Preparation And Study Of High-temperature-resistance Silicone Marking Paints

Braking systems is one of the most important factors related to the safe operation of the railway vehicles. Thus, before the vehicle operates, it’s important to check the security of the braking system. The standard is to watch the site of the galvanized fasteners coated with marking paints moving or not. But in the process of rail vehicle braking, the instantaneous temperature could reach500-600℃, which puts forward higher demand to the marking paints. The traditional high-temperature-resistance paints are hard to meet various requirement of the performance. Therefore, the existing high-temperature-resistant silicone paints can’t meet the requirements of railway vehicle to use in practice.In this work,the methyl phenyl silicone resin was synthesized by hydrolysis condensation method using MTMS and DDS as raw materials. The effects of raw material y(R/Si), solvent type, synthetic process, solid content on viscosity, the added amount of the curing agent, storage stability, chemical resistance, heat stability and basic physics performance of high solid content silicone resin solution were investigated. The results show the best preparation parameter of the methyl phenyl silicone resins is followed:raw material y(R/Si)=1.35, glycol ether as solvent, and the solid content is chosen to be75%.Through the analysis of TG-DSC, silicone resin mass loss was about2.5%at400℃, and its mass loss was about7.5%at500℃. TG-DSC analysis shows that as-synthesized silicone resin has excellent stability.A kind of high-temperature-resistance silicone paints was prepared by using as-synthesized methyl phenyl silicone resin as binder. The effects of the fills(nano-SiO2, talcum powder, aluminum power, pearlescent powder),pigment(iron oxide, iron blue, Iron green, ultramarine, melanin, titanium dioxide,) and curing agents (butyl titanate, KH550) on the performance of high-temperature-resistance silicone paints were studied, such as gelatin time of paints, adhesion, heat resistant performance, cold and hot alternation performance etc. Here, the red paints were studied as typical conduct.Though the comparison test, the best formula of the high-temperature resistance paints is obtained. Namely, the amounts of the methyl phenyl silicone resin,nano-SiO2, iron oxide, aluminum power, talcum powder, pearlescent powder, butyl titanate, leveling agent S43, defoamer El are40-47%,0-2%,7-9%,20-28%,5-15%,10-15%,2-2.5%,0.6%,0.1%, respectively. The paints doesn’t cracked after10times cold and hot alternation in conditions of500℃-cold water, the pencil hardness reaches3H, and the adhesion reaches1level after curing.