【作者】 张恒龙；

【导师】 余剑英；

【作者基本信息】 武汉理工大学 ， 复合材料学， 2011， 博士

【摘要】 沥青路面在服役过程中易产生车辙、裂缝、坑槽、剥落等病害,这些病害的产生严重影响了沥青路面的使用性能和服役年限。已有的研究表明,导致沥青路面产生病害的主要原因之一就是沥青的老化,即沥青路面在服役的过程中,受热、氧、光和水等环境因素的作用,沥青将发生热氧老化和光氧老化。由此可见,采用合适的耐老化改性剂以改善沥青的耐老化性能,对于延长沥青路面的使用寿命具有重要的意义。聚合物/无机纳米复合材料具有的独特力学、热学、阻隔、光学、电磁学等性能,使得添加无机纳米材料已成为聚合物高性能化和功能化的重要手段。无机纳米材料主要包括层状硅酸盐(如蒙脱石Mt、蛭石、累托石REC等)和无机纳米粒子(如纳米SiO2、纳米TiO2、纳米ZnO等)。近些年来,沥青/Mt纳米复合材料已受到国内外的广泛关注,研究表明Mt对沥青的物理性能、流变性能和抗老化性能有良好的改善效果,并且有机插层改性Mt的作用更为明显。而目前将其他无机纳米材料用于沥青改性的研究较少。系统研究不同无机纳米材料对沥青的改性作用以及二者的相互作用机理,对于改善沥青的耐老化性能、拓宽沥青改性剂的种类和推动纳米技术在道路材料中的应用具有重要意义。本文选用不同结构类型的插层剂对层状硅酸盐进行插层改性和采用硅烷偶联剂对无机纳米粒子进行表面修饰,制备了不同组成和结构的无机纳米材料；研究了插层改性和表面修饰前后不同无机纳米材料对沥青物理、热氧和光氧老化性能的影响；采用X-射线衍射(XRD)、傅里叶红外光谱(FTIR)和原子力显微镜(AFM)等测试手段对老化前后不同沥青/无机纳米复合材料的化学结构和微观结构进行了表征,探讨了无机纳米材料对沥青的改性机理以及沥青/无机纳米复合材料的耐老化机理。主要研究结论如下：(1)十六烷基三甲基溴化铵(CTAB)和十八烷基二甲基苄基氯化铵(ODBA)均可增大Mt、REC和膨胀蛭石(EVMt)的层间距。与Mt和REC相比,EVMt层间更易撑开,层间距同比增大了1.69nm～3.16nm。插层剂在三种层状硅酸盐的层间排布形式各异,主要表现为：倾斜单层、直立或倾斜双层。有机化改性过程中,层状硅酸盐中有机物含量在很大程度上取决于其阳离子交换容量的大小。(2)将沥青／层状硅酸盐纳米复合材料溶于三氯乙烯中,对混合溶液进行过滤,分离出其中的层状硅酸盐,然后进行XRD测试,将此测试结果与沥青/层状硅酸盐纳米复合材料本身的XRD测试数据相结合能更准确的反映不同沥青/层状硅酸盐纳米复合材料的结构特征,避免了仅对复合材料采用XRD测试过程中误差掩盖的真实结构信息。结果表明,Mt和EVMt与沥青复合之后形成的是相分离型的复合结构,ODBA-Mt、REC和ODBA-REC与沥青复合之后形成的是插层型的纳米复合结构,而ODBA-EVMt与沥青形成的则是半剥离型的纳米复合结构。(3)有机化插层改性显著增强了Mt和REC与沥青的相容性,离析管上下两部分的软化点差值和层状硅酸盐含量差别均明显减小,但其对EVMt与沥青的相容性无明显改善作用。相比于空白样,不同沥青/层状硅酸盐纳米复合材料物理性能的变化趋势均表现为软化点和粘度增大,而针入度和10℃延度变化差别较大。与REC和EVMt相比,Mt加入后沥青的软化点和粘度增加更大,并且Mt的加入提高了沥青的10℃延度,经过有机化改性,这种作用更为明显,而REC和EVMt插层改性前后对沥青的10℃延度影响较小。(4) Mt、REC和EVMt三种层状硅酸盐的加入均可降低沥青薄膜烘箱老化(TFOT)和压力老化箱(PAV)老化之后的粘度老化指数和软化点增量,提高沥青的延度保留率。相比于REC和Mt,沥青/EVMt复合材料在TFOT和PAV老化之后显示出更低的粘度老化指数、软化点增量和更高的延度保留率。EVMt的有机化改性使得沥青/EVMt纳米复合材料的耐热氧老化性能得到了进一步提高,但对其耐紫外老化性能无明显改善作用。插层剂的组成和结构对沥青/EVMt复合材料的耐老化性能影响较大,相比于CTAB-EVMt,沥青/ODBA-EVMt纳米复合材料在TFOT、PAV和长期热氧老化后显示出更低的质量变化率和粘度老化指数,这归因于ODBA-EVMt的加入显著抑制了沥青在热氧老化过程中羰基的生成,减缓了体系的胶体结构由溶胶-凝胶型向凝胶型转变而呈现单相化的趋势。(5)紫外老化之后,沥青/Mt复合材料较空白样显示出较低的粘度老化指数和软化点增量,而REC和EVMt的加入对沥青的紫外老化性能无明显改善作用。原子力显微镜观测表明,由于不同组分结构和刚性的差异,沥青呈现出以沥青质为核心的分散相和以轻组分为主的连续相。紫外老化过程中,沥青中的分散相表现出明显的缔合作用,使得沥青硬化,最终导致性能的劣化。而Mt的加入有效抑制了沥青紫外老化过程中分散相的缔合作用,减缓了沥青的硬化,显著改善了沥青的耐紫外老化性能。相比于Mt,沥青/ODBA-Mt纳米复合材料紫外老化之后体系中的两相结构更为明显,并且粘度老化指数和软化点增量也进一步降低,表现出更好的耐紫外老化性能。(6)红外光谱研究表明,硅烷偶联剂已通过化学键接到了三种无机纳米粒子的表面,不同无机纳米粒子表面偶联剂含量大小为：DB-560-nano-ZnO> DB-560-nano-SiO2>DB-560-nano-TiO2。无机纳米粒子的表面修饰显著增强了其与沥青的相容性,离析软化点差值和离析管中无机纳米粒子的含量差值明显减小。表面修饰对纳米ZnO与沥青的相容性及其在沥青中的分散性改善作用最为明显。无机纳米粒子的加入均可降低沥青的针入度和延度,提高沥青的粘度和软化点,但是表面修饰之后无机纳米粒子对沥青的这种作用有不同程度的降低,其中降低的程度以DB-560-nano-ZnO最为显著。(7)不同无机纳米粒子的加入均可以降低沥青紫外老化之后的粘度老化指数和软化点增量,其中以沥青/纳米ZnO复合材料的耐紫外老化性能最为明显。这归因于三种无机纳米粒子对紫外光屏蔽作用的差异,纳米SiO2主要以反射作用为主,而纳米TiO2和纳米ZnO则以吸收作用为主。与纳米TiO2相比,纳米ZnO对紫外光的吸收能力更强。由此可见,与对紫外线的反射相比,纳米粒子表现出的吸收作用对沥青耐紫外老化性能的改善更为有效。不同无机纳米粒子的表面修饰进一步增强了其对沥青紫外老化性能的改善作用,尤其以DB-550-nano-ZnO的作用最为明显。(8)表面修饰前后纳米ZnO均可有效抑制沥青的光氧化,相同紫外老化时间下,沥青/nano-ZnO和DB-550-nano-ZnO复合材料的羰基指数较空白样明显降低,但其抑制作用随着紫外老化时间的延长逐渐减弱。纳米ZnO的加入促进了沥青质在冷却过程中的异相成核结晶,改变了“蜂形”结构的尺寸及其在沥青中的分布状态。相比于未修饰纳米ZnO, DB-550-nano-ZnO的加入使得沥青质结晶体的直径明显减小,在体系中的分布也更为均匀,尺寸趋于均一。紫外老化过程中,纳米ZnO的加入有效地抑制了沥青表面粗糙度的增加和组分变化引起的体系单相化趋势,并且DB-550-nano-ZnO的作用更为显著,从而使得沥青/nano-ZnO和DB-550-nano-ZnO复合材料表现出较好的耐紫外老化性能。更多还原

【Abstract】 Asphalt pavement is prone to be destroyed by forming the rutting, cracks, pot holes and stripping during service process, which affects the service performance and service life of asphalt pavement obviously. Many studies have shown that bitumen aging is one of the principal factors causing the deterioration of bitumen pavements, that is, the thermo-oxidative and photo-oxidative aging of bitumen occur under the influence of heat, oxygen, light and water. Consequently, it is important to improve the aging resistance of bitumen by developing new anti-aging modifiers, which will prolong the service life of asphat pavement. Polymer/inorganic nanomaterials show the special mechanical, thermotic, barrier, optical and electromagnetic properties, which contributes to that the adding of inorganic nanomaterials is the important high performance modification and functionalization method to polymer. The inorganic nanomaterials mainly contain layered silicates (e.g. montmorillonite (Mt), vermiculite, rectorite (REC)) and nanoparticles (e.g. nano-SiO2, nano-TiO2, nano-ZnO). The key point of preparing polymer/inorganic nanomaterials is to improve the interface effect of inorganic nanomaterials and polymer, which can be achieved by organic modification of layered silicates and surface modification of nanoparticles. Recently, more and more attention of the domestic and international researchers has been paid to the bitumen/Mt nanocomposite. It has been showed that physical, rheological and aging resistance of bitumen can be improved obviously with the introduction of Mt. However, there are relative few reseacches about the adding of other nanomaterials into bitumen. The investigation of mechanism between the bitumen and inorganic nanomaterials is significant to improve the aging properties of bitumen, expand the bitumen modifiers and promote the application of nanotechnology in road materials.In this paper, inorganic nanomaterials with different composition and structure were prepared by modifying the layered silicates with intercalated agents and nanoparticles with silane coupling agents, respectively. The effect of inorganic nanomaterials on physical, thermo-oxidative and photo-oxidation aging properties was investigated before and after organic intercalation and surface modification. The chemical and microstructures of bitumen/inorganic nanocomposites before and after aging were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The modification and aging resistance mechanism of bitumen/inorganic nanocomposites also studied. The main results obtained are as follows:(1) The interlayer spacing of three layered silicates (Mt, REC and EVMt) can be increased by cetyltrimethyl ammonium bromide (CTAB) or octadecyl dimethyl benzyl ammonium chloride (ODBA). Compared with Mt and REC, the interlayer spacing of EVMt is easily expanded. The interlayer spacing of EVMt increases with the values between1.69and3.16nm in comparison with Mt and REC modified by the same intercalation agents. The intercalation agents show different aggregation structures in three layered silicates interlayers, for example, lateral-monolayer, vertical structure and lateral-bilayer. The intercalation agents content in layered silicates is mainly dependent on cation-exchange capacity.(2) The microstructures of bitumen/inorganic nanocomposites can be reflected more precisely by combining XRD and dissolving-filtrating method, which avoids the true structures hidden by test error during XRD analysis for bitumen/inorganic nanocomposites. The seperation process of layered silicates was performed as follows: first, bitumen/inorganic nanocomposites were dissolved in trichloroethylene and the layered silicates were filtered from the solution. Then the separated layered silicates were characterized by XRD. The results show that Bitumen/Mt and EVMt nanocomposites form the phase-seperated structure, bitumen/ODBA-Mt, REC and ODBA-REC nanocomposites form the intercalated structure, while the bitumen/ODBAEVMt nanocomposite forms the semi-exfoliated structure.(3) The compatibility between bitumen and Mt as well as REC is improved obviously by organic modification. Under the same content, the difference between the softening point as well as the layered silicates content in the upper and lower sections of the toothpaste tubes is decreased remarkably after organic modification. However, the compatibility between the EVMt and bitumen is not enhanced by organic modification. Compared with unmodified bitumen, the softening point and viscosity of bitumen/layered silicates nanocomposites are increased, while the penetration and ductility (10℃) are changed differently. The softening point and viscosity of bitumen are increased more obviously after Mt modification in comparison with REC and EVMt, moreover, the ductility (10℃) of bitumen is increased after Mt modification, which can be improved after organic modification of Mt. However, the ductility of bitumen is slightly influenced by REC and EVMT.(4) The viscosity aging index and softening point increment of bitumen are decreased, while the retained ductility are increased after thin film oven test (TFOT) and pressure aging vessel (PAV) aging with the adding of Mt, REC and EVMt. Compared with REC and Mt, bitumen/EVMt nanocomposite shows the lower viscosity aging index and softening point increment, and the higher retained ductility. The thermo-oxidative aging resistance of bitumen/EVMt nanocomposite is further improved after EVMt organic modification which shows slightly influence on its ultraviolet (UV) aging properties. The aging resistance of bitumen/EVMt nanocomposite is affected remarkably by the composition and structure of intercalation agents. Bitumen/ODBA-EVMt nanocomposite shows the lower viscosity aging index and mass change ratio in comparison with CTAB-EVMt after TFOT, PAV and long term aging, which can be attributed to that the formation of carbonyl in bitumen is restained as well as the transformation from sol-gel structure to gel structure during thermo-oxidative aging by ODBA-EVMt.(5) After ultraviolet (UV) aging, bitumen/Mt nanocomposite shows the lower viscosity aging index and softening point increment in comparison with unmodified bitumen, while the the UV aging properties of bitumen are slightly influenced by REC and EVMt. According to AFM analysis, bitumen shows the dispersed phase the core of which is asphaltenes and the matrix phase mainly contained light components due to the structure and stiffness diffference in various bitumen molecules. The association reactions of the dispersed phase as well as the hardening of bitumen occur during UV aging. However, the association reactions of the dispersed phase as well as the hardening of bitumen are prevented during UV aging by Mt. Furthermore, the two phases are still obvious in bitumen/ODBA-Mt nanocomposite, and the viscosity aging index and softening point increment are further decreased in comparison with Mt after UV aging, indicating its good UV aging resistance.(6) The silane coupling agents are bound on the surface of the three nanoparticles according to FTIR analysis and ablation tests. The silane coupling agents content in the three nanoparticles is as follows:DB-560-nano-ZnO> DB-560-nano-SiO2>DB-560-nano-TiO2. The compatibility between bitumen and nanoparticles is improved obviously by surface modification. Under the same content, the difference between the softening point as well as the nanoparticles content in the upper and lower sections of the toothpaste tubes is decreased remarkably after surface modification. Nano-ZnO shows the best compatibility with bitumen after surface modification among the three nanoparticles. The penetration and ductility are decreased, while the softening point and viscosity of bitumen are increased with the addition of nanoparticles. However, this effect is weakened after surface modification of nanoparticles and DB-560-nano-ZnO has the most influence.(7) The softening point increment and viscosity aging index of bitumen after UV aging are decreased with the addition of different nanoparticles. Bitumen/nano-ZnO nanocomposite shows the best UV aging resistance. It can be attributed to the different UV-shielding properties of the three nanoparticles. Nano-Si02has stronger reflection effect to ultra violet, while nano-TiO2and ZnO show the strong absorption effect. Compared with nano-TiO2, the absorption effect of ZnO is more obvious. Compared with reflection effect, the UV aging resistance of bitumen is improved more obviously by absorption effect of UV radiation. The UV aging resistance of bitumen/nanoparticle composites is further enhanced by surface modification of nanoparticles, and bitumen/DB-550-nano-ZnO composite shows the best UV aging resistance.(8) The photo-oxidation of bitumen can be prevented remarkably by nano-ZnO before and after its surface modification. The carbonyl indices of bitumen/nano-ZnO and DB-550-nano-ZnO composites are decreased more obviously in comparison with unmodified bitumen under the same UV aging time. However, this effect is weakened with the increasing of UV aging time. The heterogeneous nucleation crystallization of asphaltenes is accelerated by adding the nano-ZnO which also changes the "bee-like" structures as well as its dispersion in bitumen. Compared with unmodified nano-ZnO, the diameter of crystals is decreased obviously and its dispersion in bitumen is more homogeneous in bitumen by DB-550-nano-ZnO. The surface roughness increases and single phase trend caused by components changes in bitumen are prevented with the addition of nano-ZnO during UV aging, which is improved more obviously by DB-550-nano-ZnO, indicating the good UV aging resistance of bitumen/nano-ZnO and DB-550-nano-ZnO composites.更多还原