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Gafur M.A.,Bangladesh Council of Scientific and Industrial Research | Nasrin R.,Bangladesh University of Engineering and Technology | Mina M.F.,Bangladesh University of Engineering and Technology | Bhuiyan M.A.H.,Bangladesh University of Engineering and Technology | And 2 more authors.
Polymer Degradation and Stability | Year: 2010

Talc-loaded isotactic polypropylene (iPP) composites with various contents of talc were fabricated by compression molding, following slow- and fast-cooling processes, to obtain slow-cooled samples (SCS) and fast-cooled samples (FCS), respectively. Lamellar thickness of the α-crystal of iPP in the SCS is observed to be larger than that in the FCS by X-ray diffraction study. Rolled fast-cooled samples (RFCS) were also prepared at 25 °C in order to examine the crystal growth of iPP. An epitaxial growth mechanism of the α-crystal of iPP from the talc crystal is proposed. Surface of talc-loaded FCS appears with a smaller particle size than that of talc-loaded SCS and RFCS as observed by a scanning electron microscope. Young's modulus and tangent modulus of FCS are found lower than those of SCS with the addition of talc up to 20 wt% and higher above this concentration, except microhardness which is higher in SCS at all contents of talc. From thermal studies, talc-loaded SCS and FCS are found to show higher melting temperature than the neat samples. Effect of cooling and rolling on the structures and properties of the fabricated composites are elaborately discussed. © 2010 Elsevier Ltd. All rights reserved.

Bhuiyan A.H.,Bangladesh University of Engineering and Technology | Mina M.F.,Bangladesh University of Engineering and Technology | Seema S.,Bangladesh University of Engineering and Technology | Khan M.M.,Bangladesh University of Engineering and Technology | And 2 more authors.
Journal of Polymer Research | Year: 2011

Titanium dioxide (TiO2)-filled isotactic polypropylene (iPP) composites with various contents of TiO2 were prepared by a locally fabricated extrusion molding machine. The extrudates were melt-pressed at 180 °C and produced as plane sheets of nearly equal thickness by rapid cooling. X-ray diffraction studies reveal a decrease of crystallinity and crystallites size as well as a change of α-, β- and γ-crystalline phases of the neat iPP to the α-form due to filler inclusion. Scanning electron micrographs taken on the fractured surface of the samples show increasing amount of voids with increasing filler content. Tensile strength, elongation-at-break (%) and glass transition temperature of the samples are found to decrease considerably with the increase in TiO2 content, whereas microhardness decreases slightly with the filler content. © 2010 Springer Science+Business Media B.V.

Sultana S.,University of Dhaka | Sultana S.,Bangladesh Atomic Energy Commission | Khan R.A.,Bangladesh Atomic Energy Commission | Shahruzzaman M.,University of Dhaka | And 3 more authors.
Polymer - Plastics Technology and Engineering | Year: 2010

Gelatin films were prepared from gelatin granules in aqueous medium by casting. Tensile strength, tensile modulus, elongation at break and the glass point of the gelatin films were found to be 27 MPa, 100 MPa, 4% and 51.7°C, respectively. After irradiated with gamma radiation tensile properties were increased due to denser network structure. Gelatin films were soaked in five different formulations containing 2-hydroxyethyl methacrylate (HEMA) (10-50%, by wt), methanol and photoinitiator and then irradiated under gamma radiation. Again, a series of gelatin solutions was prepared by blending varying percentages (10-50% by wt) of HEMA and then films were prepared and irradiated under gamma radiation. It was found that tensile and thermal properties of gelatin films improved significantly. © Taylor & Francis Group, LLC.

Azizar Rahman M.,Bangladesh University of Engineering and Technology | Azizar Rahman M.,Bangladesh Council of Scientific and Industrial Research | Gafur M.A.,Bangladesh University of Engineering and Technology | Akther Hossain A.K.M.,Bangladesh University of Engineering and Technology
Journal of Magnetism and Magnetic Materials | Year: 2013

Magnetoelectric composites of nominal chemical compositions (y)Mn 0.45Ni0.05Zn0.50Fe2O 4+(1-y) BaZr0.52Ti0.48O3 (where y varies from 0 to 1.0 in steps of 0.20) were prepared by the standard solid state reaction technique. The samples were sintered at various temperatures. X-ray diffraction patterns confirm the presence of the constituent phases. The initial permeability increases with increasing ferrite content and also with increasing sintering temperature. However, there is a slight decrease in initial permeability value for samples sintered above 1573 K. The dielectric dispersion is observed at lower frequencies (<103 Hz) due to interfacial polarization. The dielectric constant is almost independent at high frequencies (>104 Hz) for a particular composition because of the inability of electric dipoles to follow the fast variation of the alternating applied electric field. The ac electrical conductivity increases with increasing frequency, suggesting that the conduction is due to small polaron hopping. The increase in dielectric constant and dielectric loss corresponds to the increase in ac electric conductivity with increasing sintering temperature up to 1573 K. The magnetoelectric voltage coefficient of the composites decreases with increasing ferrite content and dc magnetic field. © 2013 Elsevier B.V. All rights reserved.

Chowdhury A.,Rajshahi University of Engineering and Technology | Alam A.,Rajshahi University of Engineering and Technology | Rashid R.B.,University of Dhaka | Al-Mansur M.A.,Bangladesh Council of Scientific and Industrial Research | And 2 more authors.
Research Journal of Medicinal Plant | Year: 2013

Corypha taliera Roxb. is a critically endangered palm species. The tree grown in the campus of the University of Dhaka, Bangladesh used to be considered as the only living species in the world. This palm tree raised some interests due to several bioactivities observed earlier and later systematic scientific studies have been undertaken to explore for its secondary metabolites. In the present study, a thorough phytochemical investigation was conducted to explore its chemical features. Initially, the unripe fruits of this palm was extracted with methanol. Later on, it was fractioned by the modified Kupchan partitioning method in to n-hexane, carbontetrachloride, chloroform and aqueous soluble fractions. The n-hexane soluble fraction was subjected to Column Chromatography (CC) over Sephadex LH-20 and the column was eluted with n-hexane-dichloromethane-methanol (2:5:1) mixtures. From the collected fractions stigmasterol (1), β-sitosterol (2), β-amyrin (3), lupeol (4) and betulinic acid (5) were isolated by Preparative Thin Layer Chromatography (PTLC). The structures of these purified compounds were established by extensive spectroscopic analysis and by comparison of their spectral data with published values as well as co-TLC with authentic samples. This is the first report of isolation of steroids and terpenoids from this plant. © 2013 Acadamic Journals Inc.

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