The sorption characteristics of different cellulose fibres by tensiometry

Zelo pomembna lastnost tekstilnih vlaken je njihova sposobnost navzemanja tekočin - njihova sorpcijska sposobnost. Za izboljšanje reaktivnosti regeneriranih celuloznih vlaken je običajno potrebna predobdelava, kot sta pranje in beljenje. Preizkušana viskozna in modalna ter liocel vlakna so enake kemične sestave, razlikujejo se v molekulski in nadmolekulski ureditvi. Razlike v sorpcijskih lasnostih neobdelanih in predobdelanih regeneriranih celuloznih vlaken smo zasledovali z alternativno metodo - tenziometrijo ter rezultate primerjali s klasično metodo zasledovanja hidrofilnosti. Tenziometrija je analizna metoda za določevanje površinske napetosti, stičnega kota ter adsorpcije. S pomočjo Powder Contact Angle metode smo določili kapilarno hitrost preskušanih vzorcev, na osnovi tega pa izračunali stični kot med trdno (vlakno) in tekočo (voda/heptan) fazo. S postopki predobdelave se sorpcijske lasnosti regeneriranih celuloznih vlaken bistveno izboljšajo, kar ugodno vpliva na nadaljne faze plemenitenja. Največjo sorpcijsko sposobnost navzemanja vode in s tem najnižji stični kot med neobdelanimi vzorci vlaken imajo viskozna vlakna (▫$varphi 68,3^o$▫), največji stični kot (▫$varphi 77,1^o$▫) pa modalna vlakna. Na izboljšanje sorpcijskih lastnosti ima največji vpliv predobdelava beljenje, kjer prav tako dosežejo najnižji stični kot beljenja viskozna vlakna (▫$varphi 57,8^o$▫).The improvement of wettability and sorptivity is the major task of textle finishing. In order to create the proper sorption character of regenerated cellulose fibres different pretreatment processes are applied, such as washing and bleaching. Classical viscose, modal and a new type of regenerated cellulose fibres called lyocell, have the same chemical structure, but a different molecular and supramolecular structure. The differences in the sorption properties of untreated and pretreated regenerated cellulose fibres were obtained using a new alternative method - tensiometry and compared with various methods for determining water adsorption. Tensiometry is an analytical method for measuring surface tension, contact angles and adsorption. We measured the sorption abilities using the Powder Contact Angle Method, and as a result we get the capillar velocity. From the velocity we can calculate the contact angle between the solid - fibres and the liquid - water/heptane. The pretreatment increases the adsorption abilities and makes the material more accessible to chemicals used in finishing processes. The raw viscose fibres show the highest amount of moisture and have the lowest contact angle (▫$varphi 68,3^o$▫), raw modal fibres have the biggest contact angle (▫$varphi 77,1^o$▫). Using chemical bleaching we improve the the sorption abilities. The bleached viscose fibres have the lowest cintact angle (▫$varphi 57,8^o$▫)

Hydrophilic/Hydrophobic Characteristics of Diffferent Cellulose Fibres Monitored by Tensiometry

Wettability and sorptivity improvements for different textile materials are the major tasks during textile finishing. In order to improve the sorption characteristics of a cellulose fabric, different pre-treatment processes are applied, usually washing, bleaching and mercerisation. Differences in the sorption properties of un-treated and pre-treated (washed and bleached) regenerated cellulose fibres were obtained using tensiometry and compared with the classical method for determining moisture adsorption. Results show that compared to raw fibres, viscose fibres have the highest moisture and the smallest contact angle whilst modal fibres have the biggest contact angle. Pre-treatment increases the sorption abilities and makes the material more accessible to Chemicals used in the finishing processes. Using the conventional method, it can be confirmed that fibres with the highest moisture have the smallest contact angle (tensiometry)

Tenziometrijsko praćenje hidrofilnih i hidrofobnih značajki različitih celuloznih vlakana

Wettability and sorptivity improvements for different textile materials are the major tasks during textile finishing. In order to improve the sorption characteristics of a cellulose fabric, different pre-treatment processes are applied, usually washing, bleaching and mecerisation. Differences in the sorption properties of untreated and pretreated (washed and bleached) regenerated cellulose fibres were obtained using tensiometry and compared with the classical method for determining moisture adsorption. Results show that compared to raw fibres, viscose fibres have the highest moisture and the smallest contact angle whilst modal fibres have the biggest contact angle. Pretreatment increases the sorption abilities and makes the material more accessible to chemicals used in the finishing process. Using the conventional method, it can be confirmed that fibres with the highest moisture have the smallest contact angle (tensiometry).Poboljšanje vlažljivosti i sorptivnosti tekstilnih vlakna najvažnije su zadaće pri završetku izrade tekstila. Kako bi se poboljšale sorpcijske značajke celuloznih vlakana u njihovoj predobradbi rabe se razni postupci, najčešće ispiranje, izbjeljivanje i maceriranje. Razlike u sorpcijskim svojstvima neobrađenih i predobrađenih (ispranih i izbijeljenih) regeneriranih celuloznih vlakana istražene su tenziometrijom i uspoređene s klasičnim postupkom određivanja adsorpcije vlage. U usporedbi sa sirovim vlaknima, viskozna vlakna imaju najmanju vlažnost i najmanji kut kontakta, dok modalna vlakna imaju najveći kut kontakta. Predobradbom se povećavaju sorpcijska svojstva i pristupačnost raznim kemikalijama u završnim postupcima obradbe. Rabljenjem standardnih postupaka potvrdili smo da vlakna najveće vlažnosti posjeduju najmanji kontaktni kut, što je dokazano tenziometrijom

Self-cleaning textiles based on nano TiO2TiO_2 coatings

V prispevku je opisan postopek priprave samočistilnih poliestrnih (PES) tekstilij s fotokatalitičnimi $TiO_2$ nanonanosi. Samočistilno površino smo pripravili s sol-gel procesom in proučili vpliv pogojev postopka na oblikovanje nanonanosov na vlaknih. Pri postopku polikondenzacije nanodelcev $TiO_2$, smo uporabili kisli in bazični katalizator. Pri toplotni obdelavi nanodelcev na poliestrnem substratu se je tvorila polimorfna kristalna $TiO_2$ struktura anataz, ki ima širšo optično vrzel v frekvenčnem pasu kot kristalna oblika rutil. Obdelane tekstilije smo analizirali, da bi določili vpliv postopka obdelave na njihove uporabne lastnosti. Raziskava je potrdila, da s sol-gel postopkom oblikujemo nanonanose s samočistilno sposobnostjo, vendar pa imajo boljše fotokatalitične sposobnosti $TiO_2$ nanosi, pridobljeni iz kislega sola. Postopek obdelave poliestrnih pletiv s $TiO_2$ nanonanosi ni pomembno vplival na mehanske lastnosti PES pletenin.The aim of this research was to obtain self-cleaning properties of PES surfaces by nano-modification with $TiO_2$ coatings. The sol-gel process was used to prepare $TiO_2$ nanoparticles and the influence of process conditions on the formation of nano-coatings was studied. Acid and alkaline catalysts were used in the polycondensation process of $TiO_2$. The heat treatment of nanoparticles on the polyester substrate caused the formation of a polymorphic form of $TiO_2$ anatase which has a wider band gap than the crystal structure rutile. To determine the efficiency of the fibre nano-modification and influence of the treatment on the fibre properties, the photocatalytic activity was observed by Foron Brill. Violett EBIN degradation and the mechanical properties were determined. The results show that the photocatalytic properties of $TiO_2$ coatings obtained from acid sol are higher than those obtained from alkaline sol. However, the influence on mechanical properties of PES knitted fabrics was insignificant irrespective of the treatment conditions used in the process

The influence of structural properties on the dye diffusion and dyeability of PA 6 fibres

The relationships were investigated between the structural and dyeing properties of different structurally modified PA 6 fibers. PA 6 monofilament yarn samples were applied having different crystalline degrees and different content of alpha, respectively gamma crystalline modification. The diffusion coefficients of two different acid dyes were determined together with the content of dyestuff absorbed (under specific conditions) by fiber samples. In order to estimate colorimetry method from the viewpoint of polymer structural change detection, the colors of the dyed PA 6 samples were determined (L*, a*,b*, C*, h coordinates) and the color differences (L*, a*, b*, C*, H*, E*) were calculated between untreated standard and structurally modified samples. The dyeability of PA 6 fibers depended mainly on the way in which crystallinity had been achieved, i.e. on the materialćs history. Different crystalline modifications caused different sorption properties and fiber dyeability. Smaller increases (app 20%) of crystallinity degree caused a decrease in diffusion coefficients. Contrary to expectations, the significant increase of crystallinity degree (app 50%) had an influence on the increase ofdyeability, presumably owing to the formation of larger empty spaces in the structure. The results achieved by colorimetry were in good correlation with dye absorption measurements. The colorimetry of dyed fiber samples was sensitive enough to detect even small differences in the quantities of absorbed dyestuff

The interaction ability of cellulosic materials as a function of fine structure and Helmholtz surface energy

Many chemical or physical modification processes significantly influence the accessibility of fiber forming polymers by causing structural changes. The wettability and sorption ability improvements of polymeric materials are major tasks during finishing processes. Different pre-treatment processes are used in order to improve the accessibility of dissociable groups, hydrophilicity, dyeability, and whiteness. These are usually alkaline purification, chemical bleaching and mercerization. In a previous paper we presented the data for structural characteristics (density, crystallinity index, molecular orientation, void volume, diameter and the specific inner surface of void, etc.) of untreated regenerated cellulose fibers (viscose, modal and lyocell) [41]. We now compare the influence of different pre-treatment processes on fiber structure and the accessibility of the chemical groups of these fibers. In order to improve the accessibility, two pre-treatment processes were used: chemical bleaching of fibers and tensionless alkali treatment. The influence of these pre-treatment processes on the structure parameters was evaluated using viscosity measurements (determination of polymerization degree (DIN 54 270)) and iodine sorption ability measurements according to the Schwertassek method (determination of crystallinity index) [13, 16]. The reactivity and accessibility in a polar environment was determined using tensiometry. Contact angles between the fibers and liquids of different polarities were determined using the powder contact angle method and calculated from a modified Washburn equation [26, 28]. The surface free (Helmholtz) energy of differently treated fibers was determined from the contact angle data using the Owens-Wendt-Raeble-Kaelble approximation [30, 33, 35]. The differences in the accessibility of raw and pre-treated regenerated cellulose fibers obtained using tensiometry are compared with the results of the conventional method used to determine moisture adsorption (DIN 54 351, DIN 53 802). In regard to raw fibers, viscose shows the most hydrophilic characteristic: adsorbs the highest amount of moisture, has the fastest penetration velocities (Fig. 6), the smallest contact angle, and the highest SFE (Fig. 8). Modal fibers have the largest contact angle, the lowest SFE, and they adsorb the smallest amount of water vapor. Pre-treatments increase the sorption ability and the surface free (Helmholtz) energy while they decrease the contact angle. This makes the material more accessible to water and chemicals used in the finishing processes although the crystallinity index increases. The main modification in polymer properties caused by the treatments is an increase in the fiber SFE caused by an increase of the fiber surfaces because of swelling in the alkaline medium (washing, slack-mercerization), and due to an increase of accessible OH- and COOH-groups (bleaching). This enables the formation of an increased number of hydrogen bridges between the water molecules and the OH- and COOH-groups. Our investigations confirm the results published earlier thatthe main property necessary for the proper sorption behavior of cellulose materials are the accessible, less ordered regions and not the degree of crystallinity

Characterisation of grass fibres

The elementary grass fibres were isolated from different grass and legumes sorts, i.e. Ryegrass (Lolium hybridum Gumpenstein), Wheat straw, Trefoil (Trifolium pratense) and Lucerne (Medicago sativa). The fibre-samples were obtained in a bio-refinery, after the liquid phase containing proteins and lactic acid was eliminated from the ensiled and green grasses, respectively. For the isolation of elementary grass fibres different processes were used. The morphological characteristics of stems and leaves of different grass species were microscopically observed. On the microscopical stem and leaves cross-section samples the quantification of fibres sclerenchyma cells was performed. The quantitative analysis was carried out in order to obtain basic quantitative data on grass fibres, such as area of the single fibre or group of fibres, diameter of a single fibre or group of fibres and distances betweenthe most distant and least distant points on the area of the fibre. Measurements were made using a Carl Zeiss software KS 300, which runs on a computer connected to the image analysis equipment consisting of a microscope and a digital camera. In addition to, geometrical and mechanical properties ofisolated fibres and fibre bundles were determined. Due to the grass history,i.e. deformations and damages caused by the treatment of grasses in the bio-refinery, maturity grade, grass or legumes type and conditions during grass growth, the plant structures vary considerable in their properties

X-ray study of pre-treated regenerated cellulose fibres

Regenerated cellulose fibres have had an important role to play in the man-made fibre field. The very special characteristics of different types of regenerated cellulose fibres, e.g. mechanical properties, sorption characteristics, and aesthetics were conditioned by the differences in their fine structure due to fibre formation processes. Additionally, the finishing processes could influence the fibre structure. A study was done of the crystalline structures of a solvent-spun cellulose fibre type (Lenzing Lyocell), made according to the NMMO process, and two conventional cellulosic fibre types, made by the viscose process (Lenzing Viscose and Lenzing Modal). The fibres were pre-treated (bleached and slack mercerised) and structural changes were followed by wide angle and small angle x-ray scattering (WAXS and SAXS), respectively. The periodical structure, determined by long spacing, was nearly the same in all the different types of fibres. A slight increase was observed after the treatment of viscose and modal fibres, but an unpronounced fall of a long period accompanied the pre-treatment of lyocell fibres. Some changes in crystallinity and crystalline orientation occurred due to the treatment conditions. The structural changes were correlated to the iodinesorption and mechanical properties

Flax fibres sorption properties influenced by different pretreatment processes

The sorption behavior of raw and treated flax fibers was investigated. This paper presents the effect of conventional pretreatment processes (alkaline, acid) in comparison to environment-friendly enzymatic processes on the sorption ability of flax fibers. Weight-loss, moisture sorption, water retention value and contact angle were determined in order to interpret the pretreatment results. In addition, the influence of the process on the fibers\u27 mechanical properties was studied. The ecological parameters of the treatment wastewaters were analyzed

Sustainable plant textile fibres

Zaradi čedalje globlje ekološke ozaveščenosti in okoljevarstvenih zahtev obravnavamo v sodobnem času izdelavo, uporabo in odstranjevanje materialov veliko bolj kritično. Naravna celulozna vlakna so v tem pogledu izkazala svojo kakovost in popolnoma izpolnila vse ekološke kriterije. Naravna celulozna vlakna uporabljamo za tekstilne in tekstilnotehnične namene. To so vlakna iz ličja stebel, ki tvorijo vlaknate snopiče v notranjem ličju stebel dvokaličnic, in listna vlakna, ki tečejo po dolžini listov enokaličnic, ter semenska vlakna in vlakna iz plodov. Lan, konopljo, juto, ramijo, sisal ter kokos uporabljamo predvsem za tehnične namene. V zadnjem času pa izjemno narašča zanimanje za obnovljive surovinske vire tudi na področju vlaken. V ospredju so vlakna rastlinskega izvora. Pri iskanju novih surovinskih virov se proučujejo številne rastline, ki ne spadajo med tradicionalne vire vlaken, da bi iz njihovih stebel ali listov izolirali vlakna uporabnih lastnosti. Pri izolaciji vlaken pridobimo tehnična vlakna, kar pomeni, da so celulozna vlakna večcelične strukture, pri katerih so posamezne celice vezane v snopiče. Poleg konvencionalnih načinov izolacije vlaken se uporabljajo tudi številni sodobni postopki, kot so biotehnološki z uporabo encimov, itd. Način, kako vlakna izoliramo, vpliva na površinsko morfologijo vlaken. V prispevku so predstavljena nekatera vlakna, ki jih pridobivamo iz kmetijskih odpadkov, kot so slama žitaric, listi ananasa, sladkorni trs, hmeljeva stebla, kinoa, vlakna iz različnih trav itd.The manufacture, use and removal of traditional materials are now considered more critical due to increasing environmental consciousness and the demands of legislative authorities. Natural cellulose fibres have successfully proven their qualities when also taking into account an ecological view of fibre materials. Different cellulose fibres can be used for textile and technical applications, e.g. the bast or stem fibres which form fibrous bundles in the inner bark (phloem or bast) of the stems of dicotyledenous plants, the leaf fibres which run lengthwise through the leaves of monocotyledenous plants, and the fibres of seeds and fruits. Flax, hemp, jute, ramie, sisal and coir are mainly used for technical purposes. Recently, the interest in renewable resources for fibres particularly of plant origin has increased. Therefore, several non-traditional plants are being studied with the aim to isolate fibres from plant leaves or stems. A review of some untraditional fibres is given in the paper. Technical fibres are mainly obtained with fibre isolation, which means that cellulose fibres are multicellular structures with individual cells bound into fibre bundles. Different retting processes can be performed in both acid and alkaline mediums, respectively, and with an enzymatic treatment. The used procedure influences the fibre surface morphology. Some biofibres from agricultural by-products, e.g. wheat straw, pineapple leaves, sugarcane bagasse, hop stems, Musaceae plants, quinoa etc. are introduced. In addition, the fibres from different grass and legume species and from sea grass are presented in the article