Ana María Mendoza-Martínez

Cellulose derivatives from cellulosic material isolated from Agave lechuguilla and fourcroydes

Fibers isolated from Agave lechuguilla(lechuguilla) and fourcroydes (henequen) contain about 80%cellulose, 5% hemicellulose and 15% lignin. They are a renewable resource,interesting as feedstock for new products obtained by chemicalfunctionalization. In the present paper the reactivity of such fibrousmaterialsunder typical conditions for modification of cellulose was studied. Treatmentwith n-octanol/aqueous NaOH of the fibers leads to an activated expandedgel-like material with enhanced accessibility. Carboxymethylation, sulfation,acetylation and tritylation reactions as well as subsequent carboxymethylationof the trityl derivative and selective oxidation of the primary hydroxylfunction of carboxymethylated products with TEMPO/NaBr/NaClO were successfullycarried out under conditions typical for cellulose reactions. The products werecharacterized by means of 13C-NMR and 1H-NMR spectroscopyandHPLC after complete depolymerization, by GPC, and by the determination ofsolubility.

Composites from chicken feathers quill and recycled polypropylene

Recycled polypropylene composites reinforced with quill from chicken feathers were prepared by extrusion process. Chicken feathers, a worldwide waste without any relevant application, may potentially replace nonrenewable reinforcements in composites. The effects of quill reinforcement on the density, as well as the thermal, thermo-mechanical and morphological properties of the composites, were evaluated. Quill showed an excellent compatibility with the polypropylene matrix, revealed by the good dispersion that was confirmed by the physical appearance observed with aid of scanning electron microscopy. This fact is due to the hydrophobic nature of keratin in quill. All of the composites showed higher storage modulus than simple polymer, particularly for the lowest quill content. In addition, the composite materials also had a lower density. The transition temperature remained almost unaltered compared with polypropylene. However, the thermal stability was observed to be strongly related to the quill content. Thus, this study reports a successful industrial process applied to a new natural reinforcement material: quill, used to synthesize composites with an amply used polymer: polypropylene; which can open an important gate towards the extended exploitation of keratin quill as a novel and renewable reinforcement material.

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.

EFFECT OF INITIATOR AND CROSS-LINKING AGENT ON A SEMI-IPN OF (PU-STARCH)/PMMA

The variations of the cross-linking agent, initiator, and molar ratio in the synthesis of a semi-interpenetrating polymer network (IPN) of polyurethane-starch/polymethyl methacrylate (PMMA) were studied for their viscoelastic and morphologic properties. The synthesized semi-IPNs were evaluated by means of dynamic mechanical analysis (DMA), finding that a relationship exists between the quantity of cross-linker and the storage module, where alpha and beta relaxations are present in the polymethyl methacrylates rigid chains, and this peak widens upon increasing the quantity of PMMA in the semi-IPN. The morphology of the semi-IPNs shown by SEM and AFM micrographies suggests that 0.5 wt.% of initiator and 3 wt.% of cross-linker demonstrate uniform surfaces.

Evaluation of Graft Copolymerization of Acrylic Monomers Onto Natural Polymers by Means Infrared Spectroscopy

Infrared spectroscopy (IR spectroscopy) is a technique based on the vibrations of atoms of a molecule. An IR spectrum is commonly obtained by passing IR radiation through a sample and determining what fraction of the incident radiation is absorbed at a particular energy. The energy at which any peak in an absorption spectrum appears corresponds to the frequency of a vibration of a part of a sample molecule (Bickford, 2008).

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.

EVALUACIÓN TÉRMICA DEL CURADO DE ADHESIVOS BASE SBR USANDO PERÓXIDO DE DICUMILO

Curing is an important process in adhesive formulation, but scant reports on the study of the kinetics of curing in adhesive are currently available, particularly for formulations including styrene-butadiene copolymers. The focus of the present work was to thermodynamically quantify the curing reaction in pressure-sensitive adhesives (PSA) obtained from styrene-butadiene copolymers, the effect of dicumyl peroxide (DCP) ratio, which acts as a crosslinking agent, and also evaluate the effect of two reactive adhesive resins, sylvalite and piccolyte. Kinetic parameters were determined by differential scanning calorimetry (DSC) in an isothermic and dynamic mode, gel content was determined as was swelling degree, given these characteristics can be associated with the curing reaction. The kinetic study showed the curing reaction was first order, according to the Ozawa and Kissinger equation. Resins have affinity to BR segment, while in the case of sylvalite and piccolyte to the PS segment, varying behavior with dicumyl peroxide in the adhesive mixture. Lower swelling values were associated with an increase in crosslinking, indicative a curing reaction took place, and the gel content test was used to corroborate the results.

Synthesis and characterization of organogel from poly(acrylic acid) with cellulose acetate

Abstract In the last decade, the interest in physical organogels has grown rapidly with the discovery and synthesis of a very large number of diverse molecules, which used organic solvents at low concentrations. New organogels based on poly (acrylic acid) (PAA) and cellulose acetate (CA) were prepared as thin films to study properties and swelling behavior. In organogels synthesis different crosslinking agent and initiator concentrations were studied. The swelling for PAA/CA organogels was carried out with acetone at 3 different temperatures (30°, 40° and 50 °C) and pH of 6.5 (pHacetone= 6.5). The higher swelling for PAA/CA organogels was 770% for 25PAA/75CA composition ratio with 3%wt N,N´-methylene-bis acrylamide (MBA) and 1%wt potassium persulphate (KPS) at 30 °C. The films were analyzed by FTIR and the presence of functional groups of each polymer was confirmed without secondary reactions. The DSC analysis indicated two glass transition temperatures (Tg); at 106 °C corresponding to PAA and 86 °C, corresponding to CA, respectively, indicative of phase separation, characteristic of gels. Surface morphology was analyzed by Scanning electron microscopy (SEM) showing smooth surface and small crystal forms.

Estudio de copolimerización injerto del acrilato de butilo sobre almidón empleando sistema iniciador redox

The mixture of synthetic and natural materials yields a material with improved physical-chemical properties. One way of obtaining this kind of material is through graft copolymerization. Some natural materials have been used in graft copolymerization with synthetic monomers. In this work, graft copolymerization of butyl acrylate (BA) onto starch using a redox initiator system was carried out. The graft yield was evaluated for different reaction conditions. The graft copolymer was characterized by infrared spectroscopy, thermal analysis and scanning electron microscopy (SEM).