How is rubber hardness accurately calculated?
The theoretical calculation of rubber compound refers to the calculation of the mass, volume, and proportion of each component in the formula, to predict the physical properties of rubber, especially the characteristics of hardness, density, volume, filler distribution, etc. These calculations provide a basis for the design and development of rubber products and also help engineers optimize formulations when developing new products. Here are a few key steps and methods in the theoretical calculation of rubber compounds.
What is Rubber Hardness?
Rubber hardness refers to the ability of rubber materials to resist deformation under the action of external forces, which can also be understood as its "softness and hardness". The higher the hardness, the stronger the resistance to deformation of the rubber; The lower the hardness, the softer the rubber.
Hardness is not only an indicator to measure the performance of rubber but also directly affects the wear resistance, fatigue resistance, and compression performance of rubber products. Therefore, different application scenarios have different hardness requirements for rubber, for example, car tires usually require a high hardness, while rubber seals need a moderate hardness to ensure their elasticity and tightness.
Common test methods for rubber hardness
There are many ways to test rubber hardness, The two most common methods are Shore Hardness and International Rubber Hardness Degree (IRHD). Among them, Shore hardness is divided into type A, type D, etc., according to the different hardness of the rubber, choose the appropriate hardness tester.
Shore hardness
Shore hardness is a method of characterizing hardness by measuring the degree of indentation of a rubber surface. It presses a conical or spherical indenter into the rubber surface under a certain load, records the depth of the indenter into the rubber, and then calculates the hardness value through a certain formula.
There are different types of Shore hardness:
· Shore A hardness: used to measure soft rubber, such as car tires, sealing rings, etc.
· Shore D hardness: used to measure harder rubber materials, such as engineering rubber.
The specific test process is as follows:
· Place the rubber sample under the hardness tester and keep it stable;
· By applying a certain force, the indenter of the hardness tester is pressed into the sample;
· Record the depth of indentation and derive the hardness value according to the scale of the hardness tester.
Shore A hardness usually ranges from 0 to 100, with higher values representing harder rubber. For example, a piece of rubber material with a hardness of 60 Shore A is harder than a material with a hardness of 30 Shore A.
IRHD (International Rubber Hardness)
Similar to Shore hardness, IRHD characterizes material hardness by measuring the depth at which the indenter is pressed into the rubber. The difference is that the IRHD hardness uses different indenter shapes and loading forces, making it more suitable for measuring thin-walled rubber products.
IRHD hardness measurements are typically expressed on a scale of 0 to 100, where 0 represents extremely soft material and 100 represents complete rigidity.
Mohs hardness
Mohs hardness is primarily used to test mineral and ceramic materials, but it is also sometimes involved in abrasion testing of rubber materials. Mohs hardness differs from the above two methods in that it is based on the ability of different materials to scratch each other.
