聚醚胺對蒙脫土之脫層機制及其衍生奈米複合材料之應用

Abstract

本研究使用具親水性乙醚與親油性聚丙醚鏈段之聚醚胺於質子性溶劑中改質蒙脫土。當在水中改質、及使用具高比率親油性聚丙醚的聚醚胺時，因其在親水性黏土層間的親油相聚集，能使蒙脫土的層間距擴大到 10 nm；當使用 5 當量的聚醚胺時，層狀黏土則會脫層至無序分散的狀態；反之，使用親水性聚乙醚比率較高的聚醚胺時，層間距只能擴大到 1.8 nm。但當在異丙醇中進行黏土改質，此兩類聚醚胺在 3 當量數下，皆能造成黏土的脫層，這是由於反應系統因熱力學安定的需求，會在黏土層外形成一個薄膜，再經由聚醚胺局部濃度的提升而最後滲透過薄膜進入黏土層間造成黏土脫層。 一般而言，使用傳統的化學改質法不易取得有機脫層黏土，而利用本研究中親水聚醚胺對黏土脫層的特殊機制，可以將特定的官能基，例如環三磷腈，導入聚醚胺後再對黏土脫層，來製備能改善通用塑材之熱安定性的有機脫層黏土。在本研究中，聚醚胺與環三磷腈由取代反應可合成分子級之聚醚胺環三磷腈，其結構為一個硬質的磷腈中心與具有彈性的聚醚鏈段所組成的外殼。將此聚醚胺環三磷腈酸化後對黏土進行脫層反應，可得到聚醚胺環三磷腈/脫層矽片之奈米衍生物。將此衍生物摻混入聚胺酯加工後，可以使其熱裂解溫度延緩 60 oC。使用不同摻混量的聚醚胺環三磷腈/脫層矽片組合對聚胺酯的熱安定以及抗紫外線 (365 至 400 nm 之波長) 性質有加成的效果。這可歸就於聚醚胺環三磷腈與脫層矽片在高分子材料中的分子級分散效果。

Poly(oxyalkylene)-amines (POA-amine) are used for affecting sodium montmorillonite (Na+-MMT) in protic mediums. In water, the hydrophobic aggregation of poly(oxypropylene)-rich (POP-) amines in the silicate galleries expands the interlayer spacing up to 10 nm and to exfoliation with over 5 amine equivalents, where as hydrophilic poly(oxyethylene)-rich (POE-) amines could only achieve in a low interlayer spacing of 1.8 nm. On the other hand, all POA-amines in isopropanol (IPA) afford the exfoliation with over 3 amine equivalents. The unexpected exfoliation is explained by the thermodynamic formations of an imaginary membrane surrounding the clay units, followed by amine diffusion from the solvent into the clay galleries. The POA-amine-modification of Na+-MMT in IPA opened a gateway to the preparation of randomized organoclays which in general were not easily achieved by conventional methods. This new finding allowed the exploration of new exfoliating agents embedding particular functionalities for special applications, such as hexachlorophosphazenes (HCP) for enhancing the thermal properties of common polymers. The amine substitution of HCP with POA monoamines (M-amine) afforded aminophosphazenes (AP) at molecular level. Na+-MMT was modified by using HCl-treated AP to prepare AP-exfoliated MMT clay (AP/EMMT) nanohybrids. When the nanohybrid was blended into polyurethane (PU), the presence of silicate platelets promoted the PU stability and retarded the degradation for more than 60 oC under the standard TGA measurement. The co-existence of AP and EMMT at various wt ratios demonstrated a synergistic effect on the improvements of thermal stability as well as the UV resistance under the standard test of UV exposure in wavelength range of 365 to 400 nm. The molecular-level dispersion of AP and silicate platelets had synergistically contributed to the PU thermal and UV stability.