Asymmetric surface modification of poly(ethylene terephthalate) film by CF4 plasma immersion

Poly(ethylene terephthalate) (PET) films were treated with CF₄ plasma immersion. The samples were processed at different RF powers and treatment time. The surface modification of PET films was evaluated by water contact angle (CA), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Decrease in contact angle of both sides of PET films was observed under mild treatment conditions. However, as raising treatment power and/or time, the change in contact angle between the two sides of PET films was different. The relatively hydrophobic and hydrophilic surfaces were being in situ formed on the two sides of PET films, respectively. And the extreme values of water contact angle reached 108.63 and 7.56°, respectively. XPS analyses revealed that there was a substantial incorporation of fluorine and/or oxygen atoms in both side surfaces. The relative chemical composition of the C (ls) spectra's showed the incorporation of non-polar fluorine-based functionalities (i.e. CFCF_n, CF₂ or CF₃ groups) and polar oxygen-based functionalities (i.e. COOH or OH groups) in the surfaces. Correlation between the plasma parameters and the surface modification of PET films is also discussed.     

Electron induced modification in poly(ethylene terephthalate)

Abstract

The effect of 100 kGy dose of 2 MeV electron irradiation on Poly(ethylene terepthalate) (PET) has been studied by different characterisation techniques such as the Fourier transformed IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction analysis. Oxidative degradation leading to amorphisation of the polymer has been observed from spectral analysis. The thermal stability of the polymer was found to decrease due to electron irradiation. The thermal decomposition temperature as well as the melting temperature in case of irradiated PET was found to be decreased due to electron bombardment. A decrease in crystallinity of the polymer has also been observed after irradiation.     

Molecular dynamics simulation study on the structural properties of poly (ethylene terephthalate) under uniaxial extension and thermal shrinkage processes

In thermal shrinkage process for polyethylene terephthalate (PET) films, PET film is uniaxially stretched and then thermally relaxed. We investigate the effect of heat relaxation temperature on the thermal shrinkage of uniaxially stretched PET film using molecular dynamics simulation method. Through our investigation, we find that the thermal shrinkage ratio of the amorphous PET film is reduced as a function of heat relaxation temperature, whereas the skirt ratio is weakly correlated with the heat relaxation temperature, exhibiting the most negative skirt ratio in the case of the highest thermal shrinkage ratio. Our analysis on the PET film at molecular level further verifies that the trans-gauche transformation observed in ethylene glycol units during the simulated process is a driving force for the thermal shrinkage of uniaxially stretched PET systems.     

Electron beam induced modification of poly(ethylene terephthalate) films

Electron beam processing of poly(ethylene terephthalate) (PET) films is found to promote significant changes in the melting heat, intrinsic viscosity and polymer film-liquid (water, isooctane and toluene) boundary surface tension. These properties are featured with several maximums depending on the absorbed dose and correlating with the modification of PET surface functionality. Studies using adsorption of acid-base indicators and IR-spectroscopy revealed that the increase of PET surface hydrophilicity is determined by the oxidation of methylene and methyne groups. Electron beam treatment of PET films on the surface of N-vinylpyrrolidone aqueous solution provided graft copolymerization with this comonomer at optimum process parameters (energy 700 keV, current 1 mA, absorbed dose 50 kGy).     

Moisture barrier of AlxOy coating on poly(ethylene terephthalate), poly(ethylene naphthalate) and poly(carbonate) substrates

The moisture barrier property of Al_xO_y coated poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) (PEN) and poly(carbonate) (PC), have been investigated. The differences in the morphology of the Al_xO_y sputtered grown on these substrate were investigated using atomic force microscopy (AFM). The initial growth of the Al_xO_y followed closely the topology of the substrate and an amplified roughness was observed. In the fully grown Al_xO_y, the comparative roughness followed that of the substrates. It has been found that a single layer Al_xO_y improved the moisture barrier of PET by an order of magnitude, PC by two orders of magnitude while no improvement was observed for PEN. UV-ozone treatment on PC further improved the moisture barrier, while no improvement was observed for PET and PEN. The comparative effects of the substrate surface roughness and surface energy on the moisture barrier are discussed.     

Cold plasma-induced modification of the dyeing properties of poly(ethylene terephthalate) fibers

Surface modification of poly(ethylene terephthalate) (PET) fabrics induced by air radiofrequency (RF) plasma treatment has been investigated systematically as a function of plasma device parameters, to identify the plasma-polymer surface interactions prevailing under different operating conditions and leading to an increased color depth upon dyeing. Some tests have also been performed employing chemically inert argon as a feedstock gas. The dyeing properties of plasma-treated fibers were correlated to their topographical characteristics, determined by AFM analysis, and to their chemical surface composition, determined by XPS analysis, while the plasma-originated UV radiation was found to have no relevant effects in PET surface modification. The relative importance of plasma-induced surface processes, such as etching and grafting of polar species, is discussed in relation to their role in modifying PET dyeing properties.     

Investigation of structural relaxation and surface modification of ultrathin films of poly(ethylene terephthalate)

We studied dynamic properties of ultrathin films of poly(ethylene terephthalate) spincoated on different substrates, by means of dielectric spectroscopy and surface patterning experiments. We did not observe any variations of structural dielectric relaxation dynamics for films spincoated on aluminium substrate having thicknesses down to 40 nm. On the same substrate, 13 nm thick films are instead characterized by a reduction of the chains mobility. Surprisingly the chains dynamics as probed by a surface nanopatterning experiment evidenced a strong dependence on the substrate interaction even for 50 nm thick films, where dielectric relaxation dynamics is unaffected. It can be deduced that different length scales characterise dielectric relaxation dynamics and the processes related to the surface patterning, even if both are related to the chain mobility. Further experiments are wished to better understand this intriguing scenario.     

Ultrastructural observations of human epidermal melanocytes cultured on polyethylene terephthalate film

ObjectiveTo assess the application of polyethylene terephthalate film as a supporting material of cultured human epidermal melanocytes and to observe the ultrastructure of human epidermal melanocytes in vitro.MethodsHuman epidermal melanocytes were isolated from 7- to 14-years old children foreskins and were cultured in M254 culture medium containing human melanocyte growth supplement. Cultured melanocytes were purified via a differential trypsinization method. Purified melanocytes were cultured on a film and prepared for transmission electron microscopy.ResultsIn comparing with the cellular supporting materials polyvinylidene chloride and cellophane, human epidermal melanocytes only attached and grew on polyethylene terephthalate film. Melanocytes grown on polyethylene terephthalate film maintained an intact shape, and retained special ultrastructures characteristic of melanocytes such as dendrites.ConclusionsPolyethylene terephthalate film proved to be an ideal cellular supporting material for the cultivation of human epidermal melanocytes. Ultrastructure of melanocytes showed melanosomes are transferred both from the tip and middle section of dendrites.     

Structure-property and composition-property relationships for poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation

The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and I_D/I_G ratio and between chroma and I_D/I_G ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp² carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the I_D/I_G ratio and inverse correlations between surface energy and I_D/I_G ratio and between dispersive component of surface energy and I_D/I_G ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp² carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the π → π* shake-up satellite of the C 1s peak.     

Investigation of the surface of poly(ethylene terephthalate) films modified by vacuum ultraviolet irradiation in air

This paper reports on the results of measuring the changes in the characteristics of the surface of poly(ethylene terephthalate) films upon radiation-induced oxidation of the polymer under vacuum ultraviolet irradiation in an oxygen-containing medium. The films were irradiated by light from a sealed-off deuterium lamp with the maximum photon energy within the band (10 ±1 eV) in air under conditions where thermal destruction of poly(ethylene terephthalate) could be ignored. The functional relationship between the decrease in the film thickness and the growth of surface irregularities in the course of photoetching was established from measurements of the optical transmission spectra T (γ) of the films and investigations of the surface microrelief by atomic-force microscopy. The hydrophilic properties of the surface of the sample regions irradiated with different doses were examined by measuring the contact angle.     

Rheological,thermal, and mechanical properties of poly(ethylene naphthalate)/poly(ethylene terephthalate) blends

Structural, Theological, thermal, and mechanical properties of blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) obtained by melt blending were investigated using capillary rheometry, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) observation, tensile testing. X-ray diffraction, and ¹H nuclear magnetic resonance (NMR) measurements. The melt Theological behavior of the PEN/PET blends was very similar to that of the two parent polymers. The melt viscosity of the blends was between that of PEN and that of PET. Thermal properties and NMR measurement of the blends revealed that PEN is partially miscible with PET in the as molded blends, indicating that an interchange reaction occurs to some extent on melt processing. The blend of 50/50 PEN/PET was more difficult to crystallize compared with blends of other PEN/PET ratios. The blends, once melted during DSC measurements, almost never showed cold crystallization and subsequent melting and definitely exhibited a single glass transition temperature between those of PEN and PET during a reheating run. Improvement of the miscibility between PEN and PET with melting is mostly due to an increase in transesterification. The tensile modulus of the PEN/PET blend strands had a low value, reflecting amorphous structures of the blends, while tensile strength at the yield point increased linearly with increasing PEN content.     

Radiothermoluminescence of poly(tetra fluoroethylene) and poly(ethylene terephthalate) pretreated by xenon ions

Low-temperature (77–300 K) RadioThermoLuminescence (RTL) investigations of Poly(Tetra FluoroEthylene) (PTFE) and Poly(Ethylene TerePhthalate) (PET) foils previously treated by different flux (Φ = 10⁶–10¹¹ cm⁻²) of Xenon ions with energy 1.1 MeV/nucleon have been showed an essential ion-induced changes in RTL of the both polymers under study. In PET as well as in PTFE significant changes of RTL light yield observed at the ion flux more than 10⁹ cm⁻². Variation of RTL light yield in PTFE accompanied by appearance of new TL temperature maxima on the glow curve. An existence of correlation between observed changes of molecular mobility in ion-irradiated polymer and optical (PET) and strength (PTFE) properties have been found.     

Angle dependent laser nanopatterning of poly(ethylene terephthalate) surfaces

Interference effects can lead to the formation of ripple structures at laser-irradiated poly(ethylene terephthalate) surfaces. Poly(ethylene terephthalate) surface was irradiated with linearly polarized light of a pulsed 157 nm laser. In a certain range of irradiation parameters, the irradiation resulted in the formation of coherent ripples patterns. The dimension of the pattern depends on the angle of the laser beam incidence. The surface morphology of the nano-patterned poly(ethylene terephthalate) was analyzed by atomic force microscopy and focused ion beam-scanning electron microscopy. Oxygen concentration in the modified polymer surface was studied by angular resolved X-ray induced photo-electron spectroscopy. Gold nano-layers were consecutively sputtered onto the laser irradiated poly(ethylene terephthalate) surfaces. The morphology of the sputtered gold nano-layers was investigated with atomic force microscopy too. We found that the morphology of the gold nano-layers changes and depends on the surface pattern of the laser irradiated poly(ethylene terephthalate). Formation of gold “nano-hills” is observed at the ridges of the ripple structures. The amount of oxygen together with the morphology of prepared polymer pattern may be the dominant factors controlling the gold layer growth. The present results are compared with those obtained earlier on PET irradiated with krypton fluoride laser.     

On the aging characterization of poly(ethylene terephthalate) by positron spectroscopy

Positron spectroscopy was used to study the free volume properties of glassy poly(ethylene terephthalate) as a function of temperature and aging time. The experimental results indicate that the glass transition temperature increases with increasing aging time. This is confirmed by differential scanning calorimetry measurements. From the aging time dependence of the intensity of the ortho-positronium (o-Ps) component I₃ and the fractional free volume, we observe that the concentration of free volume holes and the fractional free volume show a continuous decrease at a fixed aging temperature, which suggests that structural relaxation and segmental rearrangement occur during physical aging.     

Ensembles of aluminum islands on the surface of strained poly(ethylene terephthalate) films

This paper reports on a study of the size distribution of aluminum islands forming an aluminum-coated poly(ethylene terephthalate) film subjected to tension. The islands are shown to form four statistical ensembles, with the distribution in each of them being thermodynamically optimized and coinciding with the canonic distribution of thermodynamic probability.     

Influence of laser irradiation on the optical and structural properties of poly(ethylene terephthalate) fibres

Laser irradiation has been previously investigated for achieving uniform heating of polyethylene terephthalate (PET) fibres in the hot-drawing stage of the production process, so as to obtain better fibre mechanical properties. The optical properties and dye uptake of PET fibres also depend on the polymer chain orientation and crystallinity within the fibre structure. This paper reports an investigation of a concept whereby laser irradiation and interferometry could be used to modify and trace a small change in the optical properties of a PET monofilament fibre, but the corresponding change in the dye uptake would not be detected visually. A copper vapour laser (550-580 nm wavelengths) was used to expose consecutive 4 mm lengths along a running length of monofilament to 39.8 W cm⁻², at a pulse rate of 9.89 kHz in order to modify, in a controlled way, the polymer crystallinity and orientation. A 3D finite element simulation, based on uncoupled heat-transfer analysis, indicated that rapid heating and cooling could be obtained with the laser to give the small changes required. Irradiated and untreated samples were analysed by interferometry and a 0.16% change was detected in the birefringence profiles, corresponding to a small reduction in the degree of orientation and crystallinity of the irradiated samples. Density measurements and wide-angle X-ray scattering (WAXS) analysis confirmed the change in crystallinity. Tests conducted for dye adsorption and tensile strength showed a small increase in the former and only a very small decrease in the latter. It was concluded that these changes in property provide the opportunity for a laser-irradiated PET monofilament fibre to be used as a subtle tracer element in brand labels for textile garments as an anti-counterfeit measure.     

Dispersion of Nano TiO2 in Ethylene Glycol and Poly(ethylene terephthalate)

Nano TiO₂ was dispersed in ethylene glycol (EG) by the replacement of dispersion medium from water sol. EG/TiO₂ suspension was well stabilized by the electrostatic repulsive force when pH value of suspension was less than 4.3. In situ polymerization starting from bis(2-hydroxyethyl) terephthalate (BHET) and EG/TiO₂ suspension was carried out to prepare a series of poly(ethylene terephthalate) (PET)/TiO₂ nanocomposites. Under highly acidic conditions, 97% particles dispersed in PET matrix had the size less than 100 nm. With the increase of pH value, aggregation occurred and larger size particles appeared. A tensile test showed that Young's modulus of PET was increased by the addition of nano TiO₂     

Exclusive attributes of undoped poly (ethylene terephthalate) for alpha particle detection

Poly (ethylene terephthalate) (PET) is available worldwide and has a broad range of applications. However, its basic properties as a scintillation material that is undoped with fluorescent guest molecules are not completely known. Here, we optically characterise undoped PET for use in radiation detection. Light absorption is primarily below 350 nm, with an emission maximum at 385 nm. An effective refractive index, determined from the emission spectrum and the wavelength dependence of the refractive index, is 1.62, which is greater than that for the sodium D line (N_D = 1.57). The density of PET is 1.33 g/cm³, and its stopping power for 1-MeV electrons is 1.72 MeV cm²/g. Distinct peaks generated by alpha particles from ²¹⁰Pb and ²⁴¹Am radioactive sources appear in PET light-yield distributions. The PET response to 5-6-MeV alpha particles is approximately one-eighth that for electrons. These results demonstrate that undoped PET has special attributes for alpha particle detection. This knowledge will enable better performance of radiation equipment based on PET and its blends with other aromatic ring polymers.     

Grafting of copolymer styrene maleic anhydride on poly(ethylene terephthalate) film by chemical reaction and by plasma method: Optimization of the grafting reaction using experimental design

This work deals with the chemical grafting of a styrene maleic anhydride copolymer on the surface of a previously hydrolyzed polyethylene terephthalate (PET) film 12 μm thick via covalent bond. Two different ways are studied. The first one involves an activation of the hydrolyzed PET by the triethylamine before the grafting step. In the second one, the copolymer reacts with the 4-dimethylaminopyridine in order to form maleinyl pyridinium salt which reacts with alcohol function of the hydrolyzed PET. Characterization and quantification of the grafting are performed by Fourier transform infrared spectroscopy. Factorial experiment designs are used to optimize the process and to estimate experimental parameters effects. The opportunity to associate the chemical process to a cold remote nitrogen plasma one is also examined.