Functionalization of CNTs with isocyanate/carbodiimide into acylurea
| Autor: | Jui-Hung Kao, 高瑞鴻 |
|---|---|
| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 In this study, we have carried out three successful chemical modifications on the multi-walled carbon nanotubes (MW-CNT) by introducing different acylurea groups on to CNT’s carboxylic acids. After each chemical modification, the acylurea modified multi-walled carbon nanotubes were blended into either polyurea polymers or epoxy resins for making nano-CNTcomposites through thermal processes. Then, the properties of nanocomposites and un-modified polymers were compared to evaluate CNT’s potential enhancement effects. One of the biggest drawbacks of pristine MW-CNTs is their propensity to agglomerate, leading to inhomogeneous distribution when they are blended into polymer matrix. In our effort to remedy this problem, MW-CNT was first treated with nitric acid for introducing anchoring carboxylic groups on CNT surfaces. Then, the modified MW-CNTs were further reacted with either macrocyclic carbodiimide (MC-CDI), or linear polyamide carbodiimides such as polyamide carbodiimide (PA-CDI) or phenyisocyanate-MDI polycarbodiimide (PM-CDI) onto CNT’s carboxylic groups at 60℃~120℃. It was found that MC-CNT is the most efficient reagent among the three approaches. The acylurea functionalized CNTs prepared are the latent isocyanates which were found to generate reactive isocyanate groups on heating to over 180℃. The acylurea functionalized CNTs were dispersed readily in most organic solvents of polar and medium-polar solvents stable for as long as six months. In our composite application study, acylurea functionlized CNTs was blended into either a polyurea or an epoxy resin formulation at 0~4 wt%. On SEM examination, modified-CNTs are found to distribute homogenously throughout the polymer matrix which results in composite polymer thermal stability enhancement over un-modified polymers in Tg (in the epoxy resin) by 3~6℃ and in Tfl (in polyurea) by 14~25℃. In the mechanical evaluation, optimal enhacement in polyurea was observed at 2wt% CNT (MC-CDI modified) which result in 29% increase in tensile strength without sacrificing its elongation. Then, tensile strength increase 31% and 28% in epoxy resin with 4wt% MC-CNT-ACU and PA-CNT-ACU. The development of acylurea modified CNTs is still in its infancy, and there are many other applications that they could exert greater performance impact. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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