Development Of High Performance Polysulfide Sealant

Polysulfide, which is a kind of perfect elastic sealant, show many advantage such as curing homogeneous, resistance chemical, climate resistance. The mass-production polysulfide at home presents poor tensile bond properties, which couldn't achieve the demand of high speed train. In this paper, polysulfide sealant is modified by blend, and mechanical properties, bond performance, SEM, TG and DMA tests are utilized to display the effect of each component on the properties of the sealant, then to prepare reliability sealant with high properties.The results show that:(1) the oligomer with low cross linking degree (0.5%) present higher elongation at break and lower tensile strength compared to high cross linking degree (2%). Though the curing speed of MnO2 is higher than ZnO, the mechanical property of sealant cured by MnO2 is lower than that cured by ZnO. Curing system, which composited by accelerator diphenyl-guanidine and MnO2, can accelerate the curing speed of the sealant at the initial stage, and the addition of the diphenyl-guanidine should be not more than 1.0phr. Butyl benzyl phthalate is a good plasticizer of polysulfide sealant. (2) Nano-CaCO3 and TiO2 are nice reinforcing filler for polysulfide sealant, then the addition is 80phr, the elongation at break and tensile strength of each is 430%, 2.63MPa and 369%, 2.62MPa. The tensile strength and elongation at break of the sealant, which filled with the composites of nano-CaCO3 and precipitated CaCO3, can be tuned with various additions of the composite filler. (3) The adhesiving can improve the tensile bond behavior of the sealant, and make the sealant achieve to cohesive failure, and resin can enhance the mechanical properties. (4) The effect of the components on the reliability of the sealant are also studied, and the sealant show good chemical tolerance, high degradation temperature as 200℃, and low glass transition temperature as-58℃finally.