Introduction: After several years of progresses in textile technology and wearable measurement instrumentation, applications of wearable textile-electronics systems are arising providing a stable background for commercial applications. So far, the available commercial solutions are centered on fitness applications and mostly based in the acquisition of heart rate through Textile Electrodes (Textrodes) based on metallic threads or on conductive rubber compounds. Methods and Materials: In this work a novel material approach is presented to produce Textrodes for acquisition of Electrocardiographic (ECG) signals using a conductive polypropylene (PP1386 from Premix, Finland) polymer material. The polymer was film extruded into thin films, and used as such in the Textrode. Conductive Polymer Films (CPF) have been used to produce Textrodes, and its measurement performance has been compared with the ECG signals obtained with commercial Textrode fabrics and conventional Ag/AgCl electrodes. In order to set up the same measurement conditions, a chest strap tailored to host the testing electrodes has been used. Results: The close resemblance of the ECG acquired with the textile fabric electrodes, the Ag/AgCl electrodes and the PP1386 CPF electrodes suggest that the Polymer Electrodes PP1386 are a feasible alternative to the current textile fabrics that use silver thread as conductive material and also to conductive rubber material. Discussion & Conclusion: The availability of the Conductive Polymer Electrode PP1386 in a film form allows the manufacturing of electrodes by conventional textile processes, like lamination or sewing, therefore facilitating the transition from lab prototyping to industrial manufacturing. Replacing the traditional silver thread as conductive element in the fabrication of Textrodes will definitely reduce the material cost per Textrode. Biocompatibility issues and manufacturability issues must be addressed but the exhibited functional performance is showing encouraging results.
The interconnection between hard electronics and soft textiles remains a noteworthy challenge in regard to the mass production of textile–electronic integrated products such as sensorized garments. The current solutions for this challenge usually have problems with size, flexibility, cost, or complexity of assembly. In this paper, we present a solution with a stretchable and conductive carbon nanotube (CNT)-based paste for screen printing on a textile substrate to produce interconnectors between electronic instrumentation and a sensorized garment. The prototype connectors were evaluated via electrocardiogram (ECG) recordings using a sensorized textile with integrated textile electrodes. The ECG recordings obtained using the connectors were evaluated for signal quality and heart rate detection performance in comparison to ECG recordings obtained with standard pre-gelled Ag/AgCl electrodes and direct cable connection to the ECG amplifier. The results suggest that the ECG recordings obtained with the CNT paste connector are of equivalent quality to those recorded using a silver paste connector or a direct cable and are suitable for the purpose of heart rate detection.
The carding of the Lyocell cellulose fiber was done with a cylindrical cross lap machine supplied by Cormatex Prato, Italy. Several mats were made by carding and needle punching in order to have a compact and well entangled mat suitable for reinforcement. The speed of the cross lap machine, the frequency of needle punching, the number of times the mat goes through needle punching, the feeding rate of the carded fiber and the depth of needle penetration determined the level of entanglement of the Lyocell fiber which ultimately increased the mechanical properties of the fiber. The good mechanical properties of the carded Lyocell fiber made it a renewable and environmentally friendly alternative as reinforcement in composite manufacturing. Compared with other jute fiber reinforced composites, the mechanical properties of the resulting Lyocell composites were found to be better. Regenerated cellulose fiber (Lyocell) composites were environmentally friendly and the mechanical properties were comparable to those of natural fibers.
Composite matrices of poly(ε-caprolactone)-grafted acrylic acid (PCL-g-AA) and hydroxyapatite (HA) were prepared via electrospinning of oil-in-water emulsions. Grafting of varying amounts of AA on PCL was carried out in a twin-screw compounder using benzoyl peroxide as an initiator under inert atmosphere. A solution of PCL-g-AA in toluene, containing HA, comprised the oil phase of the emulsion, while the aqueous phase contained poly(vinyl alcohol) (PVA) as a template polymer. No emulsifier was used in making such emulsions which were found to be stable for more than a month at room temperature. Secondary interactions of AA group of PCL-g-AA with HA and PVA at the oil–water interface provided stability to the emulsion. Uniform composite fibrous matrices were produced from the resultant emulsions under controlled electrospinning conditions. The composite matrices, thus developed using minimal organic solvent, are free from emulsifiers and have high potential to be used in applications including tissue engineering
There is need for the bio‐based materials which could fully or partly replace the synthetic materials in automotive components. Several studies have been suggested to incorporate natural fiber based materials into automotives, and regenerated cellulose fibers could have a great potential several automotive applications. In the paper we will describe ongoing research where we study non‐woven viscose and Lyocell as well as uniaxial continuous viscose filament reinforcements for the use in structural composites. Hybrid reinforcements based on regenerated cellulose fibers and glass fibers have also been studied, with the intention to optimize the reinforcement durability. The uniaxial viscose filament reinforcements were prepared by a winding technique, and we have also combined the viscose filament with continuous hemp yarns as well as different thermoplastic yarns. Both thermoset and thermoplastic composites were then produced by compression moulding with a pressure of 40 bar and at the temperature between 160‐170°C for 5 minutes. The resulting composites have been characterized regarding mechanical and thermal properties.
Blends of polypropylene with multi-walled carbon nanotubes (CNT) have been prepared and melt spun to fibre filaments. The resulted filaments have been characterised regarding conductivity, thermal properties, and morphology. DSC suggests that carbon nanotubes act as nucleating sites in polypropylene and the TGA shows a high increase in thermal stability. Conductivity around 0.001 S/cm are achieved for both as-spun fibre and drawn fibre. A higher load of CNT up to 15 wt % increases the conductivity to 2.8 S/cm in as-spun fibre, but due to a high fibre diameter variation during spinning resulting in fibre breakage, melt spinning is very difficult. This is due to a non-uniform stress distribution during the drawing steps which can be a result of a non-homogeneous PP-CNT blend and the spinning machine process limitations. Differences in conductivities for extruded rods, as-spun fibre and drawn fibre which are made from the same blends, suggests that the crystallinity can affect the conductivity of the PP/CNT fibre.
This presentation will discuss some on-going efforts regarding the development of conductive fibres by melt spinning of polyaniline-polypropylene blends. The blend was also modified with multi wall carbon nanotubes. The presentation will also review in the literature presented concepts regarding processing and manufacture of electrically conductive textile fibres.
Ternary blends of polypropylene/polyamide-6/Polyaniline-complex and binary blends of PP/ Polyaniline-complex were prepared and melt spun to conductive fibers under different solid-state draw ratios. Both blends showed a dependency of the conductivity to the fiber draw ratio. Compared to the binary blend fibers, the ternary blend fibers showed a more linear voltage-resistance relationship, a smoother surface and more even fiber in SEM images, and could combine a good conductivity with a good mechanical strength, because their maximum conductivity was observed in fibers made under a higher draw-ratio where the fibers show a better mechanical strength. The mechanical properties were promising to be used in a knitted network.
Melt spun drawn fibers were prepared using a ternary blend of PP/PA6/PANI-complex (polypropylene/polyamide-6/polyaniline-complex). Their electrical and mechanical properties were compared to those of binary blend fibers of PP/PANI-complex. The results of the morphological studies on 55:25:20 PP/PA6/PANI-complex ternary fibers were found to be in accordance with the predicted morphology for the observed conductivity vs. fiber draw ratio. The scanning electron microscopy (SEM) micrographs of the ternary blend illustrated at least a three-phase morphology of a matrix/core-shell dispersed phase style, with widely varying sizes of droplets. This resulted in a dispersed morphology that, in some parts of the blend, approached a bicontinuous/dispersed phase morphology due to coalescence of the small droplets. The matrix was PP and the core-shell dispersed phase was PA6 and PANI-complex, in which a part of the PANI-complex had encapsulated the PA6 phase and the remaining was solved/dispersed in the PA6 core, as later confirmed by X-ray mapping. When the ternary blend fibers were compared to the binary fibers, the formers were able to combine better conductivity (of an order of 10−3 S cm−1) with a greater tensile strength only at a draw ratio of 5. This indicated that the draw ratio is more critical for the ternary blend fibers, because both conductivity and tensile strength depended on the formation of fibrils from the core-shell dispersed phase of the PA6/PANI-complex.
Blends of polypropylene with polyaniline and multi-walled carbon nanotubes have been prepared and melt spun to fibre filaments. The resulted filaments have been characterised regarding conductivity, morphology, thermal and mechanical properties. DSC suggests that carbon nanotubes act as nucleating sites for PP/polyaniline blend. Electrical conductivity has been measured for blends with extruded rod shape, as-spun fibre filaments and fibres made under draw ratio of four. Polypropylene containing 20 wt% polyaniline polymer modified with 7.5 wt% carbon nanotubes shows the maximum conductivity among all the samples, about 0.16 S/cm.
Ternary blends of polyaniline-complex, polypropylene and multiwalled carbon nanotubes have been prepared and melt spun to fibre filaments. Prepared filaments have been characterised regarding electrical and thermal properties as well as microscopic morphology. Electrical conductivity measurements showed that the maximum conductivity is obtained in polypropylene containing both CNT and Polyaniline rather than polypropylene with only one of the conductive materials. In SEM images for cross section of as-spun fibres, PP/polyaniline-complex/CNT shows much more homogeneous structure than PP/polyaniline-complex prepared at the same blending and spinning conditions. Fibres made of PP/CNT and PP/ CNT/polyaniline-complex show the electrical resistance dependency on time as well as applied voltage within the chosen range of measurements.
Electrically conductive composites containing polypropylene (PP) and polyaniline (PANI) were prepared using PP with three different melt flow rates (MFRs) and a commercial PANI-complex in proportions of 80% by weight and 20%, respectively. Composite blends were melt-spun to fibers under different solid-state draw ratios. Rheological studies of dynamic viscosity, as well as the storage modulus and loss modulus showed that the prepared PANI-complex/PP blends exhibit different dynamic rheological behavior, depending on the PP used. This confirms the blends' morphological differences. PP matrix viscosity was found to play an important role in the electrical properties of the prepared fibers. Fibers prepared using the matrix with the lowest viscosity, showed a larger dispersed phase size in the cross-sectional SEM micrographs, maximum conductivity observed at higher draw ratios and a more linear resistance–voltage relationship than those of the fibers prepared using the higher viscosity matrices.
A melt-processable polyaniline complex was blended with polypropylene under different mixing conditions and melt-spun into fiber filaments under different draw ratios. The conductivity, electrical resistance at different voltages, and morphological characteristics of the prepared fibers were investigated. The morphology of this two-phase blend was demonstrated to have a large effect on the conductivity level and the linearity of the resistance–voltage relationship of the blend fibers. Two factors had substantial effects on the morphology and electrical properties of the fibers. They were the size of the initial dispersed conductive phase, which depended on the melt blending conditions, and the stress applied to orient this phase to a fibril-like morphology, which was controlled by the draw ratio of the fiber. The two factors were shown to be associated with each other to maintain an appropriate balance of fibril formation and breakage and to create continuous conductive pathways.