Polymer continued dispersions

Polymer composite consisting of a polymer continuous phase and disperse phase domains of microscopic ceramic particles. 

After the molecular weight and composition of the block polymer were fixed at appropriate levels, mechanical blending was scaled-up to both larger and continuous dispersion mixers. An acceptable and reproducible product was made at all levels up to the highest output tried, e.g., 1000 lbs/hr. 

Multicomponent polymers systems such as polyblends, and block copolymers often exhibit phase separation in the solid state which results in one polymer component dispersed in a continuous phase of a second component. The morphological properties of these systems depend upon a number of factors such as the molar ratios of the components, the molecular weights, the thermal history of the system and, for solvent cast films, the solvent and drying conditions. 

Non-Aqueous Processes. Dispersions of composite particles in non-aqueous media (12) have been prepared. The particles were sterically stabilised to prevent flocculation and aggregation. This was achieved by physical absorption of amphipathic graft or block copolymer (13,14) or by covalent attachment of diluent-soluble oligomer or polymer chains (15) at the particle surface so that by definition different polymers were situated at the surface and in the bulk of the particles, even for single-polymer particles. Composite particles were prepared by slow addition of the second monomer which was fully miscible with the diluent phase, obviating a monomer droplet phase further monomer-soluble initiation and amphipathic graft stabiliser was included as appropriate so that the process comprised continued dispersion... 

Polymerization Results. Preliminary polymerization runs were conducted to evaluate the effect of Initiator concentration, temperature, and continuous-phase density on the rate of reaction as well as the ultimate molecular weight of the polymer. Continuous-phase density could be varied in two ways 1) by varying the pressure at constant temperature and ethane/propane ratio, and 2) by varying the ethane/propane ratio at constant temperature and pressure. In all of these polymerizations, the acrylamide ratio was 1.0, water was 3.5, and the total dispersed-phase volume fraction was 0.16. 

The more common situation, Illustrated in Fig. lb, is where the two polymers are immiscible but form a homogenous solution in a common solvent. In this case, film casting along the line C to D generates a variety of structures depending on the selected solvent (and its interaction parameters X o Xij), the chemical nature of the two polymers (X23) as well as on the kinetics of the process. Three phase-separated types of morphologies can result co-continuous, dispersed, and layered. 

Vibrational dispersion is, for vibrations of the same type, the variation of the relative phase of atomic displacements with their frequency. Although it is a well known effect in molecular spectroscopy it is not usually presented as such. Rather there is an emphasis on treating each vibration individually and the deep similarities between vibrations of the same type are often obscured. Dispersion in molecules is normally seen in its discrete form and the effect of continuous dispersion is only observed in the spectroscopy of polymers ( 10.1.1.1). The connection between the discrete and continuous forms is most easily seen by considering the vibrations of molecules composed of simple chemical motifs repeated several-fold. We have chosen to demonstrate this with the highest frequency vibrations in benzene, the stretches of the six C-H repeat units. 

The state of thermodynamic equilibrium (implying the formation of a single-phase blend of components) can rarely be reached due to the high viscosity of polymer composite systems. Polymer CM are most often dispersed systems whose composition varies with time and individual components may form phase areas of different sizes. One of their components (the polymer phase) is a continuous dispersed medium, i.e. a matrix, in which all other components are spread as a dispersion of spatially separated particles called a dispersed phase [31],... 

One method is to add a second polymer to the heat seal layer that melts at a higher temperature than the sealant it should also melt at a higher temperature than is expected to be used on the packaging equipment for sealing. If this polymer is dispersed in the heat seal polymer in tiny domains, it acts to disrupt the continuity of the heat seal and weaken the seal strength to the point where the seals can be peeled apart easily. 

Immiscible polymer blends normally have a sea-island stmcture, where one polymer is dispersed as (normally spherical) particles in the other polymer, which forms the matrix, or a co-continuous structure, where both polymers are equally distributed in the blend without one polymer forming a continuous phase. For the blends to have good mechanical properties, it is also important that there is good interaction between the different components in the blend. To ensure this, researchers have tried a variety of methods to compatibilize the polymers in blends. The most used method is to add a third polymer, which interacts well with the other two polymers, into the blend. Reactive blending is another well-used method, and recently, a lot of investigation went into the use of (especially clay) nanoparticles to improve the interaction between the polymer components by locating themselves on the interfaces between the polymers. 

Accordion polymers—Continued orientational and chemical stability, 139 synthesis by Knoevenagel condensation polymerization, 135-136 waveguide construction, 139-140 Aluminum metal electrode, deposition on polymer in LED, 411,412/ Aromatic amine-containing polymers dye-dispersed poly(N-vinylcarbazole), 387, 390-393... 

Two reaction loci are considered, the polymer-rich dispersed phase and the C02-rich continuous phase. A kinetic scheme typical of free-radical reactions and including initiation, propagation, terminations, and chain transfer to monomer and to polymer is applied to each phase. 

Molecular characteristics of syrrthetic polymers are never uniform. They always exhibit certain dispersity. Dispersity is a new term, coined by lUPAC, which should substitute the former term distribution. In fact all synthetic polymers represent mirlticomponent mixtures of macromolecirles, which differ in one or several molecular characteristics. With a rather few exceptions such as for example some polymer mixtures and polymer blends, dispersities in molecular characteristics of common polymers are continuous in nature. For example, the molar masses of macromolecules that form particular members of typical homologous series usually differ only in the molar mass of a single monomeric rmit The resulting total molar mass of polymers ranges from a minimirm, to a maximum value, while the latter may be several times higher than the minimum value. Therefore, the molecular characteristics are described with their average values or with the dispersity functions. Consequently, we have ... 

In immiscible polymer blends, one polymer is dispersed in the form of domains in the continuous phase of the other. The degree of dispersion depends upon the mixing ability of the polymers, which decreases with an increase in concentration of the other polymer in the blend. Therefore, the quantity of domains and the degree of dispersion in PVC/CPE blends determine the progress of the degradatimi. The evolved HCl partially lags in the bulk sample, due to inefficient diffusion and, consequentially, has a catalytic effect on dehydorchlorination at low level of dehydrochlorination, as well as on the secondary reactions of polyene residues (Mahmood and Quadeer 1994). 

Emulsion pol)m erization is a complex process in which the radical addition polymerization proceeds in a heterogeneous system. This process involves emulsification of the relatively hydrophobic monomer in water by an oil-in-water emulsifier, followed by the initiation reaction with either a water-soluble or an oil-soluble free radical initiator. At the end of the pol)nnerization, a milky fluid called "latex", "synthetic latex" or "pol)rmer dispersion" is obtained. Latex is defined as "colloidal dispersion of polymer particles in an aqueous medium". The pol)nner may be organic or inorganic. In general, latexes contain 40-60 % pol)nner solids and comprise a large population of polymer particles dispersed in the continuous aqueous phase (about lO particles per mL of latex). The particles are within the size range 10 nm to 1000 run in a diameter and are generally spherical. A typical of particle is composed of 1-10000 macromolecules, and each macromolecule contains about lOO-lO " monomer units [10-16]. 

Multiphase or multicomponent polymers can clearly be more complex structurally than single phase materials, for there is the distribution of the various phases to describe as well as their internal structure. Most polymer blends, block and graft copolymers and interpenetrating networks are multiphase systems. A major commercial set of multiphase polymer systems are the toughened, high impact or impact modified polymers. These are combinations of polymers with dispersed elastomer (rubber) particles in a continuous matrix. Most commonly the matrix is a glassy amorphous thermoplastic, but it can also be crystalline or a thermoset. The impact modified materials may be blends, block or graft copolymers or even all of these at once. 

The phase-separated morphology of a NSLC consists of a self-assembled polymer networic dispersed in die continuous liquid crystal (See Figure 3). NSLCs differ from both PDLC and H-PDLC materials, in that, die initial mixture contains less than 10% by weight of a reactive liquid crystalline monomer whereas, the initial mixture for PDLCs and H-PDLCs contains 20% to 60% reactive non-liquid crystalline monomer. NSLC are bi-stable in that once switched with an lied voltage from the reflective state to die transparent state or visa versa, the optical properties do not change wh the voltage upon removed. 

The preparation of high molecular weight, water soluble acrylamide-based flocculants as water continuous dispersions is described. This innovative method of manufacture eliminates many of the undesirable characteristics associated with the production and application of these flocculants as conventional water-in-oil emulsions or as dry powders. The monomers and their polymers, the role of the stabilizer polymer, particle characteristics, viscosity considerations, and the thermodynamic and physical stability of these polymer diversions is discussed. 

In order to overcome the difficulties associated with inverse emulsion and dry polymers, Nalco has become involved in the development and commercial practice of a unique technology for the manufacture of high molecular weight water soluble polymers based on acrylamide. This polymerization process permits the manufacture of these extremely useful polymers as water continuous dispersions. The polymer products are liquid, and so retain the virtues of ease and safety of handling, but they are manufactured in water instead of in a hydrocarbon and surfactant matrix. Thus, no oil or surfactants are released to the environment with the application of these polymers. The performance of these polymers in the various end use applications is equivalent to, or in some cases exceeds, that obtained with similar polymers produced in inverse emulsion or dry form. A discussion of this dispersion polymerization technology, the monomers and their polymers, the stabilizer polymers, particle characteristics, viscosity considerations and the thermodynamic and physical stability of the products constitutes the subject of this manuscript. 

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