Preparation And Performance Of High Strength Room Temperature Vulcanized Silicone Rubber Based On MQ Silicone Resin

Room temperature vulcanization(RTV)silicone rubber is a siloxane polymer with comprehensive properties such as room temperature vulcanization,good thermal stability,high weather resistance and cold resistance,water repellency and electrical insulation.It is widely used in electronic appliances,building sealants,Aerospace and medical and health fields.However,RTV silicone rubber has a low cohesive energy density and weak intermolecular interaction forces,resulting in poor mechanical properties.Therefore,how to effectively modify it is a scientific problem in this field.Inorganic particles such as silica,montmorillonite,nano-calcium carbonate,etc,are widely used at low prices and are traditional inorganic reinforcing materials for reinforcing silicone rubber.When such materials are used to reinforce silicone rubber,although they can effectively improve the silicone rubber Mechanical properties,but it will cause the system viscosity to increase sharply and it is difficult to process,and too much filler will seriously affect the transparency.The MQ silicone resin is composed of a monofunctional M unit and a tetrafunctional Q unit.It is a hydrophobic powder material with a nano / micro size structure that has both organic and inorganic characteristics.It is excellent in compatibility with liquid silicone rubber.Sex,easy dispersibility,reinforcement and transparency.The traditional preparation methods of MQ silicone resin are sodium silicate method and ethyl orthosilicate method.The sodium silicate method is simple in process and low in raw material cost,but the yield of MQ silicone resin is low,easy to gel,and the molar mass distribution is wide;The molar mass distribution of MQ silicone resin prepared by ethyl silicate method is moderate and not easy to gel,but the process is cumbersome and the cost is relatively high.In addition,organic solvents are used in the preparation process of both methods to coordinate the reaction and cause pollution to the environment.In view of the above shortage of scientific problems,this paper uses a new water capture method to prepare MQ silicone resin with uniform particle size distribution,and uses MQ silicone resin as a reinforcing agent to build different series of room temperature vulcanized silicone rubber systems.Analytical testing means conduct a comprehensive evaluation of its macro / micro performance,the specific contents are as follows:In the first part,MQ silicone resin was synthesized by hydrolytic condensation reaction using tetramethoxysilane as inorganic precursor,hexamethyldisiloxane as blocking agent,acetic acid as active substance,concentrated sulfuric acid as catalyst.The effects of different M / Q value,acetic acid dosage,reaction time,reaction temperature and other factors on the performance of MQ silicone resin were studied.Using Fourier infrared spectrometer? nuclear magnetic and TG to characterize the structure and performance of the reaction product,thermal weight loss and other instruments.The best process for preparing MQ silicone resin show that when the M / Q value is 0.8,OHAc / OMe = 1.25,the reaction time is 4 hours,and the reaction temperature is 58 ° C,the prepared MQ silicone resin has good performance,high yield,and excellent thermal stability.In the second part,MQ silicone resins with different M / Q values were selected to reinforce the condensation type room temperature vulcanized silicone rubber.By changing the addition amount of MQ silicone resin,the morphological characteristics,thermal stability,transparency,and mechanical properties are studied.And hardness,determine the optimal M /Q value and addition amount.The results show that when the M / Q value is 0.8 and the addition amount is 30%(relative to the quality of the base rubber),the modified silicone rubber is prepared.Excellent performance,stable thermal performance,excellent mechanical properties,fast curing.In the third part,making the M / Q value to 0.8,change the ratio of MQ silicone resin to modified mica powder(marked as MQ / MP),and study the surface drying time,mechanical properties,and dielectric properties of condensed RTV silicone rubber law of influence.The results show that as the MQ / MP value increases,the surface drying time gradually increases and the hardness gradually decreases.Among them,when MQ / MP is 3: 2,MQ silicone resin and modified mica powder are uniformly dispersed in the silicone rubber.The prepared modified silicone rubber has a dry time of 41 minutes,a tensile strength of 1.21 Mpa,and an elongation at break is 672.56%,maximum thermal decomposition temperature is 578?,the relative dielectric constant is 0.0817,and the comprehensive performance is the best.