纤维素多孔材料结构及性能的研究
发布时间：2019-02-16 21:30
【摘要】：纤维素从其储量、力学性能、化学性能、生物相容性可再生特性上都无疑是制备环境友好和生物相容性材料的最佳天然高分子原料。利用纤维素制备多孔材料是目前纤维素的一个研究方向。以纤维素为基体的纤维素多孔材料能够结合多孔材料的结构特征和纤维素分子优秀的理化性质、环境友好特性和生物相容性,具有广泛的应用范围和长远的应用前景。本文以N,N-二甲基乙酰胺(DMAc)为活化剂,研究了其对微晶纤维素的热活化机理,使微晶纤维素能在常温下溶解于LiCl/DMAc中。经过溶胶凝胶和溶剂置换得到具有紫外线吸收效果的透明纤维素水凝胶。以此水凝胶为前驱体,经超临界干燥和二氧化碳干燥制备了结构可控的纤维素多孔材料。并将所得多孔材料应用于掺杂石墨微粉(粒径d23μm)的PEG的封装得到纤维素多孔材料封装PEG的复合材料。通过X射线衍射(XRD)、傅里叶红外光谱(FTIR)、扫描电镜(SEM)观察和差示扫描量热(DSC)等对所制备的材料进行表征。并对DMAc热活化微晶纤维素机理,纤维素孔结构的控制和形成机理,以及孔结构对储热、导热性能、形状稳定性的影响进行了深入研究。研究表明:150℃加热条件下,DMAc造成微晶纤维素晶体缺陷增加,使得LiCl/DMAc溶解体系对纤维素溶解的可及性增加,使微晶纤维素在常温下就能溶解于LiCl/DMAc溶解体系。冷冻干燥前,预冷冻条件对纤维素多孔材料的孔结构起决定作用:预冷冻条件决定了纤维素水凝胶内冰晶的生长及其尺寸、形状、分布等,纤维素层片聚集于冰晶晶界上,冰晶升华后形成材料最终的孔结构。因此,通过控制冰晶的生长和结构可实现对纤维素多孔材料结构的控制,据此制备了具有取向结构的纤维素多孔材料。纤维素多孔材料封装PEG的复合材料的相变潜热可达到93.68J·g-1,热导率可达到3.09 W·K-1·m-1,具有作为相变储热材料应用的巨大潜力。复合材料中纤维素层片越多越密集,材料内部热传导热阻增加,导热性能下降,纤维素多孔材料的连通结构和取向结构有利于PEG填充,同时材料的导热性能也较好。在加热相变过程中,复合材料的相变潜热低于所含PEG结晶潜热总量,可能受到PEG和纤维素之间形成氢键的影响。通过本课题的研究工作完善了纤维素多孔材料的制备理论,探索了一种结构和性能可控的制备方法,拓展了纤维素多孔材料的应用范围。
[Abstract]:Cellulose is undoubtedly the best natural polymer material for the preparation of environment-friendly and biocompatible materials in terms of its reserves, mechanical properties, chemical properties and biocompatibility and renewable properties. The preparation of porous materials from cellulose is a research direction of cellulose at present. Cellulosic porous materials based on cellulose can combine the structural characteristics of porous materials with excellent physical and chemical properties of cellulose molecules, environment-friendly properties and biocompatibility, so it has a wide range of applications and long-term application prospects. In this paper, the thermal activation mechanism of N- dimethyl acetamide (DMAc) on microcrystalline cellulose has been studied. The microcrystalline cellulose can be dissolved in LiCl/DMAc at room temperature. Transparent cellulose hydrogel with UV absorption effect was obtained by sol-gel and solvent replacement. Cellulose porous materials with controllable structure were prepared by supercritical drying and carbon dioxide drying. The porous materials were used in the encapsulation of PEG doped with graphite powder (d23 渭 m) to obtain the composite material of PEG encapsulated by cellulose porous materials. The prepared materials were characterized by X-ray diffraction (XRD) (XRD), Fourier transform infrared spectroscopy (XRD),) (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The mechanism of thermal activation of microcrystalline cellulose by DMAc, the control and formation of cellulosic pore structure, and the effects of pore structure on heat storage, thermal conductivity and shape stability were also studied. The results show that under the heating temperature of 150 鈩，
本文编号：2424852
[Abstract]:Cellulose is undoubtedly the best natural polymer material for the preparation of environment-friendly and biocompatible materials in terms of its reserves, mechanical properties, chemical properties and biocompatibility and renewable properties. The preparation of porous materials from cellulose is a research direction of cellulose at present. Cellulosic porous materials based on cellulose can combine the structural characteristics of porous materials with excellent physical and chemical properties of cellulose molecules, environment-friendly properties and biocompatibility, so it has a wide range of applications and long-term application prospects. In this paper, the thermal activation mechanism of N- dimethyl acetamide (DMAc) on microcrystalline cellulose has been studied. The microcrystalline cellulose can be dissolved in LiCl/DMAc at room temperature. Transparent cellulose hydrogel with UV absorption effect was obtained by sol-gel and solvent replacement. Cellulose porous materials with controllable structure were prepared by supercritical drying and carbon dioxide drying. The porous materials were used in the encapsulation of PEG doped with graphite powder (d23 渭 m) to obtain the composite material of PEG encapsulated by cellulose porous materials. The prepared materials were characterized by X-ray diffraction (XRD) (XRD), Fourier transform infrared spectroscopy (XRD),) (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The mechanism of thermal activation of microcrystalline cellulose by DMAc, the control and formation of cellulosic pore structure, and the effects of pore structure on heat storage, thermal conductivity and shape stability were also studied. The results show that under the heating temperature of 150 鈩，
本文编号：2424852
本文链接：https://www.wllwen.com/kejilunwen/cailiaohuaxuelunwen/2424852.html
