Preparation of Exfoliated Polyester/Clay Nanocomposites
Preparation of Exfoliated Polyester/Clay Nanocomposites
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DOI：
10.1002/adma.200401260
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发表时间：
2005-07
影响因子：
29.4
通讯作者：
T. Tsai;C. Li;C. Chang;W. Cheng;C. Hwang;R. Wu
中科院分区：
文献类型：
--
作者：
T. Tsai;C. Li;C. Chang;W. Cheng;C. Hwang;R. Wu
对聚合物/粘土纳米复合材料的研究普遍表明，与微米和宏观复合材料相比，几乎所有类型和类别的纳米复合材料都会带来新的和改进的性能，例如机械性能提高、吸湿性降低、可燃性和渗透性。[1±18]然而，关于剥离聚对苯二甲酸乙二醇酯（PET）/粘土纳米复合材料的制备和表征的研究很少报道。制备这些纳米复合材料的瓶颈是如何将整个聚合物基质中的粘土均匀地剥离成单独的层状硅酸盐。对于纳米复合材料的制备，已经表明亲水性或疏水性溶胀剂，例如长链有机阳离子和水溶性低聚物，可以插入或吸收在相邻的硅酸盐层之间。改性剂或表面活性剂不仅增加了层间距，而且增加了相容性，使得在聚合物基体聚合过程中聚合物链可以包含在硅酸盐层之间。然而，PET/粘土纳米复合材料无法通过这些传统方法剥离成单独的层，因为在聚合过程中没有提供促进相邻硅酸盐层之间单体或低聚物吸收的驱动力。相关研究强调粘土与聚酯界面之间的相容性[19, 20]，却忽视了单体扩散到层间进行聚合的因素。这种常规处理导致PET/粘土纳米复合材料仅变成粘土的插层分散体，而不是聚合物基底中的剥离分散体。为了克服上述问题，在本研究中，我们在粘土的画廊空间之间应用催化剂插层，并将其与新颖的聚合工艺相结合，将层状无机矿物材料按比例分散在聚酯中，从而形成剥离的PET/粘土纳米复合材料。本研究在实验部分描述的新颖聚合工艺之后应用催化剂前体乙酸锑Sb（OAc）3作为插层剂，将层状无机矿物材料按比例分散在聚酯中。 PET 并形成纳米复合材料。当纯化的粘土用乙酸锑[Sb(OAc) 3]处理时，对于命名为PK-802、PK-805和CWC的粘土，层间距分别从12.61、12.80和12.50扩大到16.05、16.17和15.22。 [21]由于天然粘土固有的不同晶体缺陷，不同的粘土源在改性时表现出不同的d-间距。通常，蒙脱石粘土含有连续的二维四面体片，其中四面体通过共享三个角而连接，并且剩余的角指向任何方向，其组成为T 2 O 5 。四面体片在单元结构中连接至八面体片以及配位阳离子组或单个阳离子。根据阳离子取代的位置，分为八面体取代蒙脱石或四面体取代蒙脱石。例如，蒙脱石是八面体取代的蒙皂石。 Mg2+可以取代八面体层中的Al3+，产生正电荷缺陷。这种缺陷可以通过层间的阳离子（通常是 Na+ 或 Ca2+）来补偿。正电荷不足越大，产生的阳离子交换容量（CEC）就越高。 PK-802、PK-805 和 CWC 的阳离子交换容量 (CEC) 分别为 116、98 和 140 mequiv/100…
Research into polymer/clay nanocomposites has generally shown that virtually all types and classes of nanocomposites lead to new and improved properties, such as increased mechanical properties, decreased moisture absorption, flammability, and permeability, when compared with their microand macrocomposite counterparts.[1±18] However, seldom have studies been reported on the preparation and characterization of exfoliated poly (ethylene terephthalate)(PET)/clay nanocomposites. The bottleneck in the preparation of these nanocomposites is how to exfoliate the clay uniformly throughout the polymer matrix into individually layered silicates. For the preparation of nanocomposites, it has been shown that hydrophilic or hydrophobic swelling agents, such as longchain organic cations and water-soluble oligomers, can be intercalated or absorbed between adjacent silicate layers. The modified agents or surfactants increase not only the interlayer spacing but also the compatibility, so that polymer chains can be included between the silicate layers during polymerization of the polymer matrix. However, PET/clay nanocomposites could not be exfoliated into individual layers by these traditional methods because there is no driving force provided that facilitates absorption of the monomers or oligomers between adjacent silicate layers during the polymerization process. Related studies emphasize the compatibility between the interfaces of clay and polyester,[19, 20] but overlook the factor of the monomer diffusing into the interlayer in order to proceed with polymerization. This conventional treatment causes the PET/clay nanocomposites to become only an intercalated dispersion of clay instead of an exfoliated dispersion in the polymer substrate. To overcome this above-mentioned problem, in this study we apply a catalyst intercalated between the gallery spaces of the clay, and combine it with a novel polymerization process to proportionally disperse the stratiform inorganic mineral materials in the polyester and thus form exfoliated PET/clay nanocomposites.This study applies the catalyst precursor antimony acetate Sb (OAc) 3 as an intercalant after a novel polymerization process, which is described in the experimental section, to disperse the stratiform inorganic mineral materials proportionally in the PET and form nanocomposites. When the purified clays are treated with antimony acetate [Sb (OAc) 3], the interlayer spaces are expanded from 12.61, 12.80, and 12.50 to 16.05, 16.17, and 15.22 for clays designated PK-802, PK-805 and CWC, respectively.[21] Different clay sources demonstrate different d-spacings upon modification because of the inherently different crystal defects of the natural clays. Generally, smectite clays contain continuous two-dimensional sheets of tetrahedrals, wherein the tetrahedrals are linked by sharing three corners and with the remaining corner pointing in any direction, with the composition T2O5. The tetrahedral sheets are linked in the unit structure to octahedral sheets and to groups of coordinated cations or individual cations. According to the location of the cation substitution, they are divided into octahedrally substituted smectites or tetrahedrally substituted smectites. For example, montmorillonite is an octahedrally substituted smectite. Mg2+ may substitute for Al3+ in the octahedral layer to produce a positive charge deficiency. This deficiency is compensated by cations, usually Na+ or Ca2+, residing between the layers. The greater the positive charge deficiency, the higher the cation exchange capacity (CEC) produced. The cation exchange capacities (CEC) of PK-802, PK-805, and CWC are 116, 98, and 140 mequiv per 100 …