Several Implications of Process Performance Index of Silicone Rubber
(1) Watch drying time
It refers to the time when a single component RTV silicone rubber loses its stickiness when it is exposed to atmospheric solidification and touches its appearance with its finger. Generally speaking, it refers to the time distance when the silicone rubber plane sealant is extruded and aired without touching hands.

(2) Curing depth
It refers to the thickness of the silicone rubber plane sealant cured from outside to inside within a certain time after sizing, such as 2-3mm/24h, 0.6mm/h, etc.

(3) Extrudability (defined in accordance with ASTM C1183 specification)
According to the requirements of ASTM C1183 specification, the extrusion weight per unit time is called extrudability under specific pressure conditions by using Semco tubes and special rubber nozzles (diameter 3.2mm).

(4) Instant sealing pressure
Silicone rubber plane sealant is sizing on the flange plate with a certain diameter, then closing immediately, controlling the reasonable thickness of the rubber layer, and then applying pressure according to a certain rate, the maximum pressure it receives is the immediate sealing pressure.

(5) Curing characteristics in oil
It means that the silicone rubber plane sealant is put into a fixed die, and then the die is put into the oil. The thickness of the silicone rubber plane sealant cured from outside to inside in a certain period of time is recorded to characterize the curing characteristics of the silicone rubber plane sealant in the oil.

(6) Shear Strength Adherence Rate of Drying Time
It refers to the shear strength of the shear specimens which have been sizing for a certain period of time under the specific high temperature and humidity conditions, then stop closing and bonding, and stop curing for 168 hours under the standard conditions, then test their shear strength, and compare with the shear strength of direct bonding and curing for 168 hours under the standard conditions, and calculate the strength adherence rate.

(7) Thermal stability without curing
It refers to putting the uncured silicone rubber plane sealant in the high temperature environment for a certain period of time, and then curing under the standard conditions. It clarifies that the silicone rubber plane sealant is stable under this temperature condition. If the thermal stability temperature of sealant is more than 100 C, it means that the uncured sealant can continue to cure after heating at 100 C.

According to the different content of phenyl in silicone rubber (phenyl: silicon atom), it can be divided into low phenyl, medium phenyl and high phenyl silicone rubber. When the rubber crystallizes or approaches the glass transition point or the two conditions overlap, the rubber will be rigid. The regularity of polymer chains is destroyed by introducing a suitable amount of large groups, which can reduce the crystallization temperature of polymers. At the same time, the glass transition temperature can also be changed because the introduction of large groups changes the intermolecular force of polymers. Low phenyl silicone rubber (C6H5/Si=6-11%) has excellent low temperature resistance due to the above reasons, and has nothing to do with the type of phenyl monomer used. The brittleness temperature of vulcanizate is - 120 C, which is the best low temperature rubber nowadays. Low phenyl silicone rubber has both advantages of vinyl silicone rubber and low cost, so it has the tendency to replace vinyl silicone rubber. When the phenyl content is greatly increased, the rigidity of the molecular chain will increase, which will lead to the decrease of cold resistance and elasticity, but the ablation resistance and radiation resistance will be improved. The phenyl content of C6H5/Si = 20-34% is medium-phenyl silicone rubber with ablation resistance, while the high-phenyl silicone rubber (C6H5/Si = 35-50%) has excellent radiation resistance. Performance.