Nanocomposite foaming

Biodegradable Polymer-based Nanocomposites Nanostructure Control and Nanocomposite Foaming with the Aim of Producing Nano-cellular Plastics... 

For both foam systems, the calculated distribution functions of the cell size from the SEM images are presented in Figure 9.20. The nanocomposite foams nicely obeyed a Gaussian distribution. In the case of PLA/ODA foamed at 150 °C under a high pressure of 24 MPa, we can see that the width of the distribution peaks, which indicates the dispersity for cell size, became narrow, accompanied by a finer dispersion of silicate particles. 

For PLA/MMT-SBE foams prepared under the condition with low Tf ( 100-110 °C) and high pressure ( 28 MPa), the nanocomposite foams exhibit no significant difference in Nc compared with PLA/MMT-ODA foams. This reasoning is consistent with the large value of W in both systems. 

Figure 9.28 shows the relation of the relative modulus (Ktf Kp) to the relative density (Pf/Pp) of neat PLA and PLA-based nanocomposite foams, taken in the directions parallel (A) and perpendicular (B) to the flow. 

To clarify whether the modulus enhancement of the nanocomposite foams was reasonable, Equation (9.7) proposed earlier by Kumar [66] was applied to estimate the relative moduli with various foam densities ... 

Chen, M., Chen, B., Evans, J. R. G. (2005). Novel thermoplastic starch-clay nanocomposite foams. Nanotechnol-... 

Modesti, M. Lorenzetti, A. Besco, S. Hrelja, D. Semenzato, S. Bertani, R. Michelin, R.A.. Synergism between flame retardant and modified layered silicate on thermal stability and fire behaviour of polyurethane nanocomposite foams. Polym. Degrad. Stab. 2008, 93, 2166-2171. 

Okamoto, M., Nam, P. H., Maiti, R, Kotaka, T., Nakayama, T., Takada, M., Ohshima, M., Usuki, A., Hasegawa, N., and Okamoto, H., Biaxial flow-induced alignment of sUicate layers in polypropylene/clay nanocomposites foam. Nano Lett., 1, 503-505 (2001c). 

M. Liu, Z. S. Petrovic and Y. Xu, Bio-based polyurethane-clay nanocomposite foams syntheses and properties . Mater Res Soc Symp Proc, 2009, 1188, 1188-LL04-05. 

Fujimoto Y, Sinha Ray S., Okamoto M., Ogami A., Yamada K., Ueda K., Well-controlled biodegradable nanocomposite foams From microcellular to nanoceUular, Macromol. Rapid. Commun., 24, 2003, 457 61. 

Y. Fujimoto, et al, Well-controlled biodegradable nanocomposite foams from microcel-lular to nanocellular, Macromolecular Rapid Communications 24 (7) (2003) 457-461. 

Wu, Sh., Ju, H., and Liu, Y. 2007. Conductive mesocellular silica-carbon nanocomposite foams for immobilization, direct electrochemistry, and biosensing of proteins. Adv. Funct. Mater. 17 585-592. 

Darder M, Matos CRS, Aranda P, Ruiz-Hitzky E (2010) Sepiolite-based nanocomposites foams. In Proceedings of the SEA-CSSJ-CMS trilateral meeting on clays. Sevilla, pp 357-358. (ht /Avww.sea-arcillas.es ublicaciones/2010%20SEA-CSSJ-CMS%20Trilateral %20Meeting%20(m%2(X)lays.pdf)... 

Frydrych M, Wan C, Stengler R, O Kelly KU, Chen B (2011) Stmcture and mechanical properties of gelatin/sepiolite nanocomposite foams. J Mater Chem 21 9103-9111... 

Quadrini et al. developed a solid-state process to yield epoxy foams with different contents of nanoclay (up to 10%wt) [86]. They demonstrated excellent shape memory properties for the nanocomposite foams with low filler loadings and were able to control porosity by varying the solid precursors during the foaming process. 

Frydrych, M., C. Wan, R. Stengler, K.U. O Kelly, and B. Chen. 2011. Stiucture and mechanical properties of gelatin/sepiolite nanocomposite foams. Journal of Materials Chemistry 21(25) 9103-9111. 

The nanocomposite foams showed smaller cell size and larger cell population density compared to neat PLA foam. This behavior was attributed to the dispersed silicate particles that acted as nucleating sites for cell nucleation. 

FIGURE 17.5 Master plot of density versus Tf + ATg (redueed foaming temperature) using data of both neat PLA and PLA-based nanocomposites foamed under various CO2 pressures (14-30 MPa) [41]. Nanocomposite specimens and PLA type are described in Table 17.3. 

The compressive strength of PU foams can be significantly increased through the incorporation of multi-walled carbon nanotubes (CNTs) into the polymer solution prior to phase separation. The CNTs can be observed at the polymer surface, giving the surface a rough hairy texture, and appear to be uniformly distributed throughout the bulk of the material. Culture of SaOS-2 osteosarcoma cells on PU/CNT nanocomposite foams indicated that... 

Lee S, Cho W, Hahn P, Lee M, Lee Y, Kim K (2005) Microstructural changes of reference montmorillonites by cationic surfactants. Appl Clay Sci 30(3-4) 174-180 Lee SM, Tiwari D (2012) Organo and inorgano-organo-modified clays in the remediation of aqueous solutions an overview. Appl Clay Sei 59-60 84—102 Lee S Y, Chen H, Hanna M A (2008) Preparation and eharacterization of tapioca stareh-poly(lactic add) nanocomposite foams by melt intercalation based on elay type. Ind Crops Prod 28(1) 95-106 Lee SY, Hanna MA (2009) Tapioca starch-poly(lactic acid)-Cloisite 30B nanocomposite foams. Polym Compos 30(5) 665-672... 

Lee S-Y, Hanna MA (2008) Preparation and eharacterization of tapioca starch-poly(lactic add)-Cloisite NA-l- nanocomposite foams. J Appl Polym Sei 110(4) 2337-2344 Leite IF, Soares APS, Carvalho LH, Raposo CMO, Malta OML, Silva SML (2009) Characterization of pristine and purified organobentonites. J Therm Anal Calorim 100... 

Lee SY, Xu YX, Hanna MA (2007) Tapioca starch-poly (lactic acid)-based nanocomposite foams as affected by type of nanoclay. Int Polym Process 22(5) 429-435 Lee B-H, Kim H-S, Lee S, Kim H-J, Dorgan JR (2009) Bio-composites of kenaf fibers in polylactide role of improved interfacial adhesion in the carding process. Compos Sci Technol 69 2573-2579... 

Few examples of nanocomposites in which the cellulosic nanostructure is used in biobased thermosets can be also foimd. Due to the fact that these environment friendly composites suffer from several limitations, such as low mechanical properties due to low strength in reinforcement plus inadequate interfacial strength, and that cellulose nanostructures have been shown to have significant potential as a reinforcement, the possibility of using cellulose nanofibers as reinforcements in a bio-derived resin was revised. In Masoodi et al. [200], cellulose nanofibers were used as reinforcements in the forms of layered films, while in Lee et al. [201] the stability of the gas-soybean oil foam templates and the mechanical properties of the polymer nanocomposite foams are enhanced upon the addition of bacterial cellulose nanofibrils. Other examples of biobased thermosets containing cellulosic nanoreinforcements are the work of Shibata [202] in which the use of a biobased epoxy was revised, and systems in which cellulose nanocrystals are incorporated in biobased polyurethanes [203,204], Few examples exist also in the literature on the polymerization of furfuryl alcohol in presence of CNR [205,206] in these papers, the authors established the feasibility of producing furfuryl... 

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