Mechanical, electrical and electro-mechanical properties of thermoplastic elastomer styrene–butadiene–styrene/multiwal carbon nanotubes composites

Composites of styrene–butadiene–styrene (SBS) block copolymer with multiwall carbon nanotubes were processed by solution casting to investigate the influence of filler content, the different ratios of styrene/butadiene in the copolymer and the architecture of the SBS matrix on the electrical, mechanical and electro-mechanical properties of the composites. It was found that filler content and elastomer matrix architecture influence the percolation threshold and consequently the overall composite electrical conductivity. Themechanical properties aremainly affected by the styrene and filler content. Hopping between nearest fillers is proposed as the main mechanism for the composite conduction. The variation of the electrical resistivity is linear with the deformation. This fact, together with the gauge factor values in the range of 2–18, results in appropriate composites to be used as (large) deformation sensors.

An e-marketplace of healthcare and social care services: the perceived interest

Purpose – The health and social care sector is receiving growing attention due to the increased life expectancy and to the public demand for a better quality of life and better health services. New cost-efficient approaches are required, and the paper aims to present and discuss the main results of a study undertaken in a Portuguese municipality on the perceived relevance of an e-marketplace of social and healthcare services for the inhabitants in general, and for people with special needs in particular, and the identification of the most relevant services to be offered through this platform. Design/methodology/approach – A wide survey was undertaken to identify the needs of potential users and their expectancies with relation to the proposed platform. The results of the study are a support for the project promoters to understand the viability of the solution and the requirements to the deployment of the pilot experiment, as well as to drive the selection of domains of activities/classes of services to be offered by the platform. Findings – Services such as information about healthcare services, home monitoring/accompanying services 24 hours per day, and personal hygiene services provided at home are the ones recognized by the inquired citizens as the most important, which indicates that the potential users will be mostly people with special needs or their family or caregivers. Originality/value – While still at a preliminary development phase, the project represents a good opportunity to develop a totally innovative service with high potential impact for the senior population and for individuals with special needs.

Mechanical, electrical and electro-mechanical properties of thermoplastic elastomer styrene–butadiene–styrene/multiwall carbon nanotubes composites

Composites of styrene–butadiene–styrene (SBS) block copolymer with multiwall carbon nanotubes were processed by solution casting to investigate the influence of filler content, the different ratios of styrene/butadiene in the copolymer and the architecture of the SBS matrix on the electrical, mechanical and electro-mechanical properties of the composites. It was found that filler content and elastomer matrix architecture influence the percolation threshold and consequently the overall composite electrical conductivity. The mechanical properties are mainly affected by the styrene and filler content. Hopping between nearest fillers is proposed as the main mechanism for the composite conduction. The variation of the electrical resistivity is linear with the deformation. This fact, together with the gauge factor values in the range of 2–18, results in appropriate composites to be used as (large) deformation sensors.

On the origin of the electrical response of vapor grown carbon nanofiber + epoxy composites

The origin of the electrical response of vapor grown carbon nanofiber (VGCNF) + epoxy composites is investigated by studying the electrical behavior of VGCNF with resin, VGCNF with hardener and cured composites, separately. It is demonstrated that the onset of the conductivity is associated to the emergence of a weak disorder regime. It is also shown that the weak disorder regime is related to a hopping depending on the physical properties of the polymer matrix.

Temperature dependence of the electrical conductivity of vapor grown carbon nanofiber/epoxy composites with different filler dispersion levels

The influence of the dispersion of vapor grown carbon nanofibers (VGCNF) on the electrical properties of VGCNF/epoxy composites has been studied. A homogeneous dispersion of the VGCNF does not imply better electrical properties. The presence of well distributed clusters appears to be a key factor for increasing composite conductivity. It is also shown that the main conduction mechanism has an ionic nature for concentrations below the percolation threshold, while above the percolation threshold it is dominated by hopping between the fillers. Finally, using the granular system theory it is possible to explain the origin of conduction at low temperatures.

The role of disorder on the AC and DC electrical conductivity of vapour grown carbon nanofibre/epoxy composites

Four dispersion methods were used for the preparation of vapour grown carbon nanofibre (VGCNF)/epoxy composites. It is shown that each method induces certain levels of VGCNF dispersion and distribution within the matrix, and that these have a strong influence on the composite electrical properties. A homogenous VGCNF dispersion does not necessarily imply higher electrical conductivity. In fact, it is concluded that the presence of well distributed clusters, rather than a fine dispersion, is more important for achieving larger conductivities for a given VGCNF concentration. It is also found that the conductivity can be described by a weak disorder regime.

Modeling Carbon Nanotube Electrical Properties in CNT/Polymer Composites

In this work it is demonstrated that the capacitance between two cylinders increases with the rotation angle and it has a fundamental influence on the composite dielectric constant. The dielectric constant is lower for nematic materials than for isotropic ones and this can be attributed to the effect of the filler alignment in the capacitance. The effect of aspect ratio in the conductivity is also studied in this work. Finally, based on previous work and by comparing to results from the literature it is found that the electrical conductivity in this type of composites is due to hopping between nearest fillers resulting in a weak disorder regime that is similar to the single junction expression.

An e-marketplace of healthcare and social care services: the perceived interest

The health and social care sector is receiving growing attention for the last years, due to the increased life expectancy, the public demand for a better quality of life and for better health services. These requirements can be met with more cost-efficient approaches and using new technology-based solutions for providing services. The paper presents and discusses some of the main results of a study undertaken in Guimarães, a Municipality at the North of Portugal, on the perceived relevance of an e-Marketplace of social and healthcare services for the inhabitants in general, and in particular for people with special needs; the study also included the identification of the most relevant services to be offered by this platform and allowed concluding that such an e-Marketplace is of recognized relevance and that it is expected a good adhesion from the population.

Coupling Mechanical and Electrical Behavior in the Multi-scale Simulation of Polymer-based CNT Nanocomposites

A numeric model has been proposed to investigate the mechanical and electrical properties of a polymeric/carbon nanotube (CNT) composite material subjected to a deformation force. The reinforcing phase affects the behavior of the polymeric matrix and depends on the nanofiber aspect ratio and preferential orientation. The simulations show that the mechanical behavior of a computer generated material (CGM) depends on fiber length and initial orientation in the polymeric matrix. It is also shown how the conductivity of the polymer/CNT composite can be calculated for each time step of applied stress, effectively providing the ability to simulate and predict strain-dependent electrical behavior of CNT nanocomposites.

The influence of matrix mediated hopping conductivity, filler concentration, aspect ratio and orientation on the electrical response of carbon nanotube/polymer nanocomposites

A model to simulate the conductivity of carbon nanotube/polymer nanocomposites is presented. The proposed model is based on hopping between the fillers. A parameter related to the influence of the matrix in the overall composite conductivity is defined. It is demonstrated that increasing the aspect ratio of the fillers will increase the conductivity. Finally, it is demonstrated that the alignment of the filler rods parallel to the measurement direction results in higher conductivity values, in agreement with results from recent experimental work.

The influence of the dispersion method on the electrical properties of vapor-grown carbon nanofiber/epoxy composites

The influence of the dispersion of vapor-grown carbon nanofibers (VGCNF) on the electrical properties of VGCNF/ Epoxy composites has been studied. A homogenous dispersion of the VGCNF does not imply better electrical properties. In fact, it is demonstrated that the most simple of the tested dispersion methods results in higher conductivity, since the presence of well-distributed nanofiber clusters appears to be a key factor for increasing composite conductivity.

Dashboard services for pragmatics-based interoperability in cloud and ubiquitous manufacturing

The real Cloud and Ubiquitous Manufacturing systems require effectiveness and permanent availability of resources, their capacity and scalability. One of the most important problems for applications management over cloud based platforms, which are expected to support efficient scalability and resources coordination following SaaS implementation model, is their interoperability. Even application dashboards need to easily incorporate those new applications, their interoperability still remains a big problem to override. So, the possibility to expand these dashboards with efficiently integrated communicational cloud based services (cloudlets) represents a relevant added value as well as contributes to solving the interoperability problem. Following the architecture for integration of enriched existing cloud services, as instances of manufacturing resources, this paper: a) proposes a cloud based web platform to support dashboard integrating communicational services, and b) describe an experimentation to sustain the theory that the effective and efficient interoperability, especially in dynamic environments, could be achieved only with human intervention.

Effect of cylindrical filler aggregation on the electrical conductivity of composites

This work reports on the effect of carbon nanotube aggregation on the electrical conductivity and other network properties of polymer/carbon nanotube composites by modeling the carbon nanotubes as hard-core cylinders. It is shown that the conductivity decreases for increasing filler aggregation, and that this effect is more significant for higher cylinder volume fractions. It is also demonstrated, for volume fractions at which the giant component is present, that increasing the fraction of cylinders within clusters leads to a break of the giant component and the formation of a set of finite clusters. The decrease of the giant component with the increase of the fraction of cylinders within the cluster can be related to a decrease of the spanning probability due to a decrease of the number of cylinders between the clusters. Finally, it is demonstrated that the effect of aggregation can be understood by employing the network theory.

Information technology supporting healthcare and social care services

The authors are developing a pilot project for a Municipality in the North of Portugal, envisaging the definition and implementation of an e-marketplace for healthcare and social services, in order to facilitate the interaction between healthcare and social services professionals and people with special needs (or their relatives). Based on the results of a survey on user needs analysis and expectations conducted in 2011, the paper discusses the relevance and interest of such platforms and the main drivers and motivations of the population for using such services, as well as which services would motivate citizens to use the platform. The results of the study will be used to select the products and services perceived to be the most desired by the potential users. The paper thus makes three main contributions: (1) the results of the study confirm the interest and the perceived potential of such a service, from the end-users perspective; (2) the findings support the advantage of expanding this pilot project to a full scale implementation; and (3) the performed analysis improves our understanding of the relations between the characteristics of the inquired population and the perceived interest in such platforms.

The impact of the digital divide on the perceived interest of an e-Marketplace to support healthcare and social care services

In a Europe increasingly aging, it is now recognized the importance and potential of the service industry for ageing well based on information and communication technologies (ICT), as exemplified by the electronic market of social services and health care, the GuiMarket, proposed by the authors. However, this new range of services requires that individuals have advanced digital skills to fully participate in society. Based on the results of a survey made on a sample of 315 individuals, this paper discusses the importance granted GuiMarket and the intended frequency of use, concluding there is a close relationship between ICT access and use that respondents anticipate making of GuiMarket and alike services.