Study On Functionalized Carbon Nanotube Polymer Composites

Carbon nanotubes (CNTs) are promising reinforcement material for structural polymer composites due to their extraordinary mechanical and thermal properties. Mechanical properties of CNT/polymer composites depend mainly on the interfacial interactions between CNT and matrix, as well as the dispersion and alignment of CNTs in the matrix. However, pristine CNTs are prone to aggregation, and are insoluble in most solvents, rendering them difficult to be dispersed in the matrix. Moreover, the interfacial interactions between pristine CNT and matrix are rather weak. It was reported that CNT functionalization could be an effective way to improve the dispersion and strengthen the interfacial interactions. There exist three categories of functionalizations: nocovalent, covalent, and hybrid functionalizations. Recently CNT functionalizations and their applications in polymer composites have become a new research interest. The purpose of this thesis is to study the effects of different functionalizations on fracture lifetimes of CNTs, elastic moduli and tenslie toughness of different types of functionalized CNT/polymer composites.Based on a kinetic fracture model and using molecular mechanics (MM) simulations, the influence of different functionalizations on lifetime of single-walled carbon nanotubes (SWCNTs) under tension was studied. Three types of functionalizations, namely, covalent, noncovalent, and hybrid, were studied. Comparing with pristine SWCNTs, our results show that noncovalent functionalization can enhance, while covalent functionalization has detrimental effect, on the lifetime of SWCNTs, Effects from covalent and noncovalent functionalizations superimpose in hybrid functionalization, and in most cases it has positive effect on the lifetime of SWCNTs.Using molecular dynamics (MD) method, tensile toughness of noncovalent, covalent, and hybrid functionalized CNT/polymer composites were studied. Results show that noncovalent functionalization can not enhance the tensile toughness of composites, covalent functionalization and hybrid functionalization can markedly enhance the toughness of CNT/polymer composites.