Preparation And Properties Of Dopamine Modified Polysiloxanes

Polysiloxane with flexible Si-O-Si as the main chain has many excellent properties,such as high and low-temperature resistance,irradiation resistance,aging resistance,corrosion resistance,and physiological inertness.It has been widely used since the 20th century in daily use at home,in industrial production,aerospace,and military industries.Silicone rubber has the broadest range of applications in various polysiloxane materials.However,its common filler silica has many hydroxyl groups on the surface,which hinders the compatibility of silica with silicone rubber and causes dispersion defects of silica,and seriously affects the reinforcement effect.In addition,silica is a non-renewable material;its production and application process is accompanied by massive energy consumption and dust pollution.Therefore,it is of great practical significance to explore how to enhance the compatibility of the silica-silicone rubber interface,improve the reinforcement effect and further explore new green fillers to expand the application scope of silicone rubber.Dopamine and other compounds with catechol structure can form covalent bonds or noncovalent complexes with many other functional groups,enhancing the adhesion to various material surfaces.Therefore,introducing catechol into polysiloxane systems may improve silica-silicone rubber interfacial interaction and create a self-reinforcing effect.This paper first synthesized dopamine-functionalized alkoxysilanes(DATMS)from dopamine and isocyanate siloxane.Based on this,dopamine-modified silicone oil(DASO)and dopamine-modified silicone resin(DASR)were prepared using a hydrolytic condensation reaction of siloxane.Thermogravimetric analysis showed that the catechol structure increased the thermal decomposition temperature of the silicone resins.Subsequently,a series of high-temperature vulcanized dopamine-modified silicone rubbers(R-DA)were prepared by adding DASO to dimethyl silicone rubber with silica reinforcement and using a peroxide crosslinking system.The relationship between the structure and properties of different formulations of silicone rubbers was subsequently investigated.SEM images of R-DA showed that the agglomeration of silica was reduced after the addition of DASO,and the dynamic mechanical loss behavior indicated that the damping factor of R-DA in the high elastic state increased with the addition of DASO.This demonstrates that the addition of DASO enhanced the interaction between the rubber polysiloxane molecular chains and the filler.Thermogravimetric analysis showed that the dopamine modification could increase the thermal degradation temperature of the Si-O-Si main chain by 60℃,which had a good effect on the heat resistance enhancement of silicone rubber.Also,the tear strength of R-DA was enhanced by introducing concentrated crosslinking points generated by catechol groups and robust filler interfaces.The tear strength of the improved formulation of silicone rubber could reach 52.81 kN/m.Cellulose,which is derived from natural plants and has green degradable,and eco-friendly characteristics,has shown good reinforcing ability when compounded with polymeric materials such as nylon and natural rubber.However,the presence of many hydroxyl groups on the surface of cellulose leads to its poor compatibility and non-uniform dispersion with silicone rubber.Therefore,silicone rubber formulation systems with pure cellulose as reinforcing filler are rarely reported.Inspired by the interaction mechanism between catechol structure and silica hydroxyl groups,considering the abundant hydroxyl groups on the surface of cellulose,the use of dopamine as a bulking agent between silicone rubber and cellulose may solve the interfacial compatibility problem and may develop cellulose as a new generation of green filler for silicone rubber.A series of cellulose-filled dopamine-modified silicone rubber materials were prepared by introducing two cellulose blends,ethyl cellulose(EC)and cyanoethyl cellulose(CNEC),into the silicone rubber system.The reinforcing effect of cellulose and the capacitating effect of DASO on the fillers were investigated.The results showed that cellulose was chemically bonded to the silicone rubber backbone by the bridging action of DASO,and the more the amount of DASO,the tighter the bonding of cellulose to the rubber.At the same time,cellulose can improve the tensile strength of silicone rubber,inhibit the crystallization behavior of silicone rubber molecular chains,and reduce the crystallization melt transition temperature of rubber.These phenomena indicate that cellulose has the potential to replace the traditional filler of silicone rubber.