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This study presents a novel type of wet electrode material for electrophysiological monitoring based on a conductive aerogel film. The electrode material incorporates cellulose nanocrystal and fiber as a biocompatible polymer and multi-walled carbon nanotube as a conductive filler. The fabricated electrode is fully characterized to explore the chemical, mechanical, electrical, and water absorption properties. The wet aerogel film presents suitable mechanical flexibility owing to the use of fiber enabling it to be conformal to curved surfaces like human body. The water absorption percentage of the fabricated aerogel film is extremely high (∼500%) due to the porosity of the film and hydrophilicity of the base polymer allowing it for effective wet electrode applications. The film is air dryable with a fast (∼10 min) and facile wetting process granting the electrode application for long-term, multiple use, and remote monitoring of patients. The electrical impedance range of the fabricated aerogel electrodes is relatively low (20 Ω/cm2-370 Ω/cm2) which is within the range of use for various electrophysiological monitoring purposes such as electrocardiography (ECG) and electroencephalography (EEG). Overall, the presented study introduces a novel wet electrode based on porous and electrically conductive aerogel film to be used for various biomedical applications. [ABSTRACT FROM AUTHOR]

Computed tomography imaging phantom devices have proven to be beneficial in improving computed tomography diagnostic techniques. Though commercial phantoms are available with tissue mimicking properties, there is a lack of low-density tissue specificity and variety. This study proposes a method for the fabrication of various low-density tissue mimicking computed tomography imaging phantoms. By illustrating the fabrication technique, material properties can be shown to be controlled and assessed against characteristic computed tomography imaging properties, most particularly, the computed tomography number in Hounsfield Units. A batch cellular foaming technique was utilized on thermoplastic polyurethane with ranging heated water bath foaming times from 0.5 to 10 min to fabricate polymeric computed tomography phantoms of controlled foam material properties. Computed tomography number values were experimentally measured. Additionally, separate experimental measurements were made on the foam characteristic properties of fabricated thermoplastic polyurethane foams. A relative decreasing trend was exhibited between the foam characteristic properties of cell density, average cell size, and material density to computed tomography number. [ABSTRACT FROM AUTHOR]

Multifunctional shape memory composites composed of shape memory polymers and shape memory alloys exhibit superior shape memory properties; therefore, it is of great interest to researchers to model their thermo-mechanical behavior numerically. Although a number of constitutive models of shape memory alloys and shape memory polymers have been developed, very few models have been developed for shape memory composites and validated with experimental data. In this study, we first review separately constitutive models of shape memory alloys and shape memory polymers developed in previous studies. Both models were validated with thermo-mechanical tests conducted on a shape memory alloy fiber and shape memory polymer, respectively. A constitutive model for the shape memory composite was then developed utilizing the homogenization scheme. Shape memory composites containing 0.5% or 1% of the shape memory alloy fiber volume content embedded in the shape memory polymer matrix were fabricated. Thermo-mechanical tests were carried out on these shape memory composites to validate the proposed constitutive model. The experimental results showed that the proposed shape memory composite model was able to predict the general trend of the thermo-mechanical behavior of the shape memory composites. [ABSTRACT FROM AUTHOR]

Polymeric composites have the potential to replace current electronic packaging and improve thermal management of electronics to open the way for further size shrinkage. Such composites need to provide high thermal conductivity and high electrical resistivity while possessing suitable mechanical properties. This paper reports the study of thermal behavior of arranged and random network of hexagonal boron nitride (hBN) in composite with different polymers. Thermal barrier factors and possible solutions to reduce the effect of these factors are thoroughly investigated. Thermal behavior of hBN filler network in composite with different polymers as well as the possibility of using green (bio-based) polymers as the matrix have been studied. Fully bio-based, partially bio-based and petroleum based composites are compared to investigate the effect of different polymer matrices on thermal properties of composites. Designed high thermally conductive and electrically insulative composites are expected to possess unique properties. This includes being lightweight, injection moldable, low coefficients of thermal expansion, eco-friendly, and with proper service temperature and mechanical properties. Such composites will result in more compact, lighter and cheaper electronics with higher performance, by avoiding the use of electrical fans, heat sinks and other methods of heat dissipation. [ABSTRACT FROM AUTHOR]

Multifunctional polymer matrix composites (PMCs) exhibiting increased thermal and electrical conductivity can be achieved by adding conductive carbon-based fillers in the polymer matrix. Emerging markets for thermally and electrically conductive PMCs include heat management devices in electronics, light emitting diodes, and/or photovoltaics cells as well as bipolar plates in fuel cells. In this study, the effects of microsized and nanosized carbon fillers [e.g., pitch-based carbon fibers (CF), multiwalled carbon nanotubes (MWNT), and graphene nanoplatelets (GNPs)] on the multifunctional properties of polyphenylene sulfide (PPS) matrix composites were investigated. Among the three carbon-based fillers, experimental results revealed that GNPs were the most effective fillers to promote the PMC's effective thermal conductivity ( keff). The highest keff of 1.94 W/m K was attained by adding 30.0 wt% (i.e., 22.4 vol%) of GNPs in the PPS matrix. The nano-sized MWNTs and GNPs had lower percolation threshold than the micron sized CFs to suppress the composite's electrical impedance. However, the coefficient of thermal expansion and the compressive elastic modulus of the composites were only slightly improved with the filler addition. The different levels of improvement in the composite's multifunctional properties can be related to the filler geometry, filler size, and the composite's phase morphology. POLYM. ENG. SCI., 53:2398-2406, 2013. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The article discusses a study on the fabrication of solid and porous polylactide (PLA)-multiwall carbon nanotube (MWNT) composites. It describes the morphology and thermal, rheological and electrical properties of the PLA-MWNT composites prepared with MWNT concentrations of 0. 0.5, 1, 2 and 5 weight percent. The study found that increasing MWNT content increased the thermal stability and crystallization kinetic of PLA.

The article provides information on a study which investigated the effect of the processing parameters on the scaffold's physical properties. Using the biodegradable polymer 85/15 poly(DL-lactide-co-glycolide) acid, the study examined the effects of saturation time (ST), saturation pressure (SP) and NaCL/polymer mass ratio (NaCl/PMR) on the scaffold density, porosity, average pore size, pore density (PD) and Young's modulus in compression.

The article introduces a novel approach to synthesize open-cell polymeric foams for acoustic applications wherein rotational foam molding and particulate leaching are combined. It reports that the process allows for the fabrication of open-cell foams with an average open-porosity percentage of 0.90. Results suggest that the cellular and acoustic properties of the foam fabricated through such method can be controlled by means of using different salt particle sizes.

Adhesion and loading bearing properties of polyurethane (PU) foams and sandwich composite with metallic inserts are studied. Metal or solid polymer anchors are used as the load transfer components for PU foam and sandwich composites when they are used as the structural element in design. The traditional method of fixation of these components in foams is gluing and fastening. In this work, the anchors are in the form of inserts and are imbedded in the PU during the foaming process. Flexural testing was conducted on PU with and without metallic inserts to establish typical interaction trends. The load-deflection response, mode of failure, and fracture stresses of the PU structures are elucidated. Results show that long taper and leaf inserts imbedded in foam and sandwich composite provide better load carrying capacity. Comparisons between the taper and leaf inserts are documented. Leaf inserts inside a foam and sandwich composite show better results as compared to taper inserts in terms of adhesion and failure stresses. A linear elastic fracture model is also developed for the foam beam, and the fracture toughness is calculated. FEA analyses of the interaction between the inserts and the PU and sandwich composites under different loads were carried out. The FEA modeling results coincide with the experimental ones, hence validating the model. [ABSTRACT FROM AUTHOR]

Constitutive modelling of the stress-strain relationship of open-celled PLGA85/15 bioscaffolds under compression was studied. A constitutive model for compressive behaviour was directly derived from the morphology of a unit cubic cell. These constitutive equations describe the stress-strain relationship as a function of the foam's material properties and cell morphology, such as elastic modulus, yield stress, relative density, cell strut thickness, and cell size. To verify this model, uniaxial compression testing was performed on scaffold samples. Using the gas foaming/salt leaching method, the samples were prepared by using different foaming parameters such as salt/polymer mass ratio, saturation pressure, and saturation time. The comparisons of theoretical and experimental data demonstrate that the constitutive model using a cubic unit cell accurately describes the behaviour of PLGA foams with low relative densities under compression. [ABSTRACT FROM AUTHOR]

In this study, the effects of nanoclay on the mechanical properties of poly(methylmethacrylate) (PMMA)/clay nanocomposite foams are investigated. Intercalated PMMA/clay nanocomposites have been prepared through a solvent co-precipitation method. PMMA/clay nanocomposites with only 0.5wt% of well-dispersed montmorillonite nanoclay showed considerable improvement of mechanical properties; specifically in elastic modulus, tensile strength, and elongation at break. However, with an increased load of clay in the nanocomposite, the mechanical properties decreased due to the agglomeration of excessive nanoclay. Microcellular foams have been processed with PMMA/clay nanocomposite material using a subcritical gas foaming method. When a short foaming time is used, the increased amount of nanoclay induced a greater amount of heterogeneous nucleation during the foaming process and therefore decreased the density of the foam. In contrast, when a longer foaming time is used, foam density increased with a larger nanoclay load due to the higher diffusivity coefficient of CO2 blowing agent. Nanoclay, as a nucleation agent and reinforcement filler, changed the foaming behavior and mechanical properties of the PMMA microcellular foams. The microcellular foams made of PMMA/clay nanocomposite with 0.5 wt% exhibited an optimized mechanical response under tonsile experiments. It is observed that the mechanical properties of nanocomposite foams are greatly related to the mechanical properties of unfoamed material and foam density. The nanoclay dispersion quality is a very important factor for the mechanical properties of both foamed and unfoamed polymer/clay nanocomposites. [ABSTRACT FROM AUTHOR]

Examines the glass transition temperature, sorption and diffusion of subcritical carbon dioxide gas in polymethyl methacrylate nanocomposites containing organically modified smectite clay. Formation of large-scale holes within the glassy nanocomposite; Provision of significant property improvements over a neat polymer; Effect of nanoclay loading on the glass transition temperature behavior.

Hydrocarbon leakages are incredibly prominent in today's oil and gas transportation infrastructure, causing several billion dollars of environmental damage annually. Mitigation of this issue is primarily carried out via leak detection sensor systems using fiber optics cables, which are highly prone to failure but are conventionally utilized in industry due to a lack of commercially feasible alternatives. Likewise, sensor solutions in literature have also proven infeasible, featuring high accuracies coupled with difficulties in technology scale-up. Herein we develop a unique hydrocarbon sensor with both scalability and accuracy, using hydrocarbon-soluble polymers in composite chemiresistive sensors. The design's novelty is based on the simple yet highly potent effects of dissolution that take place after exposure to aromatic elements of hydrocarbons pollutants. Large structural deformations are caused in the sensor and can be detected quickly and accurately. In this study, four soluble polymers are characterized for hydrocarbon susceptibility via crude oil exposure, and show large changes in physical and rheological properties. Large electrical sensor response magnitudes are achieved, of up to 180% in 1 h and 27555% in 6 h. Overall, high efficacy in hydrocarbon leak detection is achieved, validating the sensing effectiveness of this unique, hydrocarbon-soluble polymer-based design. • Highly sensitive and scalable sensors for hydrocarbon leak detection are developed. • Four hydrocarbon-dissolvable polymers are designed and tested chemiresistively • Most effective sensor responses measured at +180% in 1 h and +27555% in 6 h. [ABSTRACT FROM AUTHOR]