Delhi Public School VaranasiChemistry Investigatory Project

Topic: Study the effect of acids and bases on tensile strength of fibers.

Yash KesharwaniRoll No. - 28

Index

Acknowledgement Certificate Introduction Materials required Procedure Observation table Result Precautions Bibliography

Acknowledgement

I have taken efforts in this project.However, it would not have been possiblewithout the kind support and help of manyindividuals. I would like to extend mysincere thanks to all of them.

I am highly indebted to Anju ma’am andNilanjana ma’am for their guidance andconstant supervision as well as forproviding necessary information regardingthe project and also for their support incompleting the project. I would like toexpress my gratitude towards my parentsfor their kind co-operation andencouragement which help me in completionof this project.

My thanks and appreciations also go to myfriends in developing the project andpeople who have willingly helped me outwith their abilities.

CertificateThis is to certify that YashKesharwani of class XII-D2 of DelhiPublic School Varanasi for academicsession 2014-2015, has prepared hischemistry investigatory project on thetopic allotted to him properly.I hereby certify that this project isprepared by the above mentionedstudent.

Mrs. Anju Singh Department of Chemistry

Delhi Public School Varanasi

FiberFiber is a natural or synthetic stringused as a component of compositematerials, or, when matted into sheets,used to make products such as paper,papyrus, or felt. Synthetic fibers can often be producedvery cheaply and in large amounts comparedto natural fibers, but for clothingnatural fibers can give some benefits,such as comfort, over their syntheticcounterparts.

Natural FibersNatural fibers include those producedby plants, animals, and geologicalprocesses and can be classifiedaccording to their origin:

Vegetable fibers are generally basedon arrangements of cellulose, oftenwith lignin: examplesinclude cotton, hemp, jute, flax, ramie,sisal, bagasse, and banana. Plantfibers are employed in themanufacture

of paper and textile (cloth),and dietary fiber is an importantcomponent of human nutrition.

Wood fiber, distinguished fromvegetable fiber, is from treesources. Forms include groundwood, lacebark, thermo mechanicalpulp (TMP), and bleached orunbleached kraft or sulfite pulps.Kraft and sulfite (also calledsulphite) refer to the type ofpulping process used to remove thelignin bonding the original woodstructure, thus freeing the fibersfor use in paper and engineeredwood products such as fiberboard.

Animal fibers consist largely ofparticular proteins. Instancesare silkworm silk, spidersilk, sinew, catgut, wool, seasilk and hair such ascashmere, mohair and angora, fur suchas sheepskin, rabbit, mink, fox,beaver, etc.

Mineral fibers includethe asbestos group. Asbestos is the

only naturally occurringlong mineral fiber. Six minerals havebeen classified as "asbestos"including chrysotile ofthe serpentine class and thosebelonging tothe amphibole class: amosite, crocidolite, tremolite, anthophyllite and actinolite. Short, fiber-likemineralsinclude wollastonite and palygorskite.

Biological fibers also knownas fibrous proteins or proteinfilaments consist largely ofbiologically relevant andbiologically very important proteins,mutations or other genetic defectscan lead to severe diseases.Instances are collagen family ofproteins, tendon, muscleproteins like actin, cell proteinslike microtubules and manyothers, spider silk,sinew and hair etc.

Man-made FibersMan-made fibers or chemical fibers arefibers whose chemical composition,structure, and properties aresignificantly modified during themanufacturing process. Man-made fibersconsist of regenerated fibers andsynthetic fibers.

Semi-synthetic fibers Semi-synthetic fibers are made from rawmaterials with naturally long-chainpolymer structure and are only modifiedand partially degraded by chemicalprocesses, in contrast to completelysynthetic fibers suchas nylon (polyamide)or dacron (polyester), which thechemist synthesizes from low-molecularweight compounds by polymerization(chain-building) reactions. Theearliest semi-synthetic fiber is thecellulose regenerated

fiber, rayon. Most semi-syntheticfibers are cellulose regeneratedfibers.

Cellulose regenerated fibersCellulose fibers are a subset of man-made fibers, regenerated fromnatural cellulose. The cellulose comesfrom various sources: rayon from treewood fiber, Modal from beechtrees, bamboo fiber frombamboo, seacell from seaweed, etc. Inthe production of these fibers, thecellulose is reduced to a fairly pureform as a viscous mass and formed intofibers by extrusion through spinnerets.Therefore, the manufacturing processleaves few characteristics distinctiveof the natural source material in thefinished product.Some examples are:

rayon bamboo fiber Lyocell , a brand of rayon

Modal , using beech trees as input diacetate fiber triacetate fiber .Historically, cellulose diacetate and -triacetate were classified under theterm rayon, but are now considereddistinct materials.

Synthetic fibersSynthetic come entirely from syntheticmaterials such as petrochemicals,unlike those man-made fibers derivedfrom such natural substances ascellulose or protein.Fiber classification in reinforcedplastics falls into two classes: (i)short fibers, also known asdiscontinuous fibers, with a generalaspect ratio (defined as the ratio offiber length to diameter) between 20 to60, and (ii) long fibers, also known ascontinuous fibers; the general aspectratio is between 200 to 500.

Metallic fibersMetallic fibers can be drawn fromductile metals such as copper, gold orsilver and extruded or deposited frommore brittle ones, such as nickel,aluminum or iron. See also Stainlesssteel fibers.

Carbon fiberCarbon fibers are often based onoxydized and via pyrolysis carbonizedpolymers like PAN, but the end productis almost pure carbon.

Silicon carbide fiberSilicon carbide fibers, where the basicpolymers are not hydrocarbons butpolymers, where about 50% of the carbonatoms are replaced by silicon atoms,so-called poly-carbo-silanes. Thepyrolysis yields an amorphous siliconcarbide, including mostly otherelements like oxygen, titanium, oraluminium, but with mechanical

properties very similar to those ofcarbon fibers.

FiberglassFiberglass, made from specific glass,and optical fiber, made from purifiednatural quartz, are also man-madefibers that come from natural rawmaterials, silica fiber, madefromsodium silicate (water glass)and basalt fiber made from meltedbasalt.

Mineral fibersMineral fibers can be particularlystrong because they are formed with alow number of surfacedefects, asbestos is a common one.[8]

Polymer fibers

Polymer fibers are a subset of man-made fibers, which are based onsynthetic chemicals (often

from petrochemical sources) ratherthan arising from natural materialsby a purely physical process. Thesefibers are made from: polyamide nylon PET or PBT polyester phenol-formaldehyde (PF) polyvinyl chloride fiber(PVC) vinyon

polyolefins (PP and PE) olefinfiber

acrylic  polyesters,pure polyester PAN fibers are usedto make carbon fiber by roastingthem in a low oxygen environment.Traditional acrylic fiber is usedmore often as a syntheticreplacement for wool. Carbon fibersand PF fibers are noted as tworesin-based fibers that are notthermoplastic, most others can bemelted.

Aromatic polyamids  (aramids) suchas Twaron, Kevlar and Nomex thermally degrade at high temperatures anddo not melt. These fibers have

strong bonding between polymerchains

Polyethylene  (PE), eventually withextremely long chains / HMPE (e.g.Dyneema or Spectra).

Elastomers  can even be used,e.g. spandex although urethanefibers are starting to replacespandex technology.

polyurethane  fiber Elastolefin

Coextruded fibers have two distinctpolymers forming the fiber, usuallyas a core-sheath or side-by-side.Coated fibers exist such as nickel-coated to provide static elimination,silver-coated to provide anti-bacterial properties and aluminum-coated to provide RF deflectionfor radar chaff. Radar chaff isactually a spool of continuous glasstow that has been aluminum coated. Anaircraft-mounted high speed cutterchops it up as it spews from a movingaircraft to confuse radar signals.

MicrofibersMicrofibers in textiles refer to sub-denier fiber (such as polyester drawnto 0.5 denier). Denier and Dtex are twomeasurements of fiber yield based onweight and length. If the fiber densityis known, you also have a fiberdiameter, otherwise it is simpler tomeasure diameters in micrometers.Microfibers in technical fibers referto ultra-fine fibers (glass ormeltblown thermoplastics) often used infiltration. Newer fiber designs includeextruding fiber that splits intomultiple finer fibers. Most syntheticfibers are round in cross-section, butspecial designs can be hollow, oval,star-shaped or trilobal. The latterdesign provides more opticallyreflective properties. Synthetictextile fibers are often crimped toprovide bulk in a woven, non-woven orknitted structure. Fiber surfaces canalso be dull or bright. Dull surfacesreflect more light while bright tends

to transmit light and make the fibermore transparent.Very short and/or irregular fibers havebeen called fibrils. Natural cellulose,such as cotton or bleached kraft, showsmaller fibrils jutting out and awayfrom the main fiber structure.

Tensile StrengthOf Fibers

Depending upon the sources, the varioustypes of fibers can be classified into thefollowing main three categories:

Animal Fibers Vegetable Fibers Synthetic fibers

Besides their chemical composition andproperties, most important property ofthese fibers is their tensile strength,meaning the extent to which a fiber can bestretched withoutbreaking and it ismeasured in terms ofminimum weight requiredto break the fiber. Todetermine the tensilestrength of nay fiber, it is tied to ahook at one end and weights are slowlyadded to the other end until the fiberbreaks.

Since peptide bonds aremore easily hydrolyzedby bases than by acids,therefore wool and silkare affected by bases

and not by acids.

It is because of this reason that wool andsilk threads breakup into fragments andultimately dissolves in alkalines.

In other words,alkalines decreasethe tensile strengthof animal fibers(wool and silk),vegetable fibers(cotton and linen),

on the other hand, consist of longpolysaccharide chains in which the variousglucose units are joined by etherslinkage. Since ethersare hydrolyzed by acidsand not by bases,therefore vegetablefibers are affected byacids but not by bases.In other words, acidsdecrease the tensile strength of vegetablefibers. In contrast, synthetic fibers suchas nylon and polyester practically remainunaffected by both acids and bases.Synthetic fibers owe some of theirchemical resistance to their more

Procedure Cut out equal lengths of a cottonfiber, nylon fiber and silk fiber fromthe given sample.

Tie one end of cotton fiber to a hookwhich has been fixed in a verticalplane. Tie a weight hanger to the otherend. Let the thread get straight.

Put a weight to the hanger and observethe thread stretch. Then, increase theweights gradually on the hanger untilthe breaking point is reached. Thennote the minimum weight needed forbreaking the cotton fiber.

Repeat the above experiment by tyingnylon and silk fibers to the hookseparately and determine the tensilestrength of each fiber.

Soak the woolen thread in a dilutesolution of sodium hydroxide for fiveminutes. Take it out from hydroxide

solution and wash it thoroughly withwater and then dry by keeping it in thesun. Determine the tensile strengthagain.

Now take another piece of woolen threadof the same size and diameter and soakit in a diluter solution ofhydrochloric acid for five minutes.Take it out, wash thoroughly withwater, dry and determine the tensilestrength agin.

Repeat the above procedure for thesamples of cotton and nylon fiber.

Observation Table

S.No.TypeOfFibre

Wt. RequiredTo Break TheUntreated Fiber

Wt. Required ToBreak The FiberAfter Soaking InDil. HCl

Wt. Required ToBreak The FiberAfter Soaking InNaOH Solution

1. Wool

2. Cotton

3. Nylon

Result The tensile strength of woolen fiberdecreases in alkalies but practicallyremains unaffected on soaking in acids.

The tensile strength of cotton fiberdecreases on soaking in acids butremains practically unaffected onsoaking in alkalies.

The tensile strength of nylon fibersremain practically unaffected onsoaking either in acids or inalikalies.

Precautions

The threads must be of identicaldiameters.

The length of the threads should alwaysbe same.

The weights should be added in smallamounts very slowly.

The chemicals should be handled verycarefully.

BibliographyGoogle

Wikipedia

Britannica Encyclopedia

Materials &ChemicalsRequired

Weight Hanger &Weights

Hook

DiluteHydrochloric

Acid

SodiumHydroxideSolution

CottonSilk

Nylon