It is divided into: fabric core conveyor belt and non-fabric core conveyor belt.
Fabric core conveyor belt is divided into two types: layered fabric core and whole core;
Layered fabric core conveyor belt is divided into: cotton canvas core, nylon core and polyester core conveyor belt;
The whole core conveyor belt is divided into PVC and PVG whole core conveyor belts;
Non fabric core conveyor belt is divided into: steel wire rope conveyor belt, metal mesh core conveyor belt and steel cable conveyor belt. (including high strength nylon conveyor belt) the product shall comply with gb7984-2001 standard.
Covering layer: the tensile strength shall not be less than 15MPa, the breaking extension length shall not be less than 350 percent , the wear amount shall not be less than 200mm3, the average value of longitudinal samples of interlayer bonding strength shall not be less than 3.2n/mm between cloth layers, and between covering adhesive and cloth layers shall not be less than 2.1 n / mm
The full thickness longitudinal elongation at break shall not be less than 10 percent , and the full thickness longitudinal reference force elongation shall not be greater than 1.5 percent
Nylon (NN), polyester (EP) conveyor belt:
The average value of longitudinal sample of interlayer bonding strength shall not be less than 4.5n/mm between cloth layers, and not less than 3.2n/mm between covering adhesive and cloth layers
The full thickness longitudinal elongation at break shall not be less than 10 percent , and the full thickness longitudinal reference force elongation shall not be more than 4 percent . The product shall comply with mt147-95 standard.
Conveyor belt: it is the main component for pulling and carrying materials. When selecting, cotton canvas, polyester canvas or nylon canvas belt shall be used according to the tension. Other parts of the conveyor are designed to meet various belt strength requirements. Mechanical joints, cold rubber joints and vulcanization joints can be used for conveyor belt connection according to different working conditions.
Mastering method of vulcanization process of rubber conveyor belt:
To understand the vulcanization process of rubber belt, we mainly need to master the essence of vulcanization and the factors affecting vulcanization, the determination and implementation method of vulcanization conditions, the operation method and structure of flat vulcanizer. Vulcanization is the process of crosslinking the linear macromolecules of rubber mixture at a certain temperature, time and pressure to form a three{{0}}dimensional network structure. Vulcanization reduces the plasticity and increases the elasticity of rubber, The ability to resist external force deformation is greatly increased, and other physical and chemical properties are improved, making rubber an engineering material with use value. Vulcanization is the last process in the processing of rubber products. The quality of vulcanization has a great impact on the performance of vulcanized rubber. Therefore, the vulcanization conditions should be strictly controlled, and the pressurizing surfaces of the two hot plates of the vulcanizer should be parallel to each other, The hot plate is heated by steam or electricity. During the whole vulcanization process, the pressure applied on the die cavity area of the flat plate shall not be less than 3 MPa. No matter what type of hot plate is used, the temperature distribution on the whole die area shall be uniform, and the maximum temperature difference between each point in the same hot plate and between each point and the center point shall not exceed one degree, The temperature difference at the corresponding position between the two adjacent plates shall not exceed one degree, and the maximum temperature difference at the center of the hot plate shall not exceed 0.5 degrees. The common technical specifications are the maximum closing pressure of 200 tons, the maximum stroke of the plunger is 200 mm, the plate area is 500 500 mm, the number of working layers is one layer, and the total heating power is 27 kW;
For the operation of vulcanization test, the film after mixing shall be parked for 24 hours according to the regulations before cutting for vulcanization. The cutting method is sheet tension and other test or strip samples are cut on the rubber with scissors. The width direction of the rubber belt test piece shall be consistent with the calendering direction of the rubber. The volume of the rubber shall be slightly larger than the volume of the mold, and its weight shall be weighed with a balance, The mass of rubber blank is calculated according to the following method: the mass of rubber blank is equal to the volume of mold cavity multiplied by the density of rubber compound multiplied by 1.05. In order to ensure sufficient amount of rubber during molding vulcanization, the actual amount of rubber compound is increased by 5 percent compared with the calculated amount. After cutting, label the number and vulcanization conditions on the edge of rubber blank. Take another film of about 2mm and take the height of sample as the width, Press to cut the rubber strip along the vertical direction and roll it into a circular cylinder. The cylinder shall be rolled tightly without gap. The volume of the cylinder shall be slightly smaller than the mold cavity and the height shall be higher than the mold cavity. The paper label with number and vulcanization conditions shall be pasted on the bottom of the cylinder, and then the rubber shall be cut into a circular film sample according to the requirements. If the thickness is not enough, the film can be stacked, Its volume shall be slightly larger than that of the mold cavity. Stick a paper label with number and vulcanization conditions on the bottom of the circular sample, adjust and control the plate temperature according to the required vulcanization temperature to make it constant, preheat the mold on the closed plate until the specified vulcanization temperature is within the range of plus or minus one degree, and keep it at this temperature for 20 minutes. It can no longer be preheated during continuous vulcanization, During vulcanization, only one mold is allowed for each layer of hot plate. When the vulcanizer is working, the pump provides vulcanization pressure. The vulcanization pressure is indicated by the pressure gauge. The pressure value can be adjusted by the pressure regulating valve. Put the rubber blank checking the number and vulcanization conditions into the preheated mold as soon as possible, close the mold immediately and place it in the center of the plate, After the upper and lower vulcanization models are aligned in the same direction, apply pressure to make the plate rise. When the pressure gauge indicates the required working pressure, properly relieve the pressure and exhaust for about three to four times, then make the pressure reach the maximum, start to calculate the vulcanization time, release the pressure and start the mold immediately after the vulcanization reaches the predetermined time, take out the sample, close the mold, exhaust The vulcanization time and mold opening are automatically controlled. The vulcanized conveyor belt sample can be cut off the rubber edge, and the performance test can be carried out after parking at room temperature for ten hours;
For the rubber compound with determined formula, there are three factors affecting the quality of vulcanizate: vulcanization pressure, vulcanization temperature and vulcanization time, also known as the three elements of vulcanization. The purpose of applying pressure to the rubber material during vulcanization is to make the rubber material flow in the mold cavity, fill the grooves or patterns, prevent bubbles or lack of rubber, and improve the compactness of the rubber material, Enhance the adhesive strength between rubber and cloth layer or metal; It is helpful to improve the physical and mechanical properties of the compound, such as tensile property, wear resistance, bending resistance, aging resistance, etc. it is usually determined according to the plasticity of the compound and the product structure of the rubber belt sample. For example, if the plasticity is large, the pressure should be smaller; The pressure with large thickness, many layers and complex structure should be greater. The vulcanization temperature directly affects the vulcanization reaction speed and vulcanization quality. The influence of vulcanization temperature on the vulcanization speed is very obvious, that is, increasing the vulcanization temperature can accelerate the vulcanization speed of the belt, but high temperature is easy to cause the cracking of rubber molecular chain, resulting in vulcanization reduction, It leads to the decline of physical and mechanical properties, so the vulcanization temperature should not be too high. The appropriate vulcanization temperature should be determined according to the compound formula, which mainly depends on the type of rubber and vulcanization system. The vulcanization time is determined by the compound formula and vulcanization temperature. For a given compound, there is the most appropriate vulcanization time under certain vulcanization temperature and pressure, Too long or too short time will affect the properties of vulcanizate. We can determine the appropriate vulcanization time by instrument.
Mechanical parameters of vulcanizate for rubber conveyor belt
1. Hardness: hardness is the ability of rubber to resist external force. At present, two typical rubber hardness meters are widely used to measure hardness in the world, one is shore hardness meter; The other is the international rubber hardness tester. The most commonly used shore a hardness tester is shore a hardness tester, and the measured hardness value is very close to the international rubber hardness value;
2. Abrasion: it refers to the phenomenon that the rubber surface is worn off due to the action of friction. There are many kinds of instruments used in the abrasion test, among which the more important ones are as follows:
(1) Akron abrasion tester is widely used in China, and there is only British standard abroad. In the national standard gb-82 implemented in 1982, the content of using sample abrasion index to characterize rubber abrasion performance is added;
(2) At present, only a few countries have included the instrument in their national standards, which are generally divided into constant load method and fixed torsion method;
(3) The Schopper abrasion tester is also called DIN tester. The international organization for standardization has decided to recommend the test method of the Schopper abrasion tester as the international standard;
(4) The wear tester is mainly used to measure the wear resistance of tread rubber, and can also be used to identify the wear resistance of soft rubber and other elastic materials. The pike wear tester is characterized by using two tungsten carbide knives with specific shape and certain sharpness to cut the rubber sample rotating at a certain speed under the action of fixed load, and determine the weight of the material worn off during the test time, The pick-up wear tester can better reflect the wear of tires on the road;
(5) Mnp-1 abrasion instrument is unique to the former Soviet Union. Its characteristic is that it can widely change the test parameters. For example, the load can be 0.5N, the temperature is 40.130 degree , and the test range is relatively wide;
3. Fatigue: fatigue test is to simulate and reproduce the main service conditions of rubber products in the laboratory, so as to quantitatively measure the fatigue resistance of the products, which is often characterized by fatigue life;
Fatigue tests are generally divided into three categories according to different forms of applied force:
(1) Compression fatigue test is to compress the sample repeatedly with a certain frequency and a certain deformation range, and measure its temperature and deformation. The instrument has constant deformation, constant stress and constant energy;
(2) The flexion cracking test is used to determine the flexion times when the rubber cracks due to multiple flexions, or to determine the crack extension length when a certain number of flexions;
(3) Tensile fatigue test;
4. Test of compression permanent deformation: the vulcanization state of rubber can be judged through compression permanent deformation, and the ability of products to resist static compression stress and shear stress can be understood. There are two measurement methods, namely constant compression permanent deformation and static compression deformation;
5. Test of effective elasticity and hysteresis loss: effective elasticity refers to the percentage of the ratio of the work recovered during sample shrinkage to the work consumed during elongation when the sample is stretched to a certain length on the tensile machine. Hysteresis loss refers to the percentage of the ratio of the work lost during shrinkage to the work consumed during elongation when the sample is measured on the tensile machine.
