The Preparation And Application Of Polyhedral Oligomeric Silsesquioxanes Hybrid Materials

Polyhedral Oligomeric Silsesquioxanes (POSS), with a typical cage-shaped three-dimensional structure at nanometer level, are nanoplatforms with one to eight reactive or nonreactive organofunctional groups attached to the eight silicon vertices of cubic silsesquioxane. POSS owned typical cage structure, nanometer-sized and good compatibility with polymers, which can lead to nanoscale hybrid materials at molecular and nanometer-sized levels. POSS are also a new kind of environmentally friendly nanometer-sized organic-inorganic hybrid marerials and display great otential in modifying polymer materials, their rigid inorganic core can provide molecular reinforcement, while the organic groups which connected to silicon can increase the compatibility and processability with other polymers, and improve the interaction between organic and inorganic phases. The glass-transition temperature, mechanical properties and thermal stability of polymer materials have been greatly improved by the incorporation of POSS. Therefore, it is valuable to develop a new class of POSS and POSS-containing polymer hybrid materials. The main research content of this paper are as follows:1. The incompletely condensed Heptamethyltrisilanol-POSS ((CH3)7Si7O9 (OH)3) was synthesized via using silane directly hydrolysis and condensation reaction trichloromethylsilane (CH3SiCl3). The structure and properties were characterized by FTIR, XRD?1H-NMR?29Si-NMR SEM and TG-DTG. The results show that:Heptamethyltrisilanol-POSS has a typical incompletely condensed cage-like structure and The TG/DTG curves shows that the thermal decomposition of the synthetic product below 800? takes place in a single step and is characterized by a only one DTG peak centered at about 238?, which can be mainly attributed to the dehydration and condensation of silanol group of Heptamethyltrisilanol-POSS and Si-C bonds cleavage and reorganisation in a solid structure. The average values of Ea associated with the stage were determined to be 128.5±5.5 kJ mol-1, the reaction mechanism function of the stage is g (a)=-ln(1-a)1.05(NO.15). The values of the pre-exponential factor A for the stage is 1.02×1011 s-1.2. On the basis of preparation of T7, POSS/Sb2O?POSS/MgO?POSS/ Al(OH)3 composite flame retardant materials were still synthesized via using silane directly hydrolysis and condensation reaction CH3SiCl3 with the Homogeneous suspension of Sb2O3. MgO and Al(OH)3 Then, the flame retardancy of Polycarbonate (PC) was modified by incorporation of POSS/Sb2O3?POSS/MgO?POSS/Al(OH)3 composites via direct melt blending. The flame retardant properties and thermal stability of PC composites were investigated by LOI, UL-94 and TG-DTG. The results show that:The addition of POSS/Sb2O3?POSS/MgO?POSS/Al(OH)3 composites significantly improved the value of LOI and residual. Moreover, the addition of POSS/Sb2O3?POSS/MgO?POSS/Al(OH)3 composites at 4% lead to the maximum increase of LOI at 28.3%?28.6% and 29.6%, respectively. The PC composites all had a UL-94 rating V-0 with the content of POSS/Sb2O3> POSS/MgO?POSS/Al(OH)3 composites at 4%. At the same time, the incorporation of POSS/Sb2O3?POSS/MgO?POSS/Al(OH)3 composites into PC matrix slightly reduced the initial thermal decomposition temperature of the PC composites.3. The mono-amine-functional POSS, (CH3)7Si8O12(CH2)3NH2, was synthesized via using y-Aminopropyltriethoxysilane (NH2(CH2)3Si(OC2H5)3) to corner-capping the incompletely condensed Heptamethyltrisilanol-POSS ((CH3)7Si7O9(OH)3). The structure and properties were characterized by FTIR? XRD?1H-NMR?29Si-NMR?SEM and TG-DTG. Then, epoxy resin (E44) was modified by incorporation of T8-NH2 at different mass fraction of 0%,1%, 2% and 4%, respectively. The prepared nanocomposite coatings were applied on the mild steel surface and were cured in a conventional oven. Corrosion performance of the coated mild steel specimens was investigated employing polarization curve, salt spray test, soaking coating weight experiment and SEM. The results show that:(1) T8-NH2 has a typical completely condensed cage-like structure and The TG/DTG curves shows that the thermal decomposition of the synthetic product below 800? takes place in two well-defined stages. The first mass loss stage begins at about 100?, ends at about 257?, and is characterized by DTG peak at about 183?, which can be mainly attributed to the loss of some crystalline water in the sample. The second one, starting from about 419? and mainly taking place at approximately 558? and ending at about 720?, involves a DTG peak at about 558?, which can be mainly attributed to the decomposition of the organic corner groups and the formation of a Si-O-Si network structure. The average values of Ea associated with the two stages were determined to be 82.6±4.9,92.8±9.0 kJ mol-1, respectively, the reaction mechanism function of the two stages are as follows:(?) g(?)= (1-?)-0.425-1(No.3), (?) g(?)= (1-a)-0.5-1(No.3), respectively. The values of the pre-exponential factor A for the two stages were 5.42×108,4.40×104 s-1, respectively. (2) When the incorporation of 2% T8-NH2 possessed the best corrosion performance and dispersion and compactness in coating. At the same time,2% T8 NH2/E44 composite coating has good physical barrier function, and also waterproof and penetration, the protection of the metal surface level best, corrosion potential was about 232 mV, corrosion current fell by nearly 258 times, corrosion rate fell by nearly 134 times.