one is best for you.
Characteristics
Carrying out large-scale repairs involves checking the quality of work at all levels. It often happens that the owners of houses and apartments do not take into account how tightly the pipes of all vital systems are connected. Such negligence can lead to a lot of unpleasant surprises in the future. If a water leak, even a minimal one, can be resolved in time when detected, then a gas leak is life-threatening.
Running pipes near an expensive household appliances will entail additional expenses if it fails due to water leakage. TO old-fashioned ways solutions to the leakage problem include thread, tow, plasticine, but in the era high technology To put it mildly, it is strange to use such ineffective materials. Thread sealant copes well with such tasks.
Types of thread sealants
Fum tape
With fum tape, everything is clear from the name. It is sold in reels in the form of a thin tape, which is tightly wound around the threads of pipes. Teflon thread is used to tightly connect pipes made of various materials for ventilation, heat exchange, water disposal systems, refrigeration units And so on. Often used in medical institutions, the food industry, etc., where there are high requirements for sanitary standards.
Anaerobic thread sealant
It has gained particular popularity recently, and all thanks to the best level each other, completely sealing the thread. At correct application, this material can withstand pressure of about fifty atmospheres, as well as decent vibration loads. Anaerobic sealant is rightfully considered good decision for use at home, as well as for professional use.
Details on Anaerobic Sealants
Differences
A distinctive feature of the anaerobic sealant gel for threaded connections is that the process of hardening occurs when the connecting work is completed and the access of air to the material has stopped.
Note.
For domestic use, a medium-fix sealant is sufficient; no more is needed. Since sealants with strong fixation hold the pipes tightly together, it is not possible to separate them in the future.
Sealants with a high level of connection are mainly used in industrial enterprises: plants, factories, and in the installation of urban drainage networks. Their price is very high, sealants require certain skills in handling them, due to the fact that the work must be carried out quickly without hesitation, movements must be honed. To dismantle connections of this type, you need to cut.
For threaded anaerobic pipes, it is also divided into types depending on the level of viscosity of the material. Frequent and small threads require the use of a sealant that can fill the joint space as much as possible. The maximum permissible pipe diameter is 40 mm.
Classification of colors of sealed thread adhesive
Classifying anaerobic sealant by color helps to immediately determine for what purpose it is used.
Thread sealant blue
The blue color of the material indicates that it is suitable for metal pipes. The connection occurs in such a way that its resistance to various influences from outside remains on high level. This sealant began to be used in everyday life relatively recently. Previously, it was used in industries (defense industry, aviation, space industry). The diameter of the pipes should not exceed 20 mm, and the connection can be dismantled without special tools.
Red thread sealant
Red sealants are used to seal old worn threads, as well as connecting ferrous metal pipes. Their setting time is shorter than that of other sealants, but the quality of the connection does not suffer. The material is resistant to temperature fluctuations and high blood pressure. Used to work with pipes with a diameter of no more than 30 mm. Heating tools are used to dismantle joints. IN repair work, excess sealant can not be removed, but applied over the existing layer.
Green thread sealant
Green sealant has a low level of bond strength, so it is often used for temporary fastening of metal and plastic pipes. No dismantling required special effort, this can be done by twisting. Also, it is worth noting that green sealant does not have excellent vibration resistance and high blood pressure like blue. The maximum permissible diameter of pipes for connection is 3.81 cm, and the thread must be intact.
Application areas of thread sealant
Anaerobic sealant for threaded connections was invented back in the 50s of the last century in the USA. At first, their scope of application was limited only to industrial enterprises. Then, gradually they began to be used in the construction industry.
At first, sealants were not used to connect water pipes, since there was an erroneous, unsubstantiated opinion that the composition of the material could have a detrimental effect on the quality of water. Later, research proved that all this was empty fiction.
Areas of use of thread sealant adhesive
Water pipes.
Sealant for threaded connections of water pipes is used when working with pipes in apartments and private houses. It can withstand water pressure, vibration and temperature changes. The color of the sealant is blue.
Plumbing.
Plumbing thread sealant is used for pipes in which it is necessary to create reliable connection. Water is supplied to the plumbing using pipes, the connection of which must also be made airtight.
Heating.
Sealant for threaded connections must be resistant to high temperatures and their fluctuations, antifreeze and chemical components in the heating system. For cast iron radiators, red sealant is used.
Gas pipeline.
Anaerobic thread sealant gas connections is best suited for this purpose. It has excellent qualities of reliably connecting everything related to gas. The color of the sealant is blue.
Advantages of thread sealants
- Heat resistance. Range permissible temperatures– 200°С + 300°С.
- Connection reliability.
- Economical consumption.
- Resistance to chemical compounds.
- Does not dissolve when exposed to water.
- Versatility.
- Resistant to high water pressure.
Cons of thread sealants
- Interdependence with temperatures. Pour point +15 – 25°C. At low temperatures, the sealant hardens longer and worse.
- The need to clean the surface. Cleaning, degreasing, drying - these are the three main rules for reliable adhesion of surfaces.
- Difficult to dismantle. Only with green sealant there are no problems; for the rest it is necessary to use tools.
How to use gel sealant for threaded connections?
Before applying the sealant, the surface to be treated must be diligently cleaned of rust and other contaminants. It is not necessary to remove the old sealant. New pipe Clean with a wire brush to enhance adhesion.
In order to degrease the surface, use any composition, for example, white spirit. Degreasing work must be carried out scrupulously, otherwise setting will not occur. A special activator is applied to plastic pipes at the joints.
Before opening, the tube of sealant must be shaken and only then opened. The composition must be applied in a thick layer along the entire perimeter of the thread. For better density The sealant is applied on both sides of the connection. This way you will achieve the best result.
After the adhesive and thread sealant have been applied, you need to thoroughly tighten the parts. Additional tools are not required, everything can be done manually. Any sealant that protrudes beyond the edges can be wiped off with a napkin.
You can check the joint for leaks after 15 - 25 minutes by creating a low pressure of gas or water, 10-15 atmospheres is enough. letting in water or gas. If there are no problems, wait until it hardens completely.
Note.
Complete setting of the anaerobic sealant occurs after 24 hours. Repeated strength testing is carried out at a pressure of 40 atmospheres. If there is a leak, everything needs to be disconnected and reprocessed.
Review of anaerobic sealant manufacturers
The most positive reviews We collected the following brands from users:
If the pipe is flimsy and brittle, do not try to unscrew it; use heat with a hairdryer. Temperature not less than 170°C. If possible, do not use sealants with a low level of adhesion, because disassembling pipes takes a lot of effort and time. For temporary fastening, use flax and thread sealant or fum tape.