Eva Hnatkova

Rheological investigation of highly filled polymers: Effect of molecular weight

The paper deals with rheological properties of highly filled polymers used in powder injection molding. Within the experimental framework seven PIM feedstocks based on superalloy Inconel 718 powder were prepared. Each feedstock contains the fixed amount of powder loading and the same composition of binder system consisting of three components: polyethylene glycol (PEG) differing in molecular weight, poly (methyl methacrylate) (PMMA) and stearic acid (SA). The aim is to investigate the influence of PEG’s molecular weight on the flow properties of feedstocks. Non-Newtonian indices, representing the shear rate sensitivity of the feedstocks, are obtained from a polynomial fit, and found to vary within measured shear rates range from 0.2 to 0.8. Temperature effect is considered via activation energies, showing decreasing trend with increasing of molecular weight of PEG (except of feedstock containing 1,500 g.mol−1 PEG).

Rheological and thermal performance of newly developed binder systems for ceramic injection molding

In a novel binder system, carnauba wax was considered to replace the synthetic backbone polymers (polyolefins) enhancing the environmental sustainability of Ceramic Injection Molding (CIM) technology. The paper presents comparison of the rheological performance and thermal behavior of the aluminum oxide CIM feedstocks based on a binder containing carnauba wax with those consisting of a commercial binder. Further, acrawax (N, N’-Ethylene Bis-stearamide) has been considered as another possible substitute of polyolefins. For both proposed substitutes there is a significant reduction in viscosity, and in case of carnauba wax based feedstock also in processing temperature, which is essential for injection molding of reactive powders. Thermal characterization comprised analyses of single neat binders, their mixtures and mixtures with aluminum oxide. The presence of powder lowered melting temperatures of all tested binders except of polyolefin. Further depression in melting point of poly(ethylene glycol) is obse...

Mechanical Properties of New and Recycled PIM Feedstocks

This paper deals with the mechanical properties of test specimens of commercially available PIM feedstocks based on a stainless steel powder. After injection molding, a part of the polymer binder has been removed in water. This process was followed by thermal removal of residual binder and sintering at 1360 °C in hydrogen atmosphere. For production of the mechanical test bars fresh and recycled feedstocks were employed. The aim is to determine the changes in mechanical performance resulting from injection molding processing stage, especially possible separation of feedstock components – the stainless steel powder and the polymer binder

Design of the Tool for Production of Ear Ventilation Tubes

This work deals with a development of a tool for ear ventilation tube production. Ear tubes are medical devices, which allow ventilation and provide pressure equalization in the middle ear cavity for prolonged period of time; in case of repetitive inflammation. These implants are normally made from metals or classical polymeric materials. Whereas, today, the effort is to develop bioresorbable tubes based on polylactic acid, which could replace currently used material. The benefit provides no requirement of secondary surgery for their removal. The size of ear implants is only in millimetres and the tool for their manufacturing requires a special technology. In this paper, two tubes and a transfer mold for their production was designed using 3D CAD software Catia V5R18. Subsequently, the special manufacturing process for the mold cavity plates using the rapid prototyping and electroforming technology was proposed. The designed tool is intended for biodegradable tubes, which will be further tested in the laboratory.