Polymer nanocomposites dispersion characterization

The dynamic mechanical thermal analyzer (DMTA) is an important tool for studying the structure-property relationships in polymer nanocomposites. DMTA essentially probes the relaxations in polymers, thereby providing a method to understand the mechanical behavior and the molecular structure of these materials under various conditions of stress and temperature. The dynamics of polymer chain relaxation or molecular mobility of polymer main chains and side chains is one of the factors that determine the viscoelastic properties of polymeric macromolecules. The temperature dependence of molecular mobility is characterized by different transitions in which a certain mode of chain motion occurs. A reduction of the tan 8 peak height, a shift of the peak position to higher temperatures, an extra hump or peak in the tan 8 curve above the glass transition temperature (Tg), and a relatively high value of the storage modulus often are reported in support of the dispersion process of the layered silicate. 

A description of various characterization techniques for studying the dispersion of nanoparticles, curing kinetics and thermal degradation will facihtate the readers better understanding of these techniques. Information on the applications of polymer nanocomposites in various fields has also been incorporated. 

Solution intercalation—To prepare polymer nanocomposites, typically the organically modified LDH is dispersed in a solution containing polyolefin. The resultant dispersion is then stirred or aged under nitrogen atmosphere to accomplish the polyolefin intercalation. For example, Qu et al. [19,20] prepared and characterized polyethylene/ LDH by this method using dodecylsulfate (DS)-modified LDH (LDH-DS). The nanocomposites were obtained by refluxing the mixture of LDH-DS and fhe polyolefin solution in xylene. 

Wagberg L, Decher G, Norgren M et al (2008) The build up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes. Langmuir 24 784-795 Wan WK, Hutter JL, Millon LE et al (2006) Bacterial cellulose and it s nanocomposites for biomedical applications. In Oksman K, Sain M (eds) Cellulose nanocomposites. Processing characterization and properties. American Chemical Society, Washington, DC Wang B, Sain M (2007a) Dispersion of soybean stock-based nanofibre in a plastic matrix. Polym Int 56 538-546... 

Several studies on the characterization and fabrication of carbon nanotube-polymer nanocomposites have highlighted the important roles of the parameters discussed in Chapter 2 (such as, orientation, dispersion, and interfacial adhesion) in determining the properties of the composites. Jia et al. [75] used an in situ process for the fabrication of a PM M A/ M WNT composite. An initiator was used to open up the Jt bonds of the MWNTs in order to increase the linkage with the PMMA. The formation of C—C bonds results in a strong interface between the nanotubes and the PMMA. 

Composites with starch or cellulose, drugs, and highly disperse adsorbents can be used for medicinal purposes. These nanocomposites are characterized by enhanced activity of adsorbed biopolymers or polymers and/or drugs because of their transformation into a nanostate during interactions with solid nanoparticles because each adsorbate molecule interacts with nanoparticles. TSDC, DRS, DSC, FTIR, and other methods allow to study structural features of similar nanocomposites. NMR spectroscopy with layer-by-layer freezing-out of bulk and bound water as... 

Steigerwalt ES, Deluga GA, Lukehart CM. Pt-Ru/Carbon fiber nanocomposites synthesis, characterization, and performance as anode catalysts of direct methanol fuel cells. A search for exceptional performance. J Phys Chem B 2002 106 760-6. Matsumoto T, Komatsu T, Nakanoa H, Aral K, Nagashima Y, Yooa E, et al. Efficient usage of highly dispersed Pt on carbon nanotubes for electrode catalysts of polymer electrolyte fuel cells. Catal Today 2004 90 277-81. 

Nanocomposites are a relatively new class of hybrid materials characterized by an ultra fine dispersion of nanofillers into a polymeric matrix. As the result of this dispersion, these materials possess unique properties, behaving much diflferentiy than conventional composites or microcomposites, and offering new technological and economical opportunities. The first studies on nanocomposites were carried out in 1961, when Blumstein performed the polymerization of vinyl monomer intercalated into montmorillonite structure. Since then, clay-based polymer nanocomposites have emerged as a new class of materials and attracted considerable interest and investment in research and development worldwide (Schaefer and Justice 2007). 

Y. D. Zhu, G. C. Allen, J. M. Adams, D. Gittins, M. Herrero, P. Benito, and P. J. Heard, Dispersion characterization in layered double hydroxide/Nylon 66 nanocomposites using FIB imaging. Journal of Applied Polymer Science, 108 (2008), 4108-13. 

Consequently, it allows a quick and simple determination of the optimal exposure time to ultrasound. Obtaining the optimum debundling of the CNTs, while minimizing as much as possible damage caused by sonication, by reducing the exposure time, are crucial issues — the sine qua non conditions to produce technically interesting C NT/polymer nanocomposites, among others. I n the same order of ideas, UV-Vis spectroscopy can also be used to quantitatively characterize the colloidal stability in time of CNT dispersions. ... 

To sum up, UV-Vis spectroscopy appears to be a crucial and readily accessible tool for the characterization of surfactant-CNT dispersions, in terms of composition and optimization of preparation parameters, which can be further used to produce technologically interesting CNT/polymer nanocomposites, as will be shown in the following chapters of this book. 

Work by Lee et al. [14] provides a transition from discussions centered on polyethylene-montmorillonite nanocomposites to discussions focused on polypropylene-montmorillonite nanocomposites. An extruder was not employed to prepare the polymer nanocomposites. A Haake Banbury internal mixer prepared the polymer-montmorillonite concentrates (180°C, 10 min, and 50 r/min) and the final polymer composites. The montmorillonite in this study was Kunipia-F from Kunimine, Japan. Octadecylamine served as the organic modification for the montmorillonite. The polymer concentrates were prepared with polypropylene grafted with maleic anhydride (PP-g-MA Umex 1010 from Sanyo) and PE-g-MA (Umex 2000 from Sanyo). The PP-g-MA-organomont-morillonite concentrates demonstrated superior dispersion of the montmorillonite in relation to the PE-g-MA concentrates. Hence, most of the effort in preparing and characterization of the final polyethylene composites centered on the PP-g-MA-montmorillonite concentrates. The concentrations of montmorillonite in the concentrates were 12.5, 30,... 

Polymer/silicate nanocomposites are characterized by very strong reduction of gas and liquid permeability and at the same time the solvent uptake decreases accordingly. When single layers are dispersed in a polymer matrix the resulting nanocomposite is optically clear in the visible region, as clays are just 1 nm thick, whereas there is a loss of intensity in the UV region mostly due to scattering by the MMT particles. ... 

With respect to the clay particles, dispersion, polymer nanocomposites show extremely complex morphologies. As a consequence, detailed morphological studies results are difficult to obtain by means of electron microscopy and X-ray diffraction alone. The transport properties characterization can be quite successful in elucidating structural aspects at a level which may be insensitive to the other techniques. 

Gilman JW, Davis RD, BeUayer S et al. (2005) Use of optical probes and laser scanning con-focal fluorescence microscopy for high-throughput characterization of dispersion in polymer layered silicate nanocomposites. PMSE Prepr 92 168-169... 

Seong DG, Kang TJ, Youn JR (2005) Rheological characterization of polymer-based nanocomposites with different nanoscale dispersions. e-Polymers 5... 

Thermal and mechanical properties have been drastically improved by nanocomposites [12-33] dispersed with inorganic clays in a polymer matrix, which is characterized by nanometer lengthscale domains. These nanocomposite systems can be similarly examined by the methodology reported in this chapter. 

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