Nanofiller contents

The authors [1] studied kinetics of poly (amic acid) (PAA) solid-state imidization both in the presence of nanofiller (layered silicate Na+-montmorillonite) and without it. It was found, that temperature imidization 1] raising in range 423-523 K and nanofiller contents Wc increase in range 0-7 phr result to essential imidization kinetics changes expressed by two aspects by essential increase of reaction rate (reaction rate constant of first order k increases about on two order) and by raising of conversion (imidization) limiting degree Q im from about 0,25 for imidization reaction without filler at 7 i=423 K up to 1,0 at Na -montmorillonite content 7... 

Up to now we considered pol5meric fiiactals behavior in Euclidean spaces only (for the most often realized in practice case fractals structure formation can occur in fractal spaces as well (fractal lattices in case of computer simulation), that influences essentially on polymeric fractals dimension value. This problem represents not only purely theoretical interest, but gives important practical applications. So, in case of polymer composites it has been shown [45] that particles (aggregates of particles) of filler form bulk network, having fractal dimension, changing within the wide enough limits. In its turn, this network defines composite polymer matrix structure, characterized by its fractal dimension polymer material properties. And on the contrary, the absence in particulate-filled polymer nanocomposites of such network results in polymer matrix structure invariability at nanofiller contents variation and its fractal dimension remains constant and equal to this parameter for matrix polymer [46]. 

FIGURE 13 The electron micrographs of chips of nanocomposites PP/CaCOj with nanofiller contents 1 (a) and 4 (b) mass. %. 

Let us consider in the conclusion of the present section melt viscosity behavior as a function of nanofiller contents for nanocomposites pol5q)ropylene/carbon nanotubes (PP/CNT), studied in Refs. [55, 76]. In Figs. 18 and 19 the dependences of the ratios GJG and on nanofiller contents and the parameters and (l+

experimental data and behavior, predicted by the Eqs. (38) and (39), is observed again. In Fig. 20, the dependence of MFI on nanofiller mass contents IF for nanocomposites PP/CNT, calculated according to the Eq. (43), is adduced. As one can see, the qualitative discrepancy between theoretical calculation (curve 1) and experimental data (points) is observed. If the Eq. (43) assiunes melt viscosity increasing (MFI reduction) at IF growth, then the experimental data discovers opposite tendency (MFI >MFI ). 

Merkel et al. [2002, 2003] carried out studies of gas and vapor permeability and PALS free volume in a poly(4-methyl-2-pentyne) (PMP)/fumed silica (FS) nanocomposite. It was observed that gas and vapor uptake remained essentially unaltered in nanocomposites containing up to 40 wt% FS, whereas penetrant diffusivity increased systematically with the spherical nanofiller content. The increased diffusivity dictates a corresponding increase in permeability, and it was further established that the permeability of large penetrants was enhanced more than that of small penetrants. PALS analysis indicated two o-Ps annihilation components, interpreted as indicative of a bimodal distribution of free-volume nanoholes. The shorter o-Ps lifetime remained unchanged at a value T3 2.3 to 2.6 ns, with an increase in filler content. In contrast, the longer lifetime, T4, attributed to large, possibly interconnected nanoholes, increased substantially from 7.6 ns to 9.5 ns as FS content increased up to 40 wt%. 

The increase in the tack energy above PBA is given as a function of the nanofiller content. Figure and legend are taken from [109]... 

Maitra et al. determined the hardness of PVA with 0.6 wt% oxidized NDs using nanoindentation and the Oliver-Pharr method addition of nanofiller enhanced the hardness 80% of the neat polymer [48]. Hardness and modulus of FG/epoxy composites increased steadily with the incorporation of up to 1.5 wt% nanofiller. An increased amount of agglomerates was obtained at a loading of 2 wt% amino FGs as observed by the dramatic drop in the modulus this behavior also affected the nanocomposite hardness, as depicted in Figure 10.20 [113], The microhardness of amino FGs/PI nanocomposites showed a dependence on nanofiller content, although the dependence diminishes at loadings > 1 wt%, where the effect starts to saturate [115]. Covalently bonded amino NDs/epoxy composites showed a 200 times higher hardness compared to the neat... 

Peroxide cross-linked poly(propylene sebacate), synthesized from biorenewable resources, exhibited a at about 50 °C serving as in the SM cycle. The value of could be tuned by the peroxide cross-linking and boehmite nanofillers content yielding a temperature interval between 37 and 51 °C, which is close to body temperature. Interestingly, the boehmite nanoplatelets contributed to a fast in vitro degradation of this polymer [25]. 

AD = D -d° is plotted on the graph as a function of nanofiller contents for four imidization temperatures. As it follows from this Figure plots, the AZ) value decreases... 

The temperature irrudization T. raising within the range 423-523 K and the nanofiller contents IF increase within the range 0-7 mass% results to essential imidization kinetics change expressed by two aspects by an essential increase of reaction rate (re-... 

For the solution of the first from the indicated problems the statistical segments number in one nano cluster j and its variation at nanofiller contents change should be estimated. The parameter calculation consistency includes the following stages. At first the nanocomposite stmcture fractal dimension is calculated according to the equation [12] ... 

Hence, this chapter results demonstrated common reinforcement mechanism of natural and artificial (filled with inorganic nanofiller) polymer nanocomposites. The statistical segments number per one nanocluster reduction at nanofiller contents growth is such a mechanism on suprasegmental level. The indicated effect physical foundation is the densely packed interfacial regions formation in artificial nanocomposites. 

As it has been shown above (see the Eqs. (15.7) and (15.15)), the nanocluster relative fraction increasing results to polymers elasticity modulus enhancement similarly to nanofiller contents enhancement in artificial nanocomposites. Therefore, the necessity of quantitative description and subsequent comparison of reinforcement degree for the two indicated above nanocomposites classes appears. The authors of Ref. [58, 59] fulfilled the comparative analysis of reinforcement degree by nanoclusters and by layered silicate (organoclay) for polyarylate and nanocomposite epoxy poly-mer/Na" —montmorillonite [60], accordingly. 

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