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 vitrification transition point, or the two overlap, the rubber becomes rigid.The introduction of an appropriate amount of large-volume groups destroys the regularity of the polymer chain, thus reducing the crystallization temperature of the polymer. Meanwhile, the introduction of large-volume groups changes the intermolecular forces of the polymer, so the glass transition temperature can also be changed.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 vulcanized rubber is -120℃, and it is a good 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 content of phenyl is greatly increased, the rigidity of molecular chain will increase, resulting in the reduction of cold resistance and elasticity, but the ablative and radiation resistance will be improved, the phenyl content of C6H5/Si=20~34% medium phenyl silicone rubber has the characteristics of ablative resistance. High phenyl silicone rubber (C6H5/Si=35~50%) has excellent radiation resistance.

    The performance related to the assembly process of the initiator is called the process performance index.

    (1) Dry time refers to the time when a single component RTV silicone rubber is exposed to atmospheric environment in the curing process, touch the surface with fingers and lose viscosity.Ordinary refers to the standard conditions, silicone rubber plane sealant extrusion drying, appearance of the time distance.

    (2) curing depth refers to the curing depth of the silicone rubber plane sealant in a fixed mold under standard conditions. Within a certain time after sizing, the thickness of the rubber layer solidified by the silicone rubber plane sealant from outside to inside, such as: 2 ~ 3mm/24h, 0.6mm/h, etc.

    (3) Extrudability (defined according to ASTM C1183 specification) According to ASTM C1183 specification requirements, under specification conditions, using Semco pipe and specific nozzle (diameter 3.2mm), under specified pressure conditions, extrusion weight per unit time is called extrudability.

    (4) The immediate sealing pressure refers to the silicone rubber plane sealant with a certain diameter in the flange plate plane, and then immediately closed, control the rubber layer with a reasonable thickness, and then in accordance with a certain rate of pressure, the accepted Z pressure is the immediate sealing pressure.

    (5) curing characteristics in oil refers to the silicone rubber plane sealant in a fixed mold, and then put the mold into the oil, record the silicone rubber plane sealant in a certain period of time by the thickness of outward curing to characterize the silicone rubber plane sealant in oil curing characteristics.

    (6) air buy time rate of shear strength insisted Is used to glue the shear specimens under the specific conditions of high temperature, high humidity place after a certain amount of time, then stop fold glue, the specification is placed under the condition of 168 h stop curing and test its shear strength, and with the specification under the condition of direct bonding shear strength of cured 168 h test stop comparison, calculation strength rate.

    (7) The thermal stability of the uncured silicone rubber plane sealant refers to that the uncured silicone rubber plane sealant is put into a high temperature environment for a certain time, and then it can still be cured under standard conditions. It is clarified that the silicone rubber plane sealant is stable under the temperature condition.If the temperature of thermal stability of sealant is greater than or equal to 100℃, it means that the uncured sealant can still be cured after heating at 100℃.