Surface modification of bagasse fibers by silane coupling agents through microwave oven and its effects on physical,mechanical, and rheological properties of PP bagasse fiber composite

Polypropylene/bagasse fiber composites were prepared by compounding polypropylene (PP) with bagasse fibers as reinforcing filler. Surfaces of fibers were modified through the use of silane coupling agents (Vinyltrimethoxysilane and γ‐Glycidoxypropyltrimethoxysilane). The fiber coating was performed by mixing of silane with fibers and cured through microwave oven in presence of catalyst. It was found that modification of surface fiber will change the physical, mechanical, morphological, and rheological properties of composite. It was observed from scanning electron microscopy that fiber adhesion to matrix has been improved and so as dispersion. Addition of fibers increases the melt viscosity in unmodified fibers but reduced the melt viscosity for modified fibers and even the viscosity is lower at higher loading compared with unmodified fibers. The tensile strength and tensile modulus increased in modified fibers compared with the unmodified on the same loading, but elongation at break decreased. The effect of coupling agent on properties of filled PP depend on the content of coupling agents and optimum amount was achieve through measurement of water absorption. Two types of coupling agents were used, one as A‐171 [CH₂CHSi (OCH₃)₃] and second one as A‐187 [CH₂OCHCH₂O (CH₂)₃Si(OCH₃)], the first one shows better adhesion to the fibers and improvements in mechanical properties are much better compared with the second one. POLYM. COMPOS., 28:713–721, 2007. © 2007 Society of Plastics Engineers     

Investigation of a flame holder geometry effect on flame structure in non-premixed combustion

In this paper the effect of flame holder geometry on flame structure is studied. The obtained numerical results using realizable k-? and β-PDF models show a good agreement with experimental data. The results show that increasing in flame holder length decreases flame length and increases flame temperature. Additionally, it is observed that flame lengths decrease by increasing in flame holder radius and increase for larger radii. Furthermore in various radii, the flame temperature is higher for smaller flame lengths. It was found that behavior of flame structure is mainly affected by the mass flow rate of hot gases that come near the reactant by the recirculation zone.     

Fracture behavior of glass bead-filled poly(oxymethylene) injection moldings

The mechanical properties of glass bead filled poly(oxymethylene) were investigated as a function of glass bead content and glass bead diameter using injection molded test pieces. Fracture toughness measurements were made using single edge-notched tension and single edge-notched bend specimens. The effect of notch orientation with respect to the mold fill direction on fracture toughness was studied using single gate and double gate moldings. Tensile strength and flexural modulus were measured using standard test pieces. It was found that; (i) fracture toughness of the filled and unfilled polymer was relatively independent of notch orientation, (ii) the presence of weldlines in the molded test pieces did not affect the fracture toughness of unfilled polymer or its composites, (iii) fracture toughness of filled polymer was always considerably lower than that of the unfilled polymer; fracture toughness decreased sharply with increasing bead concentration, (iv) fracture toughness was not a sensitive function of glass bead diameter; it decreased slightly as bead diameter increased, (v) strain energy release rate as measured under impact decreased with increasing bead concentration, (vi) tensile strength decreased linearly with increasing glass bead concentration and was inversely proportional to the square root of the bead diameter, (vii) weldlines did not affect the tensile strength of the polymer or its composities, (viii) flexural modulus increased linearly with increasing glass bead concentration according to the Einstein equation.     

The effect of weathering on durability and deformability properties of granitoid rocks

In this paper, the effects of weathering on durability and deformability properties for three different types of granitoid rocks were investigated. Five weathering grades ranging from fresh to completely weathered rocks were considered for each rock type. Deformability has been evaluated based on failure strain, tangent and secant modulus. For measuring these parameters, at least five uniaxial compressive strength tests with axial strain recorded were conducted on each weathering grade. To assess the weathering effect on the durability behavior of these rocks, a slake durability test was performed up to 40 cycles. The obtained results indicated that uniaxial compressive strength and elastic modulus dramatically decrease with increasing weathering grade. After moderately weathering grade, remarkable damage was observed in the structure and fabric of considered rocks. The results from slake durability tests showed that the slake durability index for each weathering grade has a certain changes trend which can be used in determination of the weathering grade and the long-term durability assessment. Moreover, the results showed that for evaluation of the long-term durability of the mentioned rock types, at least eight cycles should be considered, while two cycles were sufficient for estimation of weathering grade.     

Experimental Study of Parameters Affecting the Nusselt Number of Generator Rotor and Stator

In this research, the parameters affecting the Nusselt number of a generator rotor and stator under varying heat transfer rate are experimentally studied. In spite of the stator having no grooves, the rotor has four large triangular grooves. The temperature and then heat transfer rate of the rotor and stator are experimentally measured in three longitudinal and two angular positions. First, the effect of axial Reynolds number and rotor rotational speed on the rotor and stator Nusselt number with constant heat transfer rate ratio is studied. The range of the axial Reynolds number and rotational speed used is from 4000 to 30,000 and from 300 to 1500 rpm, respectively. Next, the effect of stator to rotor heat transfer rate ratio on the Nusselt number at constant axial Reynolds number and rotational speed is investigated. Three experiments were conducted at three heat transfer rate ratios (3, 5, and 8), defined as the ratio of heat transfer rate of the stator to the rotor. The results show that the higher the heat transfer rate ratio, the lower is the stator mean Nusselt number and the higher the rotor mean Nusselt number.     

Silicon nano-crystalline structures fabricated by a sequential plasma hydrogenation and annealing technique

Silicon nano-crystalline structures have been prepared from amorphous silicon films on silicon substrates using direct-current plasma hydrogenation and annealing at temperatures about 450 °C. Plasma power densities about 5.5 W/cm² were found to be suitable for the creation of nano-porous layers. The nano-porous structures produced visible luminescence at room temperature as confirmed by photoluminescence spectroscopy. The effects of plasma power and annealing temperature on the grain size and luminescence properties of these layers have been investigated by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and photoluminescence. Lowering the temperature during the hydrogenation step led to an increase in the diameter of the grains. In addition, lowering the plasma power density caused the distribution of the porous surface structures to become less widely distributed and the formation of more packed structures resulted.     

Recent Advancements in Polythiophene-Based Materials and their Biomedical,Geno Sensor and DNA Detection

In this review, the unique properties of intrinsically conducting polymer (ICP) in biomedical engineering fields are summarized. Polythiophene and its valuable derivatives are known as potent materials that can broadly be applied in biosensors, DNA, and gene delivery applications. Moreover, this material plays a basic role in curing and promoting anti-HIV drugs. Some of the thiophene’s derivatives were chosen for different experiments and investigations to study their behavior and effects while binding with different materials and establishing new compounds. Many methods were considered for electrode coating and the conversion of thiophene to different monomers to improve their functions and to use them for a new generation of novel medical usages. It is believed that polythiophenes and their derivatives can be used in the future as a substitute for many old-fashioned ways of creating chemical biosensors polymeric materials and also drugs with lower side effects yet having a more effective response. It can be noted that syncing biochemistry with biomedical engineering will lead to a new generation of science, especially one that involves high-efficiency polymers. Therefore, since polythiophene can be customized with many derivatives, some of the novel combinations are covered in this review.     

Determination of the fracture toughness of polybutylene terephthalate (PBT) film by the essential work method: Effect of specimen size and geometry

The fracture behavior of PBT films of thicknesses 0.125, 0.175, 0.275, 0.375 and 0.5 mm was investigated according to Essential Work of Fracture (EWF) method. Single edge and double edge notched specimens of varying ligament lengths were tested in tension producing load‐displacement traces that were typical of ductile failure. A linear relationship was obtained between the total specific work of fracture (W_f) and ligament length (L). This linearity was maintained as ligament length exceeded the plastic zone size or one third of sample width. It was found that while the specific essential work of fracture (W_e) was independent of thickness, the specific non‐essential work of fracture (βW_p) decreased with increasing thickness. It was found also, that work of fracture parameters were independent of the specimen width for the range of thicknesses used in the present study. Nevertheless, for a sample width of 20 mm, a lower w_e and a higher βw_p value was obtained. Good agreement was found between values of W_e obtained from SENT and those obtained from DENT specimens; the value of βw_p was consistently higher for SENT specimens.     

Sonichemical Synthesis of a New Ethylene Diamine Lead(II) Coordination Polymer as Precursor for Preparation of PbO Nano-Structure

A new nano-coordination polymer of lead(II) nitrate with the ethylenediamine (en) ligand, [Pb(en)(NO₃)₂] _n (1), has been synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The structure of 1 has been characterized by single crystal X-ray diffraction. In 1, Pb(II) ions are bridged by nitrate ligands forming linear chains, which are also further coordinated by neutral en ligands. This polymeric precursor has been used to prepare Pb(II)O nano-particles using two different methods. The prepared Pb(II)O nano-structure was characterized by scanning electron microscopy and X-ray powder diffraction.