1. Preparation of Polyurethane Sheets Using Surfboard Manufacturing Waste and Evaluation of Their Properties to Use in Brazil’s Construction Industry

   Ricardo Luiz Barcelos_, Anelise Leal Vieira Cubas, Ana Regina Aguiar, Luciano da Silva, Alexandre de Avila Leripio, Rachel Faverzani Magnago

   Abstract: The aim objective of this study was to identify the potential of PU solid waste generation to produce and characterize a new product, namely, thermal-acoustic insulation sheets. Polyurethane sheets were prepared by incorporating different percentages (3 per cent, 5 per cent, 10 per cent, 15 per cent and 20 per cent) of the PU waste collected, with two particle sizes into the matrix. The intended use of these PU sheets was as thermal and acoustic insulation for the construction industry. The properties of the sheets were evaluated through scanning electron microscopy (SEM), mechanical compressive strength tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TA) and determination of the sound pressure level (SPL). The results showed that the properties of the sheets are influenced by the particle size and the percentage of PU incorporated. From the SEM analysis it was observed that the material was homogeneous for all samples and for both particle sizes. Regarding the mechanical properties, the compressive strength of the sheets decreased with the addition of PU, regardless of the particle size. The DSC analysis revealed a T_g at -15^oC and crystalline melting at 71^oC for all of the sheets produced. The TA results indicated a degradation onset temperature of 200^oC. The greatest reduction in the SPL was observed with the incorporation of 15 per cent of waste, regardless of the particle size. In this new approach a lower quantity of monomers can be used to obtain sheets with similar properties to those of the material with no waste incorporation. The results demonstrates that the production of PU sheets with the incorporation of residues is viable for providing a cleaner production technology with significant environmental and economic advantages.

   Keywords: Solid waste, surfboard, polyurethane, insulation sheets, construction industry.

   Pages: 103 – 120 | Full PDF Paper

2. A Computational Investigation on Gas-Phase Molecular Structures of Ethylene and Propylene Adsorbed on Pd and Pt Dimers

   Prechiel A. Barredo and Edgar W. Ignacio, Ph.D.

   Abstract: At 298 K, adsorption mode structures (π and/or di-σ) are obtained for palladium and platinum dimers (Pd₂, Pt₂ and PdPt) using density functional (B3LYP) theory calculations in the GAMESS-US suite of package. In all cases, LANL08 basis sets with ECP are used for the metal atoms, while 6-31G and 6-31G* are used for the H and C atoms respectively. Abstraction of a hydrogen atom is observed from Pt and Pt₂’s interaction with the methyl group of propylene which was not observed from Pd and Pd₂’s interaction with the same group using the method described above. The two central important aspects (adsorption and activation) in the catalysis of C=C containing compounds such as ethylene and propylene by transition-metal clusters are determined. For each case, optimized geometries with vibrational frequencies are obtained.

   Keywords: ethylene adsorption, palladium dimer, platinum dimer, propylene methyl group activation.

   Pages: 121 – 132 | Full PDF Paper

3. Characterization in Silico of the Structural Parameters of the Antifungal Agent Ketoconazole

   G.A.Araujo, E.P.Silva, R.G.Sanabio, J.A.Pinheiro, M.B. Albuquerque, R.R.Castro, M.M. Marinho, F.K.S.Lima, E.S.Marinho

   Abstract: Computational methods of molecular modeling is a useful tool for planning of bioactive compounds such as drugs. This paper aims to describe initial aspects of approach in silico of the antifungal agent ketoconazole, using the ACD / ChemSketch® and Arguslab® software as a necessary step for future studies of structural change, hoping to optimize the action of this drug. The employed methodological steps were: (1) obtaining ketoconazole structure from Chemspide repository; (2) visualization of three-dimensional structure of this drug by ChemSketch® software, with representation of the electron density map; (3) performing semiempirical calculation Arguslab® and Avogrado® software (Austin Model 1-QM-AM1) to optimize the structure, determining the potential electrostatic and Mulliken atomic charges, generation of three- dimensional maps of the electrostatic potential, calculation of orbital border and the minimum potential energy of the molecule. The optimization of ketoconazole structure proved to be feasible. From the electrostatic potential map and load distribution of Mulliken, identified the oxygen atom of the acyl termination (O₃) as a preferred site for nucleophilic reactions. Energy ketoconazole minimum potential was estimated at -139841.4989 kcal/mol The now obtained descriptors will be key objects for future studies of relationships between three-dimensional structure of the drug and its biological activity.

   Keywords: ketoconazole, semi-empirical calculation, molecular modeling.

   Pages: 133 – 142 | Full PDF Paper