Microkinetics of crystallization in poly(ethylene terephthalate)

Abstract

The lamellar growth kinetics and lamellar thickness of poly(ethylene terephthalate) crystallized from the glassy state have been determined as a function of crystallization temperature. Values of end and side surface free energies have been estimated as well as the residual lamellar thickness. Analyses carried out using secondary nucleation approaches indicate that the width of a critical nucleus is comparable to the effective substrate length for multiple nucleation in this and other slowly crystallizing polymers at high supercoolings. A “universal” critical value of T italicm2/T2ΔT below which the strip completion process ceases was found to exist. All crystallization must, therefore, occur through the deposition of critical nuclei. Models are proposed for this process which appear to be consistent with both neutron scattering and infrared experiments on quenched polyethylenes. Comparison of crystallization rates, expressed as “jump” rates, with relaxation frequencies suggest that in order for crystallization to occur at any given temperature the relaxation frequency must be at least two decades faster than the crystal “jump” rate.

Isoconversional Approach to Evaluating the Hoffman–Lauritzen Parameters (U* and Kg) from the Overall Rates of Nonisothermal Crystallization

“…Using a ¼ 4.56 Â 10 À10 m and b ¼ 5.53 Â 10 À10 m, as determined by Palys and Phillips, [25] we find s ¼ 1.2 Â 10 À2 J Á m À2 . Substitution of this value into ss e permits estimation of the fold surface free energy as s e ¼ 6.3-7.5 Â 10 À2 J Á m À2 .…”

“…The volumetric heat of fusion (Dh f ¼ 2.1 Â 10 8 J Á m À3 ) is determined as the mass heat of fusion (140 J Á g À1 ) [18] times the density (1.5 g Á cm À3 ). [24] The monomolecular layer thickness, b, is 5.53 Â 10 À10 m. [25] The values of ss e evaluated from K g equal to 3.2 Â 10 5 K 2 (n ¼ 4 in Equation (5)) and 1.9 Â 10 5 K 2 (n ¼ 2 in Equation (5)), respectively, are 7.6 and 9.0 Â 10 À4 J 2 Á m À4 . The product ss e can be split by using the empirical relationship: [12] s ¼ 0:11 Dh f ffiffiffiffiffi ab p ð17Þ…”

Crystallization of poly(ethylene terephthalate-co-isophthalate)

“…The parameter m used in eq 6 is 2 according to the regime-II kinetics for PET crystallized at T c ϭ 120ϳ210°C. 41 Using the half-time of crystallization t 1/2 instead of the growth rate G, eq 5 can be rewritten as:…”

“…5 These results indicate that the K g and G o of PET are The data of b and ⌬H f o were reported to be 5.53Å and 1.8 ϫ 10 8 Jm Ϫ3 , respectively for PET. 41 Because the molar ratio of isophthalate in PETI-2 and PETI-12 is low, we assume that these copolyesters have the same b and ⌬H f o as those of PET. The e data of these polyesters are then determined from eq 6 and shown in Table V.…”

Use of thermal analysis techniques for examining blow-molded pet bottle specimens

“…bottle had almost a 20% higher crystallization rate than the 64 oz. bottle, based on literature data on amorphous PET for the growth rate of spherulites at several crystallization temperatures by hot stage optical microscopy [8].…”