Transcription
This is a bag of Industrial Waste which I purchased because I suspect it might hold the key to cheap and incredibly effective thermal energy storage. Hi, I'm Ben, and on this channel, we often explore advanced scientific research and see if it can be simplified and then recreated in a barn by a regular guy like me. So today, we'll be reopening the topic of phase change materials, which we explored a few months ago to make personal cooling packs that last many times longer than ice and can be recharged without refrigeration.
Phase change materials are thermal batteries, and this one, based on sodium sulfate, can soak up an incredible amount of heat in the process of melting. To recap the earlier project, we made these by adding sodium sulfate to hot water until no more can dissolve. Add in some table salt to lower the melting temp and a thickener like xanthan gum to make a stable gel. These bags of the finished PCM are amazingly useful, freezing right around room temperature and staying comfortably cold for hours on end.
As is usually the case when I make a video on a new topic, I often learn a lot more about that topic after the fact, once I've read all of your comments and become aware of new leads to look into. In the case of salt-based PCMs, that is phase change materials like this sodium sulfate variety, I was aware of one problem that these can have called phase separation, where crystals settle to the bottom over time, which reduces the effectiveness for thermal storage. What I didn't realize is how big of an issue this is and how much research has gone into attempted solutions.
The problem of crystals separating and settling in a PCM basically prevents their effective use for any purpose where they would remain stationary for a long period of time. In just a few thermal cycles, salt crystals will have settled out, throwing off the ratio of the rest of the ingredients, and the battery basically becomes dead. In my early experiments, the focus was to use this mixture in personal cooling packs, which naturally mixes and agitates the PCM. Anytime you pick this up to use it, motion prevents large crystals from forming or settling, and so the issue is avoided.
It's not so easy to fix this phase separation problem if you had 10,000 lbs of this stuff lining the walls of your house to regulate the temperature, or maybe embedded into a road to prevent it from icing over. Those are the sort of applications that need to remain stable over thousands of thermal cycles and many years of time without mixing or maintenance. So that is the big challenge facing widespread use of salt PCMS, and the one I hope to solve with industrial waste.
Now, in the last few years, one scientific paper seems to have stumbled on a massive breakthrough. This paper, which is titled "Stable Salt Hydrate-Based Thermal Energy Storage Materials," not only reports that they've made a sodium sulfate PCM which shows no loss in capacity over at least 150 freeze-thaw cycles, but the starting capacity itself has been increased by 290%. The storage capacity of these cold packs we made previously is already impressive. This is unbelievable.
So how do they pull this off? They say that they use an additive, dextran sulfate sodium (DSS), which works to stabilize crystal formation and prevent particles from settling. It does this by coating the particles and giving them an electrostatic charge so that they repel one another like magnets, and that way they never actually fall to the bottom. So let's look up this DSS to see what else it's used for and if we can buy some to play with.
And the main use for DSS seems to be giving mice irritable bowel syndrome. Oh no, no. Oh, okay. Um, who wants to handle a chemical that's used to give mice IBS? Not really something I want to play with. After further research, I realized that the mechanism which allows DSS to cause gastrointestinal distress is that it's a detergent, like soap. Soap dissolves grease and fat, which is what cell walls are made of, and if you swallow soap, it can damage the cells in your digestive tract, allowing bacteria to break in and cause a sore. In fact, various detergents like SLS are known to cause sores in your mouth, and if you experience that problem frequently, you might want to check the ingredients in your toothpaste and find one that doesn't contain a detergent. Anyways, it seems like DSS is probably no more dangerous than a strong soap. As long as you don't eat it, you're unlikely to end up like the poor mice in these studies. No. Oh, that is not fun to learn about.
Sadly, DSS is very expensive and basically only sold to professional research labs. I found one store on eBay offering samples with no labeling or details whatsoever about purity or molecular weight. $220 after shipping for 50g. That's not happening, at least not as my first choice. In a way, I don't mind that DSS is expensive because the research group that discovered its effectiveness rightfully won a patent for its use to improve PCMS. Hopefully, they'll put that patent to good use in developing new products. But in the meantime, I'd like to discover something new, maybe an additive that works in the same way as DSS, improves performance of PCMS just as effectively, and is much less expensive.
This is sodium lignosulfonate, a waste product of paper manufacturing. A chunk of wood is basically made of two different things: lignin and cellulose. Now, cellulose is a linear chain-like molecule which is useful to make paper, whereas lignin is like a branching fibrous web that glues the cellulose together. To collect cellulose from wood, the lignin needs to be removed, and the way that that's done is to react it with highly charged sulfur compounds which bind to the lignin, turning it into something like a detergent which is soluble in water so that it can just be washed out to leave clean cellulose behind. This is the waste that's left over: sodium lignosulfonate.
Now, this has some uses, mainly as a concrete additive to cause the particles to stay suspended with less water, which does sound pretty promising for our use. But the majority of this stuff is literally just burned or thrown onto roads to melt ice like rock salt. A small amount actually goes into animal feed, so apparently the IBS issue isn't too bad with this one. I hope. Basically, this is garbage, and you can't get cheaper than that. If this works to improve PCM performance, we'll have given a whole industry a profitable new use for its waste and made thermal energy storage significantly more viable. Like DSS, this is an organic polymer which has been reacted with sulfur compounds. Dextran is a polymer made by lactic acid bacteria after they digest sugar and then further processed into DSS by adding sulfate groups (that's SO4). And this is lignin with added sulfinate, which is SO3. Hopefully, that difference in one oxygen atom isn't terribly important for our purposes, but if it is, we might be able to tack an extra oxygen on if it comes to that. I really hope that this works right out of the bag.
So let's start by mixing up some sodium sulfate PCM and then we'll add various quantities of the lignosulfonate to the recipe to find out if it does indeed increase stability. This is sodium sulfate and table salt, which I will dissolve in hot water to make a saturated solution. See my earlier video on this topic if you're interested in a tutorial to make a basic PCM. You really don't need any fancy lab equipment. This will be a fairly large quantity, which I will divide into multiple samples after mixing so that we have consistency between our tests.
From this finished PCM solution, I'll extract five 100ml samples. The first will have no additives as a control, and then I'll add 1, 5, 10, and 20g of lignosulfonate. The test will be to see if any of these reduce or hopefully prevent crystal sedimentation altogether. The final sample holders will be these plastic tubes, and we'll do several tests with these. First, I'll leave them upright to cool and solidify because that should easily reveal if we have any sedimentation at the bottom or even possible liquid separation effects at the top. Then, I'll place the tubes on a reptile heating pad, which I found is a really good way to stress test a PCM and see if it can resist growing large crystals after repeated cycling. We'll come back and take a look at how these tests turned out at the end of the video because, in the meantime, we have quite a bit more fiery chemistry to explore.
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Well, as I learned about DSS and lignosulfonate, I got curious about how these compounds are sulfonated to begin with, and it turns out that it's possible to sulfonate all sorts of things, like CMC or xanthan gum, which we used to thicken the original PCM recipe. I wonder how these might work compared to DSS if we added some sulfur groups onto these compounds. That might be possible to do by a variety of processes. The simplest being to use sulfuric acid. The problem is that sulfuric acid doesn't just add sulfur groups; it also breaks apart everything it touches along the way. We need something a little bit gentler in order to avoid destroying the molecules we're trying to modify.
I found a really neat reaction to make this happen by starting with sodium nitrite (that's NaNO2) and reacting this in water with sodium bisulfite to form a really strange compound which is just waiting to react with whatever it touches to stick its sulfate groups onto something else. It does this in slightly alkaline conditions, which means there's no strong acid to get in and break things. The problem now is that I need sodium nitrite to make this happen, and that is not an easy chemical to come by in the US. I'll need to make it myself, which is a notoriously difficult thing to do. In a state of ignorant bliss, I thought I could refine a process for making sodium nitrite during a single live stream for Patreon. Two hours later, and the only thing I learned was that I had a lot more work to do.
The basic method is to start with sodium nitrate (that's NaNO3) and knock one oxygen off to get nitrite. This can be done by mixing in just enough carbon to react with 1/3 of the oxygen available in the nitrate and then setting the mixture on fire, releasing CO2 gas and leaving behind NaNO2. Nope, not that easy. You will get some nitrite this way, but most of it will be decomposed by the heat, and what is left is heavily contaminated with unreacted nitrate, which is nearly impossible to remove. It helps to use starch as the carbon source because it makes for a colder reaction compared to pure carbon, but it's still tough to get right.
I then tried several other ways to make sodium nitrite, including decomposing nitrate directly just with heat alone, which was a fun experiment if only for the fact that dipping a matchstick into a molten pool of oxidizer is a really interesting thing to watch. The result of this experiment was very low purity, less than 10% nitrite, and not suitable for my experiment. I then started the process for yet another method using sodium sulfite to convert calcium chloride to calcium sulfite, which I would react with sodium nitrate to make calcium sulfate and sodium nitrite in a solid state. Ultimately, I went back to the starch reduction method, trying various ratios until I landed on one that gave the highest concentration of my desired product: 170g of sodium nitrate ground finely together with 60g of corn starch and then piled to one side of a stainless steel bowl can be heated with a torch until it reacts and beads up, falling into the bowl as a molten pool. This mixture is just slightly to the side of having too little fuel compared to the oxidizer for it to self-sustain a reaction, which makes it safer to work with and stops it from reacting as soon as I remove the torch. The result, once the molten pool cools off and becomes solid, is 35% sodium nitrite, 33% sodium nitrate, and 32% sodium carbonate by weight. I figured this all out with a series of titration reactions. I was hoping for a little bit more sodium carbonate because that's easier to remove from the nitrite by dissolving everything and letting the carbonate crystallize out. It's about 10 times less soluble than nitrite at low temperatures, but then it's another long and energy-intensive step to boil the water off again and dry the nitrite out. And after all the difficulty I had so far, I decided I should just grind this 35% nitrite product into a powder and try using it as is. It's probably good enough.
One final note about nitrite synthesis, maybe for my own future reference, is that I did succeed in making one sample which had basically no nitrate left in it, just nitrite and carbonate. This was the same 170 to 60g ratio with starch ball-milled for an hour before reacting. The results were 30% nitrite and 70% carbonate. If I ever need super pure nitrite, this would be the experiment I repeat, followed by several rounds of crystallization. Just like that, I have traded a week and a half of work for a few bags of one of the ingredients necessary to attempt a sulfination reaction, which itself may or may not work.
The papers which I'm referencing to learn about this reaction are frustratingly and intentionally vague. Someone explained to me, what is the point of publishing in a scientific journal if you intend to hide your methods? Why do you have to pay thousands of dollars to publish in a scientific journal? Why make the experiment public at all if you're going to hold back critical details like how much of the ingredients were used? It doesn't make sense to me. All right, I don't need to say any more on that. Moving on. Anyways, between these very frustrating articles and one expired patent from 1957, I was able to piece together enough information to give this reaction a try.
The stoichiometric ratio required between our two starting chemicals is 4.5g of sodium bisulfite for every 1g of sodium nitrite in order to form the final sulfonating compound in solution at 90°C. The needed concentration of these two chemicals in a given quantity of water is a mystery, as is how much CMC or xanthan gum or whatever else can be sulfonated by the random quantity of chemicals that I use. But I did learn that when it comes time to add whatever ingredient I'd like to sulfonate, the solution should be slightly alkaline, around pH 11, and then left to react at about 40°C for a mysterious length of time.
Now, before I start this reaction, I need to mention that more often than not, I try to make chemistry really accessible in my projects, but this reaction in particular has the potential to make some seriously scary byproducts, especially since the papers I'm following have an element of mystery that has required me to invent my own procedure. I have spent weeks researching all the different horribly carcinogenic and dangerous things that could happen if I add the wrong thing to this reaction or do things in the wrong order, even if I use the wrong quantity of ingredients. Don't mess around with this. I'm about to do a carefully planned experiment. This one is not a tutorial.
So I'll start by dissolving my starting ingredients: 3g of my 35% nitrite powder to equal just over 1g of the pure compound once it's in solution, and then 10g of bisulfite in a separate container. I'm using more than double the stoichiometric quantity of bisulfite here because three or four grams will be used up just in the process of reacting with all the extra carbonate that is a contaminant in my impure nitrite powder. Bisulfite forms sulfurous acid when mixed with water, and so once the acid has neutralized the alkalinity of the carbonate, I still need the bisulfite to be in excess in order to consume all of the nitrite. So we'll mix these two solutions together slowly and then turn on the hot plate to hit the 90°C reaction temp. This needs to sit for about an hour, and then we'll be ready to add whatever thing we'd like to stick some sulfur groups on.
Well, this has been going for a while. I think the first compound I'll try to sulfonate is CMC (carboxymethyl cellulose), which is a thickener that has already proven effective in some research to prevent crystal separation in PCMS. That's right, I forgot this video was about PCMS and thermal energy storage. The chemistry that I have had to learn for this step in the project has turned out to be a way more difficult task than I expected. By the way, I have a Patreon. If you think I might have earned your support by investigating this stuff, no pressure at all there, but I would certainly appreciate it.
For the final part of this reaction, I can turn off the heat and then I need to adjust the pH of this solution to about 11. I do that with a solution of sodium hydroxide. And I learned that the pH indicator in these universal test strips that you're probably familiar with is not compatible with something in this mixture of chemicals; they just never change color. The only pH indicator I have on hand which actually works in here is phenolphthalein. I really should learn how to pronounce this stuff. Anyway, this changes color to a bright pink at a pH between 8.3 and 10, which is close enough to the ideal range of this reaction that it should work. I'll add one or two drops of this indicator into the mixture and then we'll add in some sodium hydroxide solution until the color fully changes.
Finally, I can add 5g of CMC to this sulfating solution and hope that this is an appropriate quantity to fully react and absorb sulfonate groups all along the length of its polymer chains. Before adding this, however, there is no way that such a large quantity of CMC powder would mix properly in this small quantity of water without forming clumps. So first, I'll add just a little bit of rubbing alcohol to the CMC to pre-wet it and turn it into a paste, just 1 or 2 milliliters, enough to allow it to more easily disperse. Then I can pour it into the solution, and we'll let this react for, I guess, about 10 minutes while I figure out some way to separate the end product from all the other stuff in this mixture.
The one method that I've seen mentioned for separating large polymers like sulfonated CMC from smaller molecules like the salts that are left over in this reaction is dialysis. Dialysis as a medical procedure is basically removing small waste molecules from your body while leaving behind everything else that is above a certain size. You can do the same thing to separate chemicals in the lab by using a semi-permeable membrane, often a tube made out of cellophane. You fill this tube with the products of your chemical reaction, like a weird sausage, and put it into a bowl of deionized water. The small molecules can seep out into the water, but the larger polymer molecules stay trapped in the tube. After changing out the water several times over the course of a few days, all the salts get washed out, and the contents of the tube can be dried to collect the purified polymer. This is kind of a long process, which can go very wrong if the cheap dialysis tube I purchased off the internet springs a leak and I lose my product. 40 hours in.
We'll save this process as a last resort. First, I'd like to see if we can separate the CMC by a much faster technique, which we used in my previous video to separate DNA from strawberry juice. This involves chilling the polymer solution down to as cold a temperature as possible and then adding chilled isopropyl alcohol over top. This should form its own separate layer and hopefully cause the sulfonated CMC to precipitate at the boundary between the water and alcohol.
Well, this mixture has now had plenty of time to cool down, so I guess it's time to add the alcohol and see what happens. I really, really hope this works. Oh boy. Well, it didn't precipitate at the alcohol boundary, but after stirring, the CMC does seem to have solidified and is now floating around as solid chunks. If I stop the stirring, we should be able to pour the liquid off the top, and I'll refill it a few times with fresh alcohol to hopefully remove whatever is left of the water and other things contaminating our product.
Well, we have some sort of result here. It's currently drying suspended above my hot plate on a wire mesh with my fume extractor pulling away any extra solvent as it dries. I've washed this a few extra times in 91% alcohol to hopefully leave us with a fairly pure product. So how do I know if this worked? Presuming that I have washed this thoroughly enough, the only sulfonate groups left over in this powder should be chemically bound to the CMC, and if we dissolve a little bit of this into water, we should be able to test and find out if there's any sulfinate present by using a solution of calcium chloride. So when I drip this in, we should see a white powder form as the calcium reacts to make insoluble calcium sulfate. Hmmm. That is not as dramatic a reaction as I hoped for. That's not great. Um, maybe the sulfur groups are really strongly attached to the CMC or something. Uh, maybe that could prevent the calcium chloride from reacting with them. At minimum, this does tell me that the end product is fairly pure, because any sulfite salts that were remaining in this would have definitely reacted with calcium chloride.
Let me try something a little bit stronger. We'll make a solution of barium chloride. That's the standard test for sulfites, and uh, if there are any sulfites present in this, they should definitely react with barium. Okay, barium. Now. [Laughter] And that is what I was hoping to see. I think that we have been successful, and possibly the lack of reaction with calcium could suggest that we have made a really stable product that is so good. Oh man, the rest of this sample is definitely ready to test in a PCM. So we'll compare what we have of this sample, maybe not all of it, against an equal weight of untreated CMC in the same quantity of sodium sulfate PCM.
As I was doing this, I had another idea along the way, which was to try sodium citrate instead of table salt in one PCM sample, because citrate ions have similar electrostatic effects to regulate crystal growth as the sulfinate groups that we've been focused on for most of this video. This will be a bit of an oddball sample, which can't be directly compared to the others, but I'm interested to see what happens. And in the interest of leaving no stone unturned, I have repeated the entire sulfination process to produce samples of sulfonated xanthan gum and guar gum. We'll test these as well, bringing the total to five new potential additives to improve the performance of PCMS.
Now, the question is, do any of these additives actually offer a significant improvement? So let's take a look at the results of my first series of experiments using the lignosulfonate. Starting with the vertical cooldown test to inspect for sedimentation and liquid layer separation, and you can see that the control does not look good. Uh, lots of crystals on the bottom, basically nothing homogeneous about it. There was no thickener at all in this sample, so it is not unexpected for it to have done this badly. Actually, I need to fix a problem with all of these before I can get into the results properly.
The problem with these samples was something I had forgotten about when I decided not to add a thickener for this experiment. All of the samples had crystals on the bottom, and I know it's hard to tell on the darker ones, but they are there. The problem is supercooling, which a thickener would have helped to prevent. Basically, all of the samples cooled to way below their freezing point without actually freezing. You've probably seen the trick where you can do this with water to form little ice towers as you pour it out. Anyways, these PCMS can supercool way more easily than water, and if they get too cold before something actually triggers them to freeze, the salt just can't stay dissolved. There's too much of it, the water is too cold to hold onto it, and no additive could possibly prevent crystals under those circumstances.
To fix this problem, some gelling agents like CMC do help the solution to freeze at the right temperature, but you can also make this happen with dedicated nucleating agents that trigger the hydrated salt ice to start forming at the right temperature. It only takes one little speck to convert from liquid to ice phase to trigger the entire solution to rapidly freeze. So I added a nucleating agent to each sample after remelting them: that being 1g of borax. This is known to be a very effective additive to prevent supercooling in PCMS, but I've really tried to avoid using it because recently it's been banned in most of Europe, and I prefer to use things that are accessible to everyone. There are other alternatives, but in this case, borax was the quickest way I could think of to solve the supercooling issue so that our sulfonated additives can be tested under normal freeze-thaw conditions. So we'll let these samples cool back down, and then the results should be more telling.
So now we have a whole bunch of tests to look at. I have 12 total samples here. I made these two additional ones off-camera, and I'll talk about those last. So first, we have the five lignosulfonate samples that we started with. This one is unmodified, and then we have 1, 5, 10, and 20g of added lignosulfonate. Number two nucleated really quickly, and this was the clear winner out of these samples. The control looks slightly better than it did prior to the addition of borax. All the rest look roughly the same. Three through five performed pretty badly, five being the worst of them with the coarsest crystals and the most liquid at the top. Uh, three and four were not far behind in low performance; they just have a little bit softer crystallization on the bottom, which would make them perform slightly better in the long run, but they would still need agitation to re-homogenize the mixtures. Number two might have just gotten a little bit lucky at freezing early because the early triggering of a freeze cycle tends to stabilize any crystals that would form and keep them from falling out because suddenly the mixture is a lot thicker and they stay held in place. I don't know, really, what to say about these tests except that we'll find out more when we try the repeated cycling to see which one is the best.
So moving on to the top row, these three here are the samples which are modified with my homemade sulfonated compounds. We have sulfonated CMC, xanthan, and guar gum. Then here we have ordinary CMC. This is my failure of a sample using sodium citrate instead of salt. And then over here we have two samples I'll talk about at the end. So these three, the xanthan gum was the one that performed the best. This, in fact, was really well homogenized, well frozen, and it probably still is despite this top section now being in a molten state. The xanthan gum performed really well. The sulfonated CMC was a little slower to freeze, but it too is very soft, no hard crystals. However, before this one actually fully froze, something settled to the bottom of this, and so again, when this remelts, whatever is already at the bottom is going to stay more concentrated in that area unless we agitate it, and that might be an issue. The original CMC is well distributed, but the crystals are fairly large, some good and bad there. CMC is known to stabilize PCMS, but it also reduces their thermal capacity. Hopefully, that is reversed with the sulfonated compounds, and these should actually increase the thermal storage.
Now, these two samples are the ones that I'm most excited to try in the thermal cycling test because as I saw that these lignosulfonate samples down here were not doing so well and a lot of stuff was settling out of solution, I thought that perhaps this sort of detergent action which I was leaning on for this lignosulfonate just doesn't work on its own and it might require a little bit of additional thickening. And so I decided to combine the number three test down here, that's 5g of lignosulfonate, with the CMC test up here using 3g of CMC. So this is a stabilized lignosulfonate sample that froze really well. It's it's really homogeneous, hardly any liquid at the top, and I can't feel any hard crystals. And this is a better result than the standard CMC, and so something has improved about this. I I really am curious to see how this one is going to hold up after repeated cycles. And for this one, I've just doubled the amount of CMC. So this is actually thicker than any of the other tests. I can't really compare it directly to them, but if this is the top performer after repeated thermal cycles, it'll just tell me that any of the flaws in these three up here of my sulfonated samples could be corrected by just adding more of the thickening sulfonated ingredient.
So now let's move on to test the stability of all these samples under thermal cycling. And to do that, because they have de-homogenized many of them in this vertical position, I'll go ahead and remelt all of these samples, mix them around so that we have an even distribution of ingredients throughout the tube, because that series of tests will be conducted with all these tubes lying on their side.
Well, I am glad that I got this test set up when I did, because this is the first time that I've left my house in about four days. I got really sick, and I knew it was coming. Both my wife and my son were sick as I was filming that last section of the video. Since I've been inside for like four days, this test has had plenty of time to make these samples go through many hundreds of thermal cycles, just from the fluctuations in the room temperature and from the reptile heating pad, which is below these samples cycling on and off to maintain its temperature, which was set to 100°F. So what I'm looking for in the results is for any hard monocrystalline formations at the boundary layer between the molten section. So we have a molten section of the tube, which was what was on the reptile heating pad maintaining a warm temperature, and then we have the frozen section, which was overhanging the edge. What I want to do is just take a look at what are the top performers in this test. We won't look at all of these in detail because some of them were obviously pretty much failures, and and others seem to have have done quite well.
So starting with the lignosulfonate tests, three through five performed about the same as in the vertical cooldown tests. They never actually fully froze. You can see that there's bubbles moving around on this side of the sample, and um, there's very hard crystal structures inside. Not a great result. I think maybe what's happening at the very high concentrations of lignosulfonate is that the lignosulfonate is actually more attractive to the water that's in the sample than the sodium sulfate. So very high concentrations of lignosulfonate do not seem to be a benefit to the PCM. Number two, however, seems to have frozen in a fairly homogeneous um structure toward the cold end of the sample. This this is looking pretty good, pretty much how it did in the vertical cooldown test, and I think that it is looking better than the control. Um, the control has fairly large crystal structures. It's very hard at that boundary layer. That's to be expected with the control. We had a leak on number three, but since three through five didn't perform well anyway, I don't I don't think that's an issue. Get rid of that.
This test was more interesting. So this one has 3g of CMC, the same as our control right here, and this one did stay molten on this side and frozen on this one. Yeah, there are some crystals that have formed in here, but they're fairly soft and easy to break by hand, except for that one right there. I could probably poke a hole through this tube with that crystal. That is a really good result from this tube. We'll have to experiment more with this recipe and see if we can refine it a bit more.
Now, the guar gum actually froze this time. Wow. Okay, guys, this one is actually really soft. Oh man, that's so good. That is no crystal formation at all at that boundary layer. Wow. Okay, this needs some more testing because for some reason, the guar gum sample did not freeze in our vertical cooldown test, and I still have no idea why. But once it did freeze, it's just got such a soft texture, no rigid crystal formation whatsoever. This is maybe the best result that I have ever gotten stress testing PCMS, and I have made hundreds of PCM samples. Oh, this is exciting. This might be a breakthrough right here.
All right, let's move on and look at our other samples here. So the sulfonated xanthan gum, pretty rigid crystals in this one. I I think we can rule this one to be a failure. All right, the S CMC, sulfonated CMC, that's interesting. These crystals when I squeeze these feel like waxy. So at the boundary, there are no hard crystals on the sulfonated CMC, but it's kind of lumpy in the frozen section. Very weird. I don't know what to make of this test. It seems like a better result than the sulfonated xanthan gum, definitely a better result than the standard CMC. Here, the normal CMC, very crunchy. Let me bring it close to the microphone so you can hear the crunchiness of those crystals. Much larger crystals in this sulfonated CMC tube. And then, of course, we have the sodium citrate sample, which I'm not going to really talk about.
So the sulfonated guar gum sample, this might be something special. We need to work a little bit more on optimizing the sulfonated guar gum recipe, find out why it did not freeze in our vertical cooldown test, and then also this lignosulfonate sample which has CMC added to it. Both of these are very promising. Man, there is so much to explore with this.
So after all that, we are left with some really interesting results. I don't even know what to make of this guar gum sample. After a really weird failure in the vertical cooldown test, it went on to outperform every sample I've ever put through the reptile heating pad test, and I've done this hundreds of times. Either way, this one has my attention, and I'm going to do some more experiments to refine this recipe. No matter what the result of this experiment was going to reveal, the chemistry that I learned by this process was well worth my time, and we have just the surface of a whole new world of opportunities to discover new improvements to PCM thermal batteries. If you are not already subscribed, I think you will really enjoy the things that are coming next. Sometimes it requires a long and very messy process to finally land on the sort of beautifully simple solutions that I really love to make videos about. If you'd like to join in supporting my efforts for projects like this one, Patreon is the best way to do that. Again, no pressure to support there, but I would really appreciate it, and you can literally participate in the things that I'm working on by talking with me live and giving me feedback as I work whenever we do a Patreon live stream. I have some interesting new projects in the works that I'm really excited about. Thank you everyone so much for watching. I'll see you next time.