Infrared studies of cryogenic transitions in poly(ethylene terephthalate)

Abstract

Measurements of infrared absorbance as a function of temperature down to 77°K have been made on poly(ethylene terephthalate). Transitions observed by other techniques such as torsion pendulum measurements are reflected in the infrared measurements by an abrupt change in the slope of the absorbance versus temperature. The infrared measurements are made on bands of known structural origin so the structures contributing to each transition can be determined. The β transition is shown by infrared to be a composite of two peaks with the lower‐temperature portion arising from the amorphous regions and the higher‐temperature portion from the crystalline regions.

Thermophysical properties of macromolecules in the block state

“…(6) in (5) (7) where S T is the isothermal compliance (l and k indices have been omitted since the axis deformation was measured by the spectroscopic method), Gm,n is Grtineisen parameter. (6) in (5) (7) where S T is the isothermal compliance (l and k indices have been omitted since the axis deformation was measured by the spectroscopic method), Gm,n is Grtineisen parameter.…”

Use of Microscopic FT-IR/DSC Combined System for the Study of Glass Transition Temperatures of Polymers

“…4 -8 T 8 was taken from a change in slope or midpoint of the descending graphs of peak absorption vs. temperature. 3 …”

“…Hannon et al suggest that IR spectroscopy is a sensitive and unique means for determining transition behavior in polymers, but sample preparation and the sample cell designed for Tg determination seem to be complicate~. 3 Lin et al recently used newly-developed microscopic Fourier transform infrared (FT-JR) spectroscopy equipped with differential scanning calorimetry (DSC) to study simultaneously the thermal behavior and structural changes of samples such as drug polymorphs, porcine stratum corneum, silicone elastomer, and encapsulated squil oil. 4 -8 This newly-designed system is a simple, quick, and powerful apparatus, in which the sample is only sealed within a KBr disc and set on a DSC microscopy cell.…”

Molecular Weight and Crystallization Temperature Effects on Poly(ethylene terephthalate) (PET) Homopolymers, an Isothermal Crystallization Analysis

“…This phenomenon has been previously proposed in terms of crystal growth regimes, where at high T c , a smooth crystal surface is obtained, while highly imperfect crystals are obtained at low T c , and an intermediate where nucleation and growth or diffusion rates are comparable [9]. In spite of the great number of studies on the isothermal crystallization of PET [1][2][3][4][5][6][7][8], few reports analyze simultaneously the effect of molecular weight and degree of supercooling on the crystallization process of this polymer. The present work aims to provide, via utilization of conventional and advanced techniques, a more complete analysis of the isothermal crystallization of PET by taking into account the simultaneous effects of both the molecular weight of the material, as well as the degree of supercooling in the polymer crystallization process.…”

“…Also, an important amount of this polymer is used for the fabrication of bottles for a variety of beverages [1]. As a semicrystalline polymer, PET has been studied in both isothermal and dynamical crystallization regimes [2,3]. Variables affecting the crystallization process are molecular weight, crystallization temperature, co-monomer content, nucleating agents, among others [4].…”