The tensile properties of rubber
Testing of tensile properties of vulcanized rubber
Any rubber product is used under certain external force conditions, so it is required that rubber should have certain physical and mechanical properties, and the most obvious performance is tensile performance. When conducting finished product quality inspection, designing rubber material formula, determining process conditions, and comparing rubber aging resistance and medium resistance, it is generally necessary to evaluate the tensile performance. Therefore, tensile performance is one of the important routine items of rubber.
The tensile performance includes the following items:
1. Tensile stress (S)
The stress generated by the specimen during stretching is the ratio of the applied force to the initial cross-sectional area of the specimen.
2. tensile stress at a given elongation (Se)
The tensile stress at which the working part of the specimen is stretched to a given elongation. Common tensile stresses include 100%, 200%, 300%, and 500%.
3. Tensile strength (TS)
The maximum tensile stress at which the specimen is stretched to break. Formerly referred to as tensile strength and tensile strength.
4. Elongation percentage (E)
The deformation of the working part caused by the tensile specimen is the ratio of the increment of elongation to the initial length percentage.
5. Elongation at a given stress (Eg)
The elongation of the specimen under a given stress.
6. Elongation at break (Eb)
The elongation of the sample at break.
7. Breaking permanent deformation
Extend the specimen until it fractures, and then subject it to the remaining deformation after a certain time (3 minutes) of recovery in its free state. The value is the ratio of the incremental elongation of the working part to the initial length.
8. Tensile strength at break (TSb)
The tensile stress of a tensile specimen at fracture. If the specimen continues to elongate after the yield point and is accompanied by a decrease in stress, the values of TS and TSb are different, and the TSb value is smaller than TS.
9. Tensile stress at yield (Sy)
The stress corresponding to the first point on the stress-strain curve where the strain further increases but the stress does not increase.
10. Elongation at yield (Ey)
The strain (elongation) corresponding to the first point on the stress-strain curve where strain further increases but stress does not increase.
11. Rubber compression permanent deformation
Some rubber products (such as sealing products) are used in a compressed state, and their compression resistance is one of the main properties that affect product quality. The compression resistance of rubber is generally measured by compression permanent deformation. When rubber is in a compressed state, it inevitably undergoes physical and chemical changes. When the compression force disappears, these changes prevent the rubber from returning to its original state, resulting in permanent compression deformation. The magnitude of compression permanent deformation depends on the temperature and time of the compression state, as well as the temperature and time at which the height is restored. At high temperatures, chemical changes are the main cause of compression permanent deformation of rubber. Compression permanent deformation is measured after removing the compressive force applied to the specimen and restoring the height at standard temperature. At low temperatures, the changes caused by glassy hardening and crystallization are the main factors in the test. When the temperature rises, these effects disappear, so it is necessary to measure the height of the specimen at the test temperature.
There are currently two national standards for measuring the compression permanent deformation of rubber in China, namely the determination of compression permanent deformation at room temperature, high temperature, and low temperature for vulcanized rubber and thermoplastic rubber (GB/T7759) and the determination method for constant deformation compression permanent deformation of vulcanized rubber (GB/T1683)
Post time: Apr-01-2024
