Polymerization in the Melt

Many reports on the polymerization of PET cyclic oligomers, with various results, have appeared. Polymerization in the melt at 275-310 °C has been reported by Goodman and Nesbitt [8], The latter claimed that a linear polyester was formed when the macrocycles are heated with a catalyst, neat, or in 2-methylnaphthalene at 240 °C. They also stated that scrupulously dried material... [Pg.134]

Polymerization in the melt is widely used commercially for the production of polyesters, polyamides, polycarbonates and other products. The reactions are controlled by the chemical kinetics, rather than by diffusion. Molecular weights and molecular weight distributions follow closely the statistical calculations indicated in the preceding section, at least for the three types of polymers mentioned above. There has been much speculation as to the effect of increasing viscosity on the rates of the reactions, without completely satisfactory explanations or experimental demonstrations yet available. Flory [7] showed that the rate of reaction between certain dicarboxylic acids and glycols was independent of viscosity for those materials, in the range studied. The viscosity range had a maximum of 0.3 poise, however, far below the hundreds of thousands of poises encountered in some polycondensations. [Pg.481]

The extent of polymerization (value of n) could not be calculated, however, it is assumed that polymerization in the melt is rather small and more likely, that the molecular... [Pg.400]

Glycolide (mp = 84-85 °C, t. subl. = 80-84 °C/1 mm Hg) is polymerized in the melt using Lewis acids (SbF3, ZnCl2, SnCl2, stanneous octoate) or other metal salt cata-... [Pg.183]

Capryllactam can be readily polymerized in the melt at 240°C for 24 hr with a small amount of amino acid to form polycapryllactam or nylon-8 [74,75]. It can also be polymerized rapidly with anionic initiators [76]. The polymer exhibits good thermal stability and a relatively low melt temperature of 200°C. The low melt temperature and the high cost of an intermediate have limited the usefulness of this polymer. [Pg.56]

Polymerizations in the melt above 62 °C are very rapid. They come within a few minutes to completion at 70 °C when catalyzed by lO mole of boron trifluoride. This procedure, however, is only useful for preparation of small quantities of the polymer, because the exothermic heat of the reaction is difficult to control. [Pg.183]

Table 16-3. Pressure Dependence of the Polymerization in the Melt of a-Methyl Styrene...

Two types of PET were used in Overton s study [49] one polymerized in the melt, the other in the solid phase. Molecular mass calibration was achieved using both conventional polystyrene standards and PET fractions, the latter being prepared by precipitation of the polymer from a mixed solvent solution of phenol in tetrachloroethylene by progressive addition of n-hexane. Molecular masses of the fractions were determined by inherent viscosities. [Pg.86]

The transesterification reaction by-product—water when TPA is used or methanol when DMT is used—is removed during reaction. The second stage is a polycondensation step, in which the prepolymer BHBT formed in the first stage undergoes further polymerization in the melt phase. The two reaction stages can be easily differentiated by the by-product types ... [Pg.133]

Caprolactam can be polymerized in the melt by use of a base and an activator. Two components, I and II, are used as starting materials. Component I is a catalyst-containing lactam melt and component II is an activator-containing lactam melt. The catalyst can be the sodium salt of caprolactam and the activator can be a derivative of caprolactam such as that prepared by the reaction of caprolactam with acetic anhydride or a diisocyanate [19]. The following example uses the derivative of caprolactam withhexamethylene diisocyanate. [Pg.124]

Literature on the stability of individual cydk disulfides covers (i) compounds that polymerize on standing like 3,3-dimethyl-1 -dithiolaiK [124,12, 3-hydroxy-l,2-dithiolane [126] and iV-phenyl-4-oxo-5-aza-l,2-dithia-cyclohexane [127,128] ii) compoimds which polymerizes on heating such as dibenzo-lA5,6-tetrathiocin [129] and iii) compounds that polymeixK in neat form when a catalyst is added, such as cis-l,2-dithiacyclohex-4-aie [130] and l-oxa-4,5-dithiacycloheptane [13, 119, 130]. Detailed study of the stability of cyclic disulfides towards polymerization revealed that 1,2-dithiai are the only class of simple cyclic disulfides that is thermodynamically staUe with respect to its polymerization in the melt or as concentrated solutions [131]. [Pg.100]

The unique advantage of using the macrocyclics to prepare polymer-based nanocomposite is the practicable application. This is due to the fact that these macrocyclic oligomers can instantly polymerize in the melt in the absence of any catalyst or initiator at a temperature as low as 150"C, without liberation of any volatile by-products. " Therefore, they can be processed more easily compared with other polymerization processes. [Pg.526]

Synthesis of cyclic oligocarbonates by phosgenation in dilute solution followed by ring-opening polymerization in the melt [88]. [Pg.82]

The anionic polymerization of lactam (e.g. CL) can be performed in two different temperature modes. Polymerization in the melt of the lactam below the melting point of polymer is characterized by polymerization, followed by crystallization. However, sometimes-depending on the initial polymerization temperature-the formation of polymer is accompanied simultaneously by crystallization. In both... [Pg.170]

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