As the quest to combat plastic pollution continues, new research has explored the potential for developing environmentally friendly alternatives to plastic, like sulphur polymers. Olivia Holdsworth spoke to scientist Dr. Justin Chalker about his latest research and the options being explored.
Justin Chalker is a Senior Lecturer in Synthetic Chemistry at Flinders University. He is an expert in organic and polymer chemistry.
This interview has been edited for clarity and length
Olivia Holdsworth: What prompted the study?
Justin Chalker: Our lab and our collaborators are broadly interested in designing new and useful materials that are made from sustainable resources…sustainable plastics, rubber, ceramics that are made from things that are renewable or even waste materials, but also materials that can be generally recycled. And so we are working towards a future in which we can have all the advantages of the useful things that we get from polymers and plastics and different types of rubber but do that in a sustainable way that doesn’t harm the environment.
OH: Why is this research important?
JC: There is a worldwide issue of persistent plastic pollution where you have seen islands of waste plastic floating around in the oceans and it causes serious harm to ecosystems. And so it is important to design new types of plastic that won’t persist in the environment, that can be generally recyclable, and that are prepared from resources that are sustainable. For instance, we have made many of our new types of polymers from plant oil such as laminin or canola oil, we can even use waste cooking oil to make these materials. And then our other key component to this new type of recyclable material is sulphur and sulphur is highly abundant geologically and it is also a by-product of petroleum, there are literally mountains of sulphur lying around the planet waiting to be used for something important. So we hope this will be a first step in that direction.
OH: What does this mean for the future of recycling? Will the research you have done be commercially viable?
JC: The types of materials that we are making, they actually are currently being tested in a variety of different applications. We have made these materials to capture mercury pollution from air, water, and soil, we have used these materials to clean up oil spills, and other groups around the world have shown that these high sulphur content materials can be used for batteries, high-end optics, infrared imaging, night vision lenses. Now, how will this affect the future of plastics and the future of polymers? Well this is just the first step. We can’t say that these materials will replace all of the different types of plastics, but the first step is important because we can demonstrate that you can control these properties and you can design these materials to be functional replacements for traditional plastics that are made from petroleum resources. So even though the chemical composition is quite different, we can now tune in properties to give these materials a particular hardness, a particular flexibility, even a particular colour. And so that control and those design principles are critical in making sure that we can replace plastics that can’t be recycled and get into the environment with ones that are generally recyclable.
OH: Are you saying that these sulphur polymers that you are able to create can substitute a wide range of different types of plastics?
JC: That is the long term goal. We certainly in this initial study can’t replace all plastics, rubber, glass and ceramics straight away, but we can at least show that these materials can have diverse properties that we would require if you want to replace those non-recyclable materials.
OH: What has the response been like to the research you have done?
JC: It has only been released this week so the interest is growing, but it is quite exciting because we are not only trying to make materials that are recyclable, we are also trying to synthesise them from very expensive and sustainable building blocks and sometimes even make them from waste products. And this will feed into a circular economy, this will feed into sustainable plastics that are environmental friendly, and the interest for these types of materials is only going to grow.
OH: What happens next? What are the next steps in research?
JC: So we have quite a few different lines of research ongoing. One important aspect is to learn how to scale these materials up, because if you want them to be a building block for the many different things we use polymers for then you will have to be able to make them on [a large] scale. So in the first instance we are making hundreds of grams, but in some cases we are actually preparing many kilograms for these materials and that is quite important if you want to see these materials used in applications like environmental remediation, we have used some of these polymers in agriculture as components for slow-release fertiliser, and in order to realise the commercial reality of these things we need to be able to make them on a large scale reliably and safely.
OH: Do you have any idea what that time frame is going to look like?
JC: It depends on what specific application. I mean we are already in the process of working to commercialise one of these polymers. So in this study we have disclosed a whole panel of different polymers that range from soft flexible rubber to very hard rubber to really hard transparent glass and plastic. One application that we see moving forward quite rapidly is one of the polymers that we have made from canola oil, even waste cooking oil and sulphur. It turns out this material which has a rubber consistency is excellent at removing mercury from water. And so one of the first commercial applications we envisage are kits in which this polymer is used to trap mercury from air or from contaminated water.
OH: So is this process economically viable? Is this something that can be scaled up?
JC: So the good news is that the feedstocks, the building blocks of these materials are quite inexpensive. Like I said, we can actually use waste cooking oil and in some cases we go down to the local fish and chip shop to get our starting materials. So instead of converting that into biofuels we can use some of that to make our polymers. So the raw materials are quite inexpensive, sulphur is very inexpensive as well: they make seventy million tonnes a year in the petroleum industry as a by-product of petroleum refining. They will pay you to take it away. The equipment that you will require to make one tonne of these new types of polymers that becomes a little bit more costly and requires an investment. We have built a pilot reactor here in Adelaide that allows us to make ten kilograms an hour and the purpose of this is to make a material that will be used in removing mercury from contaminated water.
OH: Final thoughts on the next steps going forward?
JC: I think the next steps are looking at the applications in which these materials will be used commercially and industrially and introducing that as a viable product it will become more apparent to everyone that there are other options for developing sustainable plastics, rubbers and ceramics that are sustainably produced and that can be generally recycled.