Nanoparticle-Reinforced Composites

Inorganic or organic nanoparticles have been incorporated to enhance the mechanical, barrier and thermal properties of PLA. Over the past few years, various nanomaterials have been investigated for reinforcing PLA, including layered silicates, carbon nanotube, hydroxyapaite, layered titanate, aluminum hydroxide, etc. 

Kim et al. studied the effect of bacterial cellulose on the transparency of PLA/bacterial nanocomposites, since bacterial cellulose had shown good potential as reinforcement or preparing optically transparent materials due to its structure, which consists of ribbon-shaped fibrils with diameters in the range from 10 to 50 nm. They found that light transmission of the PLA/bacterial cellulose nanocomposite was quite high due to the size effect of 

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Tsai, J.L., Hsiao, H., Cheng, Y.L., 2010. Investigating mechanical behaviours of silica nanoparticle reinforced composites. Journal of Composite Materials 44 (4), 505—524. 

B. Wetzel, F. Haupert, M. Z. Rong (2002) Nanoparticle-reinforced composites preparation, structure, properties, Proc. S Natl. Symp. SAMPE, Deutschland e.V., Kaiserslautern (in German). 

These are fields defined throughout space in the continuum theory. Thus, the total energy of the system is an integral of these quantities over the volume of the sample dt). The FEM has been incorporated in some commercial software packages and open source codes (e.g., ABAQUS, ANSYS, Palmyra, and OOF) and widely used to evaluate the mechanical properties of polymer composites. Some attempts have recently been made to apply the FEM to nanoparticle-reinforced polymer nanocomposites. In order to capture the multiscale material behaviors, efforts are also underway to combine the multiscale models spanning from molecular to macroscopic levels [51,52]. 

Vines, J.B., Lim, D.J., Anderson, J.M., Jun, H.W. Hydroxyapatite nanoparticle reinforced peptide amphiphile nanomatrix enhances the osteogenic differentiation of mesenchymal stem cells by compositional ratios. Acta Biomater. 8, 4053-4063 (2012)... 

According to Rebouillat et al. [55], cellulose nanoparticles mostly have two major thermal characteristics. The onset of thermal chemical degradation usually occurs at 300°C and 260°C for freeze-dried MCC and NCC (produced via sulfuric acid hydrolysis of the same MCC) respectively. In work by different authors it has been observed that the coefficient of thermal expansion of nanocellulose reinforced composite materials was improved in which coefficient of thermal expansion of the nanoparticle in the axial direction was at 0.1 ppm/K. The value is similar to that of quartz glass. Yano et al. [74] showed that the flexible plastic composites reinforced with this renewable resource have thermal expansion coefficients of 6 x 10 °C. ... 

The DSC studies suggest that the incorporation of coupling agent to the nanoparticle-reinforced polymer composites also increases the glass... 

Nanocomposites consist of a nanometer-scale phase in combination with another phase. While this section focuses on polymer nanocomposites, it is worth noting that other important materials can also be classed as nanocomposites—super-alloy turbine blades, for instance, and many sandwich structures in microelectronics. Dimensionality is one of the most basic classifications of a (nano)composite (Fig. 6.1). A nanoparticle-reinforced system exemplifies a zero-dimensional nanocomposite, while macroscopic particles produce a traditional filled polymer. Nanoflbers or nanowhiskers in a matrix constitute a one-dimensional nanocomposite, while large fibers give us the usual fiber composites. The two-dimensional case is based on individual layers of nanoscopic thickness embedded in a matrix, with larger layers giving rise to conventional flake-filled composites. Finally, an interpenetrating network is an example of a three-dimensional nanocomposite, while co-continuous polymer blends serve as an example of a macroscale counterpart. 

Improved mechanical properties. The addition of small size and low loading of nanoparticles will enhance the matrix-dominated properties such as stiffness, fracture toughness and interlaminar shear strength of conventional fiber-reinforced composites. 

Kelkar et al. [145] investigated the Mode I fracture toughness of glass fiber reinforced composites incorporated with tetraethyl-orthosilicate (TEOS) nanofibrous interlayers and alumina nanoparticles. They found no significant improvement, however only one interlaminar layer was placed between 10 layers of glass fabric. On the other hand, they experienced significant increase in Gju in the case of alumina nanoparticles. Nanoparticles can also be constructed from nanofibers through phase-separation. 

Zhang M Q, Rong M Z and Friedrich K (2003) Processing and properties of non-layered nanoparticle reinforced thermoplastic composites, in Handbook of Organic-Inorganic Hybrid Materials and Nanocomposites, vol. 2 (Ed. Nalwa H S), American Science Publishers, CaUfornia, pp. 113-150. 

If the nanoparticle-reinforced matrix is nsed for a composite laminate, the interlaminar fractnre tonghness and the impact characteristic can be improved at room temperatnre. However, at the cryogenic temperature, unreinforced epoxy may be able to provide better structnral characterization. 

Tensile properties are, by far, the most widely studied mechanical properties of eco-friendly polymer nanocomposites. Overall, the mechanical performance of CNC-reinforced composites depends on the aspect ratio, crystallinity, processing method, and CNC/matrix interfacial interaction. The mechanical properties are proportional to aspect ratio and crystaUinify of nanoreinforcement and it has been shown that increase in aspect ratio and crystaUinify results in increase in mechanical properties. Slow processing methods which encourage water evaporation result in composites with improved properties. This is because nanoparticles have suflticient time to interact and connect to form a continuous network, which is the basis of their reinforcing effect. Nanoreinforcement which is compatible with the biopolymer matrix also exhibits improved mechanical properties of the nanocomposites. 

In conclusion, although their appears to be no general improvement in fire performance when nanoclays are added to conventionally flame-retarded resins, there is evidence that in certain formulations, such as those containing APP and ATH, some benefits are observed, and this opens opportunities for favorable introduction of nanoclays and other nanoparticles in flame retardant resin formulations for use in reinforced composites that have improved fire properties. 

We appreciate all of the efforts that the chapter authors have made to provide an up-to-date account of activities regarding the use of nanocomposites in flame retardancy. We trust that the book will be useful and that it will advance worldwide knowledge on this topic. We would like to thank Don Klosterman and Lynn Bowman of UDRI for their assistance in obtaining references on nano-reinforced composites and nanoparticle health and safety, respectively, and Dr. Anteneh Worku of the Dow Chemical Company for his assistance in obtaining references and reviewing. Finally, we thank our wives, JuUe Ann Morgan and Nancy Wilkie, for their tireless support. 

Polymer nanocomposites consist of a polymer matrix with embedded filler particles with at least one dimension at the nanometre level, (i.e. 1-100 nm), much smaller than for the conventional polymer composites described above. The inclusion of nanoparticles can effect significant improvements in mechanical properties such as modulus, yield stress and fracture toughness for filler levels as low as a few per cent by weight. This is much lower than in conventional polymer composites, as illustrated in Figure 9.7, where the effect of talc reinforcement and clay nanoparticle reinforcement in a polypropylene matrix are compared. Talc filler is regarded as a conventional reinforcement, with particle diameters in the range 1-10 qm and thickness around 20 times less, whereas the clay particles are of length around 100 nm and thickness as low as 1 nm. Clay occurs in the form of platelets and has been... 

Mark JE, Sen TZ, Kloczkowski A. Some Monte Carlo simulations on nanoparticle reinforcement of elastomers. In Karger-Kocis J, Fakirov S, editors. Nano- and micromechanics of polymer blends and composites. New York Hanser Publishers 2009. p. 519-44. 

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