Thin Polyethylene Terephthalate Research Articles

An approach to the usage of polyethylene terephthalate (PET) waste as roadway pavement material

This study investigates an application area for Polyethylene Terephthalate (PET) bottle waste which has become an environmental problem in recent decades as being a considerable part of the total plastic waste bulk. Two novel additive materials, namely Thin Liquid Polyol PET (TLPP) and Viscous Polyol PET (VPP), were chemically derived from waste PET bottles and used to modify the base asphalt separately for this aim. The effects of TLPP and VPP on the asphalt and hot mix asphalt (HMA) mixture properties were detected through conventional tests (Penetration, Softening Point, Ductility, Marshall Stability, Nicholson Stripping) and Superpave methods (Rotational Viscosity, Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR)). Also, chemical structures were described by Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectrometer (EDS) and Fourier Transform Infrared (FTIR) techniques. Since TLPP and VPP were determined to improve the low temperature performance and fatigue resistance of the asphalt as well as the Marshall Stability and stripping resistance of the HMA mixtures based on the results of the applied tests, the usage of PET waste as an asphalt roadway pavement material offers an alternative and a beneficial way of disposal of this ecologically hazardous material.

Fabrication of a seamless roller mold with wavy microstructures using mask-less curved surface beam pen lithography

Roller imprinting is one of the most commonly used methods for the fabrication of continuous functional structures over large areas. However, the fabrication of roller molds with seamless and complex patterns poses a significant challenge. This paper presents an innovative technique for fabricating a seamless roller mold with wavy microstructures using a novel mask-less curved surface beam pen lithography technique. The major steps in the proposed technique include spray coating a thin photo-resist (PR) layer on the roller, exposing the PR layer though a translating micro-lens array (MLA), etching the patterned PR layer, and electro-polishing the etched microstructures. The proposed method is used to pattern roller molds with different wavy microstructures by varying the rotation speed of the roller, the translation speed of the MLA holder, and the translation distance of the MLA holder. The patterned metal roller molds are then used to replicate wavy microstructures on a thin polyethylene terephthalate substrate by means of continuous UV-type roller imprinting methods. The line-width and height of the wavy microstructure are 84.5 µm and 25.5 µm, respectively.

Evaluation Method for Stretch Blow Moulding Simulations with Process-Oriented Experiments

In the Stretch blow moulding (SBM) process, polyethylene terephthalate (PET)-preforms are biaxially deformed to produce thin walled bottles. Finite-Element (FE)-Simulations are an important tool to optimise this process in terms of material usage and product performance. Thereby, the implementation of the thermo-mechanical material behaviour of PET plays an important role to achieve realistic simulation results. A common approach for this purpose is to calibrate a material model with stress-strain curves from biaxial stretching experiments. Thin PET-sheets are stretched under defined temperatures and strain rates. However, these experiments include process simplifications concerning geometry, heating and deformation parameters. This paper presents a method for extracting temperature dependent stress-strain-curves from experiments close to the production process. PET-Preforms receive thermal treatment with Infrared (IR)-heaters from an SBM-machine and are subsequently inflated in free air (free blow trial). A high-speed-IR-camera is used to image the axial and radial temperature distribution on the preform immediately before blowing. The deformation process is recorded via 3d-high-speed-cameras with a frame rate of 2000/s. The cameras are synchronised with a pressure sensor to consequently calculate reliable stress-strain curves at any point on the preform. In addition FE-simulations of the free blow trials are conducted using a material model calibrated with the simplified stretching experiments of thin PET sheets. Resulting stress-strain-curves from simulations and free-blow-trials are finally compared to evaluate the quality of the material model as well as the underlying testing procedure.

Fabrication of Seamless Roller Mold for Continuous Roller Imprinting of Microlens Array Films

This paper describes an innovative approach for fabricating a seamless roller mold based on cylindrical photolithography, isotropic chemical etching, and electropolishing. Hexagonally arrayed concave microstructures with a near-semispherical profile are directly and seamlessly fabricated on a metal roller. The fabricated roller mold is then used for continuous roller imprinting of microlens array (MLA) on a thin polyethylene terephthalate (PET) substrate. The fabricated ball-shape microlenses have a footprint diameter of 54 and a sag height of 20.5 and are hexagonally close packed with a filling ratio larger than 91%. This MLA/PET optical film can serve as a brightness enhancement film in flat panel backlighting, and its optical performance is experimentally verified. A 30% increase in the forward on-axis luminance is observed.

Precision patterning of conductive polymer nanocomposite using a laser-ablated thin film

We introduce a simple, reliable and low-cost microfabrication technique utilizing laser ablation of a thin polymer film to pattern polymer nanocomposite at a high resolution. A conductive composite of poly(dimethylsiloxane) (PDMS) and carbon nanotubes (CNTs) was selected due to their wide use in microelectromechanical systems (MEMS) and unique properties including flexibility and piezoresistivity. To pattern nanocomposite, an excimer laser ablated through a thin polyethylene terephthalate film creating mold patterns. PDMS-CNTs nanocomposite was then filled into the mold with excessive amount removed by a smooth-edged tool. Bulk PDMS was poured atop and cured. After debonding devices with relief patterns of polymer nanocomposite could be readily realized. Fabrication conditions were optimized which led to reliable patterning of various microstructures. Detailed surface profiling revealed excellent pattern authenticity and uniformity. Minimal feature size of patterns reached below 20 µm which indicated a significant improvement from prior reports. Moreover, the presented technique required only a software design to rapidly generate new patterns, thereby eliminating costly hardware such as lithography mask, stamp and clean room. Fabrication time and cost could be consequently reduced—ideal for lab prototyping purposes. Sensor examples are discussed to demonstrate versatile applications of polymer nanocomposite in MEMS.

Reflectarray design using printed electronics technology

A Ka-band reflectarray antenna with single sub-wavelength loop elements has been designed and fabricated using printed electronic technology. The reflectarray pattern is printed on a thin polyethylene terephthalate substrate using an inkjet printer with silver metal ink. The fabrication process and measurement results are reported.

Carbon‐Nanotube‐Film Microheater on a Polyethylene Terephthalate Substrate and Its Application in Thermochromic Displays

Polyethylene terephthalate (PET) is used as the substrate of a carbon nanotube (CNT)-film heater to improve its mechanical robustness. The thermal response is improved by using thin PET and downsizing the CNT-film area. Thermal response times from room temperature to 100 °C of 2 and 5 s are achieved. An addressable microheater array is fabricated and used in thermochromic displays. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Flexible inverted polymer solar cells containing an amorphous titanium oxide electron collection electrode

An inverted polymer solar cell was fabricated on a polyethylene terephthalate (PET) substrate. The cell structure was ITO/amorphous titanium oxide (TiO x )/[6,6]-phenyl C 61 butyric acid methyl ester (PCBM): regioregular poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid) (PEDOT:PSS)/Au (TiO x cell). It was achieved using low boiling point diethyl amine (DEA) as a Ti 4+ complexing agent, and high boiling point 1,2,3,4-tetrahydronaphthalene (Tetralin) containing 2 vol.% 1,8-octanedithiol (ODT) as the solvent for PCBM:P3HT film preparation. With heat treatment at 100 °C, the use of DEA and Tetralin:ODT made it possible to prepare a TiO x electron collection layer and PCBM:P3HT photoactive layer, respectively. Fabricating the TiO x cell on the thin PET film was possible, as PET did not warp at 100 °C. The power conversion efficiency (PCE) of the TiO x cell fabricated on PET was 2.43%, under AM1.5G conditions. When fabricated on glass, the PCE was 2.76%. When [6,6] diphenyl C 62 bis(butyric acid methyl ester) (bis-PCBM) was instead used as the electron acceptor in the photoactive blend layer, the flexible air-stable cell provided a PCE of 2.81%.

Modeling Tissue Growth Within Nonwoven Scaffolds Pores

In this study we present a novel approach for predicting tissue growth within the pores of fibrous tissue engineering scaffolds. Thin nonwoven polyethylene terephthalate scaffolds were prepared to characterize tissue growth within scaffold pores, by mouse NR6 fibroblast cells. On the basis of measurements of tissue lengths at fiber crossovers and along fiber segments, mathematical models were determined during the proliferative phase of cell growth. Tissue growth at fiber crossovers decreased with increasing interfiber angle, with exponential relationships determined on day 6 and 10 of culture. Analysis of tissue growth along fiber segments determined two growth profiles, one with enhanced growth as a result of increased tissue lengths near the fiber crossover, achieved in the latter stage of culture. Derived mathematical models were used in the development of a software program to visualize predicted tissue growth within a pore. This study identifies key pore parameters that contribute toward tissue growth, and suggests models for predicting this growth, based on fibroblast cells. Such models may be used in aiding scaffold design, for optimum pore infiltration during the tissue engineering process.

Three-dimensional bulk metamaterials operating in the terahertz range

Three-dimensional bulk metamaterials that operate in the terahertz (THz) frequency range were fabricated by stacking 100 two-dimensional sheets containing metallic split-ring resonators (SRR) on thin polyethylene terephthalate film substrates. The THz magnetic resonance for the incident magnetic field perpendicular to the plane of the SRR structure was measured. We also investigated the dependence of the magnetic resonant strength on the metal thickness.

Magnetoresistive Effect in PET Films with Iron Nanoparticles Synthesized by Ion Implantation

Thin polyethyleneterephthalate (PET) layers with Fe nanoparticles (NPs) were synthesized by high-fluence ion implantation. Temperature dependence of conductance and magnetoresistance, were studied as a function of ion fluence. It is found that the implantation with fluences of about 1.0×10 17 cm -2 causes high enough concentration of metal inclu- sions to provide conditions for electrical percolation that leads to an insulator-to-metal transition (IMT) in charge carrier transport mechanisms. The magnetoresistance measurements indicate that the magnetic percolation takes place at metal concentrations (fluences) lower than those needed for the electrical percolation. For the samples on insulating side of the IMT, a non-monotonous dependence of resistance in an increasing external magnetic field is observed due to anisotropic magnetoresistive effect and charge carrier scattering on magnetic inclusions. For the samples implanted with fluences ≥ 1.0×10 17 cm -2 , the magnetoresistance becomes a monotonous decreasing function of the external magnetic field which is typical for ferromagnetic metals that indicates effective magnetic coupling of the iron inclusions.

Distance distribution of bystander effects in alpha-particle irradiated cell populations using a CR-39-based culture dish

Propagation of induced biological effects from irradiated to non-irradiated cells is known to occur in cell cultures exposed to low fluences of charged particles. These bystander effects are currently investigated using microbeam or non-microbeam (broad beams) irradiation techniques. Identification of the targeted and non-targeted bystander cells is critical to our understanding of mechanisms underlying such effects. We developed a novel cell culture dish where the base consists of a thin CR-39 sheet grafted on a thin polyethylene terephthalate (PET) foil. The validity of this device in identifying not only irradiated cells, but also the cellular compartment traversed by the particle track is described. We have optimized track etch parameters that do not interfere with measurement of induced biological endpoints under normal incident irradiation. Thus the culture dishes can be used to determine distance distributions for the propagation of induced biological effects from a hit cell to bystander cells. We describe the computer code developed to determine the distance distributions of propagated biological stress responses in normal human fibroblast cells exposed to very low fluences of alpha particles.

Modeling of discrete currents of single ion channels of cell membranes using synthetic nanometer pores in polyethylene terephthalate films

In studying of conductivity of single supernarrow pores (varying 1 to 15 nm in diameter), formed in thin membranes (10-12 microm in the thickness) from polyethylene terephthalate (PETP), there were revealed discrete changes of currents passing through such pores when applied from external source of potential difference from 200 to 1000 mV. By several characteristics, such discrete currents (discrete conductivity changes) appeared to be identical the so-cold current of single ionic channels in the cell membranes. Supernarrow pores which properties are describes in the present work were obtained as a result of alkaline etching of tracks in thin PETP membranes (a variant of the so-called nuclear filters). Alkaline etching leads to formation of negative fixed charges on the walls of the pores compensated by positive counterions. When setting potential difference onto the PETP membrane, the latter cation layer is able to transfer the current and this transfer was called the surface conductance. In the case of nanometer pores, such surface conductance may be dominating. We have shown that these discrete changes of currents passing through nanometer pores are associated with metastability of the surface conductance. In the case of highly cation-selective channels in the cell membranes it is inevitable, that at least a part of these channels should have dominating cation surface conductance and mentioned above conductance metastability as well. Our findings allow us to propose a new explanation of the origin of the characteristic discreteness of the currents of cation-selective ionic channels in the cell membranes.

Electroacoustic miniaturized DNA-biosensor

A micrometer-sized electroacoustic DNA-biosensor was developed. The device included a thin semi-crystalline polyethylene terephthalate (PET) dielectric layer with two Ag microband electrodes on one side and a DNA thiol-labeled monolayer adsorbed on a gold surface on the other. A resonance wave was observed at 29 MHz with a network analyzer, upon AC voltage application between the two Ag electrodes, corresponding to electromechanical coupling induced by molecular dipoles of the PET polymer chain in the dielectric layer. It was found that the device size and geometry were well adapted to detect DNA hybridization, by measuring the capacity of the resonance response evolution: hybridization induced polarization of the dielectric material that affected the electromechanical coupling established in the dielectric layer. The 0.2 mm(2) sensor sensitive area allows detection in small volumes and still has higher detection levels for bioanalytical applications, the non-contact configuration adopted avoids electric faradic reactions that may damage biosensor sensitive layers, and finally, PET is a costless raw material, easy to process and well adapted for large scale production. The well-balanced technological and economic advantages of this kind of device make it a good candidate for biochip integration.

Optical characteristics of uniaxial polyester films with the optical axis perpendicular to the surface

The functions of the main indices of refraction n(ν) and absorption κ(ν) of uniaxial thin polyethylene terephthalate films have been calculated by the experimental spectra of frustrated total reflection of s-and p-polarized radiation in the 700–760-cm−1 range. The κo(ν) maximum falls at the the 727-cm−1 frequency and the maximum of κe(ν) falls at the the 724-and 732-cm− 1 frequencies.

Fabrication of a synthetic nanopore ion pump.

We present a synthetic nanodevice, which transports potassium ions against their concentration gradient if stimulated with external field fluctuations. It consists of a single, conical pore, created in a thin polyethylene terephthalate film. The pumping mechanism is similar to one of longitudinally oscillating deterministic ratchets.

The role of polarization in the breakdownof an air gap with barrier

It is shown that the inhomogeneous polarization of an insulation gapwith barrier in an electrical field due to a sharp change in the permittivityand/or conductivity at the interface of `basic dielectric-barrier' is one ofpossible reasons of the so-called barrier effect in dielectrics. The influenceof the preliminary polarization of thin polyethylene terephthalate barriers onthe breakdown voltage of an air gap with a needle-plane configuration underac and dc voltage is determined.

Determination of the orthotropic elastic constants of thin PET film by an ultrasonic micro-spectrometer

The elastic constants of a thin polyethylene terephthalate (PET) film, whose thickness was 12 mum, were determined from the acoustic reflection coefficients. The reflection coefficients were measured by an ultrasonic micro-spectrometer (UMSM), and all of the elastic constants were obtained through the fitting of a theory to the dip points of the magnitude of the reflection constants where leaky Lamb waves were excited. As a result, the film was found to be an orthotropic material, and the observed elastic constants were consistent with those measured by tensile tests. Besides, the in-plane shear modulus was found to be much larger than the out-of-plane shear moduli. Then, the reflection coefficients were calculated using the obtained stiffness matrix. The calculated values reproduced not only the dip points but also the change in magnitude of measured reflection coefficients depending on the frequency and the incident angle. These agreements suggest that the stiffness matrix components were determined accurately.

Thermally stimulated current study of space-charge formation and contact effects in metal-polyethylene terephthalate films-metal systems. III. Influence of heat treatments

The influence exercised by heat treatments on the charge exchange properties of the interfacial barriers existing in metal-insulator-metal (MIM) systems obtained by vacuum deposition of aluminum electrodes on both faces of thin polyethylene terephthalate (PET) films has been investigated by using the thermally stimulated depolarization current (TSDC) method. A number of parameters have been systematically varied, including annealing atmospheres (helium, helium + oxygen, helium + nitrogen, vacuum, or air), annealing temperature, annealing time, sample fixing mode (free or taut annealing) and order adopted for applying the two procedures of annealing and metallization. The variations observed have been interpreted in terms of the electronic band model developed in the first paper of this series. X-ray photoelectron spectroscopy, thermomechanical analysis, density, aluminum adhesion and oxygen permeation measurements, were used to specify both volume and interfacial modifications undergone by the MIM structures and to support the TSDC data.

Thermally stimulated current study of space charge formation and contact effects in metal-Polyethylene Terephthalate film-metal systems. II. Influence of polarization conditions

The influence of the polarization conditions on the space charge formation in Metal-Insulator-Metal systems obtained by vacuum deposition of aluminum electrodes on both faces of thin Polyethylene Terephthalate (PET) films has been investigated by using the Thermally Stimulated Depolarization Current (TSDC) method in a wide range of poling temperatures, poling times and applied field strengths, emphasizing the effects of the presence of Schottky barriers at the Al-PET interfaces after heat treatment under helium. TSDC spectra of PET films ranging in thickness from 1.5 to 12 μm have been interpreted on the basis of the extended electronic band model described in a previous paper. Different values of activation energies, corresponding to distinct processes occurring during the space charge relaxation, have been determined, allowing a clear relationship between dipolar orientation and electronic detrapping to be evidenced. The height of the interfacial potential barriers between aluminum and PET has also been estimated.