Interaction particles/polymer matrix

Because the commercially available nanoparticles stick to each other and form large agglomerates, simple addition of these agglomerated nanoparticles into polymers would result in composites with properties even worse than the unfilled version. Therefore, surface modification of nanoparticles has to be made in advance to decrease par tides/par tides interaction and increase particles/polymer matrix interaction. 

PVDF-Ti02 composite hollow fibers exhibit superior hydrophilicity and mechanical properties as compared with the pristine PVDF hollow fibers. The composite hollow fibers prepared through the Ti02 sol-gel technique were observed to have better particle dispersion and interaction between the particle-polymer matrixes. Yuliwati et al. [94] observed that the addition of a small amount (1.95 wt%) of TiOj can greatly improve the performance of PVDF-Ti02composite hollow fibers. The aforementioned composite hollow fibers possess smaller pore sizes coupled with higher hydrophilicity and porosity. 

An important consideration is the effect of filler and its degree of interaction with the polymer matrix. Under strain, a weak bond at the binder-filler interface often leads to dewetting of the binder from the solid particles to formation of voids and deterioration of mechanical properties. The primary objective is, therefore, to enhance the particle-matrix interaction or increase debond fracture energy. A most desirable property is a narrow gap between the maximum (e ) and ultimate elongation ch) on the stress-strain curve. The ratio, e , eh, may be considered as the interface efficiency, a ratio of unity implying perfect efficiency at the interfacial Junction. 

Moreover, the interaction of the surface of the fillter with the matrix is usually a procedure much more complicated than a simple mechanical effect. The presence of a filler actually restricts the segmental and molecular mobility of the polymeric matrix, as adsorption-interaction in polymer surface-layers into filler-particles occurs. It is then obvious that, under these conditions, the quality of adhesion can hardly be quantified and a more thorough investigation is necessary. 

To improve the adhesion and interaction in the zeolite/polymer interface, the surface of the zeolites can also be sized (or primed ) by coating the zeolite with an ultrathin layer of the matrix polymer or a different polymer. Sizing of the zeolite particles prior to dispersion in the polymer matrix reduced the stress at the... 

This chapter focuses its attention on the discussion of the most relevant questions of interfacial adhesion and its modification in particulate filled polymers. However, because of the reasons mentioned in the previous paragraph, the four factors determining the properties of particulate filled polymers will be discussed in the first section. Interactions can be divided into two groups, parti-cle/particle and matrix/filler interactions. The first is often neglected although it may determine the properties of the composite and often the only reason for surface modification is to hinder its occurrence. Similarly important, but a very contradictory question is the formation and properties of the interphase a separate section will address this question. The importance of interfacial adhesion... 

As was mentioned in the previous section two types of interactions must be considered in particulate filled polymers particle/particle and matrix/filler interaction. The first is often neglected even by compounders, in spite of the fact that its presence may cause composite properties to deteriorate significantly especially under the effect of dynamic loading conditions [18]. Many attempts have been made to change both interactions by the surface treatment of the filler, but the desired effect is often not achieved due to improper use of incorrect ideas. 

In semi-crystalline polymers the interaction of the matrix and the tiller changes both the structure and the crystallinity of the interphase. The changes induced by the interaction in bulk properties are reflected by increased nucleation or by the formation of a transcrystalline layer on the surface of anisotropic particles [48]. The structure of the interphase, however, differs drastically from that of the matrix polymer [49,50]. Because of the preferred adsorption of large molecules, the dimensions of crystalline units can change, and usually decrease. Preferential adsorption of large molecules has also been proved by GPC measurements after separation of adsorbed and non-attached molecules of the matrix [49,50]. Decreased mobility of the chains affects also the kinetics of crystallization. Kinetic hindrance leads to the development of small, imperfect crystallites, forming a crystalline phase of low heat of fusion [51]. 

The considered works concern systems where the substrate plays an active role in catalytic reactions with participation of M nanoparticles located on its surface. This role shows itself not only in modification of the catalytic properties of particles by a charge transfer between them and a substrate, but also in formation of triple complexes, in which the reacting molecule is connected both with a substrate and with an M nanoparticle [114], Meanwhile, specific increased catalytic activity of M nanoparticles has been found out also in cryochemically synthesized nanocomposite PPX films, in which nonpolar polymer matrix only weakly interacts with M nanoparticles. 

We have already seen that photoactive clusters, e.g. CdS, can be introduced into vesicles and BLMs (Sect. 5.2 and 5.3). Similar support interactions are possible with both inorganic and organic polymeric supports. Photoactive colloidal semiconductor clusters can be introduced, for example, into cellulose [164], porous Vycor [165], zeolites [166], or ion exchange resins [167]. The polymer matrix can thus influence the efficiencies of photoinduced electron transfer by controlling access to the included photocatalyst or by limiting the size of the catalytic particle in parallel to the effects observed in polymerized vesicles. As in bilayer systems,... 

Fillers are added to polymers either to improve the polymer properties or to reduce the price of the compound. The properties of filled polymers are heavily influenced by the interaction between particles and polymers as well as by particle size, particle size distribution, and the homogeneity of the particle distribution. The smaller the particles and the more homogenous their distribution in the polymer matrix, the better in general the properties of the compound. Therefore, dispersion plays a key role. 

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