【作者】 张云升；

【导师】 胡国胜；

【作者基本信息】 中北大学 ， 军事化学与烟火技术， 2012， 博士

【摘要】 尼龙11（PA11）是一种具有优异综合性能的工程塑料，其突出性能主要是吸水率低和低温冲击强度高，广泛应用于汽车输油管道和煤气工程等方面，随着对低成本及高力学性能要求的日趋提高，单一的PA11树脂已不能完全满足各行业的需求。纳米粒子具有很多新的特性，利用它对高分子进行改性，可以得到具有特殊性能的高分子材料或使高分子材料的性能更加优异。所以，我们选择白炭黑、蒙脱土两种无机纳米材料作为填充材料，利用原位聚合反应制备PA11/白炭黑和尼龙611/蒙脱土纳米复合材料。论文第一部分以廉价的水玻璃为原料，采用硫酸液相沉淀法制备白炭黑。系统研究了制备过程中水玻璃浓度、反应温度、搅拌速度、H2S04浓度、分散剂Na2S04用量、溶剂洗涤等因素对白炭黑制各及性质的影响，优化制备方案，并对优化方案下的白炭黑的结构、粒径、表观物理性质进行了表征。然后以11-氨基十一酸和湿态白炭黑为主要原料，通过原位聚合的方法制备出了PA11/白炭黑纳米复合材料，采用扫描电子显微镜（SEM）、红外光谱仪（FTIR）、热失重分析仪(TGA)、毛细管流变仪、差示扫描量热仪（DSC）和偏光显微镜（POM）等对PA11/白炭黑纳米复合材料的形态结构、热稳定性、流变性能、结晶性能、力学性能和阻隔性能等方面进行了研究。取得的主要研究成果如下：1．在白炭黑纯溶液体系中加入表面活性剂PEG6000，控制其发生沉淀反应的微环境，使得生成的沉淀颗粒被包裹起来，保持颗粒的分散性，有效地降低了颗粒的团聚。PEG6000用量为2%时，产品一次粒径为20～45nm。2．采用“一步”法即在沉淀反应后期直接往溶液中加入硅烷偶联剂KH570，改变纳米白炭黑表面极性，使其由亲水性转变为疏水性，从而具有与非极性的基体材料更好的相容性。试验中发现在改性剂用量为2％、改性反应时间为1.5h、溶液pH值为4.76时，改性效果最好，此时产品的活化指数为100％，一次粒径为20～45nm。经XRD分析可以看出，加入PEG6000、KH570后对产品晶型没有影响，产品还是无定形的非晶体结构。FT-IR、TG等表征进一步表明表面活性剂PEG6000和硅烷偶联剂KH570是通过化学键键合到白炭黑表面，而不是简单的物理吸附；TEM电镜照片显示经PEG6000及KH570改性后，产品的团聚现象明显改善，改性效果明显。3．由油包水法制备的白炭黑粒径小且分布比较窄，在原位聚合过程中均匀分散于PA11基体中，并且与PA11间存在较强的相互作用；随着白炭黑含量的增加PA11的特性粘度逐渐减小，初始失重温度逐渐提高；白炭黑的加入有助于提高PA11纳米复合材料的拉伸强度和弯曲强度、热稳定性和阻隔性能，但降低了纳米复合材料的断裂伸长率和冲击强度。4．利用毛细管流变仪研究了尼龙11/白炭黑纳米复合材料的流变性能。研究表明PA11及其纳米复合材料均为假塑性流体，表现为切力变稀现象，且非牛顿指数随白炭黑含量的增加而增大；当剪切速率恒定时，除白炭黑含量为5wt%的纳米复合材料的表观粘度略高于纯尼龙11之外，其他纳米复合材料的表观粘度均低于纯尼龙11；PA11及其纳米复合材料的粘流活化能随剪切应力的增大而降低，说明在恒定剪切应力下其可在较宽的温度范围内加工、成型。5．采用DSC研究了尼龙11/白炭黑纳米复合材料的结晶过程及熔融行为。研究结果表明，白炭黑在纳米复合材料中起到了异相成核的作用，Avrami方程能很好的描述PA11及其纳米复合材料的等温结晶动力学过程，而经过Jeziorny修正过的Avrami方程及Mo法则能很好地描述非等温结晶动力学过程；利用Hoffman-Weeks公式和Hoffmann-Lauritzen理论求得了复合材料的平衡熔点和非等温过程的结晶活化能。论文第二部分以11-氨基十一酸、尼龙6预聚体和蒙脱土为原料，用原位聚合的方法制备出了尼龙611/MMT纳米复合材料，采用SEM、FTIR、TGA等并对其结构、特性粘度、形态、阻隔性能及热稳定性等方面进行了研究。主要研究成果如下：1.当蒙脱土含量较低时，复合材料形成了剥离结构，蒙脱土片层无规分散于聚合物基体中，而当蒙脱土含量较高时形成了插层结构。同时，研究还表明蒙脱土片层与尼龙分子链之间有较强的相互作用力。2.由于蒙脱土的限制作用，尼龙611/蒙脱土纳米复合材料粘均相对分子质量随着蒙脱土含量的增加逐渐下降。3.随着蒙脱土含量的增加，拉伸强度和断裂伸长率均呈现先增加后降低，而拉伸模量随着蒙脱土含量的增加而增大；尼龙611及其复合材料的冲击强度略有下降。5.蒙脱土的加入提高了材料的阻隔性能，较之于尼龙611，复合材料的吸水率、吸油值均随蒙脱土含量的增加大幅下降，分别下降了2倍和2.5倍；同时初始失重温度提高了10℃。更多还原

【Abstract】 Polyamide11(PA11) is an engineering plastics with excellent performance, suchas low water absorption and high low-temperature impact strength. PA11was mostlyused as automobile pipe-laying and municipal gas pipe as well as offshore oilfieldapplication.But with the increasing request of low cost and high mechanical properties,pure PA11resin can not fully satisfy various usages. Nanoparticles have a lot of newcharacteristics. Using nanotechnology in modification of polymers, nanocomposits with somespecial properties or polymers with more outstanding properties can be gained. Consequently,nylon11/silica nanocomposites, and nylon611/MMT nanocomposites were in-situpolymerized using silica and MMT as fillers.In the first part, silica was prepared via the vitriol precipitation method usingcheaper water glass as raw material．The influence of the reactant concentration(water glass, H2S04, Na2S04) and processing, parameters (reaction temperature,stirring rate, solvent washing reaction) on the morphology and properties of silicawere investigated systemically and optimized the synthesis technology．The structure,particle size and its distribution, and surface physical properties were alsocharacterized．PA11/silica nanocomposites (PSN-X, where X represent the weightpercentage of silica) were in-situ polymerized using11-amino undecanoic acid andwet silica as raw materials, and its morphology structure, thermal stability, rheologicalbehavior, crystallization properties, mechanical properties and barrier properties wereinvestigated by scanning electron microscopy (SEM), fourier-transform infraredspectroscopy (FTIR), thermo-gravimetric analyzer (TGA), capillary rheometer,differential scanning calorimeter (DSC) and polarizing microscopy (POM),respectively. The main results were listed as following:1. PEG6000was used as surfactant to control the minienvironment for the coprecipitation reaction，in which the formed precipitates were bundled by PEG6000and kept the precipitates from aggregating．The result showed that the average size ofprimary nanosilica particle was about20～45nm.2. Hydrophobic nanosilica was prepared by”one-step” precipitation method，thatis，silane coupling agent KH570was added into the reaction mixtures during the laststage of synthesis．The affinity of hydrophobic nanosilica with polymer matrix wasexpected to be improved．The activation coefficient of silica is100％，the averagesize of primary silica particle is about20-45nm. The XRD indicated that thenanosilica was still amorphous non-crystalline structure after the treatment withsurfactant PEG6000and silane coupling agent KH570．FTIR and TG analysisshowed that the surface active agents PEG6000and silane coupling agent KH570isgrafted to the surface of nanosilica by chemical bond rather than by simple physicaladsorption．TEM photographs illustrated that the aggregation of nanosilica wasimproved significantly after the treatment with surfactant PEG6000and silanecoupling agent KH570．3. Silica of small particle size and narrow distribution was prepared byoil-in-water microemulsion, and was uniformly dispersed in PA11matrix duringin-situ polymerization. Strong interaction was observed between PA11and silica.With the increasing silica content, the inherent viscosity gradually decreased and theinitial temperature of weight loss improved slightly. The addition of silica contributedto improve the tensile strength, flexural strength, thermal stability and barrier propertyof PA11, while it also led to reduce the impact strength and elongation at break.4. Rheological properties of PA11/silica nanocomposites were investigated bycapillary rheometry. The experimental results showed that both PA11and PA11/silicananocomposites were pseudoplastic fluid and exhibited shear-thinning behavior.Non-newtonian index increased with the silica content increasing. In case of aconstant shearing rate, apparent viscosity of all PA11/silica nanocomposites exceptPSN-5was lower than that of pure PA11. The reduction of the viscous activationenergy with the increasing shearing stress indicated that nanocomposites can beprocessed over a wide temperature at a constant shearing stress. 5. Crystallization and melting behavior of PA11and PA11/silicananocomposites were investigated by differential scanning calorimeter. It was foundthat silica acted as the nucleating agent of PA11, the Avrami equation was suitable todescribe the isothermal crystallization of PA11and its nanocomposites，while both theAvrami equation modified by Jeziorny and Mo’s method well described thenonisothermal crystallization kinetics. Additionally, the equilibrium meltingtemperature and the activation energy of nonisothermal crystallization fornanocomposites were calculated from Hoffman-Weeks equation andHoffmann-Lauritzen theory.In the second part, nylon611/MMT nanocomposites were in-situ polymerizedusing11-amino undecanoic acid, nylon6prepolymer and montmorillonite as rawmaterial. The structure, intrinsic viscosity, morphology, barrier properties, mechanicalproperties and thermal stability were characterized by scanning electron microscopy(SEM), fourier-transform infrared spectroscopy (FTIR),thermo-gravimetric analyzer(TGA),, respectively. The main results were listed as following:1. Organoclays were thoroughly exfoliated and dispersed homogenously in the nylon6/11matrix at low organoclay loading, but Intercalated and stacked silicates layerswere observed at high organoclay loading. It was also found that strong interactionoccurred between organocaly and nylon611chains.2. The viscosity-average molecular weight of nylon611/organoclay nanocompositeswas reduced with the increasing MMT content since that the organoclay blockades theactive ending-group of the monomers.3. The tensile strength and elongation at break was increased with the initial additionof MMT and then decreased with the further increasing MMT content. With theincreasing MMT loading level, the tensile modulus and impact strength werecontinuously increased and reduced, respectively.4. The barrir properties of nanocomposites were improved with the incorporation ofMMT, as indicated by the fact that the water absorption and oil absorption werereduced by twofold and2.5times versus pure nylon611. the onset temperature of weight loss was also increased by10℃.更多还原