Nanocomposites MWNT/PMMA

L. Qiliu, H.D. Wagner, A comparison of the mechanical strength and stiffness of MWNT-PMMA and MWNT-epoxy nanocomposites. Compos. Interfaces 14 (2007) 285-297. 

Figure 6.13 shows the electrical conductivity versus filler content for the MWNT/PMMA nanocomposites prepared by solution mixing. Acid purified MWNTs... 

Figure 6.15. Variation of volume resistivity with nanotube loading for different MWNT/PMMA nanocomposites. Reproduced from [61] with permission from Elsevier...

A large amount of research has been reported on the mechanical properties of CNT reinforced plastic materials. In the early days, pristine CNTs were mostly used to fabricate CNT nanocomposites. The PMMA nanocomposites were prepared by melt blending, and the nanotubes were well dispersed in the matrix with no apparent damage or breakage. The storage modulus of the PMMA matrix is significantly increased by the incorporation of pristine MWNTs, particularly at high temperatures [90]. 

Chen L., Ozisik R., and Schadler L. S., The influence of carbon nanotube aspect ratio on the foam morphology of MWNT/PMMA nanocomposite foams. Polymer 2010, 51, 2368-2375. 

Figure 5.8 Evolution of reduced modulus of several MWNT-PMMA nanocomposites. Adapted from Ref [171].

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. 

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. 

For bulk materials, Jin et al fabricated poly (methylmethacrylate) (PMMA)/MWNT nanocomposites by melt mixing. MWNTs were well dispersed in the matrix [90]. Melt compounding is also widely used for the fabrication of composite fibers. Sandler et al mixed polyamide-12 pellets and CNTs in a twin-screw micro-extruder and then the extrudate was chopped and fed into a capillary rheometer with 1 mm die. The CNTs in the spun fibers were uniformly dispersed [91]. Not only can thermoplastic polymers be melt-compounded, polyimide, a thermoset plastic, can be also prepared by mixing the imide oligomer at 320 °C on a steel plate and then cured at 370°C. It was found that the dispersion of CNTs in... 

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. ... 

Yeh et al. (2009) investigated the effect of nanoclay on the dielectric and thermal transport properties of PMMA nanocomposite foams. As shown in Figure 1.18, the nanocomposite foams showed lower dielectric constants than the neat PMMA foam. And the effect is more prominent when the clay nanoparticles were better dispersed (CCLMA clay) and when the clay concentration was increased. The effect on thermal conductivity (Figure 1.19) was slightly more complicated. While the nanocomposite foams with better dispersion, that is, CCLMA nanocomposites with an exfoliated-intercalated mixed morphology, showed a deaease in thermal conductivity, the thermal conductivity of the intercalated ACLMA nanocomposite foam was higher than that of neat PMMA foam. They have also prepared PMMA M WCNT nanocomposite foams and measured their insulation property. Interestingly, they noticed a decrease in both dielectric constant (22.6%) and thermal conductivity (19.7%) in the nanocomposite foams with 0.3 wt% carboxyl-multi-walled carbon nanotubes (c-MWNTs). 

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