CNF/CNC混合气凝胶的特性研究
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摘要
通过混合不同类型的纳米纤维素制备混合气凝胶,分析其性能特征。将桉木纸浆经化学预处理,结合机械研磨法制备得到纤维素纳米纤丝(cellulose nanofibril,CNF),桉木微晶纤维素(MCC)经硫酸水解法制备得到纤维素纳米晶体(cellulose nanocrystal,CNC),通过透射电镜与X射线衍射仪观测发现二者具有不同的长径比和结晶度。利用悬浮滴定、叔丁醇置换、冷冻干燥等方法制备球形CNF气凝胶和CNF/CNC混合气凝胶,采用扫描电镜、傅里叶红外光谱仪、比表面积分析仪、万能力学试验机对气凝胶的微观形貌、化学官能团、比表面积、平均孔径及压缩性能进行表征,结果表明:CNF气凝胶内部呈现三维网络结构,片状与纤丝状交织,比表面积为91.07m~2/g,平均孔径为14.81 nm,受压缩到80%应变时,压缩强度为0.125 MPa;添加不同比例的CNC制备CNF/CNC混合气凝胶,当CNC添加量为25%时,气凝胶内部纤丝结构取代片状结构,孔隙更加均匀,比表面积升至143.09m~2/g,压缩强度增至0.2 MPa,化学官能团和晶型结构未发生明显变化。当CNC添加量过大(50%)时,则会造成各项性能的减弱。
As a promising green nanomaterial,nanocellulose is of increasing interest for a range of applications relevant to many different fields,such as,electronic components,material science and biomedical engineering due to its advantages of anisotropic shape,excellent mechanical properties,good biocompatibility,tailorable surface chemistry,and interesting optical properties. In this study,mixed aerogels were prepared by mixing different types of nanocellulose and their performance characteristics were examined. The cellulose nanofiber( CNF) was prepared by chemical pretreatment combined with mechanical grinding method,while the cellulose nanocrystal( CNC) was fabricated using the sulfuric acid hydrolysis. According to the examinations of the transmission electron microscopy and X-ray diffractometer,it showed that the prepared CNC and CNF had different length-diameter ratio and crystallinity. The spherical CNF aerogel and CNF/CNC mixed aerogel were prepared using the suspension titration,tert-butyl alcohol replacement,and freeze-dry methods. The morphology,chemical functional groups,specific surface area,average pore size and compressive properties of the aerogels were characterized by the scanning electron microscopy,Fourier transform infrared spectroscopy,surface area analyzer and universal mechanical testing machine. The results showed that the three-dimensional network structure of the CNF aerogel interlaced with flake and filament; the specific surface area was 91.07 m2/g and the average pore size was 14.81 nm; the compressive strength was 0.125 MPa when it was compressed to 80% strain. The CNF/CNC mixed aerogel was prepared by adding different proportions of the CNC. Since the adding amount of the CNC was up to 25%,the internal fibrillar structure of aerogel replaced the lamellar structure,and the pores arranged more uniformly. The specific surface area was improved to 143.09 m2/g while the compression strength increased to 0.2 MPa. Moreover,the chemical functional groups and structure did not change significantly. It was also found that,once the amount of the CNC was over 50%,the performance of the mixed aerogel would be worsening.
As a promising green nanomaterial,nanocellulose is of increasing interest for a range of applications relevant to many different fields,such as,electronic components,material science and biomedical engineering due to its advantages of anisotropic shape,excellent mechanical properties,good biocompatibility,tailorable surface chemistry,and interesting optical properties. In this study,mixed aerogels were prepared by mixing different types of nanocellulose and their performance characteristics were examined. The cellulose nanofiber( CNF) was prepared by chemical pretreatment combined with mechanical grinding method,while the cellulose nanocrystal( CNC) was fabricated using the sulfuric acid hydrolysis. According to the examinations of the transmission electron microscopy and X-ray diffractometer,it showed that the prepared CNC and CNF had different length-diameter ratio and crystallinity. The spherical CNF aerogel and CNF/CNC mixed aerogel were prepared using the suspension titration,tert-butyl alcohol replacement,and freeze-dry methods. The morphology,chemical functional groups,specific surface area,average pore size and compressive properties of the aerogels were characterized by the scanning electron microscopy,Fourier transform infrared spectroscopy,surface area analyzer and universal mechanical testing machine. The results showed that the three-dimensional network structure of the CNF aerogel interlaced with flake and filament; the specific surface area was 91.07 m2/g and the average pore size was 14.81 nm; the compressive strength was 0.125 MPa when it was compressed to 80% strain. The CNF/CNC mixed aerogel was prepared by adding different proportions of the CNC. Since the adding amount of the CNC was up to 25%,the internal fibrillar structure of aerogel replaced the lamellar structure,and the pores arranged more uniformly. The specific surface area was improved to 143.09 m2/g while the compression strength increased to 0.2 MPa. Moreover,the chemical functional groups and structure did not change significantly. It was also found that,once the amount of the CNC was over 50%,the performance of the mixed aerogel would be worsening.
引文
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[18]WU Q,HENRIKSSON M,LIU X,et al.A high strength nanocomposite based on microcrystalline cellulose and polyurethane[J].Biomacromolecules,2007,8(12):3687-3692.
[19]CAPADONA J R,SHANMUGANATHAN K,TRITTSCHUH S,et al.Polymer nanocomposites with nanowhiskers isolated from microcrystalline cellulose[J].Biomacromolecules,2009,10(4):712.
[20]CHIEN H C,CHENG W Y,WANG Y H,et al.Ultrahigh specific capacitances for supercapacitors achieved by nickel cobaltite/carbon aerogel composites[J].Advanced Functional Materials,2012,22(23):5038-5043.
[21]JIAN L,YUN L,YANG D,et al.Lignocellulose aerogel from wood-ionic liquid solution(1-allyl-3-methylimidazolium chloride)under freezing and thawing conditions[J].Biomacromolecules,2011,12(5):1860.
[22]LU P,HSIEH Y L.Preparation and characterization of cellulose nanocrystals from rice straw[J].Carbohydrate Polymers,2012,87(1):564-573.
[23]PAAKKO M,VAPAAVUORI J,SILVENNOINEN R,et al.Long and entangled native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities[J].Soft Matter,2008,4(12):2492-2499.
[24]YANG X,CRANSTON E D.Chemically cross-linked cellulose nanocrystal aerogels with shape recovery and superabsorbent properties[J].Chemistry of Materials,2014,26(20):6016-6025.
[2]PAN M,ZHOU X,CHEN M.Cellulose nanowhiskers isolation and properties from acid hydrolysis combined with high pressure homogenization[J].Bio Resources,2013,8(1):933-943.
[3]李淑君.植物纤维水解技术[M].北京:化学工业出版社,2009.LI S J.Plant fiber hydrolysis technology[M].Beijing:Chemical Industry Press,2009.
[4]TAN C,FUNG B M,NEWMAN J K,et al.Organic aerogels with very high impact strength[J].Advanced Materials,2010,13(9):644-646.
[5]SEHAQUI H,ZHOU Q,BERGLUND L A.High-porosity aerogels of high specific surface area prepared from nanofibrillated cellulose(NFC)[J].Composites Science&Technology,2011,71(13):1593-1599.
[6]吴鹏,刘志明,刘昕昕,等.毛竹纳米纤丝化纤维素球形气凝胶的制备和表征[J].现代化工,2015,35(3):62-65.WU P,LIU Z M,LIU X X,et al.Preparation and characterization of nanofibrillated cellulose spherical aerogel from Phyllostachys heterocycla cv.pubescens[J].Modern Chemical Industry,2015,35(3):62-65.
[7]姚远,张洋,赵华,等.酸法制备纳米纤维素特性及其气凝胶的制备[J].纤维素科学与技术,2017,25(2):38-44.YAO Y,ZHANG Y,ZHAO H,et al.Characteristic of nanocrystalline cellulose prepared with acid method and fabrication of nano-cellulose aerogels[J].Journal of Cellulose Science and Technology,2017,25(2):38-44.
[8]张开涛,孙佩佩,商士斌,等.蔗渣浆制备纳米纤维素及其气凝胶的研究[J].生物质化学工程,2015,49(5):7-10.ZHANG K T,SUN P P,SHANG S B,et al.Preparation of nanocellulose and its aerogel from bagasse pulp[J].Biomass Chemical Engineering,2015,49(5):7-10.
[9]KAYA M.Super absorbent,light,and highly flame retardant cellulose‐based aerogel crosslinked with citric acid[J].Journal of Applied Polymer Science,2017,134(38):45315.
[10]LEE S,KANG K Y,JEONG MJ,et al.Evaluation of supercritical CO2,dried cellulose aerogels as nano-biomaterials[J].Journal of the Korean Physical Society,2017,71(8):483-486.
[11]JUNJI N,TSUGUYUKI S,AKIRA I.Simple freeze-drying procedure for producing nanocellulose aerogel-containing,high-performance air filters[J].Acs Applied Materials&Interfaces,2015,7(35):19809-19815.
[12]WANG X,ZHANG Y,JIANG H,et al.Tert-butyl alcohol used to fabricate nano-cellulose aerogels via freeze-drying technology[J].Materials Research Express,2017,4(6):065006.
[13]JIN C,HAN S,LI J,et al.Fabrication of cellulose-based aerogels from waste newspaper without any pretreatment and their use for absorbents[J].Carbohydrate Polymers,2015,123:150.
[14]李坚.木材波谱学[M].北京:科学出版社,2002.LI J.Wood spectroscopy[M].Beijing:Science Press,2002.
[15]ROMAN M,WINTER W T.Effect of sulfate groups from sulfuric acid hydrolysis on the thermal degradation behavior of bacterial cellulose[J].Biomacromolecules,2004,5(5):1671.
[16]SATYAMURTHY P,JAIN P,BALASUBRAMANYA R H,et al.Preparation and characterization of cellulose nanowhiskers from cotton fibres by controlled microbial hydrolysis[J].Carbohydrate Polymers,2011,83(1):122-129.
[17]GILBERTO S,JULIEN B,ALAIN D.Cellulose whiskers versus microfibrils:influence of the nature of the nanoparticle and its surface functionalization on the thermal and mechanical properties of nanocomposites[J].Biomacromolecules,2009,10(2):425-432.
[18]WU Q,HENRIKSSON M,LIU X,et al.A high strength nanocomposite based on microcrystalline cellulose and polyurethane[J].Biomacromolecules,2007,8(12):3687-3692.
[19]CAPADONA J R,SHANMUGANATHAN K,TRITTSCHUH S,et al.Polymer nanocomposites with nanowhiskers isolated from microcrystalline cellulose[J].Biomacromolecules,2009,10(4):712.
[20]CHIEN H C,CHENG W Y,WANG Y H,et al.Ultrahigh specific capacitances for supercapacitors achieved by nickel cobaltite/carbon aerogel composites[J].Advanced Functional Materials,2012,22(23):5038-5043.
[21]JIAN L,YUN L,YANG D,et al.Lignocellulose aerogel from wood-ionic liquid solution(1-allyl-3-methylimidazolium chloride)under freezing and thawing conditions[J].Biomacromolecules,2011,12(5):1860.
[22]LU P,HSIEH Y L.Preparation and characterization of cellulose nanocrystals from rice straw[J].Carbohydrate Polymers,2012,87(1):564-573.
[23]PAAKKO M,VAPAAVUORI J,SILVENNOINEN R,et al.Long and entangled native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities[J].Soft Matter,2008,4(12):2492-2499.
[24]YANG X,CRANSTON E D.Chemically cross-linked cellulose nanocrystal aerogels with shape recovery and superabsorbent properties[J].Chemistry of Materials,2014,26(20):6016-6025.
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