Advances in thermoplastic polyurethane composites reinforced with carbon nanotubes and carbon nanofibers: A review

Abstract

Carbon nanotubes (CNTs) have long been recognized as the stiffest and strongest man-made material known to date. Owing to high electrical conductivity, CNTs have also gained interest in the area of electrical appliances and communication related applications. Moreover, carbon nanofibers (CNFs) depict fine electrical and mechanical profile. Due to their miniscule size, excellent mechanical, electrical, and thermal properties, CNTs can only be beneficial if they are homogeneously dispersed and embedded into lightweight engineering polymer matrices. Adding small amounts of CNTs strongly improve the electrical, thermal, and mechanical properties of the composites. In order to enhance their chemical affinity to polymer matrices, chemically modifying the graphitic sidewalls and tips is necessary. This article reviews the processing technology and improvement of various properties of carbon nanotube-reinforced thermoplastic polyurethane (PU) composites. Initially, the structure, morphology, mechanical, thermal, and electrical properties of nanotubes are described. Then various strategies for fabricating PU/CNTs composites and their properties are discussed. To conclude, recent developments in the field of mechanical, thermal, and electrical properties of thermoplastic PU reinforced with nanotubes and nanofibers are reviewed.

Comparative Review on Structure, Properties, Fabrication Techniques, and Relevance of Polymer Nanocomposites Reinforced with Carbon Nanotube and Graphite Fillers

“…DMF was also used with polyester based PU in order to produce electrospun fibers filled with CNTs. Using electrospinning process, PU and PU/MWCNT nanocomposite nanofibers were also fabricated from PU and DMF solutions [19].…”

“…The difference between graphene and graphite is that graphene is one atom thick solitary layer of graphite whereas graphite basically consists of thousands of graphene layers. The most interesting factor of the graphene sheet is the hexagonal arrangement which is present in a repetitive manner in space and this is attributed to sp 2 hybridization process [19]. Major parameters which are used to describe the atomic structure of nanotubes are the chiral angle, tube chirality or helicity as material physico-mechanical characteristics are influenced by carbon nanotube chirality.…”

“…In the same manner, chirality also has effect on electronic properties. Graphite is considered as a semi-metal whereas nanotubes can be own characteristics that can be oppressed to be utilized in composite materials [19].…”

“…For the fabrication of polymer/nanotube composites, solution mixing has been the most commonly used method because of low solution viscosity accounted for the dispersion and mixing of nanotubes. In order to get metastable nanotube dispersion, the agitation can be obtained by mechanical stirring, magnetic shearing, reflux or sonication by using sonication bath [19]. One can also improve the nanofiller dispersion by using other ways such as heat or acid treatment of the functionalized nanotubes.…”

“…This technique of solution mixing may often result with well-dispersed polyurethane (PU) and CNTs. This method has been used to mix MWCNTs into commercially available PU with polyester and aromatic hard segment using tetrahydrofuran (THF) at a percolation threshold of 0.5 vol % [19]. Jung and coworkers…”