Addition of Nanoparticles

The specific surface area increased substantially upon addition of the nanoparticies from 4.14 m /g to 345 m /g with 4.29% loading. These materials are expected to find important applications in dental composites. 

Two-step processes to generate nanoprotrusions on electrospun fibers have also been studied. Nanofiber shish kebabs by electrospinning poly(s-caprolactone) (PCL) followed by solution crystallization of PCL or a copolymer of PCL and PEO was obtained.  

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Polypropylene (PP) is one of the most widely used plastics in large volume. To overcome the disadvantages of PP, such as low toughness and low service temperature, researchers have tried to improve the properties with the addition of nanoparticles that contains p>olar functional groups. An alkylammonium surfactant has been adequate to modify the clay surfaces and promote the formation of nanocomposite structure. Until now, two major methods, i.e., in-situ polymerization( Ma et al., 2001 Pirmavaia, 2000) and melt intercalation ( Manias et al.,2001) have been the techniques to prepare clay/PP nanocomposites. In the former method, the clay is used as a catalyst carrier, propylene monomer intercalates into the interlayer space of the clay and then polymerizes there. The macromolecule chains exfoliate the silicate layers and make them disperse in the polymer matrix evenly. In melt intercalation, PP and organoclay are compounded in the molten state to form nanocomposites. 

It has been reported recently that flux and even selectivity of PMP and PTMSP can be enhanced by the addition of nanoparticles (285, 286]. Merkel et al. [285] added fumed sihca to PMP and observed a simultaneous increase of butane flux and butane/methane selectivity. This unusual behavior was explained by fumed-silica-induced disruption of polymer chain packing and an accompanying increase in the size of free volume elements through which molecular transport occurs. Gomes et al. [286] incorporated nanosized sihca particles by a sol-gel technique into PTMSP and found also for this polymer a simultaneous increase in flux and selectivity. It has to be studied, if physical aging of the polyacetylenes is reduced by the addition of nanoparticles. 

Nowadays, nanoparticles have been widely used as fillers and compatibilizers. They exert certain effect on the miscibility of blends. Ginzburg applied a simple theory to study the effect of nanoparticles on the miscibility of PVA/PMMA blends and compared theoretical and experimental results for the same system with fillers and without fillers (Ginzburg 2005) when nanoparticle radius is smaller than polymer radius of g5n ation, the addition of nanoparticles increases the critical value of Xn and stabilizes the homogeneity (Fig. 10.38). 

The addition of nanoparticles to an immiscible blend greatly influences the viscosity ratio of the dispersed to continuous phase which in turn changes the phase inversion composition. When hydrophobic silica particles were added to... 

Compatibilization of polymer blends aims to improve the interaction between phases, ascertaining the appropriate, stable morphology and improved performance. Blends have been compatibilized mainly by addition of a compatibilizer, a co-solvent, or in a reactive process, where the compatibilizing molecules are formed within the interphase [1, 73, 302]. About 20 years ago a note in a USSR technological journal reported that the addition of a small amount of PMMA to a PE/PS blend reduced the PS drop diameter by a factor of ten. The effect was later explained by a balance of the three interfacial tension coefficients in the blends, inter-related by Neuman s triangle equation [1,352,353]. In simple terms, the PMMA, immiscible in PE and PS, formed a layer around PS drops, preventing coalescence. In a sense, addition of nanoparticles to polymer blends acts similarly. 

The addition of nanoparticles to synthetic mbber resulting in enhancement in thermal, stiffness and resistance to fracture is one of the most important phenomena in material science technology. Thermal and mechanical properties of clays mul-tiwalled carbon nanotubes reinforced ethylene vinyl acetate (EVA) prepared through melt blending showed synergistic effect in properties [86]. Malas et al. reported (SBR/BR)/expanded graphite (EG) and black carbon (CB) nanocomposites by melt blending, this study demonstrated that the presence of EG improvement thermo-mechanical properties and the presence of CB are a factor important to... 

The main conclusion from all the above is that except of MMT, where contradictory results were reported, in all other nanocomposites the addition of nanoparticles can lead to thermal stabilization effect of polymers during their decomposition. However, in this direction the effect of nanoparticles content is very crucial. In most of the cases the thermal stability enhancement takes place at low loading (4-5 wt%) of nanoparticles while at higher contents thermal stabilization becomes progressively lower. This is because at higher concentrations nanoparticles can form aggregates and thus effective area of nanoparticles in contact with polymer macromolecular is lower. In this case microcomposites may are formed instead of nanocomposites and thus the protective effect of nanoparticles becomes lower [22]. 

The addition of nanoparticles in the material formulations represents the key of polymer modification [193], which brings about the attaining upgraded performances simultaneously with the compatibilization of various blends. The features of polymer nanocomposites can be converted by high energy exposure and their application can be extended due to the favorable adjustment. 

In conclusion the addition of nanoparticles can lead to thermal stabilisation effect of polymer during their decomposition. However in this sense the effect of nanoparticles content is very crucial due at higher concentration nanoparticles can form aggregates and the effective area of nanoparticles in contact with polymer macro-molecular is lower. The thermal stability enhancement takes place at low loading of nanoparticle. 

It was shown that water suspension of iron oxide nanoparticles got heated much faster than water without nanoparticles. Thus, addition of nanoparticles to microcapsule shells should lead to local heating. Iron oxide (Fe304) nanoparticles are very sensitive to microwave radiation because of significant elecrical loss. 

Addition of nanoparticles results in less coalescence of particles during the melt processing, causing improved compatibilization. For example, exfoliated clay compatibilization, snch as in a polycarbonate/polymethylmethacrylate (PC/ PMMA) system, polyphenylene oxide/polyamide (PPO/PA), polyamide/ethyl-ene propylene diene elastomer (PA/EPDM) rnbber, polystyrene/polymethyl-methacrylate (PS/PMMA), and polyvinyl fluoride/polyamide-6 (PVF/PA) blends, is affected by lowering the interfacial tension between the two phases that are phase separated. 

The most stable morphology of a BCP can be changed on the addition of nanoparticles, which show selectivity for one of the polymer domains. Effectively, this approach increases the volume fraction of the polymer block for which the nanoparticles show selectivity. For example, Yeh et al showed that a cylindrical-forming poly(styrene-fc-4-vinylpyridine) could form a lamellae morphology on... 

The addition of nanoparticles such as carbon nanotubes, clay, silica, and mica to polymers can cause an increase or decrease in the determined value of Tg. Table 4.7 illustrates positive or negative changes in Tg following the inclusion of various nanoparticles in the polymer formulation. 

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