Journal of Applied Research and Technology
www.jart.ccadet.unam.mx JournalofAppliedResearchandTechnology15(2017)205–210
Original
Comparison of regenerated bamboo and cotton performance in warm environment
Karina Solorio-Ferrales, Carlos Villa-Angulo
∗, Rafael Villa-Angulo, José Ramón Villa-Angulo
UniversidadAutónomadeBajaCalifornia,InstitutodeIngeniería,Av.DelaNormals/nCol.Insurgentes,C.P.21280MexicaliBajaCalifornia,Mexico Received17September2016;accepted2February2017
Availableonline3May2017
Abstract
Differentmaterialshavebeenusedtofabricatesummer(warmenvironment)clothing,suchascotton,nylon,neoprene,polyesterand100%
syntheticfibers.However,becauseoftheirmechanicalandthermalproperties,nylonandpolyesterclothhasatendencytorotandchafeindamp conditions.Inaddition,close-fittingsyntheticfibersandneoprenemakesomewearersfeeluncomfortablebecauseoftherapidlyoccurringbody skinsweat.However,bambooandcottonhavedemonstratedtohavelowthermalconductivity.Hence,theyareexcellentmaterialstofabricate summerclothing.Inthisstudy,atheoreticalanalysiscomplementedwithpracticalmeasurementsofthermalpropertiesofthreedifferentribknitted structuresproducedfroma30texyarnofthreeblendsoffibers(100%regeneratedbamboo,100%cottonand50:50regeneratedbamboo:cotton) wasrealizedtocomparebambooandcottonperformanceinwarmenvironment.Obtainedresultsshowthatgarmentthicknessandheatstorage rateinthehumanbodycansignificantlybereducedbyusing100%regeneratedbamboo,withoutcompromisingcomfort.
©2017UniversidadNacionalAutónomadeMéxico,CentrodeCienciasAplicadasyDesarrolloTecnológico.Thisisanopenaccessarticleunder theCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords:Warmenvironmentclothing;Protectivematerials;Bamboogarment;Modelingbehavior
1. Introduction
Tomaintainitstemperatureinasafetyinterval,thehuman body needs to eliminate excessive warmth. To eliminate the excessivewarmth, itchangesthe amountofbloodcirculating throughthebodyanditincreasestheamountofliquidtranspira- tiononthebodyskin.Theseactionsarecommonlyself-activated once its average internal temperature overpasses the 98.6◦F (37◦C)(Jessen,2012;Hockey&Rew,1996).Also,whenthe environmentaltemperature isclose tothe temperature of the bodyskin,the internal temperature regulation becomes more difficult.If theair temperature is equal toor higher thanthe temperatureofthebodyskin,thebloodthatcirculatescloseto the body skincannot help todecrease the humanbody tem- perature(Widmaier,Raff,&Strang,2013).Inaddition,ifthe environmentalhumidity increases,theevaporation of the liq- uidtranspirationonthebodyskindecreases.Hencetheeffort
∗Correspondingauthor.
E-mailaddress:[email protected](C.Villa-Angulo).
PeerReviewundertheresponsibilityofUniversidadNacionalAutónomade México.
ofthebodytomaintainasafetytemperatureisaffected,exces- sivebloodarrivestothebodyskinandlessarrivestotheactive muscles, the brain, andthe other internal organs (Marieb &
Hoehn,2012). Asaconsequence, the bodycapacity towork decreasesandaprematureexhaustionduetotheheatstressis experienced.
Thepreviouslydescribedconditionsarecommonlyfoundin seasidecitiesandalsoinmanyjobsinindustrializedcountries (Auliciems&Szokola,2007).Differentapproacheshavebeen usedtopreventandminimizetheeffectsofprematureexhaustion duetoheatstressinhotandwarmenvironment.Ontheonehand, supplementssuchasdrinksspeciallydesignedtoreplacebody fluidsandelectrolyteshavebeenused.Theymaybeofbenefit for workers whohavevery physically active occupations but theymayaddunnecessarysugarorsalttothediet(Jones,1992).
Ontheotherhand,protectiveclothinghasbeenusedtoreduce theeffectsof environmentalstressfactors.Thematerialsused inclothingwhichhasbeendesignedforwarmandhotweather mustbeabletogivecomfortanddurability.Itmustallowairto circulatefreelyacrosstheskin,whichcanhelptokeepthebody cool.In addition,thematerialneedstoresistthesun’sraysin ordertohelpdelaytheonsetofsunburn.
http://dx.doi.org/10.1016/j.jart.2017.02.002
1665-6423/©2017UniversidadNacionalAutónomadeMéxico,CentrodeCienciasAplicadasyDesarrolloTecnológico.Thisisanopenaccessarticleunderthe CCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Materials such as cotton, nylon 6, nylon 6.6, neoprene, polyester,and100%syntheticfibershavebeenusedforwarm andhotenvironmentclothingfabrication.However,purenylon andpolyesterclothhaveatendencytorotandchafe indamp conditions.Inaddition,evenaclose-fittingandlightweightgar- mentmadeof 100%syntheticfiberandneoprenemakesome wearerfeeluncomfortablebecauseoftherapidityofbodyskin sweat.Ontheotherhand,cottonandbambooareatribeofflow- ering perennialevergreen plants in the grass family Poaceae (Das&Chakrabarty,2008)whichisanexcellentcandidatefor warmenvironmentclothingfabricationduetoitsmechanicaland thermalproperties(Mounika,Ramaniah,Prasad,Rao,&Reddy, 2012;Prakash,Ramakrishnan,&Koushik,2013;Raimundo&
Figueiredo,2009).
In thisstudy, the thermal properties of three different rib knittedstructuresproducedfroma30texyarnofthreeblends of fibers(100%regenerated bamboo,100%cotton and50:50 regeneratedbamboo:cotton)wereusedtocomparetheperfor- manceofregeneratedbambooandcottoninwarmenvironment.
Standardized valuesfor metabolic rate, for different physical activities,wereusedinthecalculations.Theheatstorageratein thehumanbodyvsclothinginsulationfortheconsideredyarn blendswascalculated.Inaddition,therelationofclothingthick- nessandclothingisolationwasestablished.Theoreticalresults showthatthegarmentthicknessaswellastheheatstoragerate cansignificantlybereducedinthehumanbodybyusing100%
regeneratedbamboo,withoutcompromisingcomfort.
2. Heatbalanceandexchangemodelingofhumanbody andclothing
Theinteractionof heatwithadressedhumanbodycanbe described from an arbitrary flux of heat impinging with the dressedbody.Oncethefluxofheatisinsidethefrontsurfaceof thedressedbody,thebehaviorofthefluxofheatisdetermined bytheratesofstorage,productionandlosses.Byconservation ofenergy,thenetheatstoragemustbalancethenetproduction andlosseswithintheunitvolumeofthedressedbody.Usingthe nomenclatureofTable1,thiscanbewrittenas:(Bartkevicius, Rackiene,&Virbalis,2008;Holmer,2006)
S=(M−W)−(R+C+E+K)−(Cres+Eres) (1) whereSistheheatstoragerate,Misthemetabolicenergypro- ductionrate,Wistheexternalmechanicalwork,andR,CandE aretheradiation,convectiveandevaporativeheatlossfromthe skin,respectively.Kistheconductiontothesurfacesbydirect contactwithskinorclothing,Cres andEres aretheconvective andevaporativeheatlossesfromrespiration,respectively.The unitsoftherateofstorage,productionandlossesareenergyper second,whicharejoulespersecond(Js−1)orwatts(W).Itis usefultostandardizeover personsof differentsizes byusing unitsof watts per squaremeter (Wm−2) of thebody surface area.
Theenergybalancecomponents,MandW,describetheheat productioninthehumanbody.Theothercomponents(R,C,E, K,Cres,andEres)describetheheatconsumption.Thermalenergy
Table1
Nomenclatureusedinthetheoreticalmodeling.
Ar
ADu Fractionofskinsurfaceinvolved inheatexchangebyradiation
Ar
ADu ≈0.77 n.d.
C Convectiveheatlossfromskin Wm−2 CORR Correctionfactortoclothing
insulation
n.d.
Cres Convectiveheatlossfrom respiration
Wm−2
E Evaporativeheatlossfromskin Wm−2 EP Emissivityofthehumanbody Ep≈0.97 n.d.
Eres Evaporativeheatlossfrom respiration
Wm−2
Fcl Reductionfactorforsensibleheat exchangeduetotheclotheswarm
n.d.
fcl Clothingarefactor n.d.
hc Convectiveheattransfer coefficient
Wm−2C−1
hr Radioactiveheattransfer coefficient
Wm−2C−1
Icl Intrinsicinsulationoftheclothing clo imdyn Dynamicpermeabilityindexfor
theclothing
n.d.
imst Staticpermeabilityindexofthe clothing
imst≈0.38 n.d.
Lr Lewisrelation Lr=1665◦CkPa−1
M Metabolicrate Wm−2
Pa Vaporpressureofthe environment
kPa
σ Stefan–Boltzmannconstant σ=5.67×10−8Wm−2K−4 Psat Saturationvaporpressure kPa
Psk Saturatedvaporpressureatmean skintemperature
kPa
R Radiationheatlossfromskin Wm−2 Ra Staticinsulationofboundaryair
layer
Ra≈0.11m2◦CW−1 Retdyn Dynamictotalwatervapor
resistanceoftheclothingsystem
m2kPaW−1
RH Relativehumidity (%)
Rtdyn Dynamicthermalresistanceof theclothingsystem
m2◦CW−1
Rtst Staticinsulationoftheclothing m2◦CW−1 S Rateofbodyheatstorage Wm−2
Ta Airtemperature ◦C
TG Globetemperature ◦C
Tmrt Meanradianttemperature ◦C
TS Drytemperature ◦C
Tsk Skintemperature ◦C
Va Airvelocity ms−1
W Mechanicalpower Wm−2
WS Walkingspeed ms−1
balanceisobtainedwhentheheatstoragerateisequaltozero (S=0).Inaddition,whentheheatstoragerateispositive(S>0) thebodytemperatureincreasesandthereexistsaheatgain,hence thebodyneedstobecooled.Ontheotherhand,whentheheat storagerateisnegative(S<0)thebodytemperaturedecreases andthereexistsaheatloss,hencethebodyneedstobeheated.
2.1. Heatproductioncomponents
In heat production components, the metabolic rate M is defined as the rate at which the body utilizes food to pro- duce energy. The unit of metabolic rate is the Met, where
1 Met=58.15 W m−2.An acceptedapproximationforthe calculationofthiscomponentistheequationofHarris–Benedict (Horrocks&Anand,2000)givenbyEq.(2)formalesandEq.
(3)forfemales.
M=66+13.7·w+5·h−6.8·a (2) M=655+9.6·w+1.7·h−4.7·a (3) Here,wisthehumanweightgiveninkg,histhehumanheight given in meters, and a is the human age given in years. In addition,standardizedvaluesfor metabolicratesfor different physicalactivitiesaregivenbythenormISO8996(ISO-8996, 2004). The other heat production component, the external mechanicalworkW isdefinedas the realizedbody mechani- calworkthatdoes notaddinternalheat.Formostactivitiesit canbemadeequaltozero.
2.2. Heatconsumptioncomponents
Thereisadifferenceintemperaturebetweentheenvironment andthesurfaceofthebodywithclothisolationparticipatingin theheatinterchange.TheradiationheatlossfromtheskinRis givenbyEq.(4)
R=hr·Fcl·(Tsk−Tmrt) (4) wherethemeanradianttemperatureTmrtisgivenin◦Candits valuecanbecalculatedusingEq.(5).TheskintemperatureTsk
isalsogivenin◦CandcanbecalculatedusingEq.(6).
Tmrt =TG+1.9·
Va·[TG−Ts] (5)
Tsk=35.7−0.0285·M (6)
Theradioactiveheattransfercoefficienthrandthereduction factorforsensibleheatexchangeduetotheclothesFclaregiven byEqs.(7)and(8),respectively.
hr =σ·Ep· Ar
ADU ·
(Tsk+273)4−(Tmrt+273)4
(Tsk−Tmrt) (7)
Fcl= 1
(hc+hr)·Icl·0.155+1/fcl
(8) StandardizedvaluesfortheintrinsicinsulationofclothingIcl
aregivenbythenormISO7730(ISO-7730,2005).Theclothing areafactorfclwhichisdependentonIcl,andtheconvectiveheat transfercoefficientwhichdependsonairvelocityvaaregiven byEqs.(9)and(10),respectively.
fcl=1+0.31·Icl (9)
hc=8.7·(va)0.6 (10)
Theconvectiveheatlossfromtheskincanbefoundusing Eq.(11)anditistheheatlossduetoairflowingbytheskinand carryingawaybodyheat.
C=(Tsk−Ta)
Rtdyn (11)
Here, the ambient temperature Ta comes from real measure- mentsandisgivenin◦C.Thedynamic thermalresistanceof theclothingsystemRtdynthathasunitsm2◦C/Wisdependent onthecharacteristicsoftheclotheswornandonenvironmental parameters.RtdynisobtainedusingEq.(12).
Rtdyn=Rtst·CORR (12)
InEq.(12)thestaticisolationofclothingisgivenbyRtst= Icl·0.155+Ra/fcl.Thecorrectionfactortoclothinginsulation CORRcanbecalculatedusingEq.(13)wherethewalkingspeed canbefoundusingWS=0.0052·(M−58).
CORR=e(0.043−0.398·V+0.066·V2−0.378·WS+0.094·WS2)
(13) Evaporativeheatlossfromtheskintotheenvironmentispro- portionaltothedifferencebetweenthesaturatedvaporpressure atmeanskintemperaturePskandthevaporpressureoftheenvi- ronmentairPa.Thisevaporativeheatlosscanbefoundusing thenextequation
E= w·(Psk−Pa)
Retdyn (14)
InEq.(14)theskinwittednessisfoundusingw=0.001·M and the vapor pressureof the environment using Pa=Psat· Ta·RH,wherethesaturationvaporpressureatagiventemper- aturePsat iscalculatedusingequation(15)whichisknownas Antoine’sformula.Thesaturatedvaporpressureatmeanskin temperature Psk andthedynamic totalwatervaporresistance oftheclothingsystemRetdynarecalculatedusingEqs.(16)and (17),respectively.
psat =0.1333·e
18.6686−4030.183Ta+235
(15) Psk=0.1333·e
18.6686−4030.183Tsk+235
(16) Retdyn= Rtdyn
Lr·imdyn (17)
InEq.(17)thedynamicpermeabilityindexfortheclothingis givenbyimdyn=imst−6.5·CORR+2.6·CORR2.Thecon- ductionKisusuallyverysmall,relativetootherterms,andcan safetybeneglected.
Heatlossfromrespirationcombinestheprocessesofevap- oration of moisturefromthe lungs aswellas convectiondue todisplacementof warmairinthelungs bycoldairfromthe outsideenvironment.Botheffectsfromrespiration,convective heatlossCresandevaporativeheatlossEres,canbequantified usingEqs.(18)and(19)respectively.
Cres=0.0014·M(34−Ta) (18)
Eres=0.0173·M(5.87−Pa) (19)
3. Modelingresults
To compare regenerated bamboo and cotton capacity for warm environment clothing, we used the warm environment characteristicsshowninTable2.Thesecharacteristicsarefound inseasidecitiesandinmanyjobsof industrializedcountries.
Threedifferentribknittedstructures,asshowninFig.1,were
Table2
Environmentalcharacteristicsusedincalculations.
Airtemperature Ta=41◦C
Vaporpressureoftheenvironment Pa=143.5kPa
RelativeHumidity RH=45%
Airvelocity Va=3.63m/s
Meanradianttemperature Tmrt=33.47◦C
Stefan–Boltzmannconstant σ=5.67×10−8Wm−2K−4 Emissivityofthehumanbody Ep=0.97
Fractionofskinsurfaceinvolvedin heatexchangebyradiation
Ar/ADU=0.77
Staticinsulationofboundaryairlayer Ra=0.11 Staticpermeabilityindexofthe
clothing
Imst=0.38
Lewisrelation Lr=16.65◦C/kPa
Fig.1.Ribknittedstructure.
producedfroma30 texyarnof threeblendsof fibers (100%
regeneratedbamboo,100%cottonand50:50%regeneratedbam- boo:cotton).The30texyarnofthethreeblendsoffiberswere spuninaspinningmillusingtwistmultiplierof3.8and15,500 spindler.p.m.Theregeneratedbamboofiberswereproducedin awet-spunprocessinwhichnaturalcellulosewasusedasraw material inahydrolysis–alkalization process obtaining asoft mass,fromwhichthenaturalfibers aremechanicallycombed outandspunintoyarn.Thethreefabricsampleswereprepared ina1×1ribmachine.Theparametersoftheknittedmachine are:numberoffeeders24,diameter30in.andmachinegauge 18.ThehairinessofyarnswasmeasuredbyZweigleG566hairi- nesstester.Foreachyarnaconeof1000mlengthwastested.
Thenumberofhairslongerthan3mmlengthper1000mlength of yarn was considered for analysis. The thermal conductiv- ities, (W m−1K−1), defined as the propertyof a material to conduct heat flow,were measured using an Alambeta instru- ment.Fivereadingswere takenfor each ofthe knittedfabric andthen averageswere calculated. Table 3 shows the calcu- latedaveragevaluesforthethreefabricsamples.TheAlambeta
Table3
Thermalconductivitiesusedincalculations.
Material Thermalconductivity(Wm−1K−1)×10−3
100%cotton 55.27
100%regeneratedbamboo 45.04 50:50%reg.bamboo-cotton 49.66
Air temperature, Ta (°C) 10
Heat storage rate, S (w/m2) 100 200 300 400 500 600 700 800
0
20 30 40 50 60 70
M=9.2 M=9.0 M=6.61 M=4.46
Fig.2.Heatstorageratesinthehumanbodyvsairtemperatureforfourmetabolic rates.
instrument usestwo measuringheads betweenwhichthetest sampleisplaced.Bothmeasuringheadsareequippedwithheat flow sensors (thermocouples).The lower measuring heads is adjustedtotheambienttemperaturebysuitablecoolingmeans;
the upper, heated measuring head is adjustedto acontrolled constantdifferentialtemperature.Theheatflowsensorsactup atthecontactfacesofbothmeasuringheads.Whenuppermea- suringheadisloweredonthemeasuringsampletheheatflow at theuppersurface andthe undersideof the testsamplecan bemeasured.Thefabricthicknesscanalsobemeasuredbythe instrument.Thethermalresistance,R(m2K W−1),definedas thepropertyofamaterialtoresistaheatflow,wascalculated usingEq.(20)(Chidambaram,Govindan,&Venkatraman,2012;
Majumdar,Mukhopadhyay,&Yadav,2010) R(m2K W−1)= h(m)
(W m−1K−1) (20)
whereh(m)isthegarmentthicknessgiveninmeters.Inaddi- tion,fromthenormISO8996(ISO-8996,2004),weusedfour standardized values for metabolic rate. The four considered values for metabolic rate and their associated physicalactiv- ities are:M=9.2met forheavy construction,M=9met for gardening,M=6.61metformediumweightconstructionand M=4.46metforlightweightconstruction.
Fig. 2, for different ambient temperatures,shows the heat storagerate thatneedstobeeliminatedfromthehumanbody toreachthermalenergybalance.Thermalenergybalancethatis givenwhentheheatstoragerateinthehumanbodyisequalto zero,(S=0),willbereferredasthermalcomfortinthisstudy.
The curvesof Fig.2 were obtained byusing Eq. (1) andthe parameters given inTables 1–3. As expected,from Fig.2 it isobservedthatasthetemperature increases,theheatstorage
Clothing isolation, Icl (Clo) 0.05
Heat storage rate, S (w/m2) 100 200 300 400 500 600 700 800
0
Clothing thickness (mm) 0.1
3.20 4.0
2.0 3.0
1.0
0.50 0.95 1.40 1.85 2.30 2.75
M=9.2 M=9.0 M=6.61 M=4.46
Fig.3.Heatstorageratesinthehumanbodyvsclothinginsulationfortherib knittedstructurefabricatedusing100%regeneratedbambooandfourdifferent metabolicrates.
rateinthe humanbodyincreases,andmoreheatneedstobe eliminatedfromthebodytoreachthermalcomfort.Inaddition, asthemetabolicrateincreases,moreheatisstoredinthebody.
Inordertocomparetheeffectinheatstorageratebyclothing isolation, the thermal properties of the three fabricatedsam- pleswereevaluatedinthe heatbalanceandexchangemodels describedinSection2.Fig.3,forfourdifferentmetabolicrates, shows the heat storage rate in the human body vs clothing insulationforthe ribknittedstructurefabricated, using100%
regeneratedbamboo.ThecurvesofFig.3wereobtainedusing Eq.(1)andparametersshowninTables2and3.FromFig.3, itis observedthat for clothingisolation from0.05 to1.4clo, whichisgivenbyclothingthicknessfrom0.1to1.18mm,asthe insulationincreaseslessheatisstoredinthehumanbody.Onthe otherhand,forclothingisolationgreater than1.4clowhichis givenbyclothingthicknessgreaterthan1.18mm,astheinsula- tionincreasestheheatstoredinthehumanbodyincreases.This behaviorisunderstandablebecauseforclothingthicknessless than1.18mmthemechanicalandthermalpropertiesof100%
bambooallowsairtocirculatefreelyacrosstheskin,whichhelps tokeepthebodycool.Ontheotherhand,increasesinclothing thicknessuntilreaching3cloofisolationrepresentsathickand heavygarmentsuchas winterwear;hence,for characteristics showninTable2,theheatstoragerate increases.In addition, itisobservedthatas themetabolicrate decreaseslessheatis storedinthebody.Hence,lessheatneedstobeeliminatedfrom thebodytoreachthermalcomfort.
Fig. 4 shows the heat storage rate in the human body vs clothinginsulationfortheribknittedstructurefabricatedusing 100%cotton andthe consideredmetabolicrates. In addition, Fig.4showstherelationofclothingthicknessandclothingiso- lation.FromFig.4,itisobservedthatastheclothinginsulation increasesfrom 0.05 to2.75clo, nosignificant change on the amountofstoredheatinthehumanbodyisobtained.However, forclothingisolationgreaterthan2.75clotheheatstoragerate inthehumanbodystartsdrasticallyincreasing.Similarto100%
bamboo,cottonclothingthicknesswithisolationcloseto3clo
Clothing isolation, Icl (Clo) 0.05
Heat storage rate, S (w/m2) 100 200 300 400 500 600 700 800
0
Clothing thickness (mm) 0.5
3.20 20
10 15
5.0
0.50 0.95 1.40 1.85 2.30 2.75
900
M=9.2 M=9.0 M=6.61 M=4.46
Fig.4.Heatstoragerateinthehumanbodyvsclothinginsulationfortherib knittedstructurefabricatedusing100%cottonandfourdifferentmetabolicrates.
Clothing isolation, Ic (Clo) 0.05
Heat storage rate, S (w/m2) 100 200 300 400 500 600 700 800
0
Clothing thickness (mm) 0.5
3.20 15
8.0 12
4.0
0.50 0.95 1.40 1.85 2.30 2.75
900
M=9.2 M=9.0 M=6.61 M=4.46
Fig.5.Heatstoragerateinthehumanbodyvsclothinginsulationfortherib knittedstructurefabricatedusing50:50%regeneratedbamboo-cottonandfour differentmetabolicrates.
representsathickandheavy garmentsuchas winterwear.In addition,itisalsoobservedthatasthemetabolicratedecreases duetodecreaseinphysicalactivity,lessstoredheatneedstobe eliminatedfromthebody.
Fig. 5 shows the heat storage rate in the human body vs clothinginsulationfortheribknittedstructurefabricatedusing 50:50%regeneratedbamboo-cotton.Fig.5alsoshowstherela- tionofclothingthicknessandclothingisolation.Similarto100%
cotton(Fig.4),inFig.5itisobservedthatastheclothinginsu- lation increases from 0.05 to 2.75clo, no significant change onthe amountof storedheatinthe humanbodyis obtained.
However,for clothingisolationgreater than2.75clo, theheat storagerateinthehumanbodystartsdrasticallyincreasing.The observeddifferencebetween100%cotton(Fig.4)and50:50%
regeneratedbamboo-cotton(Fig.5)isthat50:50%regenerated bamboo-cottoncanreachthesameclothingisolationas100%
cottonwithahalfofclothingthickness.In addition,itisalso
Clothing thickness (mm) 3 6 9
0
Intrinsic insulation of the clothing, Icl (Clo)
0.5 1 1.5 2 2.5 3
100% cotton
100% reg. bamboo 50:50%
reg. bamboo-cotton
Fig.6.Clothing thickness vsintrinsic insulation oftheclothing for 100%
regeneratedbamboo,100%cottonand50:50%regeneratedbamboo-cottonyarn blends.
observedthatasthemetabolicratedecreases,lessstoredheat needstobeeliminatedfromthebody.
Fig. 6 shows clothing thickness vs intrinsic insulation of theclothing for100%regenerated bamboo,100%cotton and 50:50%regeneratedbamboo-cottonyarnblends.Asexpected, fromFig.6itisobservedthatintrinsicinsulationofthecloth- ing increaseswhen clothingthickness isincreased. Itis seen that100%regeneratedbamboocanreachisolationvaluesusing smallerclothingthicknessthan100%cottonand50:50%regen- eratedbamboo: cotton.Forexample, 3cloofisolation canbe givenbya100%regeneratedbamboogarmentwithathickness of3mm,whileagarmentof100%cottonand50:50% regen- eratedbamboo cotton need5.9mm and9.6mm of thickness, respectively.Hence,toreachintrinsicinsulationoftheclothing of3clo,thegarmentthicknessneededbyusing100%regener- atedbambooismorethanthreetimessmallerascomparedto 100%Cotton,andmorethantwotimessmallerascomparedto 50:50%regeneratedbamboo:cotton.
4. Discussionsandconclusions
In this study, thermal properties of a 30 tex yarn from a blendsof100%fiberofregeneratedbamboo,100%fiberofcot- tonand50:50%fiberofregeneratedbamboo:cottonwereused tocomparebambooandcottonperformanceinwarmenviron- ment.Fourphysicalactivities,characterizedbytheirmetabolic rate,wereusedinthecalculations.Theoreticalresultsshowthat 100%regenerated bamboohasabetterisolation performance inhotenvironment.The heatstoragerate inthe humanbody cansignificantlybereducedbyusing100%regeneratedbam- boo.Inaddition,thegarmentthicknesscanalsobesignificantly reducedbyusing100%regeneratedbamboo.Thismeansthat 3cloofthermalisolationcanbegivenbyagarmentof 100%
regeneratedbamboowithathicknessof3mm,while5.9mmand 9.6mmofthicknessareneededby50:50%regeneratedbamboo:
cotton and100%cotton,respectively. Insummary,theoretical analysis,complementedwithpracticalmeasurementofthermal propertiesofthreedifferentribknittedstructuresproducedfrom a30texyarnofthreeblendsoffibers,showthat100%regener- atedbamboocanbeusedtoreducegarmentthicknessandheat storageinwarmenvironmentclothing,withoutcompromising comfort.Hence,acomprehensiveunderstandingoftheoretical models,willbeofgreatimportancetoexperimentalists,whoare potentiallyinterestedinobtainingthenumericalestimatesand correlatethetheoreticalresultswithpracticalmeasurements.
Conflictofinterest
Theauthorshavenoconflictsofinteresttodeclare.
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