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The layer-by-layer nature of additive manufacturing is well matched to the layer construction of stacked dielectric actuators, with inkjet printing offering a unique opportunity due to its droplet-on-demand capability, suitable for multi-material processing at high resolution. This paper demonstrates the use of high viscosity, multi-material jetting to deposit two-part reactive inks with functionalised nanofillers to digitally manufacture dielectric elastomers for soft robots with high precision and shape manipulation. Graphene-based fillers, including graphene oxide (GO) and thermally reduced graphene oxides (TRGOs), have been incorporated into a polydimethylsiloxane (PDMS) matrix at low loading (below the percolation threshold). Consequently, the dielectric constant of the elastomer dramatically increases (by 97 %) compared to neat PDMS, yielding a more than twenty-fold increase in the electric-field induced electromechanical contraction (from 0.3 to 6.7 %). This study shows that the oxygen-functionalities present in GO and TRGOs, which possess a moderate conductivity, improve the dispersion of those fillers in polymer matrices, thus significantly improving the dielectric constant of the polymer composites. Inkjet printing of high-performance, soft electroactive composites enables high-speed, reliable fabrication of monolithic artificial muscles (leading to stronger, cheaper, and more capable soft robotic devices) and provides a vital steppingstone towards fully additively manufactured soft robots.

The formulation of a high dielectric permittivity ceramic/polymer composite feedstock for daylight vat photopolymerization 3D printing (3DP) is demonstrated, targeting 3DP of devices for microwave and THz applications. The precursor is composed of a commercial visible light photo-reactive polymer (VIS-curable photopolymer) and dispersed titanium dioxide (TiO2, TO) ceramic nano-powder or calcium copper titanate (CCT) micro-powder. To provide consistent 3DP processing from the formulated feedstocks, the carefully chosen dispersant performed the double function of adjusting the overall viscosity of the photopolymer and provided good matrix-to-filler bonding. Depending on the ceramic powder content, the optimal viscosities for reproducible 3DP with resolution better than 100 &micro, m were &eta, (TO) = 1.20 &plusmn, 0.02 Pa.s and &eta, (CCT) = 0.72 &plusmn, 0.05 Pa.s for 20% w/v TO/resin and 20% w/v CCT/resin composites at 0.1 s&minus, 1 respectively, thus showing a significant dependence of the &ldquo, printability&rdquo, on the dispersed particle sizes. The complex dielectric properties of the as-3D printed samples from pure commercial photopolymer and the bespoke ceramic/photopolymer mixes are investigated at 2.5 GHz, 5 GHz, and in the 12&ndash, 18 GHz frequency range. The results show that the addition of 20% w/v of TO and CCT ceramic powder to the initial photopolymer increased the real part of the permittivity of the 3DP composites from &epsilon, &rsquo, = 2.7 &plusmn, 0.02 to &epsilon, (TO) = 3.88 &plusmn, 0.02 and &epsilon, (CCT) = 3.5 &plusmn, 0.02 respectively. The present work can be used as a guideline for high-resolution 3DP of structures possessing high-&epsilon

An investigation on antenna solutions for expendable origami paper flapping robots is presented. An origami flapping robotic bird that can be produced using standard A4 paper is employed. Antennas resonating at the two commonly used frequency bands, 2.4 GHz and 5.2 GHz, are designed for the limited space available on the folded origami structure. Two developments of the same dual-band monopole antenna are discussed. The first antenna is located on the robot's spine and the second on its tail. A space diversity configuration is also studied. The antennas are printed directly onto a photo paper substrate and then folded into an origami robotic crane's body structure. An ordinary desktop inkjet printer fitted with silver nanoparticle conductive ink cartridges has been employed. CST Microwave StudioTM has been used to design the antennas. A good agreement between the measured and simulated S11 results is achieved with a reasonable -10dB impedance bandwidth realized in the three cases studied. The radiation patterns are omnidirectional in the XZ plane which is desirable for the specific application. The diversity configuration has a mutual coupling of

The effects of expanded graphite (EG)/carbon black (CB) hybrid nanofillers on the physical, mechanical, thermo-mechanical, electrical and barrier properties of butyl rubber (IIR) vulcanizates have been widely investigated in the present study. Chemical treatment followed by a thermal exfoliation of natural graphite flakes have been done to synthesize EG. EG was further modified by treating it with mixed acid that resulted in an increase in the number of polar groups on its surface which indeed improves interfacial adhesion between the EG and rubber matrix as well as facilitates the curing reaction. The presence of different functional groups on the surface of modified EG (MEG) is confirmed by fourier transforms infrared spectroscopic (FT-IR) analysis. Significant increase in the d-spacing of MEG was observed from the wide angle X-ray diffraction analysis. The morphology of the IIR based hybrid nanocomposites have been investigated by high resolution transmission electron microscopy (HR-TEM). EG and MEG loaded IIR based nanocomposites with and without CB show an increase in the mechanical, thermo-mechanical, electrical, thermal and barrier properties compared to the neat polymer.

This article explores the synergistic effect of halloysite nanotubes along with maleic anhydride grafted polyethylene on the physical, mechanical, and thermo-mechanical properties of polycarbonate/cyclic olefin copolymer polymer blend system. Halloysite nanotubes filled polycarbonate/cyclic olefin copolymer blend nanocomposites were prepared in the presence and absence of polymeric compatibilizer by melt blending. Besides the constructive outcome of nanotubular fillers, the maleic anhydride grafted polyethylene played a complementary role in improving the properties of the nanocomposites. Structural changes of blend matrix, nanofiller distributions, nanofiller-polymer matrix interaction, nucleating effect, storage modulus, and thermal stability were widely investigated with various sophisticated instruments.

The present research work demonstrated the effect of graphene oxide (GO) on the physical, mechanical, thermo-mechanical etc., properties of neoprene (CR) and chlorosulfonated polyethylene (CSPE) vulcanizates. CR and CSPE based nanocomposites were prepared by both solution intercalation and melt intercalation methods. The changes obtained in the morphology, cure characteristics, mechanical, thermal, thermo-mechanical properties of the rubber nanocomposites have been widely investigated. X-ray diffraction analysis (XRD) and transmission electron microscopic (TEM) analysis of the samples revealed partial exfoliated structure of GO containing rubber composites. Mechanical, thermal, cure and thermo-mechanical properties of the elastomeric nanocomposites were improved compared to the neat rubbers.

Nanocomposites of polyether imide (PEI) and liquid crystalline polymer (LCP) with either MWCNT, Expanded Graphite (EG) or in combination of both EG and PEI- co -Silicon Rubber were prepared by melt blending process. The compatibility between the polymeric phases (PEI&LCP) was observed to be increased by the addition of PEI- co -Silicon Rubber while the only MWCNT added system (PLC) resulted in smaller LCP droplets. A continuous morphology was produced in presence of both PEI- co -Silicon Rubber and EG both added system (PLGR). This was due to the compatibilizing effect of PEI- co -Silicon Rubber. FTIR analysis revealed interaction between PEI and LCP in presence of PEI- co -Silicon Rubber. Remarkable increment of storage modulus was observed with the addition of EG and PEI- co -Silicon Rubber. Transmission Electron Microscope (TEM) analysis showed better dispersion of multiple graphene layers of EG in presence of PEI- co -Silicon Rubber compatibilized system. Tensile and Young’s modulus both were highest for EG/ PEI- co -Silicon Rubber added system. This is due to flexible compatibilizing effect of PEI- co -Silicon Rubber which delayed the detachment of LCP domain from the PEI matrix and thus detains the fracture.

The excellent mechanical, thermal, and electrical properties, as well as the large aspect ratio of graphene have made it a subject of significant scientific attraction. Graphene/rubber nanocomposites are the multifunctional rubber materials that are fabricated by incorporating graphene or oxidized state of graphene sheets into different rubber matrices. The present chapter deals with the different synthesis procedures of graphene oxide (GO), reduced GO, and graphene, along with their physicochemical characterizations. The present chapter also explores the different fabrication methods and several characterizations (physical, mechanical, electrical, etc.) of graphene based rubber nanocomposites. Various fabrication methods adopted by the researchers to achieve significant dispersion of graphene have been discussed. Several rubber nanocomposites filled with graphene/functionalized graphene based on different rubber vulcanizates have been described concerning their preparation and different properties. Depending on the rubber–graphene structure formation at very low loading as well as interactions between each other, the mechanical, dynamic-mechanical, thermal, dielectric, etc. properties are generally changed. The formation of filler–filler networks in the rubber nanocomposites is generally responsible for the drastic increase in the electrical conductivity of the rubber nanocomposite materials.

This report deals with the development of unmodified and modified halloysite nanotube (HNT) based cyclic olefin copolymer (COC) composites. Maleic anhydride grafted polyethylene (MA-g-PE) has been used as a compatibilizer. Exfoliation of organically modified HNTs (mHNTs) and dispersion of it in polymer matrix was observed by X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy analysis, respectively. Augmented dynamic mechanical and thermal properties of the composites were provided by incorporating mHNTs into the pure matrix. In this work, we have proposed that the modification of HNTs enhanced the dispersion and strong interfacial interaction which led to better performance of the composites where MA-g-PE acts as a bridging tool between polar clays and nonpolar COC. POLYM. COMPOS., 36:955–960, 2015. © 2014 Society of Plastics Engineers

The present research work explored the effect of expanded graphite (EG) and modified EG (MEG) with and without carbon black (CB) on the mechanical, dynamic mechanical, thermal etc. properties of ethylene propylene diene terpolymer (EPDM). EG-and MEG-filled EPDM nanocomposites were fabricated in the presence and absence of CB by direct mixing on an open two roll mill. The microstructure of the EPDM-based nanocomposites was investigated by wide angle X-ray diffraction (WAXD) and high-resolution transmission electron microscopic (HR-TEM) analyses. EG- and MEG-loaded EPDM nanocomposites in the presence and absence of CB exhibited improved mechanical, dynamic mechanical properties and thermal stability.

The aim of the present research work is to develop expanded graphite (EG) and isocyanate modified graphite nanoplatelets (i-MG) filled SBR/BR blends, which can substitute natural rubber (NR) in some application areas. The present study investigated the effect of i-MG on the physical, mechanical and thermo-mechanical properties of polybutadiene rubber (BR), styrene butadiene rubber (SBR) and SBR/BR blends in the presence of carbon black (CB). Graphite sheets were modified to enhance its dispersion in the rubber matrices, which resulting in an improvement in the overall physical and mechanical properties of the rubber vulcanizates. Compounds based on 50:50 of BR and SBR with ∼3 wt% nanofillers with CB were fabricated by melt mixing. The morphology of the filled rubber blends was investigated by wide angle X-ray diffraction (WAXD) and high resolution transmission electron microscopic (HR-TEM) analyses. The intercalated and delaminated structures of the nanofiller loaded rubber blends were observed. Scanning electron microscopic (SEM) analysis of the cryo-fractured surfaces of the rubber compounds showed more rough and tortuous pathway of the fractured surfaces compared to the fractured surfaces of the only CB loaded rubber composites. Filled rubber compounds exhibit increase in the Δ S (torque difference) value, reduced scorch and cure time compared to their respective controls. Dynamic mechanical thermal analysis (DMTA) of the filled rubber compounds shows an increase in the storage modulus compared to the controls. Isocyanate modified graphite nanoplatelets (i-MG) containing rubber compounds in the presence of CB showed an increase in the mechanical, dynamic mechanical, hardness, abrasion resistance and thermal properties compared to the alone CB filled rubber vulcanizates.

The present research work demonstrated the reinforcing effect of expanded graphite (EG) and modified EG (MEG) with and without carbon black (CB) on the physical, mechanical and thermo-mechanical properties of emulsion polymerized styrene butadiene rubber (SBR) vulcanizates. In separate batches, EG and MEG flakes with and without CB were incorporated into the SBR by melt blending. The microstructures of the nanocomposites were precisely characterized by wide angle X-ray diffraction (WAXD) analysis and high resolution transmission electron microscope (HR-TEM). EG and MEG filled SBR compounds showed improvement in the curing features, mechanical, thermal and dynamic mechanical properties than their respective controls.

Dual filler (organoclay and carbon black) loaded emulsion polymerized styrene butadiene rubber (E-SBR) based nanocomposites were synthesized by melt blending. Three different organically modified clays (viz. Cloisite 15A, Cloisite 20A and Cloisite 30B) were used for the present study. To disperse different organoclays selectively in the rubber matrix, oil extended carboxylated styrene butadiene rubber (XSBR) was used as a compatibilizer between organoclay and the nonpolar SBR. Wide angle X-ray diffraction analysis (WAXD) and high resolution transmission electron microscopic (HR-TEM) analysis of the nanocomposites revealed that the organoclays were intercalated and delaminated in the elastomer matrix in the presence of carbon black (CB). Different organoclay loaded SBR compounds show improvement in the overall properties such as curing features, mechanical, thermal, abrasion resistance and dynamic mechanical properties compared to the neat SBR. Among the three different hybrid nanocomposites, Cloisite 30B filled SBR compound in the presence of CB show superior properties.

Ultrasonic welding have been studied using Polycarbonate (amorphous) and Polypropylene (semi-crystalline) in presence and absence of polymeric compatibilizer. A solution phase compatibilization has been used using Polycaprolactone, Polymethylmethacrylate and Maleic anhydride grafted Polypropylene. Cylindrical samples were used in the near and far field ultrasonication in order to achieve the better weldability. The welding strength was increased while utilizing the compatibilizer than that of un-compatibilized samples. Mixture of Polycarbonate and Polymethylmethacrylate on the PC phase enhanced the weld strength tremendously. The XRD analysis revealed the increase in crystallinity during the ultrasonication process resulting the enhanced weldability. The phase fusion is quite prominent from the SEM study of the fractured surface and also from the SEM of the welded portion. The FTIR study indicated the phase interaction through the compatibilizer thus enhancing the ultrasonic weldability of the thermoplastics.

Supercapacitors have evolved as the premier choice of the era for storing huge amounts of charge in the field of energy storage devices, but it is still necessary to enhance their performance to meet the increasing requirements of future systems. This could be achieved either through advancing the interfaces of the material at the nanoscale or by using novel material compositions. We report a high-performance material composition prepared by combining a transition metal (palladium)-doped conductive polymer with multiwalled carbon nanotubes (MWCNTs). MWCNTs/palladium-doped polyaniline (MWCNTs/Pd/PANI) composites and multiwalled carbon nanotube/polyaniline (MWCNTs/PANI) composites (for comparison) were prepared via in situ oxidative polymerization of aniline monomer. The reported composites were characterized by Fourier-transform infrared (FTIR), x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) studies. FESEM and TEM studies indicated the narrow size distribution of the π-conjugated polymer-protected palladium nanoparticles on the surface of the carbon nanotubes. All the electrochemical characterizations were executed using a three-electrode system in 1 M H2SO4 electrolyte. Cyclic voltammetry (CV) analysis was performed to observe the capacitive performance and redox behavior of the composites. The ion transfer behavior and cyclic stability of the composites were investigated by electrochemical impedance spectroscopy (EIS) analysis and cyclic charge–discharge (CCD) testing, respectively. The MWCNTs/Pd/PANI composite was found to exhibit an especially high specific capacitance value of 920 F/g at scan rate of 2 mV/s.

Expanded graphite (EG) consists of a huge number of partially exfoliated graphite sheets with the thickness of most of the sheets in the nanometer range. This study analyses the effect of EG and modified EG (MEG) on the mechanical, thermal, and dynamic mechanical properties of solution styrene butadiene rubber (SSBR) with and without carbon black (CB). The surface of the EG was modified to enhance its dispersion in the SSBR matrix. In addition, oil-extended carboxylated styrene butadiene rubber (XSBR) was used as a compatibilizer to disperse MEG in the base nonpolar SSBR matrix. XSBR/MEG nanocomposites have been prepared by solution mixing. The obtained nanocomposites were incorporated into the SSBR matrix in the presence of CB by melt blending. Morphological properties of the nanocomposites revealed intercalation of MEG sheets in the SSBR matrix. Nanocomposites containing MEG in the presence of CB show improvement in mechanical, thermal, and dynamic mechanical properties. POLYM. ENG. SCI., 54:33–41, 2014. © 2013 Society of Plastics Engineers

Summary — The simple mixing of non-polar rubber and organically modified nanoclay may not lead to good dispersion of organoclay in the rubber matrix, which is due to the incompatibility between the rubber and the filler. Thus, the application of polar compatibilizer which is compatible with both the gum base and organically modified clay may help to increase the reinforcing efficiency of the organoclay. Oil extended carboxylated styrene-butadiene rubber (XSBR) was used as a compatibilizer for the dispersion of the organically modified clay (Cloisite 15A, Cloisite 20A and Cloisite 30B) in the ethylene-propylene-diene terpolymer (EPDM) matrix. The degree of dispersion of organoclays in non-polar EPDM matrix after application of polar compatibilizer as well as the influence of these organoclays on the properties of nanocomposites based on EPDM were analyzed in this study. The microstructure of the organoclay filled EPDM composites was studied by wide angle X-ray diffraction (WAXD) method and high resolution transmission electron microscopic (HR-TEM) analysis. Dynamic mechanical thermal analysis (DMTA), scanning electron microscopic (SEM) analysis, thermogravimetric analysis (TGA) and curing tests were conducted for each nanocomposite. Cloisite 30B filled EPDM composite showed best thermal, mechanical and dynamic mechanical properties compared to all other investigated nanocomposites.

As nanosized expanded graphite (EG) reveals a similar layered structure like organoclay and also it has a high expansion ratio so rubber chains can easily be intercalated into the gallery space. To improve the dispersion of EG in the rubber matrices, primarily the surface modification of the expanded graphite have been done and then the modified expanded graphite (MEG)/polar compatibilizer [epoxidized natural rubber (ENR)] master batch have been prepared by solution mixing method in the laboratory. After that the MEG/ENR master batch have been mixed with bulk natural rubber (NR) in presence and absence of carbon black (CB) in a laboratory scale open two roll mixing mill. Wide angle X-ray diffraction (WAXD) and high resolution transmission electron microscopic (HR-TEM) analysis of the nanocomposites revealed that MEG was intercalated and as well as delaminated in the NR matrix. Scanning electron microscope (SEM) images of the nanocomposites showed very rough surface than the pure NR matrix. In presence of expanded graphite the crack paths are channelized and coincide in one point suggesting the effect of plate like expanded graphite to acts as a barrier. We have got improved mechanical, thermal and dynamic mechanical properties for the MEG and MEG/CB loaded NR compounds compared to EG and EG/CB loaded NR compounds.

The study described in this paper is an analysis of the role of a compatibilizer for dispersing organically modified nanoclay in styrene butadiene rubber (SBR) and ethylene propylene rubber (EPR) matrices. The normal mixing of non-polar rubbers and organically modified nanoclay may not lead to improved distribution of the nanofiller in the rubbery matrix. Hence, a polar rubber such as epoxidized natural rubber (ENR) can be used as a compatibilizer for dispersing nanoclay in the non-polar rubber matrices. ENR–organically modified nanoclay composites (EC) were prepared by solution mixing. The nanoclay used in this study is Cloisite 20A. The obtained ENR–nanoclay composites were incorporated in SBR and EPR matrices along with carbon black. The morphological studies proved the intercalation of nanoclay platelets in ENR and further incorporation of EC in SBR and EPR matrices leads to partial exfoliation of nanoclay platelets. A curing study demonstrated faster scorch time, cure time and increased maximum torque for the compatibilized SBR and EPR nanocomposites containing a dual filler system compared to the control. Dynamic mechanical thermal analysis showed increase in storage modulus for the SBR and EPR compounds containing dual fillers compared to rubber compounds containing pure and single filler. The same compounds show substantial improvement in mechanical properties. The tensile fractured surface of the rubber compounds containing single and dual filler observed by scanning electron microscopy, (SEM) showed highly rough and irregular fracture paths, which proved the physical interaction between filler and rubber.

Summary — Layered double hydroxides (LDHs) are a class of layered inorganic materials, containing basic layers of metal hydroxides. Between these layers anions and water molecules are accommodated. Interlayer anion can be replaced by wide range of organic and inorganic anions and this key feature of LDH opens new fields of applications. In this study magnesium and aluminum based LDH was modified with linseed compounds using the regeneration method. Modified LDH samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM). XRD results indicate that anionic spacer has gone inside the gallery space, which is evident from increased interlayer spacing. FT-IR study suggests the presence of spacer moiety in modified LDH. From FE-SEM study, it was observed that the shape and texture of LDH platelets have changed (they were hexagonal and smooth before modification). Unmodified and modified LDH were applied to prepare polyurethane nanocomposites (PUR/LDH and PUR/LLDH, respectively). Nanocomposite PUR/LLDH was characterized by better mechanical and thermal properties in comparison with

The present study explored the effect of nanoclay on the properties of the ethylene–propylene–diene rubber (EPDM)/carbon black (CB) composites. The nanocomposites were prepared with 40 wt% loading of fillers, where the nanoclay percentage was kept constant at 3 wt%. As the modified nanoclay contains the polar groups and the EPDM matrix is nonpolar, a polar rubber oil extended carboxylated styrene butadiene rubber (XSBR), was used during the preparation of nanocomposites to improve the compatibility. Primarily the nanoclay was dispersed in XSBR by solution mixing followed by ultrasonication. After that EPDM-based, CB–clay hybrid nanocomposites, were prepared in a laboratory scale two roll mill. The dispersion of the different nanoclay in the EPDM matrix was observed by wide-angle X-ray diffraction (WAXD) and high resolution transmission electron microscopy. It was found that the mechanical properties of the hybrid nanocomposites were highly influenced by the dispersion and exfoliation of the nanoclays in the EPDM matrix. Thermo gravimetric analysis, scanning electron microscopy and dynamic mechanical thermal analysis was carried out for each nanocomposite. Among all the nanocomposites studied, the thermal and mechanical properties of Cloisite 30B filled EPDM/CB nanocomposite were found to be highest.

This article explores the effect of halloysite nanotubes (HNTs) and modified HNTs (M-HNTs) on the properties of immiscible blend system based on polar polyoxymethylene (POM) and nonpolar polypropylene (PP) polymers. HNTs have been modified by N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (APTMS). Modification is confirmed by Fourier transform infrared spectroscopy (FTIR), also FTIR confirms the interaction between polymer blend and HNTs/M-HNTs. Morphology of the nanocomposites are demonstrated by scanning electron microscope (SEM) and dispersion of HNTs/M-HNTs are observed by transmission electron microscope (TEM). In nanocomposites, average dispersed domain sizes reduce in the presence of HNTs/M-HNTs but significant reduction has been observed in the case of M-HNT-filled nanocomposites rather than unmodified HNT-filled nanocomposites. The M-HNT acts as a reinforcing agent as well as bridging tool in polar–nonpolar hybrid system. Modification of HNTs brings compatibility in between the blend partners and reveals improved dynamic mechanical, thermal, and tensile properties than that of the pure blend system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39587.