堇青石水基流延坯片的干燥动力学研究

Study on Drying Kinetics of Cordierite Sheets by Aqueous Tape-casting

以纳米堇青石粉体为原料,聚丙烯酸钠为分散剂,聚乙烯醇为粘结剂,聚乙二醇为增塑剂,通过水基流延成型制备了堇青石陶瓷基片。研究了流延坯片的干燥工艺及干燥动力学。结果表明,堇青石水基流延坯片干燥过程分为恒速干燥和降速干燥两个阶段。在恒速干燥阶段,坯片表面水分的蒸发占主导地位。随着干燥过程的进行,水分在坯片内部的扩散传输开始占据主导。在降速干燥阶段,由于坯片内高分子三维网状结构的束缚作用和高分子链上羟基(-OH)的亲和作用,干燥速率减慢。干燥温度过高会破坏坯片内部三维结构,导致坯片表面疏松。干燥温度为25℃时,得到的堇青石生坯表面光滑,柔韧性好,致密度高。

Nano cordierite powders were used as raw materials. Sodium polyacrylate, polyvinyl alcohol and po- lyethylene glycol were acted as dispersant, adhesive and plasticizer, respectively. The cordierite sheets were prepared by aqueous tape-casting. The drying process and drying kinetics were investigated. It turned out that the drying process of cordierite sheets could be divided into constant rate drying stage and failing rate drying stage. In the con- stant rate drying stage, the evaporation of water on sheet surface is dominant. With the drying process, internal diffu- sion of water began to dominate. In the falling rate drying stages, the decrease of drying rate is due to the constraint of internal three-dimensional reticular structure of the polymer and the affinity interaction of hydroxyl （-OH）. If the drying temperature is on the high side, internal three-dimensional structure could be destroyed and sheet surface was loose. The sheets with prefect surface, good flexibility and high density were obtained at 25 ℃ drying temperature.