Iranian polymer journal
Volume:16 Issue: 8, 2007

Moulded grating is a lattice of connected beams that has wide applications in various industries. In the case of structural applications, deflection control is usually expected to be the limiting factor in design rather than strength control. Thus, this research is mainly focused on an analytical solution to predict the loaddeflection behaviour of a moulded grating under concentrated and uniform loads. The general differential equation of an orthotropic plate is expanded by considering a moulded grating as several beams with bending and torsional rigidities. Afterward, the developed model is validated by a finite element modelling technique as well as by the experimental data provided by Strongwell Company. Results showed that the data obtained by the proposed analytical model and those of the finite element method and experimental are in good agreement. Thus, using a developed closed form solution method in this article, the deflection of a grid with any arbitrary dimensions and meshes can be calculated properly.

The present study describes the drug release behaviour of vitamin B2 loaded superporous floating hydrogels which was prepared through rapid copolymerization of acrylamide and acrylic acid in the presence of model drug using NaHCO3 as porogen and tetraethylmethylene diamine as catalyst. The gels prepared with 0.12 and 0.58 mM of cross-linker remained buoyant for nearly 96 h, but showed different release behaviours. The cross-linked sample with 0.12 mM released almost 100% drug within two hours in a simulating gastric fluid of pH 1.2, while the sample with 0.58 mM of cross-linker demonstrated a slower release which was extended over a period of 30 h. The mesh sizes of two samples were found to be 23.25Å and 20.11Å as determined from swelling measurements. The asymptotic nature of the release profile indicated a first-order kinetics, which was also confirmed by the regression analysis. The gels offer their strong candidature for prolonged gastric delivery of drugs for the treatment of gastric disorders.

In the present study, psyllium mucilage which is obtained from Plantago ovata has been modified through graft copolymerization and network formation using acrylic acid (AA) as the monomer, potassium persulphate (KPS) as an initiator, and hexamethylene tetramine (HMTA) as a cross-linker. Initially, various reaction parameters such as initiator concentration, amount of solvent, reaction time, reaction temperature, pH, monomer concentration, and cross-linker concentration were optimized. The optimized cross-linked [Psy-g-poly(AA)] hydrogel was then investigated for its efficiency in removing water from petrol/water, diesel/water, kerosene/water and petroleum ether/water emulsions. The study was carried-out at various time, temperature, pH, and NaCl concentration of the swelling media. The cross-linked Psy-g-poly(AA) hydrogel has been found to act as a smart polymer. It has been found that the functionalized polymer can absorb water up to 6710% and it is effective in selective removal of water from different oil/water emulsions. The polymer has a high swelling affinity in aqueous medium, though it fails to swell in ethanol, acetone, iso-propanol, petrol, diesel, kerosene, and petroleum ether. Moreover, the polymer is pH-sensitive and can act as a suitable candidate for colon-specific drug delivery systems.

This paper describes the development of a three-dimensional finite element model for the modelling of a 155/65R13 steel-belted tyre under inflation pressure, vertical static (footprint) load, and steady state rolling. The model was created for the ABAQUS/standard code and used to carry out a series of parametric studies. The main purpose was to examine the effect of some structural and operational parameters including type of body and cap plies cords, cord belt angle, and friction coefficient between tyre and road on the mechanical behaviour of the tyre under both static and rolling conditions. It is shown that the belt angle is the most important constructional variable among the selected parameters that affect the tyre behaviour, significantly. The changes of friction coefficient have had great influence on tyre variables at contact zone, e.g., pressure field and relative shear between the tread elements and road as well. The accuracy and reliability of the results obtained in this simulation were also confirmed by comparing two deformational characteristics of the tyre (static deflection and free rolling perimeter) with those of two commercial tyres.

In this work, the boron (B) modification of MCM-41-supported dMMAO/zirconocene catalysts showed a promising increase (almost twice) in catalytic activity in ethylene/ 1-octene copolymerization. The enhanced activity can be attributed to the decreased interaction between the support and dMMAO with boron modification as was proved by TGA. It was proposed that boron acted as a spacer anchoring the support and dMMAO. However, at high boron loading (ca. 5 wt%), the activity slightly decreased due to the migration of dMMAO into boron layer resulting in less surface concentration of [Al]dMMAO which was measured by XPS. The inhibition of chain transfer reaction during polymerization apparently occurred upon the boron modification providing higher MW polymer. It was also suggested that boron modification has rendered more uniform catalytic sites which was leading to narrower MWD of the polymer observed. Based on 13CNMR, boron modification did not affect the microstructure of copolymers obtained. However, the insertion of 1-octene increased with boron modification probably due to decreased steric hindrance of the MCM-41 support.

The present review gives a comprehensive account on the synthesis of block copolymers via redox initiating systems. Redox polymerization systems for the synthesis of block copolymers have been evaluated. The mechanism of initiation by a redox process is a method which is used to obtain block copolymers by various transition metals, such as Ce(IV), Mn(IIII), Cu(II), and Fe(III). Redox polymerization has found wide applications in initiating polymerization reactions and has been specifically of industrial importance. As it follows from the ‘contents’, in addition to the above mentioned metals, other redox polymerization systems such as hydrogen peroxide and vanadium are described as well.