The degradation of poly(ethylene glycol) in an Inconel 718 feedstock in the metal injection moulding process

Abstract

The degradation and stability of polymer binders in feedstock for metal injection moulding (MIM) have been rarely investigated. Feedstock is a mixture of polymer constituents and metallic powder and is subject to variations in temperature and the complexity of its mechanical effects. The mixture is pressed and squeezed in a mixer with two counter-rotating screws and injected into the mould cavities. This paper investigates the degradation and stability of polymer constituents under the conditions of mixing and injection. The interactions among different constituents were measured and analysed. The methods and application of the equipment are introduced with sufficient detail. The kinetics of decomposition for poly(ethylene glycol) (PEG) are studied to explain the mechanism of its degradation. The measurement of the carbonyl group resulted in a quantitative discussion of the decomposition. The effects of PEG degradation on its behaviour were also investigated and found to show benefits for the metal injection process. Moreover, it is proved that the combination of PEG and polypropylene (PP) is not favourable for a homogenous binder. Thus, other constituents should be found to use instead. The research reveals the degradation and stability of polymer binders under conditions of MIM technologies. It provides a reference for the choice and validation of MIM binder constituents.

Insights into the Enhanced Oxidative Thermal Stability of Nanoparticle Organic Hybrid Materials Developed for Carbon Capture and Energy Storage

“…In both HPE and NOHM-I-HPE cases, the majority of the FTIR spectrum remained unchanged upon exposure to oxidative thermal degradation conditions. This is consistent with the literature, because it has been shown that PEO 83 and PEG 84 polymers undergo random chain scission degradation reactions, where some of the chains are broken down until they are small enough to be volatilized. It is common for the remaining liquid residue to possess a composition very similar to the starting polymer, 83,84 as was observed in this study.…”

“…The characteristic peaks of the FTIR spectra relevant to the oxidative thermal degradation were found in the range of 1400–1900 cm –1 . Figure shows the FTIR spectra of the liquid residue of HPE and NOHM-I-HPE collected after being exposed to air at 120, 140, 160, and 180 °C for 1 h. In comparison to the starting samples, both liquid residues of HPE and NOHM-I-HPE exhibited the appearance of a peak at about 1720 cm –1 , which is consistent with carbonyl stretching − and expected for a PEO polymer subjected to heat and an oxygen-containing atmosphere. ,− Additionally, the HPE samples thermally degraded in air exhibited another peak at about 1680 cm –1 , while the liquid residue from NOHM-I-HPE did not. This peak corresponds to carbonyl stretching, specifically from a free primary or secondary amide. ,− This suggests that the amine-terminated end of the HPE polymer could be “protected” or “shielded” from oxidative thermal degradation in the case of NOHM-I-HPE as a result of its ionic bonding with the linker molecule staying intact (confirmed by the small peaks at about 1635 and 1525 cm –1 ).…”

Extrusion of metal powder-polymer mixtures: Melt rheology and process stability

“…the feedstock cannot be recycled indefinitely. In fact, Royer et al (2015) proved that a degradation of the water-soluble binder can be expected for prolonged exposures at high temperatures.…”

Experimental investigation and numerical simulation analysis of sintered micro-fluidic devices

“…The mixing stage generally consists of the preparation of high-loading polymers with thermoplastic polymers and spherical metallic powders [3]. The metallic powder volume loading is usually between 58% and 64% in volume for 316L, with a particle size of 16 microns (median diameter) [4]. Furthermore, the process was developed for a large range of material powders, from austenitic and martensitic stainless steels [3] to titanium alloys and pure-grade [5] and nickel-based superalloys [6,7].…”