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Nanosilica-Chitosan Composite Coating On Cotton Fabrics Dina Kartika Maharani*, Indriana Kartini and Nurul Hidayat Aprilita *Chemistry Department, Universitas Negeri Surabaya, Ketintang Surabaya 60231,Email : dkmaharani@gmail.com Phone : +628174140131 Abstract. Nanosilica-chitosan composite coating on cotton fabrics has been prepared by sol-gel method. The sol-gel procedure allows coating of material on nanometer scale, which several commonly used coating procedure cannot achieve. In addition, sol-gel coating technique can be applied to system without disruption of their structure functionaly. The coating were produced via hidrolysis and condensation of TEOS and GPTMS and then mixed with chitosan. The composite coating on cotton fabrics were characterized with X-Ray Diffraction and Scanning Electron microscopy (SEM) method. The result showed that the coating not changed or disrupted the cotton stucture. The coating result in a clear transparent thin layer on cotton surface. The nanocomposite coating has new applications in daily used materials, especially those with low heat resistance, such as textiles and plastics, and as an environmentally friendly water-repellent substitute for fluorine compounds.. Keywords: Nanocomposite, Coating, Silica, Chitosan , Cotton Fabrics. PACS: Replace this text with PACS numbers; choose from this list: http://www.aip.org/pacs/index.html
INTRODUCTION Nowadays composite material are widely used in various aplications ranging from household goods, electrical components, and contraction material to automotive parts and the aerospace industries. Nanocomposite materials differ from the traditional composite material in that they provide enhanced properties. A nanocomposite is a distinctive form of composite material, which is comprised of an inorganic filler with at least one dimension in the nanometer range into an organic polymer, metal or ceramic matrix material [1]. Due to nanocomposite’s excellent mechanical properties, such as good rigidity, dimensional stability, thermal stability, good toughness and piezoelectricity, many potential applications can be developed in modern industry fields including electronics, optics, machinery, biology, etc [2]. Most of today’s research activities on nanocomposites is on polymer-based nanocomposites or organic-inorganic nanocomposite. Organicinorganic nanocomposite have been used in several fields in order to increase the mechanical, thermal and optic properties of material, such as rubber, adhesive, plastic, fiber and in coating processes [3]. The nanocomposite coating has new applications in daily used materials, especially those with low heat resistance, such as textiles and plastics, and as an environmentally friendly water-repellent substitute for
fluorine compounds [4]. Coating is simply the act to covering material with a layer; hence nanocoating is either to cover with a layer on the nanometer scale or to cover nanoscale entity. Nanocoating is usually performed using sol-gel process. The sol-gel procedure allows coating of material on nanometer scale, which several commonly used coating procedure cannot achieve. In addition, sol-gel coating technique can be applied to system without disruption of their structure or functionality. The sol-gel process involves inorganic precursors that undergo various reactions, commonly hidrolysis and condensation reactions, resulting in the formation of a three dimensional molecular work. Coating using sol-gel process usually involves electrostatic interaction, hydrogen bonding and covalent bonding as the associating forces between the coating and the material being coated [5]. The sol-gel coatings are the most popular technique in the functionalisation of textile. There are so many reasons for the interest to using the sol-gel coating to functionalise textile, one is sols based on metal oxides or modified silica with particle diameters smaller than 50 nm (nanosol) form well adhering transparent oxide layers on textiles and such layers improve the mechanical properties of textiles. The solgel coating on textiles with nanocomposite is also could improve several properties of textiles such as improved stability against mechanical or thermal destruction and bacteria attack, improved water, oil and soil repellency, etc. In the case of the treatment of
cotton, the pure silica sols which are modified with epoxysilane like glycidoxypropyltrimethoxysilane (GPTMS) could enhancing mechanical stability. Due to the particular interest in textile coatings to prevent biocontamination, the sol-gel coating can be prepare with biocidal properties using antimicrobial compounds such as chitosan, triclosan, QAS compound, biguanids (poly(hexamethylen)-biguanide), etc [6]. In this paper, we report the formation and characterization of transparent layer on cotton fabrics using nanosilica-chitosan composite. The silica composite is produced via cohydrolysis and polycondensation of tetraethoxyorthosilcate (TEOS), and also modified with epoxysilane 3glycidoxypropyltrimethoxysilane (GPTMS) then mixed with chitosan. The coating is applied on cotton fabrics using dip-coating technique and pad-dry-cure method. The composite coating on cotton fabrics is characterized with XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy) method.
Coating Process We prepared the nanocomposite film coatings on cotton substrates of 3 x 6 cm dimension. The substrates were washed using etanol to remove wax, grease, and other finishing chemicals from the fabricss before they were coated. The scouring process was performed at room temperature for 10 min. The cleaned substrates were dipped in the mixture of modified silica sol or silica sol and chitosan solution 10 times with rate ~24cm/min. The substrates were air dried for 30 min. After this, the cotton substrate then dried at 80 oC for 5 min and finally cured at 140°C for 3 min in a preheated curing oven. The structure and morphology of these coatings were investigated using XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy) method.
RESULT AND DISCUSSION Modification Of Silica With GPTMS (Epoxysilica)
EXPERIMENTAL Preparation Of Nanosilica-Chitosan Composite The modified silica sol was prepared by mixing TEOS (98% Merck, PA), GPTMS (97%, SigmaAldrich), and HCl (Merck) in ethanol (99.8%, Merck) using various molar ratios [7]. The silica sol was prepared by mixing TEOS (98% Merck, PA), and HCl (Merck) in ethanol (99.8%, Merck) using various molar ratios. The solution then stirred for 24 h at room temperature. Chitosan was prepared from Ndeasetylation chitin isolated from crab shell with NaOH 50 %. The chitosan solution was obtained by dissolved chitosan in 2% acetic acid solution. The mixture of modified silica or silica sol and chitosan solution (%w/w ratio = 60 : 40) then was stirred further for 30 min at room temperature. Thus, nanosilica-chitosan composite produced was characterized with XRD (X-Ray Diffraction) method.
Fig. 2 presents the XRD pattern of nanosilicachitosan composite that is prepared from mixture of modified silica sol or silica sol and chitosan with composition of molar is showed in Table I. The decreasing peak is observed in the nanoepoxysilicachitosan and nanosilica-chitosan composites, at 2θ = 10.12o and 20.54o compared with chitosan. This indicate that the nanoepoxysilica and nanosilica chenge the crystalinity of chitosan into amorf form when they are in composite system. This also indicate that chitosan interact with nanoepoxysilica and nanosilica resulted in the increasing of crystalinity disorder of chitosan in composite system. The absence of new peaks in all of nanocomposite pattern show that there is no chemical bonding between chitosan and nanoepoxysilica or nanosilica. The interlayer distance of composite enlarge as its epoxy content exist. It reveals that chitosan chain inserted into layered silicates of nanoepoxysilica or nanosilica and the intercalated nanocomposites have formed [8]. The interlayer distance (d) of nanoepoxysilica-chitosan composite is 8.73 nm larger than nanosilica-chitosan composite is 8.52 nm at 2θ = 10.12o. The fact maybe because the modified silica sols with epoxysilica (GPTMS) has greatly increase the disorder of chitosan’s crystalinity in composite system.
FIGURE 1. The Structure of GPTMS
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FIGURE 1. The XRD Pattern of (a) Chitosan (b) Nanoepoxysilica-chitosan composite (NESC) (c). Nanosilica-chitosan composit (NSC) (d). Nanoepoxysilica (NE)
FIGURE 2. The XRD Pattern of (a) Cotton (b). Chitosan coated cotton (c) Nanoepoxysilica-chitosan coated cotton (d). Nanosilica-chitosan coated cotton.
TABLE 1. Molar Composition Of Nanocomposite Composite % Epoxy in TEOS Nanoepoxysilica 11 % Nanosilica 0% Structure and Morphology Of NanosilicaChitosan Composite Coating On Cotton Fabrics Coating of Nanosilica-Chitosan on cotton substrate with dip-coating method and pad-dry-cure technique allow the solution molecules disperse in the cotton fabrics’s fibers. The dry step allow the
vaporization of water molecules and solvent molecules further happen, so that the condensation reaction to form gel occur. The cure step generate the stabilization of nanosilica-chitosan composite’s thin layer on cotton fabrics, due to the condensation reaction of nanoepoxysilica and nanosilica can occur further to form polymeric network or crosslinking which liberate water and solvent molecules [9]. The coating process of nanosilica-chitosan composite give the wet pick up of chitosan and nanosilica-chitosan on cotton fabricss as showed in Table 2.
TABLE 2. Wet Pick Up Content of Nanocomposite Coated Cotton Coating Material On Cotton Fabricss Chitosan Nanoepoxysilica-Chitosan Nanosilica-Chitosan
% Wet Pick Up 78.23 113.54 114.82
Fig. 3 shows the XRD pattern of chitosan, nanoepoxysilica-chitosan and nanosilica-chitosan coating on cotton fabricss. It can seen from the figure that the coating process of chitosan, nanoepoxysilicachitosan composite and nanosilica-chitosan composite on cotton fabbrics do not disrupted the fibers’s structure. The fact can tell us that the sol-gel coating can be applied to delicate systems without disruption of their structure or functionality [10]. The diffraction peaks of nanoepoxysilica-chitosan composite and nanosilica-chitosan composite on cotton fabricss are overlapped by the big and broad peak of cellulose [11]. It may indicates that nanoepoxysilica-chitosan composite and nanosilica-chitosan composite on cotton fabrics dominantly form chitosan layer in the outer layer of composite system and the silicates layer are in the inner layer of composite system between cellulose and chitosan. It also suggests that the epoxysilica and silica in the composite system could be act as crosslink agent. The XRD pattern of cellulose shows the characteristic peaks of cellulose at 2θ = 14.5o, 16.5o and 22.5o that is reflected the 11� 0, 110 and 020 crystal plane [12]. It can be seen from the figure that the peaks intensity of cellulose at 2θ = 14.5o, 16.5o and 22.5o in all of nanocomposite’s pattern increase from chitosan coated cotton to nanoepoxysilica-chitosan. In comparison with chitosan, the lattice intensity of nanoepoxysilica-chitosan and nanosilica-chitosan are greater. This fact indicates that the coating of nanoepoxysilica-chitosan composite and nanosilicachitosan composite improve density of cellulose’s crystal unit with its particle more than chitosan [13]. The amount of silica content in the cotton coated with nanoepoxysilica-chitosan composite and nanosilicachitosan composite is also reported in this study by absorption spectroscopy analysis which is result showed in Table 3. The amount of silica content in the nanosilica-chitosan composite is greater than in the nanoepoxysilica-chitosan composite. It is due to the smaller chain of silica polymeric compared with epoxysilica chain result in the greater amount of silica particles absorbed in the cotton substrate. The data in Table 3 appropriate with the XRD analysis in which the peaks intensity of nanosilica-chitosan composite is greater than nanoepoxysilica-chitosan composite.
TABLE 3. Silica Content on Cotton Fabricss Composite on Cotton Silica Content (ppm) Nanoepoxysilica-Chitosan 11486.44 Nanosilica-Chitosan 14008.83 Fig. 4 display the SEM micrographs of cotton fabricss coated with chitosan, nanoepoxysilicachitosan composite, nanosilica-chitosan composite and uncoated cotton fabricss. It can be seen from the figure that all of nanocomposite coat the cotton fiber indicate the interaction between cotton substrate with chitosan, nanoepoxysilica-chitosan composite and nanosilicachitosan composite. The coating on the cotton substrat with chitosan and nanosilica-chitosan composite have similarity in the case of the type of coating result. They coat each part of cotton fiber and give unsmooth thin layer. The coating on cotton fabricss with nanoepoxysilica-chitosan composite give more smooth thin layer on cotton fiber and it coats not only each part of cotton fiber but also between one fiber to others.
FIGURE 4. The SEM Micrograph of (a). Uncoated Cotton (b) Chitosan Coated Cotton (c) NSC-Coated Cotton (d) NESC-Coated Cotton CONCLUSION In this study, nanosilica-chitosan composite coating on cotton fabrics were succesfully prepared by sol-gel process with dip-coating method. A thin layer of nanosilica-chitosan composite were formed on cotton fiber. From the XRD analysis, it can be concluded that a coating of nanosilica-chitosan composite on cotton fabrics didn’t disrupted its structure. It is also founded from SEM analysis that nanosilica-chitosan composite interact with each cotton fiber to give a thin layer on its surface. The modified silica sol with epoxysilica (GPTMS) were given a different type of coating on cotton fiber due to its polymeric chain properties.
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