Bulk Swelling Research Articles

Analysis of immersed silica optical microfiber knot resonator and its application as a moisture sensor.

An embedded silica optical microfiber knot resonator humidity sensor is presented. As silica has a poor response to environmental humidity changes, a surrounding layer of Nafion is used as a transducer. Spectral characterization and also a procedure to determine the coupling and total loss coefficients are presented. Sensitivity as high as (0.29±0.01) nm/% relative humidity has been noticed. Possible issues that emerge from the use of Nafion such as bulk swelling, refractive index hysteresis, as well as a saturation process, are discussed.

Fire-resistance, physical, and mechanical characterization of particleboard containing Oceanic Posidonia waste

In this work, particleboards manufactured with Oceanic Posidonia waste and bonded with cement are investigated. The particleboards are made with 3/1.5/0.5 parts of cement per part of Posidonia waste. The physical properties of bulk density, swelling, surface absorption, and dimensional changes due to relative humidity as well as the mechanical properties of modulus of elasticity, bending strength, surface soundness, perpendicular tensile strength and impact resistance are studied. In terms of the above properties, the best results were obtained for particleboards with high cement content and when the waste “leaves” are treated (crushed) before board fabrication, due to internal changes to the board structure under these conditions. Based on the results of fire tests, the particleboard is non-flammable without any fire-resistant treatment.

Mechanism of disintegrant action of polacrilin potassium: Swelling or wicking?

The effect of particle size, pH of medium, and presence of lubricant on the swelling behaviour, water uptake properties and disintegrant performance of polacrilin potassium was examined. Particle size did not affect the bulk swelling of disintegrant particles when measured as settling volume, but increased the water uptake and decreased the disintegration time of tablets containing this disintegrant. An increase in the pH of the medium from acidic to neutral increased the bulk swelling of the particles, whereas it decreased water uptake and disintegrant performance. Addition of lubricant had no effect on settling volume, but decreased the water uptake rate and the disintegrant performance significantly. It is concluded that wicking, i.e. capillary action, rather than swelling, is the major factor that contributes to the disintegration behaviour of polacrilin potassium.

Development of natural gum based fast disintegrating tablets of glipizide

Dysphagia and risk of choking are leading causes of patient non‐compliance in the self‐administration of conventional tablets.To overcome these limitations of conventional tablets fast‐disintegrating tablets were developed, using natural gums.Natural gums were evaluated for bulk swelling capacity. Powder mix containing natural gums and glipizide was evaluated for water sorption, swelling index and capillary action. For faster onset and immediate hypoglycemic action, the fast disintegrating tablets were prepared with various types of natural gums using the direct compression technique. Formulations containing guar gum disintegrated within a minute and fulfilled the official requirements for dispersible tablets. As the amount of guar gum increased, the friability increased and hardness decreased, resulting in a shorter wetting and disintegration time. Gum acacia and gum tragacanth did the opposite.The glipizide‐loaded fast disintegrating tablet prepared with 18 mg of guar gum gave a friability of 0.46 ± 0.02%, content uniformity of 99.34 ± 0.82%, drug content of 99.15 ± 1.16%, wetting time of 39.0 ± 1.04 sec, hardness of 5.70 ± 1.41 Kg and disintegration time less than 30 sec, suggesting that it was a practical product with a good tablet property. In conclusion, natural gum based patient‐friendly fast disintegrating tablets of glipizide can be successfully formulated.

Development and Long‐Term In Vivo Evaluation of a Biodegradable Urethane‐Doped Polyester Elastomer

We have recently reported upon the development of crosslinked urethane-doped polyester (CUPE) network elastomers, which was motivated by the desire to overcome the drawbacks presented by crosslinked network polyesters and biodegradable polyurethanes for soft tissue engineering applications. Although the effect of the isocyanate content and post-polymerization conditions on the material structure-property relationship was examined in detail, the ability of the diol component to modulate the material properties was only studied briefly. Herein, we present a detailed report on the development of CUPE polymers synthesized using diols 4, 6, 8, 10, or 12 methylene units in length in order to investigate what role the diol component plays on the resulting material's physical properties, and assess their long-term biological performance in vivo. An increase in the diol length was shown to affect the physical properties of the CUPE polymers primarily through lowered polymeric crosslinking densities and elevated material hydrophobicity. The use of longer chain diols resulted in CUPE polymers with increased molecular weights resulting in higher tensile strength and elasticity, while also increasing the material hydrophobicity to lower bulk swelling and prolong the polymer degradation rates. Although the number of methylene units largely affected the physical properties of CUPE, the choice of diol did not affect the overall polymer cell/tissue-compatibility both in vitro and in vivo. In conclusion, we have established the diol component as an important parameter in controlling the structure-property relationship of the polymer in addition to diisocyanate concentration and post-polymerization conditions. Expanding the family of CUPE polymers increases the choices of biodegradable elastomers for tissue engineering applications.

On the Origins of Sudden Adhesion Loss at a Critical Relative Humidity: Examination of Bulk and Interfacial Contributions

The origins for abrupt adhesion loss at a critical relative humidity (RH) for polymeric adhesives bonded to inorganic surfaces have been explored using a model poly(methyl methacrylate) (PMMA) film on glass. The interfacial and bulk water concentrations within the polymer film as a function of D 2O partial pressure were quantified using neutron reflectivity. Adhesion strength of these PMMA/SiO 2 interfaces under the same conditions was quantified using a shaft loaded blister test. A drop in adhesion strength was observed at a critical RH, and at this same RH, a discontinuity in the bulk moisture concentration occurred. The moisture concentration near the interface was higher than that in the bulk PMMA, and at the critical RH, the breadth of the interfacial water concentration distribution as a function of distance from the SiO 2/PMMA interface increased dramatically. We propose a mechanism for loss of adhesion at a critical RH based upon the interplay between bulk swelling induced stress and weakening of the interfacial bond by moisture accumulation at the PMMA/SiO 2 interface.

Enhancement of Sensing Properties of Thin Poly(Methyl Methacrylate) Films by VUV Modification

Surface modification of polymeric films by VUV light is an efficient method to tailor its prop- erties and functionality for a variety of applications. Laser irradiation at 157 nm of poly(methyl methacrylate) (PMMA) thin films deposited on SiO2 layer, demonstrates a considerable increase of surface and bulk swelling during water vapour sorption in comparison to the non irradiated film ar- eas. AFM images of surface morphology of the irradiated areas reveal that surface roughness de- pends on the irradiation conditions. Besides morphological changes, X-ray photoelectron spectros- copy (XPS) suggests chemical modification of the irradiated film areas. The enhanced surface swelling and the chemical modification increases the detection efficiency of water analyte in gas phase by many orders of magnitude. This method can be used to fabricate a polymer based sensor array and to engineer its detection efficiency.

Effect of radiation on bulk swelling of plutonium alloys

Several studies show that plutonium alloys present bulk swelling. More precisely, length (as measured by dilatometry) and lattice parameter (as measured by X-ray diffraction) increase with time and seems to reach saturation after a few months for the microscopic scale. This bulk swelling can be correlated to self-induced radiation due to the decay of the different plutonium isotopes (238Pu, 239Pu, 241Pu and 242Pu) which also induce helium that tends to forms clusters, then bubbles. Many experimental and theoretical results have already been published on this topic. The goal of this paper is to review some of the results and to propose a strategy for both experiments and modelling to try to answer some of the remaining questions regarding swelling and more generally self-irradiation defects in plutonium alloys.

Helium Nano-Bubble Evolution in Aging Metal Tritides

A continuum-scale, evolutionary model of bubble nucleation, growth and He release for aging metal tritides is described which accounts for major features of the tritide database. Bubble nucleation, modeled as self-trapping of interstitially diffusing He atoms, occurs during the first few days following tritium introduction into the metal. Bubble growth by dislocation loop punching yields good agreement between He atomic volumes and bubble pressures determined from bulk swelling and 3He NMR data. The bubble spacing distribution determined from NMR is shown to remain fixed with age, justifying the separation of nucleation and growth phases and providing a sensitive test of the growth formulation. Late in life, bubble interactions are proposed to produce cooperative stress effects, which lower the bubble pressure. Helium generated near surfaces and surface-connected porosity accounts for the low-level early helium release. Use of an average ligament stress criterion predicts an onset of inter-bubble fracture in good agreement with the He/Metal ratio observed for rapid He release. From the model, it is concluded that He retention can be controlled through control of bubble nucleation.

Hydrolysis of the Nafion® precursor studied by X-ray scattering and in-situ atomic force microscopy

AbstractThe hydrolysis of Nafion® † precursor material to a perfluorosulfonate ion exchange membrane has been studied in situ at the surface of a sample using atomic force microscopy (AFM), and in the bulk using a combination of small and wide-angle X-ray scattering. The AFM results show that there is a rapid and significant change in the surface morphology of the sample during the first 12 min after the introduction of aqueous hydroxyl ions, provided that an appropriate swelling agent is used. After this point there is little change in surface morphology, although bulk swelling of the sample continues. The wide-angle X-ray scattering results indicate a significant drop in the degree of crystallinity of fluorocarbon matrix from 14±1% to 7±1% on hydrolysis, as a result of the bulk structural reordering necessary to accommodate the formation of ionic clusters. Ionic clustering is confirmed by the appearance of a characteristic small-angle X-ray peak. However, the peak forms towards the end of the hydrolysis process, and subsequently coarsens, suggesting that the formation of ionic clusters is a slow process compared to the rate of hydrolysis. It is confirmed that an appropriate water/solvent mixture is necessary to achieve an efficient conversion of precursor to membrane. AFM images of the precursor surface, when water alone is used, show no signs of structural change.

Temperature-induced phase transition at the polymer–water interface

Temperature-induced phase transition of polymer shows the bulk swelling change in the polymer network, which may induce the change of polymer surface properties. The contact angle measurements at the polymer–water interface were performed to observe the temperature-induced phase transition at the polymer–water interface using two-liquid technique. The dispersive and nondispersive components of surface free energy of polymer were measured above or below the phase transition temperature (lower critical solution temperature). A semi-interpenetrating polymer networks composed of sodium alginate and poly( N, N-dimethylaminoethyl methacrylate-co-ethyl acrylamide) were used as a model polymer system.

The swelling behaviour of perfluorinated ionomer membranes in ethanol/water mixtures

The microscopic and bulk swelling of “Nafion ®” perfluorinated ionomer membranes in mixtures of ethanol and water was studied using small angle X-ray diffraction and optical microscopy. The microscopic swelling decreased with increasing ethanol content, in contrast to the bulk swelling which increased dramatically, reaching a maximum in a mixture containing 75% ethanol and 25% water. Uniaxially oriented membranes swollen with such an optimal mixture were found to relax back to an almost isotropic state, which could not be achieved by using water alone. The conclusion is that the ethanol plasticises the fluorocarbon matrix in Nafion, allowing the ionic material to be redistributed into smaller, more numerous clusters than in membranes swollen with water alone.

CORRELATIONS BETWEEN POWDER DEPOSITION METHODS AND GREEN COMPACT QUALITY: PART I MECHANICAL PROPERTIES OF POWDERS

ABSTRACT Influence of three different deposition methods (namely, feed shoe, funnel and rainy) on the compression response of two powders was studied using a medium pressure (< 35 MPa) flexible boundary cubical triaxial tester (CTT). The two test powders were: (I) a silicon nitride-based ceramic powder (KY 35001), and (2) a microcrystalline cellulose-based pharmaceutical powder (Avicel PH 1022), The fundamental stress-strain engineering parameters of the powders (such as bulk modulus, shear modulus, compression index and swelling index) were determined for each of the three deposition methods at different isotropic pressure values. Analysis of CTT test results showed that deposition methods significantly affected (p < 0.05) certain elastic and plastic parameters of the two powders. In case of KY 3500 powder, it was found that the shear modulus and compression index values were sensitive to deposition methods (p < 0.05). However, the bulk modulus and swelling (i.e., recovery) index values of KY 3500 were insensitive (p > 0.05) to deposition methods, In case of MCC powder, it was observed that all the four engineering parameters were sensitive to deposition methods (p < 0.05). Overall, in 11 out of 24 cases, very good correlations (R2 > 0.90) were observed between the powder's materials parameters and mean pressure of compaction for both the powders.

Synthesis, characterisation and catalytic activity of styrene–divinylbenzene copolymer (XAD‐2) bound palladium (II) complex

AbstractPolymer‐anchored Pd(II) complex catalyst was sythesised by sequential attachment of 1,2‐diaminopropane as a ligand to the chloromethylated commercially available styrene‐divinylbenzene copolymer (XAD‐2). The catalyst was characterised using techniques such as FTIR, SEM, EPR, and UV‐VIS reflectance spectroscopy. Other physicochemical properties, such as bulk density, moisture content, swelling and surface area by the BET method at low temperature by nitrogen adsorption, were also studied. The catalyst was tested for the rate of hydrogenation of cyclohexene. The influence of various factors such as temperature, concentration of catalyst, substrate, and quantity of solvent have been determined. The results are compared with the homogeneous analogue. The recycling efficiency of the catalyst was also studied.

The solvent-induced swelling of poly(ether ether ketone) by 1,1,2,2-tetrachloroethane

Exposure of amorphous poly(ether ether ketone) (PEEK) to the organic solvent 1,1,2,2-tetrachloroethane (TCE) was found to have considerable effects on the physical and spectral properties of PEEK. TCE causes significant bulk swelling, as well as inducing polymer chain crystallization. Lewis acid-base interactions between the polymer and the solvent are the likely explanation for this enhanced solvent compatibility.

Swelling and microcracking of boron carbide subjected to fast neutron irradiations

The neutron absorbing ceramic boron carbide was irradiated in the Phenix fast breeder reactor between 600 and 1500 °C. Selected pellets were observed at different magnifications using optical ceramography, scanning electron microscopy, and transmission electron microscopy. The bulk swelling was measured as a function of the burn-up and compared to a recent model based on microstructural observations. Intergranular microcracking was identified as the main source of troubles in the use of boron carbide at high fluence levels and studied in relation with our recent models.

Stimuli sensitive polymers for drug delivery systems

AbstractTemperature sensitive and electric field sensitive hydrogels were prepared for use in modulated drug release systems. Crosslinked poly(N‐isopropyl‐acrylamide) and its networks, modified with hydrophobic components by copolymerization or by interpenetrating polymer networks (IPNs) formation, were utilized as temperature sensitive hydrogels. Indomethacin (a model solute)‐release from polymer matrix and permeation through polymer membrane demonstrated “on‐off” regulation with temperature fluctuation. This was the result of polymer surface properties rather than bulk swelling, as temperature was changed past the swelling transition temperature range of the polymer. The on‐off regulation in an electric field was also obtained with a positively charged solute (Edrophonium chloride) release in distilled‐deionized water from a matrix of crosslinked poly(2‐acrylamido‐2‐methylpropanesulfonic acid‐co‐butyl methacrylate). This was attributed to the ion exchange between Edrophonium ion and protons produced at the anode. The swelling changes produced by local pH or ionic strength changes affected non‐charged solute release.

Swelling and outgassing of tritiated lithium hydride compacts

Additional lithium deuteride-tritide [Li(D, T)] compact bulk swelling and outgassing data from 77 to 273 K and 373 to 723 K is presented. A swelling maximum is seen at 425 K and a minimum at 575 K. The largest swelling is seen at 723 K. Variable-temperature experiments show that the mechanism turns on progressively as the temperature is raised to the maximum. The percent of 3He outgassed is presented and shown not to affect the bulk swelling. The forces involved in swelling are illustrated by the 270 MPa needed to restrain it at 323 K. Hardness data is also listed. The swelling at 323 and 348 K is analyzed and the slow linear region II growth is shown not to correspond to the 3He production rate. The behavior more closely fits radiation-induced creep.

Effects of chondroitinase‐ABC on proteoglycans and swelling properties of fibrocartilage in bovine flexor tendon

Fibrocartilaginous regions of bovine deep flexor tendon were treated with chondroitinase-ABC and trypsin in order to extract proteoglycans from the extracellular matrix and thereby investigate the contribution of proteoglycan and collagen organization to tissue material properties. Chondroitinase-ABC digestion of tendon specimens for 24 h resulted in extraction of 60% of tissue glycosaminoglycan and leaching of the degraded large proteoglycan from the tissue residue. The totally degraded core protein of the small dermatan sulfate proteoglycan remained with the tissue residue, indicating that it is specifically associated with the tissue residue and that this association is not dependent on the glycosaminoglycan chains. Treatment of residues with trypsin after chondroitinase-ABC digestion depleted the specimens of proteoglycan. Bulk swelling tests on enzyme-extracted specimens showed that the distinct swelling properties of the fibrocartilaginous regions of the distal flexor tendon could be partially accounted for by elevated levels of proteoglycan. Swelling tests also showed that the distinct collagen organization of this region contributes significantly to the tissue's material properties. These results suggest that the fibrocartilaginous organization and composition of the articulating layer of distal tendon are adapted for mechanical requirements unique to this site, which receives compressive and frictional loads in addition to tensile loads.

La viabilité des bétons du Québec: le rôle des granulats

The petrographic study of numerous concrete structures in Quebec has revealed the extent of postconstruction chemical reactions. Those reactions between the aggregates, which form 70% of the volume of the concrete, and the cement paste result in early deterioration and undesirable mechanical deformation of the structures. From this study, it appears that the coarse aggregates can react in three different ways: (a) by peripheral reaction, which is the case for massive granitic rocks, (b) by bulk swelling, as illustrated by the Potsdam orthoquartzite, and (c) by formation of silica gel veinules within the aggregate, as shown by some Trenton limestone. Considering these three mechanisms, it is easy to understand why certain aggregates react rapidly, that is within a few months, whereas others show signs of distress only after scores of years. Using the three rock types cited above, we have also tried to evaluate existing concrete standards and their capability to detect the most important pathologies encountered in concrete. Key words: concrete, aggregate, alkalis, disintegration, expansion, testing, durability.