Analysis of Stress Concentration Factor for Tensile Characteristics of Syntactic Foam Using Finite Element Method
Pages 21-32
Zulzamri Salleh, Md Mainul Islam and Jayantha Ananda Epaarachchi

DOI: http://dx.doi.org/10.6000/1929-5995.2017.06.01.4

Published: 06 April 2017

Abstract: This paper presented the stress concentration factor (SCF) around the half circular edge of tensile specimens made of syntactic foam using finite element software Strand7 software. The study is a preliminary effort, which investigates the effect of variations of crack geometry on the stress concentration factor on a tensile specimen subjected to a constant, uniform, uniaxial tensile load. The material property is graded for varying Young’s Modulus and Poisson’s Ratio with different composition of glass microballoons. Finally, a uniform pressure is applied at the top and the model is constrained with symmetric boundary conditions at the left and bottom. As the result, these numerical results for both SCF experimental and simulation model are compared to those obtained from analytic fracture mechanics procedures and are found to be varied. In addition, the SCF is sensitive to the modulus of elasticity, particularly for lower composition weight percentage (wt.%), while it is also varied with the different weight percentage (wt.%) of glass microballoons, which is led by 2 wt.% specimen.

Computer Integrated Manufacturing of Polyurethane Foams Steered by Measured and Calculated Data in Comparison
Pages 118-136
Heinrich Horacek

DOI: http://dx.doi.org/10.6000/1929-5995.2016.05.04.1

Published: 23 January 2017

Abstract: Polyurethane foams were manufactured under continuous measurements of isocyanate content, temperature, expansion and viscosity. Parallel model calculations were executed based on the driving force of 50kJ/mole heat of reaction of the energy rich isocyanate group and on thermodynamic balances of weight and heat of formation as well as on a kinetic model using a first order reaction for the isocyanate consumption and a relation for the viscosity dependent on conversion and on a viscosity constant. The agreement between continuous measured and calculated data was satisfying. The parameters isocyanate content, temperature, expansion and viscosity controlled and steered the variables of the production plant, like dosage of components, temperature and conveyer speed. The kinetic model was also valid for polyurethane foams with additives, which did not react with components of foam, like flame retardants or pigments. The thermodynamic balances of weight and heat predicted residues and consumed heats by degradation under fire, which correlated with those measured by TGA and DSC. The target was to establish computer integrated manufacturing without continuous measurements but by mere model calculation. This was possible with the knowledge of the first order velocity constant and the viscosity constant.

Formation Features of Hybrid Magnetic Materials Based on Polyphenoxazine and Magnetite Nanoparticles
Pages 137-148
S.Zh. Ozkan, G.P. Karpacheva, E.L. Dzidziguri, P.A. Chernavskii, G.N. Bondarenko and G.V. Pankina

DOI: http://dx.doi.org/10.6000/1929-5995.2016.05.04.2

Published: 23 January 2017

Abstract: Hybrid metal-polymer nanocomposite materials based on polyphenoxazine (PPhOA) and Fe₃O₄ nanoparticles were obtained for the first time via two methods: in situ oxidative polymerization of phenoxazine (PhOA) in an aqueous solution of isopropyl alcohol with nanoparticles of Fe₃O₄ being present; chemical transformations of PPhOA subjected to IR heating at 400–450 °С in the presence of FeCl₃·6H₂O in an inert atmosphere. Obtained hybrid Fe₃O₄/PPhOA nanomaterials were characterized by means of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy(TEM), atomic absorption spectrometry (ААS), elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), as well as by vibrating sample magnetometry. The chemical structure, phase composition, magnetic and thermal properties of obtained nanocomposites were investigated in relation to the synthesis conditions.

Optimizing Activators Regenerated by Electron Transfer for Atom Transfer Radical Polymerization of Methyl Methacrylate Initiated by Ethyl 2-bromopropionate
Pages 149-157
Mingsen Chen, Hongwang Zhou, Xiaofang Li, Li Zhou and Faai Zhang

DOI: http://dx.doi.org/10.6000/1929-5995.2016.05.04.3

Published: 23 January 2017

Abstract: In this study, we used ethyl 2-bromopropionate (EBrP) as an initiator of activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) of methyl methacrylate (MMA). We investigated in detail the effect on polymerization of different kinds of reducing agents and ligands, the amounts of the reducing agent and catalyst, and reaction temperature. We determined the molecular weight and dispersity of the polymers by gel permeation chromatography (GPC). The results reveal glucose to be the best reducing agent for this system. The monomer conversion increased with increases in the reaction temperature and in the feeding amounts of the reducing agent and catalyst. The optimum amount of the reducing agent and minimal amount of catalyst required depend on the particular system. For example, we polymerized MMA with 200 ppm of catalyst and 15-fold of glucose/CuCl₂ resulting in a PMMA with high M_n (M_n,GPC = 48 700, M_n,theo = 48 500) and low dispersity (1.27). The first-order kinetics show that the molecular weights increased linearly with the monomer conversion and are consistent with the theoretical values, the chain extension reaction and end group analysis results also demonstrate that the characteristics of polymerization process belong to a typical “living”/controlled radical polymerization. Moreover, ¹H-NMR analysis results indicate the stereoregularity of the polymer is given priority over syndiotactic architecture and the effect of the type of ligand on the stereoregularity is very slight.

Use of High-Range Water Reducer to Mitigate the Detrimental Effect of Recycled Acrylic-Based Polymers on Concrete Performance
Pages 158-168
Joseph Jean Assaad

DOI: http://dx.doi.org/10.6000/1929-5995.2016.05.04.4

Published: 23 January 2017

Abstract: The incorporation of recycled polymers from waste latex paints (WLPs) in concrete manufacturing is very limited. In fact, this practice cannot be formally implemented without thorough assessment of the various implications that could result from WLP additions on concrete properties. This paper seeks to provide better understanding on effect of WLP constituents and substitution rates on concrete fresh and mechanical properties. It also examines the effect of incorporating naphthalene-based high-range water reducer (HRWR) to mitigate the detrimental effects associated with such additions. Tested WLPs were not randomly collected from waste collection sites; rather produced to assure full traceability of composition and then stored for around 1-year to expire. Test results have shown that workability, setting time, and hardened properties of concrete are directly affected by the polymer latex type and content including the pigment/extender ratio. The use of HRWR is efficient to control work ability and its loss over time when WLPs are disposed in concrete at relatively high rate of 10% of mixing water. The incorporation of HRWR should be coupled with certain reduction in free water to control the drop in compressive strength and bond to embedded steel bars.