Development of CNT-reinforced polymer composite

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Development of CNT-reinforced polymer composite

 

Author: Wong, Ka-keung
Title: Development of CNT-reinforced polymer composite
Degree: M.Phil.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Nanotubes.
Carbon.
Reinforced plastics.
Polymeric composites.
Department: Dept. of Mechanical Engineering
Pages: vi, 119 leaves : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2189820
URI: http://theses.lib.polyu.edu.hk/handle/200/53
Abstract: Light and strong material will be essential in everyday life in the future. Research into this kind of material has never stopped. In 1991, NEC researcher, lijima, discovered a tube-like structure of carbon: Carbon nanotubes (CNTs). Many reports showed that CNTs have novel mechanical, electrical, thermal and chemical properties. This tube-like structure was expected to improve human life. Fillers such as glass fiber, Kevlar, graphite, ceramics, metal particles and clays are commonly used in polymer composites. However, these fillers offer only a limited contribution to the mechanical properties of the composites. With the advance of nano-technology, more researchers have focused on the application of nano-materials such as nano-clays and CNTs to reinforce polymer-based composites. Although many studies have been conducted in the past few years on the possibility of using CNTs to improve the performance of polymer-based materials, some of the results have been contradictory and lacked coherence. Thus, an in-depth understanding of CNT-reinforced composites is required. It is now known that the dispersion of CNTs and interfacial bonding between CNTs and polymer chains affect the performance of reinforcements. Thus, these two key issues need to be solved in order to make the best use of CNTs as reinforcement. The Van der Waals force between the nanotubes is rather strong, so nanotubes usually form bundles and are difficult to separate. The dispersion quality of CNTs directly affects the stress transfer efficiency from a polymer matrix to CNTs. In addition, the smooth tube body makes it difficult to bond with the host matrix, which results in a poor interfacial strength between CNTs and polymer. This research project aims to solve the problems by functionalizing the CNTs (fCNTs) with carboxyl function group (COOH) to improve the stress transfer efficiency from polymer to CNTs body. These functional groups of CNTs provide sites for covalent integration of the CNTs into polymer structures to produce the reinforcement. Both thermosetting and thermoplastic polymers were used to fabricate CNTs polymer-based composites in this work. CNTs and fCNTs were blended with polypropylene (PP) and epoxy by different fabrication processes. The experimental results on both CNT/epoxy and CNT/PP composites were presented. fCNTs showed a positive effect on mechanical properties of the composites when comparing with non-functionalized ones. fCNTs formed cross-link with polymer chains. Thus, it can enhance the stress transfer efficiency between CNTs and polymer matrix. On the other hand, UV degradation has been a critical problem for polymers. There is a need to study the UV effects on CNTs polymer composites when applying them in outdoor environments. fCNT/PP composites were fabricated for UV irradiation. Through mechanical and thermal properties analyses, it has been found that fCNTs can diminish the negative effects of UV irradiation on PP. fCNTs absorbs the UV energy to form bonds with polymer chains, while the layer that the polymer chains formed bonding with fCNTs would be stronger. This strengthened layer can protect the inner part of the composite. From the experimental results, CNT-reinforced polymer composites showed its high potential for multi-purpose applications. If more effort is put into related research, it will become a useful material in the future.

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