Synergic effect in electrical conductivity using a combination of two fillers in PVDF hybrids composites

The objective of this work was to prepare novel conductive blends of poly(vinylidene fluoride) (PVDF) with polypyrrole (PPy) and to compare their performance with PVDF/multiwall carbon nanotube (MWCNT) composites and novel PVDF/PPy/MWCNT hybrid systems. All the compositions were prepared by melt mixing using a miniature mixer. The mixtures were characterized by Fourier transformed infrared (FTIR), wide angle X-ray diffraction (WAXD), thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM and TEM, respectively) and volume electrical resistivity. For the binary PVDF/PPy and PVDF/MWCNT systems, percolation thresholds of 10 and 0.3 wt%, respectively, were found. In the hybrid systems, however, the percolation threshold for each filler was lower than in the binary systems, but the electrical conductivities were always much higher at all concentrations than the conductivities of the binary systems. Therefore, the addition of both fillers had a synergistic effect on the hybrid system conductivity, which was attributed to its morphology: the PPy increased the homogeneity of the MWCNT distribution and decreased the available free volume for the MWCNT; as a result the MWCNT rolled around the PPy particles bridging them through the PVDF matrix, increasing the quantum tunneling effect and thus, the electrical conductivity of the system.     

Mode-I interlaminar fracture behaviour of nanoparticle modified epoxy/basalt fibre-reinforced laminates

The effect of nano-reinforcements on fracture behaviour of bulk epoxy nanocomposites and mode-I interlaminar fracture toughness of filament-wound basalt fibre-reinforced laminates was studied. Fracture energy of the bulk epoxy nanocomposites significantly increased with acrylic tri-block-copolymer addition but remained unchanged with incorporation of nanoclay. Delamination fracture toughness was not influenced by the presence of nanoparticles in the matrix. Decreasing fibre volume fraction, on the other hand, significantly improved interlaminar fracture energy. Rigid fibres in these composites constrict the stress field ahead of the crack-tip. Hence, increasing resin content enhanced composite delamination energy by increasing the capacity for matrix deformation. Interlaminar crack propagation through the composite was observed to occur mainly by interfacial failure and matrix cracking.     

A PCA Based Fault Detection Scheme for an Industrial High Pressure Polyethylene Reactor

A data‐based monitoring scheme is proposed to detect decomposition in low density polyethylene reactors by combining principal component analysis with a priori information on the heat balance equations around the reactor. During normal operating conditions, the heat balance equation should close at all times within reasonable limits. If excess heat is generated in the reactor, the heat balance closure error will exceed a user specified threshold limit to indicate the possible onset of decomposition. However, since precise information required to formulate the exact energy balance equations was not available, principal component analysis (PCA) was used as a model identification tool. Results from a number of decompositions case studies from an industrial low density polyethylene/ethylene vinyl acetate autoclave reactor indicate that the method was able to detect the onset of decomposition with reasonable lead time.

     

Protective Effect of <Emphasis Type="Italic">Zingiber officinale</Emphasis> Against Dalton’s Lymphoma Ascites Tumour by Regulating Inflammatory Mediator and Cytokines

The aim of the present investigation was to evaluate Zingiber officinale paste against Dalton’s lymphoma ascites (DLA)-induced tumours in Swiss albino mice. Experimental animals received Z. officinale paste (low dose 100 mg/kg bw and high dose 500 mg/kg bw) orally for eight alternative days. Treatment with Z. officinale paste showed significant increase in haemoglobin level and decrease in aspartate amino transferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma glutamyl transferase (γ-GT) level. Z. officinale paste reduced the inflammatory mediators and cytokine levels, such as inducible nitric oxide (iNOS), tumour necrosis factor level (TNF-α) and interleukin-1β (IL-1β). Treatment with Z. officinale paste also significantly increased the antioxidant enzyme level, such as superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH) and glutathione transferase (GST), and decreased the lipid peroxidation. Treatment also increased the vitamin C and E levels in treated animals compared with the DLA-bearing host. Histopathological studies also confirmed the protective influence of Z. officinale paste against DLA. The present study suggested that Z. officinale paste could be used as natural spice and a potent antitumour agent.     

Parallel Breakup of Polymer Drops under Simple Shear

The deformation and breakup of a single polycarbonate drop in a polyethylene matrix is studied at high temperatures under simple shear flow using a transparent Couette device. We observed “parallel breakup” where the drop breaks after being stretched into a thin sheet parallel to the flow. The breakup occurs at a viscosity ratio greater than 3.5. Deborah number and a stress ratio incorporating elastic moduli can characterize the “parallel breakup”.

Deformation and breakup of a polycarbonate drop in a polyethylene matrix.     

DC electrorheological response of polyethylene/organically modified layered silicate nanocomposites

The present work reports the electrorheological (ER) response of high‐density polyethylene (HDPE)/organically modified silicate layers nanocomposites based on four commercially available HDPE matrices. Two single‐site catalyzed bimodal resins, one single‐site catalyzed unimodal resin and one Ziegler–Natta catalyzed unimodal resin are studied. It is revealed that the distinct separation of the two modes of the bimodal HDPE resins significantly enhances the ER response. It is proposed that the slower structural relaxation modes introduced by higher molecular weight species in the bimodal HDPE matrices enhance the ER response of the nanocomposites. This is ascribed to the longer induction time for leaking current density, which is an indicator of mobility and release of immobilized cationic surfactants at the silicate layers surface induced by field exposure. It is found that the screening effect of prematurely released cationic surfactants leads to a weaker ER response in nanocomposites whose matrices have faster relaxation modes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1298–1309     

Enhancing dispersion of copper nanowires in melt‐mixed polystyrene composites

Copper nanowire (CuNWs)/polystyrene (PS) composites were prepared by melt mixing using unfunctionalized and functionalized nanowires. Alkanethiols were utilized to modify the surface of CuNWs postsynthesis and enable their dispersion in a polymer melt. Unfunctionalized nanowires decreased the electrical resistivity of PS by nine orders of magnitude with 2.0 vol % Cu, and resulted in composites with a viscoelastic behavior dominated by polymer–polymer networks indicating that electrical percolation occurred without a transition from liquid‐like to solid‐like behavior (i.e., rheological percolation). Results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), and melt rheology characterization indicated that surface modification of CuNWs contributed to the dispersion of the nanofiller in the polymer matrix. CuNWs functionalized with 1‐octanethiol and 1‐butanethiol produced rheological percolation and a gradual decrease in the electrical resistivity of the PS nanocomposites with increasing concentration of nanowires. Polymer nanocomposites with low concentrations of functionalized nanowires showed lower complex viscosities than pure PS; this was attributed to a plasticizing effect introduced by the alkanethiols. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2064–2078, 2008     

Electrically conductive carbon nanofiber/polyethylene composite: effect of melt mixing conditions

The effect of melt mixing conditions on the morphological, rheological, electrical, electromagnetic interference (EMI) shielding effectiveness (SE), and tensile properties of 7.5 vol% vapor grown carbon nanofiber (VGCNF)/polyethylene composites were investigated. 7.5 vol% VGCNF was used because such loading is required to obtain a composite with satisfactory EMI SE. The composites were compounded by melt mixing and the parts were prepared by hot‐compression molding. The dispersion and distribution of nanofibers were enhanced by increasing the mixing energy, i.e. mixing time and/or rotation speed. The influence of mixing energy on the electrical and EMI SE properties was found to be a function of rotation speed, i.e. shear stress. For composites compounded at 20 rpm, increasing the mixing energy from 70 to 2300 J/ml decreased the EMI SE from 29.5 to 23.9 dB. However, for composites prepared at 100 rpm, increasing the mixing energy from 600 to 1700 J/ml decreased the EMI SE from 25.4 to 18.6 dB. No considerable influence on the yield stress, Young's modulus, and strain at break were found for different processing conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental investigation of viscoelastic drop deformation in Newtonian matrix at high capillary number under simple shear flow

The steady state deformation of a viscoelastic drop (Boger fluid) in a Newtonian liquid at high capillary number under simple shear flow is investigated by direct visualization using a specially designed Couette apparatus which enables visualization from two perpendicular directions. Two drop deformation modes are found: (1) Mode I – drop deformation in the flow direction and (2) Mode II – drop deformation in the vorticity direction. The drop deformation mode depends on the relative strength of the elastic contribution to viscous contribution. If the elastic contribution is weak compared to the viscous contribution, the drop elongates in the flow direction via Mode I. If the elastic contribution is strong, the drop elongates in the vorticity direction via Mode II. The drop size also affects the drop deformation. At the same capillary number, bigger drops have larger deformations than smaller drops.     

Electrostatically Dissipative Polystyrene Nanocomposites containing Copper Nanowires

Summary: A scalable synthesis of copper nanowires by alternating current electrodeposition into porous aluminium oxide was used to produce multigram quantities of 16 nm diameter by >2 µm long nanowires. Polystyrene nanocomposites were prepared by solution processing. The composites containing unpassivated nanowires were non‐uniformly dispersed and showed electrical percolation at ≈2 vol.‐% Cu loading, while the composites containing HSC₁₈H₃₇‐passivated nanowires were uniformly dispersed, but remained resistive up to at least 10 vol.‐% Cu loading.

Copper nanowires prepared by alternating current electrodeposition into porous aluminium oxide templates.