Cordierite is widely used as a carrier for automobile exhaust gas purification catalysts because of its excellent material properties such as heat resistance, corrosion resistance, porosity, and low thermal expansion. The cordierite honeycomb uses the orientation of the raw material particles to produce low thermal expansion of the honeycomb structure, and can be produced by extrusion molding.
According to the molecular composition of cordierite (2MgO·2Al2O3·5SiO2), talc, kaolin and alumina can be used as raw materials. The molding clay is introduced into the flap from the supply hole in the flap, and after subdividing, it is expanded toward the thin wall and joined together, thereby obtaining the quality of the elongation and the bonding property. In addition, as the honeycomb body after extrusion molding, in order to maintain the shape, the yield value of the clay is high, that is, the binder is selected to optimize the fluidity and self-sufficiency of the clay. .
The raw material powder, the binder, the auxiliary agent (lubricant, the surfactant, etc.) and the water are mechanically kneaded, and then continuously extruded by a screw extruder or extruded by a hydraulic ram extruder. In general, the bonding agent used for extrusion molding exhibits a highly viscous bonding property as long as it is used in a low concentration aqueous solution. Commonly used are methyl cellulose (MC), carboxymethyl cellulose (CMC), polyoxyethylene (PEO), polyvinyl alcohol (PVA), hydroxyethyl cellulose (HEC) and the like. MC is very soluble in water and gels quickly when heated. CMC is well soluble in water with high dispersion and stability. PVA is widely used in various forms. The lubricant reduces the friction between the powders, and the surfactant enhances the wettability of the raw material powder with water.
Lack of plasticity, the clay with expansion characteristics makes the extrusion less smooth and the surface defects increase. Therefore, there should be an evaluation index for the performance of the binder. The plasticity method for evaluating the soil is to apply stress such as twisting, compression, and stretching, to obtain a relationship between stress and deformation, a method using a capillary rheometer, and a method of viscoelasticity. In this way, the self-sufficiency and fluidity of the clay can be evaluated. When evaluated by the viscoelastic method, it can be concluded that both the self-defense and the fluidity increase when the amount of the binder is increased to a certain extent. That is to say, an increase in the amount of the binder blending contributes to an increase in the plasticity of the raw material.
Organic materials are the main binders for special ceramics. The rational selection of these organic materials is the key to ensuring product quality. In production, the selection should be based on the characteristics of the powder, the shape of the product, and the forming method.
Surgical Head Cap,Medical Scrub Caps,Surgical Hood Cap,Surgical Caps Online
Ningbo Autrends Prevention Products Co., Ltd , https://www.autrendsafety.com