Different Types Of Multi-walled Carbon Nanotubes Research Articles

Multiwall carbon nanotubes filled polypropylene nanocomposites: Rheological and electrical properties

Two types of commercial multiwall carbon nanotubes (MWCNTs), Baytubes® C70P and C150P were incorporated into polypropylene (PP) using melt blending technique that employs a twin screw extruder (TSE) to prepare the nanocomposites of two different concentrations (1 and 3 wt%). Subsequently, American Society for Testing and Materials (ASTM) standard samples were prepared with an injection molding machine. The prepared nanocomposites were characterized by their rheological and electrical properties using a rheometer and a picoammeter/voltage source, respectively. The effect of different types of MWCNTs and loading percentage in rheological and electrical properties was investigated in detail. The rheological analysis demonstrated a considerable dependence of the melt rheological properties of the PP/MWCNTs nanocomposites on the MWCNTs loading. The storage modulus (G′), loss modulus (G″) and complex viscosity increased with increasing MWCNTs loading. In addition, type C70P exhibited superior rheological properties compared to C150P. In terms of electrical properties, the addition of MWCNTs in the PP matrix decreased the volume resistivity of the matrix in a manner, proportional to the MWCNTs loading. No significant difference in volume resistivity was observed between the MWCNTs types. POLYM. ENG. SCI., 54:1134–1143, 2014. © 2013 Society of Plastics Engineers

Dynamic Behavior of Nanocomposites Reinforced with Multi-Walled Carbon Nanotubes (MWCNTs).

The influence of multi-walled carbon nanotubes (MWCNT) on the structural dynamic behavior of MWCNT/epoxy nanocomposites was investigated. Two different types of MWCNTs, pristine MWCNT and functionalized MWCNT, were used in this study. Carboxylic acid-functionalized MWCNTs (MWCNT-COOH) were obtained by oxidation pristine MWCNTs via sonication in sulfuric-nitric acid and characterized by Fourier transform infrared spectroscopy (FTIR). Dynamic behaviors of the MWCNT reinforced nanocomposite including the natural frequency and damping ratio were determined using free vibration test. Experimental results showed that the damping ratio of the nanocomposite decreases with the increase of the MWCNT addition, while the natural frequency is increasing with the increase of the MWCNT addition. Functionalized MWCNTs improved the interfacial bonding between the nanotubes and epoxy resin resulting in the reduction of the interfacial energy dissipation ability and enhancement of the stiffness.

Preparation of conductive PTFE nanocomposite containing multiwalled carbon nanotube via latex heterocoagulation approach

Conductive poly(tetrafluoroethylene) (PTFE) composites containing surface-modified multiwalled carbon nanotubes (MWCNTs) were prepared by a simple heterocoagulation process in water. Two different types of MWCNT were used and compared: carboxylated MWCNT and cetyltrimethyl ammonium bromide (CTAB)-stabilized MWCNT. Aqueous PTFE dispersion was mixed with the well-dispersed MWCNT dispersions and they were heterocoagulated with the aid of a flocculant, polyaluminum chloride at an elevated temperature. After particle growth and successive stabilization step, particulated PTFE/MWCNT composites were prepared in the size range of 10–100 µm. The MWCNT-containing PTFE composites have improved thermal stability and electrical conductivity. Importantly, the percolation threshold for the electrical conductivity was achieved at a low concentration of MWCNT using this heterocoagulation process.

The colony formation assay as an indicator of carbon nanotube toxicity examined in three cell lines

The cytotoxicity of multiwall carbon nanotubes (MWCNT) was studied in three different cell lines; rat brain endothelial cells (RBE4), a rapidly dividing epithelial like human cell line originating from a cervix carcinoma (NHIK3025) and a human lung carcinoma cell line (A549). The colony formation assay was used as end point to avoid sample interference in colorimetric assays. It was possible to differentiate between four different types of MWCNTs in concentrations between 2 and 20 µg/ml with this method. There was a great difference in sensitivity between the three cell lines. RBE4 cells were best suited for this assay within this concentration range. The results show that the clonogenic assay has the potential to be a useful tool in the cytotoxicity testing of carbon based nanomaterials even at low concentrations provided a suitable cell line is used.

A novel aerosol method for single walled carbon nanotube synthesis

Single walled carbon nanotubes (CNTs) were produced by a novel aerosol method. Catalyst particles were formed by a hot wire generator and introduced into a laminar flow reactor. The size of catalyst particles was approximately 1–3 nm, while the diameter of formed CNTs was 0.6–2 nm. The average length of CNTs was about 50 nm. The important role of hydrogen in the process of CNTs growth was shown. The results of computational fluid dynamics (CFD) calculations to determine the temperature and velocity profiles, mixing conditions of the species in the reactor are presented. Different types of multiwalled CNTs were produced by a CVD method, in which the aerosol introduction of catalyst particles was used.