Deformation capacity of RC piers wrapped by new fiber-reinforced polymer with large fracture strain

One of the major drawbacks of structure strengthening by fiber reinforced polymer wrapping using materials such as CFRP and AFRP, whose strength and stiffness are high, is the brittle nature of failure mode, which is caused by fracture of the fiber due to low fracturing strain. A series of experiments were conducted to investigate the efficiency of using two new types of fibers, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) fiber, for seismic strengthening of RC piers. These fibers have the properties of low stiffness and high fracturing strain. Specimens strengthened by PET and PEN fiber sheets wrapping showed considerable improvement in shear capacity and ductility compared to the control specimen. Both PET and PEN showed no tendency to fiber breakage before the pre-defined ultimate deformation. Pier behaviors such as shear deformation and strain development in both fiber and steel shear reinforcement, and the piers, ultimate failure modes, were carefully examined. Shear deformation increases rather rapidly after peak load and concrete shear capacity decreases with the increase in shear deformation. Stiffness of fiber affects the development of shear deformation and the descending branch of the load–deformation curve after the peak load. A simple model to predict the piers deformation capacity, based on the experimental results, was proposed.     

Mechanical properties of ZnO thin films deposited on polyester substrates used in flexible device applications

ZnO is growing in importance as a functional film in flexible devices because of the wide range of electrical properties that can be achieved through appropriate doping and the relative abundance of Zn. We have deposited ZnO films with various thicknesses by sputtering on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) flexible substrates and measured their mechanical properties using compression and scratch tests coupled with in-situ optical microscopy. The cracking of ZnO, during compression, is thickness dependent and at lower thicknesses the films sputtered on PEN exhibit the highest crack onset strains, around 2%. During scratch testing, two major scratch failure mechanisms are observed, analyzed and discussed. It is also found that scratch resistance of ZnO is thickness dependent for both PET and PEN. At high scratch loads a secondary failure mechanism due to impregnation of film debris into the polymer substrates is observed.     

Nanoscale deformation measurement of microscale interconnection assemblies by a digital image correlation technique

The continuous miniaturization of microelectronic devices and interconnections demand more and more experimental strain/stress analysis of micro-?and nanoscale components for material characterization and structure reliability analysis. The digital image correlation (DIC) technique, with the aid of scanning probe microscopes, has become a very promising tool to meet this demand. In this study, an atomic force microscope (AFM) was used to scan and digitally image micro-interconnection assemblies in a micro-thermoelectric cooler. AFM images of the scan region of interest were obtained separately when the microelectronic device was operated before and after the cooling and heating stages. The AFM images were then used to obtain the in-plane deformation fields in the observed region of the micro-assembly. AFM image correlation is performed for nanoscale deformation analysis using the authors' AFM-DIC program. The results show that the observed region was subjected to cyclic strains when the device worked between its cooling and heating stages, and cyclic strain in the vertical direction was found to be a significant deformation mode. The thermally induced deformation behavior of the micro-assembly device was modeled by finite element analysis (FEA). Both thermal-electric analysis and thermal stress analysis were conducted on a 3D finite element model of the device. It is shown that the experimental results were able to validate the finite element analysis results.     

预测相融共混膜氧气透过率的分形渝渗模型

目的 预测相融体系共混膜氧气透过率,为高阻氧共混膜的生产和设计提供理论依据.方法 应用分形与渝渗理论提出一种氧气透过率预测模型,该模型能够在高阻氧材料体积分数条件下更准确地估算相融体系共混膜的氧气透过率.以聚酯/聚萘二甲酸乙二醇酯(PET/PEN)共混膜为例,通过扫描电镜分析共混膜微观形貌,确定PET/PEN共混膜中氧气渗透维数,并根据渗透维数结合文中提出的预测模型计算PET/PEN共混膜氧气透过率,最后通过实验数据验证该模型的有效性.结果 氧气在PET/PEN混合膜中的渗透可以简化为二维渗透.在低PEN体积分数条件下,现有模型和文中提出的预测模型均与实验结果高度吻合.该模型在高PEN体积分数条件下展现出了现有其他模型所没有的曲线趋势,能够更准确地描述高阻氧材料在共混膜体系中对氧气的阻隔作用.结论 文中提出的预测模型能够用于预测相融体系共混膜的氧气透过率.     

非织造材料表面生长ZnO薄膜的特性研究

室温下采用射频磁控溅射技术在涤纶纺粘非织造材料表面生长ZnO薄膜。通过扫描电子显微镜及原子力显微镜对ZnO薄膜的微观结构进行表征,用分光光度计测量样品的透光率。结果表明,ZnO薄膜为纳米级,其平均晶粒大小约为30 nm~55 nm。生长了ZnO透明纳米结构的非织造材料对紫外光有较强的吸收能力,在可见光区的透光率达60%以上。     

Characterization of Al2O3 thin films fabricated through atomic layer deposition on polymeric substrates

This paper reports on the fabrication of good quality Al₂O₃ thin films on flexible substrates including polyethylene naphthalate (PEN), polyethylene terephthalate (PET) and Polyamide at different temperatures down to 50 °C under very short water purging steps of 10 s. Al₂O₃ films with appreciable growth rates having good morphological, chemical, electrical and optical characteristics have been produced. Growth rates of 1.16, 1.14 and 1.15 Å/cycle have been observed at 50 °C for PET, PEN and polyamide substrates respectively. The surface morphology has been improved with the increase in deposition temperature. Low average arithmetic roughness of 0.88 and 0.78 nm have been recorded for the Al₂O₃ films deposited at 150 °C on PEN and polyamide respectively. The XPS analysis confirmed the fabrication of Al₂O₃ films without any carbon contamination and Al 2p, Al 2s and O 1s peaks were appeared at binding energies of 74, 119 and 531 eV, respectively. Excellent insulating properties were observed for the Al₂O₃ films and optical transmittance of more than 85 % was recorded in the visible region. The experimental results suggest that polymeric materials are excellent candidates to be used as substrates in the fabrication of Al₂O₃ thin films through atomic layer deposition.     

Adhesive properties of polypropylene (PP) and polyethylene terephthalate (PET) film surfaces treated by DC glow discharge plasma

In this study, the adhesive properties of the plasma modified polypropylene (PP) and polyethylene terephthalate (PET) film surfaces have been investigated. Hydrophilicity of these polymer film surfaces was studied by contact angle measurements. The surface energy of the polymer films was calculated from contact angle data using Fowkes method. The chemical composition of the polymer films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in surface feature of the polymer surfaces due to plasma treatment. The adhesion strength of the plasma modified film was studied by T-peel strength test. The results showed a considerable improvement in surface wettability even for short exposure times. The AFM and XPS analyses showed changes in surface topography and formation of polar groups on the plasma modified PP and PET surfaces. These changes enhanced the adhesive properties of polymer film surfaces.     

Glow discharge plasma-induced immobilization of heparin and insulin on polyethylene terephthalate film surfaces enhances anti-thrombogenic properties

Polyethylene terephthalate (PET) films were treated with DC glow discharge plasma followed by graft copolymerization with acrylic acid (AA) and polyethylene glycol (PEG). The obtained PET–PEG was coupled to heparin or insulin molecules. The surfaces were then characterized by contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The surface energies of the modified PET films were estimated using contact angle measurements, and the changes in crystallinity of the plasma-modified PET film surfaces were investigated by X-ray diffraction (XRD) analysis. The blood compatibilities of the surface-modified PETs were examined by in vitro thrombus formation, whole blood clotting time, platelet contact and protein adsorption experiments. The results revealed that the contact angle value decreased and that the interfacial tension between the modified PET films and blood protein was drastically diminished compared to unmodified PET film. The XPS results showed that the PET–AA surface containing carboxylic acid and the immobilized PET surface containing both carboxylic acid and amino groups exhibited a hydrophilic character, and AFM results showed marked morphological changes after grafting of AA, PEG and biomolecule immobilization. Heparin and insulin-coupled PET surfaces exhibited much less platelet adhesion and protein adsorption than the other surface-modified PET film surfaces.     

The Influence of High Pressure Treatment and Thermal Pasteurization on the Surface of Polymeric Packaging Films

Several common single layer films (PE‐HD, PE‐LD, PP‐BO, PA6‐BO and PET‐BO) and multilayer (PS/PE, PP‐BO/PEpeel and PET‐BO/PE) films were treated by either high pressure (600 MPa) or temperature (80 °C/90 °C) to simulate a high pressure or thermal pasteurization process. The samples were tested by atomic force microscopy (AFM), profile method and surface energy measurements to obtain information about the influence of the treatments on the surface topography and surface energy of the samples and by differential scanning calorimetry and by tensile testing concerning material properties. As key figures arithmetic surface roughness (by AFM at Pulsed Force Mode and profile method), surface energy by surface energy measurement and adhesion between tip and surface by AFM were extracted. Results indicate an influence of both high‐pressure processing and thermal‐processing on the surface roughness of biaxial oriented polymer films as single layer films. Laminated biaxially oriented polymer films showed no changes regardless of which processing was performed. The surface energy was hardly affected by both of the treatments for any stretched, non‐stretched, single or laminated films.     

Improved impermeability of PET substrates using oxygen and hydrogen plasma

A considerable decrease in permeability of polyethylene terephthalate (PET) films by means of surface plasma treatment in a reactive ion etching system is reported. The effects of oxygen and hydrogen radio frequency plasma on the surface properties of PET polymers are investigated by infrared spectroscopy, scanning electron microscopy (SEM), and X-ray photon spectroscopy (XPS). The surface morphology of the samples has been investigated using SEM and atomic force microscopy (AFM). The optical transmission spectroscopy has been studied further confirming the significant effect of O-plasma. Also the penetration of air through the treated substrates was investigated using a vacuum test. It is found that oxygen and hydrogen plasmas lead to about four-fold reduction in the penetration of air through the PET films, while the effect of hydrogen plasma has been more significant. In addition, oxygen plasma results in a rougher surface as observed both by AFM and SEM analyses. The formation of nanostructures on PET surfaces has been observed at plasma powers of 0.3 W/cm².     

Deposition of electrically conductive ceria/polypyrrole nanocomposite particles on flexible polyethylene naphthalate film via in situ photo-induced polymerization

To achieve a flexible and transparent conductive film via a simple method, ceria/polypyrrole nanocomposite particles were coated on Piranha-treated polyethylene naphthalate (PEN) film as the flexible substrate. Photo-induced polymerization was carried out by cerium (III) nitrate hexahydrate dissolved in acetonitrile and irradiation by UV wavelengths for 2 h. The effect of Piranha treatment on deposition of the conductive nanocomposite particles was examined. Deposited PEN samples prepared at various conditions were characterized using FESEM, AFM and STM, UV–vis spectroscopy, four-probe conductivity and contact angle measurements. Adhesion quality of the deposited nanoparticles was investigated by Scotch-tape test.     

Low-temperature preparation of flexible a-Si:H solar cells with hydrogenated nanocrystalline silicon p layer

In this paper we report on flexible a-Si:H solar cells prepared on polyethylene naphthalate (PEN) substrates using p-type hydrogenated nanocrystalline silicon thin films (p-nc-Si:H) as the window layer. The p-nc-Si:H films were prepared at low temperature (150 °C) using trimethylboron (TMB) as a dopant gas. The influence of the silane concentration (SC) on the electrical and structural properties of ultra-thin p-nc-Si:H as well as the performance of solar cells on PEN was investigated. The results show that the crystalline fraction and conductivity of p-nc-Si:H thin films diminished, while the deposition rate and RMS roughness of films increased, when the SC increases from 0.53% to 0.8%. For the a-Si:H solar cells on PEN with the non-textured electrodes, the best efficiency of 6.3% was achieved with the p-nc-Si:H thin films deposited at SC = 0.67%.     

The effect of high‐pressure food processing on the sorption behaviour of selected packaging materials

The sorption behaviour and flavour‐scalping potential of selected packaging films in contact with food simulant liquids (FSLs) (ethanol and acetic acid solutions) were evaluated after high‐pressure processing (HPP). The films used were monolayer polypropylene (PP), a multilayer (polyethylene/nylon/ethylene vinyl alcohol/polyethylene: PE/nylon/EVOH/PE), film and a metallized (polyethylene terephthalate/ethylene–vinyl acetate/linear low‐density polyethylene: metallized PET/EVA/LLDPE) material. D‐limonene was used as the sorbate and was added to each of the FSLs. After HPP treatment at 800 MPa, 10 min, 60°C, the amount of D‐limonene sorbed by the packaging materials and the amount remaining in the FSL was measured. Untreated controls (1 atm, 60°C and 40°C) were also prepared. Extraction of the D‐limonene from the films was performed using a purge/trap method. D‐limonene was quantified in both the films and the FSL, using gas chromatography (GC). The results showed that D‐limonene concentration, in both the films and the food simulants, was not significantly affected by HPP, except for the metallized PET/EVA/LLDPE. Significant differences in D‐limonene sorption were found in comparison with the control pouches. The results also showed that changes in temperature significantly affected the sorption behaviour of all films. Copyright © 2004 John Wiley & Sons, Ltd.     

New aspects of the microstructure of glassy PET/PEN blends as revealed by microhardness

The microhardness of films of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) blends prepared by co-precipitation from solution followed by melt-pressing and quenching was determined. The miscibility, transesterification and crystallization properties of these blended films were reported previously [1]. The PET/PEN compositions chosen were 10/90, 30/70, 44/56, 60/40, 70/30 and 90/10. The microhardness of films was notably affected by the composition. It is shown that the deviation of microhardness from the additivity law of the single components depends on the time for which the blend was melt-pressed before quenching in ice water. The results are discussed in light of changes occurring from the initial two-phase structure of the single components through the one-phase structure up to the PET-co-PEN obtained by transesterification of the two components. This revised version was published online in November 2006 with corrections to the Cover Date.     

Organic photodiodes on flexible substrates

The fabrication of organic photodiodes on solution cast indium tin oxide (ITO) bottom electrodes on flexible substrates is described. ITO coatings with a sheet resistance of 2 to 3 kΩ/sq are produced by gravure printing process on PEN (polyethylene 2,6-naphthalate) films. The ITO films are directly used as transparent bottom electrodes for organic photodiodes (OPD). Furthermore, first experiments to integrate one of these OPDs in an all-organic opto-chemical sensor are successfully demonstrated. The implementation of OPDs as detectors in applications such as integrated sensors demands a fabrication of these devices on flexible substrates. For these applications the OPDs on printed ITO on PEN are especially suitable.     

Deformation of spherulitic polyethylene thin films

Thin spherulitic films of polyethylene (PE), made by casting from xylene solution, were deformed on copper grids and their deformation microstructure studied using optical and transmission electron microscopy. A range of molecular weights, branch amounts and types, and thermal histories was used to study the influence of sample microstructure on the deformation behaviour. The spherulite boundaries were the weakest regions of spherulitic structures in all types of PE. Higher strains were generally required to deform the interiors of spherulites, which deformed by a different mechanism. The toughness of the films was increased by increasing the tie-molecule density and disentanglement resistance, to strengthen spherulite boundaries. Three methods for increasing the toughness were demonstrated and were: (1) decreasing the crystallization time in order to increase the tie-molecule density, (2) increasing the molecular weight in order to increase the tie-molecule density, and (3) incorporating short-chain branches on the main chains in order to increase the tie-molecule density and increase the disentanglement resistance. Incorporation of short-chain branches was shown to be the most effective way of strengthening spherulitic structures, with the toughest films being those made of branched PE that had been crystallized rapidly. The branch length and spherulite size were found to be unimportant. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of high‐pressure food processing on the mass transfer properties of selected packaging materials

The effect of high‐pressure processing (HPP) on the total migration into distilled water and olive oil and on the barrier properties of four complex packaging materials were evaluated. The films were polyethylene/ethylene‐vinyl‐alcohol/polyethylene (PE/EVOH/PE), metallized polyester/polyethylene, polyester/polyethylene (PET/PE), and polypropylene‐SiOx (PPSiOx). Pouches made from these films were filled with food simulants, sealed and then processed at a pressure of 400 MPa for 30 min, at 20 or 60°C. Pouches kept at atmospheric pressure were used as controls. Prior to and after treatment, all films were evaluated for their barrier properties (oxygen transmission rate and water vapour transmission rate) and ‘Total’ migration into the two food simulants. In the case of water as the food stimulant, a low ‘Total’ migration was observed and even a lower one after the HPP treatment. In the case of oil as the food simulant, a higher ‘Total’ migration was found compared to the control as a result of damage to the structures during the HPP treatment. The gas permeability of the films increased after the HPP, compared to the control, due to damages in the structure caused during the treatment. The PET/PE film presented minimum changes in properties after HPP. Copyright © 2010 John Wiley & Sons, Ltd.     

Atomic force microscopy of plastically deformed polyethylene subjected to tensile deformation at varying strain rates

Abstract

The surface damage induced during tensile deformation of polyethylene at different strain rates was studied by atomic force microscopy (AFM) operated in tapping mode, before and subsequent to uniaxial tensile plastic deformation. Atomic force microscopy revealed striking differences in the deformed microstructures up to the nanoscale range. The surface of undeformed polyethylene was characterised by ribbonlike fibrils of width 0·25 νm and surface features of height about 20–60 nm. Fibrils were considered to consist of microfibrils of width 0·03–0.04 νm. Small scan (30 × 30 nm) AFM images provided details of microfibrils containing chains of molecules of ~ 0·5 nm wide. Tensile deformation in the plastic region involved stretching of fibrils and microfibrils resulting in the formation of surface openings. The ability of the ribbonlike surface fibrils and microfibrils to stretch, merge, and acquire an oriented and flat structure increased with increase in strain rate in the uniaxial tensile test. Also, with increase in strain rate the chains of molecules unfold and align to produce an oriented and elongated structure. The impact of deformation on amorphous regions could only be observed at high strain rates.     

Contact angle analysis of low-temperature cyclonic atmospheric pressure plasma modified polyethylene terephthalate

Polyethylene terephthalate (PET) films are modified by cyclonic atmospheric pressure plasma. The experimentally measured gas phase temperature was around 30 °C to 90 °C, indicating that this cyclonic atmospheric pressure plasma can treat polymers without unfavorable thermal effects. The surface properties of cyclonic atmospheric pressure plasma-treated PET films were examined by the static contact angle measurements. The influences of plasma conditions such as treatment time, plasma power, nozzle distance, and gas flow rate on the PET surface properties were studied. It was found that such cyclonic atmospheric pressure plasma is very effective in PET surface modification, the reduced water contact angle was observed from 74° to less than 37° with only 10 s plasma treatment. The chemical composition of the PET films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in PET surface feature of the polymer surfaces due to plasma treatment. The photoemission plasma species in the continuous cyclone atmospheric pressure plasma was identified by optical emission spectroscopy (OES). From OES analysis, the plasma modification efficiency can be attributed to the interaction of oxygen-based plasma species in the plasma with PET surface. In this study, it shows a novel way for large scale polymeric surface modification by continuous cyclone atmospheric pressure plasma processing.     

PEN单聚合物复合材料的热压制备工艺与性能

为了实现聚萘二甲酸乙二醇酯(PEN)单聚合物复合材料(SPCs)的制备,使用DSC热分析法确定了制备PEN SPCs的加工温度范围,根据PEN的过冷性质热压制备了PEN SPCs.通过SEM研究了PEN SPCs的界面粘结性,使用万能试验机比较了PEN SPCs与未增强PEN的力学性能.研究结果表明:PEN SPCs中的基体PEN树脂与增强体PEN纤维之间具有良好的界面粘结性;制备的PEN SPCs的拉伸强度为224 MPa,是未增强的PEN拉伸强度的3.6倍.