Preparation And Properties Of High Temperature Resistant Carborane Phenolic Adhesives

Since the phenolic resin has excellent adhesion properties and heat resistance, so it is widely used in preparing high temperature adhesives. However, phenolic resins are conventionally used because of its using temperature can not exceed 250?, which limits its application in aviation and aerospace bonding aspect to a large extent. So in order to make one type of high-temperature resistant adhesive modified phenolic is a significant research direction. Modified phenolic adhesive mainly includes the use of organic-modified phenolic resin as a matrix resin and using rubber as the toughening modifier. And boron powder, silicon powder, boron carbide and other refractory inorganic fillers are used to enhance thermal stability of phenolic resin. Thus the adhesives prepared have good adhesion and high-temperature resistant properties.In this paper boron phenolic resin and silicone phenolic resin are used as the matrix resin of high-temperature resistant adhesives, solid carboxylated nitrile rubber compound are used as a toughening modifier for boron-modified phenolic adhesive, and the modified mechanism is also analyzed. The effects of nitrile amount on boron phenolic adhesive bond strength at room temperature are studied. The results showed that a solid carboxylated nitrile rubber can crosslink with boron phenolic resin, improving the toughness of the adhesive in 100 parts of the adhesive system and the best amount of solid carboxylated nitrile rubber is 12 parts, while the adhesive bonding strength reaches its maximum temperature.Boron powder, silicon powder and boron carbide (B4C) are used to enhance high temperature resistance of boron phenolic adhesive and silicon phenolic adhesive. The effect of the inorganic filler particle size of boron phenolic adhesive are studied at high temperatures and effect of the proportion of total amount of the inorganic filler and the total amount of organic matter on the adhesive heat resistance properties are also studied. By adding of 1,2-bis(4-hydroxyphenyl)-carborane to heat resistant properties of silicon and boron phenolic adhesive, the smaller the inorganic filler particle size, the boron phenolic adhesive exhibits better resistance to high temperature, the best ratio of the inorganic filler and the organic matter in boron phenolic adhesive is 0.9:1.0 and the best ratio of the inorganic filler and the organic matter in silicone phenolic adhesive is 1.6:1.0 so that by adding of 1,2-bis(4-hydroxyphenyl)-carborane can improve high temperature resistance of boron phenolic adhesive and silicon phenolic adhesive obviously.When boron phenolic adhesives were only modified by one filler of boron powder, silicon powder and 1,2-bis(4-hydroxyphenyl)-carborane, respectively, FT-IR, SEM, EDS, TG-FTIR were used to analyze the high temperature resistant mechanism. The results showed that boron phenolic resin will decompose when the temperature exceed 500?, so CO2, CO, H2O are released. Boron powder, silicon powder and other inorganic fillers will react with CO2, CO, H2O and other volatile, as a result B2O3, SiO2 and other oxides are generated and at the same time restore the element C, so boron phenolic adhesive have a good high temperature resistant properties due to improved structural integrity at high temperature.