Cellulose as the New Plastic – Can it Help with the Microplastics Problem?
- Ned Patton
- Apr 14
- 9 min read
I came across a really interesting article in one of my science feeds that doesn’t usually produce ideas for my newsletters. The name of this newsletter is “ScienceAdvisor”, and it had this interesting article in it that I found intriguing (https://www.science.org/doi/10.1126/sciadv.ads2426?utm_source=sfmc&utm_medium=email&utm_campaign=ScienceAdviser&utm_content=distillation&et_rid=1078013933&et_cid=5584860). This newsletter comes out periodically from AAAS which I’m a member of because I subscribe to their weekly journal – Science. The article in ScienceAdvisor is a synopsis of an article in “ScienceAdvances”, and it is in the field of material science which of course is germane to composite materials as most of you have gathered by now.
The article is titled “Fully circular shapable transparent paperboard with closed-loop recyclability and marine biodegradability across shallow to deep sea”. This is a bit of a mouthful as a title, but what a group of Japanese researchers have done is to start with cellulose powder, dissolve it in a lithium bromide solution to create a gel and then press dry the gel into a thick transparent sheet that is identical to paperboard without all of the impurities that make paper opaque.
This picture isn’t precisely what they made but it is a picture of a transparent cellulose film about the same thickness as the piece of paper that is next to it. I put this here as the lead pic to make a point. Here is a transparent composite material that is made using entirely plant-based sources and is compostable and completely biodegradable even in the deep ocean where things biodegrade much more slowly. It is impervious to boiling water and can be formed into all sorts of food packaging, disposable cups and plates, and probably even disposable transparent tableware. Best of all it can be made using what is now being shoved into landfills.
The reason that I am putting this into a composite materials newsletter is that this is a wonderful example of researchers using the properties of the most abundant organic material on the planet to make a very useful and completely biodegradable composite material that can be formed just like modern plastics.
To give some background to this, we all know of cellophane but did all of you know that cellophane is actually a very thin, transparent film made out of cellulose. And it is also a composite material because the shorter chains of cellulose are used to crosslink the longer fiber-like chains of cellulose to make these films. This process was originally created using some very caustic chemistry, including using carbon disulfide and sulfuric acid, but over the years people have modified the process to enable them to make this stuff without all of the toxic sulfur chemistry.
Cellophane is actually made using what is called “regenerated cellulose” which is pure cellulose that has been modified by either sulfur based solvents or their replacements (not lithium bromide), then poured into very thin sheets and covered with or immersed into a non-solvent solution to remove the sulfur or other replacement solvent compounds. If it is done just right, this leaves a very thin film that can be washed and dried and rolled up so that you can use it in your kitchen. The history of cellophane is rather interesting and is another of the happenstance discoveries that are throughout the composites industry. It was invented by a Swiss chemist who was looking for a waterproof material and noticed that the placemats in his favorite French restaurant were hydrophobic when someone spilled wine on them. He went back to his lab and experimented with spraying cellulose solutions onto rayon fabric and when he peeled off the waterproof layer because the fabric was too stiff, he had a transparent water proof film. The patent for this was granted in 1912. The Wikipedia article about it is pretty interesting reading (https://en.wikipedia.org/wiki/Cellophane).
But this post is not about cellophane, it is about the transparent paper board (they call it tPB) these Japanese researchers came up with made entirely out of cellulose. The process for making this stuff is roughly similar to how cellophane is made, except that they did not use the sulfur based chemistry, and they have no need to wash out the solvent they use. Instead of the sulfur chemistry they used a lithium bromide solution which is heated to make the cellulose dissolve in the lithium bromide. Then when the solution with dissolved cellulose cools it forms an amorphous mass of gel that can be shaped into sheets or cups with the thickness needed to make something like a drink cup or a plastic plate. And, when this solution cools and the gel forms, the lithium bromide solution goes away with a quick rinse of water and you end up with a thick transparent gel of pure cellulose that can be formed like a thermoplastic.
The graphic below is from their paper showing how their closed loop process works and what they can make using pure cellulose.
What the authors go on to say is that while they have proven the concept using cellulose powder, the cellulose for the process they developed can come from any source. The most abundant source of course is the one I have talked about in this newsletter several times, biomass from agricultural and forest products waste. This waste material is a very abundant source of cellulose as well as lignin and a number of other very useful organic compounds.
Since cellulose is the most abundant organic compound on the planet, what this represents is a process that can be scaled up very easily and that could fairly quickly replace the current petroleum based polyethylene terephthalate packaging that is ubiquitous in the food products industry. Polyethylene terephthalate is the most common thermoplastic made and represents, with polyethylene itself from sheeting and other things, the majority of the microplastics problem that I have also talked about in other newsletters recently. So, not only is this petroleum based plastic not biodegradable like cellulose plastic is, it is also contributing significantly to the “garbage patch” in the middle of the Pacific Ocean.
Back to cellulose plastic here, one very good thing about this process is that it requires very little energy to make this transparent paper board. Even if you include the process energy of extracting pure cellulose from agricultural and forest products waste, for which there are already well established processes, the energy required to make this transparent paper board will be substantially less than what is required to start with raw petroleum. All you have to do is to mix the cellulose into a water solution of lithium bromide, heat up the solution (115° to 155° C) so that it dissolves into the lithium bromide solution. When you cool the solution back down to room temperature you end up with a transparent gel in a lithium bromide solution. Rinse the gel in water, press it into whatever form you want, dry it, and you have a transparent cellulose plastic cup or plate.
With petroleum-based plastics you first have to get the oil out of the ground, which is a costly and energy intensive process itself. Then you have to refine it into the products that you need, which is also an energy intensive process and usually done using the cracking towers that you see in every oil refinery. Just the processing or refining of the petroleum to get the precursors to polyethylene and polyethylene terephthalate requires more energy than extracting cellulose from waste biomass. And it also uses up a valuable resource that could be put to better use than making a single use Bud Light cup for spectators at a baseball or hockey game.
Interestingly, once I looked into this, I found that it is not a new research area or a new area of materials science. There are a number of different ways of making transparent paper, all of which use cellulose but end up with more of a film-like product rather than a formable plastic. Not something as thick as the paperboard the Japanese researchers made, something much more like notebook paper, so this transparent paper board is new and something of a breakthrough for this material.
As an example of others making something thinner out of cellulose, in 2022 a multinational team led by researchers in India, with members of the research team from South Korea and the UK (https://phys.org/news/2022-01-strong-thin-transparent-cellulose-nanofibers.html) developed a transparent paper in the form of a film composite made of cellulose nanofibers held together by naturally occurring reinforcing glycerol. Glycerol is an organic alcohol with three carbon atoms and three OH groups so it makes a very good glue for long chain cellulose. Lignin is another much longer chain organic alcohol with lots of OH groups and is of course the plant glue that I have talked about in this newsletter a number of times. Glycerol is similar in that respect to lignin, and both are used by the plant kingdom as glues for different uses. So, this whole area of materials science research is a good example of nature’s string and glue again being used to make useful materials for humanity without the use of petroleum.
This thin film, somewhat thicker than cellophane, is also very tough and completely transparent even though it is considerably thicker than cellophane. They say in the 2022 article cited above that they are looking for investors to take this technology from a TRL 4 (demonstrated in a laboratory) to a TRL 9 (proven in an operational environment). Since this film is thicker, stronger, and tougher than thin film cellulose like cellophane, it has quite a few potential practical uses. It is sort of half way between the thin film cellophane and this new transparent paperboard. So its uses are things like oxygen barrier film to protect electronics or for food packaging, being the structural component of thin film sensors, for optoelectronic devices since it is completely transparent and can be printed on easily, for biomedical patches (think glucose monitors) and a whole host of other products.
This is just another example of what researchers all over the world are doing with this ubiquitous organic molecule. And it demonstrates that the material science of today and that will develop into the future will be focused on how to harness the compounds that are provided to us by our current biology. And it will use only the carbon and other light atoms that are everywhere around us and the energy from our sun to make all manner of useful things for humanity that do not involve pumping oil up out of the ground.
So, in closing all I have to say is ‘This Bud’s for you!’ in a transparent PaperBoard cup no less.
That’s about it for this week. And it is about time I got off this soap box for the week. As always, I hope everyone that reads these posts enjoys them as much as I enjoy writing them. I will post this first on my website – www.nedpatton.com – as then on LinkedIn. And if anyone wants to provide comments to this, I welcome them with open arms. Comments, criticisms, etc. are all quite welcome, especially from those of you that are thinking along the lines of plant-based composite materials and their inherent biodegradability. I really do want to engage in a conversation with all of you about composites because we can learn so much from each other as long as we share our own perspectives.
I especially want to encourage people that are in university laboratories working on this sort of thing to reach out to me so that we can begin a dialogue about how to get your efforts out to a wider audience so that your efforts will see the light of day and be a part of solving the existential crisis of climate change that it appears that we are rapidly approaching. I also want to encourage anyone that is interested in pursuing a career in composites or material science in general, especially if they are interested in harnessing the chemistry that already exists in nature, to contact me so that we can connect up with other like-minded people. It does after all take a village.
On another front, my publisher and I had a bit of a discussion about the title of my next book this week, but that has thankfully been resolved. After thinking about it for a few days early this week I didn’t like what we had come up with, so we worked together to shorten it a bit and make it more germane to the subject of the book. So, finally, the title is going to be, “Sustainable Composite Materials: A Roadmap to a Circular Economy”. This will work on two fronts. First it is pretty clear from the outset what the book is about – Sustainable Composite Materials - and second, it keeps the whole idea of circularity in the composites industry in the title of the book. There is a very business-forward slant to the book, and it is the industry itself that I am preaching to in the book, so I’m good with what we came up with. I’d like to know from you what you think. The book truly is a roadmap to a circular and sustainable business model for the industry which I hope that at least at some level the industry will follow. Only time will tell. And of course I got our daughter working on it right away, and what she came up with will be at the bottom of next week’s post. So stay tuned and you will see how it is going to look. Hopefully people will like it enough that they will buy it. And of course I hope that they read it and get engaged. We need all the help we can get. And time is not our friend in this regard.
Finally, I still need to plug my first book, so here’s the plug. The book pretty much covers the watershed in composites, starting with a brief history of composites, then introducing the Periodic Table and why Carbon is such an important and interesting element. The book was published and made available last August and is available both on Amazon and from McFarland Books – my publisher. However, the best place to get one is to go to my website and buy one. I will send you a signed copy for the same price you would get charged on Amazon for an unsigned one, except that I have to charge for shipping. Anyway, here’s the link to get your signed copy: https://www.nedpatton.com/product-page/the-string-and-glue-of-our-world-signed-copy. And as usual, here’s a picture of the book.
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