nylon is a thermoplastic

8/2/2019 Nylon is a Thermoplastic

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Nylon is a thermoplastic, silky material, first used commercially in a nylon-bristled

toothbrush(1938), followed more famously by women's stockings ("nylons"; 1940). It is

made ofrepeating units linked by amidebonds and is frequently referred to aspolyamide(PA). Nylon was the firstcommerciallysuccessful synthetic polymer. There are two

common methods of making nylon for fiber applications. In one approach, molecules with

an acid (-COOH) group on each end are reacted with molecules containing amine (-NH2)groups on each end. The resulting nylon is named on the basis of the number of carbon

atoms separating the two acid groups and the two amines. These are formed into monomers

of intermediatemolecular weight, which are then reacted to form longpolymerchains.

Nylon was intended to be a synthetic replacement forsilkand substituted for it in manydifferent products after silk became scarce during World War II. It replaced silk in military

applications such asparachutesand flak vests, and was used in many types of vehicle tires.

Nylon fibers are used in many applications, including fabrics, bridal veils, carpets, musical

strings, and rope.

Solid nylon is used formechanical parts such as machine screws, gears and other low- to

medium-stress components previously cast in metal. Engineering-grade nylon is processed

by extrusion,casting, andinjection molding. Solid nylon is used in hair combs. Type 6,6

Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the mostcommon commercial grade of molded nylon. For use in tools such as thespudger, a nylon

is available in glass-filled variants which increase structural and impact strength and

rigidity, and molybdenum sulfide-filled variants which increaselubricity.

Aramids are another type of polyamide with quite different chain structures which include

aromatic groups in the main chain. Such polymers make excellentballistic fibers.

Chemistry

Nylons are condensation copolymers formed by reacting equal parts of adiamine and adicarboxylic acid, so that amides are formed at both ends of each monomer in a process

analogous topolypeptidebiopolymers. Chemical elements included arecarbon,hydrogen,

nitrogen, and oxygen. The numerical suffix specifies the numbers ofcarbonsdonated by

the monomers; the diamine first and the diacid second. The most common variant is nylon6-6 which refers to the fact that the diamine (hexamethylene diamine,IUPAC name:

hexane-1,6-diamine) and the diacid (adipic acid,IUPAC name:hexanedioic acid) each

donate 6 carbons to the polymer chain. As with other regularcopolymers likepolyesters

andpolyurethanes, the "repeating unit" consists of one of each monomer, so that theyalternate in the chain. Since each monomer in this copolymer has the same reactive group

on both ends, the direction of the amide bondreverses between each monomer, unlikenatural polyamideproteins which have overall directionality:C terminal N terminal. In

the laboratory, nylon 6-6 can also be made using adipoyl chloride instead of adipic.

It is difficult to get the proportions exactly correct, and deviations can lead to chain

termination at molecular weights less than a desirable 10,000 daltons (u). To overcome this
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problem, a crystalline, solid "nylonsalt" can be formed at room temperature, using an exact

1:1 ratio of theacid and thebaseto neutralize each other. Heated to 285 C (545 F), the

salt reacts to form nylon polymer. Above 20,000 daltons, it is impossible to spin the chainsinto yarn, so to combat this, some acetic acid is added to react with a free amine end group

during polymer elongation to limit the molecular weight. In practice, and especially for 6,6,

the monomers are often combined in a water solution. The water used to make the solutionis evaporated under controlled conditions, and the increasing concentration of "salt" is

polymerized to the final molecular weight.

DuPont patented[1] nylon 6,6, so in order to compete, other companies (particularly the

German BASF) developed the homopolymernylon 6, orpolycaprolactam not acondensation polymer, but formed by a ring-opening polymerization (alternatively made by

polymerizing aminocaproic acid). The peptide bond within the caprolactam is broken with

the exposed active groups on each side being incorporated into two new bonds as themonomer becomes part of the polymer backbone. In this case, all amide bonds lie in the

same direction, but the properties of nylon 6 are sometimes indistinguishable from those of

nylon 6,6 except for melt temperature and some fiber properties in products like carpetsand textiles. There is also nylon 9.

The 428 F (220 C) melting point of nylon 6 is lower than the 509 F (265 C) melting

point of nylon 6,6.[2]

Nylon 5,10, made frompentamethylene diamineand sebacic acid, was studied by

Carothers even before nylon 6,6 and has superior properties, but is more expensive tomake. In keeping with this naming convention, "nylon 6,12" (N-6,12) or "PA-6,12" is a

copolymer of a 6C diamine and a 12C diacid. Similarly for N-5,10 N-6,11; N-10,12, etc.

Other nylons include copolymerized dicarboxylic acid/diamine products that are notbased

upon the monomers listed above. For example, somearomatic nylons are polymerized withthe addition of diacids liketerephthalic acid ( Kevlar,Twaron) orisophthalic acid (

Nomex), more commonly associated with polyesters. There are copolymers of N-6,6/N6;copolymers of N-6,6/N-6/N-12; and others. Because of the way polyamides are formed,

nylon would seem to be limited to unbranched, straight chains. But "star" branched nylon

can be produced by the condensation of dicarboxylic acids withpolyamines having three or

more amino groups.

The general reaction is:

A molecule ofwateris given off and the nylon is formed. Its properties are determined bythe R and R' groups in the monomers. In nylon 6,6, R = 4C and R' = 6C alkanes, but one

also has to include the two carboxyl carbons in the diacid to get the number it donates to

the chain. InKevlar, both R and R' arebenzene rings
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Concepts of nylon production

The first approach: combining molecules with an acid (COOH) group on each end are

reacted with two chemicals that contain amine (NH2) groups on each end. This processcreatesnylon 6,6, made of hexamethylene diamine with six carbon atoms and adipic acid.

The second approach: a compound has an acid at one end and an amine at the other and is

polymerized to form a chain with repeating units of (-NH-[CH2]n-CO-)x. In other words,

nylon 6 is made from a single six-carbon substance called caprolactam. In this equation, ifn = 5, thennylon 6 is the assigned name (may also be referred to as polymer).

The characteristic features of nylon 6,6 include:

Pleats and creases can be heat-set at higher temperatures

More compact molecular structure

Better weathering properties; better sunlight resistance

Softer "Hand" Higher melting point (256 C/492.8 F)

Superior colorfastness

Excellent abrasion resistance

On the other hand, nylon 6 is easy to dye, more readily fades; it has a higher impact

resistance, a more rapid moisture absorption, greater elasticity and elastic recovery.

[edit] Characteristics

Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull.

Durability: its high tenacity fibers are used for seatbelts, tire cords, ballistic clothand other uses.

High elongation

Excellent abrasion resistance

Highly resilient (nylon fabrics are heat-set)

Paved the way for easy-care garments

High resistance to insects, fungi, animals, as well as molds, mildew, rot and many

chemicals

Used in carpets and nylon stockings

Melts instead of burning

Used in many military applications

Good specific strength Transparent to infrared light (12dB)[3]

Bulk properties

Above theirmelting temperatures, Tm, thermoplastics like nylon are amorphous solids or

viscous fluids in which the chains approximate random coils. Below Tm, amorphous regionsalternate with regions which are lamellarcrystals.[4] The amorphous regions contribute
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elasticity and the crystalline regions contribute strength and rigidity. Theplanaramide (-

CO-NH-) groups are verypolar, so nylon forms multiple hydrogen bondsamong adjacent

strands. Because the nylon backbone is so regular and symmetrical, especially if all theamide bonds are in thetrans configuration, nylons often have high crystallinity and make

excellent fibers. The amount of crystallinity depends on the details of formation, as well as

on the kind of nylon. Apparently it can never be quenched from a melt as a completelyamorphous solid.

Hydrogen bonding in Nylon 6,6 (in mauve).

Nylon 6,6 can have multiple parallel strands aligned with their neighboring peptide bondsat coordinated separations of exactly 6 and 4 carbons for considerable lengths, so the

carbonyloxygensand amide hydrogens can line up to form interchain hydrogen bonds

repeatedly, without interruption (see the figure opposite). Nylon 5,10 can have coordinated

runs of 5 and 8 carbons. Thus parallel (but not antiparallel) strands can participate inextended, unbroken, multi-chain -pleated sheets, a strong and tough supermolecular

structure similar to that found in naturalsilk fibroin and the-keratins in feathers. (Proteins

have only an amino acid -carbon separating sequential -CO-NH- groups.) Nylon 6 willform uninterrupted H-bonded sheets with mixed directionalities, but the -sheet wrinkling

is somewhat different. The three-dimensional disposition of each alkanehydrocarbon

chain[disambiguation needed ] depends on rotationsabout the 109.47tetrahedral bonds of singlybonded carbon atoms.

When extrudedinto fibers through pores in an industrialspinneret, the individual polymer

chains tend to align because ofviscousflow. If subjected tocold drawingafterwards, the

fibers align further, increasing their crystallinity, and the material acquires additionaltensile strength.[5] In practice, nylon fibers are most often drawn using heated rolls at high

speeds.

Block nylon tends to be less crystalline, except near the surfaces due to shearingstresses

during formation. Nylon is clear and colorless, or milky, but is easily dyed. Multistrandednylon cord and rope is slippery and tends to unravel. The ends can be melted and fused

with a heat source such as aflameorelectrode to prevent this.
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When dry, polyamide is a good electrical insulator. However, polyamide is hygroscopic.

The absorption of water will change some of the material's properties such as its electrical

resistance. Nylon is less absorbent than wool or cotton.

Historical uses

The worn out nylon stockings will be reprocessed and made into parachutes for army fliers

c. 1942

Bill Pittendreigh, DuPont, and other individuals and corporations worked diligently during

the first few months ofWorld War II to find a way to replace Asian silkand hemp withnylon inparachutes. It was also used to make tires,tents,ropes,ponchos, and othermilitary

supplies. It was even used in the production of a high-grade paper for U.S. currency. At the

outset of the war,cotton accounted for more than 80% of all fibers used and manufactured,

and wool fibers accounted for nearly all of the rest. By August 1945, manufactured fibershad taken a market share of 25%, at the expense of cotton.

Some of the terpolymers based upon nylon are used every day in packaging. Nylon has

been used formeat wrappings and sausage sheaths.

[Use in composites

Nylon can be used as the matrix material incomposite materials, with reinforcing fibers

like glass or carbon fiber; such a composite has a higherdensity than pure nylon. Such

thermoplastic composites (25% glass fiber) are frequently used in car components next to

the engine, such as intake manifolds, where the good heat resistance of such materialsmakes them feasible competitors to metals.

Hydrolysis and degradation

All nylons are susceptible to hydrolysis, especially bystrong acids, a reaction essentiallythe reverse of the synthetic reaction shown above. Themolecular weightof nylon products

so attacked drops fast, and cracks form quickly at the affected zones. Lower members of

the nylons (such as nylon 6) are affected more than higher members such as nylon 12. Thismeans that nylon parts cannot be used in contact with sulfuric acidfor example, such as the

electrolyte used in lead-acid batteries. When being molded, nylon must be dried to preventhydrolysis in the molding machine barrel since water at high temperatures can also degradethe polymer. The reaction is of the type:
http://en.wikipedia.org/wiki/Hygroscopichttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Bill_Pittendreighhttp://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/Silkhttp://en.wikipedia.org/wiki/Hemphttp://en.wikipedia.org/wiki/Parachutehttp://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Tenthttp://en.wikipedia.org/wiki/Tenthttp://en.wikipedia.org/wiki/Ropehttp://en.wikipedia.org/wiki/Ropehttp://en.wikipedia.org/wiki/Ponchohttp://en.wikipedia.org/wiki/Armed_forceshttp://en.wikipedia.org/wiki/Currencyhttp://en.wikipedia.org/wiki/Currencyhttp://en.wikipedia.org/wiki/Cottonhttp://en.wikipedia.org/wiki/Cottonhttp://en.wikipedia.org/wiki/Woolhttp://en.wikipedia.org/wiki/Meathttp://en.wikipedia.org/wiki/Sausagehttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Densityhttp://en.wikipedia.org/wiki/Strong_acidhttp://en.wikipedia.org/wiki/Strong_acidhttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Sulfuric_acidhttp://en.wikipedia.org/wiki/Sulfuric_acidhttp://en.wikipedia.org/wiki/Lead-acid_batterieshttp://en.wikipedia.org/wiki/Hydrolysishttp://en.wikipedia.org/wiki/File:Amide_hydrolysis.svghttp://en.wikipedia.org/wiki/File:The_worn_out_nylon_stockings_in_this_barrel_full_of_salvaged_stockings_will_be_reprocessed_and_made_into_parachutes..._-_NARA_-_196427.jpghttp://en.wikipedia.org/wiki/Hygroscopichttp://en.wikipedia.org/wiki/Materialhttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Electrical_resistancehttp://en.wikipedia.org/wiki/Bill_Pittendreighhttp://en.wikipedia.org/wiki/DuPonthttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/Silkhttp://en.wikipedia.org/wiki/Hemphttp://en.wikipedia.org/wiki/Parachutehttp://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Tenthttp://en.wikipedia.org/wiki/Ropehttp://en.wikipedia.org/wiki/Ponchohttp://en.wikipedia.org/wiki/Armed_forceshttp://en.wikipedia.org/wiki/Currencyhttp://en.wikipedia.org/wiki/Cottonhttp://en.wikipedia.org/wiki/Woolhttp://en.wikipedia.org/wiki/Meathttp://en.wikipedia.org/wiki/Sausagehttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Densityhttp://en.wikipedia.org/wiki/Strong_acidhttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Sulfuric_acidhttp://en.wikipedia.org/wiki/Lead-acid_batterieshttp://en.wikipedia.org/wiki/Hydrolysis


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Incineration and recycling

Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash,

typically containing hydrogen cyanide.Incineratingnylons to recover the high energy usedto create them is usually expensive, so most nylons reach the garbage dumps, decaying

very slowly.[6] Some recycling is done on nylon, usually creating pellets for reuse in theindustry.[7]

MAKING OF NAYLON

Of course, there are a few more details to the reaction than you see up there in that

little picture.

To make nylon 6,6 on doesn't needa catalyst, but acids do catalyze the reaction, and

wouldn't you know it, one of the monomers is itself an acid. A little reaction happens

between two adipic acid molecules. One will donate a proton to a the carbonyl oxygen

of another.
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.

When this oxygen is protonated the carbonyl oxygen becomes much more vulnerable

to attack by the nitrogen of our diamine. This happens because our protonated

oxygen bears a positive charge. Oxygen does not like to have a positive charge. So it

pulls the electrons it shares with the carbonyl toward itself. This leaves the carbonyl

carbon lacking electrons, and ready for the amine nitrogen to donate a pair to it:


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Clickhere to see a movie of this reaction.

Then the electrons play musical chairs. One of the electron pairs form the carbonyl

double bond shifts entirely to the oxygen, taking care of the problem of the positive

charge at that atom, but now our nitrogen has a positive charge.
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Clickhere to see a movie of this reaction.

So then we get an even more elaborate game of electron musical chairs. The electrons

from the hydrogen oxygen bond go back to the oxygen, freeing the proton,

regenerating the acid catalyst. Then the carbonyl oxygen shares its newly regained

electrons with the carbon atoms, regenerating the carbonyl double bond.

Of course, this isn't enough. The oxygen of the hydroxyl group decides to do a little bit

of electron shuffling of its own. It takes the pair it shares with the carbon and hogsthem to itself, severing the bond between it and the carbon. It then donates a pair of

electrons to a hydrogen connected to the nitrogen.

That gets this hydrogen thinking. As it now shares a pair of electrons with the oxygen,

it sees no need to keep the pair it shares with the nitrogen, so it lets go of that pair,

giving it over to the nitrogen. This shift of electrons breaks the bond between the
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hydrogen and the nitrogen, and gets rid of the positive charge on that nitrogen. It

splits off H2O, and generates the amide-containing dimer.

So what does this dimer do? Look close, and you'll see that it has an acid group at one

end, and an amine group at the other. This means that it can react with a molecule of

the diacid, or a molecule of the diamine. Either way, you get a trimer.


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Wanna know a little secret? Our dimer can also react with other dimers, to make a

tetramer if it wants to. Or it can react with a trimer to form a pentamer, and it canalso react with bigger oligomers. Eventually, when this happens, dimers will grow into

trimers, tetramers, and bigger oligomers, and these big oligomers will react with each

other, to form even bigger oligomers. This keeps happening until they become big

enough to be called polymers.

For the molecules to grow big enough to be called polymers, we have to do this

reaction under a vacuum. When we do this, all that by-product water will evaporate


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and get sucked away. We need to get rid of the water because of a little rule calledLe

Chatelier's Principle.

Now remember how at the beginning of this little lesson I said that the reaction

doesn't needan acid catalyst to take place? The reason we know this is that near the

end of the polymerization, when there aren't many acid groups left to be catalysts, thereaction still goes on. You see, the amine can react with the unprotonated carboxylic

acids. If this were not so, high molecular weight nylon 66 could not be made without

an external catalyst, because the reaction would stop at higher conversions, when

there aren't many acid groups left to be catalysts.

Wanna know something else?

Nylons can also be made from a diamine and a diacid chloride:

This reaction goes by the same mechanism, but you need to add a little bit of acid to

act as a catalyst. (When you make nylon the other way, adipic acid acts as the

catalyst.) Also, it produces HCl gas as a byproduct rather than water.
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Production Process Pall Recommendations

Nylon 66 fibers for use in textiles, carpet, 1. HexamethyleneDiamine and 5. For the Ti02 slurry in water,

and tire cord are produced by extruding Adipic Acid -

Ultipor GF Plus Profile II cartridge grades RF100

molten polymer through spinnerets and grade U2-20Z isrecommended for to RF200 (rated 10-20 m

stretching to their final thickness and this feedstream forpromoting an absolute) are recommended for

weight. efficient nylon salt reaction.

nylon 66 manufacture. The make

up water should also be filtered

2. Water feed to the nylon salt

The polymer melt must be homoge-with Ultipor GF Plus grade U010Z


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reactor should be filtered with

neous, gel free, and without oversizebefore mixing with Ti02 . Filtration of

Ultipor GF Plus grade U2-20Z

additive agglomerates to achieve highTi02/water slurry stops passage of

cartridges to remove harmful

quality fiber and yields. Filtration of thelarge particles which could reduce

minerals that will contaminate the

process feedstreams, additive slurries,the tensile strength and quality of

and polymer melt itself are essential to nylon saltintermediate. the finished fiber.

help eliminate fiber breaks and enhance 3./4. For the nylonsalt solution a Pall

6. The final nylon 66 polymer

fiber strength and uniformity. Not only is Rigimesh gradeK backwash filter

transfer line" filter typically

fiber quality improved, but production is recommended ifcontaminant

consists of high pressure pleated

rates can be higher with less process concentrationlevels are high,

PMF elements 10-40 m


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downtime. followed by an Ultipor GF Plus

depending on the denier fiber being

grade U2-20Z polishing filter.These

produced. For the finest denier

filters remove extrinsic particulate

nylon fiber grade FH100 10 m

contamination such as iron oxides

absolute is recommended. PMF

and other debris which will reduce

elements ensure superior quality

polymerization efficiency and fiber

nylon fiber, and the ability to spin at

quality.

Properties

nylon 66 is a semi-crystalline engineering thermoplastic with universal

applications.

The main characteristics of Nylon 66 are:

It has good sliding properties

Is very abrasion resistant

Resistant to many oils, greases, diesel, petrol, cleaning fluids

Strong and tough

Rigid


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Electrically insulating

Easily machined

Easily welded and bonded

The preferred fields for the use of Nylon 66 are: mechanical engineering,

automotive

engineering, transport and conveyor technology, textile, packaging and

paper processing

machinery, printing and drinks dispensing machinery, household articles,

electrical

engineering, building machinery, and agricultural machinery

Popular applications for the use of Nylon 66 are:

Gear wheels

Friction strips

Bushes, spindle nuts

Piston guides Castors

Impact plates

Friction bearings

Conveyor screws

Cam discs

Rope pulleys

Plug parts

Damping plates

Popular applications for the use of Nylon 66 are:

Gear wheels

Friction strips

Bushes, spindle nuts

Piston guides Castors

Impact plates

Friction bearings

Conveyor screws

Cam discs

Rope pulleys


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Plug parts

Damping plates


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Production for nylon


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The chips ofnylon polymer are fed through a hopper A, into a spinning vesselB, on an electrically heated grid ( perforated plate) C. The

perforations are so small that the chips do not pass through, butwhen melted, the liquid can pass.

The molten nylon collects as a pool D, at the bottom of thevessel. This liquid should not come into contact with oxygen orair and hence nitrogen is introduced into the vessel. The moltenpolymer is kept at a temperature of about 288 deg C and suckedby a pump F, into a spinnerette E. The molten polymer solidifiesas soon as it emerges out of the spinnerette. The filament thusformed pass through a colloing zone, in which cold air G

circulates directed towards the filaments. The filaments are thenpassed through a steam chamber H, to wet them before windingon the bobbin L.

Drawing

Nylon filaments as obtained are not very strong. They have to tbedrawn 4-7 times their original length. This is done by cold
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drawing. The yarn in pulled off from bobbin L through guides Mand N, between a pair of rollers O. The speed of rotation of theserollers determines the initial speed. The yarn then goes over adeflector P, and two to three times around roller Q, running atfive times the speed than that of O. The yarn subsequently

courses through another guide R, and wound on another bobbinwhich rotates at very high speed, to impart twist in the yarnbefore being wound. Manufacturing Process of Nylon 6

Manufacturing Process of Nylon 6

Nylon Manufactured in India at present is of this type. This is made from Caprolactum

which is made by a series of reactions using products obtained from coal tar

Coal Tar--> Benzene--Chlorine--> Chlorobenzene--> Sodium Phenate--HCL--> Phenol--

H2 (Nickel)-->Cyclohexanol--Oxidation Air Fe, Zn Catalyst--> Cyclohexanone-->Cyclohexanone Oxime--H2SO4--> Caprolectum

Polymerisation

Caprolectum is a white flaky solid, melting at 68 deg C and is soluble in water. the

polymerisation is carried out in stainless steel cylinders.

Hot Caprolectum is mixed with a suspension of pigment, acid promotor and acid chain

stopper. The extent of polymerisation depends upon the temperature of polymerisation. The

purpose of acid chain stopper is to stop furthur polymerisation so that a desired density ofmolten polymer may be obtained.

The molten polymer is extruded into ribbons and cut into chips. These chips are used for

the production of continuous filaments.

Melt Spinning

Continuous filaments are made by melt spinning. Dry polymer chips are fed to a melt

spinning apparatus, wherein one section of the chips fall, into a melting region where they

are heated electrically to 250-260 deg C. The molten polymer flows into a conical sectionto form a pool, which feeds a spinning pump and spinnerette. The pool is kept under an

atmosphere of nitrogen to prevent decomposition by air.

The molten polymer leaving the pump is filtered before entering the spinnerette which is a

stainless steel disc having a number of holes, the number and diameter of which determine

the type of yarn formed. Before reaching the machine in which cheese is build up, the

filaments are moistened with water to ensure dimensional stability of the final packages.

The yarn thus formed is not strong enough and has a very high extensibility. the yarn

contains a large number of macro molecules which are unoriented and these must be


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oriented so as to lie parallel to the length of the fibre to develop full strength. This is done

by stretching the yarn to 3-4 times its original length.

Engineering Plastic Grade


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SpecificationApplication Product Features

Luster R.V. Lot.no.

BR

low 2.45 N-140

compoundingGood mechanical properties, excellent impact

properties

Big surface hardness, small friction coefficientGood electricity properties, anti-low

temperature properties

Good chemical resistance,and oil resistance

middle2.71 N-150

compounding

high 3.3

N-180

compounding

N-190BOPAfishnettire cord

Spinning Grade

SpecificationApplication Product Features

Luster R.V. Lot.no.

BRlow 2.45

N-130 FDY

MOYHOYATY

Good quality stabilityGood evenness of molecular arrangment,

low variation rate

Low oligomer, low yarn breakage rate

SD N-131

FD N-136

BR middle2.71 N-160

carpet yarnhigh tenacity

yarn

Properties

PurposeSpecific

(Spec.)

Viscosity

(R.V.)

Moisture (ppm) Extraction (%) TiO2(%) NH2 - (meq/kg)

For spinningBR

2.45 800 0.60 abt. 45

SD 0.3 abt. 40

FD 1.6 abt. 45

High Tenacity BR 2.71 800 0.6 0 abt. 35High Tenacity

& FilmBR 3.30

4000.6 0 abt. 39

800

For engineering BR2.45

1000 0.6 0abt. 45

2.71 abt. 35

3.30 abt. 39

The detail specification list for engineering plastic grade nylon chip

1. for High Tenacity yarn & Film N160,N190,N2002. for compounding N140 ,N150 ,N180

Characteristics strength

1. Great degree of polymerization concentrated molecular weight distribution,

suitable for high speed spinning.
http://www.libolon.com/download/N160.pdfhttp://www.libolon.com/download/N160.pdfhttp://www.libolon.com/download/N190.pdfhttp://www.libolon.com/download/N190.pdfhttp://www.libolon.com/download/N200.pdfhttp://www.libolon.com/download/N140.pdfhttp://www.libolon.com/download/N150.pdfhttp://www.libolon.com/download/N180.pdfhttp://www.libolon.com/download/N160.pdfhttp://www.libolon.com/download/N190.pdfhttp://www.libolon.com/download/N200.pdfhttp://www.libolon.com/download/N140.pdfhttp://www.libolon.com/download/N150.pdfhttp://www.libolon.com/download/N180.pdf


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2. Superior quality low monomer contamination, great polymer purity.

3. Good thermal stability minimum degradation caused by heat, resistant against

etiolation and deterioration.

4. Great packaging quality moisture and sunlight proof to ensure product quality.

Packing

1. Package type

Package Large Small

Weight (kg) 800 820 25

2. Container type

ContainerLarge Small

800kg 820kg W/pallet Wo/pallet

20 ft . 20 20 600 720

Engineering Plastic Grade (RePET-P)

Properties

For 3C applications

Spec. Method Unit Status LL-Re-PET-1flowability ASTM D1238 g/10min 260 2.16 kg 23

sp.gr. ASTM D792 1.2

moisture% ASTM D570 % 0.4Tensile strength ASTM D638 Kg/cm2 575

Enlongation ASTM D638 % 180

Bentch strgngth ASTM D790 Kg/cm2 950Bentch moldulus ASTM D790 Kg/cm2 34500


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IZOD impact strength ASTM D256 Kgcm/cm 85

Heat Defect temperature ASTM D648 80

Soften temperature ASTM D1525 105linear thermal

expansion coefficient ASTM D696 10-5 cm/cm/ 5~7

shrikage ASTM D955 % 0.4~0.6FR property UL94 - 1.5mm V0

1. Recycle PET and PA6 are major additives in composite product applications2.Expected mechanical properties are slightly lower with respect to vergin ones.

3.Test results are only references for applications, real parameters are depended on

manufacturing equipments possessed by customers.


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Structure

8.1 Introduction

Objectives

8.2 Manufacturing Process of Nylon Filaments

Nylon 6

Nylon 6,6

8.3 Characteristics of Nylon Fabrics

8.4 Summary

8.5 Terminal Questions

8.6 Answers

8.1 Introduction

The synthetic fibres also called as chemical fibres are the synthesised polymers, which are

not found in nature. There are different types of synthetic fibres of which the

manufacturing process of nylon is discussed in this unit. Nylon is the first man madesynthetic fibre (pure chemical fibre).


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As defined by the Federal Trade Commission (FTC), nylon is a long chain synthetic

polyamide in which less than 85 per cent of the amide linkages are attached to two

aromatic rings.

Objectives

After studying this unit, you would be able to:

explain the manufacturing process of nylon fibres.

discuss the different properties of nylon fibres.

8.2 Manufacturing Process of Nylon Filaments

The two varieties of nylon, which are used for apparel purposes which include Nylon 6 andNylon 6,6. Nylon 6 is made from one monomer (Caprolactum) containing 6 carbon atoms.

Nylon 6,6 is made from hexamethylene diamide and adipic acid which has six carbonatoms each.

8.2.1 Manufacturing Nylon 6

The raw material for manufacturing Nylon 6 is coal.

Cyclohexane oxime is produced by a series of chemical reactions on coal.

Cyclo heaxaneoxime is then treated with sulphuric acid to form caprolactum.

The caprolactum is a monomer with 6 carbon atoms that are polymerized to from chainsof caprolactum. Polymerization is done by gently heating it in a steam jacked stainless

steel vessel. The solution is stabilised as a super polymer under constant steam andpressure.

Nylon may be delustered by adding the delustering agents like titanium di oxide, barium

sulphate, zinc oxide, and zinc sulphate.

The molten nylon 6 polymer is allowed to flow onto a slowly revolving casting wheel.

These are sprayed with cold water, which hardens it into milky white ribbons.

The ribbons are transformed into flakes that are sent for spinning and are then drawn into

the fibre form.


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Spinning of nylon 6:

The spinning of the nylon fibres is carried out with melt spinning. There are two methods

of melt spinning:

grid spinning

extruder spinning.

Grid spinning is employed for the production of finer filaments.

The nylon flakes are made to fall on a hot grid that melts the nylon flakes.

The molten nylon is pumped through a sand filter to the spinneret. The type of filament

produced depends upon the number of holes on the spinneret, the size and the shape of the

holes.

The molten nylon as extruded from the spinneret solidifies and forms filaments asexposed to the air.

Extruder spinning is generally used for heavier yarns.

The nylon chips flow by gravity into a device that forces them by screw action through

the heated zones.

The combined action of the heat and screw pressure melts the chips.

The molten polymer is then extruded through the spinneret, which solidifies when the

polymer comes in contact with the air.

Drawing:
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The filaments obtained from spinning are stretched by drawing process. The drawing

process is accomplished in two stages:

unwinding the yarn from one godet, or wheel,

winding it onto another godet that is rotating much faster. The speed of the second wheeldetermines the amount of cold-drawing or stretching.

The yarn from the second godet is wrapped on a cylindrical tube called a pirn.

The filaments can be stretched from 2 to 7 times their original length. The molecules in the

filament structure straighten out, become parallelized, and are brought very close together.

8.2.2 Manufacturing Nylon 6,6

The manufacturing process starts with the production of two chemicals hexamethylene

diamine and adipic acid both of which contains 6 carbon atoms from coal.

These chemicals are combined to form the nylon salt, which is dissolved in water and sent

to the spinning mill.

The nylon salt solution is made into a concentrated solution by heating in largeevaporators.

The concentrated solution is then heated in an autoclave under the pressure and

temperature. The polymerization takes place combining the two chemicals into polymers

which are like a giant chains.

The molten polymer is processed in a manner similar to nylon 6.

The flow chart is as follows:


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The symbolic representation of the manufacturing process of nylon 6 and nylon 6,6 is

given in figure 8.1:

Figure 8.1: Manufacturing Process of Nylon 6 and Nylon 6,6

Self Assessment Questions

1. Caprolactum is a monomer consisting of ____ carbon atoms.

2. ______ spinning is employed for nylon filaments.

3. ______ and _____ combine to form nylon salt.

4. Grid spinning is meant for ____ yarns.

8.3 Characteristics of Nylon Fabrics

Nylon is very much suitable for hosiery and the knitted fabrics because of its smoothness,

light weight and high strength. Nylon is a lustrous fibre. The lustre of the fibre can bemodified by adding the delustering agent at the molten stage.

Composition: The nylons are polyamides with recurring amide groups. They contain

carbon, oxygen, nitrogen and hydrogen elements.

Strength: Nylon has good tenacity and the strength is not lost with age. Nylon has a highstrength to weight ratio. It is one of the lightest textile fibres is at the same time also one of

the strongest. It is one of the fibres which are added at the points of wear such as knees and
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seats of jeans and toes and heels of socks. The strength of the nylon fabric is lost when wet.

Nylon has excellent abrasion resistance.

Elasticity: Nylon has good elasticity which makes it much suitable for the apparelpurposes. The excellent elasticity would mean that the nylon materials return to their

original length and shreds the wrinkles or creases. Nylon like other fibres has its own limitof elasticity. If stretched too much, it will not completely recover its shape. The high

elongation and excellent elastic recovery of nylon contributes to the outstandingperformance in hosiery. Nylon hosiery recovers to its original shape at knees and ankles

instead of bagging.

Resilience: Nylon fabrics have excellent resilience. Nylon fabrics retain their smoothappearance and the wrinkles from the usual daily activities can be removed easily.

Drapability: Fabrics of nylon filament yarn have excellent draping qualities. The drape of

the fabrics made from nylon can be varied depending on the yarn size. The light weight

sheer fabrics of nylon night gowns have high-draping quality. The medium-weight dressfabrics can drape very nicely.

Heat Conductivity: The heat conductivity of the nylon fabrics vary depending upon the

fabric construction, the type of nylon (staple/filament) used in the construction etc. For

instance, the filament nylon used in the open construction would be cooler when comparedto the same filament used in a closed construction. In a closed or tight construction the air

circulation through the fabric is limited. The heat and moisture of the body will not readily

pass the fabric construction, which makes the wearer feel very warm. Such fabrics are goodfor winter apparel, such as wind-breakers, but are not suitable for summer garments. On the

other hand the fabrics with open construction permits the air circulation which makes the

wearer feel cool.

Absorbency:Nylon fabrics have low absorbency. The low absorbency of the fabrics tendsto be advantageous and also disadvantageous. The main advantage of the nylons low

absorbency is that the water remains on the surface of the fabrics and runs off the smooth

fabric and hence dries quickly. This property makes the nylon fabrics suitable for raincoats

and shower curtains. Nylons low absorbency has a disadvantage in that the fabric feelsclammy and uncomfortable in warm, humid weather.

Cleanliness and Washability: Nylon fabrics are easy care garments. Nylon fabrics are

smooth, non-absorbent and dry quickly. Dirt doesnt cling to this smooth fibre, which can

be washed easily or can be even cleaned by using a damp cloth. Nylon whites arecommonly referred as colour scavengers and should be washed separately to avoid greying.

They easily pick up colour and dirt from the wash water. Nylons, washed with other fabrics

pick up colour (even from the palest pastels) and develop a dingy grey appearance that isextremely difficult to remove. In addition to retaining their appearance during wear,

garments made from nylon fabrics retain their appearance and shape after washing. Hot

water should be avoided during washing as the hot water may cause wrinkling in somefabric constructions.


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Effect of Bleaches: The nylon fabrics are white and generally do not require bleaching.

The nylon fabrics which pick up colour or develop greying should be bleached with

oxidising bleaches such as hydrogen peroxide.

Shrinkage:Nylon fabrics retain their shape and appearance after washing. It has good

stability and does not shrink.

Effect of Heat:Nylon should always be ironed at low temperatures. Using hot iron will

result in glazing and then melting of the fabric.

Effect of Light:Nylon fabrics have low resistance to sun light. They are not suitable forcurtains or draperies as it is weakened by the exposure to sun light.

Resistance to Mildew:Nylon fabrics have absolute resistance to the development of

mildew.

Resistance to Insects:Nylon is resistance to the moths and fungi.

Reaction to Alkalis:Nylon has excellent resistance to alkalis but the frequent andprolonged exposures to alkalis will weaken the nylon fabrics.

Reaction to Acids:Nylon is less resilient to the action of acids and is damaged by strong

acids.

Affinity for Dyes:Nylon can be easily dyed with a wider range of dyes. The dyed fabricsretain their colour and have good resistance to fading.

Resistance to Perspiration:Nylon fabrics are resistant to perspiration.

Processing Nylon Yarn

The nylon material that ACES is made of was probably processed differently from what is

used in commercially sold synthetic strings. For one, we used individual nylon threads that

were already a bundle of twisted single nylon filaments to make our core rather than asingle monofilament or straight multifilaments. These threads were most likely

manufactured through a melt spinning process, as is more often used for polyamides, such

as nylon, that melt at or below 280 C because it is more economical. [3] The main steps inthis process include taking molten polymer, passing it through a filter and spinnerette,

quenching the molten filaments, converging the filaments into yarns, and finally drawingthe yarn to achieve certain properties for specific end use. (see Figure 1 below) Each step in

the process has many variables that can be changed to affect the time and costs of themanufacturing process.


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Figure 1 - Melt spin-draw processes for nylon yarn (a) draw-twist process, (b) conventionalspinning process, and (c) coupled process. [3]

Obtaining molten polymer

In the first commercial processes, the molten polymer was obtained by melting polymer

chips sealed in a hopper under nitrogen pressure. The chips would flow by gravity into apancake coil heated to temperatures in the 300 C range. Extruders can also be used to melt

polymer chips. Nowadays, however, more efficient spinning machines have been made that

combine the polymerization process of nylon directly with the spinning machine toeliminate the use of polymer chips. [3]

Passing through filter and spinnerettePrecisely metered amounts of the polymer must be passed through the filter and delivered

to the spinnerette. This is achieved by using a metering pump to discharge exact volumesof molten polymer per unit time. The molten polymer passes through a filter which uses

high shear to remove gel particles and particulate matter that can clog spinnerette holes.

The filtration-shear devices have been made with layers of sand of different grain sizes, butnow specially designed screens and sintered metal are replacing the sand. The spinnerettes

can have anywhere from 500 to 4000 holes per disk to produce the molten filaments. [3]


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Spin-Draw Process

After going through the spinnerette, the molten filaments are air-quenched in a vertical

chimney and converged into a yarn. The yarn is usually spun onto bobbins that can hold 10to 25 kg of yarn per bobbin and can operate up to 6000 m/min. Usually there are two or

more bobbins per winder, and spare winders can switch over rapidly to a new roll to avoid

yarn loss. Often the yarn is spun onto bobbins at 300-3000 m/min and then lagged to betaken to a draw-twisting operation as seen in Figure 1a. The degree of drawing or

stretching can be controlled by changing the speed of the draw rolls, which run faster than

the feed rolls. The spinning and drawing steps have now been combined into a single stepthrough the development of high speed drawing, winding technology, and air jet

interlacing. (see Figure 1c)

The polymer melt viscosity, spinning speed, cooling rate, and the fiber's degree of

structural orientation all effect the tensile strength of the fiber, however, the spinning anddrawing step of the string manufacturing process probably has the largest effect on the final

properties of the fiber. The yarns can be drawn between approximately 130% to 600 %,

which increases tensile strength, lowers elongation, and more oriented crystallization.Orientation can also be controlled by spin spped. Low orientation yarns (LOY) can be

made that have a high residual drawing, low crystallinity, and limited storage stability.

Medium oriented yarns (MOY) are processed at 1800-2800 m/min. so are slightly more

crystalline, but still have limited storage stability. At spinning speeds of 4000-6000 m/min.,highly oriented yarns (HOY) are made, while fully oriented yarns (FOY) can be produced

with speeds of well over 6000 m/min. FOY have elongations of 20-30%, similar to the

strains of the nylon threads that we used and tested. [3]

Processing Kevlar Yarn

Kevlar, or poly(p-phenylene terephthalamide) (PPTA), is an aromatic polyamide that has ahigh melting point, which does not allow it to be processed in the melt-spin method

described for nylon. Instead the polymer is sent to the spinning process from a solution of

PPTA and sulfuric acid. The patent literature describes a spinning process in which PPTA

is dissolved in 98-100% sulfuric acid at a concentration of greater than 18%. The solutionis pumped through a spinnerette, and then into an aqueous bath that quenches the filaments.

Finally, the fiber is washed thoroughly with water and dried. [4]

Constructing ACES

After obtaining our nylon and Kevlar strings from McMaster-Carr, we proceeded toconstruct our tennis string. The method we finally decided on was based on the processused to make bowstrings. (see figures below) A bowstring jig was constructed, which we

used to hold four nylon strands under a tension of about 10-20 lbs to keep the threads taut.

We then used a server jig with a reel of Kevlar on it to wrap the nylon threads.

The resulting string resembles a rope more than it does a conventional synthetic string,both in appearance and fracture behavior.


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Figure 2 - Bowstring jig.


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Figure 3 - Server jig used for wrapping process.

nylon is a thermoplastic

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