(1) Surface drying time
It refers to the time during which a single component room temperature vulcanized silicone rubber loses its adhesion by touching the surface with your fingers during the curing process in an atmospheric environment. Ordinary refers to the time distance during which silicone rubber flat sealant is extruded and air dried under standard conditions, and the surface is not touched.

(2) Curing depth
It refers to the thickness of the adhesive layer of silicone rubber flat sealant that solidifies from the outside to the inside within a certain period of time after applying silicone rubber flat sealant in a fixed mold under standard conditions, such as 2-3mm/24h, 0.6mm/h, etc.

(3) Extrudability (defined according to the specifications of ASTMC1183)
Under standard conditions, the extrusion weight per unit time under specific pressure conditions using Semco pipes and specific nozzles (diameter 3.2mm) is called extrudability.

(4) Immediate sealing pressure
It refers to applying silicone rubber flat sealant with a certain diameter to the flange plate surface, immediately closing it, controlling the adhesive layer to have a reasonable thickness, and then applying air pressure at a certain rate. The maximum pressure it receives is the instant sealing pressure.

(5) Curing characteristics in oil
It refers to applying silicone rubber flat sealant into a fixed mold, and then placing the mold into oil, recording the thickness of silicone rubber flat sealant that solidifies from the outside to the inside within a certain period of time to characterize the oil curing characteristics of silicone rubber flat sealant.

(6) Persistence rate of shear strength during drying time
It refers to placing the previously glued shear test piece under specific high temperature and humidity conditions for a certain period of time, then stopping the closure and bonding. It is then placed under standard conditions for 168 hours to stop curing, and its shear strength is tested. It is then compared with the shear strength tested under standard conditions for direct bonding and curing for 168 hours, and the strength persistence rate is calculated.

(7) Thermal stability when not cured
It refers to placing uncured silicone rubber flat sealant in a high-temperature environment for a certain period of time, and then being able to cure under standard conditions, indicating that silicone rubber flat sealant is stable under this temperature condition. If the thermal stability temperature of the sealant is ≥ 100 ℃, it means that the uncured sealant can still continue to cure after heating at 100 ℃.

According to the different phenyl content (phenyl: silicon atom) in silicone rubber, it can be divided into low phenyl, medium phenyl, and high phenyl silicone rubber. When rubber crystallizes or approaches the glass transition point, or when these two situations overlap, it can lead to a stiff state of the rubber. Introducing an appropriate amount of large volume groups can disrupt the regularity of the polymer chain, which can reduce the crystallization temperature of the polymer. At the same time, the introduction of large volume groups can change the intermolecular force of the polymer, thus also changing the glass transition temperature. Low phenyl silicone rubber (C6H5/Si=6-11%) has excellent low-temperature resistance due to the above reasons, and is independent of the type of phenyl monomer used. The brittleness temperature of vulcanized rubber is -120 ℃, making it the best low-temperature performance rubber today. 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, leading to a decrease in cold resistance and elasticity. However, the resistance to ablation and radiation will be improved. The phenyl content of C6H5/Si=20-34% is the characteristic of medium phenyl silicone rubber with ablation resistance, while high phenyl silicone rubber (C6H5/Si=35-50%) has excellent radiation resistance.