Processing of Piezocomposites by Fused Deposition Technique

Piezoelectric ceramic/polymer composites were made by a fused deposition (FD) technique, which is a solid-freeform fabrication (or layered manufacturing) technique where three-dimensional (3-D) objects are built layer by layer from a computer-aided design (CAD) file on a computer-controlled fixtureless platform. Indirect and direct FD methods were used to fabricate lead zirconate titanate (PZT)/polymer composites. For the indirect method, a CAD file for the negative image of the final part was created. A polymer mold was made via FD using a thermoplastic filament, and composite formation was completed via a lost mold technique. In the direct FD method, a thermoplastic polymeric filament that was filled with 50–55 vol% of PZT powder was used to form a positive image of the desired structure. Three-dimensional honeycomb ("3-D honeycomb") composites and "ladder" composites with 3-3 connectivity, which were formed via the FD technique, showed excellent electromechanical properties for transducer applications. In addition, the FD technique showed the ability to form composites with controlled phase periodicity, various volume fractions, and a variety of microstructures and macrostructures that are not possible with traditional composite-forming techniques.     

ENGAGE compatibilized HDPE/EPDM blends: Modification of some industrially pertinent properties and morphology upon incorporation of Mg(OH)2 filler and electron beam crosslinked network

To observe the effect of ENGAGE (a poly‐olefin elastomer) on compatibilization of industrially important incompatible blend, high‐density polyethylene (HDPE)/ethylene‐propylene diene elastomer (EPDM), 15 wt % ENGAGE is incorporated into the system and the latter is found satisfactorily efficient as compatibilizer for the above system. To improve some industrially pertinent properties another strategies are also followed in addition, incorporation of magnesium hydroxide [Mg(OH)₂] and electron beam (EB) crosslinking into the system. The gel content was found to increase with radiation dose, EPDM content and Mg(OH)₂ dispersion. ENGAGE interestingly increases the gel content that is, promotes crosslinking. It is unique that filler dispersion and crosslinked network formation maintain the compatibility of the ternary system, which is confirmed by X‐ray diffraction, differential scanning calorimetry, mechanical properties, and scanning electron microscope. The compatibilization, Mg(OH)₂ dispersion, and EB crosslinking improve the mechanical, thermo mechanical, flame retardant properties, and phase morphology considerably. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44922.     

Flow pattern transition in gas‐liquid downflow through narrow vertical tubes

The present report studies on the flow pattern transitions during vertical air water downflow through millichannels (0.83 ≤ Eötvös no. ≤ 20.63). Four basic flow patterns namely falling film flow, slug flow, bubbly flow, and annular flow are observed in the range of experimental conditions studied and their range of existence has been noted to vary with tube diameter and phase velocities. Based on experimental observations, phenomenological models are proposed to predict the transition boundaries between adjacent patterns. These have been validated with experimental flow pattern maps from the present experiments. Thus the study formalizes procedure for developing a generalized flow pattern map for gas‐liquid downflow in narrow tubes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 792–800, 2017     

Characterizations of surfactant synthesized from Jatropha oil and its application in enhanced oil recovery

Surfactants are frequently used in chemical enhanced oil recovery (EOR) as it reduces the interfacial tension (IFT) to an ultra‐low value and also alter the wettability of oil‐wet rock, which are important mechanisms for EOR. However, most of the commercial surfactants used in chemical EOR are very expensive. In view of that an attempt has been made to synthesis an anionic surfactant from non‐edible Jatropha oil for its application in EOR. Synthesized surfactant was characterized by FTIR, NMR, dynamic light scattering, thermogravimeter analyser, FESEM, and EDX analysis. Thermal degradability study of the surfactant shows no significant loss till the conventional reservoir temperature. The ability of the surfactant for its use in chemical EOR has been tested by measuring its physicochemical properties, viz., reduction of surface tension, IFT and wettability alteration. The surfactant solution shows a surface tension value of 31.6 mN/m at its critical micelle concentration (CMC). An ultra‐low IFT of 0.0917 mN/m is obtained at CMC of surfactant solution, which is further reduced to 0.00108 mN/m at optimum salinity. The synthesized surfactant alters the oil‐wet quartz surface to water‐wet which favors enhanced recovery of oil. Flooding experiments were conducted with surfactant slugs with different concentrations. Encouraging results with additional recovery more than 25% of original oil in place above the conventional water flooding have been observed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2731–2741, 2017     

Vegetable fillers for electric stimuli responsive elastomers

Dielectric elastomer actuators (DEAs) have been studied widely in recent years for artificial muscle applications, but their implementation into production is limited due to high operating voltages required. The actuation behavior of dielectric elastomer under an applied electric field is predicted by Maxwell's pressure and thickness strain equations. According to these equations, the best electromechanical response is achieved when the relative permittivity is high and elastic modulus is low. The potential source for additives increasing the relative permittivity of rubbers can be vegetable powders that have much higher dielectric constant than common elastomers. In the present research, the dielectric and actuation properties of polyacrylate rubber (ACM) were studied after the addition of different vegetable‐based fillers such as potato starch, corn starch, garlic, and paprika. The results were compared to ACM filled with barium titanate. The compounds containing vegetable fillers showed higher relative dielectric permittivity at 1 Hz frequency than the compounds containing barium titanate due to higher interfacial polarization. The actuation studies showed that lower electric fields are required to generate certain actuation forces when the starches and garlic are used in the rubber instead of barium titanate. Therefore, the vegetable‐based fillers can be used to improve actuation performance of DEAs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45081.     

Modelling of multicomponent gas separation with asymmetric hollow fibre membranes—methane enrichment from biogas

A mathematical model for the dynamic performance of gas separation with high flux, asymmetric hollow fibre membranes was developed considering the permeate pressure build‐up inside the fibre bore and cross flow pattern with respect to the membrane skin. The solution technique provides reliable examination of pressure and concentration profiles along the permeator length (both residue/permeate streams) with minimal effort. The proposed simulation model and scheme were validated with experimental data of gas separation from literature. The model and solution technique were applied to investigate dynamic performance of several membrane module configurations for methane recovery from biogas (landfill gas or digester gas), considering biogas as a mixture of CO₂, N₂ and CH₄. Recycle ratio plays a crucial role, and optimum recycle ratio vital for the retentate recycle to permeate and permeate recycle to feed operation was found. From the concept of two recycle operations, complexities involved in the design and operation of continuous membrane column were simplified. Membrane permselectivity required for a targeted separation to produce pipeline quality natural gas by methane‐selective or nitrogen‐selective membranes was calculated. © 2012 Canadian Society for Chemical Engineering     

Dynamic tensile strength of polyurea-bonded steel/E-glass composite joints

The dynamic tensile strengths of E-glass composite/polyurea and polyurea/steel interfaces within the E-glass composite/polyurea/AL-6XN stainless steel joint were measured using a laser spallation technique. Values of 370?±?20?MPa were obtained for the polyurea/composite interface while a much higher value of 486?±?20?MPa was obtained for the steel/polyurea interface. Because of the transient nature of the stress pulse, the strain rate changes continuously as the interface stress builds up. A peak strain rate of 5?×?10⁵?s^?1 was estimated. The effect of moisture on the tensile strength of the E-glass/polyurea interface was also examined. The effect was found to be minimal, with the tensile strength stabilizing at 320?±?25?MPa after 30?days of exposure to a 90%RH, 50?°C environment. When comparing the strengths of corresponding interfaces in an epoxy-bonded joint from a previous study, it was concluded that polyurea results in a much stronger and durable joint.     

Direct stamping and capillary flow patterning of solution processable piezoelectric polyvinylidene fluoride films

It is well known that the potential applications of polyvinylidene fluoride (PVDF) mainly come from the piezoelectricity and ferroelectricity of its polar β phase. Thus, we have investigated the effect of different preparation conditions namely evaporation temperature, type of solvent and additive to enhance the β crystal structures of PVDF thin film. Subsequently, facile and direct soft lithography technique; direct stamping and capillary flow were employed to demonstrate good pattern transfer of PVDF thin films. The piezoelectricity of the microstructure was characterized using piezoresponse force microscopy (PFM) where fairly good piezoresponse was obtained without further processing procedures i.e., annealing or applied pressure/electric field. As such, our solution processable and direct patterning of PVDF techniques offer facile and promising route to produce arrays of isolated microstructures with improved piezoelectric functionality.     

The effect of partial replacement of carbon black by carbon nanotubes on the properties of natural rubber/butadiene rubber compound

The basic objective of this study is to investigate the mechanical properties of tyre tread compounds by gradual replacement of carbon black by multiwalled carbon nanotubes (MWCNTs) in a natural rubber–butadiene rubber‐based system. A rapid change in the mechanical properties is noticed even at very low concentrations of nanotubes though the total concentration of the filler is kept constant at 25 phr (parts per hundred rubber). The correlation of the bound rubber content with MWCNT loading directly supports the conclusion that MWCNTs increase the occluded rubber fraction. Transmission electron microscopy reveals a good dispersion of the MWCNT up to a certain concentration. In the presence of MWCNT, a prominent negative shift of the glass transition temperature of the compound is found. Thermal degradation behavior, aging, and swelling experiments were also carried out to understand the resulting effect of the incorporation of MWCNT in the rubber matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3153–3160, 2013