【作者】 戈明亮；

【导师】 贾德民；

【作者基本信息】 华南理工大学 ， 材料学， 2008， 博士

【摘要】 近年来聚合物/粘土纳米复合材料因表现出许多优异的性能已引起了人们的极大的兴趣。粘土具有纳米片层的结构,当它们以单个的片层均匀分散于聚合物基体中,或使聚合物分子链插入粘土层间,所得的纳米复合材料的性能可获得显著的提高,甚至出现许多新的性能。通过插层方法已经成功制备了许多聚合物/粘土纳米复合材料。为了增加粘土与聚合物之间的相容性,一般需要对粘土进行有机改性,使其由亲水变为亲油,最常用的插层改性剂是含长链烷基的季铵盐。当前大部分研究者对粘土的插层改性是在液相中(例如水、乙醇等)进行的,这种液相法存在许多缺点,例如工艺过程繁琐,耗时长,效率低,成本高,而且对环境造成一定的污染。本文采用固相法对粘土进行插层改性,制备出有机粘土。此法不采用水、乙醇等其他溶剂,而是在固态下直接对粘土进行改性,因此省去了后续的过滤、洗涤、干燥、粉碎、过筛等工艺过程,缩短工艺时间,提高改性效率,减少环境污染,降低成本,克服了液相法改性的缺点。用烷基季铵盐和季鏻盐插层剂对钠基蒙脱土进行有机化处理,使其成为有机蒙脱土。X-射线衍射(XRD)和傅立叶转换红外光谱(FTIR)表明插层剂已成功进入到粘土的层间,导致层间距扩大。将固相法改性的有机粘土应用于PP、PVC和NR, XRD和透射电镜(TEM)研究表明,PP、PVC和NR的大分子链可以插层到有机蒙脱土片层之中,形成了纳米复合材料。通过XRD, FTIR、差示扫描量热法(DSC)、热重分析(TGA)、TEM、橡胶加工分析仪(RPA)和动态力学分析(DMA)等现代测试手段以及力学性能测试研究了聚合物/粘土纳米复合材料的结构形态和性能。季铵盐改性的有机粘土B没有改变PP的晶型,而插层剂季鏻盐改性的有机粘土C使PP产生约10%左右的γ晶型。分别用修正Avrami方程的Jeziorny法、Ozawa法和Mo法研究PP/粘土复活材料的非等温结晶行为,结果表明,用Jeziorny法和Mo法处理非等温结晶过程比较理想,而用Ozawa法处理则不太适用。有机粘土的加入提高了聚丙烯的结晶温度和结晶速度,结晶指数n增加,对结晶常数Zc影响不大;有机粘土对PP的结晶具有异相成核的作用;钠基粘土导致结晶活化能增加,而有机粘土降低PP的结晶活化能。PP/粘土纳米复合材料的玻璃化转变温度高于纯PP。粘土的加入降低了PP的表观剪切粘度、动态粘度,改善了材料的加工性能,有机粘土降低的幅度大于钠基粘土;有机粘土的加入改善了聚丙烯的综合力学性能。此外有机粘土可以略为降低PP的最大热释放速率(pHRR)值。用KH-550处理过的有机粘土对PVC力学性能的提高幅度明显的大于用KH-560处理过的有机粘土。有机粘土C导致PVC的玻璃化转变温度略有升高,而偶联剂用量对PVC/粘土纳米复合材料的玻璃化转变温度没有明显影响。有机粘土C对PVC的热稳定性没有明显影响,偶联剂对PVC的热稳定性有一定的提高作用,降低了PVC的热分解速度,导致分解温度区间变大,但有机粘土C和偶联剂的加入降低了PVC的降解表观活化能。NR在和有机粘土混炼时,有部分的NR分子进入到粘土的层间,发生插层行为,而在硫化过程中,随着时间的延长,粘土的层间距不断增大,直至硫化结束,最终形成NR/粘土纳米复合材料。未改性的粘土对天然橡胶的硫化性能影响不明显,有机粘土可以明显缩短天然橡胶的焦烧时间和正硫化时间。不同的粘土对NR的粘性模量和损耗因子影响不大,但对弹性模量有一定的影响。有机粘土降低NR的热降解表观活化能,偶联剂的加入提高了NR的热降解表观活化能。有机粘土降低了NR的滚动阻力和抗湿滑性能;提高了NR的玻璃化转变温度;有机粘土改善了NR的综合力学性能,在大部分的情况下,含有偶联剂体系的静态力学性能好于不含偶联剂体系的静态力学性能;100℃、72h热老化后,有机粘土对NR的力学性能保持效果优于未改性的粘土。更多还原

【Abstract】 In recent years, polymer-clay nanocomposites have attracted great interests from researchers since they frequently exhibit unexpected hybrid properties synergistically derived from the two components. In most cases, the new and improved properties are derived when the dimensions of dispersion clay is less than 100nm and many techniques have been attempted for the ultrafine dispersion of clay into the polymer matrix. This is due, in great part, to the recent developments of new functionalization of smectic clays, especially Na+-montmorillonite. Nowadays many polymers have been used to prepare polymer/clay nanocomposites successfully. In general, polymer/clay nanocomposites were successfully prepared through intercalation. In most cases, in order to provide a better physical and chemical environment for the polymer, clay is organically modified through an ion exchange reaction between organic cations and inorganic cations to change the clay from hydrophilic to organophilic and to increases interlayer spacing of clay. The commonly used organic modification agents are long carbon-chain alkyl amine or ammonium salts. However, the processes of organically modified clay which mainly operate in the solvent (e.g. water or ethanol) are costly and inefficient. In addition, the processes cost much time and may bring environmental pollution on environment.In this paper, the organically modified clay (organoclay) was prepared by treating Na- montmorillonite with modified agent (alkyl ammonium ions and self-made surface-active cation) through solid state method without solvent. The Solid State Method has some advantages, such as simple process, cheap and harmless to environment. X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy indicated that modified agent could intercalate into the interlayer of the clay.The organoclay was applied to polypropylene(PP), poly (vinyl chloride)(PVC) and nature rubber(NR). The results from XRD and transmission electron microscopy(TEM) showed that the molecular chains of PP, PVC and NR had intercalated into the gallery of organoclay. The structure and properties of the polymer/organoclay nanocomposites were investigated by XRD, FTIR, diferential scanning calorimeter (DSC), thermogravimetric analysis (TGA), TEM, rubber processing analyzer (RPA), dynamic mechanical analyzer(DMA) and Mechanical properties testing.The organoclay which was modified by alkyl ammonium ions did not change the crystal structure of PP(α-PP). On the other hand, The organoclay which was modified by phosphonium cation did bring on theγcrystal structure of PP(10%).The nonisothermal crystalline process was described by the the modified theory of Avrami by Jeziorny, Ozawa and Mo methods. The results show that both Jeziorny and Mo methods could describe this system very well, but Ozawa analysis failed. The crystallization temperature of the composites was higher than that of the neat PP and crystallization speed of the composites was faster than that of the neat PP. Clay could increase the index of crystallization n of PP and had hardly effect on the constant of crystallization Zc of PP. The addition of organoclay decreased the activation energy of crystallization of the PP, which was used as nucleating agent during nonisothermal crystallization process of polymer. The thermal degradation temperature of PP increased evidently in the presence of the silicate layers. The organoclay could lead to depress apparent shear viscosity and improve processing properties. The mechanical properties of PP/organoclay nanocomposites were better than those of neat PP. In addition, organoclay could lightly lower peak heat release ratio(pHRR) of PP.Mechanical properties testing indicated that the PVC/organoclay nanocomposites were better than neat PVC. Silane coupling agent could lead reinforcement effect to PVC/organoclay nanocomposites and reinforcement effect of coupling agent KH-550 was much better than that of coupling agent KH-560. The glass transition temperatures(Tg) of PVC/organoclay nanocomposites were appreciably higher than that of neat PVC and silane coupling agent had hardly effect on the Tg. Silane coupling agent could increase the thermal degradation temperature of PVC and slower speed of thermal degradation of PVC. The addtion of organoclay decreased the activation energy of thermal degradation of PVC.Some of chains of NR could intercalate into interlayer of the organoclay when NR and organoclay were blended. During vulcanizing, The interlayer distance of the organoclay was expanded with increasing vulcanization time. Na- montmorillonite had hardly effect on the vulcanization properties of NR and the organoclay could obviously decrease vulcanization time of NR. The organoclay decreased the thermal degradation apparent activation energy of NR but silane coupling agent could increase the thermal degradation apparent activation energy of NR. The rolling resistance and anti wet-slide properties of NR/organoclay nanocomposites were lower than that of neat NR. In a general way, the addition of organoclay improved mechanical properties and silane coupling agent could lead reinforcement effect to NR/organoclay nanocomposites. After aging at 100℃for 72h, the mechanical properties of NR/organoclay keep better than those of NR.更多还原