Chapter 7 Chapter 7 Conclusions and Future Scopes
1.8 Characterizations and Structural Analysis of Composites
Evaluations of various characteristics of the polymeric composite materials are indispensible before application. The common characterization techniques such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction analysis,
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morphological analysis (SEM, FE-SEM, AFM) and many more tools are employed for polymer composite materials. However, the presence of filler materials into polymer give improved thermal, mechanical and other properties in accordance with the optimum percentage of filler materials.
For the structural applications, researchers give importance in mechanical properties, structural investigation of sandwich panels with bending deformation analysis as well as vibration analysis. In recent advancement of technology on structural analysis, researchers get more interest in investigation of effects of crack vibration for structural applications. This includes the crack identification and assessing the effect of crack on the mechanical parts.
The nanoparticles and nanocomposites can be characterized using various emerging technologies. Generally, characterizations of the materials are required to predict or to observe the intrinsic properties of the materials. Various techniques have been employed widely to characterize the nanocomposites materials. The commonly used powerful characterization tools are Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), wide-angle X-ray diffraction (WAXRD), Differential Scanning Calorimetry (DSC), Fourier Transformed Infrared Spectrophotometry (FTIR), Thermo Gravimetric Analysis (TGA) etc.
The SEM provides images by which huge information of surface features associated with the sample can be obtained. TEM allows a qualitative understanding of the internal structure, spatial distribution of the various phases, and views of the defective structure through direct visualization (Hussain and Hojjati, 2006).
WAXRD technique gives the information about the nanocomposite structures with the help of kinetics of polymer melt intercalation. Based on this, one can conclude the percentage aggregation of the nanoparticles into the polymer (Manchado et al., 2005; Raka et al., 2009).
Generally, a DSC technique is used widely to characterize the polymers for checking their composition, glass transition temperatures (Tg), melting temperatures (Tm) and crystallization percentage as well as crystallization temperature (Tc) and time (Zeng et al.,2006; Garcia et al., 2004; Jose et al.,2008). Zeng et al., (2006) has shown that double melting peaks can be observed in the curves of pure lab-synthesized polyamide (PA1010) and MWNTs/PA1010 composites with MWNTs contents < 5.0 wt%.
TGA is performed on samples to determine changes in weight in relation to the change in temperature (Zeng et al., 2006; Jose et al., 2008). Such analysis relies on a high degree of precision in three measurements i.e., weight, temperature, and temperature change. It is commonly employed in research and testing to determine characteristics of polymeric
Chapter 1 Introduction and Literature Review materials such as degradation temperatures, absorbed moisture content of materials, the level
of inorganic and organic components in materials, decomposition points of explosives, and solvent residues etc.
FTIR is used to record the infrared spectrum of a chemical substance or mixture of nanocomposite materials. This spectrometer gives data for all wavelengths simultaneously.
Choi et al., (2006) reported the observation on Multi-walled carbon nanotubes (MWNTs)/polysulfone (PSf) blend membranes. They concluded based on FTIR spectrum, the modified MWNTs show –COOH and –OH functional groups. The peak at 1715 and 3435 cm−1 are in correspondence to CO and –OH stretching, respectively, indicating the existence of carboxyl groups in the modified CNTs.
Chen et al., (2006) have obtained similar observations on Nylon 6 nanocomposites after extensive characterization. They discussed about the formation of MWNTs–NH2 and was confirmed through the FT-IR analysis. A fine dispersion of MWNTs throughout nylon 6 matrix was observed by SEM and TEM.
Valentini et al., (2003) reported on the characterization of SWNTs/polypropylene nanocomposites. They observed that the polymer is intercalated between nanotubes into bundles at the low frequency Raman bands when the concentration of nanotubes is low.
However, when the nanotube concentration is high, nanotubes do not allow for intercalation of a high quantity of polymer in between the nanotubes bundles.
Marosfoi et al., (2006) carried out thermogravimetric analysis (TGA) and varied temperature Raman spectroscopic measurements on the polypropylene/carbon nanotube composites. They reported that the incorporation of carbon nanotubes into polymer matrix increased the thermal stability compared to the virgin polypropylene. In addition, the TGA and Raman Spectroscopy also provide further information about the thermal decomposition of the composites.
Dong et al., (2008) also reported on polypropylene/organoclay nanocomposites after conducting experiments such as, the X-ray diffraction (XRD), SEM, TEM and dynamic mechanical analysis (DMA). The prevalence of intercalation with a certain level of localized exfoliation is observed by XRD, homogeneous dispersion is observed in the morphologies by SEM, TEM analysis. While quantitative verification by XRD and SEM analyses demonstrate the prevalent intercalated nanocomposites structure and higher clay content could deteriorate the uniform clay dispersion as a result of large tactoids. DMA analysis shows that the dynamic elastic modulus drastically decreases with the increase of temperature.
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Similar characterization techniques have been employed for characterizing the different nanocomposites by several researchers. Where, different characterization techniques such as, the UV/visible spectroscopy, Contact Angle Goniometer, XRD, Rheometer, DSC, Fourier Transform Infrared (FTIR) spectroscopy, SEM, Atomic Force Microscope (AFM), TGA, TEM, DMA etc. techniques revealed the intrinsic properties of the nanocomposites.