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Recently, hybrid fillers have been found to be more advantageous in energy-harvesting composites. This study investigated the mechanical and electromechanical performances of silicone rubber-based composites made from hybrid fillers containing conductive nanocarbon black (NCB) and molybdenum disulfide (MoS2). A hybrid filler system containing only 3 phr (per hundred grams of rubber) MoS2 and 17 phr NCB provided higher fracture strain, better tensile strength, and excellent toughness values compared to the 20 phr NCB-only-filled and 5 phr MoS2-only-filled rubber composites. The chemical cross-link densities suggest that NCB promoted the formation of cross-links, whereas MoS2 slightly reduced the cross-link density. The higher mechanical properties in the hybrid filler systems suggest that the filler particles were more uniformly distributed, which was confirmed by the scanning electron microscope study. Uniformly distributed filler particles with moderate cross-link density in hybrid filler systems greatly improved the fracture strain and fracture toughness. For example, the hybrid filler with a 17:3 ratio of NCB to MoS2 showed a 184% increment in fracture toughness, and a 93% increment in fracture strain, compared to the 20 phr NCB-only-filled composite. Regarding electromechanical sensing with 2 kPa of applied cyclic pressure, the hybrid filler (17:3 CB to MoS2) performed significantly better (~100%) than the 20 phr NCB-only compound. This may have been due to the excellent distribution of conducting NCB networks and piezoelectric MoS2 that caused symmetric charging–discharging in the toughened hybrid composite. Thus, hybrid composites with excellent fatigue resistance can find dynamic applications, such as in blood pressure measurement. [ABSTRACT FROM AUTHOR]

The piezo-electric energy harvesting devices based on rubber composites have attracted great attention in the field of flexible electronics. These devices have the ability to provide a voltage of ∼0.5 V when subjected to mechanical strain. In this work, carbon allotropes nanofillers were used to reinforce the room-temperature vulcanized silicone rubber (RTV-SR). The nanofillers added to the rubber matrix were found to improve the compressive modulus, tensile strength, fracture strain, and tensile modulus. For example, the compressive modulus was 1.29 MPa (Virgin) and improved to 1.4 MPa (graphene), 2.3 MPa (CB), 2.2 MPa (CB–graphite hybrid), 2.17 MPa (CB–Nano graphite hybrid), and finally 2.19 MPa (CB–graphene hybrid). Similarly, the fracture strain was 146% (Virgin) and improved to 149% (graphene), 156% (CB), 160% (CB–graphite hybrid), 151% (CB–Nano graphite hybrid), and lastly 178% (CB–graphene hybrid). Moreover, the effect of three different diameters of loading tips is used for voltage production. More areas of deformation during energy harvesting can be able to produce higher voltage output. For example, a 21 mm tip can produce higher energy output than 7 mm and 14 mm. In the end, it was found that formation of cracks in the electrode while repeated loading causes a reduction in voltage output. [ABSTRACT FROM AUTHOR]

In present work, magneto-rheological elastomers (MREs) based on iron oxide (Fe2O3), carbon black (CB) and their hybrid were prepared using room temperature vulcanized silicone rubber (RTV-SR) as host matrix. The rubber composites based MREs were prepared by solution mixing technique. The tests show that the mechanical performance tunes with presence and absence of magnetic field. The mechanical properties such as compressive modulus, tensile strength and fracture strain were higher for hybrid composites than CB or Fe2O3. It was also found that Fe2O3 based MREs specimen shows high magnetic response and stress relaxation than hybrid composites which shows higher mechanical properties. The multi-hysteresis measurement shows that hybrid with higher reinforcing properties exhibit higher heat build-up losses which are a demerit. These demerits can be overcome by improving stress transfer in composite which can be achieved by enhancing interfacial interaction in composite and will be performed in our future work. [ABSTRACT FROM AUTHOR]

Flexible energy harvester can be able to produce continuous voltage output under the mechanical deformations. High temperature vulcanized (HTV) and room temperature vulcanized (RTV) silicone rubbers are used for making the flexible piezo‐electric energy harvester. A total of 1 and 2 phr of multi‐walled carbon nanotube (MWCNT) are used as the electrode material mixed with the rubber solution for the preparation of flexible electrode. Cyclic loading machine is used for the application of 2 Hz of bi‐axial load and uniaxial compression load in the specimen. One centimeter depth of displacement is applied during the bi‐axial cyclic loading and 4 mm amplitude of displacement is applied during the compression loading. Tensile and compression tests are performed to determine the engineering properties of the material. Tensile load withstanding value of the silicone rubber is increasing as increasing the MWCNT filler in the rubber. Tensile value of the pure HTV silicone rubber is 10.020 N and for 2 phr MWCNT reinforced rubber is 22.106 N. Compressive withstanding load of pure HTV rubber is 189.565 N and for 2 phr MWCNT reinforced rubber is 287.066 N. HTV silicone rubber is the highly stiffness material on compares with RTV rubber based on the tensile and the compressive value. Transmission electron microscopy, optical micrographs, and scanning electron microscope show the morphology of MWCNT and surface image of specimen. A total of 2 mm substrate based 2 phr MWCNT reinforced HTV flexible energy harvester undergo decrease in voltage during the cyclic loading due to breakage of electrode. A total of 2 phr MWCNT electrode‐based sample can be able to produce more output voltage than 1 phr MWCNT electrode‐based sample during bi‐axial and compression loading. More voltage is produced in the compression specimen than bi‐axial one. [ABSTRACT FROM AUTHOR]

The stretchable materials exhibit various challenges such as high hysteresis losses, lower magnetic effect, and less magnetic sensitivity. In this work, we design and fabricate stretchable magnetic-rheological elastomers based on silicone rubber with robust magnetic sensitivity and lower hysteresis losses. The nanofillers used were carbon black (CB), and electrolyte iron particle (EIP). The stretchable materials obtained show an anisotropic effect of up to 165%. Moreover, the hysteresis losses were 0.4 kJ (control), 2.45 kJ (15 phr of CB), 0.58 kJ (60 phr of EIP), and 3.53 kJ (60 phr of hybrid filler system). The compressive modulus was 1.4 MPa (control), 3.76 MPa (15 phr of CB), 2.1 MPa (60 phr of EIP), and 3.9 MPa (60 phr of hybrid filler system). The fracture strain was 164% (control), 160% (15 phr of CB), 100% (60 phr of EIP), and 139% (60 phr of hybrid filler system). To sum up, the CB shows robust mechanical properties with high stretchability. However, the hybrid filler system shows high stiffness with a higher magnetic response. Finally, EIP-filled composites show optimum stiffness and robust magnetic response force. [Display omitted] • Stretchable device with magnetic sensitivity was explored in this work. • Stretchable device was fabricated from silicone rubber, electrolyte iron particles, nano-carbon black, and their hybrid. • A magnetic effect of up to 165% was demonstrated in this work. • A low hysteresis loss of 3.9 kJ and a high stretchability of 139% for the hybrid composite was obtained. • The final device has high stretchability, optimum stress-relaxation, and robust magnetic sensitivity. [ABSTRACT FROM AUTHOR]

This study was undertaken to explore the mechanical and magneto-mechanical properties of styrene butadiene rubber (SBR) based magnetorhelogical elastomers (MREs) reinforced with carbonyl iron particles (CIP) as a primary filler. Nanocarbon materials such as nano carbon black (NCB) and few layer graphene (FLG) were used as secondary fillers to reinforce the rubber matrix. The key purpose of this study is to demonstration how the mechanical and magneto-mechanical properties of MREs are related with filler-rubber interactions. CIP can reinforce rubber, although it contains micron size particles, and improvements in moduli and fracture toughness values indicate the formation of filler-rubber networks and interactions between the π-electrons of benzene and the d-orbital electrons of iron. Optimization of CIP filler loadings in SBR was performed using mechanical properties. Tensile strength and elongation at break were increased by increasing CIP loadings up to 15 vol%, and the addition of FLG at 2 vol% further improved mechanical and magneto-mechanical properties as compared with 17 vol% CIP in SBR-based MREs. The study shows that the addition of nano reinforcing filler and an optimum amount of magnetic filler enhances magnetic and mechanical properties, which would be useful for high-energy smart damping systems. [Display omitted] [ABSTRACT FROM AUTHOR]