Amount Of Glass Beads Research Articles

Process optimization for reverse micellar extraction of stem bromelain with a focus on back extraction

In the current study, reverse micellar extraction (RME) for the purification of stem bromelain was successfully achieved using the sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane system. A maximum forward extraction efficiency of 58.0% was obtained at 100 mM AOT concentration, aqueous phase pH of 8.0 and 0.2 M NaCl. Back extraction studies on altering stripping phase pH and KCl concentration, addition of counter-ion and iso-propyl alcohol (IPA) and mechanical agitation with glass beads indicated that IPA addition and agitation with glass beads have significant effects on extraction efficiency. The protein extraction was higher (51.9%) in case of the IPA (10% v/v) added system during back extraction as compared to a cetyltrimethylammonium bromide (100 mM) added system (9.42%). The central composite design technique was used to optimize the back extraction conditions further. Concentration of IPA, amount of glass beads, mixing time, and agitation speed (in rpm) were the variables selected. IPA concentration of 8.5% (v/v), glass bead concentration of 0.6 (w/v), and mixing time of 45 min at 400 rpm resulted in higher back extraction efficiency of 45.6% and activity recovery of 88.8% with purification of 3.04-fold. The study indicated that mechanical agitation using glass beads could be used for destabilizing the reverse micelles and release of bromelain back into the fresh aqueous phase.

Development of a Performance Verification Test for USP Apparatus 4

To evaluate salicylic acid tablets as a candidate reference material in a Performance Verification Test (PVT) when a USP performance test for dissolution (General Chapter <711>) relies on USP Apparatus 4 (flow-through cell). We developed a dissolution procedure relying on Apparatus 4 and salicylic acid tablets. Thereafter, a designed experiment was conducted to identify operational variables that significantly affect salicylic acid dissolution in this apparatus. Four variables (size of glass beads, cell temperature, flow rate, level of deaeration) and one combination effect (deaeration/bead size) were significant for mean percent dissolved. Two variables (tablet orientation, level of deaeration) were significant for standard deviation results, but these effects were less pronounced than those for mean percent dissolved results. Three variables (analyst, tester manufacturer, amount of glass beads) had no statistically significant effects on either the mean or standard deviation of the responses. The proposed PVT is capable of probing effects of changes in several critical operational parameters of Apparatus 4. Salicylic acid tablets were shown to be a suitable reference material for the PVT. The PVT using salicylic acid tablets satisfies important aspects of a PVT.

Effect of Glass Beads and Polyurethane on the Fracture Properties of Epoxy Resin

The present work investigates the mechanical properties of conventional and hybrid composites based on epoxy resin. Diglycidyl ether of bisphenol A was used as the matrix and triethylenetetramine was used as the curing agent. Polyurethane (PUR) used was based on polyether and toluene diisocyanate. Impact strength (IS), critical stress intensity factor (Kc), tensile strength (TS) and flexural strength were evaluated as function of modifiers content. It is shown that IS is increased by approximately 120% and 200% with the addition of respectively 10 phr of glass beads (GB) or 10 phr PUR, in comparison with IS of the unmodified epoxy resin. Moreover, Kc was increased by approximately 20% with 10 phr GB and 35% with 10 phr PUR. The addition of 15 phr PUR gave compositions with 30% enhanced TS and 40% increased tensile strain at break. However, the strain at break decreased with increasing amount of GB. Hybrid composition containing 10 phr PUR and 15 phr GB exhibited the maximum tensile energy to break corresponding to 80% and 85% improvement respectively in relation to the energy at break of the virgin epoxy resin and composition with only 10 phr PUR. Infrared spectra analysis of the compositions containing PUR revealed the formation of an interpenetrating polymer network structure between the modifier and the polymer matrix

Suppressed coalescence of dispersed viscous poly(methyl methacrylate) phase in polystyrene matrix by glass beads

The effect of glass beads (GB) on morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends has been studied by scanning electron microscopy (SEM) at different shear rates and during quiescent annealing. For the viscosity ratio of PMMA to PS greater than unity, the dispersed viscous PMMA phase in the blend coalesced during the shear flow or quiescent annealing. However, the domain size of the PMMA phase decreased significantly under shear even though a small amount of GB was added. The PMMA domain size further decreased and the size distribution became narrower with increasing GB content. According to SEM images, the quiescent coalescence of the PMMA phase was effectively inhibited by adding large amounts of GB, and the breakup of PMMA domains in shear flow was greatly favored by the high local shear prevailed between GB. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 25–35, 2009

Adhesion of Streptococcus sanguinis to glass surfaces measured by isothermal microcalorimetry (IMC)

Bacterial adhesion is the first step in the development of the oral biofilm, called dental plaque. Plaque is the cause of caries, periodontal diseases, and periimplantitis. Investigations of dental plaque, including bacterial adhesion, employ various in vivo and in vitro models using microscopic methods. Microcalorimetry offers another direct approach. The model organism Streptococcus sanguinis is one of the first colonizers adhering to the saliva-coated human tooth surfaces or dental materials within minutes after tooth cleaning. TAM III thermostats, equipped with microcalorimeters, were used for isothermal microcalorimetric (IMC) measurements of heat production as a function of time, expressed by power-time (p-t) curves. Continuous measurements of heat production of growing S. sanguinis cells showed their overall metabolic activity and were highly reproducible. For the adhesion experiments the bacteria were allowed to adhere to different amounts of glass beads. Growing S. sanguinis cells produced a characteristic p-t curve with a maximum of 500 microW at 4.5 h when reaching 10(9) cells ml(-1). The same number of stationary S. sanguinis cells, suspended in PBS produced only approximately 30 microW at 0.5 h due to adhesion. But the amount of heat increased with available glass surface area, indicating that a portion of the heat of adhesion was measured. Similar results were obtained with stationary S. sanguinis cells suspended in human saliva. This study shows that microcalorimetric evaluation of initial bacterial adhesion is indeed possible and may become a rapid, reproducible screening method to study adhesion of different bacteria to different dental materials or to modified surfaces.

Increased flow property of polycarbonate by adding hollow glass beads

AbstractThe steady shear viscosity and dynamic viscoelastic properties of glass beads (GB) filled polycarbonate (PC) melts were studied at varying filler diameters and concentrations. The PC/GB composites containing small amounts of GB bore lower melt viscosity and dynamic modulus than those of pure PC at studied frequencies and shear rates, showing a “ball‐bearings” effect. For highly filled systems, the viscosity and dynamic modulus were decreased further at higher frequencies and shear rates. This ball‐bearings effect was enhanced by changing the GB from larger to smaller one. The oscillatory experiments with modified shear stress showed a stress‐dependent decrease of the viscoelastic properties, and revealed an interfacial slip mechanism, combined with the polymer chains disentanglement at melt/solid interfaces. The scaling relationship between the relative viscosity and the mean interparticle gap confirmed that the interfacial slip and polymer chains disentanglement were induced by the extremely high local shear developed in the narrow gaps between the nearby rotating spheres. POLYM. ENG. SCI., 45:1119–1131, 2005. © 2005 Society of Plastics Engineers

Morphology evolution of a liquid crystalline polymer confined by highly packed glass beads in polycarbonate

Very long and perfectly oriented fibrils of a liquid crystalline polymer (LCP) were in situ formed in capillary flows by adding large amounts of glass beads (GB) to a polycarbonate (PC)/LCP blend. Thermodynamically the different interfacial tensions between the components made GB migrate to the LCP phase. Then the high content of GB spheres produced a confined condition, so that the LCP droplets passed through the simultaneously formed micro-capillaries, followed by being stretched into fibrils and stabilized consequently.

On the application of a damped model to the falling weight impact characterization of glass beads–polystyrene composites

AbstractInstrumented falling weight impact tests were carried out to characterize the mechanical behavior of a material pattern formed by polystyrene and different amounts of glass beads. This characterization was performed at high strain rate using two different impact arrangements: the first uses high impact energy at the striker, whereas the second uses a low‐impact energy. Starting from a conservative model, a nonconservative one has been proposed for the low‐energy impact configuration as a better approach to the material behavior. In this latter model, the energy losses were quantified through the restitution coefficient. Two alternative methods for its calculation are described. The results shows good agreement between the flexural modulus and break stresses calculated in either the low‐ or the high‐energy arrangement; however, the low‐energy impact method yields more confidence results. Using the proposed model, the composites' fracture onset was determined, and also in the samples with low content of glass beads, it was possible to assess the micromechanism of failure, given the estimation for the stress to produce crazing. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1271–1284, 2004

Mechanical properties of epoxy‐based hybrid composites containing glass beads and α,ω‐oligo(butylmethacrylate)diol

AbstractA novel phase‐separating liquid rubber based on oligo(alkylmethacrylate) in combination with microglass beads was used to toughen an anhydride‐cured epoxy resin. The resulting hybrid composites, containing 5 or 10 wt % of oligomeric liquid rubber and between 10 and 60 wt % glass beads as well as composites containing corresponding amounts of glass beads but no liquid rubber, were characterized mechanically. The experimental data show that modification with glass beads results in increased stiffness and toughness compared to the neat resin but reduces tensile strength. Compared to the glass bead–filled composites, additional modification with methacrylic rubber leads to a further increase in toughness and also to an increase in strength but does not alter stiffness and glass‐transition temperature. This synergistic behavior is explained by the fact that the rubber separates preferably on the surface of the glass bead, forming a core–shell morphology during curing. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1040–1048, 2003

Liquid-Solid Separation of Photo-Catalyst Suspension Induced by Ultrasound

A method for the induction of the agglomeration of different kinds of particles by the ultrasonic irradiation in the water was studied. This method has been proven to be applicable to the separation of photo-catalyst particles from the drainage of photo-oxidation process. The catalyst particle was titanium oxide with the average diameter of 3 µm. The agglomeration was observed when the ultrasound with the frequency of 26 kHz and the power of 80 W was irradiated and a certain amount of glass beads with the diameter between 33-44 µm were added. The catalyst particles deposited on the glass beads, and then settled together with the glass beads leading to the liquid-solid separation. It was also found that the addition of the glass beads has also enhanced the agglomeration among the catalyst particles themselves.

Preparation and characterization of hydroxypropyl cellulose/silica micro-hybrids

Hydroxypropyl cellulose (HPC) was incorporated in situ with silica by the sol-gel process involving various amounts of added tetraethoxysilane (TEOS), and hybrids with nanometre-sized silica particles were prepared. To determine the effect of TEOS content on the mechanical properties of the micro-hybrids, the TEOS content in the hybrids was varied from 20 to 60%. The mechanical properties of the micro-hybrids were compared with those of HPC composites mixed with various amounts of glass beads (diameters of 20–40 μm) by solvent blending. The ultimate tensile strength of the micro-hybrid was improved from 6 to 18 MPa when the TEOS content reached 40 wt%. On the other hand, the strength of the blend composite decreased with glass-bead content. The α1- (molecular motion in a highly ordered amorphous phase), α2- (molecular motion in a random amorphous phase) and β-relaxations (relating to molecular motion of hydroxypropyl groups) were observed in the temperature dependence of the dynamic viscoelastic properties of HPC. The level of the dynamic modulus, G′, of the micro-hybrid increased with initial TEOS content. By hybridization, the α1-peak in the tan δ curve broadened and its intensity lowered as the initial TEOS content increased. The α2-peak was observed for the micro-hybrid composed of 20 wt% TEOS, but disappeared when the TEOS content exceeded 40 wt%. The β-peak was not observed in the hybrid. No drastic change was observed in the dynamic viscoelastic behaviour of the blend composite as the glass-bead content was varied. The mechanical properties of the in situ micro-hybrid were completely different from those of the blend composite. This difference was caused by the interaction between the filler and matrix. In the micro-hybrid, nanometre-sized ceramic particles may be dispersed in the HPC component, and strong interaction occurs via hydrogen bonding. In contrast, the interaction between the glass beads and HPC in the blend composite is weak.

ON THE RHEOLOGICAL BEHAVIOUR OF FILLED POLYMER MELTS†

The viscosity of polymer melts increases when adding fillers. Experiments were conducted with styrene—acrylonitrile copolymers filled with various amounts of glass beads and short glass fibres on a rotational and a capillary rheometer. Further from literature some representative equations have been compiled describing the influence of fillers on the viscosity. Applied to the experimental results it was found that the relative viscosity (R, i.e. the ratio of the viscosities of the filled and unfilled melts, shows a pronounced dependence on the shear rate ? but not on the shear stress t.

Ultimate behavior of dry and water‐swollen polymer network/glass bead composites

AbstractTensile properties of a poly(2‐hydroxyethyl methacrylate) (PHEMA) network filled with various amounts of glass beads, in the dry and the equilibrium water‐swollen states, have been studied below and above Tg. The temperature ranged from 5° C to 170° C and the volume fraction of the filler was up to 50 percent. In the glassy region it has been found that the temperature at which the transition from brittle to ductiel behavior occurs is increased by the presence of the filler. In the brittle zone the strength of the composites is decreased by the presence of the filler and can be predicted by using a finite element method; in the ductile zone, however, the strength of the composites reaches that of the unfilled polymer.In the rubbery region failure envelopes have been obtained for both dry and swollen PHEMA/glass bead composites. Using a double shift procedure all the data have been superimposed to obtain universal failure envelopes for the two different states. The dependence of the shift factors on filler content is discussed.

A methodological study of human leucocyte adhesiveness to glass beads.

A method to determine the adhesiveness of human leucocytes to glass beads was evaluated. The leucocyte adhesiveness increased by decreasing flow rates, increasing amount of glass beads, increased temperature, and decreased by increasing concentration of citrate, oxalate and EDTA. The standard error of the method was 2 per cent adhesiveness.