The influence of different content of dimethyl silicone oil on the performance of silicone building sealant has been studied at home and abroad.The results show that appropriate addition of simethicone can increase the elongation of the sealant product, improve its elasticity, and increase its resistance to displacement; however, when the content of simethicone exceeds 20%, the tensile strength of the sealant will gradually appearProblems such as decline, excessive sag and poor adhesion to the substrate.Therefore, it is necessary to reasonably design the amount of simethicone added in the actual use process to ensure the comprehensive performance of the sealant.
Silicone sealant is made of polydimethylsiloxane as the main raw material, adding appropriate amount of fillers, plasticizers, crosslinking agents, coupling agents, catalysts and other additives. It is produced by reacting with water in the air at room temperature.The reaction forms a cross-linked network structure, which is then cured to form elastic silicone rubber.
Polydimethylsiloxane, commonly known as dimethyl silicone oil, is a colorless transparent liquid with good heat and cold resistance. It can be used for a long time at -50~200 ℃, maintaining stable chemical properties and excellent physical properties;The main polymer of the silicone sealant has the same molecular structure (silicone as the main chain), and has good compatibility with the silicone sealant system. It is often added to room temperature vulcanization (RTV) silicone rubber as a diluent or plasticizerin.Therefore, this paper systematically studied the plasticizing effect of different content of dimethyl silicone oil in dealcoholized and ketoxime silicone building sealants, focusing on the surface drying time, sag, mechanical properties and viscosity of the sealant.The junction performance varies with the content of dimethyl silicone oil.
1) As the content of dimethyl silicone oil increases, the surface dryness of the sealant becomes slower; the greater the content of dimethyl silicone oil, the longer the surface dry time of the sealant; relative to the deoxime type sealant, the surface dry time of the sealant becomesThe influence of the surface drying time of the dealcoholized sealant is more significant.
2) As the content of simethicone increases, the resistance to deformation and flow of the sealant becomes worse, which is manifested as an increase in sag; the greater the content of simethicone, the higher the sag of the sealant;There is no significant difference in the sag of dealcoholized sealant and oxime sealant.
3) As the content of simethicone increases, the tensile strength of the sealant shows a downward trend; when the addition of simethicone is 20% to 30%, the tensile strength of the sealant drops significantly.There is no significant difference in the effect of dimethyl silicone oil on the tensile strength of dealcoholized sealant and oxime sealant.
4) As the content of simethicone increases, the elongation of the sealant shows an upward trend; when the content of simethicone exceeds 20%, the increase in the elongation of the sealant tends to be flat.Compared with the deoxime sealant, the simethicone has a more obvious effect on improving the elongation of the dealcoholized sealant.
5) When the simethicone content is less than 10%, the adhesion between the sealant and the substrate is good; when the simethicone content exceeds 10%, the adhesion between the sealant and the substrate gradually becomes problematic;When the amount of simethicone added exceeds 50%, the sealant and the substrate may not stick at all.Considering comprehensively, it is recommended that in the actual sealant formulation design, the content of simethicone should be less than 20%, which can ensure the mechanical properties of the sealant.Under the premise of bonding performance, it can effectively improve the elasticity of the product.