Acetate Films Research Articles

Highly Transparent, Self-Reinforced, and Hydrophobic Cellulose Acetate Films Fabricated Based on Thermal Stretching and Surface Engineering

Imparting cellulose acetate with surface hydrophobicity and self-cleaning function without sacrificing its high transparency and mechanical robustness is a great challenge. In this work, we report a highly transparent, self-reinforced, and hydrophobic cellulose diacetate (CDA) film, prepared by the combination of non-solvent-induced phase separation, uniaxial thermal stretching, and slippery liquid injection (LI). Results indicate that the surface-modified CDA films have hydrophobicity, with the water contact angle (WCA) increasing from ∼58.2 to 105–109°. Meanwhile, by adjusting the draw ratio, the sliding of liquid on the film surface and the WCA hysteresis are effectively improved, especially the sliding angle of CDA-LI-1.7-200 film decreases from 30.5° (for the unmodified CDA film) to 9.4°. Notably, uniaxial stretching provides enhanced mechanical strength for this antifouling CDA film, with up to 60.2% increase in tensile strength (from 37.2 to 59.6 MPa). Meanwhile, it is noted that the modified CDA film also has excellent transparency (≥92%), even slightly higher than that of the unmodified CDA film (∼91.5%). In addition, the surface-modified CDA films show excellent anti-scratching performance and maintain good liquid repellency even after several cycles of severe scratching. The work would provide guidance for the facile preparation of high-performance and multifunctional CDA films.

Preparation of Cellulose Acetate Nanocomposite Films Based on TiO2-ZnO Nanoparticles Modification as Food Packaging Applications

To develop bio-packaging materials, nanocomposite films of cellulose acetate reinforced with titanium dioxide and zinc oxide nanoparticles were prepared, by the casting method at different weight ratios of ZnO nanoparticles (1.5, 2, and 2.5) wt% and a constant weight ratio of 2 wt% TiO2. ZnO and TiO2 nanoparticles were tested using scanning electron microscopy (SEM). The mechanical properties (tensile strength and elongation) were improved at a fixed level of Cellulose Acetate+ 2% TiO2+1.5wt% ZnO loading. Beyond that level of loading, they decreased. The tensile strength was decreased due to some degrees of agglomeration of filler particles above a critical content. Fourier-Transform Infrared Spectroscopy (FTIR) was conducted to reveal the microstructures and chemical composition of as-prepared composite films. The wettability of the films was also determined by the sessile drop method. An increase in contact angle was also observed by the addition of ZnO content from 70.6° to 77.1° compared to pure Cellulose Acetate, which indicated a value of 61.3°. Antibacterial activity against Escherichia coli and Staphylococcus aureus was enhanced after incorporation of ZnO-TiO2 compared with pure CA. The enhanced wettability and antibacterial activity of the prepared films suggest that they could be used for packaging applications.

Performance Enhancement of Crystal Silicon Solar Cell by a CsPbBr3–Cs4PbBr6 Perovskite Quantum Dot @ZnO/Ethylene Vinyl Acetate Copolymer Downshifting Composite Film

Crystal silicon solar cells being the most successful photovoltaic devices have prevailed in the energy market for decades. To further improve the device performance, photon management is necessary. Herein, a CsPbBr3–Cs4PbBr6 perovskite quantum dot@ZnO/ethylene vinyl acetate copolymer downshifting composite film is coated on the silicon solar cell. This downshifting composite film helps to convert high‐energy (UV‐blue) photons to relatively low‐energy photons with a wavelength at about 500 nm, which possess higher sensitivity in silicon solar cells. The effects of tetra‐n‐heptylammonium bromide and Zn(C2H5)2 on composition, optical and luminescence properties of perovskite quantum dots are thoroughly investigated, and a clean quantum dot solution with strong luminescent intensity can be obtained. The perovskite quantum dot@ZnO/ethylene vinyl acetate composite film absolutely improves the efficiency of silicon solar cells by 1.18%. The value is much higher than pure ethylene vinyl acetate (0.42%) and composite film without ZnO (0.57%). Moreover, ZnO inclusion can inhibit Cs and Pb leakage and maintain the device working stability, which is helpful for their commercial application in the future. This study further reveals that the enhancement lies in carrier relaxation energy loss reduction. Herein, a low‐cost downshifting composite film with excellent environmental stability for silicon solar cells applications is proposed.

Fluorescent indolo[2,3-b]quinoxalin-2-yl(phenyl)methanone dyes: photophysical, AIE activity, electrochemical, and theoretical studies

Herein, we have synthesized four indolo[2,3-b]quinoxalin-2-yl)(phenyl)methanone derivatives by cyclocondensation. The photophysical studies of dyes in various solvents and neat solid film exhibit typical electronic spectra with inbuilt intramolecular charge transfer (ICT) (λmax: 397–490 nm) confirming donor–acceptor architecture. Herein, dyes fluoresce in the blue-orange region (λEmax: 435–614) on excitation at their ICT maxima in toluene, ethyl acetate, chloroform, DMSO, and neat solid film. Two dyes, which exhibit good emission intensity in all mediums, were studied for aggregation-induced emission (AIE) effect. Electrochemical studies indicate the dyes possess relatively low lying LUMO (− 3.65 to − 3.98 eV) comparable to reported n-type/electron-transporting materials. The HOMO and LUMO energy levels were evaluated by DFT and TD-DFT calculations. TGA analysis shows the dyes exhibit good thermal stability. The characteristic optoelectronic properties and thermal stability signify these dyes are potential candidates for their application in optoelectronics.Graphical abstract

Single‐step post‐production treatment of lead acetate precursor‐based perovskite using alkylamine salts for reduced grain‐boundary related film defects

AbstractPowered by the worldwide efforts of research groups experienced in dye‐sensitized, and thin‐film solar cells, perovskite solar cells (PSCs) reached a power conversion efficiency of 25.7% within 10 years. However, the presence of defects and trap density within the active layer's grain boundaries commonly operates as non‐radiative recombination centers. Hence, intensive efforts have been reported to passivate the inevitable bulk and interface defects of the active layer using additives or post‐treatment processing to enhance the efficiency and stability of PSCs. Herein, a facile post‐treatment strategy based on wet processing methylammonium lead triiodide, MAPbI3 (prepared from lead acetate and methylammonium iodide precursors) films with organic amine salts (FABr and FAI) is demonstrated. As a result, high‐quality films of mixed perovskites (FAxMA1‐xPbI3‐xBrx and FAxMA1‐xPbI3) were obtained. The surface treatment has efficiently passivate the defects in the host film, suppressing the non‐radiative carrier recombination. Compared to the control device, the increased open‐circuit voltage (from 0.5 V to 1 V) and fill factor (FF) values of the optimized device based on FAxMA1‐xPbI3 showed a PCE of 16.13%. And our findings revealed that post‐treatment is possible on wet perovskite film aged for a few minutes prior to its post‐treatment, which saved the energy used for pre‐annealing.

Improvement of stability for cellulose polymer by calcium oxide for application to porous materials

In this study, calcium oxide (CaO) was used as an additive to form pores in a cellulose acetate (CA) and at the same time improve the thermal stability of the cellulose acetate. When the CA/CaO membrane was exposed to water pressure, the CA matrix area plasticized by the CaO particles became weakened and water channels were formed. In addition, the high melting point of CaO and its bonding with the carbonyl group of CA caused a crosslinking effect. We succeeded in manufacturing a porous separator with a high porosity of 73.1% and a high flux value of 92.25 L/m2 h at 8 bar. Furthermore, TGA measurements revealed an increase of thermal stability by 50 °C. The pores generated in the cellulose acetate film were confirmed using a SEM and mercury porosimeter. Thermal stability and interactions in materials were measured using TGA and FT-IR. By improving the thermal stability of inexpensive and eco-friendly cellulose acetate, the potential for commercialization of battery separators was proposed.

Regulation of orientation birefringence for cellulose acetate film: The role of crystallization and orientation

Cellulose acetate (CA) based films are widely used in liquid crystal displays due to their outstanding transparency, and a certain orientation birefringence of CA films is required when they are used as retardation films. The regulation of orientation birefringence is usually from the perspective of stretch-induced orientation, while the effects of crystallization behaviors of CA films remain obscure. In this study, the roles of crystallization and orientation on the orientation birefringence of CA films were elucidated. For cellulose diacetate films, the orientation birefringence is dominated by the orientation degree. In comparison, apart from the orientation degree, crystallinity is another key variable to regulate the orientation birefringence of cellulose triacetate and plasticized cellulose triacetate films, originating from the birefringence heterogeneity of the crystalline and amorphous phases. These results provide valuable guidelines for the production of CA-based optical films with excellent optical performance.

Improvement of the functional properties of cellulose acetate film by incorporating with glycerol and n-propanol

Cellulose acetate (CA) was used for the preparation of food packaging film. Glycerol and n-propanol were introduced, as plasticizer and transparent agent, respectively for evaluating the possible changes of the film functional properties on tensile strength and transparency. The transmittance, haze value, tensile strength and flexibility were acquired by using optical and mechanical analyses, respectively. The presence of glycerol improved the functional properties of films by increasing their extensibility, flexibility and elasticity; however transparency of the films deteriorated with the inclusion of plasticizer. Therefore, the addition of n-propanol as transparent agent into the films enhanced the transparency. Moreover, morphological changes and gas barrier property were confirmed by scanning electron microscopy and water vapor transmission rate analyses. The results suggest that CA films incorporated with plasticizer and transparent agent have good functional properties in isolating water vapor, mechanical performance and optical properties, demonstrating that the optimal film has a potential in the application for food packaging. High strength transparent cellulose acetate film (CAF) was prepared with glycerol as plasticizer and n-propanol as transparent agent. The addition of glycerol and n-propanol has a significant influence on film mechanical performance, optical properties, water vapor barrier property and physical behavior, such as pore structure.

Exposure to cellulose acetate films incorporated with garlic essential oil does not lead to homologous resistance in Listeria innocua ATCC 33090

Essential oils (EOs) have been considered potential green additives for active food packaging. However, sub-lethal concentrations of EOs may lead to bacterial resistance, which is a concern. In this sense, the effects of 1% (GEO1) and 10% (GEO10) of garlic EO in cellulose acetate-based films regarding homologous resistance in Listeria innocua were investigated after incubation at 37 °C/24 h and 7 °C/10 d. The films were also characterized and tested on sliced mozzarella cheese as interfold packaging for 8-days storage at 7 °C. The EO did not alter the mechanical properties of the films nor their thermal degradation profile. However, GEO10 was less permeable to water vapor than GEO1. When tested against L. innocua, the incubation at 7 °C enhanced the films’ antimicrobial effect: log reductions of 4.3 and 5.7 were obtained for GEO1 and GEO10, respectively. Moreover, 86.3% of L. innocua cells were injured at sub-lethal level when exposed to GEO10. Despite this, no occurrence of homologous resistance was found. When the active films were tested on cheese against the natural microbiota, they resulted in slices of mozzarella with fewer contaminants, however the reduction was not significant. Nevertheless, we considered this an important finding to the food industry since this work suggested that GEO is a safe active compound from the point of view of homologous resistance to be used against Listeria.

Characterization and chemical modification of pullulan produced from a submerged culture of Aureobasidium pullulans ATCC 15233

In this paper, the pullulan produced by A. pullulans ATCC 15233 was characterized and chemically modified. The pullulan derivative was synthesized with an acetylation reaction with a degree of substitution (DS) of 2.90. Its structural elucidation was performed using infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The results showed signs of α (1–4) and α (1–6) glycosidic bonds, typical of pullulan. The molecular weight (MW) of pullulan was 93.47 kDa. The thermal analysis conducted indicated increased thermal stability (Td) and glass transition temperature (Tg) due to acetylation. Homogeneous morphologies of the samples under analysis were obtained using scanning electron microscopy (SEM). The mechanical properties of the pullulan film exhibited tensile strength (TS) values of 1.70 ± 0.48 MPa and an elongation at break (% E) of 11.89%. Likewise, the pullulan acetate film recorded a TS of 1.23 ± 0.09 MPa and a % E of 1.25%. The results suggest that the physicochemical properties of biosynthesized pullulan and pullulan derivatives can be considered in the development of biomaterials.

Antibacterial and degradable properties of β-cyclodextrin-TiO2 cellulose acetate and polylactic acid bionanocomposites for food packaging

Polylactic acid (PLA) and cellulose acetate (CA) as biodegradable polymers are being highly exploited in the development of innovative materials across several industrial sectors. PLA and CA composite films with TiO2 nanoparticles (NPs) and β-cyclodextrin grafted TiO2 NPs were prepared. Thermo- and photo-degradation studies were performed on PLA and CA films and noticed that higher amount of TiO2 induce greater color variations, structure modifications and weight losses. It has been observed 9.3 % and 5.1 % maximum weight loss for 5 % TiO2 CA and PLA matrices, respectively. βCD-modified TiO2 NPs increased the photo-degradation of the plain polymers to a lesser extent than TiO2 NPs. Benzoic acid (BA) and sorbic acid (SA) were incorporated to βCD-TiO2 NPs and the antibacterial activity of PLA and CA composite films was studied by inactivation of Escherichia coli and Staphylococcus aureus. CA film filled with 5 % TiO2 NPs presented the highest antibacterial activity and achieved 71 % inhibition of E. coli and 88 % inhibition of S. aureus. CA composite films showed potential to be used as antimicrobial food packaging.

Quantification of methods used in field metallography using the example of quality assurance measures for a circular economy for high-alloy steels

Abstract This study aims to develop a method for on-site metallography, enabling the characterization of carbide banding in cold-work steels via cellulose acetate film replication. It will be demonstrated that for this purpose, it is sufficient to grind the sample surface using P1500 mesh SiC abrasive paper and etch it with V2A etchant or nitric acid for 7 minutes. By sample preparation and etching, the matrix of the parent material is sufficiently removed for the carbides to leave a “negative” impression on the film. This negative replica can then be studied under reflected light microscope, enabling the characterization of carbide banding.

High-Throughput Direct Writing of Metallic Micro- and Nano-Structures by Focused Ga+ Beam Irradiation of Palladium Acetate Films.

Metallic nanopatterns are ubiquitous in applications that exploit the electrical conduction at the nanoscale, including interconnects, electrical nanocontacts, and small gaps between metallic pads. These metallic nanopatterns can be designed to show additional physical properties (optical transparency, plasmonic effects, ferromagnetism, superconductivity, heat evacuation, etc.). For these reasons, an intense search for novel lithography methods using uncomplicated processes represents a key on-going issue in the achievement of metallic nanopatterns with high resolution and high throughput. In this contribution, we introduce a simple methodology for the efficient decomposition of Pd3(OAc)6 spin-coated thin films by means of a focused Ga+ beam, which results in metallic-enriched Pd nanostructures. Remarkably, the usage of a charge dose as low as 30 μC/cm2 is sufficient to fabricate structures with a metallic Pd content above 50% (at.) exhibiting low electrical resistivity (70 μΩ·cm). Binary-collision-approximation simulations provide theoretical support to this experimental finding. Such notable behavior is used to provide three proof-of-concept applications: (i) creation of electrical contacts to nanowires, (ii) fabrication of small (40 nm) gaps between large metallic contact pads, and (iii) fabrication of large-area metallic meshes. The impact across several fields of the direct decomposition of spin-coated organometallic films by focused ion beams is discussed.

Tailoring the Selective Permeation Properties of Asymmetric Cellulose Acetate/Silica Hybrid Membranes and Characterisation of Water Dynamics in Hydrated Membranes by Deuterium Nuclear Magnetic Resonance.

In this work, the water order and dynamics in hydrated films of flat asymmetric cellulose acetate (CA)/silica, CA/SiO2, and hybrid membranes, covering a wide range of nanofiltration (NF) and ultrafiltration (UF) permeation properties, were characterised by deuterium nuclear magnetic resonance (DNMR) relaxation. The range of NF/UF characteristics was attained by subjecting three CA/SiO2 membranes, prepared from casting solutions with different acetone/formamide ratios to drying post-treatments of solvent exchange and conditioning with surfactant mixtures. Post-treated and pristine CA/SiO2 membranes were characterised in terms of hydraulic permeability, selective permeation properties and molecular weight cut-off. These results were correlated with the DNMR relaxation findings. It was found that the post-treatment by solvent exchange caused membrane shrinkage that led to very different permeation characteristics and a significant enhancement of the DNMR relaxation observables. In contrast, conditioning with surfactant solutions exhibited a weaker effect over those properties. Scanning electron microscopy (SEM) images were obtained for the membranes post-treated with solvent exchange to confirm their asymmetric nature. This work provides an essential indication that DNMR relaxometry is a reliable tool to characterise the asymmetric porous structures of the NF/UF CA/SiO2 hybrid membranes.

Imparting Cellulose Acetate Films with Hydrophobicity, High Transparency, and Self-Cleaning Function by Constructing a Slippery Liquid-Infused Porous Surface

The high hydrophilicity and brittleness of cellulose acetate (CA) limit its application as a barrier and as a moisture-proofing, waterproofing, and self-cleaning agent. Imparting CA films with hydrophobicity, high transparency, and good mechanical properties simultaneously is of great significance but remains a challenge. In this work, a surface modification method combing nonsolvent induced phase separation (NIPS) and liquid injection is proposed for the treatment of cellulose diacetate (CDA). It is discovered that by utilizing acetone/ethanol as the solvent system for NIPS, and carefully tuning CDA concentration, CDA films with controlled micro/nanoporous surface structures are obtained. Further injecting liquid paraffin into the porous surfaces, high transparent CDA films are achieved, with optical transmittance up to 91.8% (very close to 93% for the pure CDA film) in the visible range. Besides, the surface treatment also significantly changes the surface wettability, leading to hydrophobic CDA films (water contact angles increase from 58.2 to 106.6°) with good water-repelling and self-cleaning functions. Moreover, these surface-modified CDA films also have comparable or even more superior mechanical properties over the pure CDA film, with the tensile strength and the elongation at break as high as 45.2 MPa and 61.2%, respectively. This work would provide significant guidance for the large-scale preparation of CA-based films with special surface wettability, high transparency, and good mechanical properties.

The study of the particle size effect on the physical properties of TiO2/cellulose acetate composite films

Abstract The cast method was used to synthesize cellulose acetate (CA)/titanium oxide (TiO2) composites by varying TiO2 particle sizes at different weight ratios of 1, 1.5, 2, 2.5, and 3 wt%. The relationship between structural diversity and performance was explored. Microstructures and chemical composition of as-prepared composite films were revealed using field-emission scanning electron microscopy and Fourier-transform infrared spectroscopy. The tensile strength increased from 46.8 MPa for pure CA to 54.7 MPa for the CA-1% micro-TiO2 composite and 81.7 MPa for the CA-2% nano-TiO2 composite, according to the mechanical properties. The tensile strength decreased due to some degrees of agglomeration of filler particles above a critical content. UV-vis transmittance spectra showed that pure CA was almost transparent, CA-micro-TiO2 films were less transparent than pure CA, and CA-nano-TiO2 films could efficiently block the light. XRD diffraction for the synthesized membranes was performed. The patterns of micro-TiO2 and nano-TiO2 were shown as 2θ = 25° for the anatase phase and 2θ = 18.5 for the pure CA film, respectively. The hydrophilicity of films was also measured using the sessile drop technique. The contact angle value for the pure CA was 61.3°. As the amount of TiO2 added to the films increased, the contact angles of the CA-micro TiO2 and CA-nano TiO2 films reduced from 53.2° to 29° and from 51.5° to 27°, respectively. The produced films’ improved wettability indicated that these films could be employed as filters.

Development and characterization of biodegradable ultraviolet protective and antibacterial polylactic acid-cellulose acetate film modified by phenyl salicylate

The polylactic acid composite films were successfully fabricated via the technique of solvent casting using cellulose acetate (20%, wt) as the reinforcing material and phenyl salicylate as the ultraviolet (UV) absorbent and antibacterial agent. Polylactic acid-cellulose acetate-phenyl salicylate composite films displayed complete absorption effect at the region of UV-C (280–100 nm) and UV-B (315–280 nm), and more than 95% UV absorption effect at the region of UV-A (400–315 nm). These results indicate that the UV shielding performance of the composite films could be significantly improve by addition of phenyl salicylate. Moreover, the addition of 20% phenyl salicylate could improve the steam resistance, mechanical properties and thermal stability of the films, and the composite films had also better antibacterial activity against Escherichia coli. The composite films could reduce the decay rate of fresh lilies and extend their storage time. The degradation characteristics of the films were explored in the natural environment and the laboratory level, which provided application prospect for the development of degradable food packaging materials with anti-ultraviolet and anti-bacteria effect.

Towards skin-acetone monitors with selective sensitivity: Dynamics of PANI-CA films.

Most research aimed at measuring biomarkers on the skin is only concerned with sensing chemicals in sweat using electrical signals, but these methods are not truly non-invasive nor non-intrusive because they require substantial amounts of sweat to get a reading. This project aims to create a truly non-invasive wearable sensor that continuously detects the gaseous acetone (a biomarker related to metabolic disorders) that ambiently comes out of the skin. Composite films of polyaniline and cellulose acetate, exhibiting chemo-mechanical actuation upon exposure to gaseous acetone, were tested in the headspaces above multiple solutions containing acetone, ethanol, and water to gauge response sensitivity, selectivity, and repeatability. The bending of the films in response to exposures to these environments was tracked by an automatic video processing code, which was found to out-perform an off-the-shelf deep neural network-based tracker. Using principal component analysis, we showed that the film bending is low dimensional with over 90% of the shape changes being captured with just two parameters. We constructed forward models to predict shape changes from the known exposure history and found that a linear model can explain 40% of the observed variance in film tip angle changes. We constructed inverse models, going from third order fits of shape changes to acetone concentrations where about 45% of the acetone variation and about 30% of ethanol variation are captured by linear models, and non-linear models did not perform substantially better. This suggests there is sufficient sensitivity and inherent selectivity of the films. These models, however, provide evidence for substantial hysteretic or long-time-scale responses of the PANI films, seemingly due to the presence of water. Further experiments will allow more accurate discrimination of unknown exposure environments. Nevertheless, the sensor will operate with high selectivity in low sweat body locations, like behind the ear or on the nails.

High-performance cellulose acetate-based gas barrier films via tailoring reduced graphene oxide nanosheets

Improving the gas molecule barrier performance and structural stability of bio-plastic films dramatically contribute to packaging and protective fields. Herein, we proposed a novel nanocomposite film consisting of cellulose acetate (CA)/polyethyleneimine (PEI)/reduced graphene oxide (rGO)-NiCoFeOx) with high gas barrier property by applying “molecular glue” and “nano-patching” strategies. Systematical investigations demonstrated that the CA/rGO interfacial interaction was effectively enhanced due to the “molecular glue” role of PEI chains via physical/chemical bonds and the defective regions in rGO plane were nano-patched through hydrophilic interactions between edged oxygen-containing functional groups and ultrafine NiCoFeOx nanoparticles (~3 nm). As a result, the oxygen and moisture transmission rates of the prepared CA/PEI/rGO-NPs hybrid film were significantly reduced to 0.31 cm3 ∗ μm/(m2 ∗ d ∗ kPa) and 314.23 g/m2 ∗ 24 h, respectively, which were 99.60% and 54.69% lower than pristine CA films. Meanwhile, the tensile strength of hybrid film was increased from 25.90 MPa to 40.67 MPa. More importantly, the designed nanocomposite film possesses excellent structural stability without obvious GO layer shedding and hydrophobicity attenuation after persistent bending at least 100 times. The exceptional robust and high gas barrier film displays great promising application in food, agriculture, pharmaceuticals and electronic instruments packaging industry.

Jambolão extract and potassium sorbate as antimicrobial components in active packaging

This study aimed to use the raw extract of jambolão (Syzygium cumini L.) and potassium sorbate as antimicrobial components in cellulose acetate films and evaluate their potential for application as active packaging forsugar-free banana preserve. The films were prepared using the casting method and evaluated for thickness and inhibition potential. The efficiency of the films as active packaging, in situ, was evaluated through the enumeration of aerobic mesophiles and mold and yeast over 36 days of storage of banana preserves.