Injection molding technology creates a new era in glass production

Glass is one of the ancient materials of humanity, produced around 3500 BC in Egypt and eastern Mesopotamia. Its manufacturing process is the same as before: melting silicon dioxide or silicon at a temperature of about 2000 ℃, and then using various techniques to shape it.

Modern glass manufacturing technology can mass produce certain shapes of glass, but cannot produce complex glass instruments required for modern biomedical applications in large quantities.

A study published in Science reports a new glass manufacturing method that can make this material look like plastic, allowing scientists to mold vaccine bottles, curved pipes for experiments, and other complex shapes.

In 2017, a research team led by Frederik Kotz, a microsystem engineer at the University of Freiburg in Germany, began studying the difficulty of mass producing complex glass instruments. They modified a 3D printer commonly used for printing plastic or metal to forge glass.

Researchers mixed silica nanoparticles with a polymer that can be cured by ultraviolet light to create a printable powder. After printing the desired shape, they cured the polymer with ultraviolet light to maintain its shape. Then, the researchers put the mixture into an oven to burn off the polymer and melt the silica particles into a continuous glass structure. This method has been effective, but the production process is too slow and still cannot be fully industrialized like plastic.

Now Kotz and colleagues have extended their method to the injection molding stage (a process of mass producing plastic parts such as toys and car bumpers by ton).

Researchers once again started with tiny silica particles and mixed silica with two polymers - polyethylene glycol (PEG) and polyvinyl butyral (PVB). This mixture produces a sticky paste like toothpaste. The research team sends the paste into an extruder and presses it into prefabricated molds in the shape of disks or small gears.

Take away the mold, the parts can maintain their shape but are very fragile. To make them harder, the researchers washed away the PEG with water and then fired the remaining material in two stages: the first stage burned out the PVB at 600 ℃, and the second stage fused the silica particles at 1300 ℃.

We can obtain high-purity silica glass of any shape, "Kotz said. These glass components have the optical and chemical properties required for commercial telecommunications equipment and chemical reaction instruments.

However, this new method of mass producing glass parts still faces a bottleneck: in order to ensure that the glass parts do not break, PEG can only be slowly cleaned out within a few days. If the speed of this process can be accelerated, this glass forming method may be widely used.