Casein-based Bioplastic

Robert Murray-Smith. 2020. Step By Step: Hemp–Casein Bioplastic. Video. Retrieved from (Members only).

From the video's description, “This should give all the instructions needed as well as an indication of what you can do to make it all your own - best of luck and I hope it helps.”

  • 0:19–1:15: “Now 'hemp plastic' is, strictly, a bit of a misnomer, because they're not really plastic in themselves. What you do, is add them to some kind of resin, you let that resin set, and you get a composite panel. … Mostly what you'll see is that they're added to standard polyolefin plastics like polypropylene, polyethylene, or some kind of a resin, an epoxy resin or a PU resin, something like that. But they have been, essentially, impregnated with some other kind of resin, formed into a panel or object, and allowed to cure. And then these have been talked about as 'hemp plastics'. So in themselves, the hemp plastic idea is a little bit misleading — it is, in fact, just a composite, where the fibre being used in the composite material is hemp-based.”
  • 1:31–2:17: “So hemp plastics and glass-fibre and carbon-reinforces plastics are all really of the same kind of family. So if you're going to make a 'hemp plastic', what are the considerations? Well it's like any composite that you make — a composite is all about the mixing, the dispersion of two things, one in another, so that you get an even matrix of material, and you get that combined effect. Now hemp as a natural fibre is extremely strong — it has an awful lot of really great properties, it's why they used to make rope out of it, and they make all kinds of things out of it, it's a really very strong material. So it's idea for a composite, if you think about it. If you can break up those fibres so you can get good distribution, then it's actually ideal.”
  • 2:17–2:53: “Now my big thing, really, is bio-degradable plastics. So when we made the hemp bio-degradable plastic, we didn't use an olefin plastic … What we used was a natural protein plastic, that is casein. Now this milk protein here is rennet casein. It's produced in mass quantities, incidentally. And for anybody who thinks using food is a bad idea, because milk is a food-stuff, 50% of milk gets wasted before it gets to the consumer stage, just because it's unfit for human consumption.”
  • 3:30–4:30: “Now we chose casein as essentially the resin, and hemp, essentially, the reinforcement fibre. Now casein as a resin is really well known. It was called 'galalith' many years ago, and it was used to make buttons and rods and all kinds of material, because it was, actually, a very good plastic. It was thermoset, which led to a lot of problems, it used formaldehyde to cure it because casein would, in fact, absorb water, and that is an issue, obviously, in a material that you want to last a long time. But it absorbs the water, falls apart, and it rots. So you needed some kind of curing agent, just like you use in a urethane resin, where you use a formaldehyde. Casein used formaldehyde to cure it. That led to lots and lots of problems. The curing time was dependent on the thickness of the casein, and if it was quite a thick casein, it could take months to cure, and so it fell out of favour, and you didn't see it much for a very long time, particularly when the petroleum plastics came in.”
  • 4:36–5:26: “However, because of the sudden resurgence of interest in degradable polymers and polymers from renewable resources, casein has resurfaced. And the thing about casein is that the bulk of the research has been in curing agents that are not formaldehyde-based. Now the curing agent I chose was this stuff — it's tannic acid. Now I chose tannic acid because it's really well researched, actually. If you go onto Google Scholar and you look at casein and tannic acid, … you'll find tonnes of papers where people have been working on casein cured with tannic acid for film formation, for body plastics, all that kind of stuff. A lot of research back up to casein and tannic acid as a curing agent.”
  • 5:26–6:15: “So that's what we're going to be doing. We're going to be using casein as a resin, tannin to cure the resin, and then hemp as a distributed fibre within that resin, to give that resin strength. Now the tannin doesn't make the casein waterproof, it makes it water-resistant. That's actually a good thing. Because our world is water-based — everything requires water. If water can't get into something, then neither can the organisms that eat that plastic. And so a 100% waterproof plastic would be no better that the plastics we're using at the moment — they would just be particles drifting in the sea, poisoning everybody. You don't want a 100% waterproof casein. What you want is a balance of water resistance, to the degree that you want to use the casein.”
  • 7:14–7:35: “So those are the essential components of what we're going to be looking at. And just to review them, hemp fibre is the reinforcement, casein is the plastic resin, and tannic acid as the curing agent that gives a degree of water-resistance, depends on how much tannic acid you put in there — put a lot in there, very resistant, not much, not so much.”
  • 7:35–8:16: Examples of little things they've made using different proportions of ingredients, and their properties including: (a) a compressed casein handle (very hard, very water-resistant); a casein plug made by adding glycerol to the mixture, too (resulting in quite a flexible / bendable plastic); a casein film made with added graphene (1% w/w resulting in an 'immensely strong' plastic); and a reference sample made with only a minimum of tannin.
  • 8:34–8:52: “What we're going to go there here is the basic work that needs to be done in order to form that plastic. Other additions that you would do are up to you, really, to experiment with, and you should add them at the dispersal stage so that you get good, even dispersion.”
  • 8:55: The start of the process' description proper.
  • 10:50–11:39: On the use of an 'indian spice grinder', comprising two granite stone wheels, a pot with a granite bed that rotates, and an 'integrated pipe' that allows the wheel assembly to be affixed (under variable tension) to the stationary base. Also, “but if I leave that off, those stones bounce up and down. As they bounce up and down, they're going to pummel the fibre, and it is, in fact, a hollandering machine, so this will hollander the fibre, and it basically pummels the fibre, flattening it out, and separating those fibres out.”
  • 11:39–12:15: “And in order to do that, I'm going to add 60g of my hemp fibre and 2L of water, and give that some time, just to go around there, pounding those fibres into individual fibres. Now it usually takes about 12 hours to do that because it's quite a slow mechanical process. … This is the first stage of that dispersion process, because we need those fibres hollandered out into a nice stream that we can intermix with.”
  • 13:31–14:26: “Now you can tell it's ready because it goes kind of gelatinous — all those fibres get separated out and get into the wash water. Now I added 2L of water here. If you're finding it's getting a bit too gelatinous, well, just add more water. You've got to keep it so it's nice and liquid, and so those fibres get separated easily. Any water you add, you're going to have to take out later, so don't add tonnes and tonnes of water — just add the water that you need. Now when you feel that those fibres have separated, and you can tell, because all those 'sticks' that you saw in there when you added the hemp have gone — it'll all just look like a smooth, even, jelly sort of paste. When it's add that stage, we'll add the casein. Now we added 60g of hemp, and in here, I've got 60g of rennet casein. That really is just a random guess — it's something to play with, have a play with those ratios, because that will alter the quality of the material that you're making.”
  • 14:48–16:04: “Now casein, when it's like this, is like a tight ball of protein. So we add it here, and all that will happen is that those balls will go in between the [hemp] fibres and stay as balls — that's all that happens, unless we add this stuff. Now this is 4g of KOH in 200mL of water. What happens then, is that those bundles of casein will open out into fibres, and as we continue mixing it, those fibres will intermingle with the cellulose fibres that we've put it. Now you don't need to add the cellulose fibres. If you just want to make the casein, you would just add the casein to the water and the KOH to open them out, then you would add the linking agent, which is the tannic acid, and we'll come to that later, and then we would drop the casein back out again. But here, because we're making a composite material, we want to entangle all of those fibres. … And those [casein] strings along with those hemp fibres are going to intermingle as they continue mixing. Now you need to give that a fair amount of time for that to happen — a couple of hours or so — and then you can look in on it, because you will find it going even more gelatinous, and if it's getting too gelatinous, add more water.”
  • 16:46–17:54: “What we're going to do now is cross-link them. In order to cross-link them, we use this stuff. This is tannic acid, and it's dissolved in a KOH solution. Now there's 6g of tannic acid in there, and that's 10% by weight of the casein we've put in here — it's quite a lot, so if you use less grams, like 3g, 2g, 1g, you won't get as much cross-linking, and it will be more permeable to water. If you use more, like 10g, then you get an impermeable plastic at the end of it. There is a limit to how much you can put in because some won't cross-link. But that's the tannic acid — it's this kind of brownish powder, it looks like dried tea actually, and it's dissolved in 200mL of water, with 2g of KOH in there to help that dissolve. … And now we're going to pour that in there and give it 12 hours.”
  • 19:06–19:25: “Now one of the reasons it takes so long is to mix it with the hemp fibres that we put in there. If all you actually want is the casein, then just leave out the hemp fibres — you put the water in there, you add the casein, you add the KOH, add the tannic acid, give it about 12 hours to mix, and then proceed from there with what we're going to do.”
  • 20:55–22:27: “Now everything is nicely mixed in there — remember that casein has opened up into fibres now that have been cross-linked by the tannic acid. Now what we want to do, really, is make those casein fibres close back up again. And when the close back up, they'll close back up around the hemp fibres, and they'll be linked. So this stuff will aggregate up, and sink to the bottom. Now it's only going to do that in an acidic solution, so we have to acidify that solution. … I'm going to use HCl — it's a 37% — and I've pre-mixed that here in a 1:5 ratio, there's 50mL of HCl in 200mL of water, and we add that to our alkali solution to neutralise it, and acidify it. Now we're adding an acid to an alkali, so don't chuck the whole thing in there, or you really will be sorry. And as it gets acidified, you should be able to see that it's beginning to agglomerate. See that — it's going from the brown colour, which was the tannin, to this kind of whitish colour, and that whitish colour is where the casein is curling up around the hemp fibre.”
  • 22:39–23:09: “So I mixed up 250mL of acid solution … and I've used about 50mL of that to get this. Now all I have to do is leave that to settle. Now we can filter it at this stage — it'd be quite a deal quicker — but I'm going to leave it to settle a little bit, and go and grab a cheese cloth because right now, that stuff is clumped together and will [won't?], in fact, just go through a cheese cloth.”
  • 24:02–25:20: “Now there will be some fat and bits of wasted material in there which is why it's that kind of yellow colour. The more brown it is, then the more tannin that you've lost. So having that yellow colour is telling me that it's losing fat, but quite a lot of the tannin has cross-linked in with the casein there. And all I then do is leave that to drip, obviously. Now at this stage, if you wanted to add a plasticiser like polyethylene glycol or glycerine, it's at the mixing stage, before you add the tannin, that you would add the plasticiser. Now we did a method of making graphene using glycerine and an upright ball mill — it's an earlier video — that's an excellent way of getting graphene and plasticiser into this, because you don't have to wash the graphene out of that, you can just use it directly in here, adding it at that point just before you add the tannic acid.”
  • 26:27–27:00: “There is our casein, hemp and tannic acid plastic. All we do with that now is dry it into a powder. Now you don't want to dry it as a solid lump like this because it's a nightmare to powder. Let that get a bit dryer, and then chop it up into small bits, maybe with a blender — I actually use a pasta or mashed potato maker that pushes this through — that helps it to dry, and it will dry in little lumps that are then much, much easier to powder.”
  • 27:10–27:30: “And that's what the finished powder looks like … And all we have to do with that is heat it and extrude it, or put it in a press and give it some heat and some pressure, and we'll get our plastic parts.”
  • 27:48–28:49: “I put it back into the cheese cloth and put it into the press, and it formed this dryer cake — a lot of moisture came out, and when you saw how much water we're using, we want a lot of moisture out because it shortens the drying time. Now this is kind of a mid-damp stage — it feels sort of dry, but it isn't, it's still quite moist. And we don't want to let it dry like that; if you let it dry like that, it'll be next to impossible to do anything with it. What we need to do is get it into a kind of breadcrumb style, so this is it, this is when we've got it into a nice light, fluffy, breadcrumb. When that dries, we can use that as our resin in our moulds. Now it'll stay like that forever, really — I mean, it is milk so it will rot until you finish the curing process, but pretty much it'll stay like this nice, dry crumb. When it's thoroughly dry, then we can put it into a press. Remember, when we pretty this stuff, we apply heat and pressure, and that's how we form these kind of rigid waterproof materials.”
  • 29:23–29:42: “There's just lots and lots of scope [adding different fibres, etc.] in order to be able to make this as a plastic engineering material that will rot away when it's in the environment. Now to get that crumb, all I did was put it in a 'Blitzer' [small 'Bullet'-style blender]. And we don't want to blitz it for absolutely ages because we'll just kind of force it into a big lump again, we just want to kind of blitz it on and off 'til it forms a breadcrumb.”

If you start with a sheet of hemp felt, impregnate it with the resin, and dry it, you can get a pretty tough panel.

For more flexibility, you can also use simple hemp fibres, be they 'raw' / unrefined, rolled up or chopped up.

  • Last modified: 2022-03-19 17:36
  • by Peter