Intermediate nanocomposites

Intermediate nanocomposites the nanocomposite contains both intercalated and exfoliated clay platelets. 

Figure 9.2 Types of clay-polymer composites (a) microcomposites, (b) intercalated nanocomposites, (c) intermediate nanocomposites, (d) exfoliated nanocomposites.

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

The engineering of novel deviees requires, in many eases, materials with finely seleeted and preestablished properties. In partieular, one of the most promising lines of synthetic materials research consists in the development of nanostructured systems (nanocomposites). This term describes materials with structures on typical length scale of 1-100 nm. Nanometric pieces of materials are in an intermediate position between the atom and the solid, displaying electronic, chemical and structural properties that are distinct from the bulk. The use of nanoparticles as a material component widens enormously the available attributes that can be realised in practice, which otherwise would be limited to bulk solid properties. 

Fig. 1.7 Scanning electron micrographs showing fractal pattern formation by hierarchical growth of fluorapatite-gelatin nanocomposites (A) half of a dumbbell aggregate viewed along the central seed axis, (B) dumbbell aggregate at an intermediate growth state, and (C) central seed exhibiting tendencies of splitting at both ends ( small dumbbell). Adapted from [119], reproduced by permission ofWiley-VCH.

If R can react with itself or additional components (R contains vinyl, methacryl or epoxy groups, for example), the result of the condensation process is a flexible network of inorganic oxide covalently bonded to organic polymers, namely a hybrid nanocomposite lacking interface imperfections. The properties of this hybrid nanocomposite are intermediate between those of polymers and glasses, and can meet unique requirements. 

The heat release rate curves shown in Fig. 4A are consistent with the characteristic burning patterns of intermediate thick, non-charring samples (II). The PHRR values for PE-ZCHS-5 and PE-ZCHS-10 nanocomposites are reduced by 27 and 25% relative to the pure PE respectively. For smectite clay/polymer nanocomposites, reduction in PHRR has been shown to be correlated with nanodispersion of the additive in the polymer matrix (72). With HDS and related layered metal hydroxide additives, we have also only found PHRR reduction in the case of PVE with CHDS, a system with some... 

The Pt-containing (2-4% Pt) nanocomposite beads placed in an aqueous basic solution of L-sorbose catalyze oxidation of the latter with O2 to 2-keto-L-gulonic acid, an intermediate in the production of vitamin C [399]. Within first 100 min at 60—80°C the catalytic activity gradually develops, resulting in a 100% convenion of L-sorbose with the yield of ketogulonic acid up to 98% [400]. With the size of Pt clusters controlled by the size of matrix network meshes, the catalytic properties of the composite material remain stable even after 30—50 reaction cycles... 

The only peak at 254.5 °C observed in the as-received nanoparticles, as shown in Figure 12.5(b), is due to the decomposition of the iron oxide-hydroxide (goethite, FeOOH as proved by theFT-IR spectra) [31,76]. Similar to the TGA observation, a higher decomposition temperature (308.0 °C) was observed in PPy formed with the aid of nanoparticles than that of pure PPy formed without them (298.4 °C). Whereas only one peak was observed in the pure PPy samples, two exothermic peaks were observed in the DTA curves of the nanocomposites. These were due to the decomposition of PPy at 307 °C and the possible phase transition of iron oxide at 480 °C, as reported for the Fc203/PPy nanocomposites fabricated by the simultaneous gelation and polymerization (sol-gel) method [77,78] respectively. As compared with no obvious phase transition in the pure iron oxide nanoparticles, the observed phase transition was due to the intermediate product of PPy [77,78]. 

Several authors used the continuum mechanics for modeling conventional polymer composites as well as PNC. Ren and Krishnamoorti [2003] used a K-BKZ integral constitutive model to predict the steady-state shear behavior of a series of intercalated nanocomposites containing an organo-MMT and a disordered styrene-isoprene diblock copolymer. The model predicts the low-y shear stress properties calculated from the experimental linear stress relaxation and the relaxation-based damping behavior. However, as it does not take into account the effect of clay platelet orientation, it is unable to predict the shear stress behavior at intermediate y and the normal stress behavior at all y and clay contents. 

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