(1) Surface dry time

It refers to the time that the one-component room temperature vulcanized silicone rubber loses its viscosity when it is exposed to the atmospheric environment and the surface is touched with a finger. General refers to the time distance that the silicone rubber plane sealant is extruded and left to dry under standard conditions, and the surface does not touch the hands.

(2) Curing depth

It refers to the thickness of the adhesive layer that the silicone rubber plane sealant is cured from the outside to the inside within a certain period of time after sizing under standard conditions, such as: 2 ~ 3mm/24h , 0.6mm/h, etc.

(3) Extrusion (defined in accordance with ASTMC1183)

According to ASTM C1183 standard requirements, under standard conditions, using Semco pipes and specific nozzles (diameter 3.2mm), under specific pressure conditions, the extrusion weight per unit time is called extrudability.

(4) Instant sealing pressure

It means that the silicone rubber plane sealant is glued on the flange plate with a certain diameter, and then closed immediately, the adhesive layer is controlled to have a reasonable thickness, and then the air pressure is applied at a certain rate, and the maximum pressure it accepts is the instant sealing pressure.

(5) Curing characteristics in oil

It means that the silicone rubber plane sealant is placed in a fixed mold, and then the mold is put into the oil, and the thickness of the silicone rubber plane sealant cured from the outside to the inside in a certain period of time is recorded to characterize the oil possessed by the silicone rubber plane sealant. Medium curing properties.

(6) Shear strength adherence rate during drying time

It means that the shear test piece that has been glued is placed for a certain period of time under specific high temperature and high humidity conditions, and then stopped to be closed and bonded, placed under the standard conditions for 168h to stop curing, and its shear strength is tested, and it is consistent with the standard. Under the condition of direct bonding and curing for 168h, the shear strength of the test was compared, and the strength retention rate was calculated.

(7) Thermal stability when uncured

It means that the uncured silicone rubber flat sealant is placed in a high temperature environment for a certain period of time, and then it can still be cured under standard conditions, indicating that the silicone rubber flat sealant is stable under this temperature condition. If the thermal stability temperature of the sealant is greater than or equal to 100°C, it means that the uncured sealant can continue to be cured after being heated at 100°C.

According to the phenyl content (phenyl: silicon atom) in silicone rubber, it can be divided into low phenyl, medium phenyl and high phenyl silicone rubber. When the rubber crystallizes or is close to the glass transition point, or when the two conditions overlap, the rubber becomes stiff. Introducing an appropriate amount of bulky groups to destroy the regularity of the polymer chain can reduce the crystallization temperature of the polymer. At the same time, because the introduction of bulky groups changes the intermolecular force of the polymer, it can also change the temperature. 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℃, which is the best rubber with low temperature performance. Low phenyl silicone rubber has the advantages of vinyl silicone rubber, and the cost is not very high, so there is a trend to replace vinyl silicone rubber. When the phenyl content is greatly increased, the rigidity of the molecular chain will increase, resulting in the reduction of cold resistance and elasticity, but the ablation resistance and radiation resistance will be improved, and the phenyl content will reach C6H5/Si=20~34 % is medium phenyl silicone rubber has the characteristics of ablation resistance, high phenyl silicone rubber (C6H5/Si=35~50%) has excellent radiation resistance.