Time-dependent properties of bimodal POM — Application in powder injection molding

Powder Injection Molding is applied for manufacturing complex and precise components from metal, ceramics or cemented carbide powder. It basically consists of mixing the powder and a polymeric binder, injecting this mixture in a mold with the desired form, debinding and then sintering. Among the debinding techniques applied, catalytic debinding of polyoxymethylene (POM) stands out due to the high debinding rates and low risk of cracking. In this work, the potential use of a bimodal POM-based material as the main binder component was evaluated by comparing its thermal and time-dependent properties to a standard monomodal POM. In addition, the potential optimization of this bimodal material was investigated by preparing five new formulations of bimodal POM with higher concentration of short polymeric chains (wax). This work has shown that macroscopic properties of POM are sensitive to the addition of these short chains. For instance, the magnitude of the complex viscosity for the commercial bimodal material was found to be more than 67% lower than for the monomodal POM in the whole range of frequencies studied. Finally, a new formulation of bimodal POM was suggested with 8% of added wax concentration (in weight), resulting in a material with very fine structure that has shown even better flowability than the commercial bimodal POM, without compromising its thermal and mechanical properties.

Graphical AbstractThe potential use of a bimodal POM-based material with higher concentration of short polymeric chains (wax) added was evaluated as the main binder component in PIM. 8 wt.% of added wax was suggested, resulting in a material with better flowability than the commercial bimodal POM, without compromising its thermal and mechanical properties.Figure optionsDownload as PowerPoint slideResearch Highlights
► Potential use of a bimodal POM-based material as the main binder in PIM technology.
► Optimizing bimodal POM with higher concentration of added short polymeric chains.
► New formulation of bimodal POM with 8 wt.% of added short polymeric chains.
► Adding short polymer chains results in finer structure and better flowability.
► POM optimization does not compromise material's thermal and mechanical properties.