PET Samples Research Articles

Reactive Modification of Poly(ethylene terephthalate) and its Foaming Behavior

A methodology for the preparation of chain extended poly (ethylene terephthalate) (PET) and its foams by autoclave batching foaming method was proposed. First, PET was mixed with tetraglycidyl diamino diphenyl methane (TGDDM) as chain extender to generate the branching/crosslinking molecular structure and improve the viscoelasticity of PET. Then, PET foams were prepared using supercritical CO2 as physical blowing agent. The molecular structures of various PET samples were characterized by the nuclear magnetic resonance, gelation degree and crosslinking density test. The results showed that with the introduction of TGDDM, the branching/crosslinking structure of PET appeared. The influences of various molecular structures on the thermal property and rheology of PET were also studied. The results showed that the crystallization temperature, crystallization rate, and crystallinity of various PET samples decreased with the content of TGDDM, but the modified PET had higher melt elasticity than that of pure PET. PET foam with the addition of 0.4% TGDDM had finer cellular morphology and the highest expansion ratio.

Temperature dependence of the rigid amorphous fraction in poly(ethylene terephthalate)

The analysis of the cp melting curve of poly(ethylene terephthalate) (PET) after non-isothermal crystallization, according to a three-phase enthalpy-based procedure, has allowed to monitor the correct crystalline and rigid amorphous fractions evolution during fusion at low heating rate and to identify the temperature of complete mobilization of the rigid amorphous fraction, located in the proximity of 215°C. This limit temperature for the disappearance of the rigid amorphous fraction in PET corresponds to the transition between the triple and the double melting behaviour displayed by PET after isothermal crystallization. The multiple melting behaviour of PET is usually attributed to the fusion of original crystals recrystallized during the heating at conventional scanning rate, and to the presence of dual lamellar stacks. In the present study, PET was isothermally crystallized at various temperatures (Tc) ranging from 185°C to 225°C, and the double and triple melting profile that is observed at conventional DSC heating rates, after isothermal crystallization at Tc higher and lower than 215°C respectively, has been put in relation with the absence and the presence of RAF around the original crystal lamellae. All the experimental evidences here reported indicate that the critical temperature for the formation and the disappearance of the rigid amorphous fraction in the PET sample analyzed in the present study at conventional DSC scanning rates, is around 215°C.

Vertical wicking behavior of knitted fabrics

Wicking describes the liquid transport behavior of fibrous assemblies and plays an important role in deciding the comfort characteristics of fabrics. The present manuscript describes the vertical wicking behavior of different knitted fabrics. The wicking measurement has been done using a prototype based on capacitance principle. The developed prototype is capable of measuring the rate and amount of liquid transport more precisely during wicking. Several weft knitted double jersey fabrics were produced using V-bed machine by changing material and machine parameters. Many variables, i.e., fiber type, machine gauge, number of yarn feed and presence of elastomeric yarn, were chosen for the experimental design. It has been found that these factors significantly affect the wicking in fabrics. Fabrics made up of cotton or viscose yarns were showing lower wicking rate compared to PET samples (p<0.01). The rate and amount of water rise also decreases for the fabric samples produced with increasing the machine gauge and the number of yarn feed in the V-bed machine (p<0.01). Incorporating elastomeric yarn in the knitted structure make the fabric structure relatively tighter and offer more drag to the water rise, and hence show poor wicking characteristics. The developed prototype could be further used to examine the influence of several other factors of the fabric structure on the wicking behaviour.

Comparative in situ PET biodegradation assay using indigenously developed consortia

A soil burial test was carried out to evaluate the biodegradation of polyethylene terephthalate under natural environment for a period of six months in presence of three different indigenously developed bacterial consortia. These consortia comprised of potential polymer-degrading bacterial cultures isolated from various waste disposal sites. The comparative biodegradation of PET samples in presence and absence of used consortia was monitored through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). FTIR analysis implies structural changes in biodegraded PET samples unlike the control. The biodegradation is further substantiated by SEM which manifested the development of fissures and a sign of significant erosions which were progressive with the incubation time. Moreover, the DSC showed lowering of melting temperature (Tm) and heat of fusion (ΔHf) of biodegraded film samples suggesting their increased brittleness.

Quantification of Colour Formation in PET Depending on SSP Residence Time, Temperature, and Oxygen Concentration

SummaryA systematic approach was carried out to quantify the discolouration of different poly(ethylene terephthalate) (PET) samples such as virgin bottle‐grade resins, bottle‐to‐bottle recycled chips, and bottle‐to‐bottle recycled flakes. The PET samples were treated in a fixed bed reactor in the solid‐state. The possible influencing parameters such as residence time, temperature, and oxygen partial pressure were studied by analysing the CIELAB b*‐coordinate (axis = yellow to blue) with a spectrophotometer at the end of the experiment. The PET samples were analysed once as chips respectively flakes retained from the experiments and again as plates obtained from a following standardised melting procedure. The combination of experiments and literature review results in the proposal of different discolouration mechanisms, which are influenced by temperature, residence time, and oxygen concentration. Using the design of experiments (DoE) approach, a mathematical model was compiled that can be used to predict the yellowing of the different PET grades.

Dependence of conformational relaxation on nanoconfinement in semicrystalline poly(ethylene terephthalate)

Novel aspects concerning the micromechanical response of amorphous regions confined by crystals in nano-sized domains are illustrated for semicrystalline poly(ethylene terephthalate) (PET), on the basis of microindentation hardness and dynamical mechanical spectroscopy (DMS) analyses (10-3÷60 Hz frequency range for DMS). PET samples were crystallized from the glassy state at low and high temperatures (Tc=100°C and 160°C, respectively) and subsequently recrystallized some degrees above to gain information on the nature of the amorphous regions. DMS at 95°C reveals two segmental relaxation processes ascribed to the interlamellar amorphous regions (slow mode) and to the interstack amorphous pockets (APs) (fast mode) respectively, the latter being the object of the present study. It is shown that recrystallization changes the cooperativity within the APs. At low Tc, an increase in the cooperativity and the free energy barrier for readjustment is found after recrystallization. Room temperature indentation measurements reveal an enhancement of the average hardness value of the amorphous regions, Ha, on samples recrystallized a few degrees above Tc=100°C. The reduced size of the APs regions upon recrystallization is discussed as a relevant parameter giving rise to an enhanced segmental confinement and a parallel hardening. Results for the high Tc material reveal that, in this case, both the cooperativity (measured at 95°C) and Ha (measured at room temperature) decrease upon recrystallization. The influence of the coupling of the APs with the crystal walls, on the relaxation mode and in turn on the mechanical behavior of the material, is envisaged to be a possible mechanism underlying these observations.

Outdoor weathering of polyamide and polyester ropes used in fall arrest equipment

ABSTRACTIn this work, the effect of natural climatic aging on two ropes made from polyamide 6 (PA6) and poly(ethylene terephthalate) (PET) was evaluated. Samples of rope from both materials underwent a continuous outdoor aging treatment spanning 6 months in Montreal's weather. Tensile tests carried out on aged PA6 ropes showed an increase in ultimate strain and a decrease in breaking force when compared with as‐received values, while PET ropes exhibited a slight increase in ultimate strain as their breaking force remained unchanged. FTIR analyses of aged PET samples revealed a new absorption band in the hydroxyl region ascribed to the OH stretching vibrations of carboxylic acid end groups. FTIR quantitative analyses of the absorption bands in the carbonyl region of aged PA6 spectra displayed an increase in intensity that indicates the occurrence of chemical degradation reactions. The degree of crystallinity of PA6, calculated from differential scanning calorimetry data, was found to increase after the weathering treatment, a result confirmed by X‐ray diffraction analyses. The higher crystalline fraction is believed to entail an increase in the density of PA6 fibers, which give rise to the length reduction seen in PA6 ropes after the aging treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3058–3065, 2013

Substitution of Reduction Clearing Step by Ozone Treatment at Disperse Dyeing of Polyester

The effectiveness of ozone treatment for the afterclearing of disperse dyed poly (ethylene terephthalate) (PET) fibers has been examined. Two types of disperse dyed PET samples were selected among commercial mass production range of Akbaslar textile mill. The reduction clearing procedure applied during mass production was taken as the reference reduction clearing treatment; these reference samples were taken after dyeing and reduction clearing processes at the mill. Samples of disperse dyed PET were also taken before reduction clearing in order apply ozone treatment in the laboratory as the tested afterclearing method. Color and wash-fastness properties of the reduction cleared and ozone treated fabric samples were compared and reported. Results indicated acceptable color and wash-fastness results comparable to those of reduction cleared samples for ozone treated samples. The success of ozone treatment for the black dyed PET sample at 7.0% depth of shade was especially outstanding. Ozone treatment was applied in cold water without addition of any chemicals for very short treatment times when compared to conventional reduction clearing. Ozone treatment created substantial energy and chemical savings as well as lower environmental impact.

Analysis of recycled PET bottles products by pyrolysis-gas chromatography

The impact of the contaminants in post used PET bottles on the decomposition of polymer itself after recycling process was analyzed. For that reason sorption experiments of harmful substances to PET bottles were performed. In order to monitor the presence of contaminants in recycled PET and evolution of thermal decomposition products of samples: virgin PET, contaminated PET flakes (PET K) and recycled PET (PET RM) were studied. The thermal degradation products of PET were achieved by pyrolysis using Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS), temperature-programmed evolved gas analysis-mass spectrometry (EGA-MS) and thermogravimetric analysis (TGA). Reactive pyrolysis with tetramethyl ammonium hydroxide (TMAH) was also performed to gather additional information about degradation products in studied samples. The pyrolysis products analysis of the studied PET samples indicate some changes in decomposition mechanism of PET samples that pass through contamination process due to some diversity in their chemical and structural composition.

Effects of tension on mesomorphic transitions and mechanical properties of oriented poly(ethylene terephthalate) fibers under supercritical CO2 exposure

Samples of partially oriented yarn PET fibers were uniaxially drawn below the glass transition temperature (cold-drawing) before exposure to supercritical carbon dioxide (scCO2) in the absence and presence of tension at a temperature of 80 °C and a pressure of 220 bar. The effects of draw ratio, scCO2 exposure, and tension on structural changes and on mechanical properties in particular were investigated using differential scanning calorimetry, tensile deformation, and birefringence and density measurements. A good correlation was obtained among the results obtained from various techniques. Results indicate that exposure to scCO2 not only induces structural changes but also develops crystallization in the samples. Tension under scCO2 exposure also produces significant effects in terms of causing structural changes and transforming the oriented chains in the mesophase into the crystalline or noncrystalline domains. PET fibers exposed to scCO2 under no tension yields lower values of crystallinity, orientation, tenacity, and Young’s modulus but higher values of breaking elongation compared to samples exposed under tension. This is an indication of higher plasticity of the chains in the amorphous domains in samples exposed under no tension. It is also found that mechanical measurements confirm the structural changes taking place in exposed PET samples.

직물의 β-cyclodextrin 가공에 따른 휘발성 유기성분의 흡착과 제거

Clothes that retain and emanate body odor feel uncomfortable and unclean; subsequently, the adsorption, desorption and removal amounts of malodorous compounds from fabrics with different polarities were examined. 1-Octen-3-one, octanal and isovaleric acid, which are important malodor compounds from the body, were used as volatile organic compounds (VOC). Samples were prepared with unfinished and <TEX>${\beta}$</TEX>-CD finished cotton, nylon and PET fabrics. The amounts of VOCs retained on the fabrics were measured using headspace GC-MS; in addition, the odor intensity of the samples were evaluated by 10 trained panelists. The amounts adsorbed were estimated by weight gain; however, moisture was found to have a larger effect on the increase in weight than VOCs. The polarity of the VOCs decreased in the order of isovaleric acid, octanal and 1-octen-3-one. Despite the exceptionally large amounts of octanal adsorbed on the nylon sample, the amounts of malodorous compounds adsorbed on fabrics increased with the decreasing VOC molecular weight. The unfinished PET sample adsorbed more VOCs than the unfinished-fabric samples. The odor intensity was mostly weaker in the <TEX>${\beta}$</TEX>-CD finished fabrics than in the unfinished fabrics. The odor intensity of the <TEX>${\beta}$</TEX>-CD finished fabrics was lower than unfinished fabrics. The amount of VOCs that remained on the soiled fabric samples after storing in air for 24 hrs decreased with the increasing VOC vapor pressure. Most VOCs were removed by washing; however, more VOCs were left on the <TEX>${\beta}$</TEX>-CD finished fabrics than unfinished fabrics. The intensity of the odor from the unfinished PET and <TEX>${\beta}$</TEX>-CD finished fabrics was stronger and weaker, respectively, than that of other fabrics, even when the same amounts of VOCs remained.

Migration of antimony from PET trays into food simulant and food: determination of Arrhenius parameters and comparison of predicted and measured migration data

Migration experiments with small sheets cut out from ovenable PET trays were performed in two-sided contact with 3% acetic acid as food simulant at various temperatures. The fraction of diffusible antimony (Sb) was estimated to be 62% in the PET sample under study. Apparent diffusion coefficients of Sb in PET trays were determined experimentally. Measurement of migration between 20 and 150°C yielded a linear Arrhenius plot over a wide temperature range from which the activation energy (E a) of 188 ± 36 kJ mol−1 and the pre-exponential factor (D 0) of 3.6 × 1014 cm2 s−1 were determined for diffusing Sb species. E a was similar to previously reported values for PET bottles obtained with a different experimental approach. E a and D 0 were applied as model parameters in migration modelling software for predicting the Sb transfer in real food. Ready meals intended for preparation in a baking oven were heated in the PET trays under study and the actual Sb migration into the food phase was measured by isotope dilution ICP-MS. It was shown that the predictive modelling reproduces correctly experimental data.

Surface modification of PET polymers by using atmospheric-pressure air brush-shape plasma for biomedical applications

In this study, we report a method to generate a reliable and homogeneous brush-shape air plasma plume at atmospheric pressure for surface modification of PET polymers and biomedical applications. The room-temperature air plasma plume consists of well-aligned and stable microplasma jets formed in the vicinity of the ends of hollow optical fibers at atmospheric pressure. This plasma plume may lead to the uniform and large-area surface modification of PET polymers. The plasma plume may efficiently prevent the heat-sensitive polymers from being damaged and significantly affect the surface properties of treated polymers, such as surface chemical compositions, hydrophobicity and biocompatibility. Compared to a high density of blood platelets adhering onto the untreated PET sample, no adhesion of blood platelets is observed on the plasma-activated PET sample due to the surface functionalization. The reaction processes of plasma-activated species at the surface of treated polymers are discussed based on the obtained experimental results.

PET高速溶融紡糸過程のオンライン広角X線散乱測定

We report results of on-line wide-angle X-ray scattering (WAXS) measurements for melt spinning process of poly(ethylene terephthalate) (PET). In order to obtain good results, we have conducted experiments by paying attention as much as possible. First of all, a special experimental set-up has been developed by employing a purge box which contains the spin line and the X-ray detector (imaging plate), as well, with helium gas purge, in order to minimize noise level due to air scattering. Furthermore, a high-molecular weight PET sample prepared by solid-state polymerization was used in order to increase the spin line stress, which accommodates us with starting of orientation-induced crystallization at low take-up velocities. A special care to minimize the swaying of the spin line has been taken as well by employing a perforated metal guard inside the spinning tube which covers the spin line from the spinneret to the winder with insertion of the helium gas purge box in the middle. This worked well for suppression of the air turbulence. By such special experimental treatments, we have succeeded in conducting on-line two-dimensional WAXS measurements during the high speed melt spinning of PET fibers with the take-up velocity of 1600m/min. As a high brilliant X-ray source, we utilized SPring-8 (Japan Synchrotron Radiation Research Institute, Harima, Japan). The combination of above mentioned techniques enabled us to obtain crystalline reflections from oriented crystals with only 2min exposure. Nevertheless, we observed no appreciable change in crystallinity and orientation of crystallites along the spin line. It is because the control of positioning the neck point where the crystallization sets in was sensitively influenced by the ambient gas condition. Further special care to overcome this difficulty should be taken in our future study.

Study of Weathering Effect, and the Solution on the Diffusion Coefficient of the PET, Mineral Water, and Al-Badawi Vinegar Bottles samples

The aim of this work is to study the absorptive properties of PET, and bottle material samples for mineral water and black and white Al-Badawi vinegar (acidic acid (CH3COOH)). PET samples were prepared by extrusion method, and take the bottle samples from the bottles, which are used as a container to save it. The fundamental reason for the permeability of polymers is their relatively high level of molecular motion. Since two different solutions were used to evaluate the diffusion behavior of specimens. By using mineral water for two kinds of specimen (PET, and samples of the bottle material at three conditions ((1)-indoor,(2)- in refrigerator, and(3)-outdoor) to study the weathering effect on polymer absorptive involved. It was found that PET-3(out door) was the most water absorbing polymer. It was attributed to free radical induced by the photo degradation, and the PET-2, and bottle samples (2-in refrigerator) were the lowest, which attributed to the thermal and photo degradation for the out door condition, whereas the lowest for the samples(2-in refrigerator). It was attributed to the freezing free radical in polymer of the lowest effect, so the weight gain will be the lowest. The diffusion coefficient of the bottle samples (2-in refrigerator) was of the lowest value (previous reasons), and also attributed to the bottle sample material (PET+ Additives (as stabilizers)), which caused in decreasing in thermal, and photo degradation effects.By using acidic acid at different concentration (4.6%, 6.4, and 100% of CH3COOH)) as black, and white Al-badawi vinegar, and pure acidic acid. It was found increasing in absorptive with increasing of CH3COOH concentration, so the best absorptive for the highest concentration (100%) for two samples (PET, and bottle samples). CH3COOH had a deterioration effect. This effect had led to formation of voids and gaps, beside the ones originated in the specimens during manufacturing and processing stages, and these gaps would be filled with the solutions, leading to an increase in weight. It was concluded that the diffusion coefficient was very low for all samples and in all solutions of order less than 10-14m2/sec , so it was recommended to use PET for manufacturing the bottle(container) to save the solutions(water, and acidic solution, because it was a good barrier for solutions.

A Study on Physical Aging of Semicrystalline Polyethylene Terephthalate below the Glass Transition Point

Physical aging of semicrystalline polyethylene terephthalate was studied using differential scanning calorimetry(DSC). PET samples with crystallinity content of 0.28 were aged at two different temperatures, 25 and 45°C. Thesamples were stored for several days and periodically tested using DSC method. The glass transition temperature forthe samples aged at 25°C was about 73-74°C, and the position and intensity of endothermic peaks wereapproximately constant. Higher glass transition of the samples aged at 45°C, 73-86°C, was attributed to the enthalpyrelaxation process of amorphous regions of semicrystalline PET. For the samples aged at 45°C, the endothermicpeaks shifted to higher temperatures with increasing aging time. The position of the endothermic peaks determined bythe temperature of the maximum, Tmax, tended to increase with aging time for samples aged at 45°C, and theintensity of the peaks continuously increased with time; however, the results showed that the aging of PET samples at45°C even after 120 days continued the enthalpic relaxation of semicrystalline PET and that the process could bestudied by DSC method. The results also showed that the aging process could affect the final degree of crystallinity ofc-PET samples and the samples stored at 45°C showed higher degree of crystallinity than the samples aged at 25°C.

Study of structural changes and mesomorphic transitions of oriented poly(ethylene therephthalate) fibers in supercritical CO2

Supercritical carbon dioxide (scCO2), an environmentally friendly solvent, can change the fine structure of fibers depending on treatment temperature and pressure. Samples of partially oriented yarn (POY) PET fibers were uniaxially drawn below the glass transition temperature (Tg) and then exposed to scCO2 under tension to induce morphological changes in them. The effects of draw ratio and scCO2 exposure on the structural changes and mesomorphic transitions were evaluated. For this purpose, thermal characteristics of the structure, especially the rearrangement of polymer chains in the amorphous phase induced by cold-drawing and exposure to scCO2, were evaluated by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). The orientation factor of the fibers was measured using a polarizing microscope. The paracrystalline portion and the crystallite sizes of exposed samples were estimated by wide-angle X-ray diffraction. To evaluate the solubility of CO2 molecules in the samples, density and fractional free volumes were also measured. A good correlation was obtained between the results obtained from various measurement techniques. Results showed that cold-drawing of PET fibers leads to a strain-induced crystallization and that exposure to scCO2 changes the structure of the oriented PET samples. To investigate mesophase transitions, percentage of extended chains in the amorphous regions was calculated by analyzing the results of DSC and FTIR. Results showed that the amount of extended chains developing during cold-drawing in the amorphous regions decreased when exposed to scCO2.

Comparison of biostability between poly(trimethylene terephthalate) filaments and PET for vascular prostheses when exposed to hydrolytic and enzymatic degradation

The purpose of this paper is to study the biostability of PTT samples as an implantable biomaterial. In this study accelerated hydrolytic and enzymatic degradation tests were performed on PTT filaments so as to predict the relative rates of in vivo biodegradation. PTT filaments were subjected to a highly alkaline environment (pH 13.5) for periods of up to 10 days, and to PBS buffer and neutral enzymatic papain solutions for up to 9 weeks. Changes in weight loss, surface appearance, filament diameter, thermal properties, infra-red spectrum and tensile modulus were monitored over these time periods. PET samples were also exposed to the same solutions as a comparison to PTT samples. The results show that PTT filaments are more stable in alkaline solution, but less stable in PBS neutral buffer and enzymatic papain environments compared to PET filaments. The decrease of tensile moduli of the degraded PTT samples confirms the decrease of crystallinity and conform change of the trimethylene glycol conformers during the degradation.

Chain Dynamics in Antiplasticized and Annealed Poly(ethylene terephthalate) Determined by Solid-State NMR and Correlated with Enhanced Barrier Properties

Using solid-state NMR, site-specific chain dynamics from the hertz to mid-kilohertz regime were examined in compression-molded films of poly(ethylene terephthalate) (PET), PET filled with 2 wt % acetanilide or phenacetin, and PET annealed below and above the glass transition temperature (Tg). More specifically, 13C relaxation time in the rotating frame, 1H–13C cross-polarization times, and 13C chemical-shift anisotropy exchange were measured at natural abundance. 13C CP/MAS spectra revealed that PET annealed above Tg was 28% crystalline, and all other PET samples were completely amorphous. Relaxation times in these polymers were analyzed using stretched exponentials which yielded characteristic time constants. The filled PET and PET annealed above Tg exhibited suppressed chain dynamics across the entire hertz to mid-kilohertz regime that were correlated with reduced CO2 and O2 permeabilities. Using the centerband-only detection of exchange (CODEX) sequence, the fraction of flipping phenylene rings was observed to decrease in these polymers, with the decrease in the semicrystalline sample consistent with the crystalline fraction.

Finite Element Analysis of Mechanical Behavior and Thermal Shrinkage of Poly(Ethylene-Terephthalate) (PET) Film in the Glass Transition Temperature Region

Finite element analysis has been performed based on a mechanical model proposed here to interpret the experimental data of stress-strain curves and thermal shrinkage behavior of poly(ethylene terephthalate) (PET) films observed in the temperature region near the glass transition point. The proposed mechanical model consists of a parallel array of hyper-elastic element and plastic deformation element. The former element was introduced to explain the thermal shrinkage above the glass transition temperature and the latter element was required to explain the permanent strain detected for the oriented PET sample. The numerical calculation was performed to give a good reproduction of the experimental data on the basis of explicit finite element method.