Rubber is a highly elastic polymer, its molecular structure is a chain, the molecular chain has a high flexibility. The molecular chain of rubber can be cross-linked (vulcanized), and the cross-linked material has the ability to recover quickly when it is deformed by external force, and has good physical and mechanical properties and chemical stability. Rubber can only be cross-linked to become a valuable high-elastic material, commonly known as rubber. Rubber is the basic raw material of rubber industry, widely used in the manufacture of tires, hose, tape, cables and other rubber products. It is equal to metals, chemical fibers and plastics as important materials.
Rubber is divided into natural rubber and synthetic rubber according to raw materials. According to the performance can be divided into general type and special type. General rubber refers to the variety with good comprehensive performance and wide application, including natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber and so on. Special rubber refers to rubber with some special properties, including neoprene rubber (NC111), butadiene rubber, silicone rubber, fluorine rubber, polyurethane rubber, polysulfide rubber, chlorohydrin rubber, acrylic rubber, etc.
Rubber hardness refers to the resistance of colloids under force, which is used to describe the hardness of rubber materials. The hardness of rubber is an important index to evaluate the properties of rubber materials, which measures the flexibility and hardness of rubber hard materials. Due to the advantages of rubber materials such as scalability, flexibility, tensile strength and wear resistance, it has been widely used in various industries.
The hardness of rubber is measured by the surface thickness of the rubber test piece and the surface deformation generated by the standard indenter between the sample surfaces. In general, when the compression pressure is a certain value, the smaller the deformation value, the higher the hardness of the rubber material. The hardness of rubber directly affects the physical properties of rubber materials. The higher the rubber hardness, the stronger the wear resistance and extrusion resistance of the rubber material. In addition, the flexibility of rubber materials will also be affected by hardness, in general, the higher the hardness, the worse the flexibility. Therefore, when selecting rubber materials, the hardness of rubber materials should be determined according to the actual use environment to meet its specific performance needs.
The hardness of rubber is an index to quantify the mechanical properties of rubber, which can help us to establish the connection between the molecular configuration of rubber and the material behavior, mechanical properties and control its application performance, so as to effectively evaluate the mechanical properties of rubber and its application range. To put it bluntly, from a macro point of view, the hardness of rubber is the touch and stiffness characteristics of rubber materials, which determines the mechanical properties of rubber products under certain conditions, and these properties affect the actual use of rubber products.
The factors that affect rubber hardness are as follows:
Material composition
The hardness of rubber has a great relationship with its material composition, mainly because the hardness is related to the molecular structure of the material and its cross-linking density. In general, styrene butadiene rubber is harder than natural rubber, and nitrile butadiene rubber is harder than sheepskin rubber.
Curing agent
Vulcanizing agent is the key material of rubber vulcanization. Thermodynamically, the addition of vulcanizing agent can enhance the hardness and wear resistance of rubber. Using a small amount of vulcanizing agent can make the rubber hard, and increasing the quality of the vulcanizing agent can make the rubber harder.
Filling material
Filler is a material commonly used to increase the hardness of rubber, and the choice and concentration of filler can affect the hardness and other physical properties of rubber materials. Ordinary carbon black is a widely used filler, but with the increase of the filling amount, the mechanical properties and piston density of rubber will decrease, and the hardness will also decrease.
Vulcanization temperature
The hardness of rubber has a great relationship with the vulcanization temperature, and the higher the vulcanization temperature, the greater the hardness of rubber. However, too high vulcanization temperature will cause the strength and elasticity of rubber to be reduced.
Curing time
Vulcanization time refers to the time required for rubber vulcanization reaction to complete. The length of curing time directly affects the hardness and strength of rubber, under normal circumstances, the longer the curing time, the greater the hardness of rubber. However, too long a time will cause the rubber to become brittle, and too short a time can lead to insufficient hardness of the rubber material.
In summary, there are many factors that affect the hardness of rubber, including material composition, curing agent, filling material, curing temperature and curing time. In the actual production process, reasonable selection and control should be carried out according to the specific application requirements and the characteristics of the material to achieve the best rubber hardness and performance. (2024-01-07)
