Isothermal melt-crystallization and melting behavior for three linear aromatic polyesters

Abstract

Isothermal crystallization and subsequent melting behavior for three different types of linear aromatic polyester, namely poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT), were investigated (with an emphasis on PTT in comparison with PET and PBT). These polyesters were different in the number of methylene groups (i.e. 2, 3, and 4 for PET, PTT, and PBT, respectively). Isothermal crystallization studies were carried out in a differential scanning calorimeter (DSC) over the crystallization temperature range of 182-208• C. The wide-angle X-ray diffraction (WAXD) technique was used to obtain information about crystal modification and apparent degree of crystallinity. The kinetics of the crystallization process was assessed by a direct fitting of the experimental data to the Avrami, Tobin, and Malkin macrokinetic models. It was found that the crystallization rates of these polyesters were in the following order: PBT > PTT > PET, and the melting of these polyesters exhibited multiple-melting phenomenon. Lastly, the equilibrium melting temperature for these polyesters was estimated based on the linear and non-linear Hoffman-Weeks (LHW and NLHW) extrapolative methods.

Antinucleating action of polystyrene on the isothermal cold crystallization of poly(ethylene terephthalate)

“…34,35 In this work, two-stage behavior was detected for some compositions (normally those containing PS) and T c values, but the data (n and K) were taken just from the main crystallization process, that is, the first stage. Crystallization in two stages due to secondary crystallization has been observed by several authors in different polymer systems, including poly(ether ether ketone), 36 PET/poly(ether imide), 37 PET, 38 poly(phenylene sulfide), 39 poly(methylene terephthalate), 40 poly(butylene terephthalate), 41 poly(trimethylene terephthalate), 42 PP, 43 nylon 11, 44 poly(ethylene terephthalate-co-ethylene oxide), 45 syndiotactic PS/atactic PS, 46 PET/polycarbonate, 47 and nylon 11/nylon 66.…”

“…From the endotherms of Figure 10, the T have employed the fundamental Thomson-Gibbs equation, which considers the depression of T m that an infinitely thick crystal will suffer when it is divided by the thickness of the lamellae (l c ). Other authors 1,42,71 have used the most common method of Hoffman and Weeks. A third method is an optical microscopy approach used to observe the melting behavior.…”

Isothermal and nonisothermal crystallization kinetics of poly(ϵ‐caprolactone)

“…A graph for Ozawa theory was constructed from the data points taken at different temperatures in the range [22][23][24][25][26][27][28][29][30][31][32][33][34] C during the crystallization process and is shown in Figure 9. The Ozawa plot shows nonlinearity over the entire temperature range considered and indicates a failure to provide an adequate description of the crystallization of PCL.…”

“…4 The crystallization behavior 4,5 and kinetics of polymeric materials have been reviewed previously. [6][7][8] In particular, the isothermal and nonisothermal crystallization kinetics of commodity and engineering polymers, such as isotactic polypropylene, [9][10][11][12] filled polypropylenes, 13,14 poly(ethylene terephthalate), 15,16 poly(trimethylene terephthalate), 17,18 poly(butylenes terephthalate), 19 nylon, [20][21][22] and poly(sulfides), [23][24][25] have been investigated in detail, and to much lesser extent, those of biopolymers, such as poly(lactic acid) [26][27][28][29] and poly(e-caprolactone) (PCL), [30][31][32][33] have been studied, although they have found wide commercial importance.…”

A Review of the Recent Advances in Cyclic Butylene Terephthalate Technology and its Composites

“…The Avrami rate constant k is the crystallization rate constant related to nucleation and growth parameters; and it depends on the shape (e.g. sphere-, discor rod shaped 46 ) of the growing crystallites. Equation 1 can be linearised which yields…”