| Owing to its excellent heat resistance, silicone resins have been widely utilized as heat-resistant materials such as coatings, adhesives and matrices for composites. However, silicone resins containing solvent have to be cured at elevated temperature (250-300℃), which hinders their application in adhesives and matrices for composites. Beijing University of Chemical Technology synthesized a novel liquid polymethoxylsilicone (MOS) without solvent, which could be cured at room temperature. But, the pure cured resin had low physical properties and poor heat resistance, which required the resin to be modified on strength and toughness. On basis of the modification, heat resistant MOS resin sealant could be developed.Nano-CaCO3/MOS composite and metal powder/MOS composite have been prepared respectively by adding nano-CaCO3and metal powder to MOS resin. Moisture curing behavior has been studied by FTIR. Furthermore, physical properties of MOS resin and its composites have been tested in accordance with national standard GB. Heat property has been studied by TG and DMA. Finally, shrinkage ratio and dielectric constant have been tested.(1) MOS resin and its composites could be cured at room temperature and catalyst system, atmosphere and filler concentration affected the curing rate and depth. Multi-catalyst of organic tin and organic amine was obviously better than single catalyst. More filler was added, deeper curing depth would be possible by using more catalyst. Curing in nitrogen was better than in air. Shrinkage varied ratio from7%to0.99when CaCO3concentration varied from0to40%.(2) Tests of MOS resin and its composites showed that the maximum impact, tensile and bending strength of MOS resin were0.85kJ/m2,1.06MPa and4.00MPa respectively. The physical properties of nano-CaCO3/MOS composite rised to a certain value and then came down with the increase of nano-CaCO3dosage. The maximum impact, tensile and bending strength,3.72kJ/m2,8.2MPa,17.9MPa have been obtained when nano-CaCO3concentration was30%, volume. SEM analysis showed that the structure of nano-CaCO3/MOS composite after loading was dense and the substrate had obvious distortion, which demonstrated the resin has been reinforced by nano-CaCO3. The impact strength of metal powder/MOS composite rised to a certain value and then came down with the increase of metal powder dosage. The maximum impact strength value2.16kJ/m2, which was twice that of MOS, has been obtained with the mass ratio of metal powder to resin6/1.(3) Heat property studies showed that the heat stability of MOS resin in argon and air differs as different pyrogenation mechanism. TG analysis showed the real mass loss of nano-CaCO3/MOS resin was lower than the total mass loss of pure CaCO3and pure MOS, which revealed that cooperation effect existed between CaCO3and MOS resin. Mass loss of metal powder/MOS composite was of difference when in argon and air atmosphere. Mass loss of metal powder/MOS composite in argon at800℃was only2.66%(15.44%for MOS resin).The composite gained weight when heated in air at800℃owing to the oxidation effect of metal powder.(4) The dielectric constant of nano-CaCO3/MOS resin increased from4.00to4.59when CaCO3concentration varied from0to40%. |
PDF Full Text Request