Polymeric matrix particles

In recent decades, various inorganic materials have been investigated and identified as potential fillers for hybrid membrane preparation. The required features for the choice of the embedded phase are typically chemical adaptation for the dispersion in the polymeric matrix, particle shape and morphology, and suitable effects on the overall transport properties. 

It is precisely the loosening of a portion of polymer to which the authors of [47] attribute the observed decrease of viscosity when small quantities of filler are added. In their opinion, the filler particles added to the polymer melt tend to form a double shell (the inner one characterized by high density and a looser outer one) around themselves. The viscosity diminishes until so much filler is added that the entire polymer gets involved in the boundary layer. On further increase of filler content, the boundary layers on the new particles will be formed on account of the already loosened regions of the polymeric matrix. Finally, the layers on all particles become dense and the viscosity rises sharply after that the particle with adsorbed polymer will exhibit the usual hydrodynamic drag. 

In a polymeric matrix the filler, even if present in minimum quantities) is always more or less agglomerated [212]. Microscopic studies have confirmed the existence of two types of primary structures in composites [213], i.e., filler aggregates with particles bound together firmly enough, and agglomerates — systems of weakly interrelated aggregates. 

By the term particulate composites we are referring to composites reinforced with particles having dimensions of the same order of magnitude. Particulate composites are produced from a polymeric matrix, into which a suitable metal powder has been dispersed, and exhibit highly improved mechanical properties, better electrical and thermal conductivity than either phase, lower thermal expansivity, and improved dimensional stability and behaviour at elevated temperatures. 

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. 

Figure 6. A hologram of two gold particles embedded in a polymeric matrix. The image does not include the full hologram only the part of the original TEM image including the particles has been selected for an easier visualization of the interference fringes. (Thanks to Prof. B. Corain and Dr. P. Centomo (University of Padova, Italy) for providing the specimen and to Dr. P. G. Merli and to Dr. L. Ortolani (IMM-CNR Bologna, Italy) for the use of the FEI FEG-TEM.)...

The results of the catalyst testing are shown in Table 3. The data listed in the table show, that on a per proton basis, catalyst A (based on 7% DVB) has higher activity as compared to resin materials, crosslinked with 12% DVB. This result is in accord with the finding by Petrus et al.,3 that at temperatures higher than 120 °C the hydration is under into particle diffusion limitation and as such, a more flexible polymeric matrix will provide better access to the acidic sites. On a dry weight basis, catalyst D showed the highest activity, which correlates well with the high acid site density found for this resin (Table 2). On a catalyst volume basis, catalyst A has the best performance characteristics followed by catalyst D. 

Based on these preliminary investigations, SEM-EDS was used to identify the particles embedded in the sheets. A particle was isolated from the extruded plastic sheeting and analyzed. Figure 40 shows an SEM micrograph at 14,500 x magnification of the particle studied. This specimen is quite small, on the order of 10 pm in diameter. The EDS results are summarized in Table 11 for both this particle and for the polymeric matrix material from which it was harvested. 

As expected, the EDS data set indicates that the polymeric matrix material (the PE-PP blend) is composed only of carbon (hydrogen is not detectable by this method). The particle, however, appears to be composed mainly of aluminum and oxygen along with small amounts of copper. The ratio of aluminum to oxygen is consistent with the chemical formula for aluminum oxide (A1203). The SEM-EDS results are consistent with aluminum oxide and traces of copper as the primary constituents of the particulate contamination. (Al2O3.3H20 is a commonly used fire-retardant additive in polymeric products.)... 

In conclusion, the particles from the extruder breaker plate were identified as being polyetherimide. The particles in the polymeric matrix, however, appear to be inorganic in nature, containing aluminum and oxygen, as aluminum oxide, with traces of copper. 

Table 11 Summary of EDS results for the polymeric matrix and the particle harvested from the extruded plastic sheeting...

The original polymeric latex particles still are widely used for separation and detection. Polymers provide a matrix that can be swollen for embedding other molecules in their core, such as organic dyes or fluorescent molecules. Even nanoparticle quantum dots can be incorporated into larger latex particles to form highly fluorescent composite microparticles. 

The insertion of dried fern in a polymeric matrix avoids the fern particles mechanical degrading and permits the bioaccumulating material regeneration and it is reworking, determining the effectiveness of this advanced cleaning wastewater. 

The mechanical stability and morphology of the resulting membrane depended on the polymeric matrix and the presence of additives such as plasticisers or pore forming agents, e.g. PEG, as well as on the MIP particle size and concentration (Fig. 19) [258, 261, 262],... 

The immobilization of enzymes may introduce a new problem which is absent in free soluble enzymes. It is the mass-transfer resistance due to the large particle size of immobilized enzyme or due to the inclusion of enzymes in polymeric matrix. If we follow the hypothetical path of a substrate from the liquid to the reaction site in an immobilized enzyme, it can be divided into several steps (Figure 3.2) (1) transfer from the bulk liquid to a relatively unmixed liquid layer surrounding the immobilized enzyme (2) diffusion through the relatively unmixed liquid layer and (3) diffusion from the surface of the particle to the active site of the enzyme in an inert support. Steps... 

Besides, as can be seen from the cited data, this value is almost one and the same irrespective of the nature of M/SC so that it is determined by only structure and properties of a polymeric matrix. In this connection it should draw attention to the fact that according to spectral data [80] the d value of Ag nanocrystals in films Ag-CNPPX is much less than that of Ag nanocrystals in films Ag-PPX and Ag-CIPPX. As was specified above, it is possible to expect essential interaction between Ag particles with strongly polar CN substituents of PPX that hinders the growth of Ag nanocrystals. 

At co-deposition of dielectric and M/SC the structure of a nanocomposite film depends on a relationship between the rate of formation of M/SC particles and the rate of making of a solid dielectric matrix. Models of such deposition are discussed. The special attention is paid to new low-temperature processes of nucleating and growth of nanoparticles in a solid polymeric matrix containing the inclusions of... 

A method of incorporating simultaneously hybrid fillers of CB and MWNTs into a polymeric matrix has also been used to enhance the electrical conductivity of composites because the CB particles link the gaps between the unconnected MWNTs thus improving the formation of connected structures (51,52). In fact the synergistic effects arising between the two different fillers improve the dispersion of MWNTs in the polymer matrix. 

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