Melt-phase poly

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... 

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. 

This chapter is concerned with these phases, where a substantial amount of the experimental work has been on poly(oxyethylene)-containing block copolymers in aqueous solution. From another viewpoint, the phase behaviour in concentrated block copolymer solutions has been interpreted using the dilution approximation, which considers concentrated solution phases to be simply uniformly swollen melt phases. Work on styrenic block copolymers in concentrated solution has been interpreted in this framework. There is as yet no unifying theory that treats ordered micellar phases and diluted melt phases coherently. 

End-group association in the melt can differ tremendously from that in solution. Binder s group recently investigated mixtures of polyisobutylenes (PIBs) and poly (butyl acrylates) containing thymine (Thy) and 2,6-diaminotriazines (DAT) end groups [58-60]. Thymine and DAT both self-associate however, they favor the formation of heterocomplementary complexes. Blends of monofunctional and telechelic polymers were systematically studied in solution and melt phases. 

Chiu FC, Ung MH (2007) Thermal properties rmd phase morphology of melt-mixed poly (trimethylene terephthalate)/polycarbonate blends-mixing time effect. Polym Test 26 338-350 Chuah HH (2004) Effect of process variables on bulk development of air-textured poly (trimethylene terephthalate) bulk continuous filament. J Appl Polym Sci 92 1011-1017 Chuah HH, Lin VD, Soni U (2001) PTT molecular weight and Mark-Houwink equation. Polymer 42 7137-7139... 

Figure 7.22 represents a typical DSC ttace of copolymer melting. The poly(ethylene-co-vinyl acetate) is expected to follow a eutectic phase diagram. The melting temperature decreases from the value of the homopolymer, but the crystallinity decreases much more than expected from the small amount of noncrystallizable comonomer. Also, the crystallization of a eutectic component, required by an equilibrium phase diagram, seen for example in Fig. 7.1, is rarely observed in random copolymers with short repeating units, as in vinyl polymers. 

An example is melt phase polycondensation of a mixture of dimethyl terephthalate (DMT) + poly(tetramethylene oxide) glycol + an excess of tetramethylene glycol. A wide range of properties can be built into the TEEE by using different mixtures of isomeric phthalate esters, different pol5uneric glycols, and varying MW and MWD. Antioxidants, such as... 

The melt phase grafting reaction of acrylic acid onto polypropylene proceeds by a free radical mechanism (10). Radicals generated by thermal decomposition of an initiator abstract hydrogen from the polypropylene backbone and initiate homopolymerization of acrylic acid. Acrylic acid also adds to the sites on the backbone, with the result that the product contains acrylic acid grafted polypropylene (AA-g-PP) and poly(acrylic acid) homopolymer. 

Poly(ethylene terephthalate) (PET) is commonly prepared by melt-phase polycondensation reactions. Bis(hydroxyethyl) terephthalate (BHET) was converted to PET under a variable flow (2-10 mL/min) of CO2 at 20.7 MPa (207 bar) (95). Molecular weights were obtained over the range 3 x 10 to 6.3 x 10 g/mol and increased significantly with flow rate and/or reaction time. These values are low compared to normal molecular weights obtained in commercial processes (approx. 2 X 10 g/mol) and may be attributed to the decreased solubility of the ethylene glycol condensate in CO2 compared with phenol in the polycarbonate system. 

The effect of interaction of polycaproamide and poly(ethylene terephthalate) in the melt phase on their melt spinning behaviour has also been described. ... 

The most widely known aromatic homopolyester made of 1,4-CHDM is doubtless poly(l,4-cyclohexylenedimethylene tereph-thalate) (PCT) (Figure 6.5). This polyester, which was firstly developed in 1959 by Tennesee Eastman Co. for its utilization in the fiber industry with the trade name of Kodel, is nowdays produced by two-step melt phase polycondensation from DMT and 1,4-CHDM. When high molecular weight PCT is desired, the... 

Luyk [251] has examined formation of poly-brominated dibenzo-/ -dioxins (PBDD) and diben-zofurans (PBDF) during thermal processing of polymers containing polybrominated diphenyl ethers. The formation of PBDDs and PBDFs is a result of thermal and mechanical stress in the melt phase or condensed phase. The yield depends on temperature... 

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