Peroxide-containing monomer

Other examples of peroxy inisurfs can also be found in Russian scientific papers. As for instance in Ref. [41] Voronov et al. describe a polymeric surfactant with peroxy side chains for application as inisurfs in emulsion polymerization. They obtained the polymeric inisurf (Inisurf 2) by copolymerization of a peroxide containing monomer (dimethyl-vinylethinyl-methyl-tm-butyl-peroxide) with acrylic or methacrylic acid or 2-methyl-5-vinyl pyridine with benzoyl peroxide as initiator in the presence of dodecylmercaptan as chain transfer agent. The resulting copolymers are water soluble at appropriate pH-values, surface active, and exhibit a critical micelle concentratioiL... 

Peroxide-containing monomer 57 Peroxides, fiee radical initiators 97-103, 105-110... 

Ketone Peroxides. These materials are mixtures of compounds with hydroperoxy groups and are composed primarily of the two stmctures shown in Table 2. Ketone peroxides are marketed as solutions in inert solvents such as dimethyl phthalate. They are primarily employed in room-temperature-initiated curing of unsaturated polyester resin compositions (usually containing styrene monomer) using transition-metal promoters such as cobalt naphthenate. Ketone peroxides contain the hydroperoxy (—OOH) group and thus are susceptible to the same ha2ards as hydroperoxides. 

If pure monomer is to be used ia a reactioa, it must be used iaimediately or stored at < — 20° C to preveat dimerization to any appreciable extent. Chemical inhibition does not prevent dimerization low temperature is preferred. If the monomer has to be stored for more than a few hours, it must be protected against oxygen to prevent peroxidation and polymer formation. Cyclopentadiene monomer reacts spontaneously with oxygen of the air to form brown, gummy peroxide-containing products. 

Nitrogen and oxygen can be Incorporated Into the backbone such that they are surrounded by different atom types. For example, organic peroxides contain two covalently bonded oxygen atoms that form the peroxide linkage. These molecules are Inherently unstable. Two covalently bonded nitrogen atoms are also similarly unstable. These unstable structures decompose to form smaller unstable molecules that are used to start the polymerization for some types of monomers. Thus, to be incorporated implies that the molecules are found only singularly in the backbone chain. Sulfur and silicon are considered to be chain formers. They can be found in the backbone in multiple units connected covalently to molecules of the same type or with carbon. Complete molecules with a silicon backbone are possible, and molecules with multiple sulfur links incorporated into the system are common, particularly in sulfur-crosslinked rubber. 

It is important to pay attention to the potential role of peroxides created on the surface of plasma-treated, including plasma polymer-coated, TPOs in the formation of durable bonds between the substrate and primer. It has been known for decades that the peroxides formed on the irradiated polymers (by y-ray. X-ray, electron beams, etc.) can be utilized in graft copolymerization of various monomers. This method is known as the peroxide method of radiation copolymerization [27]. The trunk polymer is first irradiated by ionizing radiation in a vacuum or in an inert gas environment. The irradiated polymer is exposed to air or oxygen to convert free radicals to peroxides. Thus created peroxides-containing polymers were used as the initiator of the free radical polymerization of the second monomer. The polymer peroxides are decomposed by heat or by the use of reduction/oxidation accelerator, i.e., peroxides are converted to free radicals. 

CHEMICAL PROPERTIES very corrosive may polymerize explosively in the presence of acids polymerization may be caused by elevated temperature, sunlight, oxidizers, or peroxides uninhibited monomer vapor may form polymer in confined spaces usually contains inhibitors to prevent polymerization may react with acids, silver, and chlorinating agents FP (-11°C, 12°F) LFL/UFL (3.3%, 54.8%) AT (320°C, 608°F) HC (-15,930 Btu/lb, -8850 cal/g) HF (91.9 kJ/mol liquid at 25°C). 

It is particularly typical of grafting amine-containing monomers peroxides cause oxidation of amino groups, which leads to a loss of commercial value of a grafted product. It should be remembered that most of the azo compounds are unsuitable as initiators not only because of half-life (tq.s) but also because cyanoalkyl radicals formed are inactive in abstraction reactions of hydrogen from chains. An exception is phenylazo-compounds (33) being a source of phenyl radicals that are most active in hydrogen abstraction reactions (Table 10.3). 

A third example of a polymeric ligand with pH-sensitive solubility is 97. This ligand was prepared by ring-opening metathesis polymerization of the 1,4,7-triazacyclononane-containing monomer 96 by the chemistry shown in Eq. 40 [132]. This polymer was capable of forming Mn(IV) complexes that oxidize alkenes and cycloalkanes with hydrogen peroxide. This basic polymer s solubility is affected by pH, as is the case with the other polymers 93 and 95 described above. 

To prepare polymer wood, wood is degassed and then loaded with a suitable monomer. The monomer is then polymerized. For polycondensations, the preferred monomers are those that do not eliminate volatile components during polymerization (diisocyanates). Both ring-containing monomers (epoxides) and monomers with carbon-carbon double bonds can be polymerized. In the case of the latter, polymerization can be initiated by y-irradiation, peroxides, redox systems, etc. Not all monomers are suitable for the manufacture of polymer wood. Poly(acrylonitrile), for example, is insoluble in its own monomer. In wood, therefore, the precipitation polymerization leads to powdery deposits and not to a continuous phase. The same problem occurs with vinyl chloride, and in this case the boiling point of the monomer (—14 C) is too low. Poly(vinyl acetate) has too low a glass-transition temperature. In addition, monomers with low G values (see Section 21.2.1) need high doses of y rays to initiate polymerization. Commercially used polymers include, e.g., copolymers of styrene and acrylonitrile, poly(methyl methacrylate), and unsaturated polyesters. 

Polymerisation of vinyl toluene in quaternary microemulsions containing cetyltrimethylammonium bromide as the cationic surfactant was studied using laser Raman spectroscopy and dilatometry. The influences of water soluble (potassium peroxodisulphate, ammonium peroxodisulphate) and oil-soluble (azobisisobutyronitrile, benzoyl peroxide) initiators, monomer, surfactant, cosurfactants (n-alcohol and bifunctional alcohols) and temperature on the rates of polymerisation, energy of activation, particle diameter, number of polymer particles, molecular weight of polyvinyl toluene and number of polymer chains per latex particle were investigated. The dependencies of the kinetic and latex size parameters on the initiators and co-surfactants are discussed in terms of the efficiency of the initiators in initiating the polymerisation and on the interfacial partitioning behaviour of various co-surfactants. 19 refs. 

Most of the other fluorine-containing monomers such as trifluoroethylene, hexafluoropropylene, and pentafluoropropylene are used only for copolymerization with vinyl fluoride, vinylidene fluoride, and tetrafluoroethylene [506,521,535,559-562]. Those copolymers, after a convenient vulcanization procedure using peroxides, diisocyanates, or amines, can be applied as fluorocarbon elastomers [564]. Due to the fluorine content, they have high chemical resistance and often a broad temperature range for application [612]. Polymers of interest are the vinylidenefluoride/hexafluoropropylene copolymer and the... 

Monomeric methacrylic acid is soluble in benzene while poly(methacrylic acid) is not. This fact has led to a novel patented continuous slurry polymerization procedure [36]. A 5% benzene solution of methacrylic acid containing 1 % the weight of the monomer of benzoyl peroxide is heated at reflux until a haze due to polymer formation is observed. Then further solutions of initiator-containing monomer are added at a modest rate while the temperature is maintained at 82" C. At the same rate, the formed slurry overflows onto a filter. Over a 72-hr period 85-90% conversion of the utilized monomers was observed. The product was a free-flowing, dustless powder. 

High yields (94%) of polymer are also obtained by adding a preheated (40-45°C) solution of monomer, diacetyl peroxide, and chlorobenzene, over 2.5 h, to chlorobenzene at 105-111°C and subsequent heating for 1 h at 105°C. In another procedure,white powdered polymer, free of monomer, is manufactured with little evolution of heat by charging a heated feed solution of monomer, solvent, and initiator into a heated reaction zone containing monomer and inert solvent. The polymer, which precipitates during the course of the reaction, is easily collected, washed, and dried. 

Structural acrylic adhesives contain monomer, and cure is by a redox system which generates free radicals which cause cure by addition polymerization. Redox systems have two components, one being dissolved in the adhesive and the other in the hardener or catalyst. Once mixed cure is rapid. Examples are cumene hydroperoxide and N,N-dimethyl aniline. Should the peroxide be in the adhesive, then it will slowly decompose to give free radicals, which will cause cure and eventually terminate the shelf life, which is typically 12 months. Chemical reactions obey the Arrhenius relation (O Eq. 18.1). Here k is the rate constant. 

The aqueous phase into which the monomer mix is dispersed is also prepared in a separate tank before transferring to the copolymerization ketde. It contains a catalyst, such as benzoyl peroxide [94-36-0], to initiate and sustain the polymerization reaction, and chemicals that aid in stabilizing the emulsion after the desired degree of dispersion is achieved. Careful adherence to predeterrnined reaction time and temperature profiles for each copolymer formulation is necessary to assure good physical durabiHty of the final ion-exchange product. 

The second largest use at 21% is for unsaturated polyester resins, which are the products of polycondensation reactions between molar equivalents of certain dicarboxyhc acids or thek anhydrides and glycols. One component, usually the diacid or anhydride, must be unsaturated. A vinyl monomer, usually styrene, is a diluent which later serves to fully cross-link the unsaturated portion of the polycondensate when a catalyst, usually a peroxide, is added. The diacids or anhydrides are usually phthahc anhydride, isophthahc acid, and maleic anhydride. Maleic anhydride provides the unsaturated bonds. The exact composition is adjusted to obtain the requked performance. Resins based on phthahc anhydride are used in boat hulls, tubs and spas, constmction, and synthetic marble surfaces. In most cases, the resins contain mineral or glass fibers that provide the requked stmctural strength. The market for the resins tends to be cychcal because products made from them sell far better in good economic times (see Polyesters,unsaturated). 

---