# Development of a Soda-Lime Glass Feedstock for Injection Molding

## TL;DR

Researchers developed a new soda-lime glass feedstock that can be injection molded and sintered into dense glass parts.

## Contribution

A novel soda-lime glass feedstock system was developed and shown to be feasible for injection molding and thermal processing.

## Key findings

- Glass feedstocks with 55 Vol% and 60 Vol% solid load were successfully compounded.
- Injection molded parts achieved near-theoretical density after sintering.
- The process chain demonstrated feasibility for producing dense soda-lime glass parts of various shapes.

## Abstract

What are the main findings?
Development of new soda-lime glass containing feedstocks.Feasibility of injection moldability demonstrated.Dense glass parts after debinding and sintering obtained.

Development of new soda-lime glass containing feedstocks.

Feasibility of injection moldability demonstrated.

Dense glass parts after debinding and sintering obtained.

What is the implications of the main findings?
Dense sintered soda-lime glass parts of different sizes can be realized by injection molding and thermal postprocessing.

Dense sintered soda-lime glass parts of different sizes can be realized by injection molding and thermal postprocessing.

Injection molding has been used for many years in the fabrication of thermoplastic parts with different complexities. With metal and ceramic injection molding, it is possible to realize at the end of the related process chain sintered metal and ceramic parts. Parts made from glass are rather seldom realized applying powder technology methods. This work describes the production of devices made from a commercial soda-lime glass applying the process chain of powder injection molding, covering the individual process steps like compounding, shaping, debinding, and sintering. In the first step, a binder consisting of polyethylene glycol (PEG) with different average molecular masses (4000, 8000, and 20,000 g/mol), polyvinyl butyral (PVB), and stearic acid (SA) were used for compounding new feedstocks with a solid load of 55 Vol% and 60 Vol%. As filler, a soda-lime glass with an average particle size of 6.1 µm, an almost symmetrical particle size distribution, a specific surface area of 0.78 m2/g, and a spherical morphology was applied. The measured equilibrium torque during compounding was low, with values between 2.5 and 5.5 Nm depending on the solid load and average molecular mass of the investigated PEG. All feedstock possessed a pseudoplastic flow behavior in the shear rate range between 10 and 3500 1/s. Small disk-shaped parts, as well as large cuboids and plates, were injection molded to a good quality. These green bodies were pre-debinded in water to remove the PEG, subsequently followed by thermal debinding to eliminate the remaining organic moieties. The concluding sintering in the temperature range between 660 and 680 °C delivered glass parts with huge density values close to 100% of the theoretical value, as measured by the Archimedes method. The principal feasibility of glass injection molding with a suitable feedstock system could be demonstrated successfully.