Study On The Intercalated Nanocomposites Of Ionic Liquid-Treated Rectorite And Epoxy Resin

Ionic liquid-treated rectorites (OREC) were prepared by using 1-hexadecyl-3-methyl- imidazolium bromide ([C₁₆mim]Br) with better thermal stability than the commonly used alkyl ammonium to treat natural rectorite by solution (in water and toluene) and grinding method. For the solution method the cation exchange capacity of rectorite was investigated using elemental analysis in different reaction conditions. And the structure and property of the modified rectorites were characterized by FTIR,XRD,TEM and TG. Then two types of OREC/epoxy intercalated nanocomposites were obtained from the prepared OREC by melting intercalation, with epoxy resin (EP) as matrix, 2-ethyl-4-methylimidazole (2-E-4-MI) and tung oil anhydride (TOA) as curing agents, respectively. The microstructure, mechanical and heat-resistant property of the nanocomposites were characterized by XRD,SEM,TEM,tensile and bending testing,TG-DSC. Besides, the curing kinetic process of the anhydride curing system was investigated by non-isothermal DSC analysis, and the rheological behavior of the clay/epoxy blending system was also studied by HUCK Rotational Rheometer. The main conclusions of the paper were as follows:(1) The optimum process condition for the organic modification was determined as follows: in the water, the stoichiometric ratio of [C₁₆mim]Br/REC 1.5:1, the slurry concentration 5%, reaction temperature 50℃, reaction time 4 h, pH value 9-11; In the toluene, the stoichiometric ratio of [C16mim]Br/REC 1.5:1, the solvent amount 50 mL, reaction temperature 50℃, reaction time 4h, reaction time 2h. The XRD results showed that the interlayer spacing of modified clays from water and toluene were expanded from 2.23 nm to 3.14 nm and 3 nm respectively, the organic clay prepared by grinding method to 3.003 nm. TG analysis showed that the thermal decomposition temperature of the modified clays from water and toluene increased by 121.5℃and 71℃as compared with the cetyltrimethylammonium bromide-modified rectorite (CTAB-REC).(2) The results of XRD and TEM analysis showed that, with addition of the curing agent 2-E-4-MI, the intercalated nanocomposite was obtained; with addition of the curing agent TOA, the exfoliated nanocomposite was obtained when the OREC content was less than 2 wt %. The performance test results indicated that, the intercalated OREC/EP nanocomposite containing 3 wt% OREC had the best mechanical properties as compared with pure epoxy resin, the tensile strength increased by 31.1 %; bending strength increased by 15.25 %. As the OREC content increases to 5 wt %, the thermal decomposed temperature of intercalated nanocomposites increased by 16.6℃. The exfoliated OREC/EP nanocomposite containing 2 wt % OREC had the best mechanical and thermal properties, the tensile strength increased by 60.3 %, bending strength 26.7 %. The thermal decomposition temperature increased by 14℃, glass transition temperature 5.7℃.(3) The calculated results according to Kissinger and Flynn-Wall-Ozawa equation showed that the addition of the OREC could reduce the curing activation energy and frequency factor of the anhydride curing system, indicating the cure reaction could be accelerated by the added OREC. And the curing reaction order was calculated to be 0.92～0.93 according to Crane equation, indicating the anhydride curing reaction is not a simple first-order reaction, and the added OREC didn't change the cure reaction mechanism.(4) Roller semi-empirical model analysis showed that, the flow-activation energy of the blending systems increased as the OREC content increased. The viscosity of the resin with different OREC content showed significant Non-Newtonian behavior at different temperatures. And at the same temperature, the rate of increase in the viscosity of the blending systems increased as the OREC content increased, indicating that the addition of OREC accelerated the cure reaction.