Synthesis of copoly(ethylene terephthalate /imide)s and crystallization kinetics

Abstract

Copoly(ethy1ene terephthalate/imide)s (PETI) were prepared by melt polycondensation of bis(2-hydroxyethy1)terephthalate (BHET) and imide containing comonomer, 4,4'-bis[(4-carbo-2-hydroxyethoxy)phthalimido]diphenylmethane (BHEI) with Sb,O, as catalyst at 280°C under vacuum ( -1 mm Hg). The change of T, with an increase of the BHEI repeat unit in the PETI copolymer was analyzed by the Flory equation. On isothermal crystallization, a longer induction time and a lower activation energy than for the PET homopolymer were observed with an increasing amount of the BHEI repeat unit. The Avrami exponent, n, increased from 1.5 to 2.3 as the content of BHEI or crystallization temperature was increased. The Avrami rate constant K decreased with the increase of the BHEI unit. On nonisothermal crystallization, the Ozawa equation and Lawton plot were used to investigate the effect of BHEI units on the crystallization kinetics of PETI copolymers. From the change of the cooling crystallization function and the result of the Lawton plot, it was found that the BHEI unit effectively decreases the rate of crystallization.

Crystallization of 2‐methyl‐1,3‐propanediol substituted poly(ethylene terephthalate). I. Thermal behavior and isothermal crystallization

“…This suggests that more thermal energy (and/or time) is required for the molecular rearrangement that is required for nucleation and crystal growth. This has been reported for other PET copolymers as well 10, 1…”

“…Therefore, as crystal thickness decreases, the surface energy of the crystal becomes more influential, resulting in a depression of the melt temperature. Again, this has been witnessed for many other PET copolymers,1, 13–15 and in particular for those containing short diols 12, 15, 16…”

“…As a general rule, adding a comonomer reduces the crystallinity and rate of crystallization. For example, PET copolymerized with the imide containing monomer 4,4′‐bis[(4‐carbo‐2‐hydroxyethoxy)phthalimido]diphenylmethane,1 and polyethylene isophthalate2 exhibit this effect. It is important to note, however, that many investigators have found evidence suggesting that copolymerizing PET with certain species actually increases the rate of crystallization.…”

Crystallization Kinetics of Lactose and Sucrose Based On Isothermal Differential Scanning Calorimetry

“…Isothermal DSC has been used extensively to study crystallization of polymers such as poly(ethylene terephthalate) (PET) (Chan and Isayev, 1994;Chan et al, 1995), poly(phenylene sulphide) (Auer et al, 1994) and copoly (ethylene terephthalate/imide)s (Park and Lee, 1995). The technique has been used less frequently in the study of low molecular weight compounds such as disaccharides (Elamin et al, 1995;Roos and Karel, 1990).…”

Synthesis and thermal behavior of new poly(ethylene terephthalate-imide)s

“…Copolymerization is always an effective method in the chemical modification of PET or other polyesters. Many publications have appeared on the incorporation of rigid units to improve the heat resistance or mechanical properties of PET 7–14. Among them, the PET/ p ‐hydroxybenzoic acid (HBA) copolymers are successful examples and were probably the first commercialized thermotropic liquid‐crystal polymers 7, 8.…”