Poly condensation, melt

Melt poly condensation The reaction is carried out in a 250-mL stainless steel vessel with nitrogen inlet and mechanical stirrer. The vessel containing T4T-dimethyl (30 g, 72.8 mmol) and ethanediol (30 g, 0.48 mol) is heated up in an oil bath at 200°C. After 15 min reaction TiO -OCaJ I7 )4 (1.5 mL of 0.1 M solution in CH2C12) is added and subsequently the temperature is gradually raised to 260°C (l°C/min). After 10 min at 260°C the pressure is reduced (15-20 mbar) for 5 min. Then the pressure is reduced further (<2.5 mbar) for 45 min. The vessel is cooled down slowly to room temperature, maintaining the low pressure. After solidification, the polymer is ground (particle size <1 mm) and subsequently dried in a vacuum oven at 80°C. 

Several routes have been reported for the synthesis of aromatic poly(azole)s such as poly(benzimidazole), poly(benzoaxazole), and poly(benzthiazole) melt polycondensation of dicarboxylic acid diphenyl esters with tetramines21 and high-temperature solution polycondensation of dicarboxylic acids or their derivatives with tetramine hydrochlorides in PPA.22 PPA acts as condensing agent and solvent. Ueda etal.23 developed a modified method for the synthesis ofpolyazoles with the use of PPM A. 

Hoftyzer and van Krevelen [100] investigated the combination of mass transfer together with chemical reactions in polycondensation, and deduced the ratedetermining factors from the description of gas absorption processes. They proposed three possible cases for poly condensation reactions, i.e. (1) the polycondensation takes place in the bulk of the polymer melt and the volatile compound produced has to be removed by a physical desorption process, (2) the polycondensation takes place exclusively in the vicinity of the interface at a rate determined by both reaction and diffusion, and (3) the reaction zone is located close to the interface and mass transport of the reactants to this zone is the rate-determining step. 

The chemistry of the solid-state polycondensation process is the same as that of melt-phase poly condensation. Most important are the transesterification/glycolysis and esterification/hydrolysis reactions, particularly, if the polymer has a high water concentration. Due to the low content of hydroxyl end groups, only minor amounts of DEG are formed and the thermal degradation of polymer chains is insignificant at the low temperatures of the SSP process. 

PCT, PETG, PCTG and PCTAs can all be prepared readily via standard melt-phase poly condensation processes [34, 35], The diacid can be delivered via transesterification of the dimethyl esters or via direct esterification of the diacids. Numerous conventional catalyst and catalyst combinations can be employed. The use of a catalyst or catalyst combination is important for the manufacture of polyesters via the melt-phase process and has been well reported in the literature [36-41], Appropriate catalyst systems enable the production of polyesters with high processing rates and high molecular... 

Melt poly condensation is also the most popular method for other thermotropic condensation polymers, including the polyazomethines where the reaction between aromatic aldehydes or ketones and primary amines with elimination of water leads to azomethine (Schiffs base) formation 48). 

Comparison of the Two Reactions Step-Growth Polymerization in More Detail Making PET in the Melt Interfacial Poly condensation Chain-Growth Polymerization in More Detail Free Radical Chain Polymerization Going One Step Better Emulsion Polymerization Copolymerization Ionic Chain Polymerization It Lives ... 

Reported values for the activation enei of the amidation reaction vary. For the melt poly condensation of aminoundecanoic acid the activation energy was found to be [87] 11 kcal mole for the polycondensation of the same acid as a 30% solution in m-cresol, the reported [92] activation energy is 31 kcal mole". The activation energy of the second-order melt polycondensation of p-aminophenylalkanoic acids was reported [93] to be between 17 emd 19 kcal mole". ... 

The problem of anionic structure and the quantitative distribution of particles in silicate melts (see also in Chapter 2.1.9.) is discussed in several works. The simplest application of the Flory s (1953) polymer theory to silicate melts is the theory of linear and branched chains proposed by Masson (1965, 1968, 1977) and Masson et al. (1970). In this theory, it is assumed that the silicate anions are composed exclusively of linear and branched chains of the general formula Si 03 " j. These chains arise by poly-condensation reactions of the type... 

Polymer plasticization and overcoming compatibility problems helps in synthesis of many polymers in the presence of supercritical carbon dioxide. Carbon dioxide has been fotmd to be inert towards free radicals and cations but dramatically decreases glass transition temperamre of polymer due to plasticization (e.g., polystyrene Tg is reduced by about 50°C). Plasticization is especially useful in melt phase poly condensation processes. 

Polyesters with molar masses of a few thousand are obtained by poly-condensing ethylene glycol with adipic or sebacic acid. The polymers have low glass transition temperatures, because of the flexible ester groups, as well as low melting temperatures, and so are used as flexible segments for elastic fibers, as secondary plasticizers, as nonfatty ointment or cream bases, as well as making leather impermeable because of its water-repellent action. 

The necessary functional group equivalence required for the poly condensation is achieved by first producing the salt from molar equivalents of the diamine and dicarboxylic acid. For example, adipic acid and hexamethylene diamine form what is known as the AH salt. The purified salt is directly used in the melt polycondensation. The amidation equilibrium is so favorable that the polycondensation can take place in the presence of water, which is therefore used as a heat sink. A typical industrial synthesis is, for example, the polycondensation of the AH salt a 60%-80% sludge of the salt is precondensed with a little acetic acid as regulator (see also Section 28.2.3.2) at 275-280° C for 1-2 hr at 13-17 bar, that is, at the vapor pressure of the steam produced. After a yield of 80%-90% has been reached, further condensation takes place above the melting temperature of 264° C under vacuum. 

This polyamide is prepared somewhat differently. Salts of the diamine isomers with terephthalic acid are only partially poly condensed and the reaction is completed during extrusion [71], because the melt viscosity of the polymer is very high. The product is amorphous and exhibits greater light trasmittancy. It melts at 200°C and is sold under the trade name of Trogamid T. 

In the vast majority of cases, poly condensations are carried out in the melt at temperatures between 120 and ISO C in an inert gas atmosphere (N2, CO2, SO2) with or without added catalyst. However, the melt condensation presupposes thermally stable monomers and polymers. 

Aminoundecanoic acid is poly condensed in the melt with the elimination of water. The tensile strength of the fiber, 54-63 g/tex, is relatively high. Nylon 11 is produced in France (Rilsan), Brazil, India, the United States, and the USSR. In the first three countries, castor oil provides a cheap supply of raw material (2.5 x 10 kg/yr). In the USSR, the monomer is manufactured by telomerization (cf. nylon 7). 

Oligomers Poly condensation pr Output, Melting Estimated molar Hydroxile ... 

Solution poly condensation polymerization is used when the temperatures needed to melt the monomer are too high or when bulk (mass) polymerization is too exothermic and hazardous. With solution polymerization, monomers and polymerization initiators are dissolved in a nonmonomeric liquid solvent at the start of polymerization. The solvent is usually a solvent for the polymer and copolymer product. 

PolyCtrimethylene terephthalate) (PTT, also abbreviated as 3GT) is an aromatic polyester made by the melt poly condensation of 1,3-propanediol (PDO) with either terephthalic acid (TPA) or dimethyl terephthalate (DMT). Although available commercially only since 1998, it was one of the three polyesters first synthesized by Whinfield and Dickson (1) in 1941. Two of which, the so-called even-munhered polyCethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) for the number of methylene units in their chemical structures, are well-estabhshed high volume polymers. However, the odd-numbered PTT remained an obscure polymer. It was never commercialized until recently because PDO was very expensive and was available only as a small volume line chemical. 

An unsaturated polyester with = 140 °C and T = 20 °C has been prepared from 1,4-CHDM and diethyl fumarate by melt poly-condensation. The polyester was then crosslinked using N-vinyl pyrrolidone in the presence of variable amounts of inorganic fillers. The hydrolytic stability of these composites with different compositions was then examined for their potential use as bioresorbable boned cements (27). 

More recently, Overberger and Takekoshi [61] described the synthesis of C-methyl-7-nylon polymers from 3-, 4-, 5- (XXIXa,b) and 6-methyl-7-aminoheptanoic acids obtained from the corresponding aminoacids or lactams. The latter were polymerized by heating, in the presence of water and the former by melt poly condensation the yield and the molecular weight are both high despite the side group. 

In order to improve the compatibility during melt blending, the same approach was extended to different poly condensation blends a catalyst was added in some cases [15,16]. Blends of PET/PA6, polyamide 66 (PA66)/PA6 and PET/PA6/PA66 in weight ratios of 40/60, 40/60, and 20/60/20,... 

Blends of biodegradable synthetic aUphatic polyesters and starch are used to produce sheets and films for packaging by film extmsion or blown film methods. Up to 50% of the synthetic polyester can be replaced with starch. A polyester synthesised from the poly-condensation of 1,4-butanediol and a mixture of adipic and succinic acids has been blended with wheat starch by Lim (1999) (Nolan-ITU Pty Ltd, 2002). The blends were found to have melting points near that of the polyester alone. Plasticisers were also added to the starch to improve flexibiUty and processability of the blend. The modified blends were found to retain a high tensile strength and elongation, even at high starch concentrations. 

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