Nanoclays, use

Jash and Wilkie [86] reported that even when the fraction of clay was as low as 0.1 wt% the PBQiR in a cone calorimeter was lowered by 40 %. Lee et al. [87] demonstrated that incorporation of 6, 8 and 10 wt% of MMT into epoxy resin increased linearly the char yield firom 9.1 to 15.4 % reducing the thermal degradation of the epoxy matrix. Nazare et al. [88] studied the flammability properties of unsaturated polyester resin with nanoclays using cone calorimetry. The authors verified that the incorporation of 5 wt% of nanoclays reduces the PHRR by 23-27 % and THR values by 4-11 %. While incorporation of condensed-phase flame retardants (such as ammonium polyphosphate, melamine phosphate and alumina trihydrate) reduce the PHRR and THR values of polyester resin, the inclusion of small amounts of nanoclay (5 % w/w) in combination with these char promoting flame retardants causes total reductions of the PHRR of polyester resin in the range 60-70 %. Ammonium polyphosphate, in particular and in combination with polyester-nanoclay hybrids show the best results compared to other flame retardants. 

Using data on the surface tension values of the rubbers and nanoclays used, the master curve of filler localization in 50/50 HNBR/NR and 50/50 HNBR/ ENR blends was calculated and is presented in Figure 6.24(a). A clay fraction of about 0.9 and 1.0 localized in the HNBR phase of HNBR/ENR and HNBR/ NR blends, respectively, was found, i.e. an almost complete localization of clay in the HNBR is predicted for both blends, when they reach a thermodynamic equilibrium state. Thus, at the beginning of the preparation of HNBR/ (NR-clay masterbatch) and HNBR/(ENR-clay masterbatch) blends, nanoclay pre-mixed in the NR and ENR phase is far away from its equilibrium state. Nanoclay is expected to migrate to the HNBR phase during the blending process. 

In this chapter, we present a summary of fire retardant nanoclays used in polymer blends based on the authors previous experience and the literature [15-31]. Because the main objective of this work is to study the fire retarding effects of nanoclays on polymer blends, we will focus on the properties affecting the fire performance of polymer blends (a) dispersion of nanoclay, (b) rheology, (c) thermal stability, and (d) flammability (ignition, fire spread, and toxicity), whereas the effects of nanoclays on mechanical properties and compatibilization can be found easily in references listed in Table 8.1 (e.g.. References [16, 17, 19-21] on compatibilization and [16, 18, 21, 25, 26, 29-31] on mechanical properties). A review of the mechanism by which nanoparticles organize in polymer blends is also available in [32]. 

Schmidt B, Petersen JH, Koch CB et al (2009) Combining asymmetrical flow field-flow fractionation with light-scattering and inductively coupled plasma mass spectrometric detection for characterization of nanoclay used in biopolymer nanocomposites. Food Addit Contam 26A(12) 1619-1627... 

Dharaiya, D., Jana, S. Measurement Of Surface Polarity Of Organically Treated Nanoclay Using Contact Angle M od. Antec. 63 2213-2216 (2005)... 

One of the few disadvantages associated with nanoparticle incorporation concerns the loss of some properties. Some of the data presented have suggested that nanoclay modification of polymers such as polyamide could reduce impact performance [28]. Nanofillers are sometimes very matrix-specific. High cost of nanofillers prohibits their use. 

This is a nonpolar rubber with very little unsamration. Nanoclays as well as nanotubes have been used to prepare nanocomposites of ethylene-propylene-diene monomer (EPDM) rubber. The work mostly covers the preparation and characterization of these nanocomposites. Different processing conditions, morphology, and mechanical properties have been smdied [61-64]. Acharya et al. [61] have prepared and characterized the EPDM-based organo-nanoclay composites by X-ray diffracto-gram (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy... 

This is another important and widely used polymer. Nanocomposites have been prepared based on this rubber mostly for flame-retardancy behavior. Blends with acrylic functional polymer and maleic anhydride-grafted ethylene vinyl acetate (EVA) have also been used both with nanoclays and carbon nanotubes to prepare nanocomposites [65-69]. 

Fluoroelastomer-based nanocomposites were prepared using various nanoclays and their different properties were studied [93-98]. 

The aspect ratio of the nanoclays in different samples has been calculated using Equation 2.11 and is reported in Table 2.6. 

This is a highly polar polymer and crystalline due to the presence of amide linkages. To achieve effective intercalation and exfoliation, the nanoclay has to be modified with some functional polar group. Most commonly, amino acid treatment is done for the nanoclays. Nanocomposites have been prepared using in situ polymerization [85] and melt-intercalation methods [113-117]. Crystallization behavior [118-122], mechanical [123,124], thermal, and barrier properties, and kinetic study [125,126] have been carried out. Nylon-based nanocomposites are now being produced commercially. 

Effects of nanoclay and silica in mbber matrices have been discussed in earlier chapters. Recently, several other nanofillers have been investigated and have shown a lot of promise. All these fillers have not been investigated on rubbers extensively, although they have great potential to do so in the days to come. In this chapter, we have compiled the current research on mbber nanocomposites having nanofillers other than nanoclay and nanosilica. Further, this chapter provides a snapshot of the current experimental and theoretical tools being used to advance our understanding of mbber nanocomposites. 

The future direction of polyester R D efforts is likely to involve further progress in polyester synthesis given the wide range of potential monomer combinations, new blending technology and the use of advanced functional additives such as nanoclay reinforcements, reactive impact modifiers, anti-hydrolysis agents and chain extenders. 

A 6% nanoclay-PP composite is used for the structural seat back of the Honda Accura TF 2004 car. This Forte 35CPP091 grade replaces a 30% glass PP compound in the seat back. 

The most important materials developed are nanocomposites and nanotubes. Fabrication of the first nanocomposites was inspired by nature (biomineralisation). Nanocomposites based on nanoclays and plastics are seen as ideal materials for improved barrier properties against oxygen, water, carbon dioxide and volatiles [37]. This makes them in particular suitable for retaining flavours in foods. The technology is rather straightforward using commercially available nanoclays and extrusion processing. 

Choudhury et al. [36] in their work on hydrogenated nitrile butadiene rubber (HNBR)-nanoclay systems showed the thermodynamic aspects of nanocomposite formation using the mean-field-lattice-based description of polymer melt intercalation, which was first proposed by Vaia and Giannelis [37]. Briefly, the free... 

In subsequent discussion, we will demonstrate the use and interpretation of some of these techniques. Figure 2a shows typical XRD traces of nanocomposite systems of styrene butadiene rubber (SBR) containing unmodified and modified nanoclay, describing an exfoliated and intercalated nanocomposite [5]. photographs of these systems are also given in the same figure (Fig. 2b, c). In the present case, the information obtained from both the techniques is complimentary. 

Values of Example were calculated for the constituting domains of SEBS (PS and PEB) and for the nanoclay regions in the SEBS/clay nanocomposite using (6) and are provided in Table 2. The modulus of the clay platelets was found to be 100 MPa, whereas the modulus for PS and PEB blocks was determined to be 22 and 12 MPa, respectively. These modulus values tallied with the slow strain-rate macromechanical tensile data of 26 MPa for the SEBS/clay nanocomposite (Table 2). The lower calculated modulus values of nanoclays compared to the literature might be due to adhering soft rubber on the nanoclays, which reduces the overall modulus of clay regions in the composite. 

Rubber-based nanocomposites were also prepared from different nanofillers (other than nanoclays) like nanosilica etc. Bandyopadhyay et al. investigated the melt rheological behavior of ACM/silica and ENR/silica hybrid nanocomposites in a capillary rheometer [104]. TEOS was used as the precursor for silica. Both the rubbers were filled with 10, 30 and 50 wt% of tetraethoxysilane (TEOS). The shear viscosity showed marginal increment, even at higher nanosilica loading, for the rubber/silica nanocomposites. All the compositions displayed pseudoplastic behavior and obeyed the power law model within the experimental conditions. The... 

The X-ray diffraction peaks observed in the range of 3°-10° for the modified clays disappear in the rubber nanocomposites. photographs show predominantly exfoliation of the clays in the range of 12 4 nm in the BIMS. Consequently, excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus is observed by the incorporation of the nanoclays in the BIMS. Maiti and Bhowmick have also studied the effect of solution concentration (5, 10, 15, 20, and 25 wt%) on the properties of fluorocarbon clay nanocomposites [64]. They noticed that optimum properties are achieved at 20 wt% solution. At the optimized solution concentration, they also prepared rubber/clay nanocomposites by a solution mixing process using fluoroelastomer and different nanoclays (namely NA, 10A, 20A, and 30B) and the effect of these nanoclays on the mechanical properties of the nanocomposites has been reported, as shown in Table 4 [93]. 

In addition, Maiti and Bhowmick [93] also used fluoroelastomers having different microstructure and viscosity (Viton B-50, Viton B-600, Viton A-200, and VTR-8550). Viton is a terpolymer of vinylidene fluoride (VF2), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE). Even with the addition of only 4 phr of clay in Viton B-50, the tensile strength and modulus improved by 30-96% and 80-134%, respectively, depending on the nature of the nanoclays. The better polymer-filler interaction in the case of NA clay and the fluoroelastomers has... 

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