The quality of the rubber compound has a decisive influence on its subsequent processing properties and the quality of semi-finished products, as well as the physical and mechanical properties of the vulcanizate and finished products. The main performance indicators that determine the quality of the mixed rubber are the plasticity or viscosity of the mixed rubber, the dispersity of the compounding agent and its mixing uniformity, and the physical and mechanical properties after vulcanization. Therefore, the following items are usually checked.
1. Fast inspection of rubber materials
The traditional quick inspection items for checking the quality of compound rubber include plasticity, density and hardness, which must be checked on a vehicle-by-vehicle basis.
(1) Determination of plasticity
Take three samples from different parts of each rolling compound, and measure their Vickers plasticity or Wallace plasticity to see if their size and uniformity meet the requirements. Its Mooney viscosity can also be measured. If the plasticity of the rubber is too small or the Mooney viscosity is too high, the processing performance of the rubber will be poor; on the contrary, if the plasticity is too large or the Mooney viscosity of the rubber is too low, the rubber will be over-refined, which will damage its vulcanizate. The physical and mechanical properties of the rubber compound are not uniform; the plasticity or Mooney viscosity of the rubber compound is not uniform, indicating that the mixing quality is not uniform.
(2) Determination of relative density
Less addition, more addition and omission of compounding agents will make the relative density of the compounded rubber not meet the specified standards; uneven dispersion of compounding agents will make the density of the rubber compound uneven, so it is easy to measure the relative density and fluctuation of the compound. It can be judged whether the mixing operation is correct and whether the mixing quality is uniform. The specific method is to take samples from three different parts of each roll of rubber compound and measure them according to the standard method. If the density and uniformity of the rubber material do not meet the requirements, the quality of the rubber material does not meet the requirements, and corresponding measures should be taken to remedy or deal with it.
(3) Hardness determination
Take the rubber material of three different parts of each batch of mixed rubber, and measure whether the hardness of the vulcanized rubber sample meets the standard or whether each part is uniform.

2. Determination of physical and mechanical properties
A comprehensive inspection of the quality of the compounded rubber must also spot-check or regularly measure the physical and mechanical properties of the vulcanizate. Conventional physical and mechanical properties testing items such as tensile strength, elongation and hardness can be used to judge whether the rubber meets the quality requirements. It is also necessary to select special performance items for testing according to the different performance requirements of the rubber compound, such as the measurement of wear performance of tread rubber, and the measurement of tear performance of inner tube rubber, so as to identify the quality of the compounded rubber.

3. Dispersion inspection of compounding agents
The dispersity of the compounding agent in the rubber compound is an important parameter to characterize the uniformity of mixing, and it is the most important factor to determine the quality of the mixed rubber.
For the carbon black compound, the most important factor affecting the quality of the compound is the dispersion state of the carbon black in the compound, so the determination of the dispersity of the carbon black is an important part of evaluating the quality of the carbon black compound.

Fourth, the inspection of the vulcanization characteristics of the rubber
In order to quickly identify the quality of the rubber compound, an oscillatory rheometer is also widely used to measure the vulcanization curve of the rubber compound. Since the cure curve is very sensitive to changes in mixing conditions, the rheometer can also be used to evaluate the uniformity of compound properties. Take samples from different parts of the same roller for testing. If their vulcanization curves basically overlap, it means that the performance of the rubber is uniform; on the contrary, it shows that the performance of the rubber is not uniform and the quality is not good. If the composition of the compound is changed, its vulcanization curve is also very clearly shown in shape. Therefore, as long as the vulcanization curve of the tested compound is compared with the standard curve, it can be checked whether the compound is qualified.