Mouldable glass that could replace plastic

A new technique has been developed that allows glass to be shaped via injection moulding
13 April 2021

Interview with 

Frederik Kotz, University Frieberg


A fractured pane of glass


Most of us enjoy snapping pictures using the camera on our phones, and although the quality can be good, it could be better and that’s because the lens of the camera is made out of molded plastic rather than the optically superior glass. This is because, although glass was first made around 5000 years ago, no techniques have existed to mould glass in the same way that can for plastic. This makes manufacturing more costly. Traditionally glass is made out of sand - or silica - particles that are melted together at extremely high temperatures and then blown, ground, or etched into the right shapes. But now Frederik Kotz at the University of Freiburg has developed a technology to make glass mouldable, potentially solving the problem, as he told Eva Higginbotham...

Frederik - At the moment there are a lot of components which are made out of plastics, which we actually want to have made out of glasses. But at the moment, we don't have the possibility to shape these components in glasses at a compatible cost. We developed a novel method which now allows us to shape glass like classical plastic injection moulding.

Eva - What is injection moulding?

Frederik - You basically use a plastic - you melt it and you inject it into a mould. And the nice thing is that this process is extremely fast and can produce a lot of components at once.

Eva - How have you managed to make this new technology?

Frederik - We developed new materials, which we termed Glassomer - it's a mixed word of glass and polymer, which is something like a plastic. And these materials basically consist of a very high amount of glass powder within a plastic binder. You can still shape these materials like a classical plastic. After the shaping process, we put these components into an oven and convert them to real glass.

Eva - So is it like you have essentially a plastic goo that contains bits of sand?

Frederik - Exactly. It's basically like a plastic glue, which holds together this really high amount of sand glass particles.

Eva - The glass that you get out of it at the end, is it the same as just regular glass?

Frederik - Yeah. What you get in the end is a hundred percent class. It's really a pure glass, which you maybe know the glass fibres which we use for a high-speed internet. These types of glasses you can fabricate with this process.

Eva - What's the benefit here? Because we've designed all of these machines and we've designed various different products to use plastic. Why should we ever really want to use more glass?

Frederik - Glass has some very unique properties which are superior in many aspects. Optical transparency, thermal and chemical resistance - these glasses can be heated up to a few hundred degrees and nothing will happen. The mechanical stability is also higher. There's a reason why a car windshield is always made out of glass and not out of plastic because a plastic window would basically scratch over time.

Eva - And what about the environmental consequences of your technique? Is it better than normal glass?

Frederik - It is better. The huge advantage is that we don't melt the glass, we use a process which is called sintering, which is basically working at temperatures way below the melting temperature. So the temperature is really reduced. And we put a lot of effort also in designing this plastic binder that you can regain during this process - a really high amount of this material - and can reuse it multiple times.

Eva - Is this going to be much more expensive than making something out of plastic, like we've already organised the world to be able to do, or more expensive than making regular glass?

Frederik - In terms of making glass it's actually cheaper, especially if you look into more complex glass components. If you have multiple of these so-called etching processes then you need really big clean room facilities, high-tech etching machinery, and this makes the glass extremely expensive. Glass as itself is a super cheap material, it's even cheaper than many plastics which are out there.

Eva - What sorts of applications do you think this new material might have?

Frederik - So we see a lot of applications in different fields from optics, like camera modules, to data communication, coupling elements for glass fibres, to the pharmaceutical sector, vials for vaccines, which need to be stored at low temperatures where you need the thermal stability.


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