Flexible N-Type Thermoelectric Composites Based on Non-Conductive Polymer with Innovative Bi2Se3-CNT Hybrid Nanostructured Filler

This research is devoted to the fabrication of polyvinyl alcohol (PVOH) based n-type thermoelectric composites with innovative hybrid bismuth selenide-multiwalled carbon nanotube (Bi2Se3-MWCNT) fillers for application in flexible thermoelectric devices. Hybrid fillers were synthesized by direct deposition of Bi2Se3 on multiwalled carbon nanotubes using a physical vapor deposition method, thus ensuring direct electrical contact between the carbon nanotubes and Bi2Se3. The Seebeck coefficient of prepared PVOH/Bi2Se3-MWCNT composites was found to be comparable with that for the Bi2Se3 thin films, reaching −100 µV·K−1 for the composite with 30 wt.% filler, and fluctuations of the resistance of these composites did not exceed 1% during 100 repetitive bending cycles down to 10 mm radius, indicating the good mechanical durability of these composites and proving their high potential for application in flexible thermoelectrics. In addition, other properties of the fabricated composites that are important for the use of polymer-based materials such as thermal stability, storage modulus and linear coefficient of thermal expansion were found to be improved in comparison with the neat PVOH

Single Phase Earth Fault Impact on Underground Cable Outer PE Jacket in MV Isolated Neutral Systems

In case of single phase earth fault in medium voltage (MV) isolated neutral systems, the voltages of the remaining two phases to the earth raise from normal phase to neutral voltage to full line value, i.e., 3 times their normal value. This causes the stress, e.g., thermal stress on the inner insulation and also on the outer polyethylene (PE) jacket, which is the weakest point in the cable. Differential scanning calorimetry (DSC) monitors heat effects associated with phase transitions, e.g., crystallization, and chemical reactions as a function of temperature. The knowledge of the crystallization mechanisms of polymers presents a fundamental importance, since the degree of crystallinity influences the mechanical and thermal properties of these materials. In this paper the percentage of crystallinity of an underground cable outer PE jacket have been calculated from a peak of exothermic crystallization of differential scanning calorimetry (DSC) thermograms

Durable Hydrophobic Sol-Gel Finishing for Textiles

The surface of cotton textile was modified to create a water-repellent finishing by depositing a modifying coatings using the sol-gel technique. Treated textiles evaluated using scanning electron microscopy, X-Ray powder diffraction (XRD). The wettability of treated fabrics was characterized by water contact angle and drop test. The results showed that the cotton textile treated with 7.5 wt.% zinc acetate dihydrate sol showed excellent hydrophobic properties, water contact angle could reach 145°C without decreasing after 50 hydrothermal treatment cycles

Durable Hydrophobic Sol-Gel Finishing for Textiles

The surface of cotton textile was modified to create a water-repellent finishing by depositing a modifying coatings using the sol-gel technique. Treated textiles evaluated using scanning electron microscopy, X-Ray powder diffraction (XRD). The wettability of treated fabrics was characterized by water contact angle and drop test. The results showed that the cotton textile treated with 7.5 wt.% zinc acetate dihydrate sol showed excellent hydrophobic properties, water contact angle could reach 145°C without decreasing after 50 hydrothermal treatment cycles

Modified Silyl-Terminated Polyether Polymer Blends with Bisphenol A Diglycidyl Ether Epoxy for Adhesive Applications

Modified silyl-terminated polyether polymer (MS Polymer) was blended with bisphenol A diglycidyl ether (DGEBPA) epoxy at MS Polymer/epoxy ratio from 30/70 to 70/30. MS Polymer/epoxy systems were examined for two-component adhesive formulation with additional fillers. Applicability of the MS Polymer/epoxy system at the ratio of the components 60/40 is demonstrated for the development of adhesive formulation. Rheological analysis of the components A and B shows suitable viscosity values for development of two- component adhesives formulation. Curing dynamics as well as tensile stress-strain properties and Shore A hardness of the chosen adhesive formulation are reasonable for the development of MS Polymer/epoxy type adhesive

Multifunctional Aromatic Polyester Based Composites

Under the scope of this investigation, several characteristic features of the poly(ethtlene terephtalate) PET based systems are revealed. It is demonstrated that with increase of PET content, hardness, indentation modulus as well as tensile strength and modulus are substantially increased. Superelasticity of the investigated multiphase composites, in its turn, increase by increasing the concentration of low-modulus component. The effect of radiation modification on the properties of the investigated systems is strongly dependant on the composition of the blends. It is also shown, that there is strong correlation between morphology, structural properties (density, crystallinity, content of the voids) and micro and macro stress-strain properties of the investigated systems. Consequently, one can conclude that certain stress-strain properties of the investigated multifunctional systems can be predicted by means of mathematical models based on the morphology

Rheological, Mechanical and Adhesion Properties of Two Component Adhesive based on Modified Silyl-Terminated Polyether Polymer and Epoxy Resin

Today an increasing interest in two component adhesive products can be sensed in the market. The driving force requesting more specific adhesive materials is automotive industry for bonding of light-weight structures or challenging designs. These requirements from industry make to seek for new raw material types to formulate adhesive systems with higher strength, broad superior adhesion spectrum and other demanding properties. The combination of epoxy resin with modified silyl-terminated polyether polymer (MS Polymer) is supposed to deliver a two component adhesive that shows superior strength compared to pure MS Polymer based adhesives, while combining all the other positive features from both polymer resin types. In two component adhesive formulation MS Polymer and epoxy hardener are main ingredients of one component and epoxy, MS Polymer catalyst and water are main ingredients of other component. Depending on the amount of methoxysilyl groups various MS Polymer types, namely, di-functional MS Polymers (DMS) and tri-functional MS Polymers (TMS), were used. Rheological characteristics were measured by using Bohlin CVO 100 rheometer. Instrument was equipped with 20 mm diameter spindle in plate-plate geometry with gap size 1000 m. Tests at 23 oC were performed in oscillatory shear mode at frequency 1.5 Hz and strain 0.15. Dynamic storage G’ and loss moduli G” were recorded as functions of the reaction time. Adhesive and tensile stress-strain characteristics were determined by using Zwick/Roell Z010 universal testing machine. Tensile tests were made according to DIN 53504. Lap shear tests were made according to EN 1465. Samples were tested after 1, 7, 14, 21 and 28 days of curing