Preparation And Properties Of Carborane Modified Heat-resistant Epoxy Adhesive

Epoxy resin is currently the most widely used type of thermosetting resin.Due to its excellent mechanical properties and process properties,it has extremely high application value in the electronics industry,aerospace,construction,automotive and other fields.However,with the continuous progress and development of aerospace and other fields,higher requirements have been placed on its temperature resistance.Therefore,it is necessary to improve the high temperature resistance of epoxy adhesives.Nowadays,the heat resistance of epoxy resin can be improved by increasing the crosslinking density of epoxy matrix,using curing agent with rigid structure or multi-functional degree and adding heat-resistant filler.Although these methods are very effective,there are still shortcomings.Phenolic epoxy resin is superior to bisphenol A epoxy in high temperature resistance due to its high functionality.Carborane has been widely used in improving the heat resistance of polymers due to its energy absorption effect and large volume shielding effect.Cyclodisilazane has excellent thermal stability and is often used as an additive to improve the thermal stability of polymers.And the addition of a heat-resistant filler can also improve the thermal stability of the cured epoxy resin.Therefore,this paper mainly conducts the basic research work on the heat resistance of carborane-modified epoxy resin adhesives from the perspective of improving the heat resistance of epoxy resin adhesives.A highly functional phenolic epoxy resin is used as a matrix and a carborane-containing curing agent is used to cure it to achieve a molecular-level organic/inorganic hybrid.Then add heat-resistant fillers and liquid rubber to make up for its shortcomings in heat resistance and toughness.The polymer’s curing behavior,heat resistance and adhesive properties of the cured product were systematically studied.The main research contents and results are as follows:1.Carborane containing epoxy resin adhesive was obtained by high temperature curing,and the curing reaction was confirmed by infrared characterization.The polymer has good storage stability.Its solidified products have excellent thermal stability and thermal oxidation stability.5%weight loss temperature is higher than 300℃in nitrogen or air.The results show that the content of carborane and the amount of filler have a great influence on the adhesive properties.After optimizing the curing process,the polymer with 30%carborane unit has the best comprehensive properties.The shear strength of bonding stainless steel is 12.3 MPa at room temperature and 1.56 MPa at 500℃.And the bonding strength is improved at low temperature.It shows that we have a good adhesive with high temperature resistance and low temperature resistance.2.The room temperature curable carborane containing epoxy resin adhesive was obtained by adding phenolic amine room temperature curing agent,and the occurrence of curing reaction was confirmed by infrared characterization.The results show that the content of carborane and the amount of filler have a great influence on the adhesive properties.The polymer has good storage stability.The cured product has excellent thermal stability and thermal oxidation stability.After optimizing the curing process,the polymer with 50%carborane unit has the best comprehensive properties.The shear strength of bonding stainless steel is 15.14 MPa at room temperature and 0.9 MPa at 600℃.After adding heat-resistant fillers,the shear strength can reach up to 1.1 MPa,exhibiting superior high-temperature resistance.3.The thermal degradation mechanism of carborane containing polymers was studied.When the carborane containing epoxy resin is heated,it is mainly the depolymerization of the macromolecular network of the epoxy resin first,resulting in water,carbon monoxide,etc.With the increase of temperature,the structure of carborane was destroyed,and boron oxide,methane and alkanols were newly produced.When carborane is heated,it will react with oxygen in air or oxygen in epoxy resin system to form boron oxide.And B₂O₃ covered at the surface of epoxy resin polymer firstly,thus delaying the degradation of epoxy resin by air.4.The effect of octaphenylcyclodisilazane on the thermal stability and adhesive strength of epoxy resin was investigated.The reaction between epoxy resin and cyclodisilazane was proved by IR and NMR.It can be seen from the thermogravimetric data that the addition of octaphenylcyclodisilazane can delay the degradation of the adhesive system.5.The toughening effect of epoxy butoxyl on epoxy resin was investigated.The epoxy resin adhesive was prepared with phenolic amine as curing agent and epoxy butoxyl as toughening agent.The morphology of epoxy resin before and after toughening was observed by SEM.It was found that the original brittle fracture of epoxy resin changed into ductile fracture after adding epoxy butoxyl.The glass transition temperature of phenolic epoxy resin decreased slightly with the addition of epoxy butoxyl.The mechanical properties of the toughened epoxy resin were characterized,and it was confirmed that the impact toughness of the epoxy resin was improved by adding epoxy butoxyl.