Analysis of the Effect of HPMC Addition on the Porosity and Pore Size Distribution of Honeycomb Ceramics

HPMCAs a commonly used functional additive in the preparation of honeycomb ceramics, it has multiple functions such as thickening, water retention, pore forming, and lubrication, and plays a key role in the entire process of green body forming, drying, and sintering. The variation of its addition amount will directly change the porosity size and pore size distribution of honeycomb ceramics, which is an important process parameter for regulating the internal pore structure of ceramics.

Within a reasonable range, as the amount of HPMC added gradually increases, the overall porosity of honeycomb ceramics shows a significant upward trend. HPMC belongs to high molecular weight organic substances, which can be uniformly dispersed in the raw material system during the mixing and molding stage of the green body, and can uniformly fill the internal voids of the green body after molding. During the subsequent high-temperature sintering process, HPMC will gradually undergo thermal decomposition, combustion, and volatilization, forming connected or independent pores in the originally occupied space. The higher the amount added, the more pores are left after the organic matter evaporates, and the proportion of internal voids in the green body increases, resulting in an overall increase in porosity. If the addition amount is too low and the pore forming components are insufficient, the structure of the sintered body will be denser, the overall porosity will be lower, and the permeability and adsorption performance will be limited.

The addition of HPMC also significantly affects the uniformity of pore size distribution in honeycomb ceramics. When added in moderation, polymer particles can be uniformly dispersed in the raw material, and the pore size formed after decomposition is regular and evenly distributed, with a concentrated pore size range and good overall pore structure stability. When the addition amount continues to be high, it is easy to cause local agglomeration, HPMC clustering and aggregation. After sintering and volatilization, local large pore size pores will be formed, accompanied by a disorderly distribution of small pore size pores, resulting in an increase in pore size span, distribution dispersion, and a decrease in pore structure regularity.

On the contrary, when the amount of HPMC added is too low, in addition to low porosity, there may also be situations where the pore size is too small and the proportion of micropores is too high, which can easily cause poor pore connectivity, internal channel blockage, and affect the breathability, filtration, and catalytic carrier performance of honeycomb ceramics. Insufficient addition at the same time can also reduce the plasticity of the billet, making it prone to defects during molding, indirectly affecting the overall uniformity of the sintered pore structure.

In process applications, it is necessary to control the appropriate addition range, ensuring both the target porosity and maintaining a regular pore size distribution. Excessive addition not only damages the uniformity of pore size, but may also lead to excessive drying shrinkage of the billet, resulting in problems such as cracking and deformation; If the addition amount is too low, it is difficult to achieve the ideal pore forming effect, and the pore index of the product cannot meet the requirements of the operating conditions.

In conclusion,HPMCThe amount of addition is a key factor in regulating the porosity and pore size distribution of honeycomb ceramics. Moderate increase can steadily improve porosity and maintain uniform pore size distribution; Excessive amounts can easily lead to uneven pore size and structural defects, while insufficient amounts can result in insufficient porosity and poor connectivity. Reasonably matching the HPMC addition ratio can accurately regulate the pore structure parameters of honeycomb ceramics, adapt to the performance requirements of different application scenarios such as filtration, exhaust gas treatment, catalytic carriers, etc.