Episode Transcript
[00:00:00] Speaker A: Good day. Welcome to Lubrication Explained. And today I feel like we needed to do something special for this episode. So if you are in this industry and you ever have to explain what you do and you say you're a lubrication engineer, inevitably you're going to get some funny looks.
So I'm imagining, like, if you, if you've ever seen the meme of the rock with the, you know, a single eyebrow up, that's the kind of look that I tend to get and you have to explain yourself.
So as a special for episode 69, I think we should kind of lean into it, right, and just embrace, embrace the memes and embrace the jokes. And today we are going to be talking all things personal lubricants. And actually there's a huge amount of technology that goes into it. So it's one of these fields where, you know, you drill down into any kind of field and there are experts in these fields. And that's generally what I found with this podcast is, you know, pick any niche technology.
There is someone for whom that is a, an absolute labor of love. And it's been kind of like their, their life's work. Now, the guest today.
Mr. Well, Neil Cunningham, who is the CEO and founder of the center for Industrial Rheology.
And you might think, what's that got to do with personal lubrication? And we are about to find out. So, Neil, thank you so much for coming on the podcast.
[00:01:20] Speaker B: Fantastic. Thanks very much, Raf. Yeah, it's great to be here. Yeah, really interesting.
[00:01:23] Speaker A: Yeah, this will be good. So we're going to have some fun with this one. In fact, we are as of recording this. So it's going to be a little bit, I tend to record these a little bit out of order, but it's coming up on Valentine's Day. So I think it is super appropriate that we are discussing this topic. So straight off the bat, personal lubricants, obviously chemically very different from the standard lubricants that you'd find in something like a gearbox. And I should say that Neil is also familiar with the industrial side as well.
So the tribology lab obviously tests all kinds of materials.
What's. What, what are some fundamental differences? Right. You're obviously, I'm assuming that they're not going to be any, you know, crude oil based. There's no mineral slash synthetic divide here. You know, what kind of, what kind of, what kind of stuff we talking?
[00:02:13] Speaker B: Yeah, I think, I think the main thing really is that in terms of composition, most personal lubricants tend to be water based really. So, so they're aqueous. So they got some propylene glycol or some glycerin in there. You get some rheology modifiers in there to give certain textures and sensory characteristics really.
I know sensory doesn't, almost certainly doesn't come into your world. I should imagine so.
Yeah.
So primarily aqueous based, you get some silicone, silicone based products as well, really. But they, I, I think the market is, is pushing away from those really. So we're trying to keep it as on a natural.
[00:02:58] Speaker A: Yeah.
Is there a particular reason why silicon would be like. Obviously historically they've been made from silicone. Is there a, like a reason for that?
[00:03:08] Speaker B: Yeah, it's just there's been health concerns, safety concerns in the marketplace with silicones, not, not just in personal lubricant world, but in the cosmetics world for example, for, for quite a while now really. So I'm not too up on, on the, on the, the veracity of the health concerns there really. But, but you know, the market goes where the market goes, really.
[00:03:33] Speaker A: Yeah.
[00:03:33] Speaker B: And so yeah, there's heading more and more into aqueous products really.
[00:03:37] Speaker A: Okay. Yeah, interesting. And I mean, you know, the aqueous stuff, we do have some familiarity with that in, in our world obviously there's certain niche industrial applications that require some kind of water based, water based product. And, and as we know, water is not exactly a great lubricant. So you know, the addition of some of those modifiers is kind of what gives it its performance.
Speaking of which, you know, lubricants in, in our world, in the industrial world tend to have certain flow characteristics.
So what are the kind of characteristics that you'd see out of the personal lubricant world?
[00:04:13] Speaker B: Yeah. So how far do we want to get into this?
[00:04:17] Speaker A: Yeah, yeah.
[00:04:20] Speaker B: I mean you, first of all, you got, you've got to get the stuff out of the bottle. So it, you, you need to have, you've got to be able to squeeze something out of the bottle really. So it's got to be handleable really is, you've got to apply it, it's got to stay where it's put and, and then it needs to do its job really. So, so in terms of this, and this is really where we're talking rheology primarily initially really. And you're looking for something that's going to have, I mean most personal lubricants are typically significantly non Newtonian, so their viscosity will be depending on the shear conditions and the situation. They'll have some gel structure to them. They'll have some elasticity in there that contributes to the lubricating properties of the thing.
You don't want them stringy, you don't want them slimy.
They are, because of the nature of the product, they're exposed to the air a lot as well, really. And you don't want them drying out and getting tacky and sticky, really. So, yeah, yeah. So there's a. There's a bunch of stuff there.
[00:05:21] Speaker A: I've never asked anyone to subscribe on this channel. I'm not about to ask you to. What I am going to ask is if you find this helpful, could you please share it with a colleague who may not know anything about the channel? I've heard feedback that it's a really good resource and a really good way to instruct people that are new to the business. So if you know someone who would benefit from watching this channel and watching these videos, please share it. Yeah. Okay, so maybe we can drill down into a couple of those. So like, as an example, you mentioned, you mentioned, like, slimy, for example. Now that I think is a description that people can intuit, right? Like, we all know what something feels like when it's slimy. From a, from a, like a physical property standpoint, what would that be related to?
[00:06:03] Speaker B: Yeah, I mean, this is really interesting. And so in addition to personal lubricants, we get involved a lot with the measurement of foods and food and drink, really. So. And that's another situation where you really don't want slimy and slimy. If you think about what slimy is as a texture, slimy is where you have the inability to. I mean, let's think about something in your mouth. For example, imagine you have some raw egg white in your mouth.
So slimy. I know, pretty horrible. But slimy is the inability of your tongue to feel the texture of your palate.
So it's. So it's a surface separation there.
And, and this comes obviously into, into your world and into the tribal, logical world, really. So, so if you get something that's. If you have a material that separates surfaces so much that you cannot pick up the texture and you cannot feel the roughness and the, the asperities, really.
But you also have a lot of lubricity, so low viscosity, then that's a slimy. And the slimy sensation. So when you're getting into dialing up a specific texture, you might want. You're going to want to get just the right amount of Slimy in there, really. You've got just the right amount of surface separation there because you don't want a complete loss of feeling there, whether it's personal lubricants or something that's going in your mouth or whatever, really.
But equally, you don't want to go over the top, really. So. Yeah, yeah.
[00:07:38] Speaker A: Interesting.
That's kind of like a really. I find it fascinating to see how, like, actual physical properties sort of translate into something that we can feel for want of a better word. And then you also mentioned the non Newtonian properties. Right. So I think, you know, when most people think of it, they think of either shear thinning or shear thickening fluids. So, yeah, like, I don't know. The standard examples that are given are things like toothpaste and the, you know, oobleck, which is that combination of cornstarch and water.
So what property are we looking for in personal lubricants?
[00:08:12] Speaker B: Yeah, so typically, in terms of the rheology, what we're usually looking for there is, as I say, a certain amount of non Newtonian behavior so that you can just handle it. You can get it in your hand, first of all, really, and keep it there until you need to apply it somewhere. And.
Yeah, so a degree of non Newtonian shear thinning, really. So, but then that has to be, you know, that has to be just right, really. So I can certainly tell you we've had a number of very interesting conversations regarding shear fields and shear rate conditions and these kind of things, but. Yeah, yeah, a degree of non Newtonian basically looks after the handling side of things.
[00:08:56] Speaker A: Yeah, that's really interesting. Okay, so now we've got kind of like the rough physical properties of what's required out of one of these personal lubricants.
Maybe you can give us a feel for, like, how much do these need to be dialed in by the companies? Because in my conception, say, for example, in the industrial world, the reason why we're moving lubricant technology forward is often because there are changes to the machine design or there are changes to things like the surface texture or surface roughness of the way that gears are manufactured.
People, I mean, there's, there's evolution, but evolution is a pretty slow process. People are people and they've been having sex for hundreds of thousands of years. That aspect doesn't seem to have changed much. So where is the sort of like the development in terms of these, these lubricants?
[00:09:52] Speaker B: Yeah, yeah, so. So there's, there's a few things there that are driving it really so there is, we've got an aging population. An aging population. So an aging brings dryness with it. And so that's a big growth market for the personal lubricant world there really. So but you've also got just, just straightforward sort of sensory properties.
Getting those right. As I said, as I mentioned, stickiness and drying is a, is a downside really. So, so a lot of lubricant manufacturers are looking for formulations that can, can maintain a, a silky smooth feel for a long period of time really. So, so yeah, you're looking for something that's going to last a while really so you don't have to keep, you know, slapping, slapping more on really.
[00:10:45] Speaker A: So yeah, yeah, so, so when, when you're talking about that drying out. So with the water based lubricants, that's presumably the water, you know, disappearing whether it's absorbed into the body or you know, what have you. And so what is left is some of those rheology modifying.
I guess that, yeah, in a lot of cases there might be polymers or something like that which gives it sort of like that really tacky kind of feel to it. Could you please just explain? Because we often use the word tackiness, but I get the feeling that some people are not really like again, it's one of those things that they could probably sense when something is tacky but don't have a good definition for what tackiness is. Would you mind just like explaining what it is?
[00:11:28] Speaker B: Yes, I mean tacky and that. And tacky comes into all kinds of personal care products and cosmetics and things like sun care products and anything, anything you spread on your skin really. So, so in tacky we really, we're talking about adhesion. We're talking about, you know, two surfaces coming together and then there's an adhesion there. And as you're pulling away it's, it's, it's that force as you're pulling away there really.
So we would, you know, we typically measure tackiness with a, we will use a thing called a texture analyzer which will be, you know, two surfaces. You'll, you'll coat one of the surfaces in the lubricant or whatever process product it is.
Bring up, bring a, an upper surface, an upper probe down into contact with that under a defined force and then you'll pull away and you'll measure the peak pull off force. And very often you also measure the, the area under the force distance curve and that will give you a work of adhesion measurement there.
[00:12:22] Speaker A: Yeah, interesting. Okay. And I can Imagine why in like this scenario, why that would be like an undesirable, an undesirable property.
So another thing which would be kind of helpful to talk about as well is almost like the, the temperature performance. Right. So, you know, in industrial applications, you know, we're often having to manage a very wide temperature window, whether it's, you know, stuff in being used in kilns or, you know, sort of like the steel manufacturing industry. Now we're getting up to sort of the hundreds of degrees, right. Down to sort of like Arctic conditions, you know, wind turbines in Antarctic bases where you might be exposed to minus 50, presumably with personal lubricants. It's pretty narrow window, right?
[00:13:04] Speaker B: It is, it's a very narrow window really. So you, you know, you'll probably take the product off the shelf and it'll be Maybe sat at 20, 25 degrees, something like that. Celsius there.
Skin temperature is about 32 degrees. Internal temperature is 37 degrees. Really. So, so unless there's some, some real action going on. Yeah. You're not going to rise much above that. Not really. So.
Yeah, yeah. So fortunately that, that's a, that's a great thing really. You don't need to worry about the viscosity index for these things too much, really.
And, and cold cranking is not an issue, really.
Yeah.
[00:13:42] Speaker A: Yeah. That's so interesting. So, and is there such a thing? Like, we obviously have our viscosity grades. Right. So, you know, your ISO viscosity grades or things like, is there an equivalent like in the, in the lubricants world?
[00:13:57] Speaker B: There isn't really. No. And there's no standard. Yeah, yeah, yeah. And that's the, the good thing about my world really here is there's, there's far fewer standards really, for, for that. So. But I do think having the, the SAE grades would be quite an interesting 0w.
[00:14:18] Speaker A: I think that's a great branding opportunity for one of the brands to say like, this is a, this is a 15W40.
[00:14:25] Speaker B: Yeah.
[00:14:26] Speaker A: And actually on that kind of what if you had to kind of say, you know, approximately what is the viscosity of one of these? Like if you, if you were to measure it, say, do you have any idea of roughly where it would be?
[00:14:41] Speaker B: Now you got me. I mean, a low sheer, you're probably going to be talking of the order of a few, a few pascal seconds.
[00:14:49] Speaker A: Okay.
[00:14:49] Speaker B: Really? So, yeah, yeah, yeah. So yeah, that, that's going to drop down significantly. Really. That's probably going to drop by maybe a factor of 100 or so.
[00:14:58] Speaker A: Yeah. Okay, interesting. That's interesting. So, so very affected by the, the shear performance then.
[00:15:05] Speaker B: Yeah, absolutely. Yeah, yeah. And the other thing to bear in mind there is you've got a bunch of other stuff going on and that viscosity is going to be changing as it's drying, it's going to be changing. But you've also got bodily fluids getting involved as well there really. So, so there's going to be interactions there. There's a whole world that we get involved with what is known as muco adhesion, really. And this is where you get a lot of products, a lot of polymer related products, for example, will be adhesive and they'll form a synergistic gel with mucin and mucus.
So your body, you've got a whole bunch of mucous membranes in your body, whether it's your eyes and your nose or in the vagina. And there you're going to have a whole.
There are a lot of situations where you may want or you may not want these sort of muco adhesive interactions going on there really. And some of that is dialed in not so a little bit in the personal care, in the personal lubricant world, but certainly more in the pharmaceutical and medical devices world where maybe you want a cough sweet or something that's going to stay and coat the throat.
[00:16:13] Speaker A: So that kind of thing fascinates me because let's say, for example, in a test environment like you're doing, right, where you're trying, you need something that's extremely repeatable, right. You need to be able to, so that you can dial in the properties. You need a very repeatable test, which presumably means that you have some kind of synthetic mucus that you're able to add to these tests.
[00:16:38] Speaker B: Yeah, yeah.
[00:16:38] Speaker A: Is that correct?
[00:16:39] Speaker B: Yeah, yeah, there is. I mean the stand that's used in, in our world is actually is porcine gastric mucin. So, so it's pig stomach mucin, basically.
[00:16:50] Speaker A: Right.
[00:16:50] Speaker B: So.
And that's. Yeah, and that's, that's readily available and, and we will use that for a whole bunch of different things really. We'll typically, we'll take a, we'll make up a solution of that and we'll measure the rheology of that and then we'll measure the rheology of the product that we're working with and then you combine the two and you look to see if there's an unexpected increase in either the viscosity or what we call the elastic modulus, the measure of the gel structure. In there. Really. And if you get these sort of unexpected increase, that's a good indication that you've got this synergistic interaction and this muco adhesive thing going on.
[00:17:28] Speaker A: Yeah, that, that's fascinating. Okay, so.
Yeah, one. Okay, so one thing you mentioned was that sort of like concept of visco elasticity.
[00:17:40] Speaker B: Yeah.
[00:17:41] Speaker A: Could you please elaborate a little bit on what that is? Because I think that's not really a concept that we encounter so much in the industrial world.
[00:17:47] Speaker B: Yeah, certainly. So I think a really good example of it is you imagine you've got something like, you know, that, like the hand, the hand soaps.
[00:17:56] Speaker A: Yeah.
[00:17:56] Speaker B: Or you know, the pumpable product there. So there you've got a really good example of a viscoelastic liquid that you've got something that will, if you, if you tip it up, it will pour like honey, really. So it's acting like a liquid, but you can also wobble it. And it's got some bounce and some, some gel structure to it, really. So, and, and so you get in this product that depending on what you're doing to it, is either behaving when more like a liquid, when it's moving slowly, for example, or if you're wobbling it, you're pushing it into an elastic response there. Really.
So that specific version of viscoelasticity is what we call the timescale dependent viscoelastic response there.
And whenever you have any kind of linear polymer or maybe like a linear micellar structure forming in a product, then you can get that kind of behavior there. And so that's what gives you, gives you a lot of the sort of the viscoelastic handling properties of a lot of these products.
One interesting thing where that does also play out is that when you have these linear polymers in solution there, you're going to get an extensional behavior. You're going to get that stringing and that also contributes to the slimy feel there, really.
And that stringing there. When you get this something that can form into a filament here, that then does give you, that contributes to the surface separation that I was talking about. So if you could think about a really good example is you crack an egg and you have the egg hanging there, the snotty point, so to speak, really.
So you got that. That's called elastic strain hardening. That and the egg just hangs out and it will slowly, slowly extend.
So you've got this extension resistance there. Now that's a uniaxial extension resistance just on the one axis.
But when you've Got a squeeze flow situation.
You've got two surfaces that are coming together.
Then you've then got a biaxial extensional behavior going on. So you've got this, what's called planar extension or biaxial extension there. If you've got a product that resists that extension, like the egg white, that's also going to resist these surfaces coming together. You know, when you crack an egg in a bowl and you get a little bit of the eggshell in the bowl and you try and get your finger in to fish it out, you can't get hold of it.
[00:20:30] Speaker A: Yeah.
[00:20:30] Speaker B: And that's classic surface separation situation that's brought on by the rheology.
So it's not a tribal logical situation yet.
There's not that high speed movement going on there or the hydrodynamic lift going on there. You've got pure rheology that's holding these surfaces apart there. You've got this viscoelastic cushion there.
And so that same effect, that surface separation effect, that's the thing that we get, gives you the sensory properties or for personal lubricant or it can give you the. Just the right mouthfeel with you if you're making a low fat mayonnaise and that kind of thing. Really? Yeah, yeah.
[00:21:12] Speaker A: That is so interesting. Okay, so, all right. So I'm always trying to kind of, anytime. I'm always trying to sort of do a read across almost to the industrial world. Right.
So we've talked a little bit about the differences in, you know, composition, temperature, all that sort of stuff. I'm just trying to think of like, what is the equivalent in terms of a mechanical system to the kind of thing that the personal lubricants would have to measure up to.
[00:21:41] Speaker B: Yeah.
[00:21:42] Speaker A: And I mean, it's basically, I mean, I'm for want of a better word, kind of like an engine piston. Right. So it's like. And whenever I'm describing the relationship between, let's say, for example, piston rings and, you know, and, and the liner, you sort of saying, well, that's actually linear motion. So it would be actually similar to a linear guide maybe.
And now we're getting almost into the realm of, I mean, there are some metal working fluids, which is sort of that water base, but also have to be able to provide protection against that linear motion.
[00:22:20] Speaker B: Yeah.
[00:22:20] Speaker A: So.
[00:22:21] Speaker B: Yeah.
[00:22:21] Speaker A: Is that basically like the equivalent mechanical system that you're working with?
[00:22:26] Speaker B: I think it is, yeah. Yeah. I mean there's, there's not a lot of rotation going on there.
[00:22:30] Speaker A: Yeah.
Unless you're a particularly skilled practitioner.
[00:22:36] Speaker B: So. Yeah, I mean, I'd say it's a, it's a, it's a. Essentially it's a linear bearing, isn't it really? Yeah, yeah, yeah. And I mean, I think the piston ring thing is a. Yeah, you're bang on there really.
[00:22:47] Speaker A: When you're doing like testing, for example, in, in the lab, is that the kind of setup that you are basically applying to it?
[00:22:58] Speaker B: Yeah, we don't know. We don't use any kind of reciprocating thing, despite the fact that it is reciprocating motion typically.
So we're typically using rotational.
So we have a custom built kit that we put onto a rheometer. So we use a rheometer as the base unit.
We'll have a compliant lower surface, so typically silicone or a latex or a soft surface that simulates the skin. And then we'll have a three ball upper measuring system. So we're typically using three glass balls for that upper rotational system. So it's a three balls on plate geometry essentially there.
Bring those into contact, lubricate the surface with the product you're testing, bring those into contact under a defined load, and then we'll go through a range of sliding speeds and we'll generate a stravic curve from that.
[00:23:49] Speaker A: Yeah, okay. Yeah, that's interesting. So that's not really something that I had really thought about up until now. You're right when you say you had to have a compliant lower layer because you'll get def. I mean, the materials that we're working with are a lot softer than steel. So you would have situations where the material does kind of deform actually under load as well, right?
[00:24:16] Speaker B: Yeah, absolutely. Yeah, yeah, yeah. So you've got a lot of elasto hydrodynamic deformation going on there. Yeah, yeah.
[00:24:25] Speaker A: Okay. So that might actually kind of bring us into this concept of like the normal stress type measurements. So that's something we kind of talked with offline. And could you please maybe explain that concept? And if there is an analogy in the industrial world, that'd be great. But maybe it's something that's unique to you guys.
[00:24:46] Speaker B: Yeah, I think this is, I mean, I think this is a really interesting area. So when we measure, if we take a, if we take an elastic fluid, so we take something like a shower gel or something like that, really, we put it on a rheometer on a plate, plate system, and we shear across a range of shear rates. Then in addition to the stress that's resisting the flow there we get a normal stress. We get a stress that tries to push the plates of the rheometer apart so it's normal to the direction of shearing there.
So that normal stress measurement, that's something that we've been doing a lot for the personal lubricants and for anything else from sort of food products to ophthalmic lubricants for the eyes and, and various other products, really. And there's two interesting areas there. Number one is it predicts to a certain extent the extensional behavior, which is much more difficult to measure directly. So extensional viscosity really. But, but it helps predict that extensional behavior. And, and that can lead into the whole surface separation thing we're talking about.
But the other thing is that, and I've seen a couple of references to this in the mechanical lubricants, lubricant world is that that normal stress can.
It's, it's proposed that that normal stress can help create a separation of surfaces, maintain a separation of surfaces without the accompanying viscosity penalty that you would get if you're just ramping up the viscosity of the lubricant.
So, so I think that's a really interesting, really interesting area.
[00:26:28] Speaker A: Yeah, yeah, that's, that's fascinating. Okay, so. So there is potential application in industrial purely for surface separation purposes. It'd be interesting to see. Yeah.
So what are, what are the kind of components within a liquid that would give you that property?
[00:26:46] Speaker B: Yeah, so it's typically when you have a linear, A linear polymer and the creation of that effect is a result of. It's effectively a recoil effect of, of the straightening of the polymer. Yeah, yeah. So whenever you have any kind of linear polymers in, in solution.
Also I mentioned about the, the micellar things. We get. You get what are called worm like micelles in a lot of soap, like shower gels and these sort of things really. And the same kind of thing there, really. So when they're sheared, they stretch, but they generate a force that's trying to push these plates apart really. And, and that has a very real effect in personal lubricants and cosmetic products and skincare and all kinds of other things really.
As I say, I've seen a couple of references for where they could potentially be highly relevant for industrial lubricants.
[00:27:40] Speaker A: Yeah, that's super interesting. So maybe if we can kind of branch out a little bit because obviously this area of biotribology, for one of a better word is, is pretty broad. Right. So you would.
This is one of those things where you think that it's narrow, but then the more you think about it, the more broad it gets.
Because you've already mentioned a couple. Right. So let's say for example, lubricants for your eyes. So anyone who's like, I mean, I'm wearing contact lenses, I'm. I'm pretty much functionally blind. I can't even see the eye test without them.
So. So yeah, know, I'm very familiar with, you know, eye drops and you know, you've got different grades, right? Because there's those sort of like gel type ones that you have to kind of squeeze into your eye, you know, if your eyes are feeling really gritty versus just the drops you've got. Yeah, I can imagine all sorts of stuff around skin care. Right. So anything that's applied to the face or the, or the skin needs to have certain properties.
[00:28:39] Speaker B: Yeah.
[00:28:39] Speaker A: And then you mentioned even food and drink.
[00:28:41] Speaker B: Right?
[00:28:41] Speaker A: Right. So maybe if we just dive into one of those, let's say, let's say food and drink.
[00:28:47] Speaker B: Right.
[00:28:48] Speaker A: I think that's probably the one that people are going to be most.
That's the one that's kind of like the universal equalizer. Right. Everyone eats. Everyone eats and everyone drinks. So what are the kinds of things that you might be looking at in the food and beverage world?
[00:29:04] Speaker B: Yeah, so, right. There's a couple of really interesting areas there, really. So firstly the.
Anything where you're, let's say you're removing sugar or you're removing fat from a, from a product, not so much with drink really, but removing fat from a mayonnaise or whatever, you want to replace that with some gums that give you the same kind of mouthfeel, really.
But when you do that, you're really moving away from. So oil in a mayonnaise will, will enable the mayonnaise to operate very much in a boundary lubrication situation where your tongue can feel on the surface of the, you know, the palate, you've got the lubrication there, but it's very intimate contact there. As soon as you start removing the oil out of there and replacing that with gums, then you are going to get into the, potentially into the, into the fluid film lubrication and the hydrodynamic and the slimy, the slimy sort of area there really. So, so that's one particular particular area, but another area that I think is really interesting. We talked about, I talked about mucus and mucin.
So in your mouth you have a.
It's known as the salivary pellicle. It's the layer of saliva that coats your mouth all the time.
And the lubricating component in your saliva is mucin. So it's a, it's a protein, it's a molecule that's, that's present there.
It's a linear molecule and it gives you the lubricating effect through the surface separation and these sort of things.
There are many products that will trash that lubrication momentarily, really.
And a great example of that is something like a high tannin red wine.
So you have a sip of red wine and you'll get the dry, puckered mouthfeel for a while.
[00:30:56] Speaker A: I've heard it described. The best description I've had of it is not a word up.
[00:31:02] Speaker B: Yeah, absolutely. Yeah, yeah, yeah. And, and, and the technical term for that is astringency.
So, so astringency, one of the mechanisms of that astringency is it's the momentary loss of lubrication, of lubricity of the saliva. And what's happening there is that certain chemicals, you know, tannins in a wine, for example, or there are other products in maybe an espresso, coffee or something that are precipitating out the mucin molecules so that they're interacting with the mucin, mucin in your saliva, they're precipitating those molecules out and then subsequently they lose their lubricating ability. So your saliva loses lubricating ability. And that's how you get the dry, the dry, high friction pucker mouth. Really, it's a really interesting effect. And getting that right in the food and drink industry is critical really. In the drinking industry you want just the right amount of astringency, so you've got a bitter feel going on there, but not too much really.
In the food industry, a lot of plant based proteins are famously astringent there. And so a lot of companies will be looking at formulating products that can deal with that astringency and remove those kind of effects.
[00:32:27] Speaker A: So is that becoming a bigger and bigger, let's say, component of the industry? Because people are looking at, let's say for example, vegan substitutes for like, because you mentioned the difference between animal fats and something like a gel. So if you substitute, let's say an animal based product for plant based, it completely changes, let's say the mouth feel of and like the texture. And so you're, the work that you're trying to do is to iterate and find something which is as close to the feel of an animal based product. Is that.
[00:33:01] Speaker B: Yeah, yeah, absolutely. Yeah, yeah, yeah. So, you know, it could be, for example, a plant based milk where you are, you may have a component in there that is, that is bringing the astringent effect in there really. So that needs to be dealt with in some way, really. So. And it could be looking at the oils that are present in there really to counteract that. So.
And the other area there is when you, when you're looking at sort of alternatives to animal, you know, for example, meats and the major contribution to the succulents of a meat, so a burger or a juicy steak, a ribeye steak or something like that. Really big part of that is it's the oil in the mouth, it's the animal oil, the animal fats in your mouth and how they're behaving, particularly as that fat is cooling down, there'll be crystallization going on and various things really. But there's a certain profile to that, really a certain rheological profile ultimately to that.
And so for companies that are looking at replacing animal fats with for example, coconut oil, which is a commonly used one in a lot of plant based meats there, that's a real challenge really. So, because, because that whole temperature rheology profile is very different. There is a fascinating area.
[00:34:26] Speaker A: Yeah, yeah, that is fascinating. I mean, I've got a particular interest, so it just so happens. So my, my wife is a clinical speech pathologist and so she works with cancer patients who've had mouth and throat cancer and are receiving rehab.
And often because of, you know, tongue or jaw weakness, they're having to be on modified diets. And a lot of her job is to, to kind of basically match the consistency of the food and drink that they can manage with whatever strength that they have left in their jaw. Because, you know, if you give them certain textures, they'll choke.
[00:35:03] Speaker B: Yeah.
[00:35:03] Speaker A: And it's interesting because this is something that she intuits, right, she's not measuring the rheology of these products on a, on a per patient basis.
But this is kind of like the underlying explanation, explanations for, for everything that's going on.
[00:35:18] Speaker B: And I mean, and that is a really, I mean that whole, the whole area of dysphagia, diets and you know, foods that modifying food for somebody who has those dysphagia, you know, the swallowing difficulties, that's a really fascinating area really, because you've got to deal with a whole bunch of stuff there. You've got to deal with, you've got to slow the food down. I mean, your Wife would know this much better than I would, really. But, but you got to slow the food down so they control it more and make sure they're not aspirating it into the lungs.
You've got muco adhesion aspects to that. There could be, you know, products could be getting stuck in parts of the, parts of the mouth and parts of the throat there. Really?
So. Yeah, yeah. So it's a really fascinating area and there is a lot of work that's going on on the rheology side. And I'm not so much on the. Maybe on the tribality, I don't know, to deal with that. Really. Yeah, yeah. It's great though.
[00:36:12] Speaker A: Yeah, yeah, yeah. That's fascinating. Maybe we should, maybe we should talk offline about standardizing that kind of thing.
[00:36:17] Speaker B: Yeah, absolutely.
[00:36:19] Speaker A: Yeah. Yeah, that's, that's fascinating. One, one last thing that would be worth kind of touching on. I mean, something that you've mentioned in the past is this idea of like the oscillatory measure and, and how it relates to like wax crystallization. And so can you please help explain maybe exactly what you mean by that? Because again, when we, when we talk about wax formation in the industrial world, we're generally concerned with the pour point. So as stuff cools down, you get the formation of, of wax crystals in the oil, which substantially, you know, affects the viscosity behavior at low temperatures. That's primarily what we're concerned with. You're talking about a completely different mechanism.
[00:36:58] Speaker B: Yeah, yeah. So essentially an area that we've been getting into lately with industrial lubricants, and I'm really keen for us to pursue this is.
So there are a whole bunch of techniques in rheology that are known as oscillation techniques. So oscillatory testing what you're doing, rather than shearing a material in one direction only, such as you would do with a viscometer. So if you had like a Brookfield viscometer or this kind of thing, really. So rather than doing that, what you're doing is you're gently wobbling the sample and you're measuring the resistance to the deformation is what we call the modulus. And you're also measuring the bounce back ability, really. You're measuring the elastic response there. So, so what you can do with oscillation is an extremely gentle technique. And you can start off with an oil that's up in a, in a, you know, liquid condition and you can oscillate it and you can bring that temperature down.
And as you bring that temperature down and you start to identify crystallization and the interaction of crystals. Once you start getting interaction of crystals and you start getting this structure forming the oscillation, that the elasticity suddenly starts to appear there. So we're going from what we call a viscous dominant condition, more liquid than solid, into an elastic dominant condition. We start to get the formation of a network and the network of the network is like a three dimensional network that has a connectedness throughout it and that can maintain a stress, you apply stress to it, it's going to store some energy and it's going to bounce back again.
[00:38:33] Speaker A: So just real briefly, that, that 3D structure, is that what we would refer to as gelling?
[00:38:39] Speaker B: Yeah, absolutely, exactly that. Yeah, yeah.
So I think the, the beauty of the oscillatory test is that first of all these, these you've, you've got the bounce, you're directly measuring the bounce back ability, you're directly measuring the appearance of this elastic structure in the material.
With if you think about something like the scanning viscometer approach, you've got the viscometer running at pretty low speed, but it's still grinding its way against this structure that's trying to form as the crystallization is going on there. So it's destroying the structure you're trying to measure there. Whereas these oscillation tests, incredibly gentle, they're performed on a high performance rheometers that can apply super tiny little stresses and just identify the bounce back there. Really, it's really powerful tool and we've done some great stuff so far. Looking at oils and looking at wax appearance in oils and greases as well, looking at thermo rheological profiling of greases, I'm really keen to explore that further, really. So yeah, I'd be happy to have a chat with anybody about that, really.
I think there's a lot of opportunity there and it's a rapid test, it's a, you know, a couple of hours test is not something that lasts a weekend.
[00:40:00] Speaker A: For example, when you say there's a lot of opportunity. So what kind of like performance dimensions are you thinking?
[00:40:07] Speaker B: Yeah, well I'm thinking that you get, you can get a lot of nuance in the, in the thermo rheological profile. So you can identify different stages of crystal formation.
You can identify, you could impose for example stuff certain degrees of shear of various stages throughout that. So you could see the impact of a small amount of shear on the dynamics and the kinetics of that process there.
And, and yeah, and then subsequently you could use that for sort of rapid screening of maybe additives potential. Yeah, that sort of thing. Really? So aging or something? Yeah, yeah, I think there's something there. I don't know what, but I really want to explore it.
[00:40:51] Speaker A: Yeah. Area of discovery, which is like. Which is how most science happens, right? Like, it's. It's the, you know, the. The age old. What do you want to call it?
You know, when people say, oh, that. That's interesting. That's usually where the. The cool. The cool science happens. So.
[00:41:08] Speaker B: Yeah. Cool.
[00:41:08] Speaker A: Yeah. Awesome. Well, hey, Neil, like, this was like, just absolutely fascinating. I. I loved every minute of it.
You know, very, very on topic for. For both. Both Valentine's Day, episode 69, I think, you know, just. Just a fascinating insight and. And I think, like, you know, for me, just so interesting to delve into a completely different area of, you know, rheology, slash, you know, tribology, which is, you know, like an adjacent and connected field, but something that most of this audience doesn't really have a whole lot of exposure to, but at the same time using all the same concepts. And obviously your lab still deals in the industrial world as well, so. No, really appreciate kind of all the insight and. And just having fun with the topic.
Fantastic.
[00:41:56] Speaker B: That's great, Raf. We got to keep the couples together, keep them, keep the marriages happy.
Yeah. I was.
I was workshopping stuff that we could talk about with with Chatgpt over the last few days and. And. And Chatgpt actually suggested to me finish it off talking. You've got to talk about a happy ending.
[00:42:19] Speaker A: Well, there you go.
What a great way to finish with the happiest of endings. Cool.
Thanks so much, Neil. Hey, really, really appreciate it.
[00:42:29] Speaker B: Fantastic. That's great, Rafe. Thanks very much. Appreciate it.
