What Is Expansion Joint Sealant?

Sealant is a sealing material that deforms with the shape of the sealing surface, is not easy to flow, and has a certain adhesiveness. It is an adhesive that is used to fill the gaps in the configuration to provide a sealing effect. With anti-leak, waterproof, anti-vibration, sound insulation, heat insulation and so on.

Classification by vulcanization method

Wet-air vulcanizing sealant: This series of sealants use moisture in the air to vulcanize. It mainly includes one-component polyurethane, silicone rubber and polysulfide rubber. Its polymer base contains active genes. It can react with water in the air to form cross-linking bonds and vulcanize the sealant.

1. Clean the parts to be repaired to remove oil and dust; 2. Set the width of the joints and apply masking tape to ensure smooth and beautiful after construction; 3. Smoothly squeeze the glue gun at a 45-degree angle. Seal the gap with glue; 4. Smooth the surface of the modified colloid with a steel ball rod along the surface of the sizing place to remove excess gel; 5. Carefully tear off the textured paper. The gel should not be touched for 3 hours before the initial curing. ; 6, the colloid is completely cured the next day. ^[1]

The quality of the seal directly affects the packaging effect, the storage and life of the packaging, and even the credibility of the packaging. For this reason, sealing glue has become an important part of the packaging field. According to the form and use of sealing materials, they can be roughly divided into three types: gasket seals, tape seals, and gel seals, which can achieve the purposes of preventing liquid leakage, blocking oxygen, moisture, and odors from entering, preventing counterfeiting, and shoddy products. Anti-counterfeiting seals are generally sealed with hot-melt adhesive or pressure-sensitive tape. Once the packaging is removed, it cannot be restored to its original state, which can prevent the appearance of counterfeit products and protect the interests of consumers. ^[1]

Before choosing a sealant, consult with a senior adhesion sealing expert to determine the sealant that best meets your needs. Their expertise will help you find the best sealant-excellent quality while eliminating unnecessary expenses. Circled the optional sealant, you can reduce your sealant costs by following these steps. 1. Do not use too much sealant. Sometimes, the manufacturer thinks that the more sealant used, the better the effect of adhesion. In fact, this is a wrong idea. Using an excessive amount of adhesive not only increases the cost of the adhesive, but also affects the effectiveness of the connection. If you have any questions about the amount of sealant, consult the salesperson of the sealant product or the technical staff of the manufacturer, they will provide you with a practical solution. 2. Lower the fill point of the application device. If you frequently need to change adhesive residues, try lowering the fill point of your application. 3. Extend the shelf life of the sealant. If you cannot use a whole bucket of sealant at a time, reseal the sealant container as soon as possible to prevent the product from solidifying or evaporating. 4. Check the pressure of the device. If the pressure of the equipment is too high, it will lead to waste of sealant and affect the service life of the hydraulic pump. What you need to do here is to determine a reasonable pressure setting and ensure that the equipment operator strictly adheres to this setting. 5. Regularly inspect and maintain your production equipment. Regular equipment maintenance will effectively improve equipment performance. In addition, it can reduce equipment maintenance costs. 6. Compared with other sealing products, water-based sealants can greatly save costs. Therefore, when choosing a sealant product, try to give priority to water-based seal products. Water-based sealing products are easy to clean and simple to use. Unlike chemical sealants, long-term maintenance of equipment requires high investment. 7. Repeated use of purified water and washing water. The production equipment is equipped with a system capable of using the washing water multiple times to realize the multiple uses of the purified water and the washing water. ^[1]

1. Surface preparation The construction surface should be clean, hard, dry and free of oil, grease and surface dirt such as release agents, curing films and hydrophobic agents. Thoroughly remove all loose particles and dust. 2. Primer 3. Primer for concrete and porous surfaces. 3. Sika glue construction. 4. Joint design at ambient temperature. Allowable change in joint width: above 0 . The average width of the joint is ± 12.5% below 0 ° C, which is the total amount of ± 5% of the average width of the joint when sealing. 5. Generally, Sikaflex-11FC polyurethane sealant and adhesive are used to successfully seal the joint. The design rules are worth paying attention to: the seam width is more than 12mm, the width-to-depth ratio is 1: 1, the seam width is less than 12mm, and the width-to-depth ratio is 2: 1. At the same time, in order to prevent the seal from sticking to the bottom of the seam, the Sikaflex-11FC polyurethane sealant and adhesive must be filled with a tightly sealed, non-rotating, non-absorbent backing material. Sika offers open cell polyurethane or closed cell polyethylene backing strips. Do not use oil or tar impregnated backing materials. 6. The rules for the design of expansion joints 1. The corners of concrete joints are usually weak due to insufficient vibration, so they should be treated as bevels or recesses 2. The bottom of the joint must not limit the deformation of the sealant, otherwise Sewing can cause damage when put into use. 3. The depth of the seam seal should be adjusted by inserting a suitable seam backing material. 4. The corner seam must also be inserted into the backing tape or backing strip, otherwise, the sealing adhesive will be damaged when the seam swells. ^[1]

Soft elastic sealant

Liquid tank sealant for high efficiency air filters. After the liquid tank sealant is cured, it is an elastic colloid, which is specially used for sealing in high-efficiency air filters. An airtight seal can be formed in the aluminum tank. The liquid tank sealant adheres well to the tank wall. If the filter is moved or removed, this glue will be easily separated from the filter, restore elasticity, and automatically restore the sealing effect. It has excellent weather resistance, excellent chemical stability, corrosion resistance, can absorb the stress caused by thermal expansion and contraction without cracking, and has moderate soft hardness and good elastic recovery. ^[1]

Due to the increasing number of product brands of sealants, it should be selected based on comprehensive considerations of the conditions of use of the sealing parts, the material of the sealing sub-couples, the state of the sealing sub-joint surface, the type and performance of the sealed medium, and curing conditions . About the use conditions: including the state of stress, working temperature, environment, and whether the seal accessory needs to be removable. Regarding the material of the sealing accessory: Generally for non-metallic parts, a low-strength sealant can be selected. For metal parts, a high-strength sealant should be used. Regarding the state of the sealing sub-couples: it includes the gap size and morphology of the sealing sub-couples in the assembled state, surface roughness, and whether there is iron oxide scale. Generally, when the gap is large or the surface is rough, a sealant with a high viscosity should be used. When the sealing area is large or the sealing surface is smooth, a low-viscosity sealant should be used. Regarding the type of sealed medium: full attention should be paid to the compatibility between the sealed medium and the selected sealant, that is, to ensure the stability of the chemical and physical properties of the sealant itself in the working state, so that it is compatible with the sealant. The liquids are compatible with each other. Regarding curing conditions: If anaerobic adhesives are used, care should be taken to ensure that they are isolated from the air. If, at the work site, it is not possible to achieve heating and complicated process conditions that promote the curing of the glue, you should choose another type of sealant that can be at normal temperature and does not need to be isolated from the air. Alternatively, control and reduce the sealing clearance of the mating surfaces. At the same time, in the glue solution of the anaerobic adhesive, the catalyst component is increased to shorten the curing time. ^[1]

I. Pre-assembly inspection Pre-installation is required to check whether the seal has been deformed after pre-treatment to affect the assembly. The deformed sealing surface should be trimmed, and the sealing gap should be uniform. The gap is between 0.1-0.2mm and the maximum does not exceed 0.8mm to meet the requirements of sealing assembly. Second, trimming In order to remove the excess glue edge extruded after pressure curing, improve appearance quality. Do not peel the adhesive layer during trimming. 3. Immediately after gluing, pay attention to spreading evenly. Common methods include hand coating, spray coating, roll coating, pressure injection, pressure dipping and vacuum dipping. A single piece, a small amount of glue is applied by hand, using brushes, spatulas and rollers of various shapes. Spray guns can be used for large areas, but the glue is thin. High-resistance glue can be used to repair the gap by injecting. The casting of large quantities of castings uses pressure or vacuum dipping. Fourth, the purpose of pretreatment is to remove oil, paint, rust and dust on the sealing surface. Diesel and gasoline are commonly used cleaning fluids. Precision or small-area mechanical parts can be washed with solvents such as acetone, ethyl acetate, and banana water. The large sealing surfaces are usually sodium hydroxide, sodium carbonate, sodium metasilicate, and sodium metaphosphate. Wash with alkaline solution. It is more desirable to treat with trichloroethylene vapor. The patent leather can be burned with a flame torch and then washed with a rust remover or the above method. Fifth, the purpose of chemical treatment is to remove the oxide film, and the sealed surface after chemical treatment forms a dense and uniform new oxide film, which is conducive to the immersion of the glue, and the surface polarity is increased, which significantly improves the attachment power. After the sealing surface is chemically treated, it needs to be dried. The drying temperature and time should be strictly controlled. Do not leave it for a long time. After drying, it should be glued. 6. Check whether the coating is uniform, thickness is consistent, and curing is complete. Common inspection methods include ultrasound, acoustic emission, X-ray irradiation, infrared, and holography. 7. Glue mixing should be carried out according to the formula and operation sequence, and the mixing should be uniform. 8. The metal oxide skin layer on the surface can be removed by mechanical treatment. Among them, sandblasting effect. The grit material is reasonably selected according to the hardness of the material being processed. Iron can be used for hard metals; sand or alumina can be used for aluminum-based soft metals. Nine, curing Temperature and time play an important role in the curing process of the adhesive layer. At the same time, a certain pressing force is required. The heating temperature depends on the curing characteristics of the glue. Most room-temperature curing adhesives need to be left for 24 hours to achieve good performance. The curing time of heat-curing adhesives is generally 1-3 hours. The anaerobic adhesives need to be isolated from the air to be cured. Curable. ^[1]

There are many types of sealants: silicone sealants, polyurethane sealants, polysulfide sealants, acrylic sealants, anaerobic sealants, epoxy sealants, butyl sealants, neoprene sealants, PVC sealants, and Asphalt sealant.

Buy sealant mainly depends on several properties: 1. Breaking strength (pulling force / cross-sectional area); 2. Adhesive strength (pulling force / bonding area, except for substrate damage); 3. Elongation at break Rate (length / original length when broken); four, anti-aging ability; five, appearance (mattness, particles, bubbles); six, shape retention (no drawing, facade does not sag); seven, shelf life; eight Cure time. There is no difference between glass glue and performance, and the price is suitable. Secondly, there is stability and sufficient quantity, which is a test of manufacturers. If the capacity of the sealant is less than the standard capacity (note: it is the capacity. This situation of the sealant is very serious), such a sealant is eliminated first. Such a company has a problem in its business thinking and the product is not much better. (There are also many problems, which prove that its product production process is not tightly controlled). If the amount is large, it is necessary to consider the production stability of the sealant ^[1]