Polymerizations, thermal

Polyquinolines have also been obtained by a post-polymerization thermal treatment of poly(enamino nitriles) (93). The resulting polymers show excellent thermal stabiUty, with initial weight losses occurring between 500 and 600°C in air (tga) under nitrogen, initial weight loss occurs at about 600°C and there is a 20% weight loss up to 800°C. 

Polymerization. Thermal polymerization or curing of an ink film at elevated temperatures can foUow many different chemical paths. Condensation and cross-linking reactions may be accompHshed with or without the use of catalysts. However, this method of drying generally has not been widely used for printing inks, except those used for metal and glass decoration, and some clear coatings. 

Polyfumarates. Because of steric hindrance, fumarates are difficult to polymerize into high molecular-weight polymers. However, it was demonstrated during the early 1980s that bulky fumarates, such as di-/-butyl fumarate, 0 2 200 [7633-38-7] (3), can be polymerized thermally into high... 

In S polymerization, thermal initiation will be a source of extra chains. Additional chain formation processes will cause the molecular weight to be lower than anticipated by cq. 7. Sometimes conventional thermal initiators are added with similar effect (see also eq. 12). A pre-tailing molecular weight distribution may result. 

Acid-base, hydrolysis, hydration, neutralization, oxidation-reduction, polymerization, thermal degradation Adsorption-desorption, precipitation-dissolution, immiscible-phase separation, biodegradation, complexation Acid-base, neutralization, oxidation-reduction (most inorganic and some biologically mediated), adsorption-desorption, precipitation-dissolution, complexation Hydrolysis, oxidation-reduction (biodegradation of anthropogenic inorganics), immiscible-phase separation... 

Coking Polymerize Thermal Convert Gas oil, coke Gasoline,... 

Simple saltams, 1,2-thiazetidine 1,1-dioxides, are known to polymerize thermally (73MI51500), although in one case the alkene product was reported to be formed with retention of stereochemistry (Scheme 11) (75BCJ480). 

We recently synthesise a new polymer (see exp. part) containing significant amounts of tetra-methyl piperidine groups. Such a polymer is a very efficient polymeric thermal stabilizer for elastomer however, when present in low content in the polymer matrix its IR detection is not easy because of the low absorption coefficients of all its functional groups. 

Physical entrapment or chemical coupling is a well-established procedure for MIP preparation. First, a complex is formed between a functional monomer and template in an appropriate solvent solution. Then the complex is immobilized by polymerization in excess of a cross-linker. Predominantly, free-radical polymerization thermally launched with a 2,2-azobis(isobutyronitrile) (AIBN) initiator, is performed. In the case of photo-radical polymerization, a benzophenone or acetopho-none derivative is also used as the initiator [101]. Next, the template is extracted by rinsing the resulting MIP block with a suitably selected solvent solution. The bulk... 

The coloring and bleaching phenomena are caused by changes in molecular configuration of colloidal phosphorus formed in the glasses. The P molecule (liquid or white phosphorus) is colorless. It polymerizes thermally or photochemically to the... 

Copolymers of vinyl chloride-vinyl bromide were prepared in bulk using the same conditions in the preparation of PVC, except that only uranyl nitrate was used as in initiator with visible light to avoid photodegradation during polymerization. Thermal analysis of the copolymer indicated random placement of the two comonomers. 

The amount of thermal initiation which takes place at 138°C. and its effect on molecular weights and their distributions were also studied. Two batches were polymerized thermally using monomer mixture A. 

SCT (Feed) Processes Vacuum Distillation Catalytic (Air) Polymerization Thermal... 

It appears that the reaction mechanism and the intermediates involved in the solid-state polymerization of diacetylenes are reasonably well understood. However, experimental results obtained with special monomers should not be generalized. It is not possible to design a monomer with desired properties. Inspection of Table 1 shows that on the basis of the crystallographic data and the monomer packing the absolute reactivity and the polymerization kinetics caimot be quantitatively predicted, e.g. it is not possible, to date, to explain why certain diacetylenes can be polymerized thermally whereas others with equal packing are thermally inactive. A more realistic kinetic model should include the various energy transport processes and the complex side group motions which are connected to the reaction. 

From the discussion above, it is clear that there is no evidence for catalysis of persulfate initiation in emulsion polymerization systems. However, many ionic reactions have been shown to be subject to large catalytic effects in the presence of emulsifier micelles (Fendler and Fendler, 1975) so that the question arises as to whether there are any radical reactions that are subject to micellar catalysis and whether this phenomenon plays any part in any emulsion polymerization systems, Prima fade evidence that uiicellar catalysis may be important when emulsified monomer is allowed to polymerize thermally is provided by the work of Asahara et al. (1970, 1973) who find that several emulsifiers decrease the energy of activation for thermal initiation of alkyl methacrylate and styrene, [n particular, the energy of activation for thermal initiation of styrene emulsified with sodium tetrapropylene benzene solfonate was reported as S3 kl mol. much lower than any value determined in bulk. Hui and Hamielec s value of ] IS kj tnol (1972) seems to be representative of the data available on thermal initiation in bulk. The ctmclusions of Asahara et al. are based on observations of the temperature dependence of the degree of polymerization and are open to several objections. 

Compound 25 (R = Ph) has been found to polymerize thermally at elevated temperatures to yield the poly(ferrocenylphosphine) 27 (R = Ph), which is spectroscopically identical to the material previously prepared by condensation routes (51). Similar ROP reactions have been detected for a variety of analogous species (51,63). 

This requirement is easily met when styrene is polymerized thermally (45-47) and when lactams are polymerized in the presence of alkali metals (48-52) but it is doubtful that a large kp/k ratio can be Justified for the "a.m." mechanism. 

Several cyclic bis(arylene tetrasulfides) have been synthesized within the last few years. These ring compounds can be polymerized thermally in much the same way as sulfur itself. However, whereas polymeric sulfur depolymerizes on standing at room temperature, the poly(arylene polysulfides) considered here are stable polymers under ordinary conditions. The mechanism by which the cyclic bis-(arylene tetrasulfides) polymerize has been established by ESR as a free-radical process. The maximum number-average molecular weights are from 15,000 to 16,000. 

The bisdichloromaleimides thus obtained may be polymerized thermally by the opening of the double bond. Such cross-linking... 

C2F4 is also made by quenching CF2 radicals formed at temperatures above 1500° by the reaction of almost any source of fluorine with carbon. Tetra-lluoroethylene, b.p. —76.6°, can be polymerized thermally or in aqueous emulsion by use of oxygen, peroxides, etc., as free-radical initiators. A convenient laboratory source of C2F4 is thermal cracking of polymer at 500-600°. 

When a similar reaction mixture is polymerized thermally at 75°C, gel forms after only 6% conversion [71]. Below 25°C, visible light (photoflood lamps) or UV radiation may induce the decomposition of benzoyl peroxide or of biacetyl. These decompositions, in turn, bring about polymerization of the monomer. 

Chloioacelaldehyde (CAS 107-20-0) Extremely corrosive upon direct contact severe burns will result. Vapors extremely irritating to eyes, skin, and respiratory tract. 1 ppm (C) 45 ppm Colorless liquid wilh a pungent, irritating odor. Vapor piBssuiB is 100 mm Hg at 20°C (68 E). Combustible. Readily polymerizes. Thermal-break-down products include phosgene and hydrogen chloride. 

After degassing, the flask is closed quickly and tightly and the mixture is ready to polymerize. Thermally initiated polymerization... 

Styrene polymerizes thermally. This is discussed in Chapter 2. 

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