Rubber Seals Swellability
According to the knowledge of organic chemistry, organic solvents can bind to high molecular organic matter, but some polymer organic matter is not easily dissolved, they will adsorb solvent molecules and expand the volume; hydrophilic polymer material will absorb water molecules Volume expansion, which is the so-called polar material swelling.
Swelling properties can also be explained from the principle of similar dissolution, which, at contact or at a certain pressure and temperature, have a miscible effect, but are independent of the gravitational force between molecules.
Swelling properties are one of the commonalities of rubber or polymer.
In some solvents, the crosslinked rubber or other polymer is generally not dissolved, but the solvent molecules will enter the gap in the polymer chain, increasing the volume between the segments, so the volume of polymer due to expansion And swell.
Rubber swelling after the general mechanical properties will be significantly reduced.
Swelling is a very important property of the rubber, so the rubber should be avoided and the polarity of similar solvent contact.
Rubber swell performance for two:
(1) infinite swelling: linear polymer dissolved in a good solvent, can be unlimited absorption of solvent until dissolved into a homogeneous solution so far. So the dissolution can also be seen as the result of infinite swelling of the polymer. For example, natural rubber swells in gasoline.
(2) For the cross-linked polymer and the linear polymer in the poor solvent, the swelling can only be carried out to a certain extent. After the contact with the solvent, the amount of the inhalation solvent is no longer increased, and the system is always Keep the two-phase state. For example, Dingqing rubber (which is a synthetic rubber) can be swollen in liquefied dimethyl ether organic solution.
Dingqing rubber in liquefied dimethyl ether organic solution in the swelling mechanism can be understood as: open the cylinder of the valve, the bottle of liquefied dimethyl ether and the valve within the NBR rubber ring contact, Dingqing rubber will swell; When the cylinder valve closed, the valve gradually "dry", Dingqing rubber swelling gradually decline, the volume of rubber will shrink, with the increase in the number of valve openings and liquefied petroleum gas mixed with dimethyl ether content increased , Dingqing rubber after a number of "swelling - contraction" of the stress cycle, rubber stress decreased, accelerated aging, the final rubber elastic failure and sealing performance decreased, resulting in valve leakage.
Rubber seals are our common kind of sealing device, in various industries, all kinds of machinery and equipment will be applied to a good solution to people to solve the problem of leakage and sealing.
Rubber seals are a kind of universal basic element in the sealing device and play a very important role in sealing. Rubber seals are the most common type of rubber products used in sealing skills. Because the rubber is an extremely flexible polymer material, there is a wide temperature range, in the differential medium to give a smaller stress will produce a greater deformation, this deformation can provide contact pressure, to compensate for leaks, to achieve The purpose of sealing.