Ulises Páramo-García

PANI/SBR composites as anticorrosive coatings for carbon steel I. Chemical, morphological and superficial characterization

Research of conducting polymer composites has opened a wide array of possibilities to get high performance organic anticorrosive coatings, minimizing the environmental and health impact involved in many current protection systems. Polyaniline (PAni) is one of most studied conducting polymer, for different reasons, among easy processing from solutions into films, reversibly controlled electrical and optical properties. However, its mechanical and adhesion properties are poor. A path to improve PAni properties is to use an elastomer as insulating polymer matrix, as styrene-butadiene rubber (SBR). In this work, a composite from doped PAni and SBR was obtained by solution casting method, the effect of the conducting polymer/elastomer ratio and the PAni doping anion on the chemical nature and morphology of PAni/SBR composites has been studied to determine the feasibility of their application as anticorrosive coatings for carbon steel. Chemical characterization, by means of infrared spectroscopy (FTIR) and RAMAN spectroscopy, was also carried out, the presence of signals attributed to doping anion was identified in composites, also formation of ion oxides such as magnetite, hematite and maghemite were identified. Morphology of composites was obtained by means of optical and scanning electron microscopy, and allows to observe the presence of agglomerates in composites.

Antimicrobial, Optical and Mechanical Properties of Chitosan–Starch Films with Natural Extracts

Natural extracts possess several kinds of antioxidants (anthocyanins, betalains, thymol, carvacrol, and resveratrol) that have also demonstrated antimicrobial properties. In order to study these properties, extracts from cranberry, blueberry, beetroot, pomegranate, oregano, pitaya, and resveratrol (from grapes) were obtained. Growth inhibition tests of mesophilic aerobes, coliforms, and fungi were conducted in films prepared from the extracts in accordance with Mexican Official Norms (NOM). Optical properties such as transparency and opacity, mechanical properties, and pH were also analyzed in these materials. The films with beetroot, cranberry, and blueberry extracts demonstrated the best antimicrobial activity against various bacteria and fungi in comparison with unmodified chitosan–starch film. This study shows that the addition of antioxidants improved the antimicrobial performance of these films. It was also found that antimicrobial properties are inherent to the films. These polymers combined with the extracts effectively inhibit or reduce microorganism growth from human and environmental contact; therefore, previous sterilization could be unnecessary in comparison with traditional plastics. The presence of extracts decreased transmittance percentages at 280 and 400 nm, as well as the transparency values, while increasing their opacity values, providing better UV–VIS light barrier properties. Despite diminished glass transition temperatures (Tg), the values obtained are still adequate for food packaging applications.

PAni/SBR composite as anticorrosive coating for carbon steel, part II: electrochemical characterization

Conducting polymer composites have gained popularity into the field of organic anticorrosive coatings research due to their low environmental and health impact. In this work, the effect of the conducting polymer/elastomer ratio and the PAni doping method on the electrochemical behavior of polyaniline/styrene butadiene rubber films (PAni/SBR) has been studied in order to evaluate the performance of the proposed coatings for carbon steel corrosion prevention. According to open circuit potential measurements, linear polarization resistance tests, electrochemical impedance spectroscopy and polarization curves, the use of dodecyl benzene sulfonic acid as doping agent and the reduction of the PAni content in the composite enhance the anticorrosive behavior of PAni/SBR composites by inducing carbon steel passivation process.

Crude oil UV spectroscopy and light scattering characterization

ABSTRACT Crude oil is a complex mixture of hydrocarbons representing several classes of compounds. Some of these constituents significantly affect refinery processes and analysis procedures. Ultraviolet-visible (UV-vis) spectroscopy has received wide acceptance because of its broad scope, given that many active species in the spectrum of UV, and many more that with proper treatment, are able to form visible species in that spectrum. In this study two crude oils from different sources were analyzed without dilution C1-RC, in the coastal region and C2-RM of the maritime region of the Gulf of Mexico. Stages for obtaining calibration curves depending on the change in concentration of crude, starting from crude standard solutions and evaluating the repeatability of the method and the dispersion, were established. The results show three signals: (a) 230 nm corresponding to benzene compounds, (b) 260 nm to naphthenic compounds, and (c) 410 nm Soret band corresponding to the metal porphyrins. These species are found in asphaltenes, signals were evaluated individually for separate calibration curves, at concentrations between 10 and 90 mg L−1. The model equation of each curve based on the absorbance and concentration determination coefficient values for each compound are reported. It was possible to establish that the method developed is suitable for oil solutions at low concentrations.

Polypyrrole microcontainer structures and doughnuts designed by electrochemical oxidation: an electrochemical and scanning electron microscopy study

Abstract Scanning electron microscopy (SEM) is employed to monitor the surface morphology of polypyrrole films (PPy) grown on different working electrodes (i.e., vitreous carbon and Au (111)) under diverse experimental conditions (i.e., dynamic vs. static potential protocols) and anion dopants (i.e., I- and F-). The morphology of the electrosynthesized films includes rings (doughnuts) and microcontainers, and depends on the synthesis parameters such as the electropolymerization method, the nature of the substrate, the anion dopant, and the sequence of sandwich composite growth. The formation of well-defined rings and microcontainers is attributed to overoxidation occurring during the formation of F--doped PPy. It is possible to design microcontainers by controlling the overoxidation and degradation of the polymer surface.

Cathodic Production of ClO2 from NaClO3

A study is presented on the cathodic reduction in ClO ― 3 ions in acidic and circumneutral solutions. The systems thermodynamics (i.e., the corresponding Pourbaix diagram) is an aid in predicting the appropriate conditions for the different processes to occur and in interpreting the results. Linear sweep and cyclic voltammetries on a Pt electrode, together with a spectroelectrochemical arrangement that allows for real-time monitoring of these processes by means of both a UV/visible spectrophotometer and a potentiostat, yield evidence of the ClO ― 3 to ClO ― 2 reduction in circumneutral media and of a multiplicative effect in the production of ClO 2 in highly acidic sulfate media due to a chemical/electrochemical/chemical pathway.

Evaluation of Addition of Reactive Resin for an Adhesive Formulation of Pressure-Sensitive Adhesive

Nowadays, adhesive industry is growing, and its development will be important in a short future because it offers good returns, and in some cases it is a better option for packaging and sealing with advantages in prices, productivity and weight reduction. In terms of joining and/or sealing, adhesives are well positioned among joining systems; however, knowledge about adhesives is need for their efficient use and only through proper design of the union can be achieved satisfactory results. In this chapter, a development of a formulation of pressure-sensitive adhesive based on styrenebutadiene copolymers using a reactive resin is reported. Non-aromatic solvents were used in adhesive formulation with the aim of avoiding the emission of harmful solvents into the Atmosphere, and the adequate combination and amount of solvents were found. The effect of addition of a phenolic resin in the adhesive formulation as a crosslinking agent was evaluated. By means Fourier Transform Infrared spectroscopy (FTIR), the crosslinking reaction was also studied. The performance of adhesive formulation was evaluated by means of dynamic mechanical analysis (DMA).

Synthesis of High cis-1,4-BR with Neodymium for the Manufacture of Tires

The salt of neodymium has been widely used in industrial polymerization of 1,3-butadiene. We used the ternary catalytic system neodymium versatate/diethylaluminum chloride/triisobutylaluminum (NdV3/DEAC/TIBA) with 0.5 mM NdV3/100 g Bd, NdV3 : DEAC = 1 : 9 mol : mol, and TIBA = 25, 50, 100, and 200 mM. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI) were analyzed by GPC; the rheological properties were analyzed by DMA. The formulations were prepared with carbon black (IRB6) as reinforcing filler and the mechanical properties were compared to behavior of the different elastomeric compounds. The elastomeric compounds were characterized by their rheological properties, tensile strength, abrasion resistance, tear strength, permanent set, resilience, and fatigue properties. The high cis-1,4 polybutadiene (high cis-1,4-BR) was obtained with a percentage of cis-1,4 ≥97%. The weight-average molecular weight (Mw) was from 150 × 103 to 900 × 103 g/mol and polydispersity index (PDI) was from 3.1 to 5.1. This work is based on evaluation of the effect of the catalyst system on the final properties of the synthesized polybutadiene.

Deposition of Ibuprofen Crystals on Hydroxypropyl Cellulose/Polyacrylamide Gel: Experimental and Mathematic Modeling Releasing

The crystallization of nonsteroidal anti-inflammatory drug [2-(4-isobutyl-phenyl) propionic acid] ibuprofen (IBP) on a hydroxypropyl cellulose (HPC) and polyacrylamide (PAAm) gel was studied as well as the release kinetics of the drug. The IBP was crystallized on the gel surface of HPC/PAAm. It had a prismatic shape and the growth was made in an aqueous medium; the crystallinity grade of the gels HPC/PAAm and HPC/PAAm-IBU increased to 68% and to 58%, respectively. The release of IBP is performed by two means: by a non-Fickian diffusion process and by relaxation of the chains of the gel; without regard to temperature and the diffusion media, this correlates with the lower critical solution temperature (LCST) of the proposed gel. This polymer matrix provides an option for releasing nonsteroidal anti-inflammatory drugs in a temperature range of 35–39°C. Korsmeyer and Peppas mathematical model was simulated for data releases, statistically significant at 95% confidence level.

Chitosan-Starch Films with Natural Extracts: Physical, Chemical, Morphological and Thermal Properties

The aim of this study is to analyze the properties of a series of polysaccharide composite films, such as apparent density, color, the presence of functional groups, morphology, and thermal stability, as well as the correlation between them and their antimicrobial and optical properties. Natural antioxidants such as anthocyanins (from cranberry; blueberry and pomegranate); betalains (from beetroot and pitaya); resveratrol (from grape); and thymol and carvacrol (from oregano) were added to the films. Few changes in the position and intensity of the FTIR spectra bands were observed despite the low content of extract added to the films. Due to this fact, the antioxidants were extracted and identified by spectroscopic analysis; and they were also quantified using the Folin-Denis method and a gallic acid calibration curve, which confirmed the presence of natural antioxidants in the films. According to the SEM analysis, the presence of natural antioxidants has no influence on the film morphology because the stretch marks and white points that were observed were related to starch presence. On the other hand, the TGA analysis showed that the type of extract influences the total weight loss. The overall interpretation of the results suggests that the use of natural antioxidants as additives for chitosan-starch film preparation has a prominent impact on most of the critical properties that are decisive in making them suitable for food-packing applications.