Cold vulcanizing is a kind of conveyor belt repair and joint method with high curing and bonding strength to bond the conveyor belt through cold vulcanization adhesive, which can achieve rapid curing without heating and pressure, so that the conveyor belt forms a whole. This method is suitable for medium-sized conveyor equipment, and has the characteristics of wide application, convenient operation and high joint strength.
Principle for cold vulcanizing
1.The adhesive is two-component, composed of glue and the curing agent, and the two are used in a mixed ratio which is called weight ratio（wt）=9:1～10:1。
2.The glue is a solvent-based polymer material adhesive. Under normal temperature conditions, the polymer material painted on the sticking surface will form a crystalline film with the rapid evaporation of the organic solvent, which will quickly generate adhesive force.
3.The curing agent, also known as the cross-linking agent, can quickly cross-link with the polymer material in the glue under normal temperature conditions, which can quickly improve the initial and final tack strength and enhance the bonding performance.
4.The glue and hardener are sensitive to water and moisture. The water vapor in the air can form a water film on the surface of the film, and the water remaining in the film will form a weak boundary layer, losing its activity, and reducing the bonding strength. The curing agent chemically reacts with water, loses its activity, and cannot achieve cross-linking. Therefore, attention should be paid to waterproof and moisture-proof, and it should not be in contact with water during the storage and operation of the adhesive. The bonding interface must be fully dry and it is not suitable for bonding joints in an environment with a humidity greater than 80%.
5.The glue and hardener are sensitive to dust, grease, oil and other contaminants and chemicals. The bonding interface must be cleaned (do not use water). The cleaning agent must be fully volatilized to keep the interface fully dry.
6.The multi-layer belt joints are bonded by lap jointing, and the lap joint surface is made into a 3-5 level inclined step pattern. The bonding interface is a fabric layer, which is coated with glue on both sides. Attach them closely and apply a certain pressure after the surface of the adhesive film is dry.
Factors to the adhesive curing
The bonding force of the adhesive gradually increases with the extension of time during the curing process. The bonding process of the joint is actually the curing process of the adhesive. Generally, the initial curing is achieved in 30-60 minutes, and the final highest strength of curing is achieved in 24 hours. The longer the standing time, the higher the curing strength.
1.Solvent evaporation rate: In general, the faster the evaporation, the greater the initial stick and the higher the initial bonding strength.
2.Temperature：In general, the higher the temperature, the faster the curing, and the higher degree of curing, the greater the bonding strength.
3.Humidity: In general, the higher the humidity, the slower the curing, the worse degree of curing, and the lower the bonding strength.
Other factors to the bonding strength
- The clean and dry degree of the bonding interface: the cleaner and dry, the more fully the adhesive can infiltrate the fabric, and the stronger the adhesion.
2.The pressure applied on the lap joint: the greater the applied pressure, the more uniform and the stronger the adhesion.
3.The degree of fit between the overlapping surfaces: the tighter the fit, the stronger the adhesion.
Read More: High duty cold vulcanizing adhesive supplier
Cold bonding steps for the conveyor belt at a room temperature
1．Joint making：
1）Along the length of the belt, use a cutting knife, a layer screwdriver, peeling walnut pliers, etc to cut and peel the belt layer by layer to make an oblique stepped lap surface (Figure 1 1/2/3) . Do not injure fabrics such as canvas when cutting each layer, and cut the edge of the belt evenly with the braid layer.
The lap length L:
generally take 0.6~0.8 of the width B of the conveyor belt. The general principle is that the longer the conveyor belt, the longer the lap length.
Beveled section:
Considering the convenience of cutting and pasting, the cutting angle is generally about 30°. In actual operation, generally take the beveled section (small right-angle side) as about half of the width B of the conveyor belt.
Cut the steps:
the purpose is to prolong the service life of the conveyor belt joint. The more steps, the longer the service life and the greater the workload.Comprehensive consideration, the number of steps is generally not less than 3, preferably more than 5 (considered with the number of skeleton layers).
When the two ends of the tape overlap each other, the upper tape should be in the same direction as the running direction. After the two lap joints are made, they should be overlapped together to check the dimensional accuracy, and check whether the braid layering is accurate and suitable, or adjust it. There should be no gap between the steps, and the two stepped overlapping surfaces should be aligned and fitted.
2．Surface treatment：
Use a portable electric wire wheel or wire brush to smooth and evenly roughen the surface to be adhered, remove the residual rubber layer, and roughen the exposed braid body, but do not damage the canvas or other braid body.Brush off the dander, and use cleaning agents (such as acetone, anhydrous ethanol, trichloroethylene) to clean and decontaminate, and let it dry completely.
Do not wash with water. Belts used in humid environments must be dried in the sun or baked with iodine tungsten lamps and infrared lamps to fully dry them
3．Mix adhesives：
Pour the hardener in the aluminum bottle into the iron bucket with glue and mix thoroughly and stir evenly.
According to actual needs, a part of adhesive and hardener can be mixed in other containers according to the weight ratio.
The prepared solvent must be used immediately, and it should be used up within 2 hours of the pot life, that is, it should be controlled within 2 hours from mixing to use. Not for long.
4．Apply adhesive：
Use a short and hard brush to apply the glue evenly in one direction in three times on the fully dry surface to be adhered, and the glue layer should not be too thick or too thin.
After each brushing, the adhesive film reaches the surface dry (that is, after the solvent evaporates, until it does not adhere to the back of the finger and has a sticky feeling), then brush the adhesive again.
5．Dry：
In order to save time, make the glue reach the final curing strength in advance and improve the bonding strength, use iodine tungsten lamp or infrared lamp to bake after each glue application (baking temperature 60 ~ 80 ℃), accelerate the evaporation of the solvent, until no adhesion Brush the glue again when the back of your finger is.
The quick-drying adhesive is flammable, and the vertical distance between the lamp and the overlapping surface shall not be less than 50cm during baking, otherwise the adhesive film will easily burn and catch fire.
Baking and drying is especially necessary when bonding the belt in a low temperature and humid environment.
6．Bonding：
After the third gluing and baking until it does not stick to the back of the fingers, align the two stepped overlapping surfaces, and overlap the two ends of the tape according to the running direction of the belt.
Tapping with hand from the middle to the surrounding area is enough for 2 to 3 times to exhaust the air between the two overlapping surfaces. If blistering occurs accidentally, it can be pierced with a needle and then beaten or crushed.
7．Curing：
After the belt joint is glued, it should be cured at room temperature for 30-60 minutes before tension, and then the site can be cleaned and the production can be run under load.
If conditions permit, prolonging the curing time will make the bonding effect better.
For bonding belts in low temperature or humid environments, in addition to baking, the curing time must be extended to a sufficiently long time, generally 24 hours.
If you have any questions during use or installation, please contact BAI-OTT Coveyor Belt Accessories Company.
