Excitation and emission spectra of polyethylene terephthalate and polyethylene 2,6‐naphthalate films

With excitation by the light of the wavelengths longer than 320 nm, fluorescence spectra of polyethylene terephthalate (PET) films had somewhat different shapes from those excited below 300 nm through the intrinsic absorption of PET molecules. Also, in the measurements taken with a polarizer in front of the receiving monochoromator but none before the sample, the intensity ratio of parallel (to the draw axis of the film) and perpendicular components of the emission spectra was different if excited above 320 nm or below 300 nm. Discussion was made about the first step of pumping photon energy at the wavelengths above 320 nm. Fluorescence spectra of polyethylene 2,6‐naphthalate films showed a mirror image of their absorption spectra, consisting of one broad band having the same polarization as their absorption spectra. Their fluorescence occurred from the lowest excited level, conforming to the Kasha law. Copyright © 1999 John Wiley & Sons, Ltd.     

Deformation band studies of oriented polyethylene and polyethylene terephthalate

Deformation bands formed at the yield point in tensile tests on oriented high-density polyethylene have been studied by optical microscopy and wide-angle x-ray (WAXS) diffraction. The observations of the rotation of the optical extinction direction are shown to obey a simple scheme proposed previously by us: the principal directions of the refractive index ellipsoid within the deformation bands are everywhere parallel to the principal axes of the plastic strain ellipsoid, zero strain referring to the isotropic state. This result is similar to that obtained previously for polyethylene terephthalate (PET) and polypropylene despite the much higher crystallinity obtained with polyethylene. Independent measurements of the molecular reorientation in the deformation bands made using wide-angle x-ray scattering broadly confirm the optical measurements. The results taken together suggest that the material within the band, whether crystalline or not, becomes realigned about the new direction of maximum elongation as if controlled by the deformation of an effective molecular network.     

Mesophase structures in poly(ethylene terephthalate), poly(ethylene naphthalate) and poly(ethylene naphthalate bibenzoate)

Films of poly(ethylene naphthalate) (PEN) and poly(ethylene naphthalate bibenzoate) (PENBB) have been drawn under a variety of conditions of temperature and strain rate to determine the conditions under which a nematic-like mesophase structure can be produced. In PEN the combination of low temperature and high-strain rate encourages mesophase formation, while in PENBB the mesophase was formed under all conditions where it proved possible to draw the material at all. A molecular modelling study of the mesophase in PEN and in poly(ethylene terephthalate) (PET) offers possible structures for the mesophase and showed that the mesophase structure could be stable once formed © 1997 John Wiley & Sons, Ltd.     

Aminolysis of polyethylene terephthalate waste

Polyethylene terephthalate in the form of waste fibres and disposable soft drink bottles was subjected to depolymerisation through aminolysis using excess of ethanolamine in the presence of different simple chemicals, namely glacial acetic acid, sodium acetate and potassium sulphate, as catalysts. The product bis(2-hydroxy ethylene)terephthalamide (BHETA) obtained was in its pure form with sufficiently high yields with all the catalysts. The purified product was characterised by elemental analysis, melting point, IR spectroscopy, Nuclear Magnetic Resonance (NMR) and Differential Scanning Calorimetry (DSC). The process of aminolysis reported here is economically viable since yields of BHETA are as high as 91%, it has potential for further reactions to obtain useful products and the chemicals used as catalysts are common and cheaply available.     

Characterization of gamma-irradiated polyethylene terephthalate by liquid-chromatography–mass-spectrometry (LC–MS) with atmospheric-pressure chemical ionization (APCI)

Low-molecular-weight (low-MW) constituents of polyethylene terephthalate (PET), irradiated with ⁶⁰Co gamma rays at 25 and 50 kGy, were analyzed by HPLC–MS with atmospheric-pressure chemical ionization (APCI). Consistent with earlier results, the concentrations of the major compounds that are present in the non-irradiated PET do not change perceptibly. However, we find a small but significant increase in terephthalic acid ethylester, from less than 1 mg/kg in the non-irradiated control to ca. 2 mg/kg after 50 kGy, which has not been described before. The finding is important because it gives an impression of the sensitivity of the analytical method. Additionally, it shows that even very radiation-resistant polymers can form measurable amounts of low-MW radiolysis products. The potential and limitations of LC–MS for the analysis of radiolysis products and unidentified migrants are briefly discussed in the context of the question: How can we validate our analytical methods for unknown analytes?     

Synthesis of siloxane analogue of polyethylene terephthalate

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Physical mechanism of the electrical polarization of polyethylene terephthalate

The relation between the structural and dynamical properties of amorphous and partially crystalline polyethylene terephthalate and its electret properties was analyzed. The thermal stability of polarization charges and space charges was found to increase with aging in the glassy state and with increasing degree of crystallinity. The discharge behavior was governed by the interaction of real charges and polarization charges. The combination of different charging techniques resulted in a linear superposition of the respective discharge processes on heating.     

Etching of polyethylene terephthalate thin films by neutral oxygen atoms in the late flowing afterglow of oxygen plasma

Films of polyethylene terephthalate were deposited on quartz crystals and exposed to oxygen atoms to study their etching characteristics and quantify the etching rate. Oxygen (O) atoms were created by passing molecular oxygen through plasma created in a microwave discharge. The discharge power was fixed at 250 W, while the pressure of oxygen was 50 Pa. Before exposure to oxygen atoms, a thin polymer film of polyethylene terephthalate (PET) was deposited uniformly over a crystal with a diameter of 12 mm. The crystal was mounted on a quartz crystal microbalance to accurately determine the thickness of the polymer film. The polymer film was exposed to O atoms in the flowing afterglow. The density of O atoms was measured with a cobalt catalytic probe mounted next to the sample and was determined to be 1.2 × 10²¹ m^–3. Samples were treated with O atoms for different periods of up to 120 min. The thickness of the film decreased linearly with treatment time. After 90 min of treatment, a 65‐nm‐thick polymer film was completely removed. Therefore, the etching rate was 0.5 nm/min, so the interaction probability between an O atom and an atom in the sample was extremely low, just 1.4 × 10^–6. Samples treated for different periods were investigated by atomic force microscopy and X‐ray photoelectron spectroscopy to examine the etching characteristics of O atoms in the flowing afterglow. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermal and crystallization characteristics of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends were miscible in the amorphous state in all of the blend compositions studied, as evidenced by a single, composition-dependent glass transition temperature (T_g) observed for each blend composition. The variation in the T_g value with the blend composition was well predicted by the Gordon-Taylor equation, with the fitting parameter being 0.57. The cold-crystallization peak temperature decreased with increasing PTT content, while the melt-crystallization peak temperature decreased with increasing amount of the minor component. The subsequent melting behavior after both cold- and melt-crystallization exhibited melting point depression, in which the observed melting temperatures decreased with increasing amount of the minor component. During melt-crystallization, both components in the blends crystallized concurrently just to form their own crystals. The blend with 60% w/w of PTT exhibited the lowest total apparent degree of crystallinity.     

Vibrational analysis of polyethylene terephthalate and its deuterated derivatives

The Vibrational analysis of polyethylene terephthalate, polyethylene-d₄ terephthalate, and polyethylene terephthalate-d₄ has been carried out using a valence force field calculated from the infrared and Raman spectra of a series of low molecular weight aromatic esters. The Raman spectra for polyethylene-d₄ terephthalate and polyethylene terephthalate-d₄ are presented and band assignments for these compounds and polyethylene terephthalate are discussed.     

Effect of ultraviolet radiation on polyethylene naphthalate films irradiated with high-energy heavy ions

The effect of UV radiation in the spectral range of 280–400 nm on polyethylene naphthalate (PEN) films has been studied. Changes in the optical absorption spectra of PEN after exposure to accelerated ions and UV radiation have been revealed. Changes in the surface properties have been explored, and the depth of the degraded polymer layer after long-term UV irradiation in air has been measured. Depending on the treatment time, the depth has made 0.1–0.9 μm. The photoablation rate and the quantum yield of monomer unit removal due to UV irradiation of the PEN films have been estimated at ~0.7 × 10^?4 molecule/photon. The possibility of the formation of asymmetric pores in PEN films using controlled photooxidative degradation has been shown.     

The determination of carboxyl groups in polyethylene terephthalate

Three methods for the determination of carboxyl groups in polyethylene terephthalate are investigated, viz. (a) dissolution in hot benzyl alcohol, addition of chloroform, and titration with benzyl alcoholic potassium hydroxide solution to the phenol red end-point, (b) dissolution in a mixture of o-cresol and chloroform, and potentiometric titration with ethanolic potassium hydroxide solution, and (c) dissolution in a mixture of o-cresol, chloroform and acetone, and titration with ethanolic potassium hydroxide solution with HF-indication of the end-pointThe three methods yield the same results when applied to several samples of different carboxyl content. For several reasons the potentiometric method is preferred to the other two methods.     

Sulfur modification of polyethylene surfaces. I. Insertion of sulfur into polyethylene surfaces

Atomic sulfur generated respectively by the pyrolysis of carbonyl sulfide and by the photolysis of carbonyl sulfide, carbon disulfide, and sulfur vapors has been shown to modify irreversibly the surface of polyethylene as shown by wettability measurements. The nature of the modification is not completely apparent from this portion of the study, however, insertion of the atomic sulfur into a carbon—hydrogen bond to form a surface thiol group appears likely. The modified surfaces thus formed are shown to undergo several classical organic reactions, as determined by wettability measurements.     

Dynamic mechanical behavior of oriented semicrystalline polyethylene terephthalate

The dynamic mechanical behavior of molecularly oriented semicrystalline polyethylene terephthalate (PET) induced via the equal‐channel angular extrusion (ECAE) process was investigated. Dynamic mechanical analyses in both torsional mode and bending mode were utilized. The results indicate that the ECAE‐oriented PET has a higher dynamic storage modulus above the glass‐transition temperature than that of the reference (control sample). The combined effect of molecular orientation and crystallinity is responsible for the changes in the primary and secondary relaxations of PET. Further analyses show that the shifting and broadening of the primary and secondary peak positions in oriented PET are mainly due to the amorphous‐phase orientation because the crystallinity of PET decreases upon the ECAE processing. A good correlation was found between the structural anisotropy and the dynamic mechanical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1394–1403, 2001     

Sustainability performance of polyethylene terephthalate,clarifying challenges and opportunities

Publications on polyethylene terephthalate (PET) continue to increase including the number of publications on recycling. PET is a versatile material with the ability to be remade from its polymer state through mechanical recycling and even back to its original monomer through advanced recycling. The scale of PET's use affords continued research and applications in improved recycling. Publications on new uses of discarded PET and the ability to clean and convert it into many forms including alternative materials are expanding with an attempt to complete circular use or improve the end of life. As indicated in life cycle assessment studies, increases in recycling lower the energy required to manufacture products. The future for PET will reduce energy demands further with the largest breakthroughs in recycling technologies and bio-sourced resins trending toward zero energy and carbon negative solutions. Opportunities remain for improvement in the use of PET with light weighting. The testing of new resins, development of bio-feedstocks, improvements in engineering, processing, recycling, and design continue to provide benefits. This review provides context for these developments.     

Simulation and optimization of polyethylene terephthalate (PET) reactors

Recent developments in the area of polymerization reactor design and optimization have been highlighted using polyethylene terephthalate (PET) as an example. Both the DMT and the TPA routes for its manufacture have been discussed and it has been demonstrated that a good understanding of the various physical processes present in industrial reactors is required before good models can be developed. The simulations carried out have been tested on some industrial scale reactors as well as pilot plants and improvements have been suggested based on these studies. Presented at the Symposium on ‘Polymer Science and Engineering’ during the Annual Meeting of the Academy, Nainital, October 1982.     

Fibre‐forming blends of polypropylene and polyethylene terephthalate

Bicomponent fibres represent of the new ways for the preparation of synthetic fibres with more variable properties. The polypropylene (PP)‐poly(ethylene terephthalate) (PET) fibre‐forming blend is very interesting because of the improvement of dyeability from bath and some mechanical properties of PP fibres. The new polymer additives containing ester groups which can be added as masterbatches during melting and extrusion processes have been developed in the last years. It has been found that rheological properties of the basic polymer (PP) and polymer additives have a significant role in the blend formation and in spinning. In this work, the influence of some non‐reactive low‐molecular compounds on the processing of fibre‐forming PP‐PET blends and on the properties of blend fibres are presented.