PET Samples Research Articles

Model-free isoconversional method applied to polymer crystallization governed by the Hoffman-Lauritzen kinetics

A new method is developed to obtain the kinetic parameters of polymer crystallization from measurements of the transformation rate usually done at (but not restricted to) constant heating or cooling rates. It can be considered a generalization of the Fiedman's isoconversional method to deal with the Hoffman-Lauritzen temperature dependence. Apart from delivering the U* and Kg parameters as a function of the transformed fraction, this method allows to predict the crystallization course for an arbitrary thermal history. It has been applied to the crystallization of PET and PA6 samples, monitored by differential scanning calorimetry (DSC).

Recycling of PET wastes using Electron beam radiations and preparation of polyurethane coatings using recycled material

Poly (ethylene terephthalate) (PET) products consumption has been increased dramatically over the past few decades which have resulted in generation of large quantity of PET waste. Disposal of this waste is a global concern due to its nonbiodegradability. In the present study, we report the effect of electron beam (EB) radiations on degradation of PET and its subsequent effect on glycolysis by using excess ethylene glycol (EG). The results as analyzed by molecular weight determination showed an increase in the extent of depolymerization of PET proportional to the dose of EB irradiation. The irradiated PET samples were further subjected to chemical recycling by glycolysis using conventional and microwave method in presence of excess EG and zinc acetate (0.5%) as a catalyst. Depolymerization of PET by EB irradiation resulted in increased yield of BHET after variable time intervals. The recycled material BHET was subjected to esterification using linseed oil fatty acid, further epoxidation using formic acid and hydrogen peroxide and subsequent hydrolysis to prepare ecofriendly polyol. The individual step product was analyzed for its physical and chemical parameters like% NVM, hydroxyl value, acid value, iodine value, oxirane oxygen content etc. and also characterized by spectroscopic analysis like FTIR, 1H NMR, 13C NMR and GPC technique for molecular weight determination. Polyurethane coatings based on this polyol were prepared using various commercial polyisocyanate curing agents. The coated films were evaluated for their optical, mechanical and chemical properties. Thermal properties of coatings were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

The Effect of Flipped Model of Instruction on EFL Learners’ Reading Comprehension: Learners’ Attitudes in Focus

The present study aimed at investigating the effect of flipped model of instruction on EFL learners’ reading comprehension ability. Moreover, this study aimed at identifying EFL students’ attitudes toward flipped model of instruction. To this end, 60 EFL learners studying at an accredited private language institute in Isfahan were first conveniently sampled and were homogenized through a sample of PET. 50 EFL learners within age range of 19 to 25 were selected for the study and equally assigned into two groups-experimental and group. A researcher-made reading comprehension test was given to the participants as the pretest of the study. The experimental group received flipped model of instruction, whereas the control group received traditional model of instruction. At the end of the study, the researcher-made reading comprehension test was administered to the two groups of the study as their posttest. Moreover, in order to identify the EFL students’ attitude towards the flipped model of instruction, the participants were asked to complete a questionnaire on flipped model of instruction developed primarily by Elfatah and Ahmed (2016). The results of ANCOVA revealed that flipped model of instruction had a significant positive effect on the reading comprehension ability of EFL students. Moreover, the results of frequency analyses indicated that EFL students in the experimental group had positive attitude towards attitude flipped model of instruction and agreed that it was helpful to them in many ways. The results and implications of the study are discussed in more detail in the paper.

Rheological Characterization and Thermal Stability of Different Intrinsic Viscosity Poly(ethylene terephthalate) in Air and Nitrogen

Abstract Four PET samples of different intrinsic viscosity values based on diverse manufacturing processes were characterized for their linear viscoelasticity using a parallel plate rheometer. Thermal stability and frequency sweep experiments were performed in the melt state at 270 °C. The influences of drying temperature, testing atmosphere (air or nitrogen), and preparation (granules vs. samples cut from compression molded sheets) were investigated. Results indicated that a higher drying temperature promoted complex viscosity significantly and compression molded sheets generated irreversible structural changes in harsh conditions. The samples measured in air decreased because of thermo-oxidation degradation, whereas that in nitrogen unexpectedly increased slightly because of polycondensation without surface renewal. The role of carboxyl end group towards PET thermal stability was found to be influenced by the atmosphere.

Effects of Bending Radii on the Characteristics of Flexible Organic Solar Cells Investigated by Impedance Analysis.

Flexible organic solar cells (OSCs) were fabricated on an indium-tin-oxide (ITO)/poly(ethylene terephthalate) (PET) substrate and were subjected to bending tests with various bending radii. We observed that the photovoltaic properties of the OSCs precipitously deteriorated at a bending radius ≤ 0.75 cm. In order to investigate the effects of the bending test, the changes in the surface morphology and the sheet resistance of the ITO-coated PET samples were investigated, and the photovoltaic properties of bent and unbent OSCs were evaluated. Thereafter, equivalent circuits for the OSCs were assumed and the change in their parameters, such as resistance and capacitance, was observed.

Influence of contact pressure and sliding speed on the temperature and coefficient of friction in sliding contact between two PET samples

Original scientific paper The use of polymeric materials has been growing steadily. A more extensive use of polymers as bearing materials will be made possible by a better knowledge of the properties of particular materials and their compatibility in a particular application. Poly(ethylene terephthalate) (PET) with the addition of Polytetrafluorethylene (PTFE) shows potential for being used as a material for machine parts rotating at lower loads due to its good ratio between manufacturing costs and mechanical properties. The use of PET in a PET/PET combination has been tested in three working points, with a lubricant applied once in each run and with three different values of sliding speed and of load. The change in temperature which occurs in the vicinity of the outlet zone of the contact at the end of the sliding path after 9 hour operation is presented. The applied method and temperature measurement are explained. The distribution of obtained maximum and average temperatures in the load range 9 ÷ 18 MPa and the sliding speed range 0,8 ÷ 2 m/s is shown for single working points. In addition, the effects of lubricant application on the increase in the magnitude of the load carrying capacity and on the decrease in the value of friction coefficient are shown in comparison with the reference values of temperature and friction coefficient in the dry contact operation.

Chain extension of virgin and recycled poly(ethylene terephthalate): Effect of processing conditions and reprocessing

Poly (ethylene terephthalate) (PET) is widely used in several segments of the plastic industry and PET-based products are extensively recycled. However, PET degrades during processing and use, which results in a decrease of molar mass and reduction of the material's performance. Degradation particularly affects recycled materials, subjected to repeated processing and use cycles, this limiting the applications of recycled PET. Chain extender additives rejoin polymer chain segments, compensate molar mass reduction due to degradation, and may be used to further increase molar mass. In the present work, an epoxidic multifunctional oligomer (Joncryl), recommended for use with condensation polymers was tested for chain extension of virgin and recycled PET. Molar mass decrease (degradation) or increase (chain extension) during processing in a laboratory internal mixer may be related to torque and temperature variations reported by the instrument. Here molar changes during processing were considered in terms of the chain extension additive concentration (0–1.5%) and the nominal rotor speed (30 rpm–120 rpm) in samples of bottle-grade virgin PET and postconsumer recycled PET. It was found that the molar mass changes depend strongly on additive content; 0.5% and 1.0% chain extender levels were sufficient to compensate the mild degradation observed in unadditivated samples. Reprocessing tests, with and without further additivation, showed that extra additivated PET (1.5% additive concentration) preserves chain extension capabilities to sustain reprocessing without molar mass decrease. The procedure adopted allows inline testing of additive effectiveness.

Structural and electric surface characteristics of heavy ion tracks in poly(ethylene terephthalate) and mica

The entry of high-energy Kr, Xe, and Bi ions into the surface of poly(ethylene terephthalate) (PET) and mica has been imaged. It has been shown that the track images have the shape of protuberances in both cases. The formation of protuberances is associated with the degradation of the material in the track region, in the formation of an amorphous structure, and the release of low-molecular radiolysis products as gaseous compounds. Holding the irradiated PET samples in water and dilute alkaline solution for several hours changes the surface topography due to hydrolysis of the material and escape of the radiolysis products to the solution. The kinetics of track etching in the dilute alkaline solution and pore formation have been studied. The electrical resistance and the permeability of the tracks in KCl, LiCl, MgCl2, and BaCl2 electrolytes have been measured.

Simplified Modeling of Convection and Radiation Heat Transfer during Infrared Heating of PET Sheets and Preforms

Abstract Initial heating conditions and temperature effects have an important influence during the injection stretch blow molding process of PET preforms. The paper provides a simplified modeling of the infrared (IR) flux provided by the IR lamps and the convection heat transfer with air, for the finite element simulation of the heating of PET samples. This modeling enables fast thermal simulations in industrial context. First, a complete 2D simulation of the air convection around a PET sheet sample is conducted using ANSYS/FLUENT to compute the local convection heat transfer coefficient. The distribution of this coefficient along the PET wall is then interpolated by a best linear fit function of the wall position to provide the boundary condition of the convection heat transfer thereafter. This boundary condition, coupled with the calculation of the infrared flux absorbed by the PET sheet sample, allows a 3D calculation of the time evolution of the sample temperature. This calculation is validated by comparing the experimental temperature distribution of the PET sheet obtained from an IR camera with the numerical results of the simulation. Second, we focus on the modeling of the heating of a cylindrical PET preforms by IR lamps. In our approach, the IR heating flux is calculated using the spectral and surfaceto-surface radiation laws adapted to the sample geometry. The air convection effect around the preform is modeled using the heat transfer coefficient identified from the 2D plane sheet case. It is applied on the boundaries of a simpler model in Comsol where only the preform is meshed. The temperature distribution on the outer surface of the preform is compared to experimental measurements by thermal imaging. A good agreement is observed which validates the whole approach used.

Poly(ethylene terephthalate) synthesis catalysed by chelated Sn, Zn and Mg complexes

A series of four C,N‐chelated diorganotin(IV) compounds, namely (LCN)2Sn(OCH2CH2O) (1), [LCNBuSn(OCH2CH2O)]2 (2), (LCN)2Sn(1,2‐(O)2‐3,5‐tBu2C6H2) (3) and [LCNBuSn(1,2‐(O)2‐3,5‐tBu2C6H2)]2 (4) (LCN = 2‐(Me2NCH2)C6H4), one zinc species, namely LNOZnEt (5) (LNO = [2‐(MeO)C6H4]NC(Me)C(H)C(Me)O), and one magnesium complex, namely [LNNMg]6 (6), (LNN = [2‐(Me2NCH2)C6H4]N), were used as catalysts for the synthesis of poly(ethylene terephthalate) (PET) from dimethyl terephthalate and ethylene glycol. Prepared PET samples were primarily characterized using the size exclusion chromatography technique. The highest number‐average molar mass of prepared PET samples reached 10.7 kg mol−1. Novel dimeric compound 2 was structurally characterized using both multinuclear NMR spectroscopy and X‐ray diffraction analysis. In addition, an alternative synthesis of 1 is described. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of CO2on Mesomorphic Structure of Cold-Drawn Poly(ethylene therephthalate) Fibers by Dynamic Mechanical Analysis

Dynamic mechanical analysis (DMA) provides interesting information about the dynamic viscoelastic properties and molecular scale motions. This article presents the results of an investigation into the effects of draw ratio and supercritical CO2 (scCO2) exposure on structural changes and mesomorphic transitions in cold-drawn poly(ethylene terephthalate) (PET) fibers by focus on DMA. Samples of partially oriented yarn PET fibers were uniaxially drawn below the glass transition temperature (Tg) using various draw ratios to obtain filaments with different structures for subsequent exposure to scCO2 in the presence and absence of tension at a temperature of 80°C and under a pressure of 220 bar. Microstructural investigation of the samples was carried out by combining the results obtained from DMA, differential scanning calorimetry, as well as density and birefringence measurements, all of which exhibited a good correlation. The rigid amorphous region in the PET samples was considered for interpreting structure–property relations. Results showed that increasing draw ratio leads to increased values of rigid amorphous regions and distribution of molecular orientation in the amorphous regions followed by an increase in the relaxation time distribution. Depending on sample conditions, exposure to scCO2 was found to have a strong effect on the transformation of the transient structure into crystalline or amorphous regions. PET fibers exposed to scCO2 under tension yielded higher values of crystallinity and orientation compared to those under no tension. In the case of PET fibers exposed to scCO2 under no tension, CO2 molecules released from the structure possibly caused a metastable structure to form in the amorphous phase. Therefore, rearrangement of molecular chains during the dynamic mechanical test in the temperature sweep mode is expected to increase the storage modulus of the sample before its glass transition temperature is reached. As a result, an increment is observed in the storage modulus of samples exposed to scCO2 without tension that can be related to the release of stress stored during the depressurization process. scCO2 exposure can be, therefore, claimed to be an environmentally friendly method for inducing structural changes and enhancing crystallinity in PET samples.

Determination of antimony in pet containers by direct analysis of solid samples using graphite furnace atomic absorption spectrometry and leaching studies

The main goal of this work was to determine antimony in different PET samples and evaluate its leaching from PET containers to beverages and simulant solutions. For this purpose, an analytical method was developed for the determination of Sb in PET samples using direct analysis by graphite furnace atomic absorption spectrometry (GF AAS). The concentration of Sb in PET samples ranged between 194 and 323mgkg−1 and the relative standard deviations were lower than 10%. Leaching tests have been carried out with 3% acetic acid solution, red wine and soft drink. These liquids were kept into the PET containers for 10days, under heating at 40°C. Antimony was determined in these solutions by GF AAS using an optimized analytical method for liquid samples; the LOD and LOQ for this method were, respectively, 1.0 and 3.7μgL−1, which are below the maximum limit of Sb established by international legislations. The Sb content in all solutions, after 10days of storage, was below the LOD, indicating that there was no significant leaching of the Sb from the PET containers to the different liquids.

Effect of γ‐irradiation on glycolysis of PET waste and preparation of ecofriendly coatings using bio‐based and recycled materials

Recycling of postconsumer poly (ethylene terephthalate) (PET) is a worldwide concern due to large increasing volume of these materials produced by society. In the present study, we report the effect of gamma irradiation on degradation of PET and its subsequent effect on glycolysis by using excess ethylene glycol (EG). The results as analyzed by molecular weight determination showed that extent of depolymerization of PET were dose dependent. The doses of 30, 50, 70, and 100 kGy resulted in decrease in the molecular weight by about 15%, 25%, 30%, and 40% respectively. The irradiated waste PET samples were further subjected to glycolysis using EG by conventional and microwave method which resulted in increased yield of monomeric product, bis (2‐hydroxyethylterephthalate) (BHET). The recycled material, BHET, was then used in combination with bio‐based monomers to prepare a new eco‐friendly polyester polyol which was analyzed for hydroxyl, saponification, acid value and further characterized by FTIR, 1HNMR, and GPC techniques for molecular weight determination. Polyurethane coatings were prepared from the polyester polyol and various commercial polyisocyanate curing agents. The coated films were evaluated for their performance properties. Thermal properties of coatings were investigated by differential scanning calorimetry and thermogravimetric analysis. POLYM. ENG. SCI., 55:2653–2660, 2015. © 2015 Society of Plastics Engineers

Influence of TiO2 nanoparticles on formation mechanism of PANI/TiO2 nanocomposite coating on PET fabric and its structural and electrical properties

Polyester fibers gained significant share from all other man-made fibers, but despite numerous advantages a characteristic static electricity generation is still seeking innovative solutions. In order to improve electrical properties of poly(ethyleneterephthalate) (PET) fabric, coating consisting of polyaniline/TiO2 (PANI/TiO2) nanocomposite was deposited on its surface. Coating was synthesized in acidic medium by the chemical oxidative polymerization of aniline with ammonium peroxydisulfate (APS) in the presence of colloidal TiO2 nanoparticles (d~4.5nm) and PET fabric. The morphology, molecular structure and dielectric properties of PANI/TiO2 nanocomposites were studied by scanning electron microscopy (SEM), Raman and dielectric spectroscopies. SEM analysis revealed the formation of non-uniform PANI coating on the reference PET sample. In contrast, uniform PANI/TiO2 coating on the surface of PET fabric was generated when TiO2 nanoparticles were engaged. The existence of conductive emeraldine salt form of PANI and phenazine units was confirmed by Raman spectroscopy. Formation mechanisms of PANI and PANI/TiO2 coatings on PET fabrics were proposed. The presence of TiO2 nanoparticles significantly affected the dielectric properties (permittivity and loss tangent) and AC conductivity of PANI/TiO2 coated PET fabrics. PET fabrics coated by PANI/TiO2 nanocomposite showed up to two orders of magnitude higher conductivity in the measured frequency region compared to PANI coated PET fabric.

Polymer Supported and Freestanding Transparent Electrodes Produced By Ink-Jet Printing and Electrodeposition

Transparent conductive electrodes play an important role in different applications, as thin-film solar cells, flat-panel displays and light emitting diodes1-3. With the increasing demand arising from flexible devices, mechanical properties of electrodes are becoming more and more important and alternatives to traditional materials are being investigated4,5. Doped metal oxides, e.g. ITO, are mostly used at the moment, but their main limitation derives from their ceramic nature that makes them brittle and therefore prone to cracking, when deposited on flexible substrates6. We studied the production of metallic micronets, with the aim of finding an alternative to ITO for transparent conductive electrodes. The use of metals, which are the materials owning the highest performances in terms of electrical conductivity, allows maintaining the desired level of transparency of the electrode, given by the optimization of the geometrical parameters of the micro-net. Both polymer supported and free standing metallic micronets were produced. To obtain the former structure, a conductive Ag pattern was printed on PET substrate using ink-jet printing (an example is shown in Figure 1), and then a copper layer can be grown by electrodeposition on the silver printed lines, to obtain the freestanding structure. Release of the metallic micro-net from the PET substrate is spontaneously obtained during the electrodeposition step. Electrical and optical properties of the produced electrodes were investigated. The free-standing metallic micro-net has resistivity two orders of magnitude lower than a commercially available sample of ITO-coated PET, while maintaining high transparency. Figure 1: SEM image of Ag pattern printed on PET substrate

Hydration structure and mobility of the water contained in poly(ethylene terephthalate).

We have studied the state of the water contained in poly(ethylene terephthalate) (PET), which consists of repeat units of OCC6H4COOCH2CH2O, in variously hydrated states. We first determined the hydration structure of the water therein not only from its OH stretching spectrum in a thinner sample but also from the hydration energy, the effect of the hydrogen bonding on the lengths of the donor and acceptor bonds, and the OH stretching frequencies of the water for the optimized 1:1 hydrate structures (quantum-chemically calculated). It has been found that the water bridges two ester C═O's in the manner of C═O···H-O-H···O═C therein and that about a 0.05 mole fraction of the C═O groups is bridged by the water in a PET sample hydrated in open air. We then carefully analyzed the state of the hydrating water in a thicker sample from its combination band around 5240 cm(-1), which significantly changes in frequency and bandwidth depending on the quantity of the contained water. It has been shown that the hydrating water molecules are so mobile as to begin to intermolecularly interact among themselves at a low hydration density of 10-15 water molecules per 1000 repeat units of OCC6H4COOCH2CH2O in the solid matrix.

The Preparation and Characterization of Branching Poly(ethylene terephthalate) and its Foaming Behavior

Chain extension was an effective method for increasing the molecular weight, the melt strength and the foaming property of linear polymer. In this paper, pyromellitic dianhydride (PMDA) was used as chain extender to improve these properties of linear poly (ethylene terephthalate) (PET). The intrinsic viscosity, rheological and thermal characterizations of various PET samples was investigated. The results demonstrated that the increasement of the viscoelasticity at low frequencies was correlated to the raise of the intrinsic viscosity and the formation of long chain branching. These structural changes resulted in the decreasement of the crystallization temperature and melt temperature as well as the increase in the cold crystallization values with the increasing content of PMDA. The cellular morphology and expansion ratio of CEPET foams were also obviously improved by the introduction of PMDA. The expansion ratio of CEPET foam with the PMDA content of 1.0 phr would reach 31.78. In addition, the effect of the chain extension reaction time on the intrinsic viscosity, the rheological behavior, and foaming properties of PET were also studied. The results showed that the intrinsic viscosity, the rheological behavior, and the foamability of CEPET also decreased gradually with increasing chain extension reaction time, which should be attributed to the occurrence of more and more intense thermal degradation.

Introduction of Atmospheric Pressure Plasma to Aqueous Detergent Processes.

The effects of exposure of polymer surfaces to atmospheric pressure plasma (APP) on detergency were investigated from the viewpoint of pretreatment to cleaning in aqueous systems using three PET substrates: film, mesh, and fabric. The PET substrates were soiled with stearic acid as a model oily contaminant, and were treated with the APP jet immediately before cleaning. Stir washing in aqueous solutions with and without alkali or anionic surfactant was performed, and then the detergency was evaluated from the microscopic image analysis or surface reflectance measurement. For all PET samples and detergent solutions, APP exposure was found to promote the removal of stearic acid. Contact angle measurements showed that APP exposure enhanced the hydrophilicity of PET and stearic acid. The increase in the surface oxygen concentration on PET and stearic acid due to the APP exposure was also observed by XPS analysis. The simultaneous oxidation of the PET substrate and stearic acid soil by the APP pretreatment resulted in detergency improvement via surface hydrophilization. Furthermore, microscopic observations suggested that the collapse of crystallized stearic acid deposited on the PET substrate by APP heating facilitated its removal. In situ detergency evaluation by a quartz crystal microbalance technique confirmed that the removal of stearic acid from the PET substrate was promoted by the APP exposure. The experimental findings of this study demonstrate the effectiveness of the APP exposure before cleaning in aqueous solutions.

Effect of drawing temperature on the structure and free volume of semicrystalline polyester yarns

Supercritical carbon dioxide (scCO2), an environmentally friendly solvent, can change the fine structure of fibers depending on treatment temperature and pressure. This article presents the results of an investigation into the effects of drawing temperature, scCO2 exposure and tension on structural changes, and mesomorphic transitions in partially oriented yarn (POY) and oriented poly(ethylene terephthalate) (PET) yarns. Samples of POY and PET yarns were uniaxially drawn at different temperatures to obtain filaments with different structures for subsequent exposure to scCO2 in the presence and absence of tension at a temperature of 80oC and under a pressure of 220 bar. Structural investigation of the samples was performed by combining the results obtained from differential scanning calorimetry, Fourier transform infrared, mechanical deformation, and density and birefringence measurements, all of which exhibited a good correlation. The fractional free volume in the PET samples was considered for interpreting structure–property relations. Results showed that the development of a transient structure strongly depends on process temperature and that for an identical draw ratio, PET yarns drawn at 23oC are significantly more oriented than those drawn at 68oC. Two crystallization mechanisms, that is strain-induced and thermal-induced crystallization, are involved that are frequently used to explain the structural changes during yarn deformation at different temperatures. The degree of crystallinity and orientation factors for PET yarns does not proportionally increase with increasing temperature of the drawing process; indeed, the highest value is obtained at a temperature of 100oC, whereas the lowest is observed at a temperature of 68oC, which is near the glass transition temperature. Tension under scCO2 exposure also produces significant effects in term of causing structural changes. POLYM. ENG. SCI., 55:2030–2041, 2015. © 2014 Society of Plastics Engineers

Molecular detection of E. granulosus sheep strain (G1) infections in naturally infected dogs in Punjab (India)

Abstract Echinococcosis is a preventable but neglected zoonosis in India. Although the disease in domestic animals is usually asymptomatic, huge economic losses have been reported due to cystic echinococcosis in livestock in India. The molecular characterization of Echinococcus from dog populations has not been previously carried out in Punjab (India). A total of 237 pet and stray dog faecal samples were collected and examined for the presence of eggs of the Taeniidae family in Punjab (India). A 255 base pair fragment of the mitochondrial 12S rRNA gene was amplified and the presence of sheep strain (G1) of E. granulosus has been reported. We detected eggs of the Taeniidae family in 2.11 per cent of the faecal samples. High prevalence was recorded in stray dogs (9.52 %) living near slaughter shops/post mortem areas. The prevalence of E. granulosus sheep strain (G1) using PCR was found to be 0.84 per cent in naturally infected dogs. This is the first study confirming the presence of E. granulosus (G1) sheep strain in dogs in Punjab (India). The results reveal the presence of sheep strain of E. granulosus and demand implementation of Animal Birth Control programme so as to control the stray dog population of the country.