雙性黏土矽片製備及環氧樹脂複材應用

Abstract

本研究經由系統化的合成，設計開發一新型雙親性奈米黏土，使用不同聚醚胺及環氧樹脂合成之脫層劑經由離子交換得到脫層型奈米黏土，再經由反向離子交換控制奈米材料之有機無機比例，進而達到雙親性。並利用其雙親性應用於分散顏料、吸附有機溶劑及導入環氧樹脂，製備成奈米複合材料。天然的蒙脫土經由開發之脫層劑的崁入，將層間距由 12Å 脫層為無序的奈米矽片，其基本結構中長寬高的尺寸為 100 × 100 × 1 nm，並藉由穿透式電子顯微鏡 (TEM) 及 X 光繞射儀 (XRD) 得到驗證。但也由於脫層劑使混成材料轉為疏水性及黏稠不易分散及利用，利用開發出之反向離子交換反應控制有機脫層劑/無機奈米黏土之比例，並找出最佳比例為 30/70 和 50/50 具有雙親性。此奈米混成材料在 1wt% 的添加可使表面張力由 72 mN/m 下降至 41 mN/m。 此外，添加在水和甲苯共溶液中可表現出穩定之乳化現象。另外在界達電位 (zeta potential) 和粒徑分析中可以勾勒出此雙親奈米矽片之雙親機制。在應用方面，幫助 pigment 顏料之分散和吸附 20 倍重量的癸烷，並利用共沉澱法合成氧化鐵於雙親奈米黏土中，利用磁力可以吸附水中之 pigment 顏料。另一方面，將此雙親奈米矽片作為添加劑在環氧樹脂材料中，製備出不同添加含量的奈米複合材料，並從性質改變的結果應證了雙親奈米矽片在高分子良好的分散性，例如添加 0.5wt%之雙親奈米矽片，即可將鉛筆硬度從 2H 到 4H，在穿透度的部分，未改質蒙脫土和雙親奈米矽片在同樣添加量時，雙親奈米矽片有明顯較佳之透明度。

A systematic approach of using poly(oxyalkylene)-amine-salt terminated 2,2-bis(4-hydroxyphenyl)propane. epoxy oligomers for modifying the layered silicate clays has led to organoclays with different surfactant properties. The pristine layered structure of natural clays such as sodium montmorillonite (Na+-MMT) could be organically intercalated into basal spacing from 12Å to 100Å and exfoliated to form randomized thin layer silicate platelets (ca. 1 nm thickness) , depending on the choices of the amine-oligomers. The organic modification of the ionic clays with cation exchanged capacity of 120 mequiv./100g involved the amine-salt ionic exchange reaction and accompanied by the organic incorporation into the clay layered structure as the first step. These organoclays were characterized by X-ray diffraction and shown their expanded basal spacing up to 100 Å and even into randomized platelets, and confirmed by TEM examination. Furthermore, we manipulated the organoclays fraction of hydrophobic amine-oligomers and hydrophilic randomized thin layer silicate platelets by reverse ion exchanged reaction as the second step. The cooperation of organic amine-oligomers and inorganic platelets has led to amphiphilic property in balanced organic fraction. The amphiphilic nature was further enhanced by their ability of lowering the surface tension at the water–air interface from 72 to 41 mN/m at 1 wt% of organoclay. The platelet ionic charges were analyzed by zeta potential measurement showing a pH-dependent charge species existed on the surface of the random platelets. The zeta potential of balanced organoclay was demonstrated charge reverse with pH changed, showing the interaction of nano silicate platelets and amine-oligomers can be evidenced. Since the amphiphilic organoclay synthesized, extremely stable emulsions form even the clay–amine suspension remains unflocculated in water/toluene biphase and assisted pigment dispersion. Moreover, amphiphilic organoclay with magnetic iron-oxide nanoparticles (FeNPs) embedded in the clay were synthesized by in situ Fe2+/Fe3+ coprecipitation. Then pigment adsorption with magnetic force in water was carried on. On the other side, as the filler, good enhancement of epoxy nanocomposites was carried, not only mechanical but also thermal property, raising pencil hardness from 2H to 4H with only 0.5 wt%. The high aspect-ratio and fine dispersion of the platelet silicates were found to be important factors in influencing the cured epoxy.