【作者】 傅华康；

【导师】 郑强； 杜淼；

【作者基本信息】 浙江大学 ， 高分子科学与工程， 2012， 博士

【摘要】 近几年,由一维型碳纳米管(carbon nanotubes,简称CNT)与二维型层状材料所构建的三维型复合填料开始成为研究的热点,这种新型复合填料汲取两种填料各自的优点,在改善CNT的分散性,以及制备力学性能、导电性能、阻燃性能与电化学性能等多功能型材料领域具有广阔的发展潜力。本文选用具有代表性的无机层状材料蒙脱土(montmorillonite,简称MMT)与层状双金属氢氧化物(layered double hydroxides,简称LDH),研究了MMT-CNT与LDH-CNT复合物的制备、生长机理与其在聚丙烯及聚乙烯醇中的应用。本文采用化学气相沉积(chemical vapor deposition,简称CVD)法在负载铁的MMT上原位生长CNT,成功制备出MMT-CNT复合物。考察了离子交换温度、前驱体制备方法及过渡金属种类等因素对离子交换过程及后期CNT生长的影响。结果表明,离子交换温度对MMT吸附Fe3+的过程影响显著。50℃下,MMT对Fe3+的吸附以离子交换吸附为主,100℃下,则以物理吸附为主：随[Fe3+]/[MMT]比值的增大,MMT对Fe3+的吸附量在100℃下迅速上升,而在50℃下则无明显变化。采用熔融共混方法,制备了MMT-CNT/聚丙烯(PP)复合材料,MMT-CNT的加入可在一定程度上提高PP的热稳定性、力学性能与导电性能。但由于MMT在经历了CVD处理后,层间即发生塌陷,严重限制了MMT-CNT在PP中的分散性,导致其改性效果不甚理想。为避免CVD法对层状材料所造成的破坏,本文采用条件温和的尿素法制备了微米级、形貌可控的Co-Al LDH-CNT复合物,研究了此复合物的生长过程及其影响因素、在不同溶剂中的剥离机理以及对PP多种性能的影响。结果表明,Co-Al LDH-CNT复合物的生长过程存在一个临界时间t*=16h,当t<t*时,主要是LDH成核与晶核生长阶段,而当t>t*,LDH的尺寸无明显变化,主要是晶体的完善过程；CNT含量(CCNT)变化对LDH的产率无显著影响,但对LDH的形貌、晶体完善程度以及LDH-CNT复合物的形貌影响较大。同时发现,存在一个临界浓度C*CNT=0.33mg/ml。当CCNT≤C*CNT时,LDH片层尺寸无明显变化,而当CCNT>C*CNT时,其片层尺寸显著减小。此外,可通过改变CCNT调控LDH-CNT复合物的形貌；在不同溶剂中,DBS分子链插层的LDH-CNT(DBS-LC)的剥离程度分别为：水>乙醇>二甲苯>DMF。采用溶液混合法,制备了DBS-LC/PP复合材料。发现DBS-LC的加入使PP的热稳定性、阻燃性能、力学性能及导电性能均显著提高,且比单一填料及MMT-CNT具有更高的效率为制备环保无毒的高性能LDH-CNT复合物,首先分别采用水热法与尿素法制备了高纯度、高结晶度的纳米级Mg-Al LDH与微米级Mg-Al LDH,并将其与聚乙烯醇(PVA)共混制备Mg-A1LDH/PVA薄膜。与微米级Mg-Al LDH相比较,纳米级Mg-Al LDH对PVA薄膜的力学强度与耐水性的改善效果更佳,且纳米级Mg-Al LDH/PVA薄膜的透明性与纯PVA薄膜相当。在此基础上,采用水热法制备了形貌可控的纳米级Mg-Al LDH-CNT,并对其在PVA中的应用进行了探索。结果表明,LDH与CNT的比值(δ)存在一个转折点δ*=5,当δ<δ*时,LDH-CNT复合物的平均粒径达到微米级,在水中稳定性差,当δ≥δ*时,LDH-CNT复合物的平均粒径随δ的增大而减小,其在水中的稳定性随δ的增加而提高；采用溶液混合法制备了LDH-CNT-A/PVA薄膜,发现LDH的存在有利于改善CNT与PVA之间的相容性。当δ=7时,复合薄膜的拉伸强度达最大值,当δ=18时,所得薄膜兼具优异的强度与韧性。更多还原

【Abstract】 Recent years, some researches found that the three-dimensional (3D) composite fillers consisting of one-dimensional carbon nanotubes (CNT) and layered materials could fuse the advantages of these two fillers and had the potential in preparing multi-functional composites with excellent mechanical, electrical, flame resistance and electrochemical properties, as well as in improving the dispersion of CNT in matrix. This work adopted montmorillonite (MMT) and layered double hydroxides (LDH) as the layered materials to prepare MMT-CNT and LDH-CNT composites, and studied the growth process、growth mechanism of these composites and their applications in polypropylene (PP) and poly (vinyl alcohol)(PVA).Firstly, the MMT-CNT composite was successfully prepared via chemical vapor deposition (CVD) method on Fe3+-MMT, and the influence of ion-exchange temperature、preparation method of Fe3+-MMT、type of transition metal on ion-exchange process and CNT growth were investigated. The results showed that the ion-exchange adsorption of Fe3+onto MMT dominated at50℃while the physical adsorption dominated at100℃; moreover, the amount of Fe3+adsorbed on MMT increased rapidly with the [Fe3+]/[MMT] ratio, whereas that at50℃did not exhibit significant changes. Subsequently. MMT-CNT/PP composite was prepared by melt mixing and the addition of MMT-CNT caused an increase of the thermal stability、mechanical property and electrical property for PP to some extent. However, due to the damage to MMT strucuture from CVD treatment, the dispersion of MMT-CNT was badly restricted, which should be responsible for the low efficiency of MMT-CNT in PP.To avoid the damage from the CVD treatment to layered materials, the microscale Co-Al LDH-CNT composite was successfully synthesized via a mild urea-hydrolysis method, and the growth process、growth mechanism and delamination behavior in various solvents of Co-Al LDH-CNT were investigated, as well as effect of this composite filler on PP performace. The results showed that a critical reaction time existed during the growth process of LDH-CNT composite, t*=16h, at t<t*, size of LDH increased gradually, while that changed little at t≥t*; besides, CNT concentration (CCNT) effected the crystal perfection degree of LDH and the morphology of LDH-CNT rather than the yield for LDH. There also existed a critical CNT concentration, C*CNT=0.33mg/ml, at CCNT≤C*CNT, size of LDH didn’t show significant changes, while that decreased gradually in the case of CCNT> C*CNT. In addition, the morphology of LDH/CNT could be controlled by adjusting CCNT; The delamination degree of DBS-LDH-CNT in various solvents ranked in the following order:water> ethanol> xylene> DMF. However, high-performance DBS-LC/PP composite was obtained via solution mixing, and the results showed that the introduction of DBS-LC leaded to a significant enhance of the thermal stability、flame resistance、mechanical and electrical properties for PP.Finally, the nanoscale Mg-Al LDH and microsacle Mg-Al LDH were synthesized via hydrothermal and urea-hydrolysis method respectively. Compared with microscale LDH, incorporation of nanoscale LDH could better enhance the mechanical property and water resistance of PVA film, and the nanoscale LDH/PVA films were highly transparent. Based on the above results, we prepared the controllable nanoscale Mg-Al LDH-CNT via hydrothermal method, and studied its application in PVA. The results showed that, a turning point existed in mlDH/mcNT ratio for LDH-CNT composite,δ*=5, at δ<δ*, size of LDH-CNT reached microscale, and LDH-CNT exhibited highly instable in water, while at δ≥δ*, size of LDH-CNT decreased and its stability in water improvesdwith increasing δ; moreover, existence of LDH could enhance the interaction between CNT and PVA, the LDH-CNT-A/PVA film had the best tensile strength at δ=7, and the film possessed excellent strength and toughness simultaneously at δ=18.更多还原