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학습트랜스크립트
00:00다음 chapter입니다.
00:06Characteristics, Applications, and Processing of Polymers
00:10For the previous weeks,
00:14we learned about some organic molecules
00:17and then corresponding polymer synthesis.
00:22Today we are talking about some issues here.
00:28What are the tensile properties of polymers?
00:32Tensile properties.
00:34Remember this?
00:36In the old chapters we were talking about some young modulus
00:41and then we give some stress
00:44and then the metal, the solid structure will extend their volume
00:53in the parallel direction to the force.
00:57That was like a tensile force.
01:01At that time we were learning about some stress
01:05and then strain
01:07and also some yield strength
01:11and what else?
01:13Tensile strength.
01:15Tensile strength.
01:17That was quite important for the many metallic or any kinds of materials for the mechanical purpose.
01:31And then here, the polymers and how are they affected by basic, the microstructural features we will see in the next slide.
01:47Then hardening and anisotropy and anisotropy and annealing in polymers.
01:53So this is quite interesting because you know polymers do not survive at high temperature.
02:01I don't know. I mentioned this one.
02:03You know like many organic compounds.
02:07Most of them organic compounds are starting to degrade with like over 100 or some 150 degree Celsius.
02:21That's why we don't use any plastic bowl for our food container.
02:31Because we use a lot of high temperature to cook the food, right?
02:39So here they are saying like annealing process for polymers.
02:43What are they doing?
02:45And how does the elevated temperature?
02:47So like when we're talking about some temperature
02:51and mechanical response of polymers compared to ceramics and metals.
02:55And then this temperature is also related to some creep
03:01and other mechanical properties in the previous chapters.
03:07I think you remember all those terms.
03:11What are the primary polymer processing methods?
03:15This will be discussed in the next recording.
03:21So based on this, we are talking about some polymers which is quite different from metal or ceramic
03:31which we already have learned so far.
03:35But you know like polymers are everywhere.
03:39From packaging films and fibers to electronics and medical devices and the structural components.
03:47You know wherever we go.
03:49Just around me, I can see a lot of plastic.
03:53Just many things.
03:54You know this computer is also cased by the plastic material and almost everything around my clothes.
04:06And I'm wearing glasses but this glass is also prepared by plastic.
04:12So they are everywhere.
04:14So they are everywhere.
04:16Their appeal comes from low density and tunable properties and the cost effective processing.
04:26So in this lecture, we will connect all the macroscopic stress strain behavior to molecular mechanisms.
04:38I don't think we will go very detailed for the real mechanism.
04:44When we talk about the mechanism, that's like how the molecules are moving from one side to the other.
04:50So in metal or ceramics, any kind of elements or atoms can move from one side to the other.
04:58But in this case, we don't go that far.
05:02We do not even observe any chemical structure for polymers.
05:08So in this lecture, we will connect that macroscopic stress strain behavior to molecular mechanisms.
05:22And show how temperature and time reshape performance.
05:28And then cover how polymers are formed and modified and processed.
05:36The central message is that the polymer properties depend strongly on chain architecture, crystallinity,
05:46and cross-linking, temperature, and strain rate, and process history.
05:52Here, the crystallinity is quite important.
05:56The word crystallinity.
05:59You know, when we talk about some crystallinity, that's, you know, like, what is that, like a crystal clear,
06:09or a crystal should be very organized and ordered structure.
06:16But you know, like a polymer is the ordered organic molecule.
06:21Although we learned about some crystal structure for the organic materials in the previous chapter,
06:31they are like the local one, and then it's not like a fully organized for the whole material structure.
06:41So when we say like the crystallinity, we are not talking about the whole material is crystallized or the crystallinity of the whole material.
06:57We will see that one soon.
07:01Here, mechanical properties of polymers and stress-strain behavior.
07:06Let's see, like this is strain, and this is stress.
07:10You know that, like when we give some stress, the polymer will extend.
07:18Do you remember that, like a yield strength, that the tensile strength can be determined by some strain recovery.
07:32That recovery is greater than 0.002 or something?
07:39Is it correct?
07:40If it's greater than this, that's the critical point for some stress change.
07:49And here, so we give the high stress, and then some polymer will expand their volume or length.
08:02And then here, brittle polymer, you know what the brittle means.
08:07It's the easily broken, and it's like a bottled shape one.
08:14When you drop the bottle, and it falls down to the floor, and then when it break down, the many pieces, right?
08:24That's brittle.
08:25See, they do not extend their volume that much.
08:32They just increase the stress, and then just the failure occurs.
08:38But here, it's quite important, because for brittle polymer, they can go up to 60 MPa, while other plastic cannot go that far.
08:51So, that's quite the interesting characteristics for the polymers.
08:58For example, like a brittle polymer, or the plastic and elastomer.
09:05You know, in the polymer one, when we say plastic, that's kind of like a permanent.
09:12Correct?
09:13Permanent.
09:14And elastomer is kind of like, what is that?
09:21So, it's elastic.
09:25Elastomer, elastic, and then it can go and come back to the original position.
09:33So, it's strain is, at certain stress, that strain is increasing.
09:45It's not like this one.
09:47In this case, elastomer, we will see this one case by case.
09:52So, the polymers exhibit these three different kinds of tensile response.
09:58The first one is brittle polymer, that elastically and fractured only with low elongation.
10:07And second one, plastic polymers, usually semi-crystalline thermoplastic.
10:13Semi-crystalline thermoplastic.
10:23And then, the elastomers display large recoverable strains and low stress, like rubber.
10:33So, this is the rubber.
10:38We will see each cases.
10:40Okay?
10:41Keep these curves in mind.
10:42They guide the mechanisms we will discuss next.
10:46Okay.
10:47The mechanism of deformation.
10:51Brittle, cross-linked, and network polymers.
10:54In the previous slides, I showed you there are three types.
10:59A, B, C.
11:01And then, let's take a look at the first case.
11:04That's A.
11:05Cross-linked, brittle, and cross-linked, and network polymers.
11:10Close-linked, and network polymers such as thermosets, thermosets, thermoplastics and thermosets,
11:20resist chain sliding because covalent links tie the network together.
11:25We will see how it works for each here.
11:31Remember this, like the old polymers can have the cross-links.
11:38If they have a lot of cross-links, that's thermal, not thermoplastics.
11:44It's a thermoset.
11:45Once it's set, that's set.
11:48We cannot modify it that much.
11:51So, this is kind of a brittle case.
11:59And then, let's see what's happening when we increase the stress.
12:06See?
12:07Neophilia.
12:08So, their length is changed because we are giving tensile stress this way.
12:20You should remember what tensile stress is.
12:24We give the force up and down, that's not compressing the other way, like pulling up and down.
12:35That's tensile stress.
12:39Then, we can easily guess this gap will be decreased.
12:49They are imposed and superposed to each other.
12:56So, maybe this distance is decreased, right?
13:07That's what happens for the polymers.
13:10That happens to the metallic compound too, right?
13:13But in that case, we see some crystal, the plane, the whole plane is moving.
13:26But in this case, we do not talk about some crystallinity yet.
13:31We just, like, the carbon chains are elongated.
13:37They are forced to move some directions.
13:44And then, let's see what's happening.
13:47And also, the plastic failure, we will see.
13:50This is also network polymer.
13:54I'm sorry.
13:55And then, for the brittle failure.
13:59I'm sorry, we are not talking about the plastic failure yet.
14:02Initially, we have network polymer.
14:05But that's the same way, right?
14:08The near failure.
14:10And then, obviously, this distance.
14:18is decreasing.
14:21A is B.
14:25I'm sorry.
14:26It could be just small changes.
14:31So, I think that's what's happening.
14:35So, and then, once the stress is concentrates at flaws,
14:43we don't see flaws yet.
14:46But once it's deconcentrated at some flaws, bones at crack tips break,
14:53and leaving little opportunity for plastic flow.
14:57The result is relatively high stiffness,
15:01but low ductility and failure is abrupt once cracking begins.
15:07Okay, and then, the plastic polymers.
15:12We will see the plastic polymer.
15:16There are a lot of pictures to see.
15:22Let's take a look at it.
15:24So, we are talking about some thermoplastic, not thermosets.
15:31In the previous case, we talked about some brittle failure.
15:36But most plastic has this kind of internal structure that was given in the previous chapter.
15:45And here, this is crystal region and crystallinity.
15:50And then, this is called also some, what is that, like chain.
15:57Chain molecule or some chain coil.
16:02A lot of words are like representing this kind of the place.
16:07That's amorphous one.
16:09Okay.
16:10And then, the, once we have, we force up and down,
16:17then we will see what's happening.
16:19And then next slide show.
16:21So, this amorphous region elongate first.
16:26So, that chain coils are like extending their volume.
16:31So, but still, we don't see any changes.
16:34This crystallinity region, that local parts are still as they are.
16:42That's, that's here.
16:45Then, let's see what's happening to the next part.
16:49Once we have, like the, the, but that's, that's quite important part here also.
16:56Then we give some stress, but we don't have to give any stress to make them elongate.
17:05So, we don't need any further stress.
17:08In the previous, like a brittle failure, we have to give more force to break down.
17:14But in this case, we don't have to give like a further force.
17:18In that case, you know, like this amorphous parts are fully extended.
17:25Then what's going to happen next?
17:29But these parts are already like, have done all can, all they can do.
17:36So now it's time to do, um, it's, it's time to do something for this crystallinity part, I guess.
17:47So next time, see this crystallinity, they are like some, the, what is that, the crystal plane-like.
17:56And then the plane or crystal structures are deformed, the block segments separate.
18:03That's happening, but they, they, they, they represent this way for the one.
18:12And then finally, the fibrilla structure, like a fibrilla.
18:18It's, it's, it's like some fibrilla.
18:21And then they are like, oh, they connected through this, the amorphous, the coil.
18:32Do you see big difference between metal case and this polymer case?
18:37So, um, you know, in the case of polymer, uh, I'm sorry.
18:43In the case of like a metal, we observed some, the, the failure when we do this, like a necking occurs.
18:53And then just one side is like, just one part or just one meeting part is like breaking down.
19:02But here we don't see any, the single neck.
19:07So, uh, unlike metals, in the case of polymers, deformation is not like confined to a single neck.
19:16The orientation stabilizes the neck and lets it advance a little bit.
19:22Okay, and then, uh, the pre deformation by drawing, that's tensile, right?
19:34Drawing is a intentional stretching, but that's obvious, right?
19:39We, we just give the tensile force to, uh, up and down.
19:44So, um, the drawing here.
19:49Monofilament, uh, filament, uh, filament, uh, fish line.
19:54Stretch is the polymer prior to use.
19:58I, I don't know what like this use means.
20:02Um, the, um, the, its actual purpose is a different way.
20:11And then we just, the, the, the stretch is the polymer.
20:15The, and then that can be used for some other, uh, purpose.
20:20You know, most likely we just prevent this kind of drawing after the, after that, that plastic is already formed for, for some kind of service.
20:37Okay, with this drawing, the properties become anisotropic.
20:42That's quite important.
20:44Aligns the chains in the stretching direction, right?
20:47That direction, that means it's anisotropic.
20:50Isotropic means the, uh, the older direction have the same properties.
20:56But, you know, the, if we do this drawing, the, the crystallinity is aligned to the same direction.
21:05So, it's this direction and this direction.
21:09They have totally different, uh, the properties.
21:13So, uh, result of this drawing, then increases the elastic modulus in the stretching direction.
21:21Um, that's quite interesting, right?
21:24The, and then tensile strength in the, the stretching direction.
21:28Because they don't move that much.
21:30And then it showed quite, and the, the strong force to that direction.
21:38But decreased ductility.
21:40I hope you remember this, uh, the percent EL.
21:44The original distance.
21:46And then the original distance.
21:49And, uh, extended one and, uh, times 100, right?
21:53And, and also they do some annealing process after drawing.
22:00Doing this kind of a process.
22:02And then the, some heat treatment.
22:05That heat treatment does not mean, like, uh, over 200 or something.
22:10In the, in the metal case, we talked about the quite high temperature for annealing.
22:16And then, for phase diagram, we just watched it over, like, 700 or 800, almost 1,000 degree Celsius.
22:24But here, the, for annealing after drawing, that means only the, less than 100 degree or around.
22:33So, uh, the, they also do some annealing process.
22:40Increasing some temperature.
22:41Then, the decreased chain alignment.
22:44Then, uh, reverse effect of drawing.
22:48Reduces E and, uh, enhances the, but no, that's what, uh, people observed after the annealing process.
22:57And they, normally, the annealing process gives some, the molecular rearrangement, right?
23:06So, due to their, like, van der Waals force, they might recover to, um, their original position a little bit.
23:16And contrast to effects of cold working in metals.
23:23That, the, um, you know, like, uh, some, we do, uh, the metallic compound to get their original place.
23:37And then, we do, uh, lower the temperature to sit their molecular elements on, on their, uh, side.
23:45But in this case, we increase a little bit temperature to do the same thing.
23:51Okay.
23:56And then, mechanism of deformation, elastomers.
24:00So, the third one.
24:02The elastomers, uh, elastity is largely entropic.
24:07In the unloaded state, chains are coiled, like this.
24:14Um, this is quite confusing to many students.
24:20Because, you know, they also have a lot of cross-link.
24:24But in, in the previous slide, when we mentioned about that cross-link, that's the summer sets.
24:31And then, normally, they do not elongate, right?
24:35But here, we also see some chains.
24:39But the, most of the chains are quite long enough to coil or surround the inside.
24:51So, in the unloaded state, the chains are, like, coiled and kinked.
24:56And lightly cross-linked, that's important word.
25:00Like, lightly.
25:03Lightly cross-linked.
25:08Then, how do we know it's lightly cross-linked or fully cross-linked?
25:13So, we have to check this kind of, uh, the, uh, stress and strain graph to determine that, the, the elastomer or brittle.
25:26So, uh, the, when, uh, stretched, chains uncoiled and, on, on, on the, here, they should have it this way.
25:36So, uh, you know, if we take a look at this, this picture, that looks like a starting point of brittle anti-failure, all right?
25:47The brittle, the polymer.
25:49So, the, uh, the chains recoil to high entropy configuration.
25:57This gives large reversible strain at low stresses.
26:02So, when we remove that stress, this, this, uh, the, this figure can go back to the original one.
26:17So, um, but this one, like, this behavior strongly depend on temperature and strain rate, the other glass transition.
26:27That's gonna be, um, explained in the, in the next slides.
26:32Okay.
26:35So, we just learned about some thermoplastic and, uh, thermosets.
26:40The, uh, thermoplastics have a linear or branched one.
26:46The, here, thermoplastic.
26:49Little cross-linking, ductile, and soften with heating, polyethylene, polypropylene, polycarbonate, and polystyrene.
26:59Um, um, the, some people believe, like, uh, polystyrene is quite, like, tough and, uh, the hard material.
27:10We also learned in the previous slide, some copolymer.
27:15Polystyrene and poly, like, uh, what is that?
27:18Butadian.
27:19Butadian is quite soft and then polystyrene is much tougher.
27:24So, uh, when we do some copolymer synthesis, then their characteristics are quite mixed.
27:34And then they can be used for the, the car tires.
27:38That's what we learned in the previous chapter.
27:41Uh, but still it's, uh, it's considered as a thermal plastic.
27:49So, here they are seeing some, uh, when we increase the, the temperature and then molecular weight,
27:57and, uh, the crystalline solid and partially crystalline solid, the high molecular weight,
28:03they have too much volume to be organized.
28:07And then the glass transition and, uh, the melting transition occurs and, uh, at high temperature.
28:16So, low, low molecular weight can, uh, when we increase the temperature,
28:23that glass, uh, over the glass temperature,
28:26then it may become, like, a viscous liquid.
28:30And then over, like, the melting temperature, then the viscous liquid.
28:36So, what's the main difference between them?
28:41So, we will see the, we will see them soon.
28:46And, uh, the, here we already observed that, like, a thermal plastic part.
28:54And then let's take a look at the thermal sets.
28:57Thermal sets are highly cross-linked.
29:00Little cross-linking and, uh, significant cross-linking.
29:05You know, the, if we have a small amount of cross-linking,
29:10that's enough to hold them, hold them enough, hold the, each, the lines.
29:17But if we have too much, all of the lines are, like, connected.
29:22So, it's very difficult to, uh, stretch it.
29:26They don't melt, and, uh, but degrade at high temperature.
29:32They are dimensionally stable and open, steep and brittle.
29:37Some of that, hard and brittle.
29:39Do not soften with heating.
29:42Do you, do you, um, have any example for this?
29:46For example, uh, you know, when you,
29:50you, most plastic we observe around us,
29:54if we increase the temperature, they just melt away.
29:58But, uh, not melt away, melt, melt down.
30:02I'm sorry.
30:03But some of the plastic, for example,
30:05the, what is said, that white styrofoam box.
30:09The, we also observed, that's quite serious, the material,
30:17when the fire occurs.
30:19In the, in the construction, or any, the local company,
30:26when they have that, the thermostat plastic inside,
30:32they generate a lot of the bad, the smoke,
30:37and also, they do not melt down.
30:40That's why it's very difficult to control the thermostat,
30:45the thermostat polymers.
30:49But this day, you know, they can be regenerated.
30:53So, um, maybe this, this guideline could be a little bit,
30:59uh, should be changed.
31:01Like, um, do not soften with heating.
31:05Sometimes they, they soften with heating,
31:09but we have to do some treatment.
31:11So, like, um, do, should be changed to,
31:14maybe, like, may not soften.
31:22So, uh, choosing between them depends on needed temperature resistance,
31:32and toughness, and, uh, reshaping requirements.
31:37What, what kind of properties we need for that, uh, the plastic.
31:44Where do we use?
31:47Okay, and then let's move to the influence of temperature
31:52and the strain rate on thermoplastic.
31:56This is thermoplastic.
31:58Plots for semi-crystalline PMMA.
32:01Uh, the, the product name is some plexiglass.
32:06Uh, they put, like, glass means they are quite transparent.
32:12And then, um, that polymethyl metacrylate is very famous for,
32:19like, a very transparent material.
32:22You know, when you, uh, buy, purchase, any,
32:25some, the local, the tour place,
32:29some, the souvenir products,
32:33then they have some case,
32:36which is quite transparent inside.
32:38You can see some, um, represent, uh,
32:42that area representing the figures inside, right?
32:48Then that's PMMA, most likely.
32:51And when we decrease, uh, temperature,
32:55then we also observe the increasing the young modulus
33:00and increases tensile strength
33:02and decrease the percent, the elongation.
33:06And then increasing strain rate,
33:09same effects as the decreasing temperature.
33:12That's what normal, like a temperature
33:14and normal polymer characterization observation.
33:18We are not going to go detail for this.
33:21That's just a regular observation for the polymers.
33:24You don't have to worry about,
33:27to, uh, memorize a lot of things.
33:30So here, melting and glass transition temperature.
33:35These two, um, the temperature scales control thermoplastic.
33:41What factors affect the TM and TG?
33:46So, um, what's TG?
33:48Like, uh, that's the glass transition temperature
33:52marks the, the change from rigid.
33:56And, um, the glassy behavior to rubbery response in amorphous region.
34:02Do you remember that all the polymers have a crystallinity part
34:06and then the amorphous part, right?
34:09This part is, uh, moving.
34:12That's glass, the glass temperature.
34:16This one.
34:18And then this melting temperature,
34:20the, maybe both of them are, like, into the changing.
34:28So, um, the, below this TG polymers are often brittle
34:35and above TG they become rubbery.
34:38The melting temperature Tm applies to, like, a crystal region too.
34:43That's the main difference between, uh, Tm and Tg.
34:48This might be quite useful to understand polymers for your, uh, research.
34:53What's Tm, what's Tg?
34:56They look the same, almost the same for regular uses.
35:01But in the case of Tg, just this amorphous part.
35:06And Tm, the whole part.
35:09Okay.
35:11And chain stiffness increased by presence of bulky side group.
35:15You know, the, in the case of polyethylene, we have this, this kind of things.
35:21The ethylene can be, uh, can be used for synthesizing the polymers.
35:29If we have some side group here, this poly, this, this can generate polystyrene.
35:35If we do polymer, do polymerization.
35:38So, uh, all this Tm, Tg can be controlled by the bulky side group.
35:45Such as this one, you know, in the case of polymethyl metacrylate,
35:49that, that this part is quite the complicated.
35:52I don't even remember that one, like COO, uh, methyl group, I guess.
35:58That's a methyl metacrylate.
36:00And, uh, that bulky side groups.
36:05And also, like, polar groups or side groups.
36:09And chain double bonds.
36:11In the case of the acetylene, if we do polymerization,
36:16we have, still have, like, double bond.
36:19Because we utilize only one, one of the bonds.
36:23Right?
36:24So, uh, if we do have this double bond,
36:27or this side chain can have a double bond inside, too.
36:30For example, this, the, the benzene ring may have, still,
36:35the conjugated double bond, right, inside.
36:38And also, see, like, aromatic, the chain group.
36:43That's benzene ring.
36:44Right?
36:45When we say aromatic, that's normally saying this benzene group inside.
36:52Okay.
36:53Let's move to the next.
37:07Time-dependent deformation.
37:09The, this is quite important.
37:12You have to pay very much attention to understand this part.
37:16The, to understand this graph.
37:19Okay.
37:20Um, the polymers are viscoelastic.
37:23Meaning, their response blends elastic and viscous components,
37:28and, uh, depends on time.
37:30So, under a sudden load, we see immediate, uh, elastic strain,
37:35followed by slow viscous strain.
37:39On, uh, on unloading, only the elastic part fully recovers.
37:44In this stress relaxation test,
37:49strain is held.
37:54You know what strain is?
37:56Remember that?
37:57So, when we have the tensile strength,
38:02and then that's elongated a little bit.
38:05Right?
38:06That chain, the distance is strain.
38:10Right?
38:11A and B.
38:13So, A plus B, that's like a strain.
38:19So, um, the two, uh, ones, in the case, let's take a look at,
38:27let's think about the metal.
38:30We have metal.
38:32And then, to increase that volume, to, uh, to increase the, like,
38:39let's say it's fully the, the, what is said, recovering the metal.
38:46Then, to keep this distance, to keep this length,
38:53we have to give the, the, we have to keep the force.
38:56Otherwise, it goes back.
38:57Right?
38:58That's what it says.
39:01So, um, to keep the, this distance,
39:05do we have to keep the force?
39:08Or, we don't need any further force.
39:11Or, even lower force.
39:14So, observe decrease in stress with time.
39:21That's, like, uh, abnormal, the observation, which is quite different from the, the, the metallic compound.
39:31You know, I, I know, like, uh, some metals are not recovering to its original states.
39:38And, uh, that's also considered as, uh, some other cases.
39:46That's, but in, in, in this polymer cases, it's more obvious in time.
39:52That's, the, the stress is quite slowing down.
39:57That's what it says.
40:02The, um, in this, uh, the, that's, uh, the, that's, that's the thing.
40:09Like, a strain is held.
40:11And the stress decays over time due to molecular rearrangement inside.
40:17So, once that rearrangement, rearrangement occurs, then they can stay that way.
40:25It doesn't, uh, go back to the original, uh, the, uh, position.
40:30The relaxation modulus decreases with time and, uh, with all time temperature, too.
40:37So, relaxation modulus is kind of some sort of equation.
40:43The, this is also depending on some, the temperature and, uh, the other things.
40:50That's our first police side.
40:56Okay.
40:57Then, um, we also have some other terms, like, craze.
41:03You know what craze is?
41:05It's, it's kind of like a crazy person or something.
41:10Craze.
41:11Craze formation prior to cracking.
41:15Cracking is some kind of the failure, right?
41:18So, the, many, this, uh, glassy thermoplastic is, exhibit crazing prior to, uh, fracture.
41:28This is fracture.
41:29And craze is a kind of a localized, load-bearing zone.
41:37This is craze.
41:39Then, of micro-voids, micro-voids.
41:44They're bridged by aligned febrile.
41:49This is the febrile bridge.
41:54Crazes can, uh, transmit stress.
42:01Right?
42:02They, they can hold the stress, absorb energy, growing the perpendicular to, uh, tensile stress.
42:09It's, it's perpendicular.
42:11Right?
42:12Then, if febrile fails, that's what happens here.
42:16All the febrile fails, and voids link up, link up, and craze evolves into a crack.
42:26Thickness, notch, severity, and, uh, environment influence, whether crazing toughens the material, or, whether cracks form directly.
42:41No, in some caves, we open, give this kind of craze intentionally, to make it easy to tear it off.
42:53Right?
42:54Okay, let's move to the next, like a polymer formation.
43:01We already learned about this in the previous chapter.
43:05Uh, I don't know why, why they have this one in this, uh, the chapter again.
43:12But, like a addition, we didn't mention that words here, like addition polymerization, and then condensation polymerization.
43:22Addition is kind of adding.
43:25Condensation is kind of the, what is that, what's the, the, the best words for the condensation.
43:35The, the bonds stepwise between the functional group, we will see.
43:40Often, the, releasing, or, the, removing small byproducts, like water.
43:49So, you know, the water can be removed, that, that can be condensed.
43:55Right?
43:56That's why it says like condensation.
43:58We will see how it goes.
44:02Initiation, initiation.
44:04We already observed that.
44:06What, what is it called?
44:07You remember that?
44:09Initiator.
44:10Radical.
44:11Uh, most likely hydrogen, I'm sorry, like any kind of peroxide or NBS.
44:19So, if you look up the word like NBS in the Google side, and then say polymer initiator, that's one of the, uh, the, uh, very original compound.
44:33And then, this, the, the, what is that, HOOH, hydrogen peroxide, this one works too.
44:42Normally, most of the experimental lab can have this one easily.
44:48Or, your home, this is also used for sanitizer, right?
44:53So, the hydrogen peroxide can be added to any, the, the organic compound vessel.
45:01So, that will work to initiate one.
45:05And then, next one is propagation, right?
45:08Propagation.
45:09And then, I, I hope you remember this radical.
45:15And then, this electron, one of the electron goes this way, the other way, and generates the same thing.
45:24Right?
45:26So, uh, that's, uh, the propagation.
45:32And termination.
45:33When we have the, once it's growing like this, this, two of this can be combined to terminate.
45:44Or, this radical, the initiator, if we have a lot of initiator, that can be also used to terminate the, the one, the polymerization.
45:57So, we should be very careful.
45:59The controlling the, I don't think we use many initiator, but that can be controlled.
46:07We can add some, some of the initiator, the, in time.
46:11Right?
46:12So, that's, like, some sort of addition chain polymerization.
46:20The, while that condensation polymerization, this is nylon 6-6.
46:25I, I showed you before.
46:27The, there are, like, six carbons, then six carbons.
46:32That's why it's called nylon 6-6.
46:35And then, this, the amine.
46:38Amine group has the, uh, NH2.
46:43And then, most likely carboxylic acid has, um, this kind of, the functional group.
46:50And then, this makes water.
46:52That's the H2O.
46:55And then, this goes out.
46:57That's condensing.
46:59So, bifunctional or multifunctional monomers react stepwise.
47:05Forming bonds and, uh, often releasing small molecules.
47:09This one.
47:11Then, water or methanol.
47:14Sometimes it, it becomes, it's methanol.
47:17Molecular weight increases gradually.
47:20Because, uh, the, this reaction must occur to, uh, to increase their, the, the molecular weight.
47:30But, in the previous slide, the propagation should occur a lot.
47:38And then, this is the, later, they just combine each other.
47:45So, uh, their molecular weight is, like, drastically increasing.
47:50But, in the case of condensation, it's, uh, uh, you can control.
47:57Because, uh, you know, once this reaction occurs, terminal group is this one, and the other one is this one, right?
48:04So, they might react each other to make some circle.
48:08But, most likely, we already learned about the end-to-end group, the distance is quite large.
48:14So, uh, their, um, their chances is, is, is quite low.
48:22But, you know, this one is still reactive.
48:26As long as we add more, uh, amine compound with, like, carboxyl gas, the reaction keeps going.
48:35So, we can control the, the molecular weight for this polymerization, um, in detail, more detail.
48:43So, um, the, the, the advantage for this condensation polymerization is that kind of thing.
48:55Okay?
48:57This classic examples include, like, polyester.
49:02If you take a look at the label on your clothes, you will see, like, polyester and polyamides.
49:12And this one is also very important, the reaction which is happening in our body.
49:19That's amide group, uh, amide, uh, amide link, amide reaction.
49:28I don't know that's, like, amide or amide or whatever the pronunciation could be.
49:38Okay.
49:39So, uh, this part will be explained in the next recording.
49:49Thank you.
49:50Thank you.
49:51Thank you.
49:52Thank you.
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