Effects of Polyelectrolyte as a Dispersant on Slip Casting of Ceramic Slurries

在注浆成型中，需要在保持流动性的同时制备浓缩浆。聚电解质作为分散剂对浆液的增稠是有效的，除了分散和稳定外，聚合物在使浆液流态化方面具有独特的功能。流动点是指开始流动的一定数量的粉末所需的最小介质量(增稠极限)。浆体在稠化极限附近的流动性受分散剂的种类、分散剂的浓度和相对分子质量以及浆体中固体含量的影响。伴随流态化的分散和增稠的极限应与分散剂在陶瓷颗粒上的吸附层的长度延伸结构(分散剂的构象)有关，也与浓缩浆中固体颗粒之间的相互作用有关。一种具有静电效应的聚电解质分散剂和添加剂…根据聚丙烯酸铵盐分子(PAA)在氧化铝上吸附的平均面积乘以增稠极限时水层的平均厚度，根据PAA的吸附量和不同分子质量的PAA存在时氧化铝的流动点，计算了PAA在氧化铝上的平均壳层体积。PAA分散剂对氧化铝分散的位阻效应导致了无屈服应力的流动。这是由于PAA在吸附壳层中的伸展由球形变为长轴的椭球体，超过了PAA分子量在10,000-20,000之间时范德华引力达到的有效距离。本文还建立了聚电解质的测定方法，并讨论了pH变化对聚合物在浆体中的构象变化、聚合物的吸附量以及在分散剂存在下的流态化分散的影响。较少

It is desirable in slip casting to prepare concentrated slurries whilst retaining fluidity. A polyelectrolyte as a dispersant is effective for thickening of the slurries and that polymer have a characteristic function in fluidizing slurries, other than that dispersion and stabilization. The flow point refers to the least amount of a medium (the thickening limit) required for a definite amount of powder of a start to flow. The fluidity of the slurries in the vicinity of the thickening limit was affected by a kind of dispersant, the concentration and molecular weight of dispersants and the solid loading in the slurries. The dispersion accompanied by fluidization and the limit of thickening should be related to the structure of the length extension of dispersant (the conformation of dispersant) in the adsorption layr on the ceramic particles and also to the interaction among such solid particles in the concentrated slurry. A polyelectrolyte dispersant has electrostatic effect and an addit … More ional steric effect since the polymer expands in the adsorption layr thereby exceeding the effective distance that the van der Waals attraction force operates over.An average shell volume occupied in the adsorption layr on alumina by a polyacrylic acid ammonium salts molecule (PAA) defined as the average area occupied by an adsorped PAA on alumina multiplied by the average thickness of the water layr at the limit of thickening, has been calculated from the adsorbed amount of PAA and from the flow points of alumina in the presence of PAA of different molecular weights. A steric effect of the PAA dispersant on the dispersion of alumina resulted in a flow with no yield stress. This was due to the change of the extension of PAA in the adsorption shell from a sphere to an ellopsoid with a long axis which exceeded the effective distance that the van der Waals attraction force reaches at a molecular weight for the PAA of between 10,000-20,000.It was also developed the determination method of polyelectrolyte and discussed the effects of pH changes on the conformation changes for polymers in the slurries, the adsorbed amount of polymers and the dispersion accompanied by fluidization in the presence of dispersant. Less