Effect of Increased Powder–Binder Adhesion by Backbone Grafting on the Properties of Feedstocks for Ceramic Injection Molding

Abstract

The good interaction between the ceramic powder and the binder system is vital for ceramic injection molding and prevents the phase separation during processing. Due to the non-polar structure of polyolefins such as high-density polyethylene (HDPE) and the polar surface of ceramics such as zirconia, there is not appropriate adhesion between them. In this study, the effect of adding high-density polyethylene grafted with acrylic acid (AAHDPE), with high polarity and strong adhesion to the powder, on the rheological, thermal and chemical properties of polymer composites highly filled with zirconia and feedstocks was evaluated. To gain a deeper understanding of the effect of each component, formulations containing different amounts of HDPE and or AAHDPE, zirconia and paraffin wax (PW) were prepared. Attenuated total reflection spectroscopy (ATR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and rotational and capillary rheology were used for the characterization of the different formulations. The ATR analysis revealed the formation of hydrogen bonds between the hydroxyl groups on the zirconia surface and AAHDPE. The improved powder-binder adhesion in the formulations with more AAHDPE resulted in a better powder dispersion and homogeneous mixtures, as observed by SEM. DSC results revealed that the addition of AAHDPE, PW and zirconia effect the melting and crystallization temperature and crystallinity of the binder, the polymer-filled system and feedstocks. The better powder--binder adhesion and powder dispersion effectively decreased the viscosity of the highly filled polymer composites and feedstocks with AAHDPE; this showed the potential of grafted polymers as binders for ceramic injection molding.

Fused Filament Fabrication of WC-10Co Hardmetals: A Study on Binder Formulations and Printing Variables

“…Notably, the M4-P feedstock displayed the lowest extrusion force, suggesting it had the lowest viscosity among all samples. This finding is consistent with literature on non-grafted PP, which posits that the absence of grafting agents, such as maleic anhydride, might lead to decreased material viscosity, easing the extrusion process [44].…”

Optimising Mg-Ca/PLA Composite Filaments for Additive Manufacturing: An Analysis of Particle Content, Size, and Morphology

“…The differences in surface energies and polarities result in weak adhesion [ 32 ]. Furthermore, large standard error was observed, likely resulting from porosity induced by the differential solidification temperatures of paraffin wax and PLA during the extrusion process.…”

“…This increase is attributed to the larger total surface area of the particles, which enhances their interaction with the surrounding fluid [ 38 ]. Conversely, poor adhesion between the particles and the fluid can reduce this effect, as non-adhesive particles may act as lubricants [ 32 ].…”

Interactions of polymeric components in a POM-based binder system for titanium metal injection moulding feedstocks

“…However, due to the relatively short chain lengths of stearic acid, interlinking strength among binder components is often weak [7,12]. Hence, including polymers with a polar group as interfacial agents among binder components is beneficial in enhancing the interlinking strength of binder components and improving the adhesion force on the powder surface [13,14].…”