Nanocomposites Based on Thermosetting Polyurethane Matrix and Chemically Modified Multiwalled Carbon Nanotubes

摘要

8.1 Introduction Carbon nanotubes (CNTs), which consist of cylindrical graphene layers, have attracted considerable attention because of their unique structure and excellent thermal, magnetic, electric and mechanical properties, in particular extremely high mechanical strength to density ratio and high chemical stability; this made them the outstanding candidates as nanofillers for polymers. It has been shown in numerous studies that incorporation of CNTs into polymer matrices may substantially modify their properties and lead to the nanocomposites with the enhanced performance [1, 2]. However, the final effect depends on the type of CNTs, whether as single-walled (SWCNTs), multiwalled (MWCNTs) and also spiral- and Y-shaped forms, as well as the physical and chemical state of their surface and the polymer mixing method utilised. In the direct mixing of pure CNTs into a host matrix, it is often difficult to separate agglomerated CNTs due to their intrinsic hydrophobic surface and to obtain a reasonable dispersion quality. Typically, the outer surface of CNTs contains a n-bond network that tends to promote CNT-CNT π-π interactions to minimise the surface energy. The agglomeration of CNTs reduces the interfacial area in the nanocomposites and may lead even to zero or negative impact on the properties of polymer matrices. Therefore, achieving a homogeneous dispersion of CNTs in a matrix (or at least decreasing the extent of CNT aggregation) is a key requirement for the realization of the desired enhancement in the final properties of nanocomposites. Additionally, enhancing interfacial interactions between the CNTs and the polymer matrix will promote efficient energy transfer within the system. To attain these aims, various methods have been used, in particular sonication at the mixing stage and also different approaches to chemical functionalization of CNT surface have been under investigation [1-5].