Homopolymer latices

Keywords Copolymers, differential scanning calorimeter, emulsion homopolymers, latexes, oligomeric stabilizator, polymerization... 

Latexes—These are dispersions of homopolymers and copolymers in water that are produced by anionic emulsion polymerization and contain 50% solids. Particle size is low (0.2 ym) as is viscosity (20-30 centlpoises). To produce film forming properties, homopolymer latexes must be plasticized. They are supplied either with or without plasticizer. Certain copolymer latexes such as those with acrylates are self-plasticized and do... 

However, the main focus of the miniemulsion technique lies in the formation of polymeric nanoparticles. Whereas conventional emulsion polymerization can be applied to the formulation of homopolymer latexes by radical polymerization, the generation of copolymer or functional nanoparticles is restricted with this technique,... 

Method Latex A (PVC copolymer) Latex B (PVC homopolymer) Latex C (aciylic copolymer)... 

Non-radiative direct energy transfer (DET) is the transfer of the exited state energy from a donor molecule to an acceptor molecule. This transfer occurs without the appearance of a photon, and is primarily a result of dipole-dipole interactions between the donor and acceptor. DET between phenanthrene and anthracene chromophores has been successfully employed to investigate the morphologies of PMMA and PS labelled homopolymer latex particles prepared by seeded emulsion polymerization, as well as PMMA/PS and PS/PMMA composite particles [85]. The results tend to confirm the existence of a core-shell structure of the latex particles, but more important, provide deeper insights into the interfacial structures in the particles. There is a limitation in the quantitative interpretation of the data due to the overall extent of energy transfer which is still small, even when there is substantial mixing nevertheless, trends are apparent. 

In many cases latex products are composed of more than one monomer. In copolymerisation two or more monomers are built-in into the polymer chains. The copolymer chains are produced by simultaneous polymerisation of two or more monomers in emulsion. Emulsion copolymerisation allows the production of materials with properties which cannot be obtained by latex products consisting of one monomer, that is, homopolymer latexes, or by blending homopolymers. The properties of the materials required are usually dictated by the market. Nowadays, most of the material properties are achieved by combination of more than two monomers in the copolymer product. Typical industrial emulsion polymerisation formulations are mixtures of monomers giving hard polymers, and monomers leading to soft polymers. Styrene and methyl methacrylate are examples of monomers giving hard polymers, that is, polymers with a high glass transition temperature, Tg. Soft polymers, that is, polymers with a low Tg, are, for example, formed from -butyl acrylate. The industrial emulsion polymerisation formulations also contain small amounts of functional monomers such as acrylic and methacrylic acid to impart improved or special characteristics to the latex product. Note that the colloidal stability of the latex product can be seriously improved by acrylic and methacrylic acid. Furthermore, some applications may demand for the addition of other specialty monomers that make the kinetics of the copolymerisation even more complex. 

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

The molecular weight of the polymers is controlled by temperature (for the homopolymer), or by the addition of organic acid anhydrides and acid hahdes (37). Although most of the product is made in the first reactor, the background monomer continues to react in a second reactor which is placed in series with the first. When the reaction is complete, a hindered phenoHc or metal antioxidant is added to improve shelf life and processibiUty. The catalyst is deactivated during steam coagulation, which also removes solvent and unreacted monomer. The cmmbs of water-swoUen product are dried and pressed into bale form. This is the only form in which the mbber is commercially available. The mbber may be converted into a latex form, but this has not found commercial appHcation (38). 

Since there was no experimental data available for the copolymer case, the copolymer model was run as a homopolymer one by setting one of the monomer inputs equal to zero. In this way one could test two extreme cases and see if there were any flaws in the model s logic. The results for a batch latex reactor are shown in Figure 5a. 

Abstract Emulsion homopolymers and copolymers (latexes) are widely used in architectural interior and exterior paints, adhesives, and textile industries. Colloidal stabihzators in the emulsion polymerization strongly affect not only the colloidal properties of latexes but also the fdm and mechanical properties, in general. Additionally, the properties of polymer/copolymer latexes depend on the copolymer composition, polymer morphology, initiator, polymerization medium and colloidal characteristics of copolymer particles. 

The stabilizing of aqueous latexes succeeded by using emulsifiers (anionic, nonionic) and/or their mixture, steric stabilizators (polyvinyl alcohol (PVOH), hydroxyethyl cellulose, polyethylene glycol, new protective colloids etc.), and polymerizable surfaces active agents, in general. Vinyl acetate (VAc) emulsion homopolymers and copolymers (latexes) are widely used as binders in water-based interior and exterior architectural paints, coatings, and adhesives, since they have higher mechanical and water resistance properties than the homopolymers of both monomers [2, 4, 7]. 

MMA is also used extensively as a copolymer with acrylates in latex paints and as a homopolymer in lacquers, since its transparent,... 

Under suitable conditions a reasonably stable latex may be formed (/). Although many of the factors relating to polymerization rate, molecular weight and particle size in emulsion have been studied [reference (134) is an example] the literature on homopolymers is by no means as extensive as that pertaining to copolymers. Attempts to prepare bead homopolymers have not been very successful. 

The butadiene and butadiene-acrylic monomer systems polymerize when irradiated on PVC or vinyl chloride copolymer latex. The structure of the polymer obtained may be grafted if it can be proved that the copolymer properties are different from the blend properties. To elucidate the structure we studied a copolymer obtained by polymerizing butadiene-acrylonitrile on a PVC homopolymer lattice. Owing to practical reasons and to exclude the secondary effect of catalytic residues we used y radiation. However, we shall observe in a particular case the properties of peroxide-initiated graft copolymer. 

Particle-Size Determination Particle-size of the cleaned1 latexes were determined using transmission electron microscopy after freeze-drying the samples and counting the particles with a Quantimet image analyzer. The number average particle diameters ( n) of the homopolymer, the 85/15 VA/BA and 70/30 VA/BA latexes were found to be 0.Q57/ m, 0.062/<.m and 0.073 m, respectively. 

It is well known (3,5,6) that sodium lauryl sulfate interacts with some polymers such as polyvinyl acetate causing solubilization of the insoluble polymer leading to an increase in viscosity. In Figure 3, viscosity of the homopolymer and 70/30 VA/BA at various NaLS/polymer ratio is shown. It is seen that the viscosity of the 2% latex dispersion increases with increase in NaLS/polymer ratio. Similar visoosity data for the 85/15 VA/BA was intermediate between the homopolymer and 70/30 VA/BA latexes. Surfactants that showed a normal saturation type adsorption behavior did not show any significant visoosity increase of the latex. 

Polarity of Vinyl Acrylic Latex and Surfactant Adsorption Contact angle measurements, dispersion and polar contribution to latex film surface tension and polarity of polymer calculated according to the method of Kaelble (10) of the three latex films are whown in Table V. It is seen that the polarity of the latex film decreases with increase in butyl acrylate content of the vinyl acrylic co-polymer. The polarity of the 70/30 (VA/BA) latex is very similar to that of the polybutyl acrylate homopolymer estimated to be about 0.21 (1). ... 

The interaction parameter, as expected, decreases with increase in polarity of the latex surface (12). It shows that at saturation adsorption, the extent of interaction of Igepal CO-630 with the PVAC homopolymer and the two VA/BA co-polymer latexes is 29%, 49%, and 57% respectively of the theoretical limit corresponding to a close packed monolayer adsorption. 

Figure 8 shows an example for application of this technique in the higher density range around 1.2 g cm 3. The gradient system consists of mixtures of HpO and D2O with glycerol and the latex under investigation is a latex of poly(vinyl acetate). The particle density and consequently the chemical composition is uniform, as it is expected for homopolymers. The experiment needs 40 min. 

The copolymer and acrylic homopolymer and copolymer latexes required for the blend systems to correspond compositionally to the two-stage latexes were prepared by a batch charged process as outlined in Table XIII. 

The particle size information for the latexes selected for structural characterization is shown in Table XIV. The homopolymer polystyrene seed latex was used to prepare the two-stage... 

The thermal transitions obtained for the p-St and p-BA homopolymers, and for the blend of these two homopolymers, are the anticipated transitions. The St/BA (65/35) copolymer exhibits a single transition at 33°C which is in the temperature region expected for that copolymer composition. The 65//35 (St//BA) two-stage latex exhibits the p-St and p-BA transitions in addition to a transition in the corresponding copolymer range. This intermediate transition was also observed when a mixture of 98 parts n-butyl acrylate and 2 parts methacrylic acid was used as the second stage composition or if AIBN was used as the second stage initiator. A tentative interpretation is that this transition is... 

A number of plants and some trees contain a white, milky liquid that is released when the stem or bark is cut. The liquid is called a latex from the Latin meaning liquid. Common sources include dandelions, milkweed, goldenrod, and potted rubber plants. Rubber trees, from which substantial quantities of latex can be harvested, grow in some tropical areas of the world. A major constituent of this latex is a homopolymer of isoprene (2-methyl-1,3-butadiene), called polyisoprene. Polyisoprene, as well as a number of other elastomers, has a carbon-carbon double bond in every repeat unit. The properties of polyisoprene are the result of the presence of these double bonds. Just as stereochemistry plays a critical role in both proteins and polysaccharides, we will see its importance here. 

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