Latex concept

Polymer Carbon Nanotube Composites Tbe Polymer Latex Concept Nadia Grossiord, Marie Claire Hermant, and Cor Koning Copyright 2012 Pan Stanford Publishing Pte. Ltd. 

To sum up, a proof of principle was obtained that conductive, industrially relevant CNT/PPO/PS nanocomposites can successfully be prepared by two main routes based on latex technology. The first one consists of directly mixing SDS-CNT dispersions with a PPO/PS latex. The second one is based on the use of a CNT/PS masterbatch, subsequently mixed with PPO/PS by extrusion in the melt. This second approach is particularly interesting since it opens the possibility to extend the range of application of the latex concept to the [commercial] production of nanocomposites based on blends that cannot [easily] be obtained in a latex form. 

A thermoplastic EPDM/iPP vulcanizate consists of a continuous and thermoplastic iPP phase, which forms the minority of this blend (ca. 20 wt%), and a cross-linked, oil-extended, dispersed EPDM phase (ca. 80 wt%). The discrete EPDM phase consists of submicron or several microns size particles. Within the discontinuous EPDM/ iPP vulcanizate morphology, the cross-linked EPDM phases act as excluded volumes into which carbon nanotubes can hardly penetrate during melt-blending, or after performing the four steps of the latex concept, described in depth in earlier chapters of this book. 

The results on MWCNT-polymer nanocomposites reported in this chapter demonstrate the versatility of the latex concept to prepare nanocomposites with a broad range of "home-made" or industrially manufactured polymers, namely, amorphous, semi-crystalline, and blended polymer matrixes. Note that blending can further be done in very different fashions, i.e., in situ, while the emulsion polymerization proceeds, by mixing of two different polymer latexes synthesized independently from each other, or by a "masterbatch approach." This study confirms that the CNT-polymer interactions are of major importance to influence the percolation behavior of the nanocomposites, as well as the viscosity, morphology, and the intrinsic conductivity of the polymer matrix. 

Poiymer Carbon Nanotube Composites The Pol3rmer Latex Concept... 

Chemically related database searches can be used to estabhsh concepts and patentable ideas. For instance, searches have identified researchers using particular monomers in a potentially patentable latex formulation found precedents for a polymeric emulsifier summarized pubHcations of people being considered as consultants, expert witnesses, employees or speakers to an industrial group and provided market description information for a new pigment manufacturing firm to identify target markets. 

From surfactant molecules it is known that the repeated vertical dipping of a substrate through a floating monolayer of these molecules leads to the formation of an LB multilayer on the substrate. In principle, the same procedure should also allow the preparation of multilayers of latex particles. In Figure 8b, the preparation of a particle bilayer is schematically indicated multiple repetition should result in the formation of an LB multilayer of particles. However, if one tries to realize this concept, one immediately gets into difficulties, because the contact of the particles with the underlying substrate is very poor, and the already deposited particle layer tends to detach from the surface when the substrate is dipped into... 

The reaction described in this example is carried out in miniemulsion.Miniemulsions are dispersions of critically stabilized oil droplets with a size between 50 and 500 nm prepared by shearing a system containing oil, water,a surfactant and a hydrophobe. In contrast to the classical emulsion polymerization (see 5ect. 2.2.4.2), here the polymerization starts and proceeds directly within the preformed micellar "nanoreactors" (= monomer droplets).This means that the droplets have to become the primary locus of the nucleation of the polymer reaction. With the concept of "nanoreactors" one can take advantage of a potential thermodynamic control for the design of nanoparticles. Polymerizations in such miniemulsions, when carefully prepared, result in latex particles which have about the same size as the initial droplets.The polymerization of miniemulsions extends the possibilities of the widely applied emulsion polymerization and provides advantages with respect to copolymerization reactions of monomers with different polarity, incorporation of hydrophobic materials, or with respect to the stability of the formed latexes. 

Water-based barrier dressings are attractive for application to injured tissue because of the biocompatibility between water and tissue. The concept of a water-based dressing initially consisted of latex-type particles of polymer suspended in an aqueous emulsion. The emulsion would be liquid applied to the tissue, water would evaporate and the particles would coalesce to form a continuous film. The rate of evaporation of water is slow compared to solvents as ethanol that was recognized to be a limitation to application time (time to place on the tissue and harden). The following description of miniemulsions (miniEP) involves a batch type... 

With the concept of nanoreactors one can take advantage of an additional mode control for the design of nanoparticles where both thermodynamic aspects as well as shear history enter the particle size and the inner structure of the latexes or hybrid particles. The polymerization in such nanoreactors takes place in a highly parallel fashion, i.e., the synthesis is performed in 1018-102° nanocompartments per liter that are separated from each other by a continuous phase. In miniemulsion polymerization, the principle of small nanoreactors is realized as demonstrated in Fig. 1. 

In addition, it is worth remembering that the sequence or chain length of ODN has no influence on the overall amount of adsorbed ODN (in mg m 2) on cationic colloidal polymer particles [24]. This underlines the concept that ODN are mainly adsorbed via attractive electrostatic interaction in the case of oppositely charged latexes and via hydrophobic or staking interactions when negatively hydrophobic latexes are used. 

The theory and the experimental data from this study demonstrates that in a train of CSTRs, essentially all of the particles form in the first reactor. Therefore, it is possible to maximize the monomer conversion in the latex leaving the first reactor by keeping the temperature and the residence time at the first reactor as low as possible in order to produce the maximiun number of polymer particles and so increase the rate of polymerization in the succeeding stages. This is the so-called pre-reactor concept. 

The major difficulty in the development of FFF methodologies and instrumentations is linked to the complexity of correlating elution mode hypotheses (Hyperlayer) with experimental proofs, which depends essentially upon physical properties of the cellular material, such as size, density, shape, rigidity, and cellular viscosity, which are of greatest interest if the physical point of view is considered. This point of view is historical and is linked to the wide experience of FFF practitioners with latex or silica, micron-sized species, or starch granules, or others. There are some examples dealing with cellular materials (e.g., red blood cells or yeast) where elution is correlated with the abovedescribed physical properties in these cases, cellulomics concepts are relatively simple. 

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