MIM process how to select binder?

MIM at the time of skim, water soluble adhesive additives such as polyethylene glycol or polyvinyl alcohol, can be dissolved in warm water for easy removal. Although they are very attractive, because of low cost, environmental impact is minimal, but can not be used in MIM.

There are two main reasons:

A. water soluble adhesive agent is easy to absorb moisture from the air, from solid to rubbery, dimensional stability;

B. steel powder is easy to rust.

2 why POM can be used as a binder?

A. from the chemical structure analysis: backbone for carbon and oxygen atoms alternating structure with a certain polarity, full contact and the surface of the metal powder; side chain hydrogen atom and steric hindrance, the regularity of the main chain strong, so POM crystallization degree high, generally in more than 70%, low viscosity and have ability to maintain the shape of the green. The two characteristics estimation can only use crystal to reconcile.

From the analysis of B. molecular weight: POM polymerization degree is not high, easily thermal depolymerization. POM molecular weight is small, low viscosity, ensure as far as possible the few binder can meet the injection molding conditions. In addition, smaller molecular weight to easily from green removal and is not easy to generate residual stress; high degree of crystallinity, POM has good self lubrication.

C. finally, POM is a thermoplastic material that can be recycled to reduce the cost from another aspect.