Uncoated Polyethylene Terephthalate Research Articles

Permeation of water vapour, nitrogen, oxygen and carbon dioxide through whey protein isolate based films and coatings—Permselectivity and activation energy

The aim of this study was to evaluate the influence of relative humidity (RH) on the oxygen permeability and water vapour transmission rate (WVTR) of whey protein coated Polyethylene terephthalate (PET) or whey protein monolayer films. Furthermore, the activation energies for the permeability of oxygen, carbon dioxide and nitrogen as well as the permselectivities under different set of temperatures were measured. The results showed that the permeability values through the whey protein coating and whey protein film increased with increasing RH. The water vapour permeability measured at 50% RH of (9.3 ± 0.6)−10 cm3 (STP) cm cm−2 s−1 Pa−1 increased to (16.2 ± 0.9)−10 cm3 (STP) cm cm−2 s−1 Pa−1 at 85% RH. An increase in temperature showed an expected increase of the permeability in both uncoated PET and the whey protein monolayer. The permselectivity of whey protein film was determined and the calculated ratios of the permselectivity (P(N2)/P(O2)/P(CO2):1/(4–6/(34–35)) differed from the simplified ratios given in the literature (P(N2)/P(O2)/P(CO2):1/4/16). Furthermore the calculated activation energy values for whey (51 kJ mol−1) were in agreement with other studies.

Effect of aluminum oxide coating on structural, barrier and electret properties of polyethylene terephthalate films

Polyethylene terephthalate film 12 μm thick with vacuum-deposited AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> coating was studied. Optical and atomic force microscopy was used to investigate surface topology. Film haze, optical density, surface tension, oxygen and vapor transmission rates were measured to estimate barrier performances of the film. To study effect of the coating on electret properties of the film surface potential, electric field strength and efficient surface charge density and thermally stimulated surface potential relaxation were measured. Optimal charging conditions for coated and uncoated polyethylene terephthalate films were found. Interaction of the film with different model mediums simulating foodstuff was studied. Coated electret film can be used as active packaging material with high barrier properties.

Hydrogen gas barrier property of polyelectrolyte/GO layer‐by‐layer films

ABSTRACTDifferent types of ultrathin multilayer composite membranes adsorbed on polyethylene terephthalate (PET) substrates are fabricated by the layer‐by‐layer (LBL) self‐assembly technique. The hydrogen gas barrier performances of these membranes are measured using a pressure permeation instrument. Polyethylenimines/graphene oxide (PEI/GO) are chosen as the optimal system; the multilayer film reduces the hydrogen transmission rate of the uncoated PET film from 1357 to 24 cm3/(m2 24 h 0.1 MPa). The membrane assembly process for the PEI/GO system is analyzed with UV–Visible spectroscopy, and the flat morphology of the ultrathin film is observed by scanning electron and atomic force microscopies. Moreover, in order to fully characterize the PEI/GO multilayer film system, we investigate the effects of multiple variables on the hydrogen resistance performance. These include the molecular weight of PEI, concentrations of PEI and GO, number of bilayers, soaking time, and drying methods. The film thickness is found to increase linearly during the LBL assembly process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41973.

Imaging visceral adhesion to polymeric mesh using pneumoperitoneal-MRI in an experimental rat model.

Intraperitoneal mesh implantation is often associated with formation of adhesion to the mesh. This experimental study examines the potential of minimally invasive pneumoperitoneal-MRI to assess these adhesions in a preclinical context. Uncoated polyethylene terephthalate meshes were placed intraperitoneally in rats, in regard to the caecum previously scraped to promote petechial bleeding and subsequent adhesions. Examinations were performed 2-weeks post mesh implantation using a rodent dedicated high field MRI. Respiratory-triggered T2-weighted images were acquired prior to and after intraperitoneal injection of ~8-10 mL gas to induce a mechanical stress on the abdominal wall. Adhesions are occasionally seen in sham-operated rats as opposed to rats receiving polyethylene terephthalate meshes. On high-resolution images, meshes can be detected due to their characteristic net shape. However, evidence of adherence is only found if intraperitoneal gas injection is performed, when a ~1-cm elevation of the abdominal wall is observed. When adherence occurs between the mesh and the caecum, the latter remains in contact with the wall. Looser adherences between visceral tissue and meshes are also observed. T2-weighted pneumoperitoneal-MRI is a powerful tool for assessing adherence after intraperitoneal mesh implantation. According to the mini-invasive procedure adopted here, this approach may allow a temporal follow-up of adherence fate.

Investigation of gas permeation through Al-metallized film for vacuum insulation panels

Recently, vacuum insulation panels (VIPs) become a key issue to save the building energy. VIPs must have a good insulation performance and a long service life. Al-metallized film can meet these requirements by suppressing both of thermal bridging and gas permeation. In this work, gas permeabilities through an Al-metallized film for various gases are measured using a newly-developed experimental apparatus based on a pressure difference method. Its reliability is validated by measuring a few well-known gas permeabilities through uncoated 12μm polyethylene terephthalate (PET) film. Then, a 12μm PET film coated with a 33nm aluminum layer is chosen as the sample metallized film. It is confirmed by residual gas analyzer (RGA) that nitrogen, oxygen, carbon dioxide and water vapor are the major gases permeating through the Al-metallized film, which are then taken as the test gases. Permeabilities of these gases through the Al-metallized film are measured to be only about 4.1% of those through uncoated PET film. Nevertheless, it is still higher than those of metal sheets because of the abundant pin-holes. Pin-holes are investigated for the distribution and the diameter by an optical microscope. An effective gas permeability including the pin-hole effect is calculated to be 3.6–4.0% of uncoated PET film permeability, agreeing well with the experimental results. Multiple Al-metallized layers must be thus employed to be effective gas barriers. A correlation for the permeation through a layer of Al-metallized film is also derived. These research results and methods can be usefully applied to actual VIP envelope materials with multiple Al-layers.

Synthesis of hydrogenated amorphous carbon films with a line type atmospheric-pressure plasma CVD apparatus

In this study, hydrogenated amorphous carbon (a-C:H) films were synthesized on polyethylene terephthalate (PET) substrates with a line type atmospheric-pressure plasma chemical vapor deposition (CVD) apparatus. Acetylene and nitrogen mixture gas was used for process gas and a-C:H films having two different thickness were synthesized with varying the C2H2 mixing rates. We investigated the effect of chemical bonding structure on the ultraviolet ray shielding property of the films. The deposition rate increased as a function of the C2H2 mixing rates. Increasing the C2H2 mixing rate from 2.5 to 10% caused an increase in the deposition rates from 13 to 22nm/s. The deposition rate under atmospheric pressure was faster than that of low-pressure plasma CVD (~5–16nm/s). Ultraviolet transmittance of 2μm thick a-C:H film synthesized at the C2H2 mixing rate of 10% on 100μm thick PET substrates ranged from 0 to 3% as the UV wavelength ranged from 310 to 400nm, while that of uncoated PET substrates ranged from 0 to 80%. From the result of X-ray photoelectron spectroscopy (XPS) analysis, the component of sp2-hybridized C, such as CC and CO bonds increased as the C2H2 mixing rate and thickness of a-C:H films increased. A decrease of sp3-hybridized C, such as CC and CO bonds and an increase of sp2-hybridized C bonds lead to an improvement of ultraviolet ray shielding property.

Electrically conductive and optically transparent polyethylene terephthalate films coated with gold and silver by thermionic vacuum arc

This study shows the morphology, physical, mechanical, and optical properties of conductive and transparent Ag and Au coated on polyethylene terephthalate (PET) by thermionic vacuum arc (TVA). Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) were used for the morphology investigation. To determine the mechanical and physical properties, hardness, scratch resistance, adhesion tests, and friction coefficient were measured. Friction coefficients were determined to be 0.141, 0.233, and 0.245 for uncoated PET, Gold (Au)-coated PET and Silver (Ag)-coated PET, respectively. Electrical resistivity measurements were performed using the two-probe technique. Au was 40 Ω and Ag 7 Ω versus uncoated PET, which is nonconductive with electrical surface resistance value in the order of 1014—1018Ω. The Au- and Ag-coated PETs reflectance was approximately 50% at 550 nm. Transmittance values of the Au- and Ag-coated PET films were approximately 70% and 20% at 550 nm.

Investigations of plasma polymerized SiOx barrier films for polymer food packaging

Nano-scale SiOx layers were deposited on polyethylene terephthalate (PET) foils by plasma enhanced chemical vapor deposition (PECVD) in an electron cyclotron resonance (ECR) plasma process in order to enhance their barrier properties towards water vapor. Oxygen (O2) and hexamethyldisilazane (HMDSN) served as reactive gas and precursor, respectively. The effect of layer thickness and O2:HMDSN (x:1) gas mixture ratio on the water vapor transmission rate was systematically investigated. Measurements by infrared spectroscopy and scanning electron microscopy for the characterization of the chemical composition and of the surface structure of the SiOx layers, respectively, showed that both chemical composition and surface structure of the layers have a noticeable effect on their barrier properties. For low O2 content in the O2:HMDSN gas mixture ratio, organic layers were deposited. When increasing the O2 content, the growing number of inorganic compounds in the SiOx layers found by the infrared spectroscopy gave rise to a decrease in the water vapor transmission rate. A reduction of the water vapor permeation by more than a factor of 2 in comparison with the uncoated PET foil was achieved by the best performing SiOx layer. Further increase of the O2 content led to the onset of a columnar-like layer growth which showed to be causative for the water vapor permeation rising again.Finally, the barrier properties towards water vapor of 100nm thick SiOx films deposited from different O2:HMDSN gas mixtures were contrasted with their corresponding barrier properties towards O2. The minimum water vapor and O2 permeation results were found for the SiOx films plasma deposited from almost identical O2:HMDSN gas mixture ratios in the range of 25≤x≤30.

A probabilistic model for the permeation of gases through microporous membranes

A probabilistic model for the motion of gas molecules through pores of microporous membranes is proposed. The interaction energy between the gas molecules and the surface of membrane pores is investigated using molecular modeling and results are used as input to the probabilistic model. The proposed model was used to evaluate the effect of surface coating on gas permeation of air and ammonia through single- and double-layer microporous membranes. Gas transmission experiments were conducted on uncoated polyethylene terephthalate (PET), nylon and PP/PE, coated PET, and double-layer PET microporous membranes at different pressure levels. Model results were compared with experimental data and a reasonable conclusion was drawn.

Contributions of surface topography and cytotoxicity to the macrophage response to zinc oxide nanorods

Macrophages associated with implanted biomaterials are primary mediators of chronic inflammation and foreign body reaction to the implant. Hence, various approaches have been investigated to modulate macrophage interactions with biomaterial surfaces to mitigate inflammatory responses. Nanostructured materials possess unique surface properties, and nanotopography has been reported to modulate cell adhesion and viability in a cell type-dependent manner. Zinc oxide (ZnO) has been investigated in a number of biomedical applications and surfaces presenting well-controlled nanorod structures of ZnO have recently been developed. In order to investigate the influence of nanotopography on macrophage adhesive response, we evaluated macrophage adhesion and viability on ZnO nanorods, compared to a relatively flat sputtered ZnO controls and using glass substrates for reference. We found that although macrophages are capable of initially adhering to and spreading on ZnO nanorod substrates, the number of adherent macrophages on ZnO nanorods was reduced compared to ZnO flat substrate and glass. Additionally adherent macrophage number on ZnO flat substrate was reduced as compared to glass. While these data suggest nanotopography may modulate macrophage adhesion, reduced cell viability on both sputtered and nanorod ZnO substrate indicates appreciable toxicity associated with ZnO. Cell death was apparently not apoptotic, given the lack of activated caspase-3 immunostaining. A decrease in viable macrophage numbers when ZnO substrates were present in the same media verified the role of ZnO substrate dissolution, and dissolved levels of Zn in culture media were quantified. In order to determine long-term physiological responses, ZnO nanorod-coated and sputtered ZnO-coated polyethylene terephthalate (PET) discs were implanted subcutaneously in mice for 14 d. Upon implantation, both ZnO-coated discs resulted in a discontinuous cellular fibrous capsule indicative of unresolved inflammation, in contrast to uncoated PET discs, which resulted in typical foreign body capsule formation. In conclusion, although ZnO substrates presenting nanorod topography have previously been shown to modulate cellular adhesion in a topography-dependent fashion for specific cell types, this work demonstrates that for primary murine macrophages, cell adhesion and viability correlate to both nanotopography and toxicity of dissolved Zn, parameters which are likely interdependent.

Effects of nitrogen partial pressure on titanium oxynitride films deposited by reactive RF magnetron sputtering onto PET substrates

Titanium oxynitride (TiNxOy) films have been deposited onto polyethylene terephthalate (PET) substrates by reactive radio frequency (RF) magnetron sputtering. The influence of the nitrogen (N2) partial pressure in the discharge atmosphere, with a set pressure of 0.133 Pa, was examined. Other deposition conditions were held constant. The deposition rate of the films, which exhibit an island-type morphology, was found to decrease with increasing N2 partial pressure. This concurred with an increase in the surface roughness at higher N2 partial pressure. The TiNxOy films deposited at N2 partial pressures from 0.26×10−1 Pa to 0.8×10−1 Pa possess Ti:N:O ratio of about 1:0.9:0.8 to 1:1.2:0.7. At the lowest N2 partial pressure of 0.26×10−1 Pa, the water vapor (WV) and oxygen transmission rates (OTR) of the TiNxOy films reached values as low as 0.31 g/m2-day-atm and 0.62 cc/m2-day-atm, respectively; these values are about 16 and 50 times lower than those of the uncoated PET substrate.

Gas barrier properties of titanium oxynitride films deposited on polyethylene terephthalate substrates by reactive magnetron sputtering

Titanium oxynitride (TiN x O y ) films were deposited on polyethylene terephthalate (PET) substrates by means of a reactive radio frequency (RF) magnetron sputtering system in which the power density and substrate bias were the varied parameters. Experimental results show that the deposited TiN x O y films exhibited an amorphous or a columnar structure with fine crystalline dependent on power density. The deposition rate increases significantly in conjunction as the power density increases from 2 W/cm 2 to 7 W/cm 2. The maximum deposition rate occurs, as the substrate bias is −40 V at a certain power densities chosen in this study. The film's roughness slightly decreases with increasing substrate bias. The TiN x O y films deposited at power densities above 4 W/cm 2 show a steady Ti:N:O ratio of about 1:1:0.8. The water vapor and oxygen transmission rates of the TiN x O y films reach values as low as 0.98 g/m 2-day-atm and 0.60 cm 3/m 2-day-atm which are about 6 and 47 times lower than those of the uncoated PET substrate, respectively. These transmission rates are comparable to those of DLC, carbon-based and Al 2O 3 barrier films. Therefore, TiN x O y films are potential candidates to be used as a gas permeation barrier for PET substrate.

Gas barrier properties of carbon films synthesized by atmospheric pressure glow plasma

High gas barrier carbon films were successfully synthesized on top of polymer substrates using an atmospheric-pressure glow (APG) plasma CVD equipment by reducing the discharge area and by changing the size of the electrodes of the equipment. Homogeneous and highly stable plasma was constantly generated under an atmosphere of acetylene gas (C 2H 2) without using any other dilution gases such as He, Ar and N 2 that are generally used in order to stabilize the plasma. The absence of the dilution gases led to form rigid carbon-to-carbon bonds. The rigid C bonds constructed dense carbon films at the very surface of the coated films with high gas barrier properties. The oxygen transmission rates of the polyethylene terephthalate (PET) film coated with this amorphous carbon (a-C:H) material was therefore dramatically improved (23 times less in transmission rate) compared with that of an uncoated PET film. The microstructures of the films were investigated by Fourier transform infrared spectroscopy (FT-IR) and the surface morphology was observed by a scanning electron microscope (SEM).

The effect of phosphorylcholine-coated materials on the inflammatory response and fibrous capsule formation: in vitro and in vivo observations.

Several experiments were performed to compare the in vitro adhesion of human macrophage and granulocyte inflammatory cells to polyethylene terephthalate substrate and the same coated with a phosphorylcholine (PC)-based polymer. The inclusion of various types of serum at different stages in the assay indicated that protein adsorption and passivation of the surface may be responsible for reducing the number of inflammatory cells adhering to the uncoated polyethylene terephthalate controls. In all of the assays performed there was a statistically significant reduction (p < 0.05; analysis of variance) of the number of inflammatory cells adhering to the PC-coated samples, linked to the ability of these surfaces to resist protein adhesion. Implantations of PC-coated stainless steel and high-density polyethylene USP control samples were made in a rabbit intramuscular model. Histological examination of the number of inflammatory cells present around the implant sites 4 weeks postimplantation showed there were 40% less cells associated with the PC-coated samples compared with control, but this was not statistically significant. Fibrous capsule thickness, however, whereas marginally less at 4 weeks, had almost completely regressed for the PC-coated sample at 13 weeks postimplantation and was statistically thinner (p < 0.01; Mann-Whitney U test) than the high-density polyethylene USP control. These findings support the view that low biointeractions observed for PC-based technology in vitro can result in reduced inflammation and foreign body reaction in vivo.

Expression of adhesion molecules and cytokines in vitro by endothelial cells seeded on various polymer surfaces coated with titaniumcarboxonitride.

Although endothelial cell (EC) seeding improves the patency of vascular prostheses, the detachment of adherent ECs after the restoration of circulation remains one of the major obstacles. Polymer surfaces for endothelialization can be optimized. In this study, polyethylene terephthalate (PET), polypropylene (PP), polytetrafluoroethylene (PTFE), polyurethane (PUR), and silicone were coated with a titaniumcarboxonitride (Ti(C,N,O)) layer by a plasma-assisted chemical vapor deposition process to verify the effect of titanium onto human saphenous vein ECs. Almost confluent EC monolayers were evaluated for 1) proliferation activity and 2) expression of adhesion molecules using cellular enzyme-linked immunosorbent assay and release of cytokines. The results showed that all titanium-coated polymers and uncoated PET have no toxic effect on human saphenous vein ECs excepting uncoated PTFE, PP, and silicone. Moreover, growing ECs showed an insignificant decrease in cytokine production and an unessential change in basal expression of adhesion molecules. Tumor necrosis factor-alpha-induced response depends on polymer surface: for example, intercellular adhesion molecule-1 expression decreased. E-selectin expression was unchanged for culturing ECs on coated PET, PP, and PTFE and reduced for polyurethane and silicone. Vascular cell adhesion molecule-1 expression was unchanged for coated PUR and silicone and reduced for PET, PP, and PTFE. In summary, titanium-coating layers promote adhesion of human ECs on polymer vascular grafts with no proinflammatory reaction of ECs.

Flow-cytometric analysis of leukocyte activation induced by polyethylene-terephthalate with and without pyrolytic carbon coating.

Leukocyte activation is one test for the evaluation of blood-materials interaction. The expression of adhesion molecules analyzed by flow cytometry provides a simple method to evaluate leukocyte activation by biomaterials: any change in these molecules can be predictive of the inflammatory activity of the materials. In this study the contact between leukocytes and uncoated polyethylene terephthalate or pyrolytic carbon-coated polyethylene terephthalate (PET and PET-PC, respectively) was inspected by analyzing whether the expression of some adhesion molecules involved in leukocyte activation, namely LFA-1 (CD11a/ CD18), Mac-1/CR3 (CD11b/CD18), and LECAM-1 (CD62L) can be modified. By flow cytometry expression of the adhesion molecules can be studied separately on lymphocytes and myeloid cells. The materials tested reduced the total numbers of both leukocytes and neutrophils, although not significantly. Neither PET nor PET-PC changed the expression of the adhesion molecules in lymphocytes: this suggests that no specific immune response is stimulated. On the contrary, statistically significant changes were observed for monocytes and granulocytes: the percentage of cells expressing Mac-1 and the density of such antigens on cell membranes increased while the percentage of LECAM-1 positive cells decreased. Similar changes were observed when the cells underwent the inflammatory stimulus provided by an in vitro challenge with bacterial endotoxin. Our results demonstrated that polyethylene terephthalate activates leukocytes by modifying the expression in neutrophils of the molecules involved in the early phase of the inflammatory response. Even after coating PET with pyrolytic carbon, the ability of this material to activate circulating leukocytes was maintained.

In vitro complement activation after contact with pyrolytic carbon-coated and uncoated polyethylene terephthalate.

This study was undertaken to evaluate whether the pyrolytic carbon coating of polyethylene terephthalate induces complement activation. Complement activation induced by pyrolytic carbon-coated polyethylene terephthalate (PET+PC) in comparison with uncoated polyethylene terephthalate (PET) was assessed on whole blood collected with heparin. The activation of the classic pathway was evaluated by C4d fragment enzyme immunoassay. The activation of the alternative pathway was evaluated with Bb fragment enzyme immunoassay. The results show that uncoated PET activates the alternative pathway, but not the classic one. PET+PC does not induce complement activation, not even through the alternative pathway. Pyrolytic carbon coating therefore contributes to improving blood compatibility.