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1.
The use of phosphazene bases in combination with water was proved to be efficient in order to obtain polysiloxane polymers from cyclic monomers. Only a few minutes are necessary to obtain polymer chains with a monomer concentration of 5% at the equilibrium. For that purpose the space which is between a rheometer's plates is the most convenient device to monitor this reaction concerning a chemical and viscoelastic point of view. Therefore, here is proposed a chemo-rheology study that leads in the same time to the chemical kinetics equations and to the variation of the viscoelastic functions during the polymerization. In this way different catalysts are used and their efficiencies are compared as a function of their “basicity tank”. Whatever the experimental conditions involved are, viscosity versus polymer concentration or conversion shows a master curve for catalysts suitable to be used under extrusive conditions. Thus, only a few experiments are needed in order to develop a model which can be used to foresee the variation of the viscosity during the reaction. 相似文献
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3.
《Journal of the European Ceramic Society》2021,41(13):6677-6686
An optimized recipe for 3D printing of Mullite-based structures was used to investigate the effect of MgO sintering additive on the processing stages and final ceramic properties. To achieve dense 3:2 mullite, ceramic filaments were prepared based on an alumina powder, a methyl silicone resin, EVA elastomeric binder and MgO powder. Using 1 wt% MgO and a dwell time of 5 h at 1600 °C, a dense mullite structure could be obtained from filaments with a diameter of 1.75 mm. Ceramic structures with and without sintering additive were printed in vertical and horizontal direction, to investigate the effect of printing direction on mechanical strength after sintering. Using four-point bending test, it was demonstrated that by using MgO, the printing orientation did not affect the mechanical strength significantly anymore. The low Weibull modulus could be explained by the closed porosity that emerge during the degassing of the preceramic polymer due to cross-linking. 相似文献
4.
Renata FurtunaSilvia Curteanu Florin Leon 《Engineering Applications of Artificial Intelligence》2011,24(5):772-785
This paper presents an original software implementation of the elitist non-dominated sorting genetic algorithm (NSGA-II) applied and adapted to the multi-objective optimization of a polysiloxane synthesis process. An optimized feed-forward neural network, modeling the variation in time of the main parameters of the process, was used to calculate the vectorial objective function of NSGA-II, as an enhancement to the multi-objective optimization procedure. An original technique was utilized in order to find the most appropriate parameters for maximizing the performance of NSGA-II. The algorithm provided the optimum reaction conditions (reaction temperature, reaction time, amount of catalyst, and amount of co-catalyst), which maximize the reaction conversion and minimize the difference between the obtained viscometric molecular weight and the desired molecular weight. The algorithm has proven to be able to find the entire non-dominated Pareto front and to quickly evolve optimal solutions as an acceptable compromise between objectives competing with each other. The use of the neural network makes it also suitable to the multi-objective optimization of processes for which the amount of knowledge is limited. 相似文献
5.
聚硅氧烷改性醇酸树脂的研究 总被引:4,自引:0,他引:4
采用共缩聚方法合成了聚硅氧烷改性的醇酸树脂;探讨了反应温度、催化剂和原料配比对缩合反应的影响,测试了改性树脂的部分性能。 相似文献
6.
合成了一系列低分子α,ω-二羟基二甲基硅氧烷齐聚物及1,3-二(3-羟丙基)四甲基二硅氧烷.鉴定了预聚体的结构,选择了最佳合成方法. 相似文献
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8.
The para-toluene sulfonic acid (p-TSA) was used to catalyze the moisture curing of an organic/inorganic hybrid coating system. The organic phase was based on the isocyanurate of 1,6-hexamethylene of diisocyanate (HDI). The inorganic phase was based on the prepolymerized oligomers of tetraethyl orthosilicate (TEOS). An alkoxysilane-functionalized HDI isocyanate was added into the coating formulation to aid in phase miscibility. The general coating and tensile properties were evaluated as a function of the acid catalyst concentration. In addition, the films were analyzed using differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). The results indicated that the acid catalyst enhanced the adhesive properties of the hybrid coatings. The addition of the acid catalyst increased the changed crosslink density of films and decreased the crystallinity of the organic phase. 相似文献
9.
Linear polyurethanes were obtained the reaction of 1,6-hexamethylene diisocyanate with poly(ɛ-caprolactone)diol and butane-1,4-diol. Synthesis was carried out in the presence of 1, 3 and 5 wt.% of polydimethylsiloxane-poly(methyl methacrylate) core–shell nanopowder. Solutions of resulting polyurethanes were cast on PTFE plates and dried at 140 °C to form films. The presence of structures originating from modifier was confirmed by IR and XPS spectroscopy. DSC analysis revealed the presence of crystalline phase in all samples. Contact angles were determined using standard fluids and surface free energy parameters were calculated. The results of these investigations proved that modification with silicone-acrylic nanopowder resulted in significant increase in hydrophobicity of polyurethane surfaces Changes in surface characteristics were also reflected in surface images obtained in AFM studies. It is suggested that the polyurethane composites obtained in this study can be tested as coatings for biomedical applications. 相似文献
10.
Functionalized siloxane-based solid polymer electrolytes were synthesized using a platinum-catalyzed silylation reaction.
The ionic conductivities of these solid polymer electrolytes were measured as a function of the concentration of lithium bis(trifluoromethylsulfonyl)imide
(LiTFSi) salt. The highest ionic conductivity and lowest activation energy of solid polymer electrolytes were observed to
be 1.15 × 10−4 S cm−1 (25 °C) and 3.85 kJ mol−1, respectively. The interface property between electrolyte and electrode and thermal stability of the polymer electrolytes
were found to enhance after they were functionalized with acrylate, and the functionalized electrolytes were observed to maintain
a glass transition temperature as low as that of other siloxane compounds. Thus, modifications involving acrylate with ethylene
oxide group substitution provide a route for carrier ions and enhance both the ionic conductivity and mechanical properties
of the siloxane structure. 相似文献