Intercalated nanocomposites rubber

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. 

Polyolefin must be modified to make it become polarized. This polarized polyolefin can then be processed to synthesize a nanocomposite. Rubber does not need to be modified to synthesize a nanocomposite. If we take EPDM as an example, EPDM can be mixed with C18-Mt, and this mixture is intercalated in the clay gallery during vulcanization. When the vulcanization... 

TEM investigation was carried out to examine directly the intercalation of rubber chains and the state of dispersion of the EOMt into the NR matrix. Figure 8.17 shows TEM micrographs of NR nanocomposites with both OMt and EOMt. The thickness of most EOMt tactoids was 7-8 nm and the length about 80-200 nm and these numbers were invariant to the EOMt loading. 

Kong et al. [115] synthesized hy melt-intercalation silicone rubber (SR)/clay nanocomposites using synthetic Fe-montmoriUonite (Fe-MMT) and natural Na-MMT which were modified by cetyltrimethylammoniumbromide, surfactant. They obtained exfoliated and intercalated nanocomposites. With TGA and mechanical performance found that with the presence of iron significantiy increased the onset temperarnre of thermal degradation in SR/Fe-MMT nanocomposites. In addition, the thermal stability, gel fraction and mechanical property of SR/Fe-MMT were different from the SR/Na-MMT nanocomposites, so the iron not only in thermal degradation but also in the vulcanization process acted as an antioxidant and radicals trap. A new flame-retardant system, SR/Fe-OMT based on an EVA matrix, was examined Fang et al. [ 116]. The experimental analyses showed that the exfoliated Fe-OMT had better dispersion in the EVA matrix than Na-OMT, and it was more effective in improving... 

High impact polystyrene (HIPS) is a blend of PS that has been polymerized in the presence of polybutadiene. This leads to PS chains with grafted polybutadiene, as well as some free PS and PB, and the resultant polymer blend has improved impact strength. HIPS/MMT nanocomposites were formed though in-situ bulk polymerization in the presence of polybutadiene [86]. Intercalated nanocomposites with improved thermal stabihty were formed although the dispersion was different in the PS matrix phase compared to the rubber phase. 

Gilman et al. found similar reductions in the PHRR of clay nanocomposites. They prepared 6 wt% intercalated nanocomposites with Cloisite 15A dispersed in a nitrile rubber-modified bisphenol A epoxy-based vinyl ester (mod-bis-A) or a combination of bisphenol A and novolac epoxy-based vinyl ester (bis-A/novolac). The PHRR was reduced by 25 and 39% for mod-bis-A and bis-A/novolac, respectively. The clay promoted charring in fact, no residue was obtained for the neat resins, while in the nanocomposites the residue yields were 8 wt% (mod-bis-A) or 9 wt% (bis-A/novolac). The heat of combustion, specific extinction area, and carbon monoxide yields were unchanged. 

Intercalated nanocomposite, intercalated nanocomposites are formed by the insertion of a rubber chains between the unaltered silicate layers, maintaining their regular alternation of galleries and laminas. 

Intermediate nanocomposites, rubber-clay nanocomposites which are partially intercalated and partially exfoliated, are an intermediate (and often observed) type of nanocomposite. 

This is the most widely used naturally occurring rubber. The literature search shows that many research groups have prepared nanocomposites based on this rubber [29-32]. Varghese and Karger-Kocsis have prepared natural rubber (NR)-based nanocomposites by melt-intercalation method, which is very useful for practical application. In their study, they have found increase in stiffness, elongation, mechanical strength, and storage modulus. Various minerals like MMT, bentonite, and hectorite have been used. 

Rubber-clay nanocomposites are particularly attractive for potential applications where enhanced barrier properties are desired. Organoclays for rubber intercalation were prepared... 

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

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... 

The morphology of rubber-based nanocomposites also seems to change in the presence of compounding ingredients [89, 90]. HNBR, when melt-compounded with organo-modified sodium montmorillonite clays (o-MMTs) prior to sulfur curing, resulted in the formation of nanocomposites with exfoliated or intercalated structures. In stark contrast, under similar conditions HNBR compounded with unmodified sodium montmorillonite clays (NA) formed microcomposites [90]. This was traced to its reactivity with the sulfur in the presence of amine-type organomodifiers. 

There are few reports on rubber-LDH nanocomposites in which they have been prepared mostly by solution intercalation methods and not by a conventional technique for processing rubber-based composites [102, 103]. But, the melt... 

Besides melt intercalation, described above, in situ intercalative polymerization of E-caprolactone (e-CL) has also been used [231] to prepare polycaprolactone (PCL)-based nanocomposites. The in situ intercalative polymerization, or monomer exfoliation, method was pioneered by Toyota Motor Company to create nylon-6/clay nanocomposites. The method involves in-reactor processing of e-CL and MMT, which has been ion-exchanged with the hydrochloride salt of aminolauric acid (12-aminodecanoic acid). Nanocomposite materials from polymers such as polystyrene, polyacrylates or methacrylates, styrene-butadiene rubber, polyester, polyurethane, and epoxy are amenable to the monomer approach. 

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