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Accepted Manuscript Title: Silica–cellulose hybrid aerogels for thermal and acoustic insulation applications Author: Jingduo Feng Duyen Le Son T Nguyen Tan Chin Nien Victor Daniel Jewell Hai M Duong PII: DOI: Reference: S0927-7757(16)30504-0 http://dx.doi.org/doi:10.1016/j.colsurfa.2016.06.052 COLSUA 20779 To appear in: Colloids and Surfaces A: Physicochem Eng Aspects Received date: Revised date: Accepted date: 8-4-2016 31-5-2016 26-6-2016 Please cite this article as: Jingduo Feng, Duyen Le, Son T.Nguyen, Tan Chin Nien Victor, Daniel Jewell, Hai M.Duong, Silica–cellulose hybrid aerogels for thermal and acoustic insulation applications, Colloids and Surfaces A: Physicochemical and Engineering Aspects http://dx.doi.org/10.1016/j.colsurfa.2016.06.052 This is a PDF file of an unedited manuscript that has been accepted for publication As a service to our customers we are providing this early version of the manuscript The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain Highlights: Silica–cellulose aerogels were successfully developed from recycled cellulose fibres and methoxytrimethylsilane (MTMS) silica precursor for the first time The silica–cellulose aerogels showed the super-hydrophobicity with an average water contact angle of 151o The silica–cellulose aerogels developed in this work showed a promising potential for thermal and acoustic insulation applications This work provides a facile approach to fabricate cost-effective silica–cellulose aerogels with industrial dimensions Silica–cellulose hybrid aerogels for thermal and acoustic insulation applications Jingduo Feng1, #, Duyen Le2, #, Son T Nguyen2, Tan Chin Nien, Victor1, Daniel Jewell3, Hai M Duong1,* Department of Mechanical Engineering, National University of Singapore, Engineering Drive 1, Singapore 117576 Faculty of Chemical Engineering, Ho Chi Minh City University of Technology, VNU-HCM, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam Department of Materials Science and Metallurgy, University of Cambridge, UK * Corresponding author: mpedhm@nus.edu.sg # Equal contribution Keywords: Aerogel; recycled cellulose fibre; silica; acoustic insulation; thermal insulation Abstract Silica–cellulose aerogels were successfully developed from recycled cellulose fibres and methoxytrimethylsilane (MTMS) silica precursor for the first time The developed silica– cellulose aerogels showed the super-hydrophobicity with an average water contact angle of 151o Their thermal conductivity was approximately 0.04 W/mK Moreover, the thermal degradation temperature for the cellulose component of the silica–cellulose aerogels showed a 25 oC improvement over those for cellulose aerogels The sound absorption coefficients of the silica–cellulose aerogels with a 10 mm thickness were 0.39–0.50, better than those of cellulose aerogels (0.30–0.40) and commercial polystyrene foams When the cellulose fibre concentration increases from 1.0 to 4.0 wt %, the compressive Young’s modulus of the silica–cellulose aerogels can be enhanced 160%, up to 139 KPa This work provides a facile approach to fabricate cost-effective and promising silica–cellulose aerogels with industrial dimensions for thermal and acoustic insulation applications Introduction Global warming is one of the essential reasons for irrevocable sea level rise and climate disasters [1] Most scientists believe that greenhouse emission is a major cause of global warming [1, 2] As a matter of fact, in the developed countries, more than 30% of the total greenhouse gas emission is caused by buildings [3] Moreover, the recent rapid development of developing countries has led to a growth of greenhouse gas emission from buildings, as more buildings have been equipped with air-conditions One possible solution to this problem is to integrate the building with high performance thermal insulation materials Conventional insulation materials (mineral fibres and polyurethane foam) with high sensitivity to moisture still have the largest market shares, because of the best performance per unit cost [4] Hence, fabrication of inexpensive thermal insulation materials with reasonable thermal conductivity and high moisture resistance is in need In addition, noise is one of the major environmental challenges of the current world, considered as the most widespread and least controlled environmental pollutant [5, 6] Noise can cause negative health effects, such as loss of hearing, high blood pressure, and increased physiologic stress [7, 8] Some works have been conducted to investigate the acoustic insulation properties and applications of silica aerogels [9] However, their brittleness and high cost hinder their industrial development To our best knowledge, there have been few reports on the acoustic insulation properties of cellulose-based aerogels Therefore, in this work, the acoustic insulation properties of the silica–cellulose aerogels and their cellulose matrices were explored by an industrial approach for the first time Moreover, 360 million tonnes of paper-related waste were generated in 2004, and paper and paperboard consumption is likely to keep increasing by approximately 2.1% each year until 2020 [10] The above facts imply huge amount of paper waste is generated every day Incineration or land filling of paper waste can further pollute the environment, due to toxic emissions and groundwater contaminations Even though waste paper can be converted to recycled paper, the maximum convention rate is only 65% [11] The low convention rate is due to the length degradation of cellulose fibres during recycling process, and the degradation reduces the quality of the end products [11] After recycling process, the fibres with a short length are not suitable for further recycling, and are discarded by paper manufacturers [11] Hence, there is a necessity for developing alternative commodities from paper waste Aerogels may be a solution to the above environmental problems Aerogels, considered as a new state of matter, are materials with numerous unique properties, such as low thermal conductivity (0.012–0.045 W/mK), low density (0.001–2.06 g/cm3), high porosity (77–99.8%), and large surface area (81–1600 m2/g) [4, 12-15] Silica aerogels normally are fragile, but their thermal conductivities are low; while cellulose aerogels can be compressed to a strain of 80%, but their thermal conductivities are relatively higher than those of silica aerogels [12, 16] On the other hand, both cellulose materials and silica aerogels are outstanding acoustic insulation materials [9, 17] Researchers want to combine the outstanding properties of silica aerogels and cellulose aerogels Hence, the silica– cellulose aerogels become promising, and have attracted a lot of research efforts [12, 18-20] The silica–cellulose aerogels have thermal conductivities between those of their pure silica counterparts and pure cellulose counterparts, while the compressive moduli of the silica–cellulose aerogels surpass those of the pure silica or cellulose aerogels [12, 18, 19] However, no studies were available to fabricate silica–cellulose aerogels from recycled cellulose fibres that generated from paper waste Because cellulose aerogels synthesized from recycled cellulose fibres have much lower mechanical strength than that made from normal cellulose fibres, improvements on the mechanical strength of recycled cellulose aerogels are necessary [16, 21, 22] So, it may be a good attempt to combine silica aerogels with recycled cellulose aerogels for possible improvement on the mechanical strength Moreover, almost all the current effective methods to change silica loading of silica– cellulose aerogels were via varying the amount of silica precursors [12, 20, 23], which resulted in different nano-structures of the silica phases Shi et al changed silica loading without alternating the silica nano-structures, however, the maximum silica loading in the silica–cellulose aerogels was only 12% [24] It is interesting to investigate silica cellulose aerogels of higher silica loadings High silica loadings will improve the thermal stability of the composite aerogels due to the excellent thermal stability of silica and thus, enhance the fire retardant property of the materials [25] In addition, hydrophobicity helps them to withstand moisture, and contributes to the stability of their thermal insulation performance However, the available hydrophobic silica–cellulose aerogels in literature were all obtained via post-modifications of silica–cellulose aerogels [23, 24] In 2013, a CCl4 cold-plasma postmodification approach using gas ionization was applied on silica–cellulose aerogels, and the final aerogels have a water contact angle of approximately 132o [24] In the same year, a solvent-immersion method involving a 24 h aging followed by freeze drying was introduced for the hydrophobic modification of the silica–cellulose aerogels [23] Their water contact angle was approximately 133o, which was similar to that of the previous approach [23, 24] Both the methods might be considered as uneconomical because of either the expensive equipment or the large amount of chemicals and the long duration involved Moreover, the water contact angles of the modified composite aerogels were not super-hydrophobic In our study, cost-effective and superhydrophobic silica-cellulose aerogels were successfully prepared for the first time from recycled cellulose fibres and methoxytrimethylsilane (MTMS) Their morphology, hydrophobicity, thermal, sound insulation and mechanical properties were carefully investigated The materials showed promising thermal and sound insulation properties for practical applications Experiments 2.1 Materials and chemicals Kymene 557H was supported by Ashland (Taiwan) Recycled cellulose fibres were purchased from Insul-Dek Engineering Pte Ltd (Singapore) The recycled cellulose fibres and Kymene were used without further purification Methoxytrimethylsilane (MTMS), absolute ethanol, ammonium hydroxide, ammonium fluoride were of analytical grade, purchased from Sigma-Aldrich and used as received All the solutions were made with deionized (DI) water 2.2 Fabrication of silica–cellulose aerogels 2.2.1 Preparation of silica aerogels The catalyst solution was prepared by mixing 10.25 g of ammonium hydroxide, 0.927 g of ammonium fluoride in 50ml of DI water 6.5 ml of MTMS solution was mixed with 11 ml of ethanol and stirred for minutes to prepare the MTMS–ethanol mixture Then ml of DI water, 11 ml of ethanol, and 0.5 ml of the catalyst solution were mixed in another beaker for the DI water–ethanol–catalyst solution While the MTMS–ethanol mixture was still being stirred, the obtained solution of DI water–ethanol–catalyst was poured slowly into the MTMS–ethanol solution and stirred for another 15 minutes to form the silica sol The silica sol was poured into a mould, and then the gelation and the aging processes were conducted at room temperature (25 oC) for three days After solvent exchange of the gel with DI water for three days, the obtained hydrogel was frozen and dried by using a freeze dryer (ScanVac CoolSafe freeze dryer, Labogene, Denmark) for 24 h 2.2.1 Preparation of cellulose aerogels The hydrophobic recycled cellulose aerogels were fabricated using a cost-effective method developed in our lab [26] Recycled cellulose aerogels of different porosities were obtained by changing the amounts of recycled cellulose fibres (0.3, 0.6, and 1.2 g), and the ratio of the volume of Kymene to the weight of recycled cellulose fibres (Kymene: recycled cellulose fibres = 10 μl: 0.15 g) was fixed The recycled cellulose fibre concentrations inside the initial mixtures (30 mL) for the cellulose aerogel fabrications were 1, 2, and wt %, respectively 2.2.3 Preparation of silica–cellulose aerogels The catalyst solution was prepared by mixing 10.25 g of ammonium hydroxide, 0.927 g of ammonium fluoride in 50 ml of DI water 6.5 ml of MTMS solution was mixed with 11 ml of ethanol and stirred for minutes to prepare the MTMS–ethanol mixture Then ml of DI water, 11 ml of ethanol, and 0.5 ml of the catalyst solution were mixed in another beaker for the DI water–ethanol–catalyst solution While the MTMS–ethanol mixture was still being stirred, the obtained solution of DI water–ethanol–catalyst was poured slowly into the MTMS–ethanol solution and stirred for another 15 minutes to form the silica sol After the formation of the silica sol, the weighted hydrophobic cellulose aerogels (obtained from Section 2.2.2) with different cellulose concentrations (of 1, 2, and wt % inside the initial reaction mixtures for cellulose aerogel fabrications) were immersed into the silica sol Gelation and the aging processes of the mixtures were conducted at room temperature (25 oC) for three days After solvent exchange of the gel with DI water for three days, the obtained hydrogel was frozen and dried by using a freeze dryer (ScanVac CoolSafe freeze dryer, Labogene, Denmark) for 24 h 2.3 Characterization 2.3.1 Characterization of structure and morphology The morphology of the aerogel samples was investigated using a field-emission scanning electron microscopy (FE-SEM, Model S-4300 Hitachi, Japan) The samples were coated with a thin layer of gold by sputtering prior to FE-SEM The structures of the aerogels were confirmed with the aid of X-ray diffraction (XRD, 6000 Shimadzu, Japan) The Cu-Kα radiation source (λ=0.1506 nm) was applied In addition, the scan step was 0.02o and the rate of the scan step was 0.6 o/min in the range of 5–45o (2θ) The pore properties of the silica aerogels and silica cellulose composite aerogels were determined by nitrogen physisorption measurements with a Nova 2200e (Quantachrome) All the samples were degassed in vacuum at 80 oC for 24 h before measurement 2.3.2 Determination of SiO2 content in silica–cellulose aerogels Before the immersion of the cellulose aerogel into the silica sol, the weight of the cellulose aerogel was recorded as Wc After the freeze-drying, the total weight of the silica– cellulose aerogel was measured as Wt The cellulose content ( ωc ) and the SiO2 contents ( ωs are calculated as: ωc Wc Wt Wt Wc Wt ωs (1) (2) 2.3.3 Determination of water contact angle of silica–cellulose aerogels Hydrophobicity of the aerogels was investigated by conducting a water contact angle test on the aerogels A VCA Optima goniometer (AST Products Inc., USA) was used [28] J Cai, L Zhang, Unique gelation behavior of cellulose in NaOH/urea aqueous solution, BioMacromolecules 7(2006) 183-189 [29] W Zhang, Y Zhang, C Lu, Y Deng, Aerogels from crosslinked cellulose nano/microfibrils and their fast shape recovery property in water, Journal of Materials Chemistry, 22 (2012) 11642 [30] H Hamdan, M.N.M Muhid, S Endud, E Listiorini, Z Ramli, 29 Si MAS NMR, XRD and FESEM studies of rice husk silica for the synthesis of zeolites, Journal of NonCrystalline Solids, 211 (1997) 126-131 [31] M Poletto, H Júnior, A Zattera, Native Cellulose: Structure, Characterization and Thermal Properties, Materials, (2014) 6105-6119 [32] C.-M Popescu, G Singurel, M.-C Popescu, C Vasile, D.S Argyropoulos, S Willför, Vibrational spectroscopy and X-ray diffraction methods to establish the differences between hardwood and softwood, Carbohydrate polymers, 77 (2009) 851-857 [33] M Laufmann, Handbook of paper and board in: H Holik (Ed.), Wiley-VCH Verlag GmbH & Co KGaA2013, pp 109-143 [34] Z Hu, H Guo, M.P Srinivasan, N Yaming, A simple method for developing mesoporosity in activated carbon, Separation and Purification Technology, 31 (2003) 47-52 [35] J.B Condon, Surface area and porosity determinations by physisorption measurements and theory, Elsevier, Netherlands, 2006 [36] A Venkateswara Rao, M.M Kulkarni, D.P Amalnerkar, T Seth, Superhydrophobic silica aerogels based on methyltrimethoxysilane precursor, Journal of Non-Crystalline Solids, 330 (2003) 187-195 [37] J Shi, L Lu, W Guo, Y Sun, Y Cao, An environmental friendly thermal insulaiton material from cellulose and plasma modificaiton, J Appl Polym Sci., 130 (2013) 36523658 22 [38] S Sequeira, D.V Evtuguin, I Portugal, Preparation and properties of cellulose/silica hybrid composites, Polymer Composites, 30 (2009) 1275-1282 [39] S.B H Simmler, U Heinemann, H Schwab, K Kumaran, P Mukhopadhyaya, et al, Vaccum insulation panels: study on VIP-components and panels for service life prediction of VIP in building applications (subtask A), IEA/ECBCS, 2005 [40] M.C Kiran, A Nandanwar, M.V Naidu, K.C.V Rajulu, Effects of density on thermal conductivity of bamboo mat board, Int J Agric For , (2012) 257-261 [41] Z Huang, H.-s Li, H Miao, Y.-h Guo, L.-j Teng, Modified supercritical CO2 extraction of amine template from hexagonal mesoporous silica (HMS) materials: Effects of template identity and matrix Al/Si molar ratio, Chemical Engineering Research and Design, 92 (2014) 1371-1380 [42] N Jia, S.M Li, M.G Ma, J.F Zhu, R.C Sun, Synthesis and characterization of cellulose-silica composite fiber in ethanol/water mixed solvents, BioResources, (2011) 1186-1195 [43] S.D Bhagat, C.-S Oh, Y.-H Kim, Y.-S Ahn, J.-G Yeo, Methyltrimethoxysilane based monolithic silica aerogels via ambient pressure drying, Microporous and Mesoporous Materials, 100 (2007) 350-355 [44] S Motahari, H Javadi, A Motahari, Silica-aerogel cotton composites as sound absorber, Journal of Materials in Civil Engineering, 27 (2015) 04014237 [45] B.H John F T Conroy, Microscale Thermal Relaxation during Acoustic Propagation in Aerogel and Other Porous Media, Microscale Thermophysical Engineering, (1999) 199215 [46] M Garcia-Valles, G Avila, S Martinez, R Terradas, J.M Nogues, Acoustic barriers obtained from industrial wastes, Chemosphere, 72 (2008) 1098-1102 23 [47] K.W Oh, D.K Kim, S.H Kim, Ultra-porous flexible PET/Aerogel blanket for sound absorption and thermal insulation, Fibers and Polymers, 10 (2009) 731-737 24 Figure FE-SEM images of the silica–cellulose aerogels fabricated with the cellulose matrices with different cellulose fibre concentrations (a) 1.0 wt %, (b) 2.0 wt %, and (c) 4.0 wt % in the initial cellulose aqueous suspensions (d) is a typical image of the silica region of the silica–cellulose aerogels The image shows the silica nano-particles, which composes silica micro-particles shown in (a) – (c) Inside this image, cellulose fibres are not observed, due to the large dimensions of cellulose fibres, and of pores among cellulose fibres 25 Figure XRD patterns of the silica aerogel, the cellulose aerogel, and the silica–cellulose aerogels fabricated from cellulose matrices with different cellulose fibre concentrations (1.0, 2.0, and 4.0 wt %) inside the initial suspensions The X-ray diffraction patterns of the silica– cellulose aerogels can be a systematic superposition of those of pure cellulose aerogels and the pure silica aerogels 26 Figure The nitrogen adsorption/desorption isotherms of the silica aerogel and silica–cellulose aerogels fabricated from cellulose matrices with different cellulose fibre concentrations (1.0, 2.0, and 4.0 wt %) inside the initial suspensions P/P0 is the relative pressure 27 Figure The moderate linear relationship between the silica mass concentration and the BET surface area of the silica aerogel and the silica–cellulose aerogels 28 Figure A typical image of the water contact angle measurements of the silica–cellulose aerogels 29 Figure The thermal gravimetric analysis (TGA) curve of the silica–cellulose aerogel, compared with its cellulose matrix The silica–cellulose aerogels were fabricated from cellulose matrix with cellulose fibre concentrations of 1, and wt % in the initial suspensions 30 Figure describes the set-up of the measurements of sound absorption coefficients 31 Figure The compressive strain–stress curves of the different cellulose matrices and silica–cellulose aerogels fabricated from the cellulose matrices with different cellulose fibre concentrations (1.0, 2.0, and 4.0 wt %) in the initial suspensions The inset shows the compressive curves at the low strain (up to 5%) of various aerogels 32 Table The thermal conductivities of the silica–cellulose aerogels and their cellulose aerogel matrices Cellulose fibre concentration in the initial suspensions for cellulose matrix fabrication (wt %) 1.0 2.0 4.0 Density of composite (g/cm3) Thermal conductivity of composite (W/mK) Density of cellulose matrix (g/cm3) Thermal conductivity of cellulose matrices (W/mK) 0.149±0.005 0.146±0.005 0.138±0.002 0.041±0.003 0.039±0.002 0.039±0.003 0.039±0.005 0.047±0.004 0.059±0.003 0.034±0.003 0.035±0.006 0.037±0.003 33 Table The sound absorption coefficients of the silica–cellulose aerogels and their cellulose aerogel matrices, and the thickness of all the samples is kept at 10 mm Cellulose fibre concentration in the initial suspensions for cellulose matrix fabrication (wt %) Density of composite (g/cm3) Sound absorption coefficient of composite Density of cellulose matrix (g/cm3) 1.0 2.0 4.0 0.149±0.005 0.146±0.005 0.138±0.002 0.390±0.002 0.501±0.001 0.494±0.001 0.039±0.005 0.047±0.004 0.059±0.003 34 Sound absorption coefficient of cellulose matrix 0.399±0.001 0.389±0.003 0.303±0.001 Table The compressive Young’s modulus of the silica–cellulose aerogels and their cellulose aerogel matrices Cellulose fibre concentration in the initial suspensions for cellulose matrix fabrication (wt %) 1.0 2.0 4.0 Young’s modulus of composite (KPa) Young’s modulus of cellulose matrix (KPa) 86±3 104±3 169±5 13±1 21±1 39±2 35 Graphical Abstract 36 ... facile approach to fabricate cost-effective silica–cellulose aerogels with industrial dimensions Silica–cellulose hybrid aerogels for thermal and acoustic insulation applications Jingduo Feng1,... their thermal conductivities are relatively higher than those of silica aerogels [12, 16] On the other hand, both cellulose materials and silica aerogels are outstanding acoustic insulation materials... investigated The materials showed promising thermal and sound insulation properties for practical applications Experiments 2.1 Materials and chemicals Kymene 557H was supported by Ashland (Taiwan)