Synthesis Of Deep Eutectic Solvent And Its Application In Curing Of Epoxy Resin

As a thermosetting polymer with high mechanical strength and mechanical modulus,epoxy resin has been widely used in civil and traditional and new industrial engineering fields by virtue of a variety of excellent comprehensive properties.However,the epoxy resin itself has high viscosity and poor operability.At the same time,epoxy resin cured products are accompanied by shortcomings such as brittleness,poor crack resistance and low fracture toughness.Solving these problems has also become a research focus.DES are sustainable green solvents that are complexed by hydrogen bond acceptors and hydrogen bond donors.Researchers are synthesizing more and more preparable raw materials into DES,and they are constantly developing the application range of DES,but there are not many reports on introducing DES into epoxy resin curing systems.Therefore,this article synthesizes a series of new eutectic solvents firstly,and then selects one kind of the DES to introduce into the epoxy resin curing system to prepare DES/epoxy resin composites,and finally builds on this basis in the previous section,melamine was introduced to prepare a DES/melamine/epoxy resin composite material.The specific research content and results of this article are divided into the following aspects:Firstly,choline chloride and tetrabutylammonium bromide are used as hydrogen bond acceptors,and ethanolamine,diethanolamine,and triethanolamine are used as hydrogen bond donors to synthesize DES.Explore the effects of the ratio of each component and the reaction temperature on the freezing point,density,refractive index,viscosity,conductivity,surface tension and other properties of the DES,and Fourier transform infrared spectroscopy is used to characterize the structure of the eutectic solvent.The results show that the freezing point of the synthesized DES is significantly lower than that of the raw materials,and the best molar ratios of choline chloride to ethanolamine,diethanolamine,and triethanolamine are 1:7,1:7,and 1:6,respectively.The corresponding freezing points are 3.3 ℃,-9.8 ℃,-10.4 ℃;the best molar ratios of tetrabutylammonium bromide to ethanolamine,diethanolamine,and triethanolamine are 1:6,1:7,1:6,respectively.The corresponding freezing points are-18.1 ℃,-14.7 ℃,and-17.6 ℃,respectively;The density,viscosity,and refractive index of the DES all decrease with the increase of the molar ratio of raw materials and temperature;Surface tension increases with the increase of the molar ratio of raw materials,and decreases with the increase of temperature;The conductivity increases with increasing raw material molar ratio and temperature.Secondly,the choline chloride-ethanolamine-base DES was introduced into the epoxy resin curing system,and the effect of it as a diluent on the epoxy resin curing system was explored,including the amount of DES and curing temperature on the curing material,the effect of viscosity,curing time,mechanical strength and water absorption properties,and observe its fracture morphology.The results show that the curing effect of the choline chloride-ethanolamine-base DES itself as a curing agent is significantly weakened,and the curing time is about 110 h.Compared with the traditional curing agent,the curing effect is basically negligible.As a diluent,it can reduce the epoxy resin system when the eutectic solvent content is 32%,the viscosity of the system is 2028 c P.Choline chloride-ethanolamine-base DES as a diluent can extend the curing time of epoxy resin system.When the content is 32%,the curing temperature can be extended by 70 minutes when the curing temperature is 30 ℃.The tensile strength,flexural strength,and compressive strength of cured epoxy resin gradually decrease with the increase of the amount of eutectic solvent,the elongation at break gradually increases,the tensile section shows ductile fracture,and the water absorption rate of the cured material gradually decreases.The water absorption rate within 72 h is from 8.25% reduced to 1.95%,showing good water resistance.Finally,after adding melamine to the curing system of DES and epoxy resin,the curing time of the system is prolonged.The mechanical strength of the curing system increases first and then decreases as the amount of melamine increases.The curing system the initial thermal decomposition temperature of 30% is increased by 35 ℃,the thermal weight loss rate is reduced,and the limiting oxygen index reaches 28.6%,showing a good flame retardant effect.The water absorption of the cured material increases with the addition of melamine,and the equilibrium water absorption rate is up to 9.39%,which is close to 3 times that of the cured material without melamine.Scanning electron microscopy shows that when a small amount of melamine is incorporated into the curing system,the compatibility is better.When the amount of melamine is large,its dispersion effect in the curing system becomes worse,and even agglomeration phenomenon begins to occur.