Acetate Matrix Research Articles

Solvodynamically Printed Silver Nanowire/Ethylene-co-vinyl Acetate Composite Films as Sensitive Piezoresistive Pressure Sensors

Pressure sensing is an important aspect of many processes and has a wide range of applications such as robotics and health monitoring. With the shift toward flexible and wearable technology, it is essential to develop high-performance flexible pressure sensors. In this study, we use solvodynamic printing to fabricate highly conductive piezoresistive composite films consisting of silver nanowires embedded in an ethylene-co-vinyl acetate matrix. The performance of the pressure sensor is tunable based on the composition and patterning of the film. The films can operate under a low input voltage (∼0.1 mV) with power consumption of <5 nW and show a low detection limit (12.9 ± 0.37 Pa), fast response time (11–22 ± 2.9 ms), and high sensitivity (67.3 ± 5.9 kPa–1) in the low-pressure regime, which is on par with commercially available pressure sensors. We further demonstrate the successful application of the film as a pulse-monitoring device.

Mineralization versus photoreduction of 4-nitrophenol under the influence of surface functionalized CeO2 nanoparticles, hosted by versatile cellulose supports

Multiple cellulose-derived platforms were designed for the immobilization of pristine/functionalized CeO2 nanoparticles with efficient photocatalytic activity under UV light. CeO2 nanoparticles were synthesized at two different pH values (pH = 6 and pH = 9) observing that those prepared at basic pH have better defined shapes and, by modifying their surface with silane moieties, the band gap values decreased from 3.27 eV to 2.89 eV. The synthesized CeO2 NPs were embedded in cellulose acetate matrix in various amounts and the achieved nanocomposites were tested as photocatalysts under UV irradiation in the photodegradation of hazardous pollutants, the optimal results being obtained at nanoparticle loading of 5 wt%. Also, the matrix type strongly influences the reaction pathway for 4–nitrophenol, from mineralization to photoreduction to 4-aminophenol. The cellulose acetate film containing functionalized CeO2 NPs was deacetylated under alkaline medium, to regenerate the cellulose structure, and subsequently oxidized using TEMPO mediated protocol. Experiments on 4–nitrophenol photodegradation, in the presence of oxidized cellulose bearing CeO2 NPs showed that this is completely converted to 4–aminophenol and proved the versatility of the proposed materials. Nanocomposites have good reusability results and the film containing silane-functionalized CeO2 NPs displayed encouraging efficiency as photocatalyst under visible light.

The effect of silica/zeolite-A nanocomposite on the polyvinyl acetate wood adhesive

The silica/zeolite-A nanocomposite additive was loaded at different values (1 - 4% wt) into polyvinyl acetate matrix to improve its wood adhesive properties. The silica nanoparticles were prepared by calcination method using rice husk as source material. X-ray diffraction analysis, FTIR spectroscopy, and SEM techniques were used for the characterization of the nanocomposite. The thermal stability and adhesion properties of modified polyvinyl acetate were evaluated by thermogravimetric analysis (TGA) method and measuring the shear strength of wood joints respectively. According to the results, the addition of silica/zeolite-A nanocomposite into polyvinyl acetate in dry condition and elevated temperatures was led to the enhanced shear strength of wood joints. However, in wet conditions, improvement of shear strength which was obtained by the addition of silica/zeolite-A nanocomposite was lower than that of the dry condition. Additionally, the thermal stability of polyvinyl acetate was affected by silica/zeolite-A nanocomposite. Polyvinyl acetate containing silica/zeolite-A nanocomposite additive showed better stability in water with respect to the pristine polyvinyl acetate.

Provisórios em prótese fixa: revisão integrativa da literatura e técnicas para confecção

INTRODUÇÃO: A prótese fixa provisória é uma parte importante do tratamento reabilitador, sendo uma fase intermediária necessária para a confecção das próteses definitivas. OBJETIVO: Apresentar materiais e suas propriedades; como também as técnicas para confecção de provisórios em Prótese Fixa, através de uma revisão de literatura integrativa. MATERIAL E MÉTODO: Busca dos artigos ocorreu na BVS e PubMed, publicados em português e inglês, entre 2000 a 2020. A estratégia de busca utilizada foi utilizando as palavras chave: (Denture, Partial, Temporary) AND (Polymers) AND (Denture, Partial, Fixed) AND ("Dental Prosthesis" OR "Flexural Strength" OR "Dental Polishing"). Foram incluídos estudos completos disponíveis; abordando o tema provisórios em Prótese Parcial Fixa sobre dente. Os critérios de exclusão foram estudos de provisórios em prótese sobre implante, revisões de literatura e relatos de caso. Os dados completos dos textos selecionados foram extraídos pelos revisores. Técnicas foram apresentadas quanto as etapas de confecção. RESULTADOS: Os estudos abordaram a aplicação de diferentes materiais e técnicas, além das pesquisas laboratoriais serem prevalentes. Observou-se uma heterogeneidade entre objetos de estudos e variáveis, destacando-se o uso de distintos polímeros, técnicas e adição do reforço. CONCLUSÃO: Há diversos materiais para a confecção de provisórios. As técnicas relatadas foram o uso do molde em silicone, matriz em acetato e CAD/CAM, e as mais comuns de serem executadas na clínica diária foram adaptação da faceta de estoque (sobre o preparo e dente tratado endodonticamente), resina adaptada ou bolinha e molde ou matriz em silicone.

Formation of CdS/ZnS nanoparticles in polymer matrix by SILAR method: Experiments and exploring its optical properties with DDA calculations

Composite nanostructures of Cadmium Sulfide (CdS) and Zinc sulfide (ZnS) were formed within the Cellulose Acetate matrix using successive ionic layer adsorption and reaction (SILAR) method, and their morphological and elemental characterizations were done employing field emission electron microscopy (FESEM) and energy dispersive X-ray (EDX) analyses. Experimental and theoretical investigations of the optical absorbance spectra of the prepared samples were performed by Uv-Visible spectroscopy and discrete dipole approximation (DDA) calculations respectively. The results show that when the absorbing part of the polymer matrix is composed of only CdS, increasing the number of SILAR cycles results in enlarging the absorbing part and a redshift in the wavelength of the maximum of the absorbance spectra. On the contrary, when the two materials CdS and ZnS have a contribution in the formation of the absorbing part, without paying attention to material distribution topology, and the absorbing part size, the abovementioned wavelength will remain unchanged.

Physical and chemical aspects of the interaction of chitosan and cellulose acetate with ions Ca2+ and K+ using DFT methods.

Motivated by the use of chitosan (Ch), and cellulose acetate (AC) as organic matrices in several therapeutic drugs, a theoretical study has been elaborated through the density functional theory method (DFT) to investigate the interaction mechanism between two essential ions for the human body Ca2+, K+ and two organic matrices chitosan (Ch), and cellulose acetate (AC). Many physical and chemical aspects have been carried out after the achievement of structural optimization. This involves structural parameters, molecular electrostatic potential (MEPs), interaction energy, reactivity indexes, frontier molecular orbitals (FMOs), quantum theory atoms in molecules (QTAIM) analysis, and non-covalent interaction (NCI) analysis. The results of FMOs, MEPs, and reactivity index studies have revealed that the site of interaction can be predicted. The calculation of electron interaction energies shows that those ions interact with the matrix of AC and Ch. Concretely, the Ca2+ ion interacted efficiently with the AC matrix. The structural analysis results show that the interaction of Ch and ions appear spontaneously (ΔG < 0) while the interaction of AC and ions (ΔG >0) requires more energy to occur. Finally, the QTAIM analysis data indicates that the interactions of AC-ions and Ch-ions are non-covalent presenting an electrostatic character.

Lamination of transparent conductive adhesives for tandem solar cell applications

A transparent conductive adhesive (TCA) interlayer for mechanically stacked multijunction solar cells provides adhesive strength and electrical connection between sub-cells when stacked. The fabrication of TCA sheets from an ethyl-vinyl acetate (EVA) matrix and silver coated compliant conductive microspheres, similar to industry-standard EVA encapsulant sheets, compatible with a standard lamination process was developed. Blade coating TCA sheets using 3D printed blades and testing of vertical conduction through the interlayer with a TCA conductivity jig allowed for reproducible measurements and low-cost fabrication. The supplemental information provides design files to enable other researchers to produce their own blades and testing jigs. We identified 0.5 mm as an optimal blade height for producing lab-scale TCA sheets and 120 °C at 3 psi for 10 min as the optimal vacuum lamination process to minimize resistance and possible damage to samples. For TCA sheets with coverages between 0.75% and 9%, the series resistance was approximately 0.2 Ω cm2 which should result in minimal losses for one-sun photovoltaic applications.

Investigation of cellulose acetate/gamma‐cyclodextrin MOF based mixed matrix membranes for CO2/CH4 gas separation

AbstractThis work is aimed to investigate the permeation characteristic of CA/γ‐CD‐metal organic framework (MOF) based mixed matrix membranes (MMM) for CO2/CH4 separation. The defect‐free CA/γ‐CD‐MOF MMMs with dense, isotropic morphology were fabricated using solution casting method. The fabricated membranes were characterized through Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), ultimate tensile testing, and contact angle measurements. The characterization techniques revealed the uniform dispersion of filler in cellulose acetate matrix and absence of the agglomerates or cracks in the synthesized membrane samples. Moreover, the CO2/CH4 separation performance of fabricated membrane was evaluated using single and mixed gas permeation tests. A general trend of decreasing permeability and selectivity, that is, 36.79–35 of both CO2 and CH4 was observed by increasing the filler weight percentage (0.2–1.0) and pressure (1–5 bar). However, the highest CO2/CH4 selectivity of 38.49 was achieved by CA/γ‐CD‐MOF 0.4wt% MMM. © 2021 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Mechanical properties of composite board based on coconut coir and terminalia catappa fruit fibers with Polyvinyl Acetate (PVAc) Matrix

The synthesis of composite board made from a mixture of coconut coir and Terminalia catappa fruit fibers using Polyvinyl Acetate (PVAc) matrix has been successfully carried out. The synthesis aims to determine the effect of a mixture of coconut coir and Terminalia catappa fruit fibers with PVAc matrix on the mechanical properties of the composite board. The samples were made with variations in the composition of the volume fraction of coir fiber and Terminalia catappa fruit fibers, namely (30:70), (40:60), (50:50), (60:40), and (70:30)%. The ratio of the volume fraction of the mixture of natural fibers and the PVAc) matrix made was (70:30)%. The sample production begins with taking the coconut coir and Terminalia catappa fruit, drying and cutting, then mixing the coconut coir and Terminalia catappa fruit fibers with a PVAc matrix, printing the composite with printing tools and drying. The finished sample was then mechanically tested using the UTM tool AnD, model R3010. The results showed that the value of the maximum tensile stress and the modulus of elasticity increased with the increase in the concentration of coir fibers used. The value added in length and strain decreased with the decrease in the concentration of coco fiber used. Overall, the composite sample has met the SNI 03-02105-2006 criteria where the maximum tensile stress value ranges from 8.21 MPa to 18.81 MPa and the modulus of elasticity ranges from 829.71 MPa to 1620.67 MPa.

Synthesis, characterization and bioactivity of thio-acetamide modified ZnO nanoparticles embedded in zinc acetate matrix

ZnO nanoparticles embedded in zinc acetate matrix were synthesized by chemical route. The effect of thio-acetamide concentration during its synthesis was probed by structural, morphological, optical and bioactivity studies. XRD characterization indicated the formation of dominant phase of zinc acetate along with the low intensity peak of wurtzite ZnO. Morphological transition from bulky-like feature to flower-like feature via flake-like feature, is evidenced with increasing thio-acetamide molar concentrations. The optical band gap of samples decreased from ∼3.29 to 3.24 eV whereas the emitted color shifted from near green to blue region with increasing of molar concentration of thio-acetamide from 0 to 30% in the sample. The nanoparticles exhibited antimicrobial activity against seven (7) common human pathogenic bacteria including drug resistant varieties K. pneumonaie and S. aureus. The nanoparticles formed pores in the biological model membranes made from egg-phosphatidyl choline. Our study reveals that the thio-acetamide modified ZnO nanoparticles embedded in zinc acetate matrix could be used as potential drug lead to fight drug resistance against K. pneumoniae and S. aureus.

Facile one−step preparation of acetylated cellulose nanocrystals and their reinforcing function in cellulose acetate film with improved interfacial compatibility

A facile one− step method to fabricate acetylated cellulose nanocrystals (ACNCs) was developed by using mixed sulfuric acid and acetic acid hydrolysis. It could be demonstrated that the esterification of surface hydroxyl groups took place simultaneously with hydrolysis of amorphous regions of cellulose, which was confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT − IR) and X − ray diffraction (XRD) measurement. The as − prepared ACNCs exhibited typical rod − like morphology with diameter and length of 12 − 18 and 191 − 234 nm, respectively. All − cellulose nanocomposite films were subsequently produced by introducing ACNCs into cellulose acetate (CA) matrix through solution casting technique. The mechanical performance of nanocomposites was significantly enhanced due to the uniform dispersion of ACNCs and favorable CA − ACNC interface. The results showed that the tensile strength, Young’s modulus and elongation at break of nanocomposite film were increased by 78%, 58% and 68%, respectively, with the introduction of 5% ACNCs. Moreover, the nanocomposite films could retain good optical transparency. These results indicated ACNCs have a great potential to be used as reinforcing filler in polymer matrices for extending their industrial applications.

Solar dye degradation using TiO2 nanosheet based nanocomposite floating photocatalyst

Floating photocatalysts are viable options for the degradation of pollutants using solar radiation. The presence of photocatalyst floating on top of the water body can enable better exposure to Sunlight and better air contact for photo-degradation. Direct use of powder photocatalyst in water bodies is impracticable. In the present work, TiO2 nanosheets were immobilized in a cellulose acetate matrix and provided support using Ethylene Vinyl Acetate to develop a floating photocatalyst. The performance of the floating photocatalyst for degrading pollutants under solar radiation was evaluated using Congo red dye as a model pollutant. The TiO2 nanosheet based floating photocatalyst showed good performance in the degradation of Congo red dye. X-ray diffraction and Field emission scanning electron microscopy were used to characterize the photocatalyst.

Improved mechanical, water vapor barrier and UV-shielding properties of cellulose acetate films with flower-like metal-organic framework nanoparticles

Flower-like metal-organic frameworks (Cu-MOF) nanoparticles are successfully synthesized and incorporated into cellulose acetate (CA) matrix to prepare CA-based functional nanocomposite films via a simple solution-casting method. The effect of the incorporation of flower-like Cu-MOF on the morphological, mechanical, thermal, surface wettability, water vapor barrier, cytotoxicity, photostability and UV-shielding properties of CA films is fully investigated. Results reveal that the flower-like Cu-MOF has good compatibility with CA, providing uniform and compact nanocomposite films. The as-prepared nanocomposite films show improved mechanical properties, surface hydrophobicity, water vapor barrier ability compared to neat CA film, and exhibit super UV-shielding capability through the entire UV regions meanwhile retaining a high visible transparency. Moreover, the high transparency and UV-shielding ability of the nanocomposite films can be still maintained even after continuous UV-light (365 nm) irradiation for 12 h. In addition, MTT cytotoxicity assays towards normal human liver cells (HL-7702) reveal high cell viability (over 80%) and good biocompatibility for the CA/Cu-MOF nanocomposite films. These results indicate that the CA/Cu-MOF nanocomposite films with obviously improved physical and functional performances hold significant potential for transparent packaging and UV-protection applications.

Analyzing the synthesis of various inorganic nanoparticles and their role in UV-shielding

In recent days we have been using many devices equipped with LED in one or other way, as display or light sources. These sources have large contribution of UV emission in their total emission of light. This adds the amount of UV radiations and its effect which we have already faced during the exposure of sun. To protect not only the human body, skin and eyesight, but also some essential surfaces of exteriors, plastic roof, we need some protecting film/materials that can absorb UV part from light radiation. Already aware of the harm that UV-A and UV-B rays from sun cause to the biotic components of the ecosystem, researchers and scientists have started seriously working in developing some films using polymer nanocomposites or nanomaterials which have improved tranceparancy, flexibility, durability features. Mainly concentrating on UV shielding applications, the article talks about various nanoparticles prominently used in the said purpose, namely CeO2, TiO2, ZnO, MnO2 and graphene oxide. Along with their respective synthesis methods, particle size, band gap, other experimental results have been highlighted. Green synthesis of ZnO nanoparticles with the assistance of fungus and bacteria also finds mention which is significant in reducing our dependence on chemicals. Hexagon shaped pristine and Al doped ZnO nanodisks (NDs) with exposed ± [0001] polar facets successfully synthesized with absolute ethanol: water system as dual solvent mixture show exceptionally good absorbance of 99% in UV range upto 390 nm. It also emphasizes upon the importance of the synergistic effect of the incorporated nanoparticles & the matrix material used and the conversion of cellulose acetate matrix into cellulose acetate naphthoate in order to enhance its service life in the commercial anti-UV applications.

Highly porous and thermally stable cellulose acetate to utilize hydrated glycerin

In this study, nano-pores in cellulose acetate matrix were generated by utilizing glycerin with water pressure without metal salts as additive. When cellulose acetate polymer membrane fabricated with glycerin as an additive was exposed to water pressure as external physical force, nano-pore generation depends on the pressure-strength exerted on the membrane. On the principle of the nano-pore generation, the chains became weakened in the portion of the cellulose acetate, in which glycerin was surrounded by abundant water molecules, resulting in plasticization capable of easily generating nano-pores with water pressure. We found that pore size and numbers of nano-pore could be easily controlled by adjusting the water pressure. Thus, we succeeded in preparing the porous cellulose acetate with high porosity of 78.3%.Generated pores in cellulose acetate polymers were confirmed by scanning electron microscopy (SEM) images and porosimeter. The coordinate interactions between cellulose acetate (CA) polymers and glycerin were investigated by FT-IR and TGA analysis.

Incorporation of polyethylene fillers in all-polymer high-thermal-conductivity composites

This work presents a lightweight electrically insulating composite material for high thermal conductivity: all polymer composites created by mixing ultra-high molecular weight polyethylene flakes into a matrix of low-density polyethylene or ethylene vinyl acetate. The ultra-high molecular weight polyethylene flakes have a reported thermal conductivity of 40 W m−1 K−1, and when 30 volume percent is compounded in an ethylene vinyl acetate matrix, the thermal conductivity is measured to be 2.5 W m−1 K−1 at 52 °C and the notched impact strength is 350 J/m. The temperature stability of the polyethylene flakes is investigated using polarized Raman spectrometry and thermal conductivity measurements, and it is discovered that flakes compounded at temperatures of 115 °C and above show a dramatic drop in thermal conductivity due to melting and reduced polymer chain alignment. This study highlights the possibility of using high-thermal-conductivity polymer fillers in bulk composites for near-room-temperature applications.

Graphene and MnO2 decorated graphene filled composites for electromagnetic shielding applications having excellent dielectric properties

Graphene nanoplatelets (GnP) and α-MnO2 decorated GnP were integrated into an ethylene vinyl acetate (EVA) matrix using the dual mixing method (solution followed by melt mixing). GnP was added in 1, 3, 5, 8, 10 and 15 phr loadings into an EVA matrix to obtain composites and evaluate their various properties suitable for mechanical and electrical applications. The graphene nanoplatelets were further decorated with α-MnO2 which was subsequently integrated into EVA at an 8 phr loading to form composites. It was observed in the GnP-EVA composites, that with an increasing GnP content, a substantial increase in the tensile strength (188%) over the neat polymer was observed at a 10 phr loading but reduced thereafter at a 15 phr loading. Dielectric permittivity of the composites were observed to increase with an increasing filler loading, the addition of α-MnO2 also having a beneficial effect. Conductivity as well as the electromagnetic interference shielding performance were improved with increasing GnP concentrations. A maximum 28 dB of shielding was observed in the 15 phr loaded GnP-EVA composite whereas the α-MnO2 decorated GnP-EVA composite showed a shielding efficiency of 22 dB at a concentration of 8 phr for a thickness of 2 mm with excellent thermal and mechanical properties. Overall, the composite material will find its application as a flexible EMI shielding material.

Immobilization of BiOBr into cellulose acetate matrix as hybrid film photocatalyst for facile and multicycle degradation of ciprofloxacin

A series of BiOBr/cellulose acetate (CA) composite films were prepared via solution casting method by dispersing BiOBr in the CA casting solution. Pristine BiOBr was initially synthesized via room-temperature solid state synthesis and was subsequently added into the CA casting solution in different concentrations. The phase, structural, surface, optical and thermal properties of the as-synthesized films were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR), photoluminescence (PL), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), thermogravimetric analysis (TGA) and the results confirmed the successful immobilization of BiOBr into CA film. The efficiency of the BCA composite films towards degradation of ciprofloxacin (CIP) antibiotic was tested under compact fluorescent light and was found to increase with increase in concentration of BiOBr. Moreover, the BCA composite film is easy to use, remained stable and exhibited high efficiency even after 10-cycle.

Development and Evaluation of the Chromatic Behavior of an Intelligent Packaging Material Based on Cellulose Acetate Incorporated with Polydiacetylene for an Efficient Packaging.

Global growth of the food industry and the demand for new products with natural characteristics, safe conditions and traceability have driven researches for the development of technologies such as intelligent packaging, capable to fulfil those needs. Polydiacetylene (PDA) is a synthetic material that has been highlighted in research field as a sensor substance, which can be used to produce intelligent packaging capable to detect chemical or biochemical changes in foods and in their environment due to PDA’s color transition from blue to red. This work focused on the development and optimization of an intelligent packaging constituted of a polymeric matrix of cellulose acetate-based incorporated with PDA as the substance sensor. Cellulose acetate films (3% wt.) were developed by a casting method, and the amounts of triethyl citrate plasticizer (TEC) (0–25% wt. of cellulose-acetate) and PDA (0–60 mg) were analyzed to optimize the conditions for the best color transitioning at this study range. The compound amounts incorporated into polymeric matrices were established according to Central Composite Designs (CCD). Three more design variables were analyzed, such as the polymerization time of PDA under UV light exposition (0–60 min), pH values (4–11) and temperature exposure on the film (0–100 °C), important factors on the behavior of PDA’s color changing. In this study, film thickness and film color coordinates were measured in order to study the homogeneity and the color transitioning of PDA films under different pH and temperature conditions, with the purpose of maximizing the color changes through the optimization of PDA and TEC concentrations into the cellulose acetate matrix and the polymerization degree trigged by UV light irradiation. The optimal film conditions were obtained by adding 50.48 g of PDA and 10% of TEC, polymerization time of 18 min under UV light, at 100 °C ± 2 °C of temperature exposure. The changes in pH alone did not statistically influence the color coordinates measured at the analyzed ratio; however, variations in pH associated with other factors had a significant effect on visual color changes, and observations were described. PDA films were optimized to maximize color change in order to obtain a cheap and simple technology to produce intelligent packaging capable to monitor food products along the distribution chain in real time, improving the food quality control and consumer safety.

Preparation and characterization of porous cellulose acetate with copper (II) nitrate additives for separator applications

We succeeded in generating nanopores in a cellulose acetate (CA) matrix under water pressure using copper nitrate (Cu(NO2)2·4H2O) as the additive. The nanopores were produced when the polymer matrix was subjected to isostatic water pressure adding copper(II) nitrate into the CA membrane. The polymer chains were weakened by the plasticization effect of copper(II) nitrate present in the CA membrane. We confirmed that the pore properties were readily changed by water pressure as external physical forces with additive content. The water flux of the CA composite (CA/Cu(NO2)2·4H2O) membrane improved with increasing water pressure and additive content. For the CA membrane without the additive, the water flux was not measured from 1 to 8 bar water pressure. In contrast, the water flow of the polymer film with the additive varied from 95.3 to 205.75 L/m2h, depending on the water pressure and additive content.