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Reversible addition-fragmentation chain transfer (RAFT) agent was added into a simultaneous radiation grafting system and its effects on graft polymerization and homopolymerization were investigated. Chloromethylstyrene (CMS) was graft polymerized onto ethylene-tetrafluoroethylene copolymer (ETFE) films under γ-ray sources via simultaneous irradiation. The non-grafted poly(CMS) in the grafted films were extracted by xylene at 120 °C. The poly(CMS) was characterized by NMR and GPC instruments. Addition of the RAFT agent suppressed both graft polymerization and homopolymerization. However, under a high concentration of RAFT agent, the homopolymerization in the monomer solution could occur through a typical RAFT polymerization while polymerization in the ETFE films proceeded via RAFT and conventional radical polymerization, resulting in poly(CMS) in the ETFE films with molecular weight dispersity higher than 1.0 but lower than that without RAFT agent. Furthermore, it was found that the molecular weight of the poly(CMS) in the ETFE films was several times higher than that of the poly(CMS) in the monomer solution.

To study the properties of ethylene-tetrafluoroethylene (ETFE) copolymer materials in wings of unmanned aerial vehicles, electron beam irradiation was performed to prepare the corresponding irradiated ETFE for air atmosphere. All these irradiated samples were characterized by SEM, FTIR, TGA, DSC, flexural fatigue measurement and tensile test. The results revealed that the logarithm of the flexural fatigue of ETFE decreased with the irradiation dose increased, which could be explained by the growing effect of chain scission. The elongation-at-break decreased with the dose increase, while the tensile strength was kept constant. As shown in FTIR results, the scission of the macromolecular chains induced by irradiation resulted in the relative oxidation of groups, such as carbonyl groups. TGA analysis showed that the initial and maximum decomposition temperatures increased with dose increase due to the inherent cross-linking structures. Besides, the number of the crystalline regions with regular formation (such as crystallization temperature, crystallization degree and crystallization enthalpy) decreased with the dose increase as a result of the formation of unsaturated structures after the elimination of HF from the broken chains, which was confirmed by FTIR. It is expected that our findings can provide important information to promote the development of aircraft materials.

Ethylene-tetrafluoroethylene (ETFE) fibers were fabricated by a single-screw melt spinning machine at different drawing roll speed ratios and different drawing roll temperatures. Thermogravimetric analyzer, differential scanning calorimetry, X-ray diffraction (XRD), digital fiber sound velocimeter and single fiber strength testers were used to discuss the impacts of spinning processes on the structure and performance of ETFE fibers. The results indicated that four different fibers showed a similar melting temperature at around 257℃. XRD results revealed that the largest crystallinity of four ETFE fibers was 41.1%. As the drawing temperature increased, the crystallinity of ETFE fibers decreased and the grain size increased. The breaking strength of four as-spun ETFE fibers reached up to 1.12 cN/dtex. The minimum shrinkage of ETFE fibers at 200℃ was 7%, and it was only 1% at most below 150℃. The maximum creep strain of ETFE fibers was 6% when the loading capacity was 20% of the breaking strength at room temperature and ETFE fibers had a high recovery ratio of >90% after the load was removed. Moreover, ETFE fibers showed exceptional corrosion resistance and good performance of irradiation resistance.

In this paper, we discuss nonthermalized para -positronium ( p -Ps) in fluorinated polymers [Polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene copolymer (ETFE), polyvinyl fluoride (PVF)], and silica glass based on the Tao-Eldrup model, which takes account of Ps captured at different energy levels. Comparison of the energy of p -Ps estimated by positron annihilation age-momentum correlation (AMOC) with the calculation based on the Tao-Eldrup model reveals that p -Ps increasingly occupies higher energy levels in the polymers as more hydrogen is substituted by fluorine. In silica glass consisting of silicon (heavier than fluorine) and oxygen only the contribution of the lowest excited levels may be significant. These results are qualitatively in line with the previous observation for the energy dissipation of ortho -positronium ( o -Ps) in nanoporous silica films.

The cost of materials is one of the biggest barriers for wastewater driven microbial fuel cells (MFCs). Many studies use expensive materials with idealistic wastes. Realistically the choice of an ion selective membrane or nonspecific separators must be made in the context of the cost and performance of materials available. Fourteen membranes and separators were characterized for durability, oxygen diffusion and ionic resistance to enable informed membrane selection for reactor tests. Subsequently MFCs were operated in a cost efficient reactor design using Nafion, ethylene tetrafluoroethylene (ETFE) or polyvinylidene fluoride (PVDF) membranes, a nonspecific separator (Rhinohide), and a no-membrane design with a carbon-paper internal gas diffusion cathode. Peak power densities during polarisation, from MFCs using no-membrane, Nafion and ETFE, reached 67, 61 and 59 mWm(-2), and coulombic efficiencies of 68±11%, 71±12% and 92±6%, respectively. Under 1000 Ω, Nafion and ETFE achieved an average power density of 29 mWm(-2) compared to 24 mWm(-2) for the membrane-less reactors. Over a hypothetical lifetime of 10 years the generated energy (1 to 2.5 kWhm(-2)) would not be sufficient to offset the costs of any membrane and separator tested.

Compared to their predecessors, the next generations of aircrafts will be more electrified, require more electrical power and operate at higher voltage levels to meet strict weight and volume constraints. The combined effect of low-pressure environments, increased voltage levels and compact designs intensifies the risks of premature insulation degradation due to electrical discharge activity. This paper studies the resistance to surface discharges of PTFE (polytetrafluoroethylene) and ETFE (ethylene tetrafluoroethylene), two insulation materials widely used in today’s aircraft wiring systems due to their outstanding properties, such as a wide temperature operation range and a high dielectric strength. The study is carried out in a low-pressure chamber, which was pressurized within the pressure range of 10–100 kPa that includes most aircraft applications. There is a compelling need for experimental data to assess the resistance of insulation materials to surface discharges at a very early stage as a function of the environmental pressure. Data on resistance to surface discharges in low-pressure environments for aeronautical applications are lacking, while most standards for insulation systems are based on tests under standard pressure conditions. The results provided in this work can be useful to design wiring systems for future more electric aircrafts, as well as to design fault detection systems for an early detection and identification of faults related to surface discharges. Therefore, the data and analysis included in this paper could be of great interest to design and develop insulation systems for wiring systems and standard assessment methods, as well as to design fault detection strategies for the early detection and identification of surface discharges for future generations of more electric aircrafts.

The fluororesin membrane emerges as an ideal chemical-protective clothing material due to its excellent permeation resistance. However, using a fluororesin membrane with a low surface energy for compounding fabrics is very challenging. Herein, we demonstrate a strategy to modify the surface of a poly(ethylene-alt-tetrafluoroethylene) (ETFE) membrane by the atmospheric pressure dielectric barrier discharge (DBD) of plasma under different working voltages, processing times, and concentrations of acrylic acid (AA) in a helium (He) atmosphere. The increase in the hydrophilicity of the ETFE membrane is confirmed by the wettability test, which shows a significant decrease in the water contact angle, from 96° to 50°, after plasma modification. The interfacial T-peel strength of an ETFE membrane composited with polyester fabric increased from 0.53 N/cm to 13.64 N/cm after plasma modification. Significantly, the T-peel strength of the composite using a modified ETFE membrane with ultrasonic washing could still reach 11.75 N/cm. Various characterization methods clearly disclosed the physical and chemical changes on the ETFE membrane surface, such as introducing the polar -COOH group at a nano-level, improving the roughness, decreasing the ratios of the F/C element, and increasing the ratios of the O/C element, suggesting using nano-level grafted polyacrylic acid (g-PAA) on the surface of the membrane by DBD.

Optical fiber composite insulators are essential for photoelectric current measurement, yet insulation failure at embedded optical fiber interfaces remains a major challenge to long-term stability. This study proposes a strategy to replace conventional silicone rubber with cycloaliphatic-like epoxy resin (CEP) as the shed-sheathing material. Three optical fibers with distinct outer coatings, ethylene-tetrafluoroethylene copolymer (ETFE), thermoplastic polyester elastomer (TPEE), and epoxy acrylate resin (EA), were evaluated for their interfacial compatibility with CEP. ETFE, with low surface energy and weak polarity, exhibited poor wettability with CEP, resulting in an interfacial tensile strength of 0 MPa, pronounced dye penetration, and rapid electrical tree propagation. Its average interfacial breakdown voltage was only 8 kV, and the interfacial leakage current reached 35 μA after hygrothermal aging. In contrast, TPEE exhibited high surface energy and strong polarity, enabling strong bonding with CEP, yielding an average interfacial tensile strength of approximately 46 MPa. Such a strong interface effectively suppressed electrical tree growth, increased the average interfacial breakdown voltage to 27 kV, and maintained the interfacial leakage current below 5 μA even after hygrothermal aging. EA exhibited moderate interfacial performance. Mechanism analysis revealed that polar ester and ether groups in TPEE enhanced interfacial electrostatic interactions, restricted the mobility of CEP molecular chain segments, and increased charge traps. These synergistic effects suppressed interfacial charge transport and improved insulation strength. This work offers valuable insight into structure–property relationships at fiber–resin interfaces and provides a useful reference for the design of composite insulation materials.

A method was developed for generating transparent and hydrophobic nanolayers chemisorbed onto flexible substrates of ethylene tetrafluoroethylene–silicon oxide (ETFE–SiOx). In particular, the effect of the deposition time and of the precursor molecule on the nanocoating process was analyzed with the aim of pursuing an optimization of the above method in an industrial application perspective. It was found that precursor molecule of triethoxysilane allowed to obtain better hydrophobic properties on the SiOx surface in shorter times compared to trichlorosilane, reaching the 92 % of final contact angle (CA) value of 106° after only 1 h of deposition. The optical properties and surface morphology were also assessed in function of time, revealing that an initial transparency reduction is followed by a subsequent transmittance increase during the self assembly of fluoroalkylsilanes on the SiOx surface, coherently with the surface roughness analysis data. Encouraging results were also obtained in terms of oleophobic properties improvement of the nanocoated surfaces.

Rapid urbanization and unplanned agricultural land expansion have caused widespread deforestation and exacerbated global food and water security (United Nations 2024). Rooftop Greenhouses (RTGs) have been recognized as a compelling urban agriculture strategy by utilizing unused roofs in existing buildings and locally producing crops. In addition to various social and environmental benefits, RTGs enhance energy efficiency in both host buildings and greenhouses by acting as additional insulation and reducing excessive solar heat gain. Moreover, installing Building Integrated Semi-Transparent Photovoltaic (BISTPV) systems into RTGs can further reduce cooling demands and utilize the generated electricity on site. Despite their potential, the widespread implementation of RTGs with BISTPV systems has been limited by an absence of optimized design methodologies. This study proposes design concepts for modular RTGs equipped with BISTPV systems, aiming to minimize energy consumption and allow year-round cultivation in Montreal's climate. To accommodate different rooftop sizes and layouts, two RTG modules are developed-one featuring a mono-pitched roof and the other with an even-pitched roof-allowing for either standalone or combined applications. The indoor thermal behavior and energy performance of these modules are evaluated using Resistance-Capacitance (RC) models developed with the explicit finite difference method. Moreover, a parametric analysis is conducted using key design variables that are identified through a global variance-based sensitivity analysis. As a result, the insulated glass units were the most effective RTG covering material, having the lowest cooling load in summer compared to the polycarbonate sheets and Ethylene tetrafluoroethylene (ETFE) films. The optimized design configurations of both RTG modules successfully provided adequate growing conditions for leafy greens across the three design days in winter, spring, and summer. This research confirms that adequate Day Light Integral (DLI) levels can be satisfied with a BISTPV system, respectively covering 75% and 40% of Module 1 and 2 roofs. Additionally, the proposed designs generally achieve NetZero Energy (NZE) status by maximizing the profitability of BISTPV systems and reducing heating and cooling loads, except for Module 2 on the summer design day. The excessive cooling demand during the summer months presents the need to optimize the heating, ventilation, and air-conditioning (HVAC) systems and to explore various climate control strategies for improved efficiency. Therefore, this research establishes a foundation for further advancements in building integrated agriculture and offers valuable insights for designing modular RTGs with BISTPV systems in cold climates.