Mechanical Testing and Corrosion Resistance of Rubber

Tensile Performance

Under the specified test temperature, humidity and tensile speed test, by applying a tensile load to the longitudinal axis of the rubber sample, the sample is deformed until the material is destroyed.

Influencing Factors

(1) Preparation and treatment of samples: sampling with raw materials or direct sampling from products.

(2) Test chamber: accuracy of load cell, speed control accuracy, fixture, coaxiality and data acquisition frequency, etc. The stretching speed should be stable and even, and the high or low speed will affect the stretching result.

(3) Test environment: the main influencing factors are temperature and humidity.

(4) Test process: In general, the tensile speed is fast, the yield stress and tensile strength increase, and the elongation at break will decrease. During high-speed stretching, the movement of molecular segments cannot keep up with the speed of external forces, and the rubber exhibits brittle behavior, showing increased tensile strength and reduced elongation at break.

(5) Data processing: In addition to the test data collected by the temperature controlled chamber system, it is also necessary to consider the test and calculation data, such as sample size, displacement change, elongation calculation and offline test.

Bending Performance

The first method used to determine the bending properties of rubber is a three-point load system, and the second method is a four-point load system.

Influencing Factors

Span-thickness ratio: when selecting the span-thickness ratio, comprehensive influence factors such as shear force, horizontal thrust of the bearing, and indentation of the indenter must be considered comprehensively.

Strain rate: under the same test thickness, the greater the span, the smaller the strain rate, the larger the test speed, the greater the strain rate.

The arc radius of the loading indenter and the support: the arc radius of the loading indenter is too small, causing the quality inspection of the indenter and the sample to be not line contact, but surface contact; if the radius of the indenter is too large, it will be Increase the influence of shear force, easy to produce shear fracture.

Temperature: Bending strength decreases with increasing temperature, but the degree of decrease varies.

Operational influence: measurement of sample size, adjustment of sample span, line contact and vertical condition of indenter and sample, and adjustment of zero point of deflection value.

Compression Performance

Compression performance is to describe the behavior of the material under lower compressive load and uniform loading rate.

Compression properties include elastic modulus, yield stress, deformation beyond the yield point, compressive strength, compressive strain, and slenderness ratio.

In practical applications, the compressive load is not always applied instantaneously. Therefore, the standard test results of the time dependence of the rigidity and strength of plastics cannot be used as the basis for designing parts.

The test is to place the sample between the two pressure plates of the testing machine, and apply a measurable force of equal magnitude and opposite direction at a constant rate along the main axis of the two end surfaces of the sample to make the sample along the axis. The direction is shortened, while the radial direction is increased, resulting in compression deformation until the sample ruptures, yields or the sample deformation reaches a predetermined number.

Influencing Factors

Sample material: For example, the internal stress distribution of the material, the material structure, the method of forming the sample, etc..

Test Conditions: for example, sample shape, sample size, surface roughness or friction of the upper and lower platens of the testing machine, and test speed.

Conclusion: 

The tensile properties of rubber will decrease and the compression permanent deformation will increase under ozone corrosion.

The corrosion degree of rubber in the tensile state is weaker than that in the free state.

Rubber corrosion will occur softening, sticky, deformation, expansion, foaming, cracking phenomenon.

Aging, swelling and decompression damage of rubber are the failure forms of rubber seals in practical work. Therefore, should be specific to the specific situation, choose the right rubber material.