Polymer nanocomposites characteristics

The fire toxicity of each material has been measured under different fire conditions. The influence of polymer nanocomposite formation and fire retardants on the yields of toxic products from fire is studied using the ISO 19700 steady-state tube furnace, and it is found that under early stages of burning more carbon monoxide may be formed in the presence of nanofillers and fire retardants, but under the more toxic under-ventilated conditions, less toxic products are formed. Carbon monoxide yields were measured, together with HCN, nitric acid (NO), and nitrogen dioxide (NO2) yields for PA6 materials, for a series of characteristic fire types from well-ventilated to large vitiated. The yields are all expressed on a mass loss basis. 

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... 

Fluorescent naphthol-based polymers were prepared by HRP-catalyzed polymerization of 2-naphthol in AOT/isooctane reverse micelles to give the polymer microspheres.31 The precipitated polymer was soluble in a range of polar and nonpolar organic solvents and possessed quinonoid structure. The reverse micellar system induced the peroxidase-catalyzed copolymerization of p-hydroxythiophenol and />ethylphenol, yielding the thiol-containing polyphenol particles.32 The attachment of CdS to the particles gave the CdS—polymer nanocomposite showing fluorescence characteristics. 

The linear viscoelastic properties in the melt state of highly grafted polymers on spherical silica nanoparticles are probed using linear dynamic oscillatory measurements and linear stress relaxation measurements. While the pure silica tethered polymer nanocomposite exhibits solid-like response, the addition of a matched molecular weight free matrix homopolymer chains to this hybrid material, initially lowers the modulus and later changes the viscoelastic response to that of a liquid. These results are consistent with the breakdown of the ordered mesoscale structure, characteristic of the pure hybrid and the high hybrid concentration blends, by the addition of homopolymers with matched molecular weights. 

The rheological behavior of these materials is still far from being fully understood but relationships between their rheology and the degree of exfoliation of the nanoparticles have been reported [73]. An increase in the steady shear flow viscosity with the clay content has been reported for most systems [62, 74], while in some cases, viscosity decreases with low clay loading [46, 75]. Another important characteristic of exfoliated nanocomposites is the loss of the complex viscosity Newtonian plateau in oscillatory shear flow [76-80]. Transient experiments have also been used to study the rheological response of polymer nanocomposites. The degree of exfoliation is associated with the amplitude of stress overshoots in start-up experiment [81]. Two main modes of relaxation have been observed in the stress relaxation (step shear) test, namely, a fast mode associated with the polymer matrix and a slow mode associated with the polymer-clay network [60]. The presence of a clay-polymer network has also been evidenced by Cole-Cole plots [82]. 

Graphene-polymer nanocomposites share with other nanocomposites the characteristic of remarkable improvements in properties and percolation thresholds at very low filler contents. Although the majority of research has focused on polymer nanocomposites based on layered materials of natural origin, such as an MMT type of layered silicate compounds or synthetic clay (layered double hydroxide), the electrical and thermal conductivity of clay minerals are quite poor [177]. To overcome these shortcomings, carbon-based nanofillers, such as CB, carbon nanotubes, carbon nanofibers, and graphite have been introduced to the preparation of polymer nanocomposites. Among these, carbon nanotubes have proven to be very effective as conductive fillers. An important drawback of them as nanofillers is their high production costs, which... 

Varying the polymer type and characteristics allows development of sophisticated metal-polymer nanocomposites with tunable properties and promise for future apphcations. Yet, one can expect vigorous development of this field for years to come so that new polymeric systems yielding better control over nanoparticle formation and properties will be designed. 

Polymer-embedded gold nanoparticles have been extensively studied [1]. Because of unique physical characteristics, gold-polymer nanocomposites are potentially useful for a number of advanced functional applications, especially in the optical and photonic fields. In particular, these materials can be used as light-stable color filters [2], polarizers [3, 4], ultra-low refractive index materials [5], nonlinear optical devices [6], optical sensors [7], and so on. However, still limited are the chemical routes that allow us to obtain monodispersed thiol-derivatized gold nanoparticles with controlled size to be embedded into poly-... 

Polymer nanocomposites multicomponentness (multiphaseness) requires their stmctural components to be quantitative characteristics determination. In this aspect, interfacial regions play a particular role, as it has been shown earlier, that they are the same reinforcing element in elastomeric nanocomposites as nanofiller actually [ 1 ]. Therefore, the knowledge of interfacial layer dimensional characteristics is necessary for quantitative determination of one of the most important parameters of polymer composites, in general,— their reinforcement degree [2, 3]. 

Table 17.2 Electrocatalytic characteristics of conducting polymer nanocomposites...

Polymer nanocomposites Catalyzed species Catalysis method Characteristics Ref. 

Recently, the production of nanofibres using nanocomposites has attracted attention. This is due to the fact that this type of nanofibre combines the unique properties of nanocomposites with the outstanding characteristics of nanofibres. Metal/polymer nanocomposites have not only the potential to meet the requirements of applications such as photonic and electric sensors, filters, and artificial tissue, but also can act as catalysts. Silver nanoparticles are the most common embedded metal nanoparticles used in conjunction with polymers. This is because silver nanoparticles exhibit remarkable properties including catalytic activity, surface-enhanced Raman scattering activity, high electrical conductivity and antimicrobial activity. 

Thus vegetable oil-based polymer nanocomposites have considerable significance in the development of advanced polymeric materials, offering great improvement in performance characteristics without a large increase in cost. Nanotechnology may therefore carve out a unique niche of its own in the area of vegetable oil-based polymer nanocomposites. 

Three different types of nanomaterials, based on their dimensional characteristics, are generally used to prepare polymer nanocomposites. These include nanomaterials with only one dimension in the nanometre range (e.g. nano-clay), those with two dimensions in the nanometre scale (e.g. carbon nanotubes) and those that have all three dimensions in the nanometre scale (e.g. spherical silver nanoparticles), as stated earlier. Thus nanosize thin layered aluminosilicates or nanoclays, layer double hydroxide (LDH), a large number of nanoparticles of metals and their oxides, carbon nanotubes and cellulose nanofibres are used as nanomaterials in the preparation of vegetable oil-based polymer nanocomposites. 

The ultraviolet (UV) - visible spectrophotometer is another important tool in the characterisation of vegetable oil-based polymer nanocomposites and is particularly effective for metal nanocomposites. The formation of metal nanoparticles in the matrix can be easily detected by UV-visible spectroscopy. Every metal nanoparticle has its own characteristic surface plasmon resonance value. This band is attributed to the collective oscillation of electron gas in the nanoparticles, with a periodic change in the electronic density at the surface. Parameters such as particle size, shape and dielectric constant of the medium and surface adsorbed species determine the position and shape of the plasmon absorption. When the particles become significantly smaller than the mean free path of electrons in the bulk metal, the plasmon oscillation is dampened. The plasmon absorption peak shifts to a higher wavelength than expected with an increase in aggregation of the nanoparticles. The sharpness of the peak indicates the narrow size distribution. 

The desirable properties of polymer nanocomposites which are obtained by the incorporation of small amounts of nanomaterials make them of signihcant value to the scientihc community. Properties such as tensile strength, tensile modulus, thermal and barrier properties, flame retardancy and chemical resistance of vegetable oil-based polymer matrices are improved signihcantly without affecting the light weight characteristics and flexibility of the pristine polymer system. 

The flame-retardant characteristics of polymer nanocomposites are also found to be enhanced compared to the pristine system. This may be due to a significant reduction in the heat release rate and an increase of nonflammable char residue. The char creates a protective layer which impedes oxygen penetration and creates an insulating layer between the heat and the fuel. 

Explain the improvement in the thermal and flame retardant characteristics of pristine vegetable oil-based polymer by the formation of polymer nanocomposites. 

In the past decade, clay-based polymer nanocomposites have attracted considerable attention from the research field and in various applications. This is due to the capacity of clay to improve nanocomposite properties and the strong synergistic effects between the polymer and the silicate platelets on both a molecular and nanometric scale [2,3], Polymer-clay nanocomposites have several advantages (a) they are lighter in weight than the same polymers filled with other types of fillers (b) they have enhanced flame retardance and thermal stability and (c) they exhibit enhanced barrier properties. This chapter focuses on the polymer clay-based nanocomposites, their background, specific characteristics, synthesis, applications and advantages over the other composites. 

Carbon-based polymer nano composites represent an interesting type of advanced materials with structural characteristics that allow them to be applied in a variety of fields. Functionalization of carbon nanomaterials provides homogeneous dispersion and strong interfacial interaction when they are incorporated into polymer matrices. These features confer superior properties to the polymer nanocomposites. This chapter focuses on nanodiamonds, carbon nanotubes and graphene due to their importance as reinforcement fillers in polymer nanocomposites. The most common methods of synthesis and functionalization of these carbon nanomaterials are explained and different techniques of nanocomposite preparation are briefly described. The performance achieved in polymers by the introduction of carbon nanofillers in the mechanical and tribological properties is highlighted, and the hardness and scratching behavior of the nanocomposites are also discussed. 

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