The conveyor belt is the main part of material conveying, and also an important part of the national economy. With the improvement of mechanization and automation technology in China, the demand for conveyor belts is increasing year by year and the types and specifications are increasing; It is widely used in various industries such as chemical industry, metallurgy, coal, mining, port, building materials, electromechanics, light industry, textile, agriculture, and automobile. The conveyor belt industry is closely related to industrial and agricultural production and people’s life and plays a certain role in the development of China’s national economy and scientific and technological progress.
General-purpose fabric-core conveyor belts are made from natural rubber or synthetic rubber such as SBR or SBR as the main rubber material. Oil can penetrate these rubbers and make them swell, resulting in a reduction in the strength and other mechanical properties of the rubber. In other words, these rubbers are less resistant to various oils and organic solvents. When conveying such materials, the oil will have a swelling and erosive effect on the rubber covering the surface of the belt, increasing the volume of the rubber covering the surface of the belt, expansion and deformation, and the extraction of certain functional compounds from the rubber covering. As a result, the physical and mechanical properties of the belt are reduced and the service life is shortened. The development of the oil-resistant conveyor belt is based on this need. It is made of cotton canvas, polyester-cotton interweaved canvas, nylon canvas, polyester canvas, and other carcass materials, through the process of calendering, forming, vulcanization, and other processes. It has good oil resistance. It is suitable for conveying oily materials and for use under working conditions where oily or chemical solvents may be present.
Design of the formulation
Influence of rubber species selection on oil resistance performance
The main factor affecting the life of oil-resistant conveyor belts is the penetration of oil into the vulcanized rubber, which causes the vulcanized rubber to swell and at the same time extracts the functional compound from the rubber, thus leading to a decrease in the physical and mechanical properties of the vulcanized rubber. When considering the choice of rubber, the first thing to consider is oil resistance, followed by the specific conditions of use and specific performance indicators of oil resistant conveyor belts for formulation adjustment.
Fluorine rubber is better than other rubbers in oil resistance and has good temperature resistance, and can be used at 200-250 degrees, but its cold resistance is poor, and it is only elastic at -20 degrees or more. However, due to its high elasticity and high strength. It will not be damaged at -40°C to 50°C. However, it is expensive and has poor technical properties. The processing process is complicated．
Acrylate rubber has good resistance to petroleum media performance. At 175 degrees below, it can resist sulfur-containing oils and lubricants. In the petroleum medium, the heat-resistant temperature can reach about 220 degrees. Its biggest disadvantage is that it is not resistant to water, has permanent deformation at room temperature, and cannot be vulcanized with sulfur. Processing is more difficult.
Neoprene can maintain elasticity between -50 and 100 degrees. In all the oil-resistant rubber, neoprene resistance to petroleum media performance is the worst, but good resistance to animal oil.
NBR is a general oil-resistant rubber, its oil resistance is better than neoprene, with the acrylonitrile content in nitrile rubber to increase its oil resistance and heat resistance, while the cold resistance decreases. Depending on the type and formulation of the nitrile rubber, it can be used at temperatures ranging from minus 30 degrees to minus 50 degrees and 100 degrees to 150 degrees. The swelling in different oils is related to the acrylonitrile content, the extractable, the vulcanization system, and the quantity of the compounding agent. The swelling values in oil range from about -10% to +30%. In recent years, the development of hydrogenated nitrile rubber has significantly improved the heat resistance and oil resistance of nitrile rubber is a very broad application prospect of new oil-resistant rubber. Nitrile rubber and phenolic resin, try nylon or polyvinyl chloride blend, can also significantly improve oil resistance, and oil resistance with the number of resin increases and increases.
Design of the transition rubber formulation ．
Nitrile rubber, the main body of the covering rubber of the oil-resistant conveyor belt, is a polar rubber, while the natural rubber and styrene-butadiene rubber used for the adhesive of the belt core layer are non-polar rubbers, which have large polarity differences and are difficult to bond, and the interface of the two different rubbers is very obvious when peeling. The adhesion is very low.
For this reason, it is necessary to design a transition rubber that can solve the problem of good adhesion between the cover rubber and the core adhesive and can be vulcanized together. The transition adhesive plays a role in the solid bonding of the cover adhesive to the canvas core of the conveyor belt and is related to the overall bonding performance of the oil-resistant conveyor belt.
The key point of the formulation is to make it have a good bonding performance with the full NBR cover rubber and a good bonding performance with the common synthetic rubber adhesive.