SWNT-PMMA nanocomposite

Figure 10.3 Optical micrographs of a SWNT-PMMA nanocomposite having 1 wt% purified soot (a) only sonication and drying. The as-cast film is repeatedly subjected to hot pressing (180°C, 30001b, 3 min) and is shown here after (b) 1 cycle (c) 5 cycles (d) 20 cycles. (Reproduced with permission from Elsevier [59].)...

Figure 6.12. Dependence of electrical conductivity on nanotube concentration in SWNT/PMMA nanocomposites. Reproduced from [87] with permission from Elsevier...

Figure 30 Storage modulus at 200 °C (a) and electrical conductivity at room temperature (b) measured for SWNT/PMMA nanocomposites of various SWI fT loading iVf. Data taken from Du, F. M. Scogna, R. C. Zhou, W. et at. Macromolecules 2004, 37,9048 with permission.

Regardless of the nature of these nanotubes, their dispersion state in the host polymer is crucial and its improvement is a challenge to achieve the best lire performance of the corresponding nanocomposites. For example, Kashiwagi et al.9 have shown that in PMMA well-dispersed SWNTs led to a strong decrease in PHHR in cone calorimeter tests, while poorly dispersed SWNTs did not modify HRR in comparison with pristine PMMA. 

Many studies have used these methods for processing of both thermosetting and thermoplastic polymers. Y. Liao (53) dissolved epoxy in a well-dispersed, ultra-sonicated CNT suspension. The solvent was evaporated, and the epoxy was subsequently cured to form a nanocomposite in which the good CNT dispersion was achieved. Jin et al. (54) produced various types of polymer-coated and polymer-grafted MWNT solutions, in some cases evaporating the solvent and subsequently melt-mixing with another polymer. Yudasaka et al. (55) used a mixture of SWNTs and PMMA in monochlorobenzene (MCB) for dispersion, purification and subsequent spin-casting of the material. 

Kashiwagi T, Fagan J, Douglas J F, Yamamoto K, Heckert A N, Leigh S D, Obrzut J, Du F, Lin-Gibson S and Mu M (2007) Relationship between dispersion metric and properties of PMMA/ SWNT nanocomposites, Polymer 48 4855-4866. 

SWNTs for the flammability study of PMMA-SWNT nanocomposites were synthesized by the high-pressure carbon monoxide method (HiPCO) and the coagulation method was used to produce PMMA-SWNT nanocomposites in... 

FIGURE 10.18 Effect of SWNT dispersion on heat release rate of PMMA-SWNT (0.5%) nanocomposites at an external radiant flux of 50 kW/m. (From Ref. 58.)... 

The effects of the concentration of MWNTs in PP on the heat release rate curves of the nanocomposites are shown in Figure 10.25. The results show two distinct characteristics brought on by the addition of MWNTs first, there is a shortened ignition delay time with the PP-MWNT(0.5%), followed by an increase in ignition delay time with an increase in the concentration of MWNT second, there is a gradual increase in peak heat release rate above about 1% by mass of MWNT. A similar trend was observed for PMMA-SWNT nanocomposites (less obvious for PMMA-SWNT, due to a lower concentration of SWNT, as shown in Figure 10.20). The lowest heat release rate curve for PP-MWNT is achieved with about 1% by mass of MWNT compared to about 0.5% by mass of SWNT. The increase in peak heat release rate with concentration of MWNT above 1% appears to be due to an increase in thermal conductivity of the nanocomposite. ... 

As an example of the behavior of such nanocomposites. Figure 30a shows storage modulus G measured for blends of single-wall carbon nanombe (SWNT) in a matrix of poly(methyl methacrylate) (PMMA M = 1.0 x 10 ). ° The nanotubes are uniformly dispersed in the range of the nanotube content Wf examined, but the blends exhibit elastic (solid-like) response, cu-insensitive G plateau at low cu, as Wf is inaeased beyond a threshold value Wf c (=0.12wt.% determined from percolation analysis ). This plateau is attributable to the motional constraint on the polymer chains due to a nanotube network formed through these chains. The elasticity of the... 

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