Polymerization melt-phase

Key words In situ infrared spectroscopy, stable free radical polymerization, free radical alternating polymerization, living anionic polymerization, melt phase polyester polycondensation... 

The diamine and the diacid form a PA salt that is soluble in water at elevated temperatures. The polymerization from the PA salt solution occurs in two or three stages. In the first stage a prepolymer is made. This step is carried out under pressure to prevent the evaporation of the more volatile diamine. In the second stage, a polymer is made in the melt phase at atmospheric or slightly reduced pressure. 

The second reaction, the formation of the polyester, is commercially conducted in the bulk melt phase with the removal of ethylene glycol to drive the reaction to high molecular weight. For higher molecular weights, PET can be solid-phase polymerized by again enhancing conditions to remove ethylene... 

When 1,4-cyclohexanedimethanol is used as the diol monomer, phase separation occurs in the polymerizing melts of terephthalate-based polyether-ester copolymers but not those of the analogous isophthalate-based copolymers. Phase separation in the melt during copolymerization, if sufficiently severe, drastically impairs the properties of the product. 

Macrocyclic(butylene terephthalate-co-ethylene terephthalate) co-ester (8.91 mmol) containing about 95 mol% butylene terephthalate was charged into a vial and then heated to 190°C at 1 torr for 5 minutes in an oil bath. This mixture was then treated with 0.30 mol% of the Step 1 product. The mixture was re-heated to the melt phase at 190°C for 10 minutes and polymerized for 15 minutes. Thereafter the polymer began to crystallize, and a white solid product was isolated. 

A sequence of H-abstractions due to the very reactive chlorine radical and / -decomposition gives rise to the formation of polyene molecules and HC1 which is released from the melting phase. Cross-linking reactions between polyenes lead to alkyl aromatic intermediates which can further decompose, releasing tar compounds and/or can polymerize with char formation. These transformations are experimentally observed as a second weight loss in PYC thermo gravimetric analysis. 

Not only does the melting process depend on the thermal history of the sample, the isotropization of the polymeric nematic phase is also history-dependent. Feijoo and coworkers (1988 1990) are apparently the first to have studied in detail the effect on the isotropization of the thermal treatment. According to these researchers the establishment of thermodynamic equilibrium in the nematic phase was not as quick as has been commonly believed, for both the nematic and the isotropic phases are fluid states. They found that the heat and temperature of isotropization of the polymeric nematic phase were remarkably affected by the preceding... 

Extensional Flows The yield stress also occurs in extensional flows [Kamal et al., 1984 Utracki, 1988]. Yield stress is apparent in two related dependencies (i) as a vertical displacement in the stress growth function at decreasing strain rates, contrasting with the normal linear viscoelastic behavior of single-phase polymeric melts, and (ii) as a deviation from the theory that Lim tie(e) = 3... 

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