Polymer nanocomposites solution

FIGURE 3.21 Plots of shear viscosity versus time for (a) acrylic rubber (ACM)-silica and (b) epoxidized natural mbber (ENR)-silica hybrid nanocomposites in solution at different tetraethoxysilane (TEOS) concentrations, continuously for five days. The numbers in the legends indicate wt% TEOS concentration. (From Bandyopadhyay, A., De Sarkar, M., and Bhowmick, A.K., J. Polym. Sci., Part B Polym. Phys., 43, 2399, 2005. Courtesy of Wiley InterScience.)... 

C. Polymer-Clay Nanocomposites Synthesized from Polymer Solution... 

Polyimide-clay nanocomposites constitute another example of the synthesis of nanocomposite from polymer solution [70-76]. Polyimide-clay nanocomposite films were produced via polymerization of 4,4 -diaminodiphenyl ether and pyromellitic dianhydride in dimethylacetamide (DMAC) solvent, followed by mixing of the poly(amic acid) solution with organoclay dispersed in DMAC. Synthetic mica and MMT produced primarily exfoliated nanocomposites, while saponite and hectorite led to only monolayer intercalation in the clay galleries [71]. Dramatic improvements in barrier properties, thermal stability, and modulus were observed for these nanocomposites. Polyimide-clay nanocomposites containing only a small fraction of clay exhibited a several-fold reduction in the... 

Furthermore, CNT-clay hybrid filler can also be used to prepare polymer nanocomposites by solution based method. Hydrophilic... 

In solvent casting or solution mixing, CNTs are first dispersed in a suitable solvent and then mixed with a polymer solution to obtain a suspension of nanotubes in the polymer. The mix is then poured into suitable die molds and the solvent is allowed to evaporate to leave behind nanocomposite film. Solution based methods offer advantages of lower viscosities which facilitate uniform mixing and dispersion. Ultrasonication or magnetic stirring is typically used to separate and disperse CNTs uniformly in different solvents or... 

B. K. Bhowmick, A.K. Rubber-clay nanocomposite by solution blending. J. Appl. Polym. Sci. 2003, 87, 2216-2220. 

A limited number of methods have been developed for the preparation of metal-polymer nanocomposites. Usually, such techniques consist of highly specific approaches, which can be classified as in situ and ex situ methods. In the in situ methods, two steps are needed First, the monomer is polymerized in solution, with metal ions introduced before or after polymerization. Then metal ions in the polymer matrix are reduced chemically, thermally, or by UV irradiation. In the ex situ processes, the metal nanoparticles are chemically synthesized, and their surface is organically passivated. The derivatized nanoparticles are dispersed into a polymer solution or liquid monomer that is then polymerized. 

The modem methods of experimental and theoretical analysis of polymer materials stmcture and properties allow not only to confirm earlier propounded hypotheses, but also to obtain principally new results. Let us consider some important problems of partictrlate-filled polymer nanocomposites, the solution of which allows to advance substantially in these materials properties understanding and prediction. 

Georgy V. Kozlov, DSc, is a Senior Scientist at UNIID of Kabardino-Balkarian State University in Nal chik, Russian Federation. His scientific interests include the structural grounds of properties of polymeric materials of all classes and states physics of polymers, polymer solutions and melts, and composites and nanocomposites. He proposed to consider polymers as natural nanocomposites. He is the author of more than 1500 scientific publications, including 30 books, published in the Russia, Ukraine, Great Britain, Germany, Holland, and USA. 

A microemulsion polymerization method [62,63] was also reported to produce magnetic polypyrrole nanocomposites filled with 7-Fc203. The nanoparticles were dispersed in the oil phase. FeCla was used as an oxidizing agent. Sodium dodecylbenzenesulfonic acid (SDBA) and butanol were used as the surfactant and cosurfactant, respectively. FeCl3 (0.97 g) was dissolved in a mixture of 15 mol deionized water, SDBA (6 g), and butanol (1.6 ml). A specific amount of 7-Fc203 suspended nanoparticle solution was added to the above solution for dispersion. Pyrrole was added for nanocomposite polymer fabrication in the microemulsion system. The polymerization was continued for 24 hours and quenched by acetone. 

Jamieson, A. M., Simha, R., Newtonian viscosity of dilute, semi-dilute and concentrated polymer solutions. Chapter 1, in Polymer Physics From Suspensions to Nanocomposites and Beyond, Utracki L. A. and Jamieson A. M., Editors, J. Wiley Sons, New York (2010). 

Pillai et al. described a comparison between two chemical functionalization strategies for the amine functionalization of multiwalled CNTs. The modified CNTs with optimum amine content were used to prepare PLA/CNT nanocomposites through solution casting method. The polymer nanocomposite thus prepared showed improved thermal properties when compared to the neat PLA [65]. 

Electrospinning processes are used to prepare nanocomposite fiber mats. In order to prepare nanocomposite fiber mats, mixtures containing the polymer solution and cellulose whiskers solution are placed in the appropriated electrospinning setup. Peresin et al. [128] have produced nanocomposite mats of poly (vinyl alcohol) (PVA) reinforced with cellulose nanocrystals using this electrospinning technique. Smooth nonwoven mats with homogeneous nanofibers were obtained. Park et al. [129] have also incorporated cellulose whiskers into nanofibers of polyethylene oxide (PEO) by the electrospiiming process. 

The solution method, fillers are added to a polymer solution using solvents such as toluene, chloroform and acetonitrile to integrate the polymer and filler molecules (i ). Since the use of solvents is not environmentally-friendly, melt processing and in-situ polymerization are the most widely used methods of nanocomposite production. 

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