Presentation Textile Physics

7/25/2019 Presentation Textile Physics

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Introduction:

An essential requirement in fibre structure is some means of ensuring continuity, and strength,along the length of the fibre .Because of the fineness of fibres ,transverse strength is of muchless importance. In the linear-polymer fibres, which are used in textiles, it is the long-chainmolecules that provide this continuity.

The basic requirements of fibre formation would be!a" long-chain molecules, corresponding to the long fibres that ma#e up yarns if the moleculesor fibres are too short, there will be a loss of strength.!b" A more or less parallel arrangement of the molecules$!c" %ateral forces to hold the molecules together and give cohesion to the structure$!d" &ome measure of freedom of molecular movement in order to give the necessary extensibilityto the fibre and some openness to give room for moisture absorption and upta#e of dyes.

'iber-forming polymers of apparel fibers should be To be a good textile fibre, fibre polymer system meets the following requirements.

(. )ydrophilic.*. +hemically resistant. %inear

. %ong. +apable of being oriented/. Able to form high-melting-point polymer systems.

0xplanation of these requirements is now given

1. Hydrophilic properties:

'iber polymers should be hydrophilic. This means that the polymers should be polar, enablingthem to attract water molecules. A fiber is comfortable to wear if its polymer system consists of hydrophilic polymers, and the system itself permits the entry of water molecules. There are, of course, fibers whose polymers are not hydrophilic !i.e. their polymers are hydrophobic" and yetthese fibers are used for the manufacture of apparel. In order to ma#e the textile materials of these fibers more absorbent and, hence, more or less comfortable, hydrophilic-polymer fibersneed to be blended hydrophobic-polymer fibers. 1ylon and polyester, for example, arehydrophobic-polymer fibers and are often blended with cotton, viscose or wool !e.g. two thirds polyester 2one third cotton blend". &uch blending improves the absorbency and comfort of their textile materials. Acrylic is also hydrophobic-polymer fibers. 3nitted outerwear made of acrylicsis very popular$ but it is found that it is useful to wear this non-absorbent #nitwear over anabsorbent or hydrophilic-polymer fiber garment to counter or reduce the potential discomfortwhich might otherwise be experienced. A fiber consisting of hydrophilic polymers attracts water

molecules which prevent or enable, the discharge of any static electricity accumulating on thefiber. The static electricity is discharged by the water molecules, because of their polarity, to thesurrounding atmosphere. A build up of static electricity on a fiber is undesirable because it will

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cause the fiber to attract dirt particles more readily and thus to soil more quic#ly. 4arments that become charged with static electricity may cling together to such an attract dirt particles morereadily and thus to soil more quic#ly. 4arments that become charged with static electricity maycling together to such an

2. Chemical resistance:

'ibre polymers should be chemically resistant for a reasonable length of time against thecommon degrading agents such as sunlight and weather, common types of soiling, bodyexudations, laundry liquors and dry cleaning solvents. +hemically resistant polymers should alsonot be toxic or ha5ardous to wear against human s#in$ this is a most important requirement whichis usually ta#en for granted.

Although fibre polymers should be chemically resistant, they should not be inert !i.e. totallyuncreative". +hemical inertness of fibre polymers tends to have a detrimental effect on other fibre 6forming requirements. 'or instance, the polymers of polyethylene, polypropylene may be

regarded as chemically inert from a practical point of view. 'or this reason the polymers are non- polar and hence hydrophobic, ma#ing the textiles of these fibers non-absorbent, with a greasy,slippery, aesthetically displeasing handle.

3. Linearity:

'ibre polymers should be linear !i.e. the polymers should not be branched. As explained in five below only linear polymers allow adequate polymer alignment to bring into effect sufficientinter-polymer force of attraction to give a cohesive polymer system and hence, useful textilefiber.

It is, however, a normal occurrence for many fiber polymers, which need to be linear, to haveside groups, as distinct from branches. &ide group may be thought of as causing along the polymer bac#bone, rather then the distinct pro7ection of a branch. Thus the nitrile groups of acrylics, the hydroxyl and methyl groups of the cellulose fiber, and the hydroxyl and acetylgroups of ester-cellulose fibers are some examples of side groups.

The importance of considering side groups on polymer is the fact gives rise to three types of linear polymer configurations, better referred to as three types8 stereo polymers. &tereo from the94ree#: is used here in the sense of spatial or three dimensional arrangements of the side groupson the polymer bac#bone. In man made fiber manufacture it is important to have the right stereo polymer for the extrusion of useful filaments. The three types of stereo polymer are described below

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3. a. The atactic polymer

This is a stereo-irregular polymer. It has its side groups arranged at random !i.e. in no particular order" above and below the plain of the polymer bac#bone. Two dimensionally this mayrepresent thus

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - -

;olymer bac#bone &ide group

Atactic polymers are usually not found in the polymer system of fibers. This is because they donot allow close enough alignment or orientation of polymers for the formation of effective inters polymer forces of attraction. If atactic polymers were used they would give an insufficiently

cohesive polymer system, as indicated by wax-li#e substance formed.

3. b. The syndyotactic polymer:

This is stereo regular polymer. It has its side groups arranged in a regular alternative fashionabove and bellow the plain of the polymer bac#bone. Two dimensionally this may be representedthus

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

&uch a regular polymer structure permits close enough alignment or orientation of polymers toform effective inters polymer forces of attraction, giving a cohesive enough polymer system tofrom useful fibers. The polymer of cellulose and some chlorofibers are thought to besyndyotactic polymers.

3. c. The isotactic polymer:

This is also a stereo regular polymer. It has, however, all its side groups arranged on the sameside or plane of the polymer bac#bone. Two dimensionally this may be shown thus

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

--



Isotactic polymers orient themselves readily and very closely. This permits effective formation of inter polymers forces of attraction to give a cohesive polymer system and thus, a useful fiber.;olypropylene and pure acrylonitrile fibres are #nown to have their polymer system constitutedof istactic polymers.

4. Length:

'ibre polymers should be long. It has been found that the length of polymers constituting thecommonly used apparel fibers is in excess of one hundred nanometers.;olymers of such length can readily be oriented. )aving the polymers oriented can give rise tosufficiently effective inter 6polymer forces of attraction to form a cohesive polymer system and,hence, a useful fibre.In general, the longer the polymers the more cohesive will be the polymer system and thestronger will be the fibre. 'or this to occur the polymers have to be closely aligned or welloriented so that the maximum formation of inter-polymer forces of attraction can ta#e place.

'ig %inear polymers they can assume various configurations as shown$ however, they can be oriented or aligned to form a cohesive polymer system suitable for useful fibre formation.

'ig Branched polymers the can assume various configuration as shown how ever they can

not be sufficiently oriented to form a polymer of adequate cohesion$ therefore their unsuitable for fiber formation.

'ig A strong fibre because it has long polymers which are well aligned or oriented, giving ita long <path of brea#8



'ig A wea# fibre because it has short polymers$ although they are well oriented, theshortness of its path of brea# tends to ma#e it wea#.

5. Orientation:

'ibre polymers should be capable of being oriented, as foreshadowed under above. This meansthat the polymers are or can be arranged or aligned !i.e. oriented" into more or less parallel order in the direction of the longitudinal axis of the fiber or filament.It is not #nown how the orientation of polymer occurs during the growth of natural fibers. =ithman made fibers, the operation called drawing, which stretches the extruded and coagulatedfilament, causes the polymer to orient them selves longitudinally into a more or less parallel

order. The extend of this drawing mar#edly influences the properties of the filaments and thoseof the staple fiber which may be cut from it.;erfect orientation of polymers is usually not obtained, nor is it desirable, as explained in Table(.. The orientation of polymers in the system of any fiber consists of two distinct, yet integrated

forms. The two forms of polymer orientation are called the amorphous and the crystallineregions. !&ee Table (. for definition, explanation, comparison and influence upon fiber properties of the amorphous and crystalline regions."

6. ormation o! high"melting"point polymer systems:

A fiber consisting of a high melting point polymer system tends to have adequate heat resistanceto enable it to withstand the various heat treatments of textile finishing, apparel manufacture, andthe heat subsequently applied to it during its useful life as a garment. It appears that a fibersmelting point needs to be above ** if it is to be useful for textile manufacture and apparel use.Insufficient is #nown about the influence of polymer orientation and polymer composition uponthe melting pointed heat resistance of polymer systems and hence fibre. In general, however, thelonger the polymers and the better orientation, the more inter-polymer forces of attraction will beformed, giving a more cohesive polymer system with a higher melting point. This means moreheat or #inetic energy will be required to brea# the enter polymer forces of attraction and free the polymer from each other.



#. Conclusion:

It is important for a textile fibre to full fill the required properties to get the desirable aspect fromfibre. But this is not possible to a fibre to full fill all the required properties, so which fibreclosely touched the required properties called good textile fibre.

$. %e!erence:

(. Textile &cience

By- 0.;.4. 4ohl %.>. ?ilens#y

*. &cience of Textile raw materials

By - @d. Ashraful Islam

. +lass lecture

. www. wi#ipedia.org

/



Requirements of the ber formation

Textile Physics (TEX 302)

Grou! "

Prepared For #ithi "ho$%ury

+ourse Instructor,

>epartment of Textile 0ngineering.

Prepared By

&ossain 'ohamma% 'urtua li (0*3+00+,)'ihir Ran-on .as (0*3+00*/)

iu 1en (0*3+002)

'% Raaul 4arim (0*3+0053)

Emrul 4aysh (062+60//)

Submission Date: 7th may 2009

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Presentation Textile Physics