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Perez-Garca M.G.,University of Guadalajara | Rabelero M.,University of Guadalajara | Nuo-Donlucas S.M.,University of Guadalajara | Mendizabal E.,University of Guadalajara | And 4 more authors.
Journal of Macromolecular Science, Part A: Pure and Applied Chemistry | Year: 2012

The effect of monomer feeding rate on particle size, molar masses, glass transition and tacticity of poly(n-butyl methacrylate) (PBMA) nanoparticles synthesized by semi-continuous heterophase polymerization under monomer-starved conditions is reported. Three feed rates were examined. Highly monomer-starved conditions at the two slower addition rates were confirmed by the low amount of residual monomer throughout the reaction and by the fact that the instantaneous polymerization and feeding rates became similar at later stages of the reaction. Under these conditions, polymer particles in the nanometer range (30 to 35 nm) were obtained. Glass transition temperatures are substantially higher than those reported for commercial PBMA. Polymers tacticity was determined by 13C-NMR spectroscopy. NMR measurements confirm that the syndiotactic content of the PBMA synthesized here is larger than those of the commercial ones made by free-radical polymerization. Molar masses are much lower than those expected from termination by chain transfer to monomer, which is the typical termination mechanism in microemulsion polymerization. © 2012 Copyright Taylor and Francis Group, LLC. Source


Cruz-Delgado V.J.,Research Center en Qumica Aplicada | Espaa-Sanchez B.L.,Research Center en Qumica Aplicada | Avila-Orta C.A.,Research Center en Qumica Aplicada | Medellin-Rodriguez F.J.,Autonomous University of San Luis Potosi
Polymer Journal | Year: 2012

Unique properties of carbon nanotubes (CNTs) and Nylon-6 were combined to obtain nanocomposites through in situ polymerization. For this purpose, plasma-polymerized CNTs (CNTM) and raw CNTs were added to in situ polymerization of -caprolactam and 6-aminocapropic acid to obtain nanocomposites with 2 and 4% wt/wt of nanotubes. The morphology, phase transitions, thermal stability, dispersion and electrical conductivity were investigated for all samples. Scanning electron microscopy images showed a homogeneous dispersion of CNTs; however, dispersion is known to be better in nanocomposites with CNTM. Furthermore, the crystallization temperature increased up to 50 °C, the melting temperature increased by 20 °C and the degradation temperature increased up to 70 °C for a 10% weight loss. This behavior suggests a synergistic effect for these nanocomposites. The electrical conductivity of nanocomposites with 4% wt/wt reached a maximum of 10 4 S cm 1, suggesting a semiconductive material. Finally, the method used in this work is effective for the dispersion of CNTs, and it can be used to form nanocomposites with improved properties compared with the Nylon-6 homopolymer. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved. Source


Lira-Saldivar R.H.,Research Center en Qumica Aplicada | Hernandez A.,Research Center en Qumica Aplicada | Valdez L.A.,University Autnoma Agraria Antonio Narro | Cardenas A.,Research Center en Qumica Aplicada | And 3 more authors.
Phyton | Year: 2014

The response of cherry tomato to biofertilization with beneficial microorganisms was evaluated under shadehouse conditions. Seeds were inoculated and/or co-inoculated with Azospirillum brasilense (Az) and/or Glomus intraradices (Gi). Thereafter, seedlings of six treatments received two applications of a suspension containing Az + Gi at 15 and 30 days after the transplant, and were compared against a non-inoculated treatment which only received conventional inorganic fertilization. Seed co-inoculation with A. brasilense and G. intraradices plus two applications of Az + Gi at 15 and 30 days after transplant increased on average 6% plant height, 11% leaf area, 10.5% dry biomass and 16% yield of cherry tomato in comparison to traditional fertilization. © 2014, Fund Roulo Raggio. All rights reserved. Source


Ortiz R.A.,Research Center en Qumica Aplicada | Berlanga Duarte M.L.,Research Center en Qumica Aplicada | Gomez A.G.S.,Research Center en Qumica Aplicada | Sangermano M.,Polytechnic University of Turin | And 2 more authors.
Journal of Macromolecular Science, Part A: Pure and Applied Chemistry | Year: 2012

A pair of novel tetrafunctional spiroorthocarbonates (TETRASOC) was prepared in three stages. First, glycerol was reacted with tetraethyl orthocarbonate to form a pair of isomeric hemi spiroorthocarbonates (HEMI SOC-OLs) by monocyclization of glycerol. Formation of these two isomers depends on terminal or adjacent hydroxyl groups of glycerol reacting with the tetraethylorthocarbonate to form five and six-membered ring HEMI SOC-OLs. Second, the HEMI SOC-OLs were made to undergo another cyclization reaction by reacting with 1,3-propanediol, to form a pair of spiroorthocarbonates with one hydroxyl group (SOC-OL). In the third stage, the SOC-OL was used as nucleophylic reactant to displace the bromine atom of pentaerythritol bromide to form the final product TETRASOC. A volume change study was carried out to determine the efficiency of TETRASOC as an anti-shrinking additive finding that even at a low concentration of 7 mol%, it caused a 2.18% expansion of the polymeric volume of a bis epoxycyclohexane monomer (3,4-EP). Dynamic Mechanical Analysis (DMA) determined that the flexibilization induced by the TETRASOC in the polyether derived from 3,4-EP did not adversely impact the mechanical properties of the polymer. Copyright © Taylor & Francis Group, LLC. Source


Ramirez J.C.,Research Center en Qumica Aplicada | Trevio M.E.,Research Center en Qumica Aplicada | Herrera-Ordonez J.,Research Center en Qumica Aplicada | MacOssay J.,University of Texas-Pan American
Journal of Macromolecular Science, Part B: Physics | Year: 2012

The hydrolysis of the isocyanate (NCO) group of dimethyl meta-isopropenylbenzyl isocyanate (TMI) and colloidal stability of terpolymer latexes during storage at different pH were studied. These latexes were prepared at 40C by batch emulsion polymerizations using vinyl acetate (VAc), butyl acrylate (BA) and TMI as monomers and Aerosol A-103 as surfactant. The TMI content was calculated in the poly(VAc-BA-TMI) latex at the end of the polymerization and also monitored during storage (at room temperature). It was found that the hydrolysis of the NCO group of the TMI and the colloidal stability of the latexes were affected to different extents by the pH value. The feasibility that the other chemical groups formed by hydrolysis of the VAc and BA units in the latexes during storage could promote these phenomena is discussed. © 2012 Copyright Taylor and Francis Group, LLC. Source

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