توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱The effect of linear low density polyethylene (LLDPE) molecular weight on the property of microporous membrane formation via thermally induced phase separation
اطلاعات انتشار: کنفرانس بین المللی فرآورش پلیمرها، سال
تعداد صفحات: ۴
Polymeric membranes have been developed for a variety of industrial applications. Each application imposes specific requirements on the membrane material and membrane structure. In this work microporous linear low density polyethylene (LLDPE) has been prepared via thermally induced phase separation. A homogeneous solution was prepared by melt–blending of two different types of LLDPEs with liquid paraffin. The effect of melt flow index of LLDPE which is attributed to polymer molecular weight, on the porosity and mechanical strength of porous structure was investigated. To the best of our knowledge, this is the first report about the effect of LLDPE molecular weight on membrane porosity in membrane formation via phase separation method. In the specific concentrations of polymers to diluents ratio, increasing the MFI, led to the decrease of mechanical strength and increase of porosity. The results of porosity measurements and tensile analysis showed that LLDPE with MFI=2(LLDPE 220) has bigger pores than LLDPE with MFI=0.9(LLDPE 209). Droplet growth rate depends on the matrix phase viscosity. High MFI, means low molecular weight was caused to low viscosity. Low viscosity in LLDPE 220 system could allow a faster droplet growth than the LLDPE 209 system. As a consequence, lower viscosity contributes to the LLDPE 220 sample having larger pores than the LLDPE 209 sample.<\div>

۲Fabrication of melt blended HDPE\EVA microporous flat sheet membranes via TIPS method
اطلاعات انتشار: کنفرانس بین المللی فرآورش پلیمرها، سال
تعداد صفحات: ۴
Polyethylene has many desirable properties including appropriate thermal and physicochemical stabilities. However, microporous PE membranes suffer from poor wettability and biocompatibility, which limit their potential application in aqueous solution separation and biomedical purposes. In this work, blending method was used to modify some un favorite properties such as hydrophilicity and anti–fouling of PE microporous membranes. Hydrophilic microporous flat sheet membranes were prepared using melt blended high density polyethylene (HDPE) and ethylene vinyl acetate (EVA) via thermally induced phase separation (TIPS) method. PE and EVA were used as polymeric mixture and paraffin oil was used as diluent. Homogeneous polymer–diluent samples were prepared at 220° C and were cast over pre–heated flat glass plate to fabricate flat sheet polymeric microporous membranes. Pure PE microporous membranes were also fabricated as a reference sample. Fabricated microporous membranes were characterized in terms of water permeability and mechanical property (elongation at break). Obtained results with melt blended polymeric microporous membranes were compared with pure high density poly ethylene membranes. In comparison with pure HDPE membrane, HDPE\EVA blend membranes exhibit higher water permeation as well as higher mechanical strength. Since increasing of the permeability would result in lower mechanical strength and vice versa in common membrane operational trade–off curve, the obtained results were a kind of hope giving findings to improve the hydrophilic properties of PE microporous membrane and mechanical strength, simultaneously. These results indicated that melt blended HDPE–EVA should be a novel candidate for the preparation of hydrophilic HDPE microporous membranes via TIPS method.<\div>

۳A novel hydrophilized blended HDPE\EVA microporous flat sheet membranes via thermally induced phase separation (TIPS) method
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۷
In this work, hydrophilic microporous flat sheet membranes were prepared using binary blended of high density polyethylene (HDPE) and ethylene vinyl acetate (EVA) via thermally induced phase separation (TIPS). Polyethylene and ethylene vinyl acetate were used as polymeric mixture and paraffin oil was used as diluent. Homogeneous polymer–diluent samples were prepared in three different ratios of EVA to HDPE, while the total polymer–diluent ratio was kept constant. The hot blended polymeric mixtures were cast over pre–heated flat glass at 180oC to fabricate flat plate polymeric membranes. The cast polymeric solution immerseed in water bath contaning water at 60oC. The fabricated HDPE\EVA blended membranes showed that with increasing the EVA ratio to HDPE, the water permeation as well as mechanical strength considerably increased.<\div>

۴Effect of cooling bath on LLDPE microporous membrane structure in thermally induced phase separation
نویسنده(ها): ، ، ،
اطلاعات انتشار: هفتمین کنگره ملی مهندسی شیمی، سال
تعداد صفحات: ۶
Thermally induced phase separation (TIPS) is versatile method for making microporous membranes. The purpose of this work is to investigate the coolingbath temperature and type effects on the membrane structure prepared via TIPS method. The morphology of the resulting membrane shows a typical bicontinuous structure. When quenching into water at different temperatures, a larger pore size was obtained at higher temperature. Pore sizes are about 0.7 μm, 1.2 μm, and 2.2 μm for the water cooling bath with 273K, 303K and 333K. Porosity and tensile tests confirm these results. When the composition of the coagulation bath is similar with the diluents, the chemical potential difference of diluents would be declinedand the concentration of diluent in polymer lean phase would be kept constant in stagnant condition which leads the droplets to grow and the pore size of the systemwill be larger. However in water cooling bath, the concentration of diluent in polymer lean phase decreased rapidly and pore size growth is decelerated which result is lower porosity<\div>

۵Central Composite Experimental Design Applied to Fabrication of LLDPE Microporous Membrane via Thermally Induced Phase Separation (TIPS) Method
نویسنده(ها): ،
اطلاعات انتشار: Journal of Textiles and Polymers، اول،شماره۲، JUN ۲۰۱۳، سال
تعداد صفحات: ۶
The aim of this study was to apply experimental design in determining the order of magnitude as well as the intersectional interactions between various parameters affecting the microstructure of fabricated polyethylene membranes via thermally induced phase separation method. In this study, among various parameters, the polymer concentration, cooling bath temperature and film thickness were selected as the most effective variables on the structure of membranes. The analysis variance results showed polymer concentration and cooling bath temperature were identically significant. Film thickness effect, however, showed less importance than other parameters. Surface response plots showed that lower polymer concentration and film thickness and higher cooling bath temperature would result in higher porosity. The results of analysis of variance showed that the interactions among individual parameters are significant. However, with an increase in the cooling bath temperature and polymer concentration, the effect of film thickness on the porosity would be negligible.
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