Why does vape testing in laboratory conditions often differ so much from real-world use, and what are the factors affecting overheating and the creation of unintended byproducts?? Joining us again to explore the complex physics and chemistry behind vaping is nuclear physicist and vaping advocate Roberto Sussman.
Transcription:
00:04 - 00:27
[Joanna Junak]
Hello and welcome. I'm Joanna Junak and in today's episode Roberto Sussman will explain to us the key factors that affect the vaping processes and the impact of temperature on its efficiency. Roberto, what physical factors determine whether vaping occurs under optimal conditions?
00:29 - 15:14
[Roberto Sussman]
That's an interesting thing and it is closely related to the thermal parameters, the thermal processes that make vaping run. For example, I mentioned the energy that you supply. Well, that's power. Power is energy divided by time. There is a time there also. There is a time scale, the time that vaping takes place, right? You push the button, See, when you wait, and I'm going to do the experiment, right? I was pushing, I was delivering energy as much as I was inhaling, right? So there is an energy, an amount of energy and a time. That's very important, and it gives you the supplied power, right? Okay? And you have the supplied power. Now, inhalation is a flow of air. It's airflow. Air is flowing. How do you measure flow? The volume of air by seconds. Like, for example, typically when you use a low-power device, you're doing like, I don't know, like 50 milliliters per second, right? When you are doing direct to long, you can do up to 200 or 300 milliliters per second, right? So here... you have the different rating style. First, the processes. The energy that is supplied is supplied in a given time, right? And it is powered. And then you need an airflow. The airflow will tell you how you are how you are evacuating or you are convecting this convection is an airflow. And this has to be synchronized. They have to be coordinated, right? So when you buy a device, the manufacturer in the instructions will tell you a recommended range for the device. Also, there is another issue, the resistance. See, resistance is important because essentially the total amount of energy will be very similar, the total amount of current, of electric current. if you deliver a lot of power, you need little resistance. And the resistance and power, they also play a role. But the important bit is that there is a range of power that is recommended by the manufacturer. See, for example, this one is recommended between 10 and 25. like wax, okay? So this means that you are going to supply this. The manufacturers never tell you how do they find that. because it is not the same, it depends also on the user inhalation. If I buff this one with low inhalation, it will be very different as if I buff it with direct to lung. But the manufacturers only tell you a range of power. And you never, and they never tell you how they find it. So my colleague, Sebastian Sulek, has been for a long time trying to explain how can you predict in the laboratory these ranges. The manufacturers never tell you. We suspect that what the manufacturers do, they take a sample of volunteers and ask them to vape at different power levels. And when the volunteer says, no, it's too hot, that's the top one. Or if it says, well, nothing comes out, that's the lowest one. So you can identify to end points of this power range. The lower one, when vapor is not generated, right? You feel nothing, right? And the top one, when somehow it is too hot, maybe too much vapor, maybe... Okay, so how do you test that? The idea, and that's an idea of Sebastian, was to be testing the device in a machine, increasing the rate of power, right? So you do 20 volts at, I don't know, 15 watts. Then you do another 20 pulse at 7, at 16, and so on, and you go on like this. And what you expect to see is that every increase of power will be a proportional increase of aerosol that you are forming, right? So if I deliver more power and all of these thermal processes, there's little residual energy, then I will get a certain micrograms of aerosol. Now, measuring aerosol is very complicated, so you use epoxy, the amount of liquid that was consumed. I write this one in a precision balance. I put it in the machine. The machine will profit. And I have, I don't know, 20 times less profit. So I write it again, and I see how much liquid was consumed, right? And this is a very good proxy to see how many milligrams of aerosol was generated, okay? Now, you plot them, the amount of, you expect that an increase, a small increase of power will produce a proportional increase of aerosol mass, or illiquid vaporized, right? And as long as you have this proportionality relation, The process, and we can prove that by thermodynamic allogamous, the process is running smoothly. with maximum efficiency, never 100%, but let's say 59, 60% efficiency, as long as you have this proportionality, this linear relation, right? What happens in the lower limit? No vapor is produced, no aerosol, too little power. What happens when you reach the upper limit? When you reach the upper limit, you are going to deliver more power, but not going to get more vapor or more aerosol. And this is the beginning of overheating, because the amount you need for vaporizing is a latent heat. It's a fixed heat. amount of energy that has to be absorbed. If you deliver more, that energy will not be used to vaporize. That extra energy, that extra energy will heat the liquid, will generate a little bit more vapor, but that vapor will condense back into the liquid, So, essentially, the amount of vapor that is produced, or the amount... I'm talking about several proxies here. The amount of liquid that is consumed or the mass of the aerosol that is generated will be the same, will more or less... So, the relation is no longer linear. The relation was a straight line, But after a certain power, it becomes a curve that is not growing. It's more, right? It's nonlinear. And it is, now, this, something, if you do this at the same time, in every sequence of power, in every 20, every 20 volts that you do it, 15, 16, et cetera. If you also measure the amount of byproducts, you can see that as long as you are in the optimal regime, you are in the part of the exponential that doesn't grow. The moment you go to overheating, it coincides with the triggering of the byproduct. This can be seen experimentally. This is not an idea, speculation, I believe, I think. No, this can be seen in the... So it is very important to remain in the optimal regime where the supplied power produces a proportional amount of aerosol, right? Once the supplied power is not increasing, the aerosol is not increasing proportionally, that means that a lot of energy is going to be residual, right? Because you are still having the cycle, but you have too much energy that will stay there. that would create a lot of problems. But also the reactions are going to, because the current temperature at that point, that's another issue. As long as you are in the optimal regime, the coil temperature coincides with the boiling temperature, more or less, roughly, because the coil is in the wick. Vaporization takes place in the wick. It is a small region, and the wick and the liquid at that small region are more or less in thermal equilibrium, same temperature, right? But what happens when you supply too much energy above the the optimal regime, that means the coil will get a lot of energy that was used to rubber will stay in the coil, and the coil temperature will go up. we go above the... And so the vapor that is being produced is in contact with a very hot coil. And this means that the reactions trigger. You get the exponential part of the reaction, they trigger. And, okay, so this is what happens. This is how you determine the optimal regime. Now, the optimal regime gives you a power range. You know that between a minimal and a maximal power, things are going to be okay. But this range can be modified if you modify the mixture. But what I'm saying is valid for every mixture, every coil, And because it also depends on the coil or alloy, and also depends on the mixture, and it also depends on the airflow, right? So this is why to set up, to tell somebody, if you have to wave between 10 and 25 watts, you have to know how the person is inhaling. You make assumptions about that. Because if a person is inhaling very hard, then the person can vape in larger volumes, in larger powers. If the person is vaping very, very tiny, not much airflow, then the power ranges are narrower. So we believe that manufacturers simply take an average, right? But the optimal regime depends on how you weigh, depends on your equipment, and depends also on the eliquid mixture. But this can be regulated. I'm sure that this can be classified. You cannot classify every single issue, every single parameter. but you can have a network of parameters that can serve you and this is in the experimental part of looking at the optimal functioning of the vapor is as I described and it can be done in a laboratory.
15:14 - 15:19
[Joanna Junak]
And what is the difference between underheating and overheating in vaping?
15:20 - 25:31
[Roberto Sussman]
But underheating is when you supply, you do not supply sufficient energy to generate the thermal cycle, right? No vapor is produced. And if no vapor is produced, no aerosol, because aerosol is condensation of the vapor, right? That's very easy. Normally it doesn't happen, right? Now, overheating is when you supply too much energy to the coil. What happens is that this extra energy will not be used to vaporize the liquid, to generate vapor. Because to generate vapor, you absorb a fixed amount of energy at a fixed temperature, the boiling temperature. If you put more energy, that energy will not be used to vaporize. will be used to heat the coil, to heat the liquid, to heat the air that is in the atomizer, the walls, and so on. And also, a lot of byproducts will be generated. And the fact that a lot of byproducts are generated is felt by the user because it will modify the chemistry of the aerosol. And also, more important is the temperature goes to, let's say, to 300, 350 degrees. Remember, the top temperature has to be 288. If you are already 300, then you have reactions with the wick. The wick is made by organic matter. The wick is organic matter. It's made by cellulose. And so if the gas, if the wick is in contact with the coil that is at 350 degrees, you will have reactions that affect the wick. And these are more complicated reactions than the reactions that involve only the solvents in gaseous form, right? the user will suddenly feel a deterioration of the taste. The user will also feel that it is hot, because a lot of energy will be used to heat the walls, to heat the mouthpiece, etc., but Then the moment the week starts being pyrolyzed, there's pyrolysis in the week at 350 degrees, then it starts, the taste really deteriorates. And of course, if you keep increasing the temperature, you will, and that also requires a special explanation. How do you get from overheating to the dry puff. The dry puff is the end product, but you can get already a deterioration of the taste when the liquid is still there, right? Only when the liquid depletes, you have the dry puff. However, okay, these are, but what I'm trying to say is that the dry puff is not an isolated event in the sense, oh, everything was fine. Suddenly the liquid, it depleted back. No, it's not like that. It is a process. It can be very fast. It gives you the impression that it's instantaneous, but it's not instantaneous. And once the wick becomes feralized, the taste is completely degenerated. You feel a taste like burnt almonds. But burnt almonds can be identified with compounds called furans. And furans can be produced when the wick starts to feralize. So this is what happens in overheating. Overheating is... Now, I insist that users detect it. A user knows nothing about chemistry or physics or pyrolysis or blah, blah. Doesn't know that. But the user will feel it. if there is an overheating situation. And it can happen, in several ways it can happen, that the user does not know. For example, one way when you can have certainly secure overheating is if you take a very powerful device that should be operated at, say, 50 watts, and you power it with a very tiny emulation. See, if you take a Joule, for example, this is a very small, very low power device. To power this device, you need only a very small airflow. You don't need to, the suction is very, very low. If instead of this or a low-powered device, you have a powerful monster, and you puff it the same way as you would puff a small-powered device, you burn yourself. Why? Because the coil will produce, you are supplying a lot of energy, 50 watts. And so you are vaporizing a lot of liquid. But you need to do the cycle efficiently, you have to evacuate this liquid efficiently. So you need a large air flow and intense inhalation. If you do an intense inhalation, then you evacuate it and you keep the cycle with very little residual energy. Now, if you don't, if you do not evacuate this vapor with sufficiently strong inhalation, you will leave a lot of hot vapor there. And that hot vapor, so a user will not do that. But a machine, a machine doesn't care. So one of the ways that you can produce very easily overheating conditions and a lot, a lot of byproducts, of toxic byproducts, is by putting very powerful devices in your machine with very tiny air flows. A human would not do that. At the first thought, the human would say, no, no, no. But the machine, machines go on. And this is a very typical, the most frequent way in which you can artificially produce in the laboratory overheated aerosols that are very toxic. These are very toxic. And so you take this aerosol and you put it to the cells or to mice and the mice will get sick and the cells will die and so on. And then you say raping is bad. But no, it is a bad experiment. This is a very common way. There are other ways. For example, if the puffing machine puffs too frequently, And I can talk about that maybe in another session, all the experimental problems. But normally, I insist, go back to the beginning. The user is able to tell when the vape, when the electronic cigarette or the vape is not working properly. You feel it. And that means that you are either not buffing it the way it should, maybe, The coil is already worn down. Maybe your liquid is depleting too much. All of these are related to these problems. Why the liquid depletes very fast? Because excessive residual heat will heat the liquid, the bulk of the liquid. And this will change the viscosity, and this will change the capillarity. But you will not produce too much vapor, but the liquid will decrease. It is all connected to these thermal processes, but the user doesn't know anything about it. The user just feels it.
25:34 - 25:39
[Joanna Junak]
Stay tuned for the next part of our science series coming in a couple of weeks.