Characterization of microporous ECTFE membranes exposed to different liquid media and ?-radiation and nanoparticle microfiltration through such membranes

Microporous polymeric membranes are used in a variety of applications for separations, purification as well as barrier function. A major application is for microfiltration (MF). Changes in the properties of MF membranes exposed to acids, bases and organic solvents are of interest in semiconductor processing as well as in membrane contactor applications. Microfiltration membranes used for sterilization in beverage, biotechnology and pharmaceutical industries are sterilized by gamma radiation among others. Irradiation-induced degradation in membrane properties should be known. A variety of fluoropolymer-based microporous membranes are available with varying properties. Ethylene chlorotrifluoroethylene (ECTFE) membranes are a new addition and are of potential interest. Microporous membranes of ECTFE membranes subjected to caustic soaking, organic solvent soaking and γ-irradiation were characterized extensively and compared with widely-used polyvinylidene fluoride (PVDF) membranes for selected properties. ECTFE membrane swellings by seven solvents including tri-n-octylamine (TOA) were much larger than those of nonporous ECTFE films. Scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) indicated significant defects in TOA-soaked membranes. Bubble-point-pressure (BPP) based maximum pore diameters of selected solvent-soaked ECTFE membranes are in good agreement with the pore size distribution estimated from AFM. Fourier transform infrared and Raman spectroscopies were used to study the solvent-membrane interactions: TOA introduced C-H stretching and deformation. Thermogravimetric analysis (TGA) and DSC confirmed TOA presence in membrane pores. Solvents tetrahydrofuran, toluene, acetonitrile and TOA decreased Young’s modulus by 6 to 30%. ECTFE membranes resisted plasticization by these solvents: glass transition temperature variations were limited. In TOA-treated membranes, XRD indicated more significant defects in PVDF membranes. Treatment with NaOH solutions showed no effect on contact angle and BPP. Only 3M caustic solution reduced liquid entry pressure by 13.8 kPag. ECTFE membranes showed greater hydrophobicity, stronger wetting resistance and better ability to maintain hydrophobicity vis-à-vis PVDF membranes. ECTFE membranes subjected to γ-radiation (up to 45 kGy) showed almost no effect on morphology, porosity and Young’s modulus. Slight variations were observed in BPP, melting enthalpy obtained via DSC and energy loss measured in dielectric relaxation spectroscopy. The solvent resistance of ECTFE membranes, especially to TOA, is important especially in membrane solvent extraction in the presence of diluents e.g., xylene. Many characterization techniques were employed to study solvent-treatment effects on ECTFE membranes exposed to ethanol, xylene, xylene80/TOA20 and pure TOA. Membrane-surface roughness of virgin, ethanol-soaked and TOA-soaked membranes indicated: TOA-soaked membranes were the roughest, followed by ethanol-soaked and virgin ones. Bubble-point-pressure based maximum pore diameters (dmax) of solvent-treated membranes were: dmax, TOA \u3e dmax, Xylene/TOA \u3e dmax, Xylene \u3e dmax, Ethanol \u3e dmax, Virgin. In FTIR and Raman spectra, TOA introduced extra peaks contributing to C-H stretching and deformation. Raman spectra of xylene80/TOA20-soaked membrane were a combination of those of xylene and TOA. The presence of a large amount of diluent reduces the impact of TOA on ECTFE membranes. In dead-end MF, fouling mechanisms behaved differently for virgin and TOA-soaked membranes; filtrate particle size distributions agreed well with estimated pore sizes. The values of permeance (kg/m2-s-kPa) determined from the slope of the linear plot of filtration flux vs. the applied pressure difference across the membrane, were 0.39, 0.23 and 0.03 for methanol, ethanol and 2-propanol, respectively. In cross-flow MF using silica nanoparticles suspended in 25% ethanol solution, Particle agglomerates having less than 100 nm size can pass through the membrane; some fouling was observed. The governing fouling mechanisms for tests operated using 3.8 ppm at 6.9 kPag (1 psig) and 13.8 kPag (2 psig) were pore blocking; for tests conducted using 3.8 ppm at 27.6 kPag (4 psig ) and 1.9 ppm at 6.9, 13.8 and 27.6 kPag (1, 2 and 4 psig), the mechanism was membrane resistance controlled. Less particles got embedded in membrane pores in experiments operated using suspensions with lower concentrations or higher concentrations with a higher transmembrane pressure. This is in good agreement with the values of the shear rate in the pore flow and SEM images of the membrane after MF

Batch foaming of hot melt extruded excipient/disintegrant/API pharmaceutical formulations and the study of the effects of the resulting cellular structures on API dissolution

This thesis focuses on the impact of a disintegrant included in a foamed immediate release system composed of a polymer excipient and an Active Pharmaceutical Ingredient (API). Indomethacin (INM) is used as model API; Eudragit® EPO (EPO) is used as polymer excipient; AcDiSol and Crospovidone (Cros) are used as two kinds of disintegrant. The main objectives are to gain an understanding of the resulting morphologies, as well as the impact of disintegrants on drug release from foamed polymeric matrices. In the first part of this research, the Hot Melt Extrusion (HME) process is used to compound the following pharmaceutical formulations: EPO/AcDiSol/INM and EPO/Cros/INM containing different percentages of disintegrant. Comprehensive characterization of this system carried out by Hot-stage Polarized Optical Microscopy (HPOM), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) shows that in all HME-prepared samples the API is in amorphous form in the polymer excipients, strongly suggesting that the extrudates are solid solutions of INM in EPO. In addition, the DSC results show that the disintegrant is stable in the set temperature range except for the moisture loss. Significantly, the disintegrants, as found from HPOM images, are intact after both HME and batch foaming processing. In the second part of this research, a batch foaming process is carried out on the milled hot melt extrudated formulations. Scanning Electron Microscopy (SEM) is used to characterize the resulting cellular structure. The SEM images show that the disintegrants are encaged or embedded in the polymer matrix, which indicates that the polymer and disintegrant are compatible to each other. In the third part of this research, release profiles of INM are obtained using the dissolution test with the United States Pharmacopeia (USP) Apparatus II (paddle). The concentration of API is determined through an UV absorbance calibration curve. The result strongly indicates that both disintegrants do accelerate the disintegration. In conclusion, the addition of disintegrant in the HME process formulation, which embeds it in the polymer matrix, is a valid method to increase the release rate of the resulting oral dosage extrudate

Relativistic symmetry breaking in light kaonic nuclei

As the experimental data from kaonic atoms and $K^{-}N$ scatterings imply that the $K^{-}$-nucleon interaction is strongly attractive at saturation density, there is a possibility to form $K^{-}$-nuclear bound states or kaonic nuclei. In this work, we investigate the ground-state properties of the light kaonic nuclei with the relativistic mean field theory. It is found that the strong attraction between $K^{-}$ and nucleons reshapes the scalar and vector meson fields, leading to the remarkable enhancement of the nuclear density in the interior of light kaonic nuclei and the manifest shift of the single-nucleon energy spectra and magic numbers therein. As a consequence, the pseudospin symmetry is shown to be violated together with enlarged spin-orbit splittings in these kaonic nuclei.Comment: 15 pages, 7 figure