Study On Curing Kinetics Of Modified Fly Ash As Filler In Binder

Fly ash is a kind of fine particle from flue gas of coal-fired power plant.Use of modified fly ash in the construction adhesive can not only solve the problem of pollution caused by store of fly ash to the environment but also reduce the cost of building adhesive materials and improve the mechanics performance.In the first part of this article,formation process of fly ash,basic physicochemical properties,common modification methods and the application of inorganic fillers in building adhesives were briefly introduced.In chapter 2,the surface functionalization of fly ash is carried out,including hydroxylation,silanization,hyperbranched reaction and amidation of fly ash.The physicochemical properties of fly ash before and after modification are characterized.Raw,hyperbranched and aminated fly ash were filled in the epoxy construction adhesive system,respectively.DSC analysis and mechanical characterization found that hyperbranched fly ash and amidated fly ash possess both the function of fillers and hardeners.Both of them can significantly increase building adhesive mechanics performance.Influence of modified fly ash on curing kinetics of building adhesive system was also studied.The surface modification of fly ash was carried out with self-made surface modifier and silane coupling agent.The samples were tested by infrared spectroscopy and TGA analysis.Test results showed that the organic functional groups were successfully grafted to the fly ash surface.The modified fly ash was added into epoxy resin adhesive to study the influence of different modifiers on the curing kinetics of composite materials.At the same time,the temperature of curing system was changed and the influence of temperature on curing kinetics was studied.It is found that the addition of modified fly ash has an obvious catalytic effect on the curing reaction of the composite adhesive system.However,when the amount of modified fly ash is morethan 30 parts per 100 parts of epoxy resin,the viscosity of the system increases significantly,resulting in the reaction changing from chemical control to diffusion control at a certain degree,which impedes the further curing reaction of the adhesive system and reduces the curing degree.The decrease of temperature can also significantly reduce the reaction rate series,reducing the autocatalytic effect,and changing the curing reaction from chemical control to diffusion control at a lower reaction degree.