The Properties Of Powder Binder

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May 9, 2022

The binder used in ceramic injection molding is usually an organic polymer compound, the purpose is to mix with the ceramic powder, increase the fluidity, help the injection molding stage to proceed smoothly, and keep the shape of the green body stable after molding and during degreasing. . When preparing and selecting a binder, the following points need to be considered:

The binder itself should have good fluidity. In general, the fluidity of the binder is negatively correlated with the number of molecular weights, and also has a certain relationship with the distribution of molecular weights.
The binder has good wettability with the ceramic powder. The addition of the binder can make the powder have a certain fluidity, provided that the two have good affinity and wettability. It can be improved by adding some surfactants (such as stearate, titanate, silane, etc.), the principle is to act as an interface bridge between the powder and the binder, reduce the viscosity when the two are mixed, and improve the fluidity .
The diversity of binder components, considering the improvement of the fluidity of injection molding and the subsequent degreasing process, the binder composed of multi-component organic substances is usually used. In the degreasing process, the multi-component binder is divided into steps During the process, the component with the lowest melting point is separated from the green body first, forming tiny air bubbles, which is helpful for the discharge of the following binder components.
The binder system should have good thermal conductivity and low thermal expansion coefficient. In addition, the binder should also be non-toxic and harmless, environmentally friendly, non-volatile and non-moisture absorption, and repeated heating performance. invariant characteristics.

Using three organic compounds (PP, SA and PW) as binders, and by calculating the feed viscosity, activation energy and non-Newtonian index, the optimal binder formulation of injection molding AIN powder was finally obtained. Wu Aiping [15] studied the interaction mechanism between the multiple components of the binder, and found that ethylene-vinyl acetate copolymer (EVA) can refine the spherulite structure of polyoxymethylene (POM), improve POM and HDPE ( The compatibility between high-density polyethylene) promotes the uniform dispersion of the two and reduces the size of the dispersed phase.