Conveyor belt is the main component of material conveying and an important part of national economy. With the improvement of mechanization and automation technology in China, the demand of conveyor belt increases year by year and the varieties and specifications keep 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. Conveyor belt industry is closely related to industrial and agricultural production and people's life, and has a certain role in the development of China's national economy and scientific and technological progress.
General-purpose cloth-core conveyor belt is made of natural rubber or synthetic rubber such as SBR or SBR as the main rubber material. Oil can penetrate these rubbers and make them swell, which leads to a decrease in the strength and other mechanical properties of the rubber. In other words, these rubbers are less tolerant of various oils and organic solvents. When conveying such materials, oil can have a dissolving and erosive effect on the rubber covering the belt surface, causing the rubber covering the belt surface to increase in volume, swell and deform, and extract certain functional compounds from the belt. Rubber coverings. As a result, the physical and mechanical properties of the belt are reduced and the service life is shortened. The development of oil-resistant conveyor belt is based on this need. It is made of cotton canvas, polyester-cotton interwoven canvas, nylon canvas, polyester canvas and other carcass materials by calendering, molding and vulcanization processes. It has good oil resistance. It is suitable for use under working conditions where oily materials are conveyed and where oily or chemical solvents may be present.
Influence of rubber variety 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 swells the vulcanized rubber and at the same time extracts functional compounds from the rubber, which leads to a decrease in physical properties. Mechanical properties of the vulcanized rubber. When considering the choice of rubber, the first consideration is oil resistance, followed by the specific use conditions and specific performance indicators of oil-resistant conveyor belts for formulation adjustment.
Fluorine rubber has better oil resistance than other rubbers, good temperature resistance, and can be used at 200-250 degrees, but poor cold resistance, and is only elastic above -20 degrees. However, due to its high elasticity and high strength. It does not break down at temperatures from -40°C to 50°C. However, it is expensive and has poor technical properties. The processing is complicated.
Acrylate rubber has good resistance to petroleum media. It is resistant to sulfur-containing oils and lubricants up to 175°C. In petroleum media, it is heat resistant up to 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 much more difficult.
Neoprene can remain elastic between -50 and 100 degrees. Among all oil-resistant rubbers, neoprene has the worst resistance to petroleum media, but good resistance to animal oil.
NBR is a general-purpose oil-resistant rubber with better oil resistance than neoprene. The acrylonitrile content in NBR increases its oil and heat resistance, while its cold resistance decreases. Depending on the type and formulation of NBR, it can be used in the temperature range of minus 30 degrees to minus 50 degrees and 100 degrees to 150 degrees. The swellability of different oils is related to the acrylonitrile content, extractables, vulcanization system, and amount of compounding agent. The swelling values in oils range from about -10% to +30%. In recent years, the development of hydrogenated NBR has significantly improved the heat resistance and oil resistance of NBR, which is a new type of oil-resistant rubber with very broad application prospects. NBR and phenolic resin.
Transition rubber formulation design
The main body of oil-resistant conveyor belt cover rubber NBR is polar rubber, while the natural rubber and styrene-butadiene rubber used in the adhesive of the belt core layer are non-polar rubber with large polarity difference, not easy to bond, and the interface of two different rubbers is very obvious when peeling. The adhesion is very low.
For this reason, it is necessary to design a transition adhesive that can solve the problem of good adhesion of cover rubber and core rubber and vulcanize them together. The transition rubber plays the role of firmly bonding the cover rubber to the canvas core of the conveyor belt and is related to the overall bonding performance of the oil resistant conveyor belt.
The key of this formula is to make it have good bonding performance with full NBR cover rubber and good bonding performance with common synthetic rubber adhesive.