黏土插層/脫層機制之策略性研究與黏土/磷難燃性奈米複合材料之應用

Abstract

本論文探討黏土插層/脫層機制形成“黏土/高分子混成材料”之策略性研究與黏土含磷之難燃性衍生奈米複合材料與應用，研究內容主要分敘如下。 黏土插層/脫層機制形成黏土/高分子混成材料之策略性研究，係藉由聚醚胺(polyoxyalkylene-amines) 插層劑之親/疏水性質與末端基差異性，探討對層狀黏土有機化改質機制之影響。研究中發現在相同分子量之線性疏水鏈段聚醚胺 (polyoxypropylene-amines, POP-amines)，一端末端基為甲基之 POP-M-amines，與雙端皆為胺基之 POP-D-amines 相比具有最大層間距擴張。由動態實驗發現，POP-M-amines進行黏土插層具有特殊之第二步插層現象，有別於一般插層劑經離子交換進入黏土層間(第一步插層)所觀察到有機量關鍵性插層 (critical intercalation)；第二步插層，黏土之層間距與插層劑量成正比。此階段式插層現象，除了可達到天然黏土脫層型態外，進一步地，可利用此特殊插層機制，將有機化黏土做為奈米容器，把材料儲存於黏土層間之奈米空間，如原油吸附與回收、藥物釋放及相變化 (PCM) 材料 (如paraffin wax) 之包覆等。 高分子/黏土 (Polymer layered silicate, PLS) 奈米複合材具有優秀的機械性質、熱穩定性質與生物相容性質。關鍵技術在於親水性之黏土與疏水性高分子間之相容性。本研究，黏土含磷之難燃性衍生奈米複合材料與應用，係以合成 Phosphazene-poly(oxypropylene)-amines (HCP-D400) 為始，並依三種改質方式製得 HCP-D400/NSP、HCP-D400/MMT及HCP-D400/Na+-MMT 有機化黏土，並具有 lower critical aggregate temperature (LCAT) 之特殊性質。經由SEM-EDX、XRD 及 TEM 分析，發現 HCP-D400 與脫層之奈米矽片(NSP) 以物理摻混方式製備之 HCP-D400/NSP 於環氧樹酯中分散效果最佳。更進一步分析複合材料之熱穩定性，當添加 10wt% HCP-D400/NSP 於環氧樹酯，T¬¬10wt% 由 350 oC 增加至 447 oC，T¬¬10wt% 由 500 oC 增加至757 oC ，有效提升環氧樹酯熱裂解溫度 127 oC (T10wt%)與 257 oC (T¬¬80wt%)。限氧指數 (limit oxygen index, LOI) 則提升 7% 至 27%。研究中發現HCP-D400不僅可使奈米矽片均勻分散於環氧樹酯中，進一步的與奈米矽片產生協同作用 (synergistic effect)，提升高分子材料之熱穩定性質。

Layered silicate clays are natural crystallites and are well recognized for their organic intercalation for nanocomposite applications. In this study, a new mechanism is revealed by selection of hydrophobic polyetheramines with a poly(oxypropylene) (POP) backbone and a methyl terminus as the intercalation agent. Specifically, the monoamine with a molecular weight of 2000 g/mol widened the basal spacing of the layered sodium montmorillonite up to 74 A and further expansion to 84 A, 96 A, and 100 A by a second intercalation different from the ionic exchange reaction. Kinetic studies indicated that the first stage of intercalation occurred after a critical concentration of a monoamine, while the second stage had no critical concentration behavior. This two-step method shows the potentials for synthesizing suitable organoclay nanostructures for encapsulating phase change materials (PCM) and oil recovery from the spilt ocean. The exploration of the in-depth understanding of clay confinement chemistry leads the strategic design of new materials and oil recovery process. We further synthesized the phosphazene-amine adduct of hexachlorocyclophosphazene (HCP) and poly(oxypropylene)-diamines of 400 g/mol molecular weight (D400) by amine/chloride substitution and triethylamine removal of HCl. Subsequently, the adduct HCP-D400 was physically mixed with exfoliated silicate platelets (SP) to prepare the HCP-D400/silicate hybrids (HCP-D400/SP). The HCP-D400/MMT (HCP-D400 intercalated Na+-MMT) and HCP-D400/Na+-MMT (HCP-D400 physically mixed with Na+-MMT) were also prepared for comparison with HCP-D400/SP. A more homogeneous silicate distribution HCP-D400/SP than the HCP-D400/MMT counterparts in epoxy nanocomposites was revealed by SEM-EDX, XRD, and TEM analyses. The epoxy nanocomposite with 10 wt% of HCP-D400/SP, HCP-D400/MMT, and HCP-D400 had a degradation temperature at 80 % weight loss (T80 wt%) of 757 oC, 712 oC, and 519 oC, respectively, in comparison with the 500 oC of the pristine epoxy system. Anti-flame test confirmed that the HCP-D400/SP epoxy nanocomposite had a higher limit oxygen index (LOI) of 27.0 % than the HCP-D400/MMT counterpart (24.0 %). The degree of exfoliating the layered clay into random silicate platelets is the predominant factor for the thermal stability enhancement. It is also demonstrated that the co-presence of phosphazene-amines and silicate platelets has a synergistic effect in improving the thermal behavior of the nanocomposites.