Polyaddition polymerization

Chemicals for Water Shutoff In Situ Polymerization, Polyaddition, and Condensation... 

The method of migration polymerization (polyaddition reaction) finds extensive application in the production of silicon-, germanium- and tin-containing hetero-organic polymers 97). 

Table 2.4. Synthesis of macromolecules by step growth addition polymerization (polyaddition)...

If the equilibrium constant K has a value between 1 and 10, less than a thousandth of the total amount of water formed in the reaction mixture is sufficient to prevent the formation of really high-molecular-weight condensation polymers. Hence it follows that it is extremely important to remove as completely as possible the low-molecular-weight reaction products, for example, water, eliminated during a polycondensation. In principle, these equilibriums are also known in stepwise addition polymerizations (polyaddition) like the back-reactions of urethane groups. Since they mostly occur at higher temperatures only, they can be neglected. 

Various kinds of polymerization, polyaddition, substitution and polycondensation reactions of monomers bearing stabilizing moieties have been involved. Almost every kind of synthetical approach has been tested. However, only some of them are of practical interest Examples of monomers and/or of the respective ma-cromolecular systems proposed as stabilizers were selected from many literature data to show the diversity of structures. Only representative references are reported. 

Chemical Drying. Chemically drying paints contain binder components that react together on drying to form cross-linked macromolecules. These binder components have a relatively low molecular mass, so that their solutions can have a high solids content and a low viscosity. In some cases, solvent-free liquid paints are possible. Chemical drying can occur by polymerization, polyaddition, or polycondensation. 

Miniemulsion is a special class of emulsion that is stabilized against coalescence by a surfactant and Ostwald ripening by an osmotic pressure agent, or costabilizer. Compared with conventional emulsion polymerization process, the miniemulsion polymerization process allows all types of monomers to be used in the formation of nanoparticles or nanocapsules, including those not miscible with the continuous phase. Each miniemulsion droplet can indeed be treated as a nanoreactor, and the colloidal stability of the miniemulsion ensures a perfect copy from the droplets to the final product. The versatility of polymerization process makes it possible to prepare nanocapsules with various types of core materials, such as hydrophilic or hydrophobic, liquid or solid, organic or inorganic materials. Different techniques can be used to initiate the capsule wall formation, such as radical, ionic polymerization, polyaddition, polycondensation, or phase separation from preformed polymers. 

The aim of this chapter is to describe the possibilities offered by the miniemulsion process for performing chain polymerization, polyaddition, polycondensation, and modifications of polymers, and to outline the current trends in this field of research. Whilst the different polymerization types performed in miniemulsion are discussed in detail, descriptions of so-called secondary or artificial miniemulsions (i.e., miniemulsions with a preformed polymer) will not be included at this point... 

Adhesives and sealants are manufactured from a variety of polymers. Their selection and their combinations used impact solvent selection. Most solvent systems are designed to optimize the solubility of the primary polymer. Adhesives can be divided into ones which bond by chemical reaction and ones which bond due to physical processes. Chemically reactive adhesives are further divided into three more categories for those that bond through polymerization, polyaddition, or polycondensation. Physically bonding adhesives include pressure sensitive and contact adhesives, melt, or solution adhesives, and plastisols. Polymerization adhesives are composed of cyanoacrylates (no solvents), anaerobic adhesives (do not contain solvents but require primers for plastics and some metals which are solutions of copper naphthenate), UV-curable adhesives (solvent-free compositions of polyurethanes and epoxy), rubber modified adhesives (variety solvents discussed below). 

It is clearly a truism that for reducing the fire risk in the applications of plastics, their flammability should be diminished. This is achieved either by reactive flame-retardants incorporated during the preparation (polymerization, polyaddition, polycondensation) of the polymer or by additive flame-retardants admixed in the course of plastics processing. The flammability of plastics is sometimes reduced by surface protection. The most recent methods of reducing flammability are the modification of the macromolecular structure and the development of thermally resistant polymers (high-temperature plastics). 

Reactive flame-retardants are introduced into the monomer mixture during or before the polymer production (polymerization, polyaddition, or polycondenzation). The flame-retardant monomer of appropriate functionality contains the retardant-effective element(s) and is incorporated into the macromolecular structure. The superiority of reactive flame-retardants lies in their long-lasting efficiency which is quite high even at low percentages. As a shortcoming, however, they alter the original molecular structure (and hence alter the properties of the polymer) in fact, essentially new materials may be formed. In addition, they are strictly specific and their selection requires much care. 

Stepwise addition polymerizations (polyaddition) or condensation polymerizations (polycondensation) are possible polyreacticais for the first step. The two latter combinations attained interest in the technical synthesis of polyimides and polybenzimidazoles. 

Before setting, reactive adhesives consist predominantly of reactive low molecular mass monomers and/or oligomers that, during curing, are converted by chemical reactions into high molecular mass, often three-dimensionally cross-linked polymers. Reactive adhesives can be divided into polymerization, polyaddition, and polycondensation adhesives. Vulcanizing reactive adhesives are a special group. 

F Oligourethane, oligosiloxane, various copolymers A, G or without CL Multiple bond polymerization Polyaddition, radical and ionic polymerization... 

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