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Module 1: Introduction à la finissage des textiles et au finissage de la résine

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Introduction to Finishing

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Welcome, to this course on textile finishing as we had mentioned in the introductory video alsothat we would definitely look into the chemistry. And then it’s application particularlytechnological application which has led to many treatments and finishing processes.(Refer Slide Time: 00:50)
So broadly what are we going to cover I will just take a few minutes to just explain in this wholecourse some of the topics that we will be covering. Obviously, we will have some time we shallspent on introduction is to what the finishing is, generally how do we classify these finishes, interms of mechanical and chemical finishes, this is what we going to be working on within the orspecific finishes we will have a wrinkle resist finishes, what is the need.The general approach for obtaining a wash and wear finishing, in within this topic we will try tosee what kind of agents like crosslinking agent which are used for obtaining wrinkle resist finish.The catalyst that are needed to complete the reaction, the process and the characterization of a
finished fabric. Further, we will go and talk about stiffeners and softeners, their principle and thechemistry of these compounds, that will be interesting to see.We will also talk about waterproof, water repellent and waterproof breathable finishes, how theyare generally done, in brief we will be talking about it, some of the chemistry will also come intopicture. Another important finish which we call as fire retardants or fire-retardant finishing. Wewill see how it is done what are the principles and a technology that is used.(Refer Slide Time: 02:47)
More topics. Antimicrobial finishing, bio-polishing. They are basically enzyme-based finishing,as the bio polishing is concerned and how bacterial degradation takes place and if you want toavoid growth of bacteria, what are we going to do about it. Soil repellency and soil release, thisis an important topic of finish these days. So, we will spend some time here as well. Then theother material that we have wool. So, something specially related to wool, a milling, setting,shrink resistant finishing, some special finishing for silk as well we will cover.We will also spend some time on topics related to energy management and technologies whichare more energy efficient. Interesting in this will be low liquor application and foam finishing.Finishing of synthetic fabrics, some of the important things you call the heat setting, antistaticand other special finishing required for synthetics also will be covered in this course. And some
discussions on mangles, driers, stenters and some mechanical finishing processes includingsanforization.
So, all these topics will be covered not exactly in the same order, you know. Sometimes some ofthe machines like mangles, maybe discussed before, so that it make sense. Some finishes maybedone at a later stage, so, but briefly this describes to what we are going to be covering in thiscourse.(Refer Slide Time: 05:10)
So, we come to the first lecture what we are going to do today, giving an introduction tofinishing is a general lecture. And therefore, would demand attention only to the extend thebroadness of the topics that we were talking about.(Refer Slide Time: 05:33)
So, what we shall learn today is, the need for finishing and general types of finishing processesthat are used in the industry today.(Refer Slide Time: 05:53)
So, let us look at what we know about textile fibres and fabrics. As we mentioned in earlier littlediscussion that the chemistry of the fibres, will determine as to why a certain type of finish isrequired. So, let us say, we generally remember, recall from our earlier courses that you mayhave done, what are the important textile fibres, fabrics or fabrics made from them. Do youremember them? Can you recall some of the fibres and fabrics? yeah, Cotton.
Of course, cotton is one of the most important fibre, which is used in making all kinds of appareland even industrial household textiles. So, it is an important fibre. Viscose is another fibre. Whatis the difference between these 2 fibres? So, one of them is called the manufactured fibre, whichis called the viscose and the cotton is a natural fibre. And what is common in them? Thecommon part is both are cellulosics.Then you may have heard of fibres like acetate or triacetate. How are they made? What is thebasic raw material, the polymer? Are they natural or manufactured? Yes, they are manufactured.But, how? The basic material is cellulose, the cellulose is modified, acetylated, so you makeacetates or triacetate, where all the hydroxyl groups have been substituted. Then becomestriacetate, if you look at it, from the anhydroglucose unit.Anhydroglucose unit should have 3 hydroxyl groups 1 primary and the 2 secondary hydroxylgroups. So, if you replace them completely by an acetate then you will have a triacetate. Is thistriacetate a thermoplastic fibre or non thermoplastic fibre? Yeah, non thermoplastic orthermoplastic? Is it non thermoplastic? No.(Refer Slide Time: 09:14)
These are thermoplastic fibres, because the reason why cotton cellulose is non thermoplastic, thatreason which is the intermolecular hydrogen bonding, that reason has been basically removed bysubstituting acetate groups. So, then you have wool, interesting natural fibre. Silk, another
interesting natural fibre. So, we are talked about natural which are wool, silk, cotton,manufactured fibres like viscose which is regenerated, acetate and triacetate which are modified.Any one of them is synthetic among the fibres that we have listed here? What do you say?Anyone among these, is in the synthetic category? No.(Refer Slide Time: 10:21)
So, we have other fibres which are important, which are the polyester, which is the polyethyleneterephthalate, because if we just talk about polyester that are many types of polyesters will bethere. Then other commercially successful fibre is nylon, nylon 66 and nylon 6. So, these are 2important commercial fibres. Otherwise there are many other nylons, that are also available.Polyacrylonitrile, if you remember, this fibre has more or less been used as a substitute for wool.If you remember this, is good, otherwise try and find out, why polyacrylonitrile in apparelindustry or apparel sector is considered as a substitute for wool? Polypropylene, anotherinteresting fibre, which is less use for apparel, maybe for household more, industrial applicationis much more. All these fibres which are listed here are called synthetics, synthetic fibres. Whydo we call them synthetic fibres?Because, their backbone that is the polymer chain does not exist in nature and it has to besynthesized by using compounds called monomers. So, you have monomer which have to be
reacted to make them polymers and therefore, they are called synthetics. Invariably, they are allin the range of or in the class of thermoplastics. So, these are some of the important fibres whichyou will be coming across everyday.While there other category of the fibre, which is called the high performance fibre, which are likeNomex, Kevlar. The difference between this, they are also known as polyamides, polyamidesalright! And these are called aramids. They are aromatic amides, so, they have aromatic ring, inthe thing and while these nylons do not have, so they are simply in the class of polyamide. Theseare called the aramids, they are high performance, invariably we may be using them only inspecial applications what not in the day to day applications.(Refer Slide Time: 13:31)
So, where do we stand? If somebody asks, is the chemistry of these fibres different? Is itdifferent? Yes, of course it is different. Whether this difference and the chemistry is going toaffect their performance characteristics? Like, some of them are thermoplastic, some of them arenon thermoplastics, some of them may be biodegradable, some of them may not bebiodegradable. Will it depend on this chemistry of these fibres? Yes, of course.Let us see, some of these fibres and that difference probably is going to become a basis as to whya particular type of finishing process is required for some fibres and the other required for theother fibres.
(Refer Slide Time: 14:33)
So, will we talk about requirements? Then we let us say we look at the advantages, limitations ofthese fibres and the fabrics made out of them also, not just the fibres. So, what does come to yourmind? The most important fibre that comes to your mind is cotton, the king, which is called. Andwe just talked about its chemical structure. What is the chemical structure? Right, cellulose, sowhat is cellulose? I am sure, you will either remember or go back and check it out.So, it is a cellulose based structure. So, what are the advantages of cotton? Yeah, you say that theadvantage, what is the advantage? Well, it absorbs moisture, it is a hydrophilic fibre and watercan be retained more, so a large number of people would have come to a conclusion, they did.That all materials, garments made from the cotton, should be next to the skin. So that, anymoisture that is absorbed, which is secreted out, gets absorbed easily. Right!That is why you like to have cotton near to your skin, but this may not really be an advantagetoday. Because if it absorbs more moisture, it dries also slowly. Say suppose, an athlete isrunning, these all cotton things he is wearing, or she is wearing. Then the perspiration will bethere, it will be all wet and how do you think you will like a wet material clinging to your skin,and body, I do not know. Would you like to consider this as an advantage? What else?
Yeah, it can be dyed easily because normally we want to dye in aqueous medium, with watergets absorbed more and then the dye also goes, it can be printed relatively easily, can bechemically treated also easily. Yes, this advantage could be there or that is a process advantage.What about the advantage of the user? Is the user interested how did you dye? Is the userinterested how did you print or finish? What user will be interested? What is the property that heor she is experiencing because of the textile, that he has or he has been wearing?What about creasing? When you have any textile garment that you are wearing it creases. Right!It does crease. So, does the cotton-based fabric crease more? Or less? More or less? They creasemore. Have you experienced it or not? They crease. Do you like the crease material or creasedgarment being worn? Some of you can. Most of people will like to have a garment which doesnot crease. So, this is a limitation. What about burning? Have you ever seen any cellulose, paperbeing burnt? Does it burn readily?It does burn readily. The cotton also will burn very easily. So, all cotton garments, householdmaterial, if there is a fire that is the most dangerous thing that you can experience. So, this is alimitation. Biodegradability, if suppose you keep any cotton-based garment material, let us say inthe soil or keep it unwashed for a long period, what would happen? You know, you will havefungus or rot growing on it, at the end will get degraded also.Because, in nature we have an enzyme, called cellulase, so it can degrade cellulose and cotton iscellulose, so it gets degraded. So, is it an advantage or a limitation? For some obviously, it is alimitation. In modern world, somebody says it is an advantage also. Why? Because, at the end ofthe life of a product, you have to dispose this. And when you dispose any such product, then weexpect that it will biodegrade itself, will not have to be incinerated or burnt out or do something.So, from environmental point of view, it maybe an advantage from longevity point of view, itmay not be that much of an advantage. So, all that is there, if it is the cotton. Water repellency,soil repellency, what do you think about it? It absorbs water, it cannot repel water, so they areagainst. So, in case you are interested in repellency of water then obviously you have to say thatit is a limitation in that sense.
And same is, something related in soil repellency, who wants the fabric to be soiled but you havea water-based ink or any other soil it will get soiled. So, it is a limitation.(Refer Slide Time: 20:57)
Viscose, what do you think about it? Is it similar to cotton? Yes, it is. In many senses, it issimilar to cotton, because cellulose. So, all those finishes or the limitations that we have seen inthe cotton, should be here as well, it will burn the way that burns, it will be hydrophilic, so, itabsorbs, it would not repel water. One of the difference obviously, is a manmade ormanufactured fibre, that is the difference, plus, the crystalline component in viscose would beexpected to be less compare to what we see in cotton.And therefore, the absorption capacity the moisture regain and other type of things will be seento be different. The next important fibre that we have, you can talk about, let us say wool. Whatis the chemistry of wool? Basically, these are, these are protein based fibres. So, protein. Ourhair also is similar to wool is called keratin, sometimes they are also called polypeptides. Issomebody ask this question, is wool, we understand it is protein or sometimes calledpolypeptide, is it a polymer?We never ask this question to cellulose ok, cellulose has a repeat unit which is called cellobioseand it keeps repeating itself, based on how much time the fibre grew or what have you done to it.
So, there is a monomer or a repeat unit which is repeated every time. Can we call wool or in away a protein a polymer? Can we call that a polymer?Actually, strictly speaking, although a peptide link and the associated group is being repeated,but the amino acids in every such repeat is different and therefore strictly it is not a polymer, sowhat do we call it? You can call it a macromolecule, which has large molecular weight. So, it is amacromolecule. But what it has? It obviously, has peptide links and so with hydrophilic it makesvarious types of bonds. Let us see what kind of bonds wool fibre would make intermolecularbonds, what? Does it make hydrogen bonds? Yes. It does make hydrogen bonds.Does it make Van der Waals forces? They will have intermolecular Van der Waals force? Ofcourse, it will have intermolecular Van der Waals forces also. So, the hydrogen bonding will bethere, you will have Van der Waal forces. But interestingly, wool would have intermolecular aswell as intramolecular hydrogen bonds. So, if somebody may have taught you in a normalconfiguration, it can take a helical configuration, the molecule itself can taken helicalconsideration.
And, hydrogen bonds can be here and hydrogen bonds can be formed here. So, inter and intra, soyou have Van der Waals forces which are possible, you have a inter and intra molecularhydrogen bonds, which are possible. They also have covalent bond. Which one? So, you haveintramolecular disulfide linkage or cystine linkage. So, it is a covalent bonding, it has. I am notsure if you have heard about hydrophobic bonding, have you ever heard about anything calledhydrophobic bond?Well, hydrophobic bond also has been defined as reciprocal hydrophilic effect. If there is lot ofwater around the molecules of this protein, then the hydrophobic part, because they do not likewater, they like to come together. So, in wool you can see hydrophobic bonds also, based on theenvironment, if it is hydrophilic. If it is not hydrophilic environment, they become redundant.But if there is lot hydrophilic environment, they have value.Now all this, is a part of a chemistry and if the chemistry is there, so their properties, is alsogoing to be working on them. Any specialty that we are looking at? Yeah, it has scales. Naturally
the wool is not a cylindrical smooth fibre but is got scales you remember. And because of scalesthere are certain properties which only wool will demonstrate and if you like them, it is fine, ifyou do not like them you have to work for a finish which will do reverse effect.(Refer Slide Time: 28:15)
So, looking at the part of the chemistry that we said what do you think? The creased recovery ofthis, fabrics made from wool, are going to better than cotton or inferior to cotton? Yeah, they arebetter. Because of this intermolecular crosslinking which is the covalent crosslinking is veryimportant, the recovery is better, even helical structure of the molecule is also better than youbend if the helical structure changes its shape, it likes to come back to its helical form also.So, that way the recovery of this is better than let us say cotton, burning compare to cotton haveyou heard of somebody catches fire or something is burning people say, well, put some blanketon top of that. Well, the blanket normally is associated with wool, normally does not have to be,so why do that? Do not say go and surround or wrap with a cotton sheet, that may also work forsome time, but wool.So, in general wool is also naturally more flame-resistant, compared to cotton, it does not meanthat it will not burn, it will burn but more resistant. Static charge development, do you think woolwill have static development? Invariable no, but in very cold climates, cold conditions almost
every fibre can develop static charge. Static charge is, when you rub something or you come incontact, then the charge get station on the surface.So that is a limitation. So, we had some advantage, some limitation. Water and soil repellency, itwould require in case, because it is a hydrophilic material. Is it biodegradable? Is itbiodegradable? Yes, of course it is. So, all the advantage, disadvantage you talking about arethere, in fact, if you may have heard that, there something called a moth, an insect which can eatwool, say have to take special care. Right!And so, insect proofing, biodegradability, all that if you look at it, some people say it is anadvantage. For the person of the user it becomes limitation. Have we heard about somethingwhich we call as a felting? Felting? Felting is a phenomenon, where the woolen garments if youwash them, you might find there is an entanglement, the structure is not the way you want it. Forexample, if a woolen knitted sweater, if you wash in a washing machine, what you get at the endof the day? Does not look like the original sweater.So, because the fibres get entangled so that, it is felting. If you like felting, it is good, if you donot like felting then it is bad. Of course, we will require soften, stiff finishes as well, based onwhat you want. Normally people like it to be softer generally, compared to 2 fibres obviously,because of scales and bit of rigidness and so and so forth may appear to be little harsher.(Refer Slide Time: 32:22)
Silk. Compared to wool chemical structures is more or less same. What is the difference? Whatis the difference? You remember, this is also protein. But it does not have scale. It is a smoothermaterial, in the intermolecular bonding also there is difference. One of the differences is there isno sulfur and therefore though no cystine intermolecular crosslinking. But it is a protein fibre ofa different kind, it is not called keratin, it is called sericin and fibroin.So, there are 2 types of proteins which naturally are extruded by the silkworm. One of them ismore useful which you call the fibroin, which is also protein. Sericin which is called a gum, notuseful as a fibre, it is removed, used for some other purposes but removed. So, there is differencebetween these and so if you look at the crease recovery of silk fabrics, is much inferior comparedto a wool. Is that right?Flame resistance also is less than wool, have you, did you expect it? Have you seen anythingburning? You must have done some burning test on wool fibres? Some burning test? It is meltlike burning beans, protein hair, burning hair, smell burning hair. Both of them will give similarsmell, so you cannot identify but you have to do chemical test to say there is no sulfur there moreor less, flame resistance is not as good also.(Refer Slide Time: 34:28)
And look at synthetic fibres, most of synthetic fibres as we have mention before, all the 4 fibresthat we talked about, they are thermoplastics. So, they can be handled by heating. You can docertain changes which can be permanent, semi-permanent by heat, which the other 3 fibres thatwe just talked about 4 fibres, they would not respond because they are non thermoplastics.Generally, all of them relatively more hydrophobic compared to the natural fibre that we talkedabout.
So, if hydrophobicity is an advantage, it is good. If it is a disadvantage, then you have to dosomething about it. Burning behavior, most of them burn pretty nicely, so if you are looking at aresistance to flaming, they are not the one fibres which can be used, you have to do somethingabout that. Static charge, because most of them hydrophobic, most of them are prone todevelopment of static charge, this is an important property by the way.If you have a nylon carpet on your, any building, any you know, cinema hall, what have you, andlot of people keep walking around the same area, you might find it can develop a large amountcharge, very high voltage, you can see sometimes spark so much and if electronic equipments allaround, then obviously it can damage that as well. So, this is an interesting problem which iscertainly with, seen with synthetic fibres.
Crease resistance, have you experienced? People are wearing polyester, polyester cotton versusthe one who are wearing cotton, which one would crease more? As a user if you haveexperienced it, so obviously synthetic fibres have been seen to be more crease resistant. Theproduct, final product, that is there. Water and soil repellency, well they do not like to they arehydrophobic, so they like the oily soil more.But we will differentiate between repellency versus wetting, repellency versus absorption onmoisture, 2 different things. Then obviously, because they are hydrophobic, their dyeing,finishing, and other processes will also be slightly more different. Biodegradability, this certainlyis an interesting part in all of them, simple reason they were all synthesized, that the polymer didnot exist in nature.
And therefore, we do not have biosystems, enzymes, which can degrade them easily. So, fromstability point of view, it is an advantage, but from long term environment point of view it is andisadvantage, so people are working on these areas as well.(Refer Slide Time: 37:51)
So briefly this is what we talked about and the where we stand, if somebody ask this question,so, all fibres have, will have some advantages, some disadvantages and if we closely look at thething, their chemistry definitely going to play a role in determining what the property they willfinally show us. And, property in terms of some advantages, some disadvantages also. So, what
we are looking at the finishing as a process, hopefully would have some solutions, solutions todo, obviously, any limitation which we can overcome.(Refer Slide Time: 38:38)
You must have heard this term called unit operations. So, unit operations in chemical processing,just recall them, recall. Singeing, you know what it is? Yeah. Desizing, a necessary evil tosomebody, put size on a yarn, so that you can weave properly and so after weaving, you want toremove it. Scouring, in some fibres is required, not for all, but at least some fibres required,removing waxy material.Bleaching, mercerization, bleaching for cotton and definitely would be required, you can bleachother fibres as well, but that depends on which fibre you are talking about. Mercerization term isonly used for cotton, no other fibre mercerized, but they are unit operations. Of course, generallywe have to dye all of them as another unit operation, you will have to, you may have to do someprinting, to put colorful designs to increase aesthetics, so yes which is there.And the final process is finishing. You cannot sell almost anything to a user without doing somefinishing treatment, even if the simple finishing treatment you may have to do. And therefore,this is what is the most important chemical processing unit operation which we shall be talking inthis course in little more detail.(Refer Slide Time: 40:35)
At this point maybe we can answer this question, why finishing? Some of it you already know,because the fibres and the fabrics made out of them or the garments made out of them, will havesome limitation as a carryover, some limitation as a carryover of the properties of the fibre, thatmeans which is obviously being governed by the chemistry.So, one of the things could be aesthetics that it would look good, if you do some finishing. Yes,this could be one of the reasons why, for example after washing you like to iron, so that thesurface become more smooth, smoother, right? So, aesthetics could be one of the reasons whyyou may like to do finishing. The finishing term means this is almost a last process, you havefinished the thing and you have given it to the thing, end of the processing operation.Other important thing is, why we would like to do any finishing treatment, is to improvefunctional characteristics, like we said it creases, so can we do something, so that, it does notcrease? It burns rapidly, can we do something so it does not burn rapidly? Bacteria grows on it,can we do something, so that the bacteria do not grow on it? etc. So, the more important role thefinishing would play, is to improve the functional characteristics of a textile. And dependingupon what have we done, it is one process which adds quite a lot of value.If somebody sanforizes a fabric, it is put there, it is sanforized. If you give an anti-shrinktreatment, you write there, it is an anti-shrink treated fabric, value addition is very high.
(Refer Slide Time: 42:59)
So, if you look at the classification, general classification, we can talk about it, basically 2 ways.(Refer Slide Time: 43:09)
One is the mechanical finishing, that use on some kind of machine, to do a certain improvementand which improve certain functions or aesthetics, that is mechanical, where you only usemachines basically. Some of the examples, we will take it later. The other is chemical finishing,that means you are going to use certain amount of chemicals, which is going to alter theproperties in one way or the other, obviously, in favorable to us.
Of course, there is no doubt that machines are going to be integral part of all finishing processes.You cannot apply a finish or do anything without a machine. So, even if you are doing chemicalfinishing some machines will be used, even to apply the chemical effectively.(Refer Slide Time: 44:16)
So, what are the mechanical finishers? We can look at it. Calendaring is one of them. We willnow discuss all of them just now. We are just talking about calendaring, it is like ironing,removing creases. Sanforizing is very important finish, which reduces the shrinkage of a fabricafter washing. Raising. In singeing we are removing the hairs, burning them. In raising by, weare actually doing the reverse after the final finish you want to raise the hair fibres from thesurface, so that they look nice.Something similar is called sueding, so sueds, you must have heard, it is a mechanical finish.Embossing, you may like to put a design, some kind of a design on the fabric by embossing.(Refer Slide Time: 45:12)
Then, there are chemical finishes where performance is going to be more important than theaesthetics. Crease resistant finish is one of them. Sometimes it is