Preparation And Properties Of Functional Silicone Materials

Silicone materials possess many excellent properties,such as physiological inertia,high-low temperature,weather resistance and hydrophobicity,therefore,they are widely used in petrochemical industry,construction,medical devices,aerospace,electronics and food processing.SiO₂ aerogels are a type of porous material with many excellent properties such as low density,high specific surface area,high porosity and low thermal conductivity.It has been widely used in wastewater treatment,heat preservation,heat insulation,sound absorption and catalyst carrier and other fields.Therefore,the functionalization of silica aerogel has become a hot spot recently.Silicone rubber is a traditional silicone polymer material.Its covalent bond crosslinking network is permanent,irreversible and does not possess self-healing properties.Compared with covalent bond,hydrogen bond is a dynamic and thermally reversible non-covalent bond which could establish physical crosslinking network to endow silicone rubber with self-healing properties.Therefore,in this paper,the thiophene group was introduced into the aerogel network by chemical modification to prepare thiophene modified silica aerogel composites with excellent adsorptive properties as well as the adsorption properties were mainly studied.A type of hydrogen bonds cross-linked silicone rubber was prepared based on the reaction of non-isocyanate which the high thermal self-healing property was given to silicone rubbers.The details were as follows:1.The functional reagent 2,5-divinyltrimethoxysilane thiophene（DVTHP）was synthesized from vinyl trimethoxysilane and 2,5-dibromothiophene through the Heck reaction and characterized by FTIR and ¹H NMR.Thiophene modified SiO₂ aerogel was prepared from tetraethyl（TEOS）and DVTHP by a sol-gel reaction and ambient pressure drying process.FTIR and solid ¹H NMR indicated that the thiophene units had been successfully introduced into the silica aerogel network;SEM showed a co-continuous porous structure of material;BET specific surface area measurements showed a mesoporous structure of thiophene modified silica aerogel that had a specific surface area of 834 m²/g,an average pore size of 17.84 nm and a large pore volume of 3.72 cm³/g;This thiophene-modified silica aerogel had superhydrophobicity with a water contact angle（CA）exceeding 174°and a sliding angle of less than 3°.Adsorption experiments indicated that thiophene modified SiO₂ aerogel had better selectivity for nonpolar solvents compared with polar solvents,and their adsorption capacity is significantly improved compared with unmodified silica aerogels,the adsorption capacities for n-hexane and gutter oil are calculated as 17 g/g and 16 g/g,respectively.Moreover,the samples exhibited good recyclability for organic solvents even after recycling 10 times in adsorption/desorption tests and the adsorption capacities were nearly unchanged from the maximum uptake capacities,which indicating that thiophene modified silica aerogel had good adsorption recycling capability.The results also indicated that these materials could be flexibly utilized as adsorbent materials to selectively adsorb organic solvents for wastewater treatment.2.α,ω-aminopropyl terminated polydimethylsiloxane（A-PDMS）,ethylene carbonate（EC）and catalyst lithium chloride anhydrous were uniformly mixed at room temperature,then the mixtue were cured at 120℃.The hydrogen bonds cross-linked silicone rubber（HBSR）with thermal self-healing properties was prepared.The chemical structure and multiple hydrogen bonds between the generated carbonyl and imino groups as well as the hydroxyl groups were proved by the FTIR and variable temperature FTIR analysis.Mechanical properties tests indicated that the tensile strength of HBSR could reach to 0.52MPa that was equal or even better than the conventional room temperature vulcanized silicone rubber without fillers.Swelling tests showed that the crosslinking density of HBSR increased with the increase of ammonia value of A-PDMS.TGA proved that HBSR had good thermal stability,and its thermal decomposition occured at about 300°C,the maximum decomposition temperature is about 370°C and completely decomposed at about450°C.DMA test results indicated that the storage modulus（E’）of HBSR first increased and then decreased with the increase of ammonia value of A-PDMS.Further,the higher ammonia value meant more crosslinking sites that was adverse to the stress dispersion and easily chain rupture;Moreover,the multiple hydrogen bonds led to a thermal induced self-healing efficiency of 88.1%at 80°C,the self-healing efficiency after the fifth time recovery were still reached 79.4%,which showed that HBSR had good cyclic self-healing ability.