Transparent Composites Research Articles

Sustainable optically transparent composites based on epoxidized soy-bean oil (ESO) matrix and high contents of bacterial cellulose (BC)

Production of transparent composites from totally renewable resources with extraordinary potential for different applications can be made possible using cellulose. Composites of epoxidized soybean oil (ESO)/bacterial cellulose (BC) nanofibers have been prepared with high fiber content. Due to the nano-order scale network-like structure of BC nanofibers, composite films present high transparency even at high BC content. Transparency of films has been analyzed by UV–visible spectroscopy observing that only 15% of matrix transmittance is lost in the nanocomposites. ESO/BC composites show better mechanical properties with increasing BC content. Composites combine high stiffness and good ductility due to the incorporation of BC network structure in ESO matrix.

Transparent, Luminescent, Antibacterial and Patternable Film Forming Composites of Graphene Oxide/Reduced Graphene Oxide

Multifunctional graphene oxide/reduced graphene oxide (GO/RGO) composites were prepared through electrostatic interaction using biocompatible ingredients. Different functionalities were added to GO/RGO by anchoring materials such as native lactoferrin (NLf), NLf protected Au clusters (designated as Au@NLf), chitosan (Ch) and combinations thereof. Anchoring of Ch and NLf enhances the antibacterial property of RGO/GO. The addition of Ch to RGO/GO not only helped in forming stable dispersions but also helped in fabricating large (cm(2)) area films through a simple solvent evaporation technique. Functionalities such as photoluminescence were added to Ch-RGO/GO composites by anchoring Au@NLf on it. The composites thus formed showed stable luminescence in presence of various metal ions in the solid state. The composite showed reasonable stability against pH and temperature variations as well. The as-prepared films were transparent and the transparency could be modulated by controlling the concentration of RGO/GO in the composite. The antibacterial property and ability to form stable thin films may provide an opportunity to use such composites for medical and environmental remediation applications as well. Erasable patterns were fabricated on the film by stamping required patterns under compressive pressure. Luminescent patterns can be inscribed on the film and can be erased by simply wetting it. Such films with erasable information may be useful for security applications.

New technology of production of optically transparent polymer compositions containing capsulated nanosized aggregates of photoactive compounds

The article summarizes the results of the studies performed at the Institute of Chemical Physics, Russian Academy of Sciences, devoted to development of scientific foundations of adding nanosized particles of organic or inorganic photoactive compounds into polymers for production of new polymer nanocomposites of optical application. It is shown that luminescent europium complexes and photochromic indoline spirooxazines can be added to polymer matrices in the solubilized state at a threefold concentration compared to the process without Pluronics. The effect of an increase in the functional activity of solubilized luminescent europium complexes added to polymer compositions of various structures is discovered, which is related with a decrease in the size of aggregates of europium complexes at their solubilization by Pluronics. The solubilization by Pluronics exerts a sharp influence on the maximal content of indoline photochromes in the polymer matrix; the content of the colored form of photochrome in the 3D-crosslinked acryl matrix increases fourfold. This effect is related to both the decrease in the sizes of photochrome aggregates during solubilization and the plasticization of the polymer matrix by Pluronics.

Comparison study on transparent composites with different patterns of nanofiber reinforcement

In this work, PA-6 core and PMMA shell composite nanofiber mats together with pure PMMA and PA-6 nanofibrous membranes were obtained through electrospinning. Two kinds of transparent composites were fabricated by hot pressing multilayers of the composite nanofiber mats and of the interlaced pure PA-6 with PMMA nanofibrous membranes, respectively, under the same processing condition and with the same amount of PA-6 nanofiber content. Tensile properties and visible light transmittances of the two transparent composites were characterized. It has been found that both the tensile behavior and the visible light transmittance of the composites obtained from the composite nanofiber mats were better than the counterparts from the interlaced pure PA-6 and PMMA nanofibrous membranes. With a minor loss of less than 10 % in the transparency, a maximal increase of around 20 % in the tensile modulus and tensile strength has been recognized for a transparent composite from the composite nanofibers. Although less efficient, the tensile strengths of the composites from the interlaced nanofibrous membranes were all higher than that of a transparent panel processed from the pure PMMA nanofibers.

Effect of BN whiskers on dielectric and mechanical properties of BNw/Si3N4 composites

BN whisker reinforced Si3N4 (BNw/Si3N4) microwave transparent composites were prepared by gas pressure sintering at 1800°C in N2 atmosphere. The effects of BN whiskers on the dielectric and mechanical properties of BNw/Si3N4 composites were investigated. The results showed that the addition of BN whiskers could effectively improve the dielectric properties of BNw/Si3N4 composites while maintaining relatively good mechanical properties compared with the addition of BN particles. The dielectric constant, bending strength and fracture toughness of the composites with 15 vol.-%BN whiskers reached 3·8, 215 MPa and 4·31 MPa m1/2 respectively. The principal crystal phases of the composites were h-BN and β-Si3N4. The interlocked microstructure of BN whiskers and rod-like β-Si3N4 was responsible for the relatively good mechanical properties of BNw/Si3N4 composites.

Facile Synthesis of Transparent Mesostructured Composites and Corresponding Crack-free Mesoporous Carbon/Silica Monoliths

Transparent ordered mesostructured resin-silica composite monoliths with uniform rectangular shape which fully copies the inner-shape of vessels and size (5 × 3 × 0.3 cm3) are prepared via a facile approach of evaporation induced self-assembly (EISA) without adding any protecting agent by using triblock copolymer Pluronic F127 as a template. Ordered mesoporous carbon-silica composite monoliths can be obtained in a wide range of silica content (34–82 wt %) after calcination in N2. Monolithic shape can be maintained with shrinkage (∼20%) in sizes. Furthermore, each component of the composites can be easily removed after the simple post treatments. After etching silica, mesoporous carbon monoliths retain the same in shape and sizes, but show much larger pore volume (∼2.65 cm3/g) and higher surface area (∼1800 m2/g) than the carbon–silica composites. Besides, mesoporous silica monoliths with large pore size (∼14.6 nm) show an integral and uniform shape after air combustion. The obtained mesoporous carbon monoliths show high capacitance (186 F/g) and high cycling stability (8% capacitance loss after 1000 cycles), exhibiting an excellent potential in capacitor applications.

Synthesis of Poly(1,4-cyclohexanedimethyl-1,4-cyclohexanedicarboxylate) as the Matrix Resin for Transparent Composites

PCCD polymers were prepared by melt polycondensation of 1,4-cyclohexanedimethanol (CHDM) and 1,4-cyclohexanedicarboxylic acid (CHDA) in the presence of titanium tetrabutoxide (TBT) as catalyst in a successive two-step polymerization. In the first stage, the effect of esterification temperature and stirring rate on reaction degree were investigated. The impact of reaction temperature on reaction degree was more obvious than that of stirring rate. The optimal esterification temperature and optimal stirring rate was 220 °C and 150 r/min respectively. In the second stage, the reaction conditions such as molar ratios of CHDM to CHDA and polymerization temperature were controlled for the optimum results. Mn of PCCD polymers increased with increasing initial molar ratio of CHDM to CHDA firstly, got its maximum when initial molar ratio reached 1.004:1, and then decreased when initial molar ratio exceeded 1.004:1. The polymerization temperature of 275 °C can lead to high molecular weight PCCD polymers (Mn>30,000). Finally PCCD/glass composites were studied, and it was shown that the composites maintain high transmittance and low haze like those of pure PCCD but possess better mechanical and thermal properties.

Highly stretchable, transparent and scalable elastomers with tunable dielectric permittivity

We report a fast and simple process for the large scale fabrication of highly flexible, optically transparent carbon nanotube composites with massive dielectric permittivity. Various concentrations of pristine SWNTs were dispersed in hyperbranched polyurethane to prepare uniformly dispersed nanocomposite materials. Our solution-based method does not require modification on the carbon nanotubes, thus preserving the intrinsic electronic and high mechanical properties of the composites.

Preparation and characterization of optically transparent chitin nanofiber/(meth)acrylic resin composites

Optically transparent chitin nanofiber composites were fabricated with 11 different types of (meth)acrylic resins. Chitin nanofibers significantly increased the Young's moduli and the tensile strengths, and decreased the thermal expansion of all (meth)acrylic resins due to the reinforcement effect of chitin nanofibers having an extended crystal structure.

Air-coupled guided waves combined with thermography for monitoring fatigue in biaxially loaded composite tubes

Non-destructive methodologies for remote monitoring of fatigue induced by mechanical load in fibre reinforced plastics are presented. Hollow cylinders (glass fibre winding) were stepwise biaxially fatigued and measured in single-sided access configurations. Based on conversion of air-coupled ultrasound to guided waves, it is shown that accumulated fatigue damage is accompanied by decrease in phase velocity and increase in attenuation. The change in wave velocity caused by fatigue is shown to correlate closely with measurements of stiffness degradation of the composite. The attenuation of guided waves is affected by crack density which is visually traceable in the transparent composite. Monitoring of cyclic loading of the specimens by thermal imaging and a high-speed camera revealed that the initiation of final failure in the specimens coincides with spots of increased temperature. Air-coupled guided wave area scans allow for observing the development of these areas and other local damage in the composite.

Transparent and Conductive Graphene Oxide/Poly(ethylene glycol) diacrylate Coatings Obtained by Photopolymerization

AbstractWater‐dispersed graphene oxide sheets were used to prepare graphene/poly(ethylene glycol) diacrylate resin composites by photopolymerization. It was found that graphene sheets undergo excellent morphological distribution within the resin system, giving rise to transparent composites with unaltered thermal properties with respect to the neat resin, that are electrically conductive at loading ratios as low as 0.02 wt.‐% of graphene oxide. The proposed strategy based on photopolymerization provides an easy, energy‐saving and environmental friendly technique that can find a wide application in coating technology, mainly for electromagnetic shielding and antistatic coatings. magnified image

Transparent Infrared-Emitting CeF3:Yb−Er Polymer Nanocomposites for Optical Applications

Bright infrared-emitting nanocomposites of unmodified CeF(3):Yb-Er with polymethyl-methacrylate (PMMA) and polystyrene (PS), which offer a vast range of potential applications, which include optical amplifiers, waveguides, laser materials, and implantable medical devices, were developed. For the optical application of these nanocomposites, it is critical to obtain highly transparent composites to minimize absorption and scattering losses. Preparation of transparent composites typically requires powder processing approaches that include sophisticated particle size control, deagglomeration, and dispersion stabilization methods leading to an increase in process complexity and processing steps. This work seeks to prepare transparent composites with high solids loading (>5 vol%) by matching the refractive index of the inorganic particle with low cost polymers like PMMA and PS, so as to circumvent the use of any complex processing techniques or particle surface modification. PS nanocomposites were found to exhibit better transparency than the PMMA nanocomposites, especially at high solids loading (>/=10 vol%). It was found that the optical transparency of PMMA nanocomposites was more significantly affected by the increase in solids loading and inorganic particle size because of the larger refractive index mismatch of the PMMA nanocomposites compared to that of PS nanocomposites. Rayleigh scattering theory was used to provide a theoretical estimate of the scattering losses in these ceramic-polymer nanocomposites.

Deposition and Characterization of CdSe Nanoparticles in Polymeric Materials

Cadmium selenide nanoparticles coated with zinc sulphide CdSe/ZnS were prepared using dual source method. The composites were fabricated by stabilizing chemically synthesized semiconductor CdSe/ZnS into Laurylmethacrylate (LMA) and ethyleneglycol dimethacrylate (EGDMA) matrices in the presence of tri-n-octylphosphine (TOP). CdSe/ZnS were dispersed in toluene as a compatible medium for the polymerization and cross-linking of poly Laurylmethacrylate (LMA) networks. Transparent, fluorescent and flexible nano composites (NCs) materials resulted. The nano size particles and polymer composites were characterized by XRD, TG-DTA, IR, TEM and SEM.

Compositional dependence of the optical properties of bismuth doped lead-aluminum-germanate glass

We report the compositional dependence of absorption, emission, decay constant and quantum efficiency (QE) of GeO 2:Al 2O 3:PbO:Bi 2O 3 glass with the aim of finding the composition most suitable for a laser gain medium. As the Bi 2O 3 content was varied we observed a non-monotonic variation in absorption spectrum. The optimized composition was 87.4GeO 2:6Al 2O 3:6PbO:0.6Bi 2O 3 (% molar) which had a QE of 67% but low transparency. We report the dependence of QE and decay constant on melting conditions of this glass. Adding 10% ZnO improved the transparency, therefore the optimized and transparent composition was 74.4GeO 2:10ZnO:6Al 2O 3:6PbO:0.6Bi 2O 3, which had an emission full width at half maximum of 500 nm.

Displays from Transparent Films of Natural Nanofibers

AbstractOrganic light-emitting diodes bring a whole new level of image quality, power consumption, and very thin profiles to displays. In addition, with the appropriate choice of a flexible substrate, paper-like flexible displays that are lightweight, robust, and conformable can be produced. This will make it possible to roll or fold the displays for portability or incorporate them in clothing as wearable displays. Plastic substrates are considered prospective materials due to their inherent flexibility and optical qualities. However, one of the major drawbacks of plastics is the large thermal expansion. The thermal expansion of the substrate has to be compatible with those of the layers deposited on it, otherwise these layers will become strained and crack during the thermal cycling involved in the display manufacture. One of the proposed solutions to reduce the thermal expansion of plastics without appreciable loss in transparency is to reinforce them with nanofibers. These nanofibers are already available in enormous quantities in nature, in the form of cellulose, with the caveat that they have to be extracted properly. Here we present the methodologies required to obtain the cellulose nanofibers and to produce optically transparent composites for use in flexible displays.

One-step aqueous synthesis of blue-emitting glutathione-capped ZnSe1−xTexalloyed nanocrystals

This work demonstrates a facile one-step aqueous synthesis of blue-emitting glutathione-capped ZnSe(1-x)Te(x) nanocrystals possessing photoluminescence quantum efficiencies of up to 20%. The incorporation of the NCs into a water dispersed polymer was performed in order to enhance their stability and processability resulting in transparent blue-emitting inorganic-organic composites.

Tubular Clay Composites with High Strength and Transparency

Optically transparent composites containing nanotubular clay up to 65 wt%, prepared by a facile “one-pot” process, exhibited high mechanical strength and heat resistance. The attractive characteristics of the composites, in addition to their transparency, include use of low-cost and nontoxic raw materials, easy scaling-up, and possible petroleum independence. The properties of the composites were ascribed to the strong interfacial interactions and the excellent dispersion of nanotubular clay.

PC Nanofiber Reinforced PMMA Transparent Composites Incorporated with TiO<SUB>2</SUB> Nano-Particles

PC Nanofiber Reinforced PMMA Transparent Composites Incorporated with TiO<SUB>2</SUB> Nano-Particles

Structure and optical characteristics of the polymer-dye composites prepared via solvent crazing

Optical characteristics of the composites based on an amorphous polymer and a luminescent dye [poly(vinyl chloride)-Rhodamine 6G] prepared via solvent crazing are studied. After annealing at temperatures above glass transition temperature Tg, the samples show a dramatic increase in the intensity of absorption and luminescence bands of Rhodamine Y and a marked decrease in light scattering. The observed changes are due to the diffusion of dye molecules in the polymer matrix and healing of the porous structure of crazes. The above processes are independent and proceed simultaneously. As a result, transparent composites with a low level of light scattering and with a uniform distribution of dye molecules in the polymer matrix are formed. When the PVC-Rhodamine 6G samples are annealed at temperatures above Tg, dramatic changes in their spectral luminescent characteristics and color allow the above composites to be considered specific photochromic materials.

Morphology of PAI and PA-PDMS Composites Made by Sol-Gel Process

PA-PDMS (polyamide-polydimethylsiloxane) composites and PAI- PDMS (polyamidimide-polydimethylsiloxane) composites were prepared and investigated. The results of TEM (transmission electron microscopy) analysis showed that the difference in opaqueness was the result of different particle sizes in each composite. The PDMS particle size in the PA-PDMS composite was on a μ-scale, while that of the PAI-PDMS composite was roughly on a nm scale. Opaque composites are μ-composites while transparent composites are nano-composites. The results of the AFM (atomic force microscopy) analysis showed that PDMS particles larger than 2.5 μm were spread out on the surface of the PA matrix. An increase in the PDMS content of PA-PDMS composites resulted in decreased water absorption, from 11% to 6 %. The water absorption of PAI-PDMS composites also decreased from 6 % to 4 % as the PDMS content increased.