ETFE Films Research Articles

Influence of Ageing on Optical, Mechanical, and Thermal Properties of Agricultural Films.

Plastic films utilized as greenhouse coverings play a vital role in safeguarding plantations from diverse weather conditions like sunlight, rain, hail, and wind. It is essential for these films to preserve their properties even after extended exposure to sunlight and water, while also maintaining transparency to support the unhindered growth of plants. The purpose of the study was to compare the properties of three types of plastic films: low density polyethylene diffuse film, low density polyethylene clear film, and ethylene tetrafluoroethylene film, before and after their ageing in weather test chamber with xenon-arc light in the presence of moisture. Two distinct types of PE films were chosen based on their suitability for specific regions in Croatia, whereas ETFE film was chosen as a potential new material that is gaining popularity across various industries, including agriculture. The properties investigated were tensile properties, transmittance by spectral analysis, and viscoelastic properties by dynamic mechanical analysis. Also, untreated films and the ones exposed to artificial ageing were compared by means of Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. The administered tests revealed a certain level of property degradation due to ageing in all three films. However, none of the films showed a substantial level of deterioration, indicating their suitability as greenhouse coverings.

Создание комфортных условий эксплуатации выставочных комплексов в жарком климате

Purpose: To consider the possibility of using modern innovative coating materials, and in particular ETFE film, in the enclosure structures when designing public buildings in different natural and climatic conditions, with the example of regions with hot climates. Method: Generalization of design principles, including those for hot climates. Analysis of climatic parameters of hot climate regions which have a significant impact on comfortable conditions of people staying in public buildings, characterized by multifunctionality, large spatial dimensions, high occupancy rates, and other factor s. To show the possibility of providing favorable conditions for people staying in such buildings in different ways: through planning and design; improvement of adjacent areas; the location of the building. To carry out the analysis of domestic and foreign experience of application of means of sun protection of buildings. To develop space-planning and structural solutions of the exhibition complex. To evaluate the effectiveness of the proposed solution through a computational study. Results: The results of the research of a range of measures aimed at improving the conditions for comfortable stay of people in the exhibition complexes are presented. The constructive solution of sun protection of the exhibition complex taking into account physical and mechanical properties of the membrane system and climatic conditions of the construction areas has been proposed. Practical significance: The versatility of using dome structures as enclosures is demonstrated. The advantage of using innovative covering materials as an alternative to traditional materials is shown.

Investigation of chemical degradation and water states in the graft‐type polymer electrolyte membranes

AbstractChemical degradation in the presence of H2O2 aqueous solution and water states of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs) with grafting degree (GD) of 8.8%–21.1% are investigated using Fourier‐transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), and electrochemical impedance spectroscopy (EIS). The ETFE‐PEMs show the complete detachment at the α‐hydrogen atoms of the whole graft PSSA chains from the ETFE backbones, while their precursor polystyrene‐grafted ETFE films do not. This chemical degradation exhibits independently with GDs and takes place even at very low GD (<10%). Water molecules of the membranes dried at 40°C are not completely de‐absorbed. The remains are partial non‐bonded water molecules, which are assumed to locate within the lamellar amorphous domains (constrained water molecules) of the crystalline phases. These constrained water molecules exist independently with the PSSA groups and do not detach together with them during the degradation. Note that the water molecules remained at 40°C show the additional contribution of 18%–19% to the total water uptake but do not contribute clearly to the conductance.

A Raman Spectroscopic Study of Radiation-Grafted Anion-Exchange Membranes Containing Different Anions

Anion exchange membranes (AEM) are being developed for use in a variety of electrochemical energy systems, such as alkaline membrane fuel cells, AEM-based electrolysers, reverse electrodialysis (RED), and redox flow batteries (RFB). The AEMs used will contain a variety of anions, depending on the application. For fuel cells and electrolysers (H2 generating or CO2 conversion), then alkaline anions such as OH-, CO3 2-, and HCO3 - are important. For RED cells and RFBs, non-alkali anions such as Cl-, HSO4 -, and SO4 2- are more relevant. If an AEM is synthesised using a methyl iodide reaction, then monitoring the ion-exchange of the resulting "as-synthesised" I- forms to other forms, such as Cl-, is important as it is well known that it can be difficult to completely ion-exchange soft anions such as I- out of AEMs (particularly those containing aromatic cationic groups).This presentation will highlight some initial results obtained from an on-going Raman spectroscopic study of radiation-grafted AEMs (RG-AEM). This study was initiated to see if Raman spectro-microscopy can be used to identify the anion form of a RG-AEM by looking at the shifts and intensity changes of Raman peaks as a function of anion. The RG-AEMs will be made from either the grafting of vinylbenzyl chloride onto ETFE (followed by reaction with amines such as trimethylamine, imidazole and pyridine) or the grafting of alternative monomers such as vinylpyridine onto ETFE (followed by reaction with methyl iodide).The below Figure shows Raman spectra (Renishaw inVia Raman microscope: 785 nm laser, 1800 lines mm-1 grating, and x20 objective giving a Airy spot diameter of ca. 3 μm) of a RG-AEM made from the grafting of vinylpyridine onto ETFE films (with a final methyl iodide reaction) in both the I- and Cl- forms (three spectra each):. Figure 1

Investigation of fluorine-based release agents for structural adhesive bonding of carbon fibre reinforced plastics

Peel plies can be used during the manufacture of fibre-reinforced plastics for two reasons: to protect the surface during transport and storing the parts as well as during subsequent work steps, such as adhesive bonding, the removal of the peel ply can result in bondable surface with required surface characteristics. However, the use of peel plies is not straightforward. It can be difficult to remove peel plies and a surface produced by a peel ply is altered in terms of roughness and elemental composition. In the present work, the influence of fluorine-based release agents on adhesive joining of carbon fibre reinforced composites is investigated. Within the scope of the screening, 14 fluorine-based release agents—ETFE release films, PTFE coated glass fabrics as well as fabrics made of PTFE fibres—were investigated. Preliminary studies (Meer, in: Deutscher Luft- und Raumfahrtkongress 2014, Augsburg, 2015) have shown that ETFE films have advantages in terms of adhesion. The study covers a number of aspects: the determination of the tear strength of the release agent by peel test; the determination of the element composition (XPS) and surface characteristics (SEM) before and after atmospheric pressure plasma pre-treatment, characterization the topology and the characterization of the adhesive strength by centrifugal adhesion test.

Study on the structure of polymer electrolyte membrane using small angle X-ray scattering and positron annihilation spectroscopy

The structure of poly (styrenesulfonic acid)- grafted poly(ethylene-co- tetrafluoroethylene) polymer electrolyte membrane (ETFE-PEM) was investigated by comparison with those of precursor original ETFE film and styrene-grafted films (grafted-ETFE) using positron annihilation lifetime spectroscopy (PALS) and small angle Xray scattering (SAXS). PALS of these samples indicated that there were two lifetime components, which were assigned to the annihilation of ortho- Positronium (o-Ps). The two types of o-Ps relate to the free volume at sub nanoscale locating in the crystalline and amorphous phases. SAXS profiles of these samples indicated the presence of lamellar stacks andlamellar grains. Sizes of lamellar stacks and lamellar grains varied significantly during the graftingprocess, whereas only change a little bit at sulfonation process and at wet state. A compination of PALS and SAXS allowed us to investigate the structures of ETFEPEMs with scale ranging from several Ångströms to micrometer.

Facile synthesis and properties of a cation exchange membrane with bifunctional groups prepared by pre-irradiation graft copolymerization.

A new type of a cation exchange membrane named ETFE-g-poly(AA-co-SSS) with bifunctional groups was synthesized by a one-step method. Its preparation by an electron beam-induced pre-irradiation grafting method and the effects of reaction temperature, monomer concentration, pH value of the grafting solution, storage time and temperature of the irradiated poly(ethylene-alt-tetrafluoroethylene) (ETFE) films on the grafting yield were studied. A total concentration of 2 mol L−1 of monomers was found to be beneficial for acrylic acid (AA) and sodium styrene sulfonate (SSS) co-grafting onto the ETFE films. Infrared spectroscopic analysis of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups. The contact angle of the grafted membrane decreased from 94.3 to 46.7° with the increase in grafting yield. The higher the grafting yield, the faster the response and recovery rate with respect to humidity. AFM images showed that the diameter of the grafted chains on the surface of ETFE membranes was about 30 nm. The voltage of the grafted membrane was stable after 100 cycles of charge–discharge; thus, the prepared membranes have great potentials to be used as separators in secondary batteries.

Tensile Characteristics of ETFE Film According to the Specimen Type

Tensile Characteristics of ETFE Film According to the Specimen Type

Intensifying radiation induced grafting of 4-vinylpyridine/glycidyl methacrylate mixtures onto poly(ethylene-co-tetrafluoroethylene) films using ultrasound

A new ultrasound-aided method was used to enhance grafting of 4-vinylpyridine (4-VP) and glycidyl methacrylate (GMA) monomers mixtures onto electron beam (EB) irradiated poly(ethylene-co-tetrafluoroethylene) (ETFE) film for the first time. The effects of reaction parameters such as absorbed dose, monomer concentration, reaction time on both of degree of grafting (DG) and grafting efficiency (GE) were investigated under sonication and conventional grafting at similar temperatures. Fourier transform infrared (FTIR) and atomic force microscopy (AFM) were used to monitor the impact of the applied ultrasound on composition and surfaces of the grafted films whereas 1H-NMR was used to investigate composition of the grafting residues. The ultrasound-aided grafting of 4-VP/GMA was found to enhance both of DG% and GE remarkably. Moreover, it produced grafted ETFE films having smoother surfaces without homopolymer contamination compared to grafted films obtained from conventional grafting. The results of this study suggest that the use of ultrasound is a promising way for intensifying grafting process and improving its economy.

Morphological Study of Poly(vinylbenzyl chloride)-Grafted Poly(ethylene-co-tetrafluoroethylene) [ETFE-g-PVBC] Films Using Small-Angle Neutron Scattering Analysis.

In this study, the effect of degree of the grafting and crosslinking on the morphology of the crystalline domain in poly(vinylbenzyl chloride)-grafted poly(ethylene-co-tetrafluoroethylene) [ETFE-g-PVBC] films was investigated using a SANS (small-angle neutron scattering) analysis. The grafted films can be used as a precursor for ion-exchange membrane. ETFE-g-PVBC films with various degrees of cross-linking were prepared by a simultaneous irradiation grafting of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) onto an ETFE film. The SEM-EDX (scanning electron microscopy-energy dispersive X-ray spectroscopy) results of a cross-sectional distribution of ETFE-g-PVBC films showed that the chlorine atoms were well-distributed throughout the films. SANS profiles of the PVBC-grafted films in the absence of a DVB crosslinker showed that the crystalline domain peaks were observed and the peak maximum position shifted significantly from 0.032 Å-(-1) to 0.02 Å(-1) with an increase in the degree of grafting. However, peak maximum positions of the PVBC-grafted films in the presence of a DVB crosslinker shifted slightly from 0.02 Å(-1) to 0.024 Å(-1) with an increase in the amount of DVB monomer at same degree of grafting. These results indicate that the degree of grafting and crosslinking affect the morphology of the crystalline domain in the ETFE-g-PVBC films.

ETFE 필름의 2축 인장특성 및 텐션방식 막구조물의 응력완화 거동에 관한 실험적 연구

Until recently, almost all ETFE film structures that have been erected is the cushion type because there are problems at lower allowable strength under elastic range and viscosity behaviour such as creep and relaxation of ETFE films under long-term stresses. But the number of tension type structures is currently increasing. This paper proposes the stretch fabrication of ETFE film to verify the applicability of ETFE films to tensile membrane structures. First of all, to investigate the possibility of application on tensile membrane structures, the stretch fabrication test is carried out, and it is verified that it is possible to increase the yield strength of the film membrane structures. After simulating the experiment also carries out an analytical investigation, and the effectiveness of the elasto-plastic analysis considering the viscous behavior of the film is investigated. Finally, post-aging tension measurement is conducted at the experimental facilities, and the viscosity behavior resulting from relaxation is investigated with respect to tensile membrane structures.

Kinetic behaviour of graft copolymerisation of nitrogenous heterocyclic monomer onto EB-irradiated ETFE films

Kinetic behaviour of graft copolymerisation of a nitrogenous heterocyclic monomer, 4-vinylpyridine (4-VP), onto electron beam irradiated poly(ethylene-co-tetra- fluoroethylene) (ETFE) films was investigated in correla- tion with reaction parameters (absorbed dose, monomer concentration and reaction temperature). This was estab- lished by determination of initial polymerisation rate (rp0), characteristic radical recombination rate (c) and delay time (t0). The orders of the dependence of the initial rate of grafting on the absorbed dose and monomer concentration were found to be 2.28 and 3.49, respectively. The effect of temperature was investigated in the range of 50-70 C and the activation energy was determined. The incorporation of poly(4-VP) grafts and the accompanied chemical changes in the grafted ETFE films were monitored using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, respectively. The results of the present study showed that a quantitative kinetic description for grafting of 4-VP onto ETFE can be established and the degree of grafting can be tuned by controlling the reaction parameters.

ETFE필름의 연신성형에 의한 장력막구조의 고내력화 실험 및 해석적 연구

Most of the structural forms in which ETFE film is used are the cushion(pneumatic membrane structures) and tension type(tensile membrane structures), which have been generally accepted to be the most efficient forms. Tensile membrane structures are pulled outward from the exterior to introduce initial stress. And such structures offer the advantage of a natural shape formed by tensile stress and eliminate the need for blast air. Recently, the number of tension type structures is increasing. However, there are problems of creep and relaxation of ETFE films under long-term stresses. In this paper, the stretch fabrication method is proposed for stretching the film into the plastic region during initial tensioning as a way to increase its strength. And its effectiveness is confirmed by investigating experimental and analytical test using ETFE films.

Performance and durability of MEA prepared with crosslinked ETFE-g-PSSA(DVB) membranes for direct methanol fuel cells using high concentration methanol

Proton exchange membranes were prepared by γ-ray radiation-induced grafting onto ETFE films, crosslinking with styrene/divinylbenzene (DVB) mixtures and a subsequent sulfonation. Effects of the DVB content on the membrane properties such as ion exchange capacity (IEC), proton conductivity, and methanol permeability were investigated. Membrane-electrode assemblies (MEA) containing the prepared membranes were fabricated for direct methanol fuel cells (DMFC), and the MEA performance was examined in operation with various concentrations of methanol. Durability of the MEAs was investigated using a 3M methanol solution for 1000h, and the polarization curves and impedance spectra were measured. Physicochemical properties of catalysts and membrane before and after the long-term operation were analyzed by TEM, XRD, IEC, and proton conductivity. Performance and durability of the selected membranes were also confirmed in the operation of a 6-cell stack with 3M methanol solution.

Imidazolium Cation Based Anion-Conducting Electrolyte Membranes Prepared by Radiation Induced Grafting for Direct Hydrazine Hydrate Fuel Cells

Graft-type anion-conducting electrolyte membranes (AEMs) with imidazolium cations on graft polymers were synthesized through radiation-induced graft polymerization of N-vinylimidazole (NVIm) on poly(ethylene-co-tetrafluoroethylene) (ETFE) films, followed by N-propylation and ion-exchange reactions. The N-propylation proceeded quantitatively, whereas the ion-exchange reactions in 1 M KOH at 60°C were accompanied by partial β-elimination of the imidazolium cations to yield copolymer grafts consisting of poly-(1-vinyl-3-propylimidazolium hydroxide) and double bonds (polyethyne) (AEM2), which exhibited an ion-exchange capacity (IEC) of 0.85 mmol g−1 and ionic conductivity of 10 mS cm−1. AEM2 showed alkaline stability at 60°C but it gradually degraded at 80°C for ca. 150 h. The copolymer-type AEM (AEM3) with an IEC of 1.20 mmol g−1 was prepared through the copolymerization of NVIm with styrene on ETFE films, followed by the same N-propylation and ion-exchange reactions. AEM3 was characterized to be a terpolymer, owing to partial β-elimination and showed higher alkaline durability in 1 M KOH at 80°C. As a result, it exhibited higher conductivity (>10 mS cm−1) for 250 h. Therefore, alkylimidazolium cations in copolymer grafts are a promising anion conducting group for alkaline-durable AEMs. A maximum power density of 75 mW cm−2 is obtained for AEM3 in a direct hydrazine hydrate fuel cell.

Tensile Strength Characteristics on ETFE Film for Membrane Roof System

ETFE is the abbreviation of Ethylen Tetra Fluoro Etylene, a sort of colorless and transparent granules. The advantage ETFE film has daylight transmission and chemical resistance, the aging resistance and lightweight. The thickness of ETFE film is used to from 50μm to 300μm and tensile strength of ETFE film changes from 40MPa to 60MPa and the tensile strain at break can get to about 300-400%. In this paper, ETFE film carried out the tensile proprieties, such as the tensile strain at break, the tensile strength are examined.

Solvent effect on post-irradiation grafting of styrene onto poly(ethylene-alt-tetrafluoroethylene) (ETFE) films

Radiation-induced grafting of styrene onto ETFE films in different solvent was investigated after simultaneous irradiation (in post-irradiation condition) using a 60Co source. Grafting of styrene followed by sulfonation onto poly(ethylene-alt-tetrafluoroethylene) (ETFE) are currently studied for synthesis of ion exchange membranes. The ETFE films were immersed in styrene/toluene, styrene/methanol and styrene/isopropyl alcohol and irradiated at 20 and 100kGy doses at room temperature. The post-irradiation time was established at 14day and the grafting degree was evaluated. The grafted films were sulfonated using chlorosulfonic acid and 1,2-dichloroethane 20:80 (v/v) at room temperature for 5h. The degree of grafting (DOG) was determined gravimetrically and physical or chemical changes were evaluated by differential scanning calorimeter analysis (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The ion exchange capacity (IEC) values showed the best performance of sulfonation for ETFE membranes grafted in toluene solvent. Surface images of the grafted films by SEM technique have presented a strong effect of the solvents on the films morphology.

전조사법에 의한 PVBC-g-ETFE 필름 제조 시 용매의 영향 평가

본 연구에서는 방사선 전조사법으로 ETFE(polyethylene-co-tetrafluoroethylene) 불소고분자 필름에 VBC (vinylbenzyl chloride) 단량체를 그래프트할 경우 사용되는 용매의 영향을 평가하였다. ETFE 필름을 전자선을 조사하 여 필름에 라디칼을 형성시킨 후 톨루엔, 햅탄, 이소프로판올 등 다양한 용매로 희석된 VBC 단량체 혼합물에 넣어 그래 프트 반응을 진행시켜 그래프트율을 측정하였다. VBC-g-ETFE 필름은 FTIR 기기를 사용하여 성공적으로 그래프트 되었음을 확인하였다. 여러 용매에서 제조된 필름의 기계적 강도와 필름 단면에 그래프트된 VBC 고분자의 분포도를 측 정하여 용매의 영향을 평가하였다.

DEVELOPMENT OF PRACTICAL MEASUREMENT EQUIPMENT OF MEMBRANE STRESS FOR MEMBRANE STRUCTURES

One of the most important matters in keeping membrane structures in healthy condition is to maintain the proper tension distribution over the membrane. However, it is not easy to know the real stress level in the membrane quantitatively after completion of the structures. The authors proposed a new method that can measure membrane stresses in two different directions separately using sound waves –instead of measuring the membrane stresses directly. In this paper, various problems in the downsizing of measurement equipment and reduction of measurement time for practical application are examined, and clarified both theoretically and experimentally. In addition, not only the experimental tests using the membrane material of PTFE coated glass fabric as well as ETFE film with various combinations of the membrane stress, but also the actual measurement for existing suspension structure covered with ETFE film is carried out for practical use. The results verify the developed equipment can be used to continue measurement as a tool for scientifically and quantitatively determining the membrane stress which exists in the membrane material of the actual membrane structures.

Optical properties of polymeric materials for concentrator photovoltaic systems

As part of our research on materials for concentrator photovoltaics (CPV), we are evaluating the optical properties and solar radiation durability of a number of polymeric materials with potential in CPV applications. For optical materials in imaging or non-imaging optical systems, detailed knowledge of the wavelength-dependent complex index of refraction is important for system design and performance, yet optical properties for many polymeric systems are not available in the literature. Here we report the index of refraction, optical absorbance, haze, and Urbach edge analysis results of various polymers of interest for CPV systems. These values were derived from ellipsometry and from using a VUV-VASE and transmission based absorbance spectroscopy on thick film samples. Fluoropolymers such as poly(tetrafluoroethylene-co-hexafluoropropylene) (Teflon ® FEP), poly(tetrafluoroethylene-co-perfluoropropyl vinyl ether) (Teflon ® PFA) and poly(ethylene-co-tetrafluoroethylene) (Teflon ® ETFE Film) have desirable optical and physical properties for optical applications in CPV. Ethylene backbone polymers such as polyvinylbutyral (PVB) sheet (e.g., DuPont TM PV5200), and ethylene co-polymers such as poly(ethylene-co-vinyl acetate) (EVA) (e.g., DuPont TM Elvax ® PV1400), and poly(ethylene-co-methacrylic acid metal salt) ionomer sheet (e.g., DuPont TM PV5300) have applications as encapsulants in crystalline silicon (c-Si) and other flat plate PV applications. These materials are available with both a wide variety of polymer compositions and additive packages which affect their optical properties such as the UV absorption edge. Even materials such as DuPont’s Kapton ® polyimide films, which are used behind the PV cell for their electrically insulating properties, have optical requirements, and we have also characterized these materials. The detailed optical properties of these materials will be useful in the design of the geometrical optics of a CPV system and optimization of the system’s optical throughput. This information will also provide insights into the system’s optical absorption. This is important, for example in the UV, where this absorption can impact the radiation durability of the materials.