Thesis2018

Watersorptioninpolyethylenefilmsproducedwithdifferentprotocoles

PabloCamposRamsMat:1900068299

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Index1-Abstract2-Introduction3-Material-Nano-fibberscellulose-Low-densitypolyethylene(LDPE)-Mounting-Expansionofthegas-Buoyancyforce-Hooke'slaw-Wateractivity-Antoine'sLaw-Diffusivity4-Procedure-Developmentofdata5-Discussionofresults-Nanocellulosefibberswith30%Arginine-LDPE35,5mg-LDPE80mg-Changeinprocedure-LDPE80mg6-Conclusions7.Bibliography

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1.AbstractThisthesiswillmakeacharacterizationoffourLDPEmembranes.Eachonerepresentativeofadifferentpointofthefinalmembraneproductionprocess.Theobjective,tofindoutatwhichpointoftheprocessthecapacityofwaterabsorptioninthemembraneincreasesconsiderably.Thethesispartofthevaluesobtainedin"McCall1983SolubilityanddiffusivityofwaterinLDPE"[12]wherethewaterabsorptionvaluesare50ppmand"2017InfluenceofwateruptakeontheelectricalDC-conductivityofinsulatingLDPE/MgOnanocomposites"[4]wherethevaluesofwaterabsorptioninaLDPEmembranearemuchhigher.Itwillproceedtoperformmembranesaturationswithwateringasphasetodifferentcontrolledwateractivitiesandtoperformdesorptionwithvacuumpumptocalculatethevolumeofwaterabsorbedandthuscharacterizethemembranes.2.IntroductionWiththedevelopmentofnewtechnologiesisneededtocarrycurrentoverlongerdistances.Toavoid lossesthevoltage increases,but thermalandelectrical lossesalso increase.To compensate these losseshave to resort to a better insulator toinvolvethecable.Yearsagothestrategytoimproveaninsulatingwaspurifyingthepolymer [3] to avoid the electron conduction. Nowadays, it is dispersed smallfractions (1-3 wt.%) of inorganic nanoparticles in the LDPE in order to reduceconductivity to 1 -2 order of magnitude. The physical explanation is still underdiscussion.[4]The thesis starts from an article published in 1983 "McCall 1983 Solubility anddiffusivity of water in LDPE"[12] where the absorption of liquid water in Low-DensityPolyethylene(LDPE)vasstudied.Afterwards,asimilarstudywasperformed"2017Influenceofwateruptakeontheelectrical DC-conductivity of insulating LDPE /MgO nanocomposites "[4]whereabsorptiongaswateronaLDPE treatednanoparticlesMgOwasmade.MgOwasmodified superficially with octyl (triethoxy) silane (C8) reacting the MgO withSilane for 24 h [5]. After nanoparticles MgO powder were mixed with LDPE,antioxidant(Irganox1076)dissolvedinn-heptane.Thesuspensionwasstirredfor60minanddriedat80°C.Driedmixturewasblendedat150°Cand100rpmfor6minutes in a compressor. It was degassed at 100 ° C, and it was compressionmoldedfilms.Thesecondstudywasintendedtoobtainasimilarabsorptionamounttothefirstdue to the membranes were mostly the same material. However, considerablyhigherabsorptionvaluesitwasobtained.Therefore,inthepresentthesisitwillbeproceedtotrytofindwhythereissuchadifference between LDPE and LDPE / MgO treated. In order to do that, four

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membrane samples are analysed. Every samplewill be a step in the productionprocess of the final membrane, pure LDPE, pure LDPE treated hydraulic press,pureLDPEpresspreparedwith3mLofheptaneandpureLDPEtreatedinpress0.02W+YandAminoAcidIt is intended to find which processes, from all of those done to LDPE, it doesincreaseabsorptionofwater.Previouslytotheexperimentthemainhypothesisitis thatwhenLDPE is treatedwithhexane there are somenanobubbles that staytrappedintheformofinthestructureofLDPE,andthisnanobubblesaretheonesabsorbingtheamountofwaterthatmakestheexperimentdifferent.3.materialNanocelluloseThenanocelluloseisamaterialmadebyfiber,thesefibersarecomposedofsmallerfibersthatareaswellcomposedofsmallerfibersuptoafiberthatisonlymadebyonecelluloseschain.Thusthereisasignificantrelationbetweenlength-diameterbecause itsdiameter isbetween10to20nanometersandits length is tentimesbigger.[1][2]The image (figure 1) bellow shows the celluloses in the nanocellulose chainformingapolymer. Itcanbeseen that itsstructure ismostlynonpolarmolecule,andthereforehydrophobic.Thegoalistocreateapolymerthatcanabsorbwater,modifying nanocellulose with the amino acid arginine. Alcohol radicals replacearginine in a variable percentage. Studying how it affects this percentagedifference.To this, cellulose pulp will be created and it will be mixed with differentpercentagesofArginine,thenitwillbeheateduntiltheArgininewillreactwiththecellulosechainreplacing theOH in thepolymer, theOHwill formwaterandwillevaporate.Thisprocessisnotcarriedoutanddescribedinthisthesis,althoughthiscellulosepulpmadepreviouslyinaSwedishlaboratorythatappearsintheliterature[12]itwill be used. However, the present paper is going to study the water uptakeanalysingthedifferentpressuresandconcentrations.

Figure1.Cadenadenanocellulose

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Thenewpolymerwillbepolarbecause someof theOHwill replacebyArginineandthepolymercharacteristicswilldependontheconcentrationofArginine.Thenanofibrillatedcellulose(NFC)membranewith30%concentrationofArgininewillbethefirsttobeanalysed.Low-DensityPolyethylene(LDPE)The Low Density Polyethylene (LDPE) is thematerial to be usedmainly in thisstudy, it is a thermoplastic formed of ethylenemonomers. The polymer is not asinglechainbutithasbigradicalsthatformanet,thisisthedifferencewithHighDensityPolyethylene(HDPE)[6]

Figure2.StructureofLDPEComparingLDPEwithHDPEformedbyasinglechainofethylenes,LDPE’sdegreeof compaction will decrease due to the large radicals. Every polymerizationprocessconsistsofthreeparts:initiation,propagationandtermination.ThecaseofLDPE process, it should be worked at high pressures. The most importantcharacteristicsofpolyethylenearelowreactivityandeasilyrecyclability.[7]Low price, high processability and easy recycled processmakes these polymersvery present inmany industries, i.e., in bags, bottles, laboratory equipment... Somuchsothatin2013LDPEindustrygenerated33billionUS$.[8]MountingAssembling consists of a cylindrical column with a concentric jacket formaintaining the temperature. Sample is placed in the column together with analuminium strip hung from a spring and the system is brought to the operatingconditions. The column is the principal object where the conditions andmeasurementswillbemanipulated.

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Figure3.DiagramofthecompleteassemblyThecylindricalcolumnhasawaterinletandoutletforthejacket,astreamofwaterheated to 35.5 ° C (process temperature), the jacketmaintains the temperatureduringtheprocess.Inordertoavoidtemperaturechangesandthereforelossesinpressure (activity) and taking into account that the process is carried out withgases and it takes a lot of time, the entire assembly is going to be wrapped ininsulatingmaterial.Otherwisetheexperimentwillbebiased.Thesystemhasanotherinletofwater,wateristakenfromatankheatedto35°C,thiswillevaporateandenterdirectlytothecolumn,itwillnotbeoutletbecauseitshallbestoredinthecolumnuntiltheendtheexperiment.Pressurewillbereducedto0Atmosphereswithavacuumpump.Duetothe lowpressure when the valve of the tank (S01) will be opened water willsimultaneouslyaspirateandchange togasphase to fill the tank(S02).Whenthedesired humidity is reached in the expansion tank (S02) the inlet valve to thecolumnwillbeopenedlettingthewatergasenterinthecylindricalcolumnwherethesampleislocated.

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Figure3.VacuumpumpTelecamera measures the variation in height of the sample by analysing thedifferenceinbrightness,becausethesamplesusedaretransparentthedifferencein brightness is captured on the aluminium strip previously placed with thesample. The sample displacement due to increased weight absorbed water willcauseanelongation in the spring thatholds it.To correctlymeasures theheightvariationitisplacedawhitepanelbehindthesample.Telecameraworksbymeasuringthevariationofbrightnessalonganaxethereforedetect brightness variations at the edges of aluminium foil. Telecameramakes ameasurement every x seconds. Telecamera uses five variables to assess thevariation inheight: time, height1 andheight2 (both are thepoint of variation inbrightnessoftwopredefinedaxes),reference1andreference2(whicharethesizeofthealuminiumstrip).

The image shows the sample (white film)aluminium foil (dark film) and four variables;height1, height 2 (blue and red line) Ref1, Ref2.(redsegments)Thetelecamerameasuresoverblueandredlines.References 1 and 2 are necessary, because thetelecamera takes measurements in pixels.Acordingly themeasure of the aluminium strip inmm and the measure of the strip in pixels(reference1&2) it is a reference to convert allvaluesofheightvariation tomillimetres.With thelogicalratiopixels/mm.Figure 4 shows and aluminium strip viewed by thetelecamera.

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Asit isbeensaid,thetelecameraworksbyvariationofbrightnessintheredandblue axis (figure4), i.e. the camera evaluates brightness changes only in the axisandthemadeagraphic,thewaterbubblesareseenintheimagebelongtotheshirtandcontributetotheerrorofthecamera.

Figure5.BrightnessdifferencesampleviewtheprogramTelecameradetectstherelevantdataattheedgesofthealuminiumstrip.Itshouldbenotedthecrucialimportanceoftheheatingsystemtotrytokeepthetemperatureasstableaspossible.Becausewhenworkingwithgasesavariationofhalfdegreecausesachangeinwaterhumidityanditwillaffectthedataobtainedby the telecamera, especially when the system is left working overnight. That'swhytherearedifferentsystemstomaintainconstanttemperature.Therefore, all the systemandpipeswill be coveredwith insulatingmaterial andtheheatingwatersystemwillbeconnectedtothecolumnjacketandtheexpansiontank. Likewise, a resistance will heat the top of the column because a smallcondensation would put the results on risk and even break the sample. Theresistance also heat tripod telecamera because it has been detected undesiredheightvariationsduetotemperaturechangesintripod.GasexpansionWhenwater vapor is loaded in the expansion tank, the value pressuremust bechargedtoahighervaluethantheworkingpressurevaluebecauselogicallywhenopening the inlet valve to the column itwill increase the volume and lower thepressure.Calculations relevant to this part are as follows, assuming that it behaves as anidealgas.

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Situation1

𝑃!! = 0 𝑃!! =𝑛!𝑅𝑇𝑉1 P!"#$%& =

n!RTV1+ V2

Situation2

𝑃!! =𝑛!𝑅𝑇𝑉2 𝑃!! =

𝑛!𝑅𝑇𝑉1 P!"#$%& =

n!RTV1+ V2+

n!RTV1+ V2

𝑃 =𝑛!𝑅𝑇 + 𝑛!𝑅𝑇𝑉1+ 𝑉2

Andsoonwecanobtainthedesiredpressurewiththiscalculation.FlotationcoefficientIt is calledArchimedes’ principle, it states that the buoyant force of an object isequaltothefluiddisplacedbytheobject.Knowingthatthesampleisdissolvedinairasworkingfluidthereisacomponentoftheweightofthesamplethatcannotbe attributed to its actual weight (pressure 0), so as it will work to differentpressuresmust calculate the buoyancy force on function of pressure tomake acorrectanalysisofthedifferentactivities.Because of that a simple experiment will be performed, the sample will be 0atmospheresandwill return toatmosphericpressure so thedifference inheightwillbefloatingforcebecauseitwillnotabsorbedanythingatall.

𝐹!"#$%&'$ = 𝑉!"#$%&'&!( 𝜌!"#$%& 𝑔(𝑔 𝑚𝑠! )

Thebuoyancy force isequal to theproductof thevolumeof fluiddisplaced fluiddensityandgravity.

𝑃𝑉 = 𝑛𝑅𝑇 =𝑚𝑀!"#

𝑅𝑇 𝑚𝑉 = 𝜌!"#$%& =

𝑃𝑀!"#

𝑅𝑇

It is needed to find the ratio of the density with pressure by the ideal gas law.Replacing:

𝐹!"#$%&'$𝑔 (𝑃) = 𝑉

𝑃𝑀!"#

𝑅𝑇 (𝑔)

Expressingequationingrams,knowingthateverythingweightvariationduetothevariation of buoyant force and adapting it to our experimentwhere the fluid iswatergas.

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𝐹!"#$%&'$𝑔 (𝑃) = 𝑉

𝑃𝑀!"#$%

𝑅𝑇 (𝑔)

Experimentallymustsatisfytheequation:

ℎ! − ℎ! 𝑘 +𝐹!"#$%&'$

𝑔 = ℎ! − ℎ! 𝑘 +𝑉𝑃𝑀𝑅𝑇 = 0

All the weight difference is due to the buoyant force. Where k is the springconstant. The only unknown value that we cannot find experimentally is thevolume:

𝑉 =ℎ! − ℎ! 𝑘𝑃𝑀!/𝑅𝑇

Inthiswayweobtainthevalueofthebuoyantforceforallexperiments.Hooke'slawInordertoobtainanincreaseinmassduetothevariationintheelongationofthespring,Hooke'slawwillbeused.

𝑀 = 𝑘 𝑥 − 𝑥! + 𝐹WhereMisthemassincrease,(x-x0)isthevariationinheightofthesample,Fisaflotation coefficient determined in another experiment, k is the constant to beobtainedand itsunitsareg/mm.Inthisexperiment itwillbetaken intoaccountthe bouyancy but obviously it will be a very small value compared with thevariationsoftheabsorbedwater.WateractivityWateractivityistheratioofthewaterpressureandthesaturationpressureatthesametemperature:

𝜇 𝑝! ,𝑇 =𝑝!(𝑇)𝑋𝑝!"#(𝑇)

BeingpwthepartialpressureofgasandXthemolefractionofwater,X=1inallcases to be treated. Relative humidity is the percentage of water in the systemregardingthemaximumcapacity.

𝐻! 𝑝! =𝑝!𝑝!"#

∗ 100

Duringthisstudy,humidityoractivitywillbeusedforreferringtothesamething.

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AntoinelawAlthough the experiment will be performed at the same temperature, smallchangeswillchangethesaturationpressureofwaterandthustheactivity,sothatwillbeconsideredalltime.Antoine'slawrelatesthesaturationpressureofthewatertemperature,thevaluesA,BandCcalculatedempiricallybibliographicdataaremade.

log!" 𝑝 = 𝐴 −𝐵

𝐶 + 𝑇DiffusivityDiffusivity is the process by which particles of a substance introduced into amedium.Thereisatransferbetweentwoadjacentsystemsalwaysfromthehigherconcentration to lower concentration. Thediffusivitymeasures the speedof thistransfer.TocalculatethediffusivityFick's lawitwillbeused,this lawstatesthatsolute will move to the less concentrated medium proportionally to theconcentrationgradient,asinglespatialdimensionvalues.[9]

𝐽 = −𝐷𝑑𝐶𝑑𝑥

Being "J" the diffusion rate as amount of substance per unit of area, "C"concentration,“x”thicknesspenetratedand“D”thediffusivity.[10]Applied to the case study, a rectangular plate of known thickness, it will beresearchedliteraturedataforthesamesituationsothattheequationdevelopedisthefollowing.[11]

𝑀𝑀!

= 1−8𝜋!

12𝑛 + 1 ! exp −

𝐷 2𝑛 + 1 !𝜋!𝑡𝐿!

!

!!!

Being“L”characteristicofthesample“M”and“Minf”dataobtainedinexperiments.Itisgoingtobepossibletoiteratetogetthediffusivityofeachoftheexperiments.4.ProcessProcessFirst of all, the laboratory membrane will be held with gloves to avoidcontaminating it, a rectangular piece will be held from the edges withoutdeforming. It will be weighed and will be determined their thickness. For bothtests,aseriesofmeasurementswillbemadeandtheaveragevalueofthemwillbeconsidered.Then,thesamplewillbeplacedwithintheassemblyhangingfromthespringwiththealuminiumstrip.

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Afterplacingthesamplewithintheassemblywillbegeneratedvacuum,thegoaltodo this it is dry completely the sample. Generating 0 atmospheres inside thecolumnsealedandthenmodifythepressure.Generating0atmospheresinitially,itcanbeassumedthatallthegaswithinthecolumnissteam.Duringtheprocessofgeneratingvacuuminthecolumnandthusintheexpansiontank,thesampleisobservedbytelecamera,thesamplewillgoupasitloseswaterbecausewhenitlosesmassandweightthespringthatholdsitwillbecompressed.Actually, at first due to the buoyancy of everymaterial in a fluid, itwill show adescentbutoverallthesamplewillrise.Atthemomentitwillbenowaterinside,according to Hooke’s law, the mass of the sample will be dried and it will bepossibletoevaluatethefirstpointofthefirstpressureequilibrium.Then,thesystemwillhave0atmospheres,pumpwillstopandallvalveswillclose.After, expansion tank water will be filled with the desired water activity(pressure).valvesS01andS012willbeopenedveryslowlytopreventunwantedcondensation or cooling. Water is absorbed to the tank and it is evaporatedimmediatelybecausethesystemisat0atm.WithamanometerconnectedtotheexpansiontankS02itwillevaluatedthepressureanditwillbeabletoreachthepressureandwateractivitydesired.

Figure6.DiagramValveWhenthedesiredactivityisreached,thevalveS01willbeclosed,andtheaccessvalvetothecolumnwillbeopened.Thegaswillexpandthroughthetwovolumesanditwillbeobtainedthepressureandworkactivity.Moreover,thesamplewillbeexposedtoaspecificwateractivityandtheprocessofwaterabsorptionof thesamplewillbegin.Dependingondiffusivityandwateractivityitwillabsorbfasterorslower.Withtelecamerawillbeevaluatedagainthedifferenceintheheightofthesample.Thesamplewilldescentuntilthemaximumamountabsorptionofwater(equilibriumstate).Analysing the dry mass of the sample and the mass of water that it is able toabsorb in every step of the experiment, it will be known the amount of waterabsorbedbythesampleunderspecificconditions.Whenonestepfinish,accessvalvetothecolumnwillthenbeclosed,itwillbere-opened thevalvesS01andS02 to loadanotherwaterpressure in theexpansion

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tank once loaded the desired pressure itwill be closed S01 and the inlet to thecolumn valve will be opened subjecting the sample to a different and higheractivity.Whenitwillreachequilibriumstateitwillgetanotherpressure-absorbedmasspoint.Itwillbeloadedtheexpansiontankswithdifferentactivitiesthenumberoftimesnecessarytoevaluatethediffusivity.When the experiment ends the system should be brought to an atmosphericpressurebeforehandlinganythingandbeforechangingthesample.DataprocessingThe assembly provides a series of data, from these data the behavior of themembranewillbeinterpreted.AfterobtainingdataitonlywillbeusedExceltoolformanipulationandinterpretationofit.Telecamera synchronized with the computer provides the values it has beenalready seen,height1,height2, reference2, reference2and time.Toevaluate thedata, it canbeused justoneheightandone referencebutalways correspondingwitheachother.First,thedatawillbemanipulatedtogeneratecolumnsofdataandtheheightwillberepresentedasafunctionoftime.Knowingthattheexperimentendswhenthesamplestopsfallingandthereforeithasabsorbedthemaximumamountofwater.Asheightversustimewillbeinaccurate,itwillbeplottedheightagainsttherootoftime.

Graph1.GraphicscomparisonHeight-t,height-t0.5Asitcanbeseeninthegraph1theslopeislesswiththerootoftime,whichhelpsustodistinguishwhetherthesystemreachedequilibrium.Each experiment of the study will be made with a different membrane, eachexperimentwillbedividedintodifferentsteps.Fromeachstepyoucanobtainallthe values provided by the telecamera and the initial and final pressures of thestep.Therefore, themanipulatedvariablewillbe the initial activityof thewater,the firststepwillalwaysbetoemptythecolumn,then25%,45%,55%...oranyothervalue,theobjectiveistoobtainseveralvaluesofactivity.

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Then the amount ofwater absorbed as a function of samplemass (blue line) isexpressed.Will iterate following the lawsof diffusivity tomodel thebehavior ofthemembrane(redline).

Graphic2.Exampleg_agua/g_polímerofunctionoft0,5Whenalldiffusivitiesandconcentrationsarecalculatedthefinaltwotableswillbemade,whichwillservetocomparewithotherexperimentsareperformed.Thedisturbancethatisseenintheinitialtimesisduetotheopeningoftheaccessvalve to the column. The strong pressure change causes the spring to oscillateviolentlyuntilitstabilizes.Markthestartingpointoftheexperiment

Graph 3. Example of concentration of water based activity and diffusivity depending on waterconcentration.5.DiscussionofResultsThissectioncontainsall theresultsobtained inthedifferentexperimentswillbeevaluated;graphsandobservedanomaliesarediscussed.Nano-cellulosefiberswith30%arginineThisistheexperimentfromwhichthegreatestwaterabsorptionisexpected.Ithaspolarizednano-membranecellulosefibersbytreatingwitharginine.Thefirststep

0

0,2

0,4

0,6

0,8

1

1,2

0 10 20 30 40 50 60 70

M(g

/g_p

ol)

t^0.5 (s^0.5)

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startsfrom0atm,thereforefrom0%ofinitialactivity,butleavethereststartsofthepreviousstepandthereforethereisanamountofwateralreadyabsorbed.Atalltimesthemassabsorbedrespondtotheequation.

𝑔!"# = ℎ − ℎ! ∗ 𝑆. 𝑓 ∗ 𝑘Where k is the spring constant expressed in (g / mm) and the Sf Scale factordifferentineachexperimentandexpressedin(mm/pixel).Wateractivity25%

Graph4.Waterabsorption25%activityAt25%activity,theminimumactivitytobeworkedon,thespeedofabsorptionistheslowest.Furthermorethisisthemembranemorewatercanbeabsorbed,soitistheslowestexperiment.Thecolumnwasvacuumvalveopenedand,afterafewsecondsaninitialpressureof13.98mbarscored.Itwasleftfor29hoursreachingafinalpressureof14.08mbar.Theheightdifferenceis196-190=6.YoucanseeinFigure4asthesystemdoesnotreachequilibriumcompletely.Inthegraphofmassabsorbedtheycanclearlyseetheoscillationsofthespring.Andanabnormal area differs diffusivity model (red line), just at night when thetemperaturedropssysteminevitably.Thediffusivityis3*10-11cm/s2.Wateractivity55%

Graph5.Waterabsorption55%activityThespeedofthesecondexperimentismuchfaster,sincethediffusivityincreasesexponentiallywith thepressure.Thepreviouspressureof thecolumnwas24.72mbar.Theexpansiontankwasfilledtogenerateanactivityof55%inthesystem.

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Theinitialpressureofthesystemwas30.57mbar.Itwasleft24minutesreachingapressureof30.46mbar.Fromthegraphwecanseethatreachesequilibriumbydrawingaperfectlinefroms0,5=20.Continue tobe felt theoscillationsofspring, thediffusivity is1.4*10-8cm/s2.Theheightdifferenceis215.6to207.4=8.2.Wateractivity65%

Graph6.Waterabsorption65%activityIt increases the activity under absorption becomes much faster. The initialpressure in the columnwas30.46.After filling the expansion tank andopen thevalveofaccesstothecolumninitialpressurewas36.3mbar,after25minutesthepressurewas36.3mbar.Diffusivity coefficient is 8.5 *10-9cm/s2. The height difference 227.47-216.03 =11.44.Wateractivity85%

Graph7.Waterabsorption85%activityThepreviouspressure in the columnwas42.04.After filling the expansion tankandopenthevalveofaccesstothecolumninitialpressurewas55.5mbar,after49minutesthepressurewas56.1mbar.Diffusivity coefficient is 8.5 * 10-9 cm/s2. The height difference from 280.24 to244.10=36.13.

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Activityanddiffusivity

Graph8.Concentration-activityandconcentration-diffusivityFinally, the summary tablewill serve to compare this experimentwithothers. Itshould be noted the high concentration of water absorbed against subsequentexperiments.LDPEAshasalreadybeensaid,thisthesiswilltrytoanalyzewhentheLDPEproductionprocess increases the absorbent capacity of thematerial. Four samples analyzedmembrane.NeatLDPE,LDPENeatpressingLDPE+3mLofheptaneandLDPE+Antioxidant.There was an experimental problem in the first experiments, the data weredifficult to interpret. To solve it, a lenswas used for the telecamerawithmuchmoremagnification,themembranewasapproachedtothemembraneandthesize(mass)ofthemembranedoubled.Itwentfrom35.5gramssamplesof80grams.35.5mgNeatLDPENeat LDPE is the most basic membrane. It is expected according to the article"SolubilityandDiffusionofWaterinLow-DensityPolyethyleneDavidW.McCall"avariationof50ppmisavariationof0.134pixelto5*10-5gH20/gLDPE.Vacuum

Graph9.Vacuumofthesample

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Avacuumpumpisusedtobringthesampleto0atmospheres,atwhichpointwecansaythatthereisnowaterinthesystem.Theinitialpressurewasatmosphericpressure, the final 0 atmospheres. There is a loss of height due to the buoyancyforce and the loss of the little water that can be in the sample. The heightdifferencewas317to314.6=2.33pixels.Wateractivity25%

From this point the waterabsorption is very small.The interpretation of thegraphs becomesincreasingly difficult.Image Neat LDPEabsorption25%RHhardlyany variation of 320.39 to320.20=0.19pixel.Whichimplies a very smallamountofwater.

Graph9.Waterabsorption25%activityTheinitialpressurewas25.5mbarsystem,after40minutesthefinalpressurewas25.3mbar.Wateractivity50%

Graph10.Waterabsorption50%activityTheheightvariationcontinuestobealmostimperceptible.Fromtheaverageofthepointsbefore theopeningof thevalveandwhen it reachesequilibrium(theendpoints),thevariationoftheheightisobtained317.6-316.35=1.25pixel.Theinitialpressurewas28.17mbarafter25minutesitwas27.96mbar.Whilethediffusivity3,2*10-8cm/s2.

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Wateractivity75%

Graph11.Waterabsorption75%activityThe initial pressure was 50.66 mbar after 41 minutes the pressure was 51.43mbar. The variation in height of 318.64 to 318.26 = 0.3823 was pixel. Anddiffusivity3.5*10-7cm/s2.As seen in Figure 11 the variation in height is minimal the problem is that theoscillationofthespringislargerthantheheightdifferencetobemeasured.Thesedataaredifficulttointerpretaretheonesweneedtobringanimprovementintheprocess.Activities

Graph12.Concentration-graphactivityanddiffusivity-concentrationComparativemodegraphicsummaryoftheexperiment.

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MaximumActivity

Graph13.Waterabsorptionmaximum%activityTo finish the experiment the maximum possible activity was reached andabsorption was caused from 0 atm. The goal was to make the biggest jumppossible.Todothis,aftercarryingoutthevacuum,thewaterwasevaporatedwiththevalveofthecolumnopen,maximizingthevolume.The experiment had an initial pressure of 57,58mbar after leaving it to rest allweekend2daysand18:50hoursthepressurewas50,49mbar.Thedifferenceinheightof321.52to320.45=1.07pixel.Diffusivity1*10-8cm/s2.Inthegraphyoucanseehowduringthenighttheheightvariedconsiderably,itislogical due to the inevitable temperature drop. Obviously, the oscillations in theinitial times aremuch larger because the difference in pressures is the greatestexperienced.LDPE+35.5mgNeat3mLheptaneThenextstepintheproductionprocess,treatLDPEwithheptane.Thisexperimentabsorption50ppmisalsoexpected(0.134pixelto5*10-5gH20/gLDPE)asthatobtainedwithLDPENeat.The testswere also carried out various activities and completedwithmaximumactivityasinthepreviousexperiment.Vacuum

Graph14.Vacuumofthesample

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Avacuumpumpisusedtobringthesampleto0atmospheres,atwhichpointwecansaythatthereisnowaterinthesystem.Theinitialpressurewasatmosphericpressure, the final 0 atmospheres. There is a loss of height due to the buoyancyforceandthelossofthelittleamountofwater.Thedifferenceinheightwas349.64to339.44=10.20pixels.25%activity

Graph15.Waterabsorption25%activityThevariationinheightwas351.38-351.35=0.038pixel.Theinitialpressurewas13.87mbarafter1hour19minuteswas13.98mbar.Whilethediffusivity1*10-8cm/s2.Asyoucanseethereremainsaslightvariationinheight.Wateractivity50%

Graph16.Waterabsorption50%activityThe variation in height of 350.56 to 350.06= 0.5was pixel. The initial pressurewas32.44mbarafter44minuteswas32.44mbar.Thediffusivity3.2*10-8cm/s2.

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Wateractivity75%

Graph17.Waterabsorption75%activityThe initial pressure was 43.71 mbar after 39 minutes the pressure was 44.75mbar. The variation in height of 350.92 to 350.56 = 0.4538 was pixel. Anddiffusivity3.5*10-7cm/s2.Asshowninthegraph17toahighactivitythereisnohighabsorption.Thegraphmakesclearthatthereisgreatdifficultyininterpretingthedata,whichwillleadustostoptheexperimentsandremodelingprocess.Activities

Graph18.Concentration-graphactivityanddiffusivity-concentrationComparativemode, thesummarygraphof theexperiment. It isvisualizedas increasinghumidityincreasesdiffusivityandwaterabsorption.

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MaximumActivity

Graph19.Waterabsorptionmaximum%activityAgainthemaximumcapacitywasperformed.Withthevalveof thecolumnopen,maximizingthevolume.Thedifferenceinheightwas409.91to409.28=0.6366pixel.ChangeinprocedureThis was the last experiment in these conditions. A variation of 50ppm(0,134pixel)was expected, between the oscillations and changes in temperaturethedifference thatwanted tomeasurewas smaller than the experimental error.Thegraphicalexplanationisasfollows.

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Figure20.Experimentalerror50%NeatLDPEThegraphshowsthewaterabsorptionofthemembraneNeatLDPE50%ofactivityis represented. Aswe have already said they are very difficult to interpret. Thebottomblack line represents the average height of the sample before subjectingthe sample to the absorption. Yellow lines, the standard deviation of the data(error). Theupperblack line represents the averageheight of the sample at theend of the absorption and the red lines its standard deviation (the error). Theerror overlaps almost completely, which makes a change in the procedurenecessary.

Graph21.Experimentalerror75%NeatLDPE+heptane

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Increasing the activity reduces the overlapping error part. But it is not avoided,making all data unacceptable from the statistical point of view. Although thebiggest problem as we have already said the error is larger than the value youwanttomeasure.Tosolvetheexperimentalproblem,alenswasattachedtothecamerawithmuchmoremagnification,themembranewasapproachedtothemembraneandthesize(mass)ofthemembranedoubled.Itwentfromsamplesof35.5gramsto80grams.Whenapplyinganewobjectiveandbringingthecameracloserwewillhavemoreincreases, a pixel will correspond to more centimeters. As the sample sizeincreases,agreateramountofwaterwillbeabsorbed,increasingthemmthatthesamplemustdescendwhenabsorbingthemaximumamountofwater.With35mgtheywere00875mmandwith80mg0.02mm.Finally we will make only the maximum possible jump. We will produce theminimumpossiblehumidityandwewillmakeatotaldesorption.FinalexperimentAfterthecommentedmodifications,theexperimentwascarriedoutpayingspecialattention to the standard deviation. Expected results change as well. Sinceaccording to the article "Solubility and Diffusion of Water in Low-DensityPolyethyleneDavidW.McCall"avariationof50ppmisexpected.Wewillexpectanabsorptionof4E-6gH2O,whichwillmeanavariationinthespringof0.02mmand0.833pixels.Theproceduretobefollowedwasthefollowing,firstthebuoyancyofthesamplewas evaluated. Then the sample was saturated with the maximum possiblehumiditythatinnocasereached100%.Andfinallydesorptionwasperformedwiththevacuumpumpcausingthemaximumpossiblejump.

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80mgofNeatLDPESaturation

Graph22.ExposuretohighhumidityNeatLDPEThe red line represents the average height at the beginning of the experiment,purplethefinalheight.Avariationof5.454pixel,2,65E-05gH2O,331,349ppm.AnacceptablevariationsinceweareworkingwithwateringasphaseDesorption

Graphic23.DesorptionofNeatLDPE

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The jump in the desorption experiment must be equal in amount of watersaturationexperiment.Weseethattheerrorlinesareclearlyseparated.According to the experimental data, the difference between the average of theheightatthebeginningandendoftheexperimentwas4,515pixel,2,19E-05gH2O,273,978ppm.Practicallythesameaspreviousexperiment.LDPEpressedBuoyancy

Graph24.BuoyancypressedLDPEThe variation between the start and end in experiment buoyancy is almostnegligiblebecausetheinfluenceofthebuoyancyforceofthemembraneintheairislow.Itexperiencedavariationof0,662pixel,2,92E-6gH2O,36,6ppm.Verysmallcomparedwithotherexperiments.

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Saturation

Graph25.SaturationpressedLDPEThevariation in this experiment is again the samemagnitudeas theexperimentwithNeatLDPE.Inotherwords,theyabsorbthesameamountofwater.Errorlinesremaindistinct.Itexperiencedavariationof5,9249pixel,2,615E-5gH2O,326,9298ppm.AstheexperimentwithNeatLDPE.Desorption

Graph26.DesorptionpressedLDPE

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Again the variation in the desorption should equal in saturation. Since all theabsorbedwaterisdesorbed.Errorlinesoverlapminimally.The variationwas 2,5776pixel, 1,13E-05gH2O, 142,4118ppm. The variationwasconsiderablysmaller,maybeduetoexperimentalerrorsbuttheresultsarenotsodifferentastothinkthatthereisagreaterabsorptionthatsaturationdesorption.LDPE+HeptaneBuoyancy

Graph27.BuoyancygraphicLDPE+HeptaneThe variation between the start and end in the experiment is minimal, littleinfluenceofthebuoyancyforceofthemembrane.Variation0,3926pixel,1,826E-6gH2O,22,8348ppm.Saturation

Graphic28.SaturationLDPE+Heptane

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Thevariation in this experiment is again the samemagnitudeas theexperimentwithLDPEandLDPEpressedNeat.Thereisnodifferenceintheamountofwaterabsorbed.Itexperiencedavariationof3,0458pixel,1,419E-5gH2O,177,4848ppm.Waterabsorptionremainsthesamemagnitude.Desorption

Graph29.DesorptionLDPE+HeptaneThevariationinthedesorptionwasslightlyhigherthantheabsorption.Butwithinnormalvalues.Theerrorcontinueswithoutoverlapping.Thevariationinheightwas4,371pixel,2,0371E-5gH2O,254,6386ppm.

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LDPE+w+0.02andAOBuoyancy

Graph30.BuoyancyLDPE+0,02w+yAOAgain the variation between the start and end in the experiment buoyancy isalmostnegligible.Heexperiencedavariationof1,0225pixel,4,917E-6gH2O,61,465ppm.Verysmallcomparedwithotherexperiments.Saturation

Graph31.SaturationofLDPE+0,02w+yAO

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The variation in this experiment is again equal in magnitude to that of otherexperiments.Thereisnodifferenceintheamountofwaterabsorbed.Itexperiencedavariationof4,455pixel,2,141E-5gH2O,263,6059ppm.Nomajorchangesareseenintheamountofabsorbedwater.Desorption

Graph32.DesorptionLDPE+0,02w+yAOIn thedesorptionalsosignificantvariationswereobservedwithrespect tootherexperiments.Theerrorcontinueswithoutoverlapping.Thevariationinheightwas2.04169pixel,9,8999E-6gH2O,123,749ppm.6.ConclusionsInviewoftheresultswecandrawanumberofconclusions.Theinitialprocedurewasnotgoodenoughtogivethefirstresultsasvalid.Afterattaching another lens to the camera andduplicating the size of the sample, theresultsobtainedweremuchbetterThe error (standard deviation) was one of the most important factors for thechangeinprocedure.Sinceitcouldnotbejustifiedthattherewasacleardifferencebetweentheresultsatthebeginningandattheendoftheexperiments.

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Regardingtheresultsobtained:BouyancyNeatLDPE

LDPE +Heptane

LDPEpressed

LDPE+0,02w+YAO

0.3927 0.6629 1.0225 pixels

1.83E-06 2,93E-06 4,92E-06 g

22,83487 36,607077 61,46589 ppm

Saturation Neat

LDPELDPE+Heptane

LDPEpressed

LDPE+0,02w+YAO

5,455 3,046 5,925 4,455 pixels2,65E-05 1,42E-05 2,62E-05 2,14E-05 g331,3498 177,4848 326,9298 263,6059 ppmDesorption

NeatLDPE

LDPE+Heptane

LDPEpressed

LDPE+0,02w+YAO

4.5157 4.3715 2.5777 2.0417 pixels2,19E-05 2,04E-05 1,14E-05 9,90E-06 g273,97813 254,6386 142,4118 123,74929 ppmIt can conclude that there is a difference in the amount of absorbedwater. Thesaturation experiments are greater in terms of the amount of water. As for thedesorption,thereisacleardecrease..Recallingalreadyseenintheintroductorysection.Thethesisisbasedonanarticlepublishedin"McCall1983Solubilityanddiffusivityofwater inLDPE"[12]wherethe absorptionof liquidwater in Low-DensityPolyethylene (LDPE)was studied.FinalizingthestudyexplainingthattheLDPEabsorbed50ppm.In the present thesis absorption it is calculated 200 ppm but having beenperformedtheexperimentwithwatergas.Howeveritistryingtofindthetimeoftheprocessinwhichtheamountofwaterabsorbed increases as in the article "2017Influence of water uptake on theelectricalconductivityofinsulatingDC-LDPE/MgOnanocomposites"[4]amountsofwaterabsorbedmuchhigherthanthoseoftheexperimentwasanalyzedMcCall.Thereforewe can conclude thatwehave optimized theprocess so thatwehavereducedtheerrorandhaveapproachedthevalues foreseenbyMcCall.However,there is still a big difference. We know that our process can be affected byimpurities, temperature variations, etc. The future optimization of the processshouldbringidealsclosertovalues.

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7.BibliographyPengBL,DharN,LiuHL,TamKC(2011)."Chemistryandapplicationsofnanocrystallinecelluloseanditsderivatives:Ananotechnologyperspective"[1]Pääkkö,M.;M.Ankerfors;H.Kosonen;A.Nykänen;S.Ahola;M.Österberg;J.Ruokolainen;J. Laine; P.T. Larsson; O. Ikkala; T. Lindström (2007). "Enzymatic hydrolysis combinedwith mechanical shearing and high-pressure homogenization for nanoscale cellulosefibrilsandstronggels"[2]T.L. Hanley, R.P. Burford, R.J. Fleming, K.W. Barber, A general review of poly- mericinsulationforuseinHVDCcables,IEEEElectr.Insul.Mag.19(1)(2003)13e24.[3]

Influence of water uptake on the electrical DC-conductivity of insulatingLDPE/Mgnanocomposites, Nilsson, Karlsson, Pallon, Marco Giacinti, T,Olsson, DavideVenturi[4]

L.Pallon,A.Hoang,A.Pourrahimi,M.Hedenqvist,F.Nilsson,S.Gubanski,etal.,Theimpactof MgO nanoparticle interface in ultra insulating polyethylene nanocomposites for highvoltageDCcables,J.Mater.Chem.4(22)(2016)8590e8601.[5]

http://bibing.us.es/proyectos/abreproy/4102/fichero/2.+MATERIALES+POLIM%C3%89RICOS.pdf[6]Dennis Malpass (2010).Introduction to Industrial Polyethylene: Properties, Catalysts, andProcesses.JohnWileyandSons.pp.1–.ISBN978-0-470-62598-9.[7]"MarketStudy:PolyethyleneLDPE(2ndedition)".Ceresana.–[8]SuperiorityofDielectricPropertiesofLDPE/MgONanocompositesoverMicrocomposites,2009KazuyukiIshimotohttp://www.ugr.es/~ajerez/proyecto/t3-7.htm[9]Taylor,Ross;RKrishna(1993).Multicomponentmasstransfer.Wiley.[10]J.Crank,MathematicsofDiffusion,2nded,OxfordSciencePublications,Oxford,1975[11]“McCall1983SolubilityanddiffusivityofwaterinLDPE”[12]KTHRoyalInstituteofTechnology,SchoolofChemicalScienceandEngineering,FibreandPolymerTechnology,SE-10044,Stockholm,Sweden[12]

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