溶解纤维素-PVA复合凝胶的制备及其性能研究
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摘要
将微晶纤维素溶解于N-甲基吗啉-N-氧化物(NMMO)溶剂体系,并与聚乙烯醇(PVA)NMMO溶液混合,采用溶胶-凝胶工艺制备纤维素-PVA复合凝胶,探究不同凝固浴对复合凝胶性能的影响,并利用X射线衍射(XRD)、热重分析(TGA)、扫描电子显微镜(SEM)等表征手段考察了复合凝胶的晶体结构、热稳定性、微观结构等性能,讨论基于NMMO溶剂体系纤维素与PVA复合的成胶机理。结果表明,与分别以水及无水乙醇为凝固浴制得的复合凝胶相比,以20%NMMO/1%硼砂为凝固浴制得的复合凝胶无裂纹,且具有良好的韧性,机械性能最佳;经NMMO溶解后制得的纤维素凝胶由纤维素Ι型转变为纤维素Ⅱ型,而经1%硼砂交联后制得的纤维素-PVA复合凝胶在2θ=13.18°和19.46°处出现新的结晶峰,其为PVA的衍射峰,说明纤维素与PVA交联复合;热重分析显示,与纤维素凝胶相比,纤维素-PVA复合凝胶的热稳定性显著提高,热降解初始温度从270℃升高至280℃左右;利用SEM可观察到经硼砂交联后的纤维素-PVA复合凝胶的孔隙约500 nm,相对于纤维素凝胶,其孔隙结构更均匀紧凑。
The cellulose-PVA composite gels were prepared by sol-gel process via dissolving microcrystalline cellulose in NMMO solvent system and combining with PVA NMMO solution. The effect of various coagulation bath on gel properties was investigated for exploring the gelation mechanism. The crystal structure, thermostability and micro-morphology of the gel were investigated by XRD, TGA and SEM. Compared with water and ethanol coagulation bath, the cellulose-PVA composite gel regenerated by 20% NMMO/1% borax exhibited the best mechanical strength. The crystal structure of composite gel after dissolution-regeneration was transformed from cellulose I to cellulose II. After crosslinking of cellulose and PVA, the new peaks at 2θ=13.18° and 19.46° appeared in cellulose-PVA composite gel. The thermal degradation temperature of cellulose-PVA composite gel(280℃) was higher than cellulose gel(270℃), indicating that thermostability of composite gel was improved. From micromorphology of gel, the pore structure of composite gel regenerated by 20%NMMO/1% borax was more uniform than cellulose gel.
The cellulose-PVA composite gels were prepared by sol-gel process via dissolving microcrystalline cellulose in NMMO solvent system and combining with PVA NMMO solution. The effect of various coagulation bath on gel properties was investigated for exploring the gelation mechanism. The crystal structure, thermostability and micro-morphology of the gel were investigated by XRD, TGA and SEM. Compared with water and ethanol coagulation bath, the cellulose-PVA composite gel regenerated by 20% NMMO/1% borax exhibited the best mechanical strength. The crystal structure of composite gel after dissolution-regeneration was transformed from cellulose I to cellulose II. After crosslinking of cellulose and PVA, the new peaks at 2θ=13.18° and 19.46° appeared in cellulose-PVA composite gel. The thermal degradation temperature of cellulose-PVA composite gel(280℃) was higher than cellulose gel(270℃), indicating that thermostability of composite gel was improved. From micromorphology of gel, the pore structure of composite gel regenerated by 20%NMMO/1% borax was more uniform than cellulose gel.
引文
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[5] Wu J,Zhao N,Zhang X,et al.Cellulose/silver nanoparticles composite microspheres:eco-friendly synthesis and catalytic application[J].Cellulose,2012,19(4):1239.
[6] Oliveira W D,Glasser W G.Hydrogels from polysaccharides.I.Cellulose beads for chromatographic support[J].Journal of Applied Polymer Science,1996,60(1):63.
[7] Wang Z,Liu S,Matsumoto Y,et al.Cellulose gel and aerogel from LiCl/DMSO solution[J].Cellulose,2012,19(2):393.
[8] Kilpelainen I,Xie H,King A,et al.Dissolution of wood in ionic li-quids[J].Journal of Agricultural and Food Chemistry,2007,55(22):9142.
[9] Chen Q,Yang Y,Yang G S,et al.Effects of Ployvinyl Alcohol on the Structure and Properties of Lyocell Fiber[J].Journal of Cellulose Science and Technology,2013,21(4):43.陈钦,杨阳,杨革生,等.改性剂 PVA 对Lyocell纤维结构和性能的影响[J].纤维素科学与技术,2013,21(4):43.
[10] Zhu T R,Li Z M,Liu J Y,et al.Preparation of PVA,PVP and β-CD Modified Regenerated Cellulose Membrane and Pervaporation Separation of Caprolactam-Water Mixtures[J].Journal of Jianghan University (Natural Science Edition),2014,42(6):27.朱天容,李忠铭,刘继延,等.PVA、 PVP 和β-CD 改性再生纤维素膜的制备及渗透汽化分离己内酰胺水溶液[J].江汉大学学报 (自然科学版),2014,42(6):27.
[11] Zhang X,Zhu J,Liu X.Preparation andcharacterization of regenerated cellulose blend films containing high amount of poly(vinylalcohol)(PVA) in ionic liquid[J].Macromolecular Research,2012,20(7):703.
[12] Wu C L,Li X P,Qin S L,et al.Study on the Crystalline Structure of Cellulose Membranes Prepared by NMMO Method[J].Journal of Jiangnan University (Natural Science Edition),2006,5(3):352.吴翠玲,李新平,秦胜利,等.NMMO工艺纤维素膜结晶结构[J].江南大学学报(自然科学版),2006,5(3):352.
[13] Gonzalez J S,Luduena L N,Ponce A,et al.Poly(vinylalcohol)/cellulose nanowhiskersnanocompositehydrogelsfor potential wound dressings[J].Materials Science & Engineering C:Materials for Biological Applications,2014,34(1):54.
[14] Xiao M J,Zhang W,Lu C H.Preparation and Characterization of Poly(vinyl alcohol) /Cellulose Nanofibrils Thermoplastic Composites[J].Polymer Materials Science & Engineering,2017,33(4):121.肖梅杰,张伟,卢灿辉.聚乙烯醇/纤维素纳米纤热塑性复合材料的制备及表征[J].高分子材料科学与工程,2017,33(4):121.