Electrospun polymer/CNT composite

The need for mechanical reinforcement has been the driving force for most of the reported work on polymer/CNT composites. In an attempt to investigate the mechanical properties of electrospun PAN/SWNT nanofibers, Ko et al. (75) have used an atomic force microscope (AFM) to measure the elastic modulus of the electrospun composite nanofibers. The obtained fiber modulus was 140 GPa, a value which is much higher than that of conventional PAN fibers (60 GPa) (75). In a somewhat related but independent study, Mathew et al. (92) also used AFM to measure the mechanical properties of electrospun polybutylene/MWNT terephthalate nanofibers. Elastic deformation of MWNTs in electrospun PEO/MWNT and PVA/MWNT nanofibers was studied by Zhou and co-workers (84), and was found to increase with an increase in the modulus of the polymer matrix. In the same study, a simplified model was also proposed to estimate the elastic modulus ratio of MWNT and polymers. To confirm the validity of their model, these authors compared the model predictions with experimental data obtained from AFM measurements. 

The current review summarizes the recent progress made in electrospun CNT-polymer composite nanofiber, along with their processing, characterization, mechanical properties, and applications. Theoretical investigations on mechanical properties of CNT and CNT-based polymer composite are also addressed. Finally, research challenges and future trends in modeling and simulation of electrospun polymer composite nanofibers are discussed. 

The introduction of CNTs into electrospun polymer nanofibers is an interesting attempt to enhance the mechanical properties of electrospun CNT-pol5mier composite nanofibers. So far, a few reports have been found in the literature regarding measurement of the mechanical properties of single electrospun composite nanofiber. Isolation of individual composite nanofiber remains as the biggest challenge in measuring tensile properties... 

Electrospun carbon precursor fibers, based on polyacrylonitrile (PAN] and mesophase pitch, having diameters in the range from 100 nm to a few microns, were stabilized and carbonized. These carbon nanofibers had a very high aspect ratio. Nanopores were produced in CNFs made from PAN by a high-temperature reaction with water vapor carried in nitrogen gas by increasing the surface area per unit mass of carbon black. For conductive CNT/polymer composite fibers, CNTs were incorporated into poly(vinylidene fluoride) (PVDF) in iV,iV-dimethylformamide [DMF] solutions and electrospun to form CNT/PVDF fiber mats.The thinnest fiber was obtained as 7 0 nm in diameter. 

A DETAILED REVIEW ON PRODUCTION OE ELECTROSPUN CNT-POLYMER COMPOSITE NANOEIBERS... 

Carbon nanotubes (CNTs) are highly desirable materials possessing unique structural, mechanical, thermal, and electrical properties [25-30], Electrospun nanotube-polymer composite nanofibers are very attractive materials for a wide range of applications. This is due to the fact that the use of the electrospinning technique to incorporate CNTs in polymer nanofibers induces ahgnment of nanotubes within the nanofiber structure, which could greatly enhance the mechanical, electrical and thermal properties of composite fibers. " ... 

Numerous studies have focused on understanding and improving the structure and properties of the electrospun CNT-polymer composites [35-45], However, due to the difficulties encountered in experimental characterization of nanomaterial, the simulation and theoretical approaches play a significant role in understanding the properties and mechanical behavior of CNT-reinforced polymer nanofibers [46],... 

A number of reports on the electrospun composite fibers using various types of polymers and CNTs are listed in Table 23.3. Although CNTs have potential to be embedded into various polymer matrices, electrospinning of some polymers causes difficulties. 

There are two methods to study the morphological properties of electrospun CNT-polymer composite one is electron microscopy (EM) and the second one is atomic force microscopy (AFM). As mentioned earlier, the final morphologies of the electrospun CNT-polymer composite fibers can be affected by several characteristics of the initial solution such as solution concentration, CNT weight fraction, viscosity, surface tension and conductivity of solution in addition to some electrospiiming process (applied voltage, spinning distance, volume flow rate, and the strength of the applied electric field) and environmental conditions (temperature and humidity). 

The imiformity and stability of nanotube dispersion in polymer matrix are probably the most fundamental issue for the performance of composite materials. A good dispersion and distribution of CNTs in the polymer matrix minimizes the stress concentration centers and improves the uniformity of stress distribution in composites [80]. On the other hand, if the nanotubes are poorly dispersed within the pol mier matrix, the composite will fail because of the separation of the nanotube bundle rather than the failure of the nanotube itself, resulting in significantly reduced strength [117], Mazinani et al. studied the CNT dispersion for electrospun composite fiber, as well as its effect on the morphologies and properties of electrospun CNT-polystyrene nanocomposite [42]. They demonstrated that the CNT dispersion is an important controlling parameter for final fibers diameter and morphology. 

A detailed review on production of electrospun CNT-polymer composite nanofibers. 

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