Home > KNOWLEDGE > Content

What is the Defining Stress of an O-type hydraulic seal?

May 25, 2018

What is the "Defining Stress" of an O-type hydraulic seal? First of all, we must understand that the hydraulic seal is a seal ring widely used in the chemical and industrial fields to prevent the working medium from leaking out of the housing along the shaft and the outside dust from intruding into the body.


Stress at definite elongation refers to the amount of load per unit cross-sectional area applied when a rubber product specimen is stretched to a given length. It is the material index of a rubber seal product (standard item).

1. What are the “definite stress” factors that affect the hydraulic seal in the engineering environment?


1, the greater the molecular weight of rubber, the greater the constant stress;


2. The force between rubber molecules is large and the tensile stress is high;


3, rubber and plastic material blending can improve the tensile stress and hardness;


4. When the molecular weight distribution is narrow, the tensile stress and hardness decrease;


5. Depreciation stress and hardness decrease as the number of softener increases;


6. The tensile stress and hardness increase as the crosslink density increases. The traditional vulcanization system can obtain higher tensile stress and hardness.


The definite extension stress and hardness increase with the decrease of filler particle size, increase with the increase of structure and surface activity and increase with the increase of filler content.


It can be seen that there are 100%, 200%, 300%, and 500% of the normalized set stress. If a sample with a cross-sectional area of 1 square centimeter is stretched 1 time and a load of 490 N (50 kg force) is required, the 100% set stress is 490 Pa (50 kgf/cm2).


Second, the impact of hydraulic seal specifications material tensile strength factors?


1. The tensile strength of rubber with small molecular weight increases with the increase of molecular weight;


2. The tensile strength of the narrow rubber molecular weight distribution is high;


3, with the increase of rubber crystallinity, tensile strength increases;


4. In the main chain, the tensile strength increases with the intermolecular force.


5. After the orientation of the rubber molecular chains, the tensile strength in the parallel direction increases, and the tensile strength in the vertical direction decreases;


6. The tensile strength decreases with the increase of cross-linking energy, and peaks with the increase of cross-linking density.


7. The surface of the hydraulic seal material contains many oxygen-containing groups, which have high tensile strength, tear strength and elongation;


8, small particles of filler, large surface area, large surface activity, the reinforcement effect is good, but also through the material blending to improve the tensile strength;


9. When the amount of softener exceeds 5 parts, the tensile strength of the vulcanizate will decrease.