Cast Films Research Articles

Lubricated PDMS-bearing ladderlike polysilsesquioxane coating: Fabrication and factors governing its long-term ice-shedding performance

Reacting an epoxy-bearing ladder-like polysilsesquioxane (LASQ) with mono-carboxy-terminated poly(dimethyl siloxane) (PDMS-COOH) yields LASQ-PDMS, a blend of LASQ and a graft (g) copolymer LASQ-g-PDMS. Photolyzing a cast film of LASQ-PDMS containing a cationic ring-opening polymerization initiator produces a robust and wear-resistant coating. Such a coating presents a liquid-like surface PDMS brush layer that imparts anti-smudge and ice-shedding properties. These properties are significantly enhanced via the application of a silicone oil (SO) as a lubricant. Investigated in this study are the effects of changing the molecular weight and mass fraction of PDMS as well as the molecular weight of a SO or composition of a SO mixture on properties of the lubricated LASQ-PDMS coating. These properties include the coating’s hardness, water repellence, wear resistance, SO retainability, initial ice adhesion strength (τ), variation of τ with the number of abrasions made by steel wool on a coating, and variation of τ with the number of icing/de-icing cycles. This systematic study establishes the exceptional wear resistance of the LASQ-PDMS coatings and reveals SO retainability as the primary factor governing the long-term ice-shedding performance of the coatings.

Stimuli-Responsive Properties of a Zinc(II) Salen-Type Schiff-Base Complex and Vapochromic Detection of Volatile Organic Compounds.

This contribution reports, through a combined thermogravimetric analysis, differential scanning calorimetry, UV-vis, powder X-ray diffraction, and Rietveld refinement analysis, on the stimuli-responsive chromic properties of a substituted Zn(salmal) Schiff-base Lewis acidic complex with unique and distinct thermo- and vapochromic characteristics. The solid complex obtained in air or by evaporation of the solvent from their THF solutions shows a marked thermochromism associated with a phase transition, unusually triggered by the reversible desorption/adsorption of one lattice water molecule. In contrast, the anhydrous solid, achieved from THF solutions of the complex by evaporation of the solvent under anhydrous conditions, behaves very differently as it does not show any absorption of water or thermochromism and exhibits varied vapochromic properties. Detection of volatile organic compounds having Lewis basicity is demonstrated by using the anhydrous solid or the related cast films on glass or paper substrates. In both cases, a marked vapochromism is observed upon exposure to vapors of various volatile species and involves well-defined optical absorptions and naked-eye color changes, also allowing the discrimination of primary aliphatic amines. Vapochromic behavior with the formation of stable, stoichiometric adducts is also demonstrated for both the solid obtained in air and the anhydrous solid or for the related cast films after exposure to vapors of pyridine.

Preliminary evaluation of properties and performance of natural rubber (NR) latex band for microplastic capturing in seawater

Microplastic particles are emerging water-laden waste that cause a worrying concern towards the environment and humans health. Due to its small size and geometry, and uncertain surface properties, the microplastic waste capturing method in water is still evolving. To date, a number of findings report on the emergence of microplastic surface charging, especially when exposed to water environment. In this study, the natural rubber (NR) latex band was utilized to capture the microplastic waste via a surface capturing mechanism. The NR band was produced using a film casting and curing methods. The surface charging mechanism on the NR band was introduced via the usage of high amount of ZDEC accelerator and, periodic stretching and relaxation procedures. In this work, ZDEC was used as an accelerator for the rubber formulation, and surface charge booster for the NR band. The surface charge of the NR band generates electrostatic interaction with the microplastic waste in water. The polypropylene (PP) microplastic was captured via the surface attraction mechanism using the manufactured NR band. Based on FTIR analysis, the presence of PP microplastic can be quantified on the contaminated NR band surface. The NR band shows the improvement in tensile and tear properties and crosslink density, mainly due to high amount of ZDEC used. At ZDEC loading of 20 phr, the NR band recorded the highest surface potential value, and this is owing to the formation of Zn2+ complex ions on its surface. XRF analysis indicates that the increment of Zn content in the NR band with increasing ZDEC content, that suggests the formation of Zn2+ complex ions.

Tunable Dielectric Spectroscopy of PVDF Thin Films Crossbred with TiO2 Nanoparticles for the Storage Devices

AbstractPolyvinylidenefluoride (PVDF) is a semi‐crystalline ferroelectric polymer with a wide range of interesting properties and shows potentiality in a variety of technological applications. Flexible thin films of PVDF nanocomposites (NCs) have attracted many researchers due to their tunable electronic properties. This paper reports the synthesis, characterization, and dielectric studies of PVDF‐TiO2 NC thin films. The synthesized films are self‐supporting thin and the average thickness of the thin films is 60 µm measured using a Digital thickness gauge of resolution 0.01 mm. TiO2 nanoparticles are prepared using the combustion method. Commercially available PVDF granules are used to develop PVDF‐TiO2 NC thin films using the film casting technique. The structural study of the prepared thin films is carried out using XRD that confirms the retention of the β‐phase of PVDF. The functional group and bonding nature have been studied using FTIR Spectroscopy. The thermal stability of the NC thin films is studied using TGA. The variation of dielectric constant (DC), dielectric loss (DL), AC conductivity, and dissipation factor of the medium of pristine PVDF and PVDF‐TiO2 NC thin films are studied in the frequency range of 10 Hz to 8 MHz at ambient temperature. The dielectric constant of PVDF‐TiO2 NC thin films increases up to 8 wt% and anomaly for 10 wt% of TiO2 fillers in the PVDF matrix at a lower frequency and found to decrease with increasing frequency. The dielectric loss of NC thin films is high at a lower frequency and decreases with an increase in the frequency that is in good agreement with the Maxwell–Wagner type of interfacial polarization. At lower frequencies, the dielectric constant of PVDF‐TiO2 NC increases with the increase in filler content. AC conductivity shows a sharp increase at higher frequencies whereas the dissipation factor of the polymer NCs remains unaltered with respect to frequency by maintaining the trend. This suggests that PVDF‐TiO2 NC is potential material for energy storage devices.

Characterization of Chitosan Films Cast from Different Solvents: FTIR, Surface and Mechanical Investigations

Chitosan (CS), a modified carbohydrate polymer derived from chitin by deacetylation, has shown various applications in a variety of industries, including food, cosmetics and packaging. In this work, CS films prepared from CS dissolved in three selected solvents i.e. formic acid (FA), acetic acid (AC) and propionic acid (PA) were investigated by employing scanning electron microscopy (SEM), atomic force microscopy (AFM), FTIR spectral analysis and mechanical tests (MT). SEM measurements showed relatively smooth and homogeneous surfaces for all films confirmed by AFM. The FTIR spectra of all CS films showed similar spectra with a little shift of some bands towards lower or higher wave numbers. In addition, CS film cast from AC recorded the highest elongation at break but the lowest tensile strength among the three types of films used.

Preparation and characterization of pH-sensitive intelligent packaging films based on cassava starch/polyvinyl alcohol matrices containing Aronia melanocarpa anthocyanins

Intelligent packaging films have sparked interest due to their capacity to indicate food freshness. In this study, a pH-sensitive packaging film was developed using the cast film process, with cassava starch and polyvinyl alcohol (PVA) as substrates. Aronia melanocarpa anthocyanins (AMA) were incorporated as visual indicators of pH changes. The study assessed the impact of the cassava starch/PVA ratio and AMA content on the films' physical, structural, and pH-sensitive properties. It evaluated their potential for monitoring milk freshness. The results revealed that films with a starch/PVA ratio 3/7 achieved optimal tensile strength (TS) and elongation at break (EAB). The incorporation of AMA into the films enhanced their UV barrier properties. Notably, the compatibility between starch and PVA was improved when the film contained 1 g of AMA per hectogram (hg) of the total mass of starch and PVA. Specifically, the enhanced compatibility was evident through differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) analysis. Furthermore, the films demonstrated notable color changes within a pH range of 2–11, indicating their potential for monitoring milk freshness. These findings suggested that the films containing AMA hold great promise for applications in intelligent packaging within the food industry.

Synthesis and Characterization of Cellulose Microfibril-Reinforced Polyvinyl Alcohol Biodegradable Composites.

The pursuit of an environmentally sustainable manufacturing process requires the substitution of less damaging and recyclable solutions for harmful reagents. This study aims to assess the effectiveness of using cellulose microfibrils synthesized via different hydrolysis reactions as reinforcing agents in polyvinyl alcohol (PVA) at varying concentrations. The investigation explores the morphology, thermal properties, and chemical behavior of the cellulose particles. The cellulose microfibrils (CMFs) produced using citric acid exhibited the highest yield and aspect ratio. Notably, particles from organic acids demonstrated greater thermal stability, with oxalic acid-derived particles displaying the maximum thermal degradation temperature. Subsequently, cast films of PVA reinforced with the cellulose microfibrils underwent comprehensive analyses, including Fourier transfer infrared (FTIR) spectroscopy, thermal degradation temperature (Td), differential scanning calorimetry (DSC), and tensile strength tests. The thermal behavior of cast films experienced notable changes with the addition of cellulose particles, evidenced by increased melting and crystallinity temperatures, along with a rise in the degree of crystallinity. The incorporation of cellulose particles led to a substantial improvement in mechanical properties. Films containing CMF displayed higher Young's modulus, and the sample incorporating 5% CMF derived from citric acid exhibited the most significant increase in modulus.

Ziziphora clinopodioides extract-loaded chitosan/polyvinylpyrrolidone casting films for potential applications in wound dressings

Chitosan/polyvinylpyrrolidone composite films containing hydroalcoholic Ziziphora clinopodioides extract were developed and evaluated for their potential use as wound dressings. The physical and chemical properties of the films were extensively explored, including swelling capacity, mechanical properties, antimicrobial activity, and microstructural characteristics. The results showed that the addition of Ziziphora extract significantly increased the swelling capacity of the films by 561.24% to 1175% (p < 0.05). While tensile strength and Young’s modulus were enhanced, elongation at the breaking point decreased with increasing volume percentages of Ziziphora extract. Variance analysis indicated no statistically significant effect on the tensile properties of the films with varying Ziziphora extract content (p < 0.05). Furthermore, films incorporated with Ziziphora extract demonstrated antimicrobial properties. Scanning electron microscopy (SEM) analysis revealed that samples lacking Ziziphora extract had a smooth surface, while those containing the extract displayed a rough texture that may potentially accelerate the wound healing process.

Morphology of impact polypropylene copolymer extruded cast film revealed by confocal Raman imaging.

An impact polypropylene copolymer (IPC), composed of polypropylene (PP) and ethylene-propylene copolymer (EPC), was synthesized through two-stage in-reactor polymerization. A systematic investigation of the crystalline structure, thermal behavior, morphology, and tensile properties of the IPC extruded cast film was conducted. Specifically, the morphology of EPC was obtained by confocal Raman imaging by depicting the spatial distribution of the Raman band located at 1064 cm-1. The EPC phase exhibits fibrous morphology with the long axis aligning along the machine direction (MD). A three-dimensional (3D) heterogeneous structure of the IPC cast film obtained by confocal Raman imaging confirms that the fibrous EPC phase is dispersed in a 3D framework of the PP matrix. The mesomorphic phase in the as-prepared cast film transforms to a stable α-form crystal after annealing at 130 °C, which improves the yield strength but decreases the elongation of the cast film. The WAXD and SAXS results indicate that there is no obvious orientation of the crystallites. Thus, the anisotropy of tensile properties in the MD and transverse directions is closely related to the anisotropic phase morphology at the micrometer scale. The results reveal that the mechanical performances of IPC films are determined by the crystalline structure of the PP matrix and the morphology.

Mechanically robust ultrathin nanofibrous films by using microfluidic-based continuous printing.

Ultrathin nanofibrous films with unique properties, such as controlled thickness, structures, and excellent mechanical robustness, play a vital role in flexible wearable devices, electronic skin, and rechargeable batteries. However, nanofibrous films are always facing limitations in their mechanical properties, even though they are strong when used as textiles, mainly owing to their structural shortcomings by using conventional fabrication methods. Herein, we present the fabrication of free-standing ultrathin nanofibrous films with good mechanical properties by using a microfluidic-based continuous printing strategy. Owing to the precisely controllable microfluidic flow in the micrometre-scale, the resulting aramid nanofibre (ANF) films can reach thicknesses as low as 140 ± 25 nm. Specifically, the tensile strength of such ultrathin ANF films is recorded at an impressive value of 667 ± 40 MPa, representing a 120% improvement compared to the films prepared by using casting method. Such excellent mechanical robustness comes from the double-sided protonation, which shows a symmetrically dense structure compared to the asymmetric structure of cast films. Furthermore, we demonstrate the continuous fabrication of thin regenerated cellulose nanofiber (RCNF) and cellulose diacetate (CDA) films using the microfluidic-based printing strategy. Both microfluidic-based films show significant enhancements in strength, with a 42% increase for RCNF and a 94% increase for CDA compared to their cast films. We envision that this microfluidic-based continuous printing strategy provides a promising pathway for the development of advanced ultrathin nanofibrous films towards practical applications.

Synthesis and Structural Characterization of Four Different Concentrations of Ant Nest (Myrmecodia pendens) Collagen Membranes with Potential for Medical Applications.

The purpose of this study was to synthesize and structurally characterize four ant nest membranes in four different concentrations and determine the best concentration that could potentially be used as an alternative material for the production of new collagen barrier membranes. Membranes were created by mixing ant nest extracts at various concentrations of 0.5%, 1%, 1.5%, and 2%, as well as collagen, chitosan, and Polyvinyl Alcohol (PVA) using a film casting. A Universal Testing Machine (UTM) was used to evaluate mechanical properties including elastic modulus, tensile strength, maximum elongation, elongation at break, and maximum force. Water absorption was performed, FTIR was used for functional group identification, and morphology was examined using SEM. Additionally, EDS was used to identify the composition and distribution of elements in membranes. Statistical analysis was conducted using ANOVA (analysis of variance) and post hoc testing with a significance level of p <0.01 for quantitative data. The results showed that the mechanical properties produced the following mean (standard deviation): elastic modulus 0.87 Mpa (0.11), tensile strength 16.32 N/mm2 (2.46), maximum elongation 4.96% (1.72), elongation at break 5.23% (1.87), and maximum force 22.50 N (5.06). The average water absorption capacity of all four membranes had a p-value <0.01. FTIR spectrum showed various peaks corresponding to functional groups, while SEM results indicated a homogeneous mixture. EDS analysis confirmed that the addition of ant plant extract at 0.5%, 1%, and 1.5% resulted in the presence of elements C, O, and Ca. Meanwhile, membranes prepared with 2% concentration had a different composition, namely C, O, Ca, and Na. Increasing the concentration of ant nest affects the values of the membrane's mechanical properties parameters, including the elastic modulus (0.87 Mpa), tensile strength (16.32 N/mm2), maximum elongation (4.96%), elongation at break (5.23%), and maximum force (22.50 N). The average membrane absorption of water (p value <0.01) was also affected. SEM images showed homogeneous mixing, and membrane EDS results consisted of C, O, and Ca composition. However, there was no effect on FTIR functional groups. The anthill membrane with a 1% concentration has the potential to serve as an alternative membrane in guided tissue regeneration.

Designing thermoreversible gels for extended release of mosquito repellent.

Mosquito-borne diseases are responsible for 700 000 deaths annually. Current outdoor protective strategies primarily focus on direct skin application of commercial repellents (i.e., aerosol sprays or topical lotions) which are typically limited to efficacy times of ≤10 hours due to rapid evaporation and dermal absorption. Consequently, frequent reapplication for continuous protection can increase associated health hazards and cause noncompliance. This study utilizes Hansen solubility parameter modeling to design physical gels composed of insect-repelling N,N-diethyl-meta-toluamide (DEET) and modacrylic copolymer poly(acrylonitrile-co-vinyl chloride) (P(AN-VC)). The P(AN-VC)/DEET composites exhibit tunable and reversible sol-gel transition temperatures that can meet the thermomechanical stability demands of the intended application and permit facile transition to commercial melt processing techniques such as injection molding, filament spinning, or film casting. P(AN-VC)/DEET gel films demonstrate mosquito repellency for more than half a year-performing longer than any other known material to date-due to the high reservoir of repellent and its desorption hindrance from the polymer matrix. Therefore, P(AN-VC)/DEET gels hold significant potential for extended protection against mosquitos and other biting arthropods.

Towards All-Extruded Custom-Shape Batteries

The rapid growth of flexible electronics for wearable devices, on-skin or environmental sensors, and flexible displays have resulted in intensive research in the field of free form-factor energy-storage systems. Since batteries must withstand bending, folding, or stretching while maintaining their electrochemical performance, the design and processing of battery components, must be reconsidered. Moreover, there is a clear tendency to shift battery technology to clean and cost-effective dry methods with no toxic solvents. Dry fabrication methods are environmentally friendly, involve lower energy consumption, shorter time and are cost-effective. Hot-pressing and melting-extrusion strategies are appropriate for the fabrication of flexible, solid-polymer electrolytes and electrodes with high contents of active materials and high mass loading.Here we present the progress towards the simple, one-step extrusion of a solid-state battery with a multi-shell and layered architecture. Such structures fundamentally minimize the ionic pathway for Li+. As in the conventional battery, high ionic conductivity of extruded electrolyte and compatibility with electrode materials, are the essential properties for enabling high performance of the battery. The electrolytes are composed of LiTFSI, polyethylene oxide (PEO), which is a known lithium-ion conductor, and thermoplastic recyclable and biodegradable polymer- polyurethane (TPU) - for enhanced mechanical properties and high-temperature durability. The extruded electrolytes of different PEO-to-TPU ratios and salt content were characterized by means of ESEM imaging, mass spectroscopy, differential-scanning calorimetry (DSC), electrochemical-impedance spectroscopy (EIS) and solid-state nuclear magnetic resonance (NMR) diffusion measurements. The structure and electrochemical properties of extruded electrolytes were compared with cast films. It was found that TPU, having in its structure, both soft segments from polyol regions and hard segments from isocyanate not only improves the mechanical properties of neat PEO-based polymer electrolyte, but also forms complexes with lithium salt and serves as a conducting medium. Bulk conductivity vs. temperature dependencies obey Arrhenius behavior. The highest conductivity values varying from 0.3 to 1mS/cm over a temperature range from RT to 90ºC were achieved for the extruded 1:15 (Li:EO) solid polymer electrolyte. The NMR tests show that lithium self-diffusion coefficients in extruded PE with alumina filler are close to that in cast PE, but the anion diffusion coefficients (accessible through 19F NMR) are lower in extruded filaments, indicating a correspondingly higher Li+ transference number induced by the extrusion. Lithium cells with extruded LFP cathode and solid extruded polymer electrolyte demonstrated 40 reversible cycles with close to 96% coulombic efficiency. The electrochemical performance of half-cells composed of extruded LFP-based cathode and extruded TPU-MWCNT-based current collector will be presented.

STRUCTURE DEVELOPMENT AND PROPERTIES OF PLASTICIZED PVA-STARCH-PADDY STRAW COMPOSITES

Paddy straw is often burnt in the fields or disposed of in ways that cause extensive environmental pollution. The present study focused on using paddy straw in bio-compostable composites fabricated with polyvinyl alcohol (PVA) and thermoplastic starch blends as a matrix. Locally available paddy straw was chopped, cleaned and treated with 15% NaOH solution for four hours. The alkali treatment produced changes in the crystal structure and surface morphology of the paddy straw. Then, it was dispersed in blends of PVA and starch solutions containing polyethylene glycol (PEG200) as plasticizer. The PEG200 acted as both plasticizer and compatibilizer, as evidenced by the single glass transition peak and the lower melting point of the film cast from these blends. These composite films had higher thermal stability, increased tensile strength, but also flexibility. These properties were associated with structure development with strong hydrogen bonding interaction between the paddy straw and PVA-starch blends, which was supported by results of characterization studies.

Multiple shearing-induced high alignment in polyethylene/graphene films for enhancing thermal conductivity and solar-thermal conversion performance

The simultaneous achievement of ordered alignment for fillers and polymer matrix is highly desired in polymer-based thermally conductive composites, but it is still extremely challenging. Herein, we put forward a layer-by-layer scraping (LbLS) method to simultaneously arrange ultra-high molecular weight polyethylene (UHPE) chains and graphene nanoplates (GNP) into a highly oriented structure. When UHPE/GNP gel suffering the strong shearing effect during LbLS process, the inner UHPE chains and GNP were dragged and orderly arranged along shearing direction, and these oriented structures were retained after rapidly drying by distillation. After layer-by-layer stacking, nacre-like UHPE/GNP films with tightly layered structure were obtained. By adjusting the scraping gap from 200 to 50 μm, the oriented structure can be effectively reinforced with the Herman orientation factors f increasing from 0.83 to 0.88 for GNP and 0.75 to 0.82 for UHPE chains. The highly ordered structure can form a tight and oriented thermal conduction network with low interfacial thermal resistance in plane. The LbLS composite film thus significantly enhanced the in-plane thermal conductivity up to 28.88 W/mK, compared with traditional solution casting film (9.63 W/mK). Moreover, the highly oriented structure can significantly increase the solar-thermal conversion performance (58.1 °C@100 mW/cm2) by improving its light absorption ability comparing to that of solution casting film. Besides, the mechanical strength and toughness that depend on the filler and chain alignment were effectively increased by the oriented structure.

Magnetic Chitosan Bionanocomposite Films as a Versatile Platform for Biomedical Hyperthermia.

Responsive magnetic nanomaterials offer significant advantages for innovative therapies, for instance, in cancer treatments that exploit on-demand delivery on alternating magnetic field (AMF) stimulus. In this work, biocompatible magnetic bionanocomposite films are fabricated from chitosan by film casting with incorporation of magnetite nanoparticles (MNPs) produced by facile one pot synthesis. The influence of synthesis conditions and MNP concentration on the films' heating efficiency and heat dissipation are evaluated through spatio-temporal mapping of the surface temperature changes by video-thermography. The cast films have a thickness below 100µm, and upon exposure to AMF (663kHz, 12.8 kA m-1), induce exceptionally strong heating, reaching a maximum temperature increase of 82 °C within 270 s irradiation. Further, it is demonstrated that the films can serve as substrates that supply heat for multiple hyperthermia scenarios, including: i) non-contact automated heating of cell culture medium, ii) heating of gelatine-based hydrogels of different shapes, and iii) killing of cancerous melanoma cells. The films are versatile components for non-contact stimulus with translational potential in multiple biomedical applications.

Potential application of hydroxypropyl methylcellulose/shellac embedded with graphene oxide/TiO2-Nps as natural packaging film

Graphene oxide (GO), TiO2-NPs, HPMC, and shellac are environmentally green polymers and nanocomposites. This work aimed to create biodegradable composite films made of HPMC/shellac, HPMC/shellac-GO, and HPMC/shellac-GO/TiO2-NPs by film casting. TiO2-HPMC/shellac-GO matrix's dispersibility and mixing ability were characterized and observed using FTIR and XRD. XRD analysis shows that the crystallinity decreased within the composites due to breaking H-bonding. Compared to HPMC/shellac, TGA/DTG demonstrated the composite films' superior thermal stability. TiO2 (0.08–0.16 %) was cast into a composite film comprising HPMC, shellac, and GO. The homogeneity of TiO2 distribution in the composite film was shown using a SEM, which was also used to display the morphology of nanocomposite films. Nanocomposite films' thickness, air permeability, tensile strength, Young's modulus, and burst strength were examined. The results demonstrated that natural films prepared by a combination of shellac/GO with HPMC enhanced the fabricating of films' properties, the tensile strength increased by 231 % (from 16 to 53 MPa) in HPMC and HPSG2 (HPMC 1.9 g/shellac 0.25 g/GO 0.125 g in 100 mL) respectively, whereas the contact angle did not change. And after addition of TiO2-NPs, there were high enhancements in HPMC films' properties, such tensile strength increased by 212 % (from 16 to 50 MPa), burst strength increased by 20.96 % (3.1 to 3.75 Kg/cm2), and the contact angle by 60.86 % (48 to 74°) in HPMC and HPSGT2 respectively. Compared to HPMC films, films exhibited the highest levels of antibacterial activity against E. coli, B. mycoides, and C. albicans. So, the composite films from HPMC/shellac/GO/TiO2-NPs are promising potential packaging materials.

Short-side-chain perfluorosulfonic acid incorporated with functionalized silane-based hybrid membrane for the application of energy devices

A unique functionalized organosilane (FOSi) is synthesized and prepared as a hybrid organic-inorganic composite membrane (OICM) using short-side-chain perfluorosulfonic acid (SSC-PFSA) at a large scale for vanadium redox flow battery (VRFB). The OICM solution is fabricated by using 75 wt % of SSC-PFSA and 25 wt % of FOSi and cast with the help of Roll to Roll (R2R) film casting equipment. The OICM's proton conductivity and performance are comparable to the Nafion membrane, owing to additional hydrophilic fields in the hybrid membrane. The OICM possesses proton conductivity of 0.13 S/cm and an ion exchange capacity of 1.44 meq/g, even though the water uptake has been lowered than the PFSA owing to better dispersion of FOSi. OICM has a low vanadium permeability (1.52 × 10−6 cm2/min) and remarkable selectivity, which is a significant benefit. Consequently, over 45th cycles, the OICM performs comparably to Nafion in energy efficiency combined with coulombic and voltage efficiency. The unit cell-test with OICM shows a normalized coulombic efficiency due to low permeability than PFSA and high voltage efficiency due to high proton conductivity. Hence OICM divulges a promising path to developing an alternative membrane for energy devices.

Investigation on the rheological behavior of PA6 film during biaxial stretching

In this work, the rheological behavior of polyamide 6 (PA6) film during biaxial stretching was investigated. Firstly, the cast film was subjected to different ratios of biaxial stretching, and the stress calculation expression of biaxial stretching was derived. Then the generalized Maxwell model was employed to fit the stress-time curves in the heat setting stage. It was found that the elastic-plastic deformation during biaxial stretching influenced the stress rebound or relaxation in the heat setting. Finally, the relaxation spectrum and activation energy spectrum were calculated according to the fitting curves. It was found that the stress relaxation process of PA6 film was divided into multiple stages, but the stress rebound process was relatively simple. According to the activation energy spectrum, we speculated that stress relaxation was a process of releasing energy, and stress rebound was a process of absorbing energy. With the increased stretching ratio, the peaks on the activation energy spectrum became sharper and the intensity increased. Indicating that more energy was released or absorbed under the larger stretching ratio. The obtained results would provide theoretical guidance for further understanding the biaxial stretching deformation mechanism of polymer films.

NiFe2O4/biochar decorated porous polymer membranes for the flow-through photo-Fenton degradation of tetracycline

Herein, coffee grounds derived biochar was used as support for the fabrication of NiFe2O4/biochar composite particles. The composites achieved up to 10x higher turnover frequencies (TOF) in the photo-Fenton degradation of tetracycline (20 mg/L) in batch compared to the pure NiFe2O4 particles. This could be correlated to a decreased agglomeration, lower band gap energy and electronic interaction with the biochar. The hydrophobic support further enabled the incorporation of the NiFe2O4/biochar powders into porous polyethersulfone (PES) membranes via film casting cum phase separation. The resulting about 150 µm thick porous flow-through membrane reactors achieved high degrees of conversion (95–99 %) at a flux of 100 L/m2h in the continuous photo-Fenton degradation of tetracycline (20 mg/L) in water. We could further show that the TOF values are 5-20x times higher in flow-through the catalytic membranes compared to the NiFe2O4/biochar catalyst particles used in batch mode. We also demonstrated that our photocatalytic membranes can remove low concentrations of tetracycline (2 and 0.2 mg/L) toward values below the detection limit of the used mass spectrometry analysis. Monitoring the leaching of Ni and Fe from one membrane over 28 h of flow-through revealed that Ni predominantly leaches from the incorporated NiFe2O4/biochar, which, however, did not lead to any loss of the catalytic activity. Moreover, we found that the residence time in the membrane has a direct influence on the tetracycline degradation pathways and the resulting product profile, which represents a novel approach for tuning Fenton-like reactions towards specific products.