细菌纤维素纳米纤维稳定Pickering乳液的研究

发布时间：2018-03-21 18:39

本文选题：Pickering乳液　切入点：细菌纤维素　出处：《天津科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着纳米制备技术的发展,以固体颗粒乳化剂代替传统乳化剂来稳定乳液备受关注。本文选择环境友好的、生物来源的细菌纤维素(BC)及经TEMPO/NaBr/NaClO混合氧化体系氧化的细菌纤维素(TOBC)作为颗粒乳化剂,并从氧化程度、形貌、结晶度和晶胞尺寸等方面对TOBC进行表征。考察了纤维含量、氧化程度、静置时间等对BC或TOBC乳液的稳定性和粒径分布等的影响。通过宏观流变和微流变两种手段探究了TOBC氧化程度对纤维悬浮液和Pickering乳液流变性质的影响。TOBC的氧化程度随NaCl0用量的增加而增大。在氧化剂用量为2-10mmol/ g时,羧基含量的范围为0.58～1.15mmol/g。通过傅里叶红外光谱验证了羧基存在于纤维素分子链上。经TEMPO氧化后,纤维的宽度和长度较BC纤维明显下降。x射线衍射分析表明T EMPO氧化反应主要在纤维结晶区表面发生,对纤维的结晶度和品格参数没有明显影响。随氧化程度的增大,TOBC的Zeta电位绝对值和电荷密度均增大。经超声乳化制备的Pickering乳液,均为水包油型乳液。乳液的稳定性随纤维用量的增大而增强,随TOBC羧基含量的增大反而下降。乳液滴的粒径随纤维用量的增加而增大。通过扫描电镜观察聚苯乙烯小球表面纤维的分布,纤维均匀覆盖于乳液滴表面。乳液滴的Zeta电位绝对值和电荷密度均随TOBC氧化程度的增大而增大。宏观流变表明,随氧化程度的增大,6-TOBC(NaClO用量为6 mmol/g绝干纤维,下同)和10-TOBC悬浮液开始呈现出黏弹性质。所有的纤维悬浮液均表现出剪切稀释现象。在测试的剪切速率范围内,BC悬浮液的剪切黏度最大,2-TOBC、6-TOBC、 10-TOBC悬浮液的剪切黏度均较为接近。屈服应力值的趋势与剪切黏度一致。根据2-TOBC和6-TOBC稳定的Pickering乳液的宏观流变结果,二者均具有明显的黏弹性质,且2-TOBC乳液的黏弹性要高于6-TOBC乳液,呈现胶凝态。随静置时间的延长,乳液的G’均呈先减小后增大(不超过制备初期的G’)的规律。乳液的微流变参数,如均方位移、固液平衡值、弹性指数、宏观黏度因子均指明2-TOBC乳液的稳定性、乳液结构和黏弹性质最强,其次是6-TOBC乳液,l0-TOBC乳液稳定性最低,这些都与乳液宏观流变的分析结果一致。综上,本文制备了非常稳定的Pickering乳液,在室温下放置8个月没有明显变化。纤维的尺度和润湿性这两个相互抗衡的因素对乳液稳定性起着重要的作用。同时,乳液的黏弹性结构对乳液稳定性也非常重要。可通过调整纤维的用量和润湿性来控制乳液的流动状态和粒度。安全、无毒、绿色的TOBC在有望应用于食品、制药等领域。
[Abstract]:With the development of nanometer preparation technology, solid particle emulsifier instead of traditional emulsifier to stabilize emulsion has attracted much attention. Bioderived bacterial cellulose (BC) and bacterial cellulose (TOC) oxidized by TEMPO/NaBr/NaClO mixed oxidation system were used as granular emulsifiers. TOBC was characterized by oxidation degree, morphology, crystallinity and unit cell size. Degree of oxidation, Effects of static time on the stability and particle size distribution of BC or TOBC emulsions. The effects of TOBC oxidation degree on the rheological properties of fiber suspensions and Pickering emulsions were investigated by means of macro rheology and micro rheology. With the increase of the amount of NaCl0, when the amount of oxidant is 2-10mmol/ g, The range of carboxyl content is 0.58 ~ 1.15mmol / g. Fourier transform infrared spectroscopy (FTIR) shows that the carboxyl group exists on the molecular chain of cellulose. After TEMPO oxidation, Compared with BC fiber, the width and length of the fiber decreased obviously. X ray diffraction analysis showed that the oxidation reaction of T EMPO mainly took place on the surface of the crystalline region of the fiber. The absolute value of Zeta potential and charge density of TOBC increased with the increase of oxidation degree. The Pickering emulsion prepared by phacoemulsification was prepared by phacoemulsification. The stability of the emulsion increases with the increase of fiber content. With the increase of carboxyl content of TOBC, the particle size of emulsion droplets increases with the increase of fiber content. The distribution of fibers on the surface of polystyrene pellets is observed by scanning electron microscope. The absolute value of Zeta potential and the charge density of the emulsion droplets increase with the increase of the degree of oxidation of TOBC. The macroscopic rheology shows that the amount of NaClO is 6 mmol/g, and the content of NaClO is 6 mmol/g. All fiber suspensions show shear dilution. The shear viscosity of BC suspensions is maximum in the range of shear rate measured, and the shear viscosity of 10-TOBC suspensions is the same as that of 10-TOBC suspensions. The trend of yield stress is consistent with the shear viscosity. According to the macroscopic rheological results of 2-TOBC and 6-TOBC stabilized Pickering emulsion, Both of them have obvious viscoelastic properties, and the viscoelasticity of 2-TOBC emulsion is higher than that of 6-TOBC emulsion. The microrheological parameters of the emulsion, such as mean square displacement, solid-liquid equilibrium value, elastic index and macroscopic viscosity factor, all indicate the stability of 2-TOBC emulsion. The structure and viscoelastic properties of the emulsion are the strongest, followed by the lowest stability of the 6-TOBC emulsion l0-TOBC emulsion, which are consistent with the analysis results of the macroscopic rheology of the emulsion. In summary, a very stable Pickering emulsion has been prepared in this paper. At room temperature for 8 months, there is no significant change. The scale and wettability of the fibers play an important role in the stability of the emulsion. The viscoelastic structure of emulsion is also very important to the stability of emulsion. The flow state and particle size of emulsion can be controlled by adjusting the amount of fiber and wettability. The safe, non-toxic, green TOBC is expected to be used in food, pharmaceutical and other fields.
【学位授予单位】：天津科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ340.1;TB383.1

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