% "• * . .̂?

m

• ^ ^ : ;

m^

"•~.y.-, . - , .

IdX LCI

New Synthetic Fibers Come from Natural SourcesBy Maria C. Thiry, Features Editor

In the beginning, textile fiberscame from the natural world:animal skins, hair, and wool; silkfrom silkworms; and plants likea flax, cotton, and hemp. For

centuries, all textiles came from fibersthat were harvested fron:i a plant, ani-mal, or insect. Then, at the beginningof the 20th century, people discoveredthat they could create textile fibers oftheir own. Those early synthetic fibersstill originated in a natural source—cellulose from wood pulp—but soonenough in the 1930s, 40s, and 50s, astream of synthetic fibers came on thescene that owed their origins tochemical plants instead of plantsthat could be grown in a field.

Now at the beginning of the 21stcentury, the trend in fiber researchhas come full circle. While thepopularity of completely syntheticfibers remains high, in many casesattention is once again being fo-cused on synthetic fibers that comefrom natural sources.

STARTING THE (COnON) BALLROLLING

Once the king of fibers, cotton tex-tile fiber usage began to decline inthe 1960s and 70s with the growth

JANUARY 2004

of applications for synthetic fibersand their increasing popularity. Cot-ton producers decided to fight back.Cotton Incorporated's famous market-ing campaign is credited for bringingthe public's attention and loyalty"back to nature."

"Cotton is the original high-techfiber," says the company's MichelleWallace. The fiber's material proper-ties, such as moisture management,comfortable hand, and wet tensilestrength contribute to its appeal. Thedevelopment of various finishes hasgiven cotton fabrics additional favor-

able properties, such abrasion resis-tance, stain repellency, and wrinkleresistance. In addition, according toWallace, genetic research has gone intoimproving the quality of the fiber it-self—qualities such as increasedlength, and improved strength of thefiber over the last 30 years. "In themarketplace, it is important to have adifferentiated product," notes CottonIncorporated's Ira Livingston. "We arecontinually looking for ways to intro-duce cotton that surprises the con-sumer. One of those ways is our re-search into biogenetics, to enhance

75%

61%

Percent

Cotton's Share of MarketApparel & Home Fabrics

^1961-75 Trend ^Cotton'B Share

Sourca: NPD and Traife Data* Endudn Caipat

Cfta/? courtesy of Cotton Incorporated, Used with permtssior}.

VVWW.AATCC.ORG

Photos courtesy of Fred Neal and South West Trading Co. Usedwith permission.

cotton and to keep it a brand new6000 year old fiber."

Cotton's resurgence has awakenedresearchers to the appeal of naturalfiber sources. As well as being a re-newable resource and biodegradable,cotton fibers also have material prop-erties that are appealing. And CottonIncorporated's marketing has ensuredthat the marketplace is receptive totextiles made from natural fibersources. "We brought the consumerback to a 'natural state of mind' withover 30 years of communication,"notes Livingston. "This has opened upopportunities for other natural-basedfibers."

BIOPROSPECTING

Natural fibers are either plant (cellu-lose) or animal (protein) based. Ac-cording to Anil Netravali of CornellUniversity, 'There are a lot of plantswe haven't looked at yet," for textilefibers. His group is researching themanufacture of composites usingfibers from various plant sources,such as flax, ramie, pineapple, jute,banana, bamboo, sisal, hemp, andkenaf.

Other groups are promoting soyfiber, made from the waste productsof the soybean industry. "Soy fiber isa rediscovered product that has manyuses," says Barb Keeling of Keeling'sKrafts, who uses soy fiber in her dollmaking business. She notes that thefiber has been around a long time, andis only now seeing a resurgence ofinterest. "Henry Ford talked of soyfiber in the 1940s. He even had a suitand tie made from woven soy fibers."

AATCC REVIEW

Jonelle Raffino of South West TradingCo., who markets soy yarns under thetrade name of Soy Silk, feels that themarketplace will be very receptive tothis fiber. "Consumers are demandingnew ideas and smart ideas. Soy tlbersatisfies the consumer on a lot oflevels—it is fabulously soft, reason-ably priced, and appeals to the aware-ness of environmental issues."

Cargill Dow went back to basicswhen they developed polylactic acidfiber (PLA) that they market as Ingeo."PLA was the first generic fiber regis-tered by the U.S. Federal Trade Com-mission in almost 50 years." notesCargill Dow's Joe Raffo. PLA fibersare made using lactic acid as the basisfor the polymer. The lactic acid comesfrom fermenting natural sugars orstarches. Ingeo is manufactured usingfeed corn, but Cargill Dow is develop-ing a way to use the com stalks—apart of the plant usually considered awaste product. Otherresearchers are look-ing into using ricestarch to manufac-ture PLA. Sustain-able PLA fibermanufacturing fromwaste plant materialis an exciting ideafor many. Accordingto Nexia Biotech'sAli Alwattari. "Thepotential to makefiber from wastebiomass ... couldcreate big, renewable

feed stocks of high value fiber that do- >not drain the environment and '^^from multiple rather than singh ^sources."

As well as the plant world, the <. "̂ alkingdom contains many more pro-"iiisources for fibers that have yet lo beexploited. One of these is chitin, fromthe waste products of the shellfish indus-try. According to Sam Hudson of NorthCarolina State University, "Chitin isconsidered the second most plentifulrenewable resource on earth, after cellu-lose." The shellfish waste is treated toextract the chitin, like wood chips aretreated to extract cellulose fibers in rayonproduction. "We have known aboutchitin for many years." explains Hudson."It was first chemically identified in theearly 1800s, but in the last 10-15 years,interest has been picking up."

Another "hot" area of fiber researchis spider silk. "Spiders have evolved atoolkit of as many as seven types ofsilks that they use to construct webs.With over 37.000 described species ofspiders on the planet and all them pro-ducing silk, this makes for a wealth ofopportunities for fiber researchers tobioprospect." says the University ofCalifornia—Riverside's ToddBlackledge.

INTRIGUING POSSIBILITIES

For researchers, the allure of these newfiber sources lies not just in their avail-ability or sustainability. but in theirintriguing material properties and pos-sibie applications. "Chitosan (.the fiberform of chitin) is not as strong a fiberas cotton or nylon. It is* also sensitive to

JANUARY

acidity—it can dissolve in an acidsolution (vinegar can turn it into agel). It is also too expensive tomanufacture to compete with rayonas a commodity fiber. However, it isan excellent special purpose fiber formedical applications," says Hudson.Among its attractive fiber properties,chitosan is non-allergenic, has ben-eficial bioactivity, and is naturallyantimicrobial. "The surface of thefiber resists bacterial colonization,"says Hudson. "It is being promotedfor odor control because of its anti-microbial properties." However,chitosan's most useful property isthat it's haemostatic (efficient atstopping bleeding). One current ap-plication uses chitosan in ahaemostatic bandage to stop arterialbleeding. Not only hospitals, butmilitary organizations have keeninterest in this application.

MarketabilityAccording to Raffo, PLA's materialproperties enhance its marketability."Different aspects of the fiber make ituseful in different markets." Thefiber's natural fire retardance makes ituseful for drapery, office panel sys-tems, wallcovering, and upholstery. Its

ability to wick moisturelike cotton but dryquickly like polyestermake it appealing forapparel. Low odorretention and UV trans-parency (sunlightdoesn't degrade it)make it attractive forapparel, carpeting,home furnishings, anddrapery. "The fiber'ssustainability becomesa 'throw-in'," saysRaffo. "People like tobe environmentallyconscious as long as itdoesn't affect price.Performance is tbe mostimportant thing."

PERFORMANCE

Performance is theattractive feature forspider silk fibers. Re-searchers are impressedwith its material proper-ties. According to theUniversity ofWyoming's Randy Lewis, "Spidersilk's tensile strength is as high asKevlar, with elasticity as high as ny-lon. No manmade fiber has those com-bined properties."

"Spider silk is a hot field right nowbecause spiders have evolved a toolkitof as many as seven types of silks thatthey use to construct webs. Some ofthe types of silks in this 'toolkit' arerelatively stiff fibers with high tensilestrength, approaching that of our bestmanmade fibers. Others are highlyelastic and stretch almost as much asrubber. Many of these silks absorbkinetic energy better than almost anyknown natural or artificial fibers,which is what really distinguishesspider silk," says Blackledge.

Both medical and military applica-tions suggest themselves with thesematerial properties. "Spider silk hasbeen suggested for military use asbullet resistant armor because it canabsorb immense amounts of kineticenergy without breaking. For thatreason, it has also been considered inapplications such as high performance

JANUARY 9004

ropes (like the cables that stop planeswhen they land on aircraft carriers),"says Blackledge. "Some spider silksalso supercontract (that is, the fibersget shorter and tighter when wet). Thisis unique, and means that spider silkcould be used to make high perfor-mance sports clothing that fits better asathletes sweat more, or emergencybandages that contract as victims bleedmore, like an automatic tourniquet."

Potential '

According to Lewis, medical applica-tions could include artificial ligamentsand tendons. Michael Ellison atClemson University suggests that itmight serve well as scaffolding forcell growth for tissue cultures, or forvascular grafts. Other applications arealso possible—such as automobileairbags (spider silk absorbs energy),or apparel (spider silk takes up dyewell). "The cost of production wouldbe the only factor limiting the possi-bilities," says Lewis.

The possibilities become even morelimitless when you consider the goal of

w w w , AATCC.ORG

many spider silk researchers. "We arestudying spider silk and other naturallyoccurring materials in an attempt toidentify proteins that make up thepolymer," explains Ellison. "Syntheticpolymers have a much simpler struc-ture. Natural protein polymers aremuch more complex, giving us muchmore to play with." Spiders spin dif-ferent kinds of silk, each with differentmaterial properties. "All of these silksare different from one another in theirmaterial properties, but ultimatelyevolved from the same ancestral silk,"notes Blackledge. "This means that ifwe understand how DNA. which pro-vides the genetic blueprint for silkproteins, contributes to this diversearray of unique properties, then we canbioengineer spider silk fibers to have

facture the proteinsthey want in a.solution. Ellisonuses yeast as hisexpression me-dium. Lewis notes,"We can get bacte-ria and plants tomake the proteinsas welL Our groupis currently lookingat alfalfa, becausealfalfa normallyproduces a highprotein content."Nexia Biotech hasdeveloped abiopolymer rawmaterial with thesame biochemical

Photo courtesy ol Nexia Biotech. Used with permission.

the exact material properties neededfor a particular application by manipu-lating silk genes."

Currently, researchers are insertingthe bioengineered spider silk genesinto an "expression medium"—basi-cally, a delivery system that can manu-

AATCC REVIEW

composition as the polymer in spidersand is now developing a process toconvert this biopolymer into fiber.Nexia's expression system for theirsynthetic spider silk proteins is geneti-cally modified goats. The protein isisolated from the goats' milk.

BY DESIGN

Material Properties

The opportunities and implicationspresented by the bioengineering ofspider silk proteins are far-reaching.Bioengineered natural materials aredifferent from traditional natural fibersources, because bioengineering al-lows some control of the materialproperties of the fiber according to thedemands of the application.Bioengineering gives you control ofthe physical form of the fiber. NotesAlwattari. "You can fnake an artificialsilk fiber in a controlled predictablediameter—potentially up to a largersize scale monofilament diameter thanis presently available from the silkfarm." Because the biosynthetic pro-tein polymers are purpose designed,the manufacturer can also design howquickly the product should biodegrade.

Green Manufacturing

As well as studying the protein struc-ture of spider silk in an effort to lesigntheir own protein fibers, resear rs "are studying how the spider itsmanufactures its silk. "Spiderssilk at ambient temperatures w

10

JANUARY

the use of caustic chemical or acids,"says Blackledge. Researchers wouldlike to discover ways to mimic thatproduction method. According toEllison, "Synthetic polymers use a'brute force' method of creating fibers.Quite a bit of energy is put in, and alot of waste products result. We'restudying how the spider manages toturn the protein solution in its silk ductinto a fiber by the time it exits itsspinneret. The spider removes mois-ture from the protein in a controlledway, so that when the silk exits thespinneret, it is totally formed. The waythe spider produces fiber is a muchmore sustainable technique thanthe way we do it. We're studyingthese natural production methodsto make our own productionmethods much more sustainable.We'd like to eliminate problemssuch as effluents and excessiveenergy consumption."

an attachment mechanism that has aninteresting structure," says Ellison."The same thread's structural andmechanical properties are differentwhere the thread attaches to the organ-ism (the thread is flexible) and wherethe thread attaches to an anchor pointsuch as a rock (where the thread isstiff and inflexible)."

CompetitionDespite interesting material propertiesof the new "natural" synthetics, theywill certainly face competition fromtheir traditional synthetic brethren."Petrochemical-based synthetic fibers

People like to beenvironmentally

THE FUTURE

DiscoveryAccording to Lewis, "The role ofpolymer chemistry in discover-ing new fibers is slowing down.Current developments indicatethey are not discovering newtypes of fiber materials at nearlythe rate they had been.Biogeneticists can do things apolymer chemist never dreamed of"Ellison notes that researchers have onlybegun to study in detail the materialproperties of spider silk. Other materialproperties worth exploring include thesilk's sensitivity to humidity changesand to barometric pressure, as well asits ability to supercontract when ex-posed to liquid. "Spider silk also haspiezoelectric properties. We might beable to use those properties to design asensor or an actuator out of spider silkproteins."

Ellison points out that there areother natural fiber proteins that re-searchers are looking into as well.They are revisiting the traditionalsource of silk, the silk worm, with aneye towards investigating its genetics.They are also looking at mussels."They have a thread that they use as

JANUARY 2DO4

conscious as longas it doesn'taffect P R I C E

Performance. is the mostimportant

thing.will not go away," says Hudson, " ^ i l ^"Commodity synthetic fibers arecheap to produce and have great mate-rial properties. Solvent-based fiberssuch as rayon may see more legisla-tive pressure against their manufactureas time goes on because of their envi-ronmental impact. Thermoplasticssuch as polypropylene, polyester, andnylon will be around a long time.They are more efficient to manufac-ture and don't have as great an envi-ronmental impact." Yet Hudson agreesthat in the coming years the sourcesfor new fibers will come from twosources: biotechnology, and reusingwaste materials for fiber sources.

Price and PerformanceAlwattari says that renewability willbe a major issue for new fibers. How-

ever, performance is vital as well."New benefits have to be big. notincremental. As fibers become valueadded materials beyond textiles (e.g.,composites, drug-delivery systems,etc.), there is an opportunity to shiftaway from scale/cost driven innovationto performance driven innovation—solving previously unsolved problemsfor customers."

For the future of fibers, Alwattarisees "specially formulated and processedmaterials that are engineered to respondin dynamic and in-use situations such asthe delivery of active materials, detec-"tion, and controlled mechanical response

and resistance."He also notes that cost will be a

major issue. "It is a manifestationof simple market reality that ma-terials with improved perfor-mance to cost ratio, such ascheaper or lighter weight, willdisplace incumbents that are sub-par in performance to cost fortheir particular application."

Raffo sees the new fibers as avalue-added proposition. "Theprice of traditional synthetic fi-bers is linked to the price of pe-troleum. Traditional natural fiberslike cotton are commodities. Witha natural synthetic like PLA. theprice will go down as the demandincreases. Manufacturers will beable to see a good profit margin."

OpportunityThe opportunities represented to thefiber industry by the movement backto nature are great. The new naturalfibers promise new and intriguingmaterial properties that may take theminto applications beyond the arena of"just textiles" into performance materi-als. They promise an opportunity toadd value to products in the textilechain. And they definitely promise thebenefit of sustainabiiity and environ-mental awareness. "I see an opportu-nity for the textile industry to reinventitself with huge success," says Raffino."The consumer wants soft, luxuriousfibers that are environmentally aware.We can provide it. We. as an industry,have the means."

WWW.AATCC.ORG