| Polymer nanocomposites have excellent properties not only related to the excellent physical properties of inorganic nanoparticles,but also closely related to their own process rheological properties.For different nanocomposite systems,the rheological properties are also very different.Depth understanding of the structure and rheological properties of nanocomposites,not only can optimize the processing technology,more able to control the performance of polymer nanocomposites.Usually,Small Amplitude Oscillation Shear(SAOS)and Large Amplitude Oscillation Shear(LAOS)were used to study the rheological properties of nanocomposites.The work of this thesis is mainly composed of two parts,and the curing kinetics and curing mechanism of two-component addition silicone rubber and nanocomposite silicone rubber were studied with small amplitude oscillation mode.The gelation process and strain hardening behavior of silica/ionic liquid ionogels were studied by large amplitude oscillation shear mode.The results are as follows:(1)The curing kinetics of two-component addition silicone rubber was studied by isothermal and small amplitude oscillatory rheological method.The results show that the gelation time(tgel)of silicone rubber decreases with the increase of reaction temperature,and tgel has a certain function relationship with the reaction temperature at different reaction temperatures.The apparent activation energy Ea = 87.35 kJ/mol of silicone rubber can be estimated by the relationship between lntgel and reaction temperature(1/T).The reaction series(m+n)of a|G*| and aG",aG' and atroque are calculated by the Kamal-Sourour(K-S)reaction model for a time sweep of 10 rad/s and the values is close to the ideal hydrosilylation reaction order of 2.The fitting degree of aG" with the K-S reaction model is up to 0.998.Ea= 86.79 kJ/mol obtained by K-S model is similar to the apparent activation energy Ea obtained bytgel.So,based on the K-S reaction model,the application of loss modulus(G")as the characteristic parameter analysis of silicone rubber curing process is the most reasonable.(2)The curing process of carbon nanoparticles filled silicone rubber with different shapes was studied by small amplitude oscillatory rheological method.The results indicates that the CB/silicone rubber composite system was not hysteresis,the curing lag phenomenon was observed in WMNT/silicone rubber system,while the graphene/silicone rubber system was the most serious.The surface functional groups of nanoparticles have no effect on the curing hysteresis of the composites,and the phenomenon of lag is attributed to the difference of morphology and surface area with differentad sorbability,which measured by XPS,BET nitrogen adsorption,optical microscopy and Raman spectroscopy.The adsorbability of nanoparticles to silicone rubber is: graphene> MWNT> CB.(3)The gelation process,electrical conductivity,thermal stability and the strain hardening behavior of the nano-SiO2/[BMIM]BF4 systems were studied by large amplitude oscillatory rheological method.The results show that the content of 40 wt% SiO2 is the critical gel concentration of SiO2/ [BMIM]BF4.The SiO2 /[BMIM]BF4 ionogels have good thermal stability and ionic conductivity.The strain hardening behavior of SiO2/[BMIM]BF4 is the result of the combined action of strain and strain rate during the oscillation process,which mainly occurs at the high strain rate during the oscillation process,that is,the strain rate dominates the hardening behavior.In addition,the change of the third-order phase angle in the strain process shows that the third-order phase angle changes from the fourth quadrant to the first quadrant with the increase of the strain amplitude,and the strain increases to the SiO2/[BMIM]BF4 ionogels.The contribution of hardening behavior decreases and the contribution of strain rate increases. |
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