【作者】 徐寅；

【导师】 王家俊；

【作者基本信息】 浙江理工大学 ， 材料加工工程， 2011， 硕士

【摘要】 以天然可再生生物材料为原料,制备各种石油基塑料取代品越来越成为人们研究的重点。壳聚糖作为这类生物材料之一,无毒、可降解、具有良好的生物相容性、抑菌抗菌性,拥有广泛的应用前景。但是由于生物材料自身的一些不足,如机械性能差、耐水性能差等,其实际应用受到了一定的限制。可以通过各种改性方法提高相关性能,目前共混复合改性研究较多。本文选取高结晶性的纳米纤维素晶须为增强体,不仅能够有效地改善了壳聚糖的机械性能和耐水性,同时还能够保持壳聚糖材料可降解等特性。本文通过硫酸水解微晶纤维素制得纳米纤维素晶须,继而通过流延法制备纳米纤维素晶须/壳聚糖复合膜。通过扫描电镜、红外光谱和X射线衍射等测试分析了复合膜的截面形貌、分子基团及结晶情况,探讨了两者存在的分子间作用力。另外通过各种性能测试,分析复合膜的性能变化,探讨宏观性能与微观结构之间的关系。主要研究内容和结果如下:1.通过原子力显微镜观察和分析,纳米纤维素晶须的直径尺寸分布为5～20nm,长度尺寸分布为100～500nm,长径比为30左右;通过X射线衍射分析,酸水解处理部分破坏了纤维素的非晶区,结晶度由63%提高到了68%;通过红外光谱分析,纳米纤维素晶须基本维持了纤维素的骨架结构及纯度。2.复合膜截面电镜照片表明,纳米纤维素晶须在壳聚糖基体中具有良好的分散性;通过红外光谱分析两者分子基团的变化,表明复合膜中存在较强的静电力和氢键作用;通过X射线衍射分析,纳米纤维素晶须的加入使得壳聚糖在成膜时发生了结晶情况的变化。3.通过拉伸测试,分析了复合膜在干态下、湿态下以及增塑后,纳米纤维素晶须对复合膜的拉伸强度、拉伸模量及断裂伸长率的影响。纳米纤维素晶须的加入,使得干态下、湿态下、增塑后复合膜的拉伸强度分别由51.4MPa提高到80MPa、15.5MPa提高到25.1MPa、29.4 MPa提高到62.8MPa,同时复合膜的拉伸模量出现了线性增长,纳米纤维素晶须表现出良好的增强效应。另外,增塑剂聚乙二醇显著改善了膜的塑性,在断裂伸长率达到25%以上时,拉伸强度仍维持在较高的水平上。4.动态力学性能测试结果表明,采用纳米纤维素晶须增强的壳聚糖复合膜,储能模量出现了倍数的增长、玻璃化温度有所提高;吸湿性能测试结果表明,纳米纤维素晶须的加入使得壳聚糖膜的吸湿率明显降低,提高了耐水性;纳米纤维素晶须/壳聚糖复合膜对水蒸气的阻隔性能与热稳定性均明显提高、膜透光率维持在原先较高的水平上。更多还原

【Abstract】 There is a growing interest in making plastics that are based on natural renewable materials. As one of those, Chitosan(CS) has been found to be non-toxic, biodegradable, biocompatible and was reported by several researchers to have strong antimicrobial and antifungal activities. However, the use of CS has been limited because of its inherent poor mechanical and water-resistant properties. Polymer blending is one of the effective methods for providing CS for a variety of applications. In this paper, we choose highly crystalline cellulose particles called nanocellulose whiskers (NCW) as the reinforcement. NCW has advantages over other organic or inorganic fillers, not only due to improving drawbacks of CS, but also remaining its biodegradability and other good advantages.Firstly, NCW were isolated from microcrystalline cellulose (MCC) via acid hydrolysis, and then composite films were prepared via solution casting technique. Films were all characterized by SEM, FTIR, and XRD to determine their cross section surfaces, molecular groups and crystallizations in the following. A series of tests were performed at last for trying to find the relations between micro-structure and macro-properties. The main contents and conclusions of this paper were as follows:1. The diameter of NCW determined based on AFM was 5～20nm and the length was 100～500nm with aspect ratio about 30. XRD patterns of NCW indicated that the crystal integrity of cellulose had been maintained during the hydrolysis process. The degree of crystallinity of NCW increased from 63% to 68% showed that the hydrolysis occurred in the amorphous regions. FT-IR spectra also showed the molecule of NCW had all typical peaks of cellulosic structure.2. SEM images of cross sections exhibited a good dispersion at less percentage of NCW. The electrostatic and hydrogen bonds can be found to form a rigid reinforced cross-linking network through FT-IR. From the XRD patterns of composite films, the addition of NCW influences the crystallinity of CS when solution casting.3. Composite films under dry, wet and plasticized conditons were tested for their mechanical performance. With increasing NCW content, the tensile strength significantly increased from 51.4 to 80MPa, 15.5 to 25.1MPa and 29.4 to 62.8MPa respectively. Meanwhile, tensile modulus of films grew linearly. Polyethlene-glycol (PEG) 400 dramatically improved plasticity. The breaking elongation reached above 25%, while strength maintained at a highest level.4. DMA revealed multiple increasement on storage modulus in all temperature range and glass transition temperature shifted to higher. Water uptake decreased dramaticly at equilibrium in the presence of NCW which showed an improved water resistance. Besides NCW had helped to improve barrier and thermal properties of CS films, the composite films kept a high degree of transparency.更多还原