Modelling the Relations of Rheological Characteristics with Composition of Plaster Mortar

The rheological properties of fresh plaster mortars, with varied contents of porous fillers and polymer admixtures, have been studied. The quantities of fine limestone and expanded perlite, and dosages of methyl hydroxy ethyl cellulose and ethylene vinyl acetate were varied in the experiment. Effective viscosity (at a shear rate from 0.045 to 5.705 s−1) and the thixotropy of the mixes were determined with rotational viscometer for 18 compositions (according to the design of the experiment). Each of the 18 viscosity curves were described with the Ostwald–de-Waele equation. The Experimental–Statistical models describing the dependencies of the parameters of the rheological model and of mix thixotropy on the composition factors were built on the obtained data. ES-models have allowed the individual and synergetic effects of mix components on the rheological characteristics to be evaluated. The expanded perlite powder can increase the viscosity by two times, probably due to its pozzolanic effect increasing the content of the CSH phase during cement hydration. The thixotropy can be increased by the quantity of limestone. The computational experiments with ES-models have made it possible for the information set, without a noticeable interrelation between rheological characteristics, to be stratified into subsets, in which such interrelations differ significantly.

Thermally Stimulated Depolarisation Studies of Methyl Acrylic Acid (MAA) Doped Ethyl Cellulose (EC)

Thermally stimulated depolarisation current (TSDC) of polarised samples of methyl acrylic acid (MAA) doped ethyl cellulose (EC) films of about 25 µm thickness has been recorded as a function of temperature, electric field, heating rates and storage times. Two current maxima in positive direction and found around 60 and 110oC for doped sample with ethyl cellulose. FTIR of doped EC are represented the different phenomena of TSDC. Thermal sampling technique showed that the relaxation is distributed. Differentia thermal analysis gave a second-order transition at bout 345K because of good correlation between both thermal techniques it is concluded that the TSD peak is associated with glass transition of the polymer, and therefore it involves the motion of large parts of the polymer chains.

Electrosprayed Ethyl Cellulose Core-Shell Microcapsules for the Encapsulation of Probiotics

Electrosprayed ethyl cellulose core–shell microcapsules were produced for the encapsulation of probiotic Bifidobacterium animalis subsp. lactis (Bifido). Ethyl cellulose (ETC) was used as a shell material with different core compounds (concentrated Bifido, Bifido–maltodextrin and Bifido–glycerol). The core–shell microcapsules have an average diameter between 3 µm and 15 µm depending on the core compounds, with a distinct interface that separates the core and the shell structure. The ETC microcapsules displayed relatively low water activity (aw below 0.20) and relatively high values of viable cells (109–1011 CFU/g), as counted post-encapsulation. The effect of different core compounds on the stability of probiotics cells over time was also investigated. After four weeks at 30 °C and 40% RH the electrospray encapsulated samples containing Bifido–glycerol in the core showed a loss in viable cells of no more than 3 log loss CFU/g, while the non-encapsulated Bifido lost about 7.57 log CFU/g. Overall, these results suggest that the viability of the Bifido probiotics encapsulated within the core–shell ETC electrosprayed capsules can be extended, despite the fact that the shell matrix was prepared using solvents that typically substantially reduce their viability.

Formulation, Development and Characterization of Floating Microspheres of Selected Calcium Channel Blocker

The main aim of the present investigation is to study of formulation, development and characterization of floating mcrospheres of verapamil hydrochloride. Floating microspheres with a central hollow cavity were prepared by using a modified Quasi-emulsion diffusion technique. Weighed quantities of verapamil hydrochloride, ethyl cellulose, polyethylene oxide and hydroxy propylmethyl cellulose (HPMC K15M) were dissolved in a mixture of ethanol and dichloromethane (1:1 solvent ratio) at room temperature in a magnetic stirrer at 50 rpm for 50 min. The samples were assayed for drug content using UV spectrophotometer at 228 nm after suitable dilution. No interference was found due to the other components of floating microspheres at 228 nm. The yield was determined by weighing the microspheres and then the percentage yield was calculated with respect to the weight of the input materials, i.e., weight of verapamil and polymers used. The polymers like ethyl cellulose, eudragit L 100, polyethylene oxide and HPMC were selected for hollow microspheres preparation. These formulations contained ethyl cellulose (2%) and Polyethylene oxide (1%), HPMC K15M (1%) & eudragit L100 (1%) respectively. The encapsulation efficiency ranged between 53 ± 2.2 to 89 ± 1.9%, and was observed that the encapsulation efficiency increased with increasing amount of polymers in the hollow microspheres. The sphericity factors for all formulations were in the range of 1.01 ± 0.2 to 1.29 ± 0.6 and the sphericity values of best formulations F3, F7 and F9 were 1.05±0.2, 1.07 ± 0.1 and 1.16 ± 0.1 respectively. Quassi emulsion method used for preparation of hollow microspheres was suitable for poor water soluble drugs, because the drug was soluble in the internal organic phase.