Influence of gelatin on the properties of hydroxyapatite–polyacrylamide nanocomposite as a potential bone substitute

The controlled integration of organic and inorganic components confers superior mechanical properties onto natural bone. The present work adds to the continuing efforts of designing a natural bone-like structure. In this study, the hydroxyapatite (HAP) impregnated polymeric composites of polyacrylamide (PAM) and the same with gelatin have been synthesized by a suspension polymerization method in order to study their blood compatibility, water sorption behavior, and mechanical properties; and network parameters, such as average molecular weight between crosslinks (M _c), crosslink density (q) have been calculated. Both, HAP–PAM and PAM–gelatin–HAP composites were characterized using techniques like Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) studies, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The composites were also evaluated for their mechanical properties like compressive strength and modulus (E).     

Investigation of ionic conduction and mechanical properties of PMMA–PVdF blend-based polymer electrolytes

Polymeric gel electrolytes, based on a blend of poly(methylmethacrylate)/poly(vinylidene fluoride) (PMMA/PVdF), ethylene carbonate/propylene carbonate (EC/PC) as plasticizer and lithium perchlorate as electrolyte, have been studied as a function of the different polymeric ratios to obtain the best compromise between ionic conduction and mechanical properties of the systems involved. Ionic conductivity and the lithium self-diffusion coefficient were measured by the PFG–NMR method, which revealed a maximum of lithium mobility for the composition PMMA 60%–PVdF 40%. The Raman spectroscopic study revealed a change of the interaction between that of the lithium cations and the plasticizer molecules for different PMMA / PVdF ratios. Oscillatory rheological tests have shown better mechanical properties for the intermediate compositions of the blend.     

Ionic conductance behaviour of plasticized polymer electrolytes containing different plasticizers

The effect of different plasticizers on the properties of PEO-NH₄F polymer electrolytes has been studied. Aprotic organic solvents like propylene carbonate (PC), ethylene carbonate (EC), γ-butyrolactone (γ-BL), dimethylacetamide (DMA), dimethylformamide (DMF), diethylcarbonate (DEC) and dimethylcarbonate (DMC) having different values of donor number, dielectric constant, viscosity etc. have been used as plasticizers in the present study. The addition of plasticizer has been found to modify the conductivity of polymer electrolytes by increasing the amorphous content as well as by dissociating the ion aggregates present in polymer electrolytes at higher salt concentrations. The conductivity enhancement with different plasticizers has been found to be closely related to the donor number of the plasticizer used rather than its dielectric constant. The increase in conductivity with the addition of plasticizer has further been found to be dependent upon the level of ion association present in the electrolytes. The variation of conductivity as a function of plasticizer concentration and temperature has also been studied and maximum conductivity of ∼ 10⁻³ S /cm at room temperature has been obtained. X-ray diffraction studies show an increase of amorphous content in polymer electrolytes with the addition of plasticizers.     

The Effect of Talc on the Mechanical,Crystallization and Foaming Properties of Poly(Lactic Acid)

Poly(lactic acid) (PLA)/talc composites containing different contents of talc were prepared by melt blending. Multiple properties of the prepared composites were investigated including mechanical, rheological and crystallization as well as foaming properties. Tensile test results indicated that the mechanical properties of the composite with 3% wt. talc showed significant reinforcement and toughening effect. When the talc content reached 10%, Young's modulus of the composite was increased by 35% compared with pure PLA. The morphological results showed that the talc layers were partially delaminated and uniformly dispersed in the PLA matrix at low loading. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) results indicated that 3% wt. talc significantly increased the crystallinity of the PLA matrix. The thermogravimetric analysis (TGA) results demonstrated that the thermal stability of PLA/talc composites was enhanced as well. Moreover, talc at low loading could act as a plasticizer in the polymer flow, which was investigated by rheological tests. The batch foaming experiments revealed that 3% wt. talc loading had the most notable heterogeneous nucleation effect, with the cell size decreasing from 15.4 μm for neat PLA to 8.5 μm and the cell density increasing by 298%.     

Rheological Behavior and Interaction of Polycarbonate/Barium Sulfate Composites

The effect of microsized barium sulfate (BaSO ₄ ) on the rheological properties of Polycarbonate (PC) was investigated. The composite exhibits a reduced viscosity as compared to pure PC, indicating that use of barium sulfate is a new method to enhance the mobility of PC melts. Model calculation of this behavior was carried out according to a viscosity rheological equation. Values of model parameters were obtained and discussed. Other rheological properties were also determined, including frequency dependence of storage modulus and loss modulus. Analysis by Fourier Transform Infrared (FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS) shows that the barium sulfate fillers strongly interact with PC chains, with the type of interaction being determined.     

Highly Sensitive Fluorescence Optode Based on Polymer Inclusion Membranes for Determination of Al(III) Ions

This paper reports the use of a polymer inclusion membranes (PIMs) for direct determination of Al(III) ions in natural water by using a fluorescence based optode. The best composition of the PIMs consisted of 60 wt.% (m/m) poly (vinyl chloride) (PVC) as the base polymer, 20 wt.% (m/m) triton X-100 as an extractant, 20 wt.% (m/m) dioctyl phthalate (DOP) as plasticizer and morin as the reagent, was used in this study. The inclusion of triton X-100 was used for enhancing the sorption of Al(III) ions from liquid phase into the membrane phase, thus increasing the optode fluorescence intensity. The optimized optode was characterized by a linear calibration curve in the range from 7.41?×?10^?7 to 1.00?×?10^?4 molL^?1 of Al(III), with a detection limit of 5.19?×?10^?7 molL^?1. The response of the optode was 4 min and reproducible results were obtained for eight different membranes demonstrated good membrane stability. The optode was applied to the determination of Al(III) in natural water samples. The result obtained is comparable to atomic absorption spectrometry method.     

The different influences of the two incorporation sites of B atoms on the mechanical and thermodynamic properties of B2–ZrCu compounds: a first-principle calculation

We applied a first-principle calculation to investigate the different influences of the two incorporation sites of B atoms on the mechanical and thermodynamic properties of the near-equiatomic B2–ZrCu compound. The alloying B atoms have two possible incorporation sites, namely, octahedral interstices and Cu sites. When the concentration of B atoms is lower than 5.882 at.%, interstitial B atoms will be effective at improving the bulk modulus (B), shear modulus (G) and Young’s modulus (E) of the B2–ZrCu parent. When the concentration of the substitutional B atoms is lower than 12.5 at.%, the ductility of the parent will be strengthened. The interstitial B atoms that are located at octahedral interstices in the 〈110〉 direction can remarkably improve the Debye temperature (Θ_D) of the substituted Zr₈Cu_8?zB_z phase. The prediction for the melting point shows that the high-temperature stability is strengthened with the increase of the B concentration. Interstitial B atoms are beneficial to the minimum thermal conductivity. Finally, the electronic properties are discussed in detail to further understand the mechanical properties.     

Modeling Sorption Behavior for Ethanol/Water Mixtures in a Cross-linked Polydimethylsiloxane Membrane Using the Flory-Huggins Equation

The sorption behaviors of aqueous ethanol solutions in a polydimethylsiloxane (PDMS) membrane at 25°C were investigated in this study. The sorption isotherms for the ethanol and water binary mixtures were experimentally determined. The water uptake reached a maximum at a concentration of 80 wt% ethanol, and the partial water uptakes were even higher than the pure water solubility for 10–95 wt% ethanol solutions in the PDMS membrane, which implies the presence of a strong synergistic effect due to the ethanol copermeant. The Flory-Huggins equation was utilized to predict the sorption levels at various ethanol/water compositions. The binary Flory-Huggins interaction parameters obtained from pure solvent sorption experiments (χ_iM ) and the ethanol/water vapor liquid equilibrium data (χ ₁₂) were used in the construction of the model for predicting the partial penetrant solubilities. Using constant χ_ij parameters could not render satisfactory predictions; therefore, concentration-dependent expressions for either χ ₁₂ or χ_iM were employed to improve the prediction power. We found that constant or concentration dependent χ ₁₂ parameters had little impact on the predicted sorption, whereas the modified concentration-dependent χ_iM values greatly improved the modeling precision.     

Flow birefringence,stress optical rule and rheology of four micellar solutions with the same low shear viscosity

The flow birefringence and the rheological properties of four viscoelastic solutions having nearly the same zero shear viscosity and subjected to shear flows are investigated in the linear and non-linear domains. The surfactant used for the samples is the cetyltrimethylammonium chloride in water at the concentration of 100 mmol/l with an organic salt, the sodium salicylate. The low shear viscosity curve versus the salt concentration is non-monotonic and has two maxima separated by a minimum forming four domains in which the salt concentration is chosen. For the two solutions belonging to the inner branch, i.e. between the two maxima, a simple Maxwellian behaviour is observed and shear banding occurs as confirmed by the flow birefringence pictures. Contrary to the results of P. Fisher (1996) where the unstable flow regime is restricted to the first decreasing part of the low shear viscosity curve of a cetylpyridinium chloride solution, we show that shear banding exits in a wider domain of the salt concentration. Received 18 November 2002 / Published online: 1 April 2003 RID="a" ID="a"e-mail: Decruppe@lpli.sciences.univ-metz.fr     

Degradable Bioelastomers Prepared by a Facile Melt Polycondensation of Citric Acid and Polycaprolactone-diol

Citrate-based bioelastomers have great potentials in various biomedical fields. An appropriate selection of diol monomers could tune their properties to fulfill different application requirements. Herein, polycaprolacone diol (PCL-diol) was selected as the diol monomer to fabricate poly(caprolactone-diol citrate) (PCC) degradable bioelastomers by a one pot melt polycondensation coupled with subsequent thermosetting or post-polymerization. The catalyst-free polycondensation reaction was confirmed by Fourier transform infrared (FTIR) spectroscopy and ¹H nuclear magnetic resonance (¹HNMR) spectroscopy. The properties of the PCC elastomers were explored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), uniaxial tension tests, dynamics mechanical analysis (DMA), water-contact angle and in-vitro degradation measurements. The results showed that the molar ratio of monomers and thermosetting conditions had significant effects on the ultimate properties of the PCC elastomer. By regulating monomer ratio and thermosetting temperature the crosslink density ranged from 32?±?6?mol/m³ to 292?±?18?mol/m³, the tensile strength ranged from 171?±?28?KPa to 977?±?112?KPa, Young’s modulus ranged from 252?±?36?KPa to 1737?±?212?KPa, ultimate elongation ranged from 70?±?9% to 260?±?32%, the static-water-contact-angle was in the range of 65.4?±?1.8?～?91.0?±?0.9° and the weight loss of the PCC elastomer in phosphate buffered saline (PBS) (pH =7.4) was in the range of 30?～?100?wt% after 8?weeks degradation. An elastic and compressible, porous scaffold was fabricated via a salt leaching method, which has potential use in soft tissue grafts.     

Properties of acrylonitrile butadiene rubber (NBR)/poly(lactic acid) (PLA) blends and their foams

Abstract

Thermoplastic elastomers and their foams were prepared by blending elastomeric acrylonitrile butadiene rubber (NBR) and rigid poly(lactic acid) (PLA) with various PLA compositions ranging between 0 and 40%. The thermal and mechanical properties and the morphologies of the blends with various PLA contents were investigated through universal testing machine, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscope analysis. The rheological properties during gel formation were in situ monitored through the evolution of torque with curing time. Furthermore, the microcellular structures and physical properties of the NBR/PLA foams prepared using organic blowing agents were studied. The NBR/PLA blends showed a two-phase morphology made of a continuous NBR matrix and micron or submicron nodules and the tensile strength and modulus; also, hardness of the NBR/PLA blends increased with the increase of the added PLA content. While the foamed samples exhibited a similar cell structure and foaming ratio to that of the pure NBR, the cell formation was considerably reduced as the added PLA content exceeded 30%. We conclude that the mechanical properties of NBR thermoplastic elastomer as well as its foams can be controlled by a judicious introduction of rigid and biodegradable PLA.     

Effect of ethylene carbonate concentration on structural and electrical properties of PEO–PMMA polymer blends

Polyethylene oxide–polymethyl methacrylate (PEO–PMMA) polymer blend electrolyte system complexed with silver salt having different ethylene carbonate (EC) concentrations was prepared using solution cast technique. Complex formation and change in structural and microstructural properties have been studied by X-ray diffraction, Fourier transform infrared, and scanning electron microscopy analysis. The thermal properties of polymer films have been examined by the differential scanning calorimetry technique. Addition of plasticizer is observed to lower melting temperature. Electrical response of polymer films has been measured as a function of EC concentration and temperature using complex impedance spectroscopy. Complex impedance data are used to analyze the conductivity, permittivity, and modulus formalism to understand the conduction mechanism. The temperature dependence of electrical conductivity of polymer electrolytes shows a sudden rise at the melting temperature of PEO.     

Supreme shear modulus predicted in the monocarbide system: the Rex W1–x C alloy

The energetic, mechanical and electronic properties as a function of composition for Re_x W_1–x C alloys in the WC structure have been investigated. It has been demonstrated that the shear modulus of WC can be enhanced by alloying with a small amount of Re, to a maximum shear modulus of 311 GPa at x = 0.23. The designed alloy is energetically stable and could be expected to be a potential extremely hard transition‐metal monocarbide, which is attributed to the strong metal–metalloid interaction with modulated valence electron concentration with respect to WC. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Blending Optimization of Non-Dioctyl Phthalate Plasticized Poly (vinyl chloride) Formulations

The use of non-ortho-phthalate plasticizers in poly (vinyl chloride) (PVC) packaging materials and medical devices has been in increasing demand due to worldwide regulatory trends to minimize or eliminate phthalate plasticizers (particularly di(2-ethylhexyl)phthalate (DEHP) or dioctyl phthalate (DOP)) in the PVC industry. This study evaluates the dry-blending cycle time of a suspension grade PVC formulated with various non-DOP plasticizers, di-(2-ethylhexyl) terephthalate (DEHT or DOTP), tris (2-ethylhexyl) trimellitate (TEHTM or TOTM) and alkyl sulphonic phenyl ester (ASE), and compares them with the DOP standard. A design of experiments was also conducted to study the critical dry-blending parameters for optimization of PVC formulated with only DEHT. Effects of PVC temperature (measured during plasticizer addition to the blender), plasticizer pre-heat temperature, plasticizer and lubricant concentrations and the method of plasticizer addition on the dry-blending cycle time and peak amperage of the blender were studied. The blending cycle time is shown to be related to the resultant plasticizer efficiency and the peak amperage is related to the power consumption (the energy required to mix the PVC).     

Effects of Modifier Concentration on Structure and Viscoelastic Properties of Copolyester/Clay Nanocomposites

Abstract

Poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate)(PETG)/clay nanocomposites were prepared via melt intercalation technique. The effects of concentration of the organic modifier in the clay on the properties of the nanocomposites were studied. Three clays modified using the same alkyl ammonium modifier, but differing in modifier concentration, are used for this purpose. The nanocomposites are characterized using wide‐angle x‐ray diffraction for their structure. Dynamic mechanical analysis of these nanocomposites is also studied to investigate their viscoelastic behaviors. The x‐ray diffraction study shows an increase in the interlayer spacing of organically modified clays as compared to that of Na⁺ clay. The extent of increase in the interlayer spacing is dependent on the concentration of organic modifier used to modify the montmorillonite. The presence of well‐defined diffraction peaks and the observed increase in the interlayer spacing in the nanocomposites imply the formation of an intercalated hybrid. Dynamic mechanical properties show an increase in the storage modulus of the nanocomposite over the entire temperature range studied, as compared to the pristine polymer. Investigation of the rubbery plateau modulus confirms the reinforcing effect of organically modified clay. The observed enhancement in the modulus was greater for the clay with the lowest content of the organic modifier. These results indicate that in nanocomposites, apart from the compatibility of the organic modifier with the polymer, its concentration in the interlayer also plays a critical role in the structure development and thus in the enhancement of the properties. The nanocomposites showed reduced damping, which was governed by the modifier concentration in the clay.     

Effect of plasticizer on microstructure and electrical properties of a sodium ion conducting composite polymer electrolyte

A plasticized composite polymer electrolyte (PCPE) based on Poly (ethylene oxide) + NaI with Na₂SiO₃ as the ceramics filler and Poly (ethylene glycol) as the plasticizer has been prepared by solution cast technique. Effect of plasticization on microstrucutre and electrical properties of the materials has been investigated. The changes in the structural and microstructural properties of the material have been investigated by XRD and SEM studies. The electrical conductivity estimated using a. c. impedance spectroscopy was found to be dependent on plasticizer concentration. An enhancement in the ionic conductivity value by three times has been recorded on addition of plasticizer when compared with that of unplasticized composite polymer electrolyte. The temperature dependence of conductivity of the polymer films is found to obey the Arrhenius behavior below and above the melting temperature of PEO. The electrical transport has been found to be a thermally activated process with ions being the predominant charge carrier.     

Physicochemical Investigations of Metolose Coating Films

In the course of film coat preparation it is very important to carry out preformulation investigations. The film formed by Metolose^® SM-4 polymer containing Macrogol 2000 (polyethylene glycol) as plasticizer showed structure changes depending on the concentration of the plasticizer during storage. This could be explained by the fact that the small quantity of plasticizer can be built in among the methyl cellulose molecules more easily, while the greater amount of plasticizer forms a separate phase in the beginning and can be built in into the film structure only later. On the other hand, the water bound by the hygroscopic property of the plasticizer can further influence the properties of the film as water also serves to function as a plasticizer. The increase in the quantity of the plasticizer enhanced the tensile strength of the film: the resulting film was less breakable and easier to handle mechanically. The studied films proved to be suitable for forming a protective coat of different solid dosage forms (pellets, tablets).     

Electronic,elastic and dynamical properties of MgSe under pressure: rocksalt and iron silicide phase

The electronic, elastic and dynamical properties of MgSe in the rocksalt (B1) and iron silicide (B28) phase and the effects of pressure on these properties are investigated using first-principles method. The calculated electronic band structure indicates that the B1 phase of MgSe presents an indirect band-gap feature and the band gaps initially increase with pressure and subsequently decrease upon compression. Remarkably, an indirect-to-direct band-gap transition has been observed at the phase transition pressure. The elastic constants, bulk modulus, shear modulus, Young’s modulus, elastic anisotropy and B/G ratio of MgSe in the B1 and B28 phase at high pressure have also been investigated. The bulk modulus, shear modulus and Young’s modulus all increase monotonously with the increasing of pressure for the B1 and B28 phase of MgSe. The calculated phonon frequencies of the B1 phase at zero pressure agree well with available theoretical results. And the transverse acoustic phonon TA(X) mode of this phase completely softening to zero at 82 GPa. The phonon curves of the B28 phase under pressure have also been successfully investigated.     

LiClO4-doped plasticized chitosan and poly(ethylene glycol) blend as biodegradable polymer electrolyte for supercapacitors

Biodegradable polymer electrolyte comprising the blend of chitosan (CS) and poly(ethylene glycol) (PEG) plasticized with ethylene carbonate and propylene carbonate, as host polymer, and lithium perchlorate (LiClO₄), as a dopant, was prepared by solution casting technique. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. The variation of conductivity and dielectric properties has been investigated as a function of polymer blend ratio, plasticizer content and LiClO₄ concentration at temperature range of 298–343 K. The DSC thermograms show two broad peaks for CS/PEG blend and increased with increase in the LiClO₄ content. The maximum conductivity has been found to be 1.1?×?10^?4 S cm^?1 at room temperature for 70:30 (CS/PEG) concentration. The electric modulus of the electrolyte film exhibits a long tail feature indicative of good capacitance. The activation energy of all samples was calculated using the Arrhenius plot, and it has been found to be 0.12 to 0.38 eV. A carbon–carbon supercapacitor has been fabricated using this electrolyte, and its electrochemical characteristics and performance have been studied. The supercapacitor showed a fairly good specific capacitance of 47 F?g^?1.     

Interfacial enhancement of flexible PVC-silica composites by silane coupling agents

Enhancement of a flexible poly(vinyl chloride) (PVC)-silica composite interface was studied by the application of γ-aminopropyltrimethoxysilane on silica. Composites containing silica and silanized silica up to 25.6 phr (per hundred resin) and prepared by sol-gel technology were subjected to water and water vapor attacks similar to that in their daily use. Silane application resulted in diminishing liquid water and water vapor sorption by about 24.0% and 11.9%, respectively. Equilibrium weight gain values of the composites having different amounts of silica correlated well with a peak at 3400 cm^-1 in the IR spectra which was attributed to the stretching vibration of the O-H group of water. Liquid water and water vapor diffusivities in composites determined by the evaluation of weight gain against time data were about 0.4 x 10^-13 and 0.4 x 10^-12 m² s^-1, respectively. Inhibition of dioctyl phthalate (DOP) migration from composites by silane application was also determined as 24% using UV measurements. The most impressive merit of silane enhancement was observed as the retention of ultimate tensile strength (UTS) under wet conditions. While the untreated silica composite reduced its UTS by about 21.2%, silanized silica composite reduced its UTS by only about 13.6%, on wetting.