Edison Bittencourt

Radiation-Induced Addition of Flame Retardants to the Double Bond in Acrylamidomethyl Cellulose

Cotton and rayon fabrics were condensed with N-methylol acrylamide to give products with various degrees of un saturation. Radiation-induced free-radical addition to the double bonds in these fabrics was accomplished with carbon tetrachloride, bromoform, chloroform, bromotetrachloromethane, polyethylene oxide, chloral and bromal hydrate, and sodium hypophosphite. Stannous and stannic chloride were also reacted by what seems to be a different mechanism. Bromination of these fabrics is also described. Significant flame retardancy was obtained without alteration of hand, because the reactions are limited to the inside of the cellulose fiber.

Synthesis of porous macrospheres from amino-polymers

Abstract Porous macrospheres with controlled diameter were produced using N-methylolacrylamide and urea–formaldehyde resins synthesized in our laboratories. Hot silicon oil was used to form the porous macrospheres which were characterized by using infrared spectroscopy (FTIR), scanning electron microscopy, mercury porosimetry and surface area determination (BET). Porous macrospheres of amino-polymers were used as support in immunoassays type ELISA (enzyme linked immunosorbent assay) in which mouse immunoglobulin (IgG) was immobilized, and detected by rabbit anti-mouse immunoglobulin (a-IgG) labeled with horseradish peroxidase. Responses were obtained up to a dilution ratio of 1:4000 of the conjugate standard (1 mg/ml) and 10 μ g/ml of IgG solution to recover the spheres in pH=4.5.

Extração de corantes de milho (Zea mays L.)

Natural colorants were craftly made and widely used before the discovery of the synthetic colorants. The study and the use of natural colorants have become important again in the last few years due to questions raised by the international health organizations and consumers related to the indiscriminate use of synthetic colorants which were linked to the development of degenerative illnesses and environmental impact. The colorant extracted from purple corn (Zea Mays L.) was used by the Inca civilization to prepare food and to dye textile fibers. In this work, pigments from the anthocyanin group were extracted from purple corn and red corn (Zea Mays L.) varieties and were later characterized. Three extraction methods were used: immersion, lixiviation with some changes, and supercritical extraction (ESC). The best method of extraction was lixiviation, which reached 88% (m/m) of performance as a function of the mass of colorant extracted and of the raw materials. Also using the modified lixiviation it was possible to concentrate the acylate compounds in 3% as well as to recover 85% of solvent used. A pH indicator was obtained by fixing the anthocyanins on a filter paper based on anthocyanins stabilization. This technique can be utilized in laboratory chemistry lessons.

Electron-Beam-Initiated Grafting of Flame Retardants to Fabrics Containing Cellulose. I. Reaction Rate Studies

Abstract Triallyl phosphate (I), bis(β-chloroethyl) vinyl phosphonate (II), and a multi-functional condensate of n were grafted to cotton and rayon fabrics and the grafted products screened for potential flame retardancy. Grafting was initiated by a 48 × 6 in. electron beam, in air, from a 550 kV, 20 mA accelerator powered by an insulated core transformer, with a dose rate of approximately 1 Mrad/sec. The monomers were either copolymerized in untreated fabric with N-methylol acrylamide as a coreactant or were copolymerized with pendant double bonds in fabric that had been acrylamidomethylated in a prior step.

Determinação dos índices de cristalinidade de fibras celulósicas

The purpose of this work was to develop analytical techniques for structural characterization of cellulosic fibers. To establish a relationship between the two methods that determine crystallinity index, three varieties of cotton (IAC 17, IAC 19, and IAC 20) and fibers of viscose, rami and rami chemical treated were used. Two empirical methods, x-ray diffraction and infrared spectroscopy, were used to evaluate the crystallinity index. Differentiation of IAC cotton varieties was possible with the crystallinity index obtained by infrared spectroscopy; but, not with the x-ray diffraction method. The crystallinity index obtained by these two methods had no correlation with physical properties of cotton fibers. When cellulose fibers with different treatment were assayed, there was a high correlation (r = 0.95) between the two methodologies used for the determination of crystallinity index.

Electron Beam Fixation of a Flame Retardant Applied Without Water by Coating Methods Fabric Properties and Bilateral Distribution of the Flame Retardant in the Cotton Fibers

Low wet pickup and high solids finishing techniques can produce fabric with the resin distributed in a variety of ways. depending on the method used. Liquid Fyrol 76®, applied to cotton fabric by a number of different procedures, and polymerized at room temperature with electron beam, gave resin distribution that varied from quite nonuniform at low application pressures to complete uniformity at high pressures, even to the point of lumen and fiber penetration. Small amounts of water (as low as 7% above regain) before application effected a uniform distribution even at low pressure.

Surface Modification of EPDM Rubber by Reactive Argon-Oxygen Plasma Process

The ethylene-propylene diene monomer (EPDM) rubber is an important material for rocket engine technology due to its thermal and mechanical characteristics. The improvement of the adhesion characteristics of EPDM on other kinds of polymers, using plasma technology, has been the major subject of many research works carried out during the last years. In this work, the EPDM surface activation process was carried out in a reactive ion etching reactor (RIE) operated at 13,54 MHz using pure oxygen and a gas mixture of argon and oxygen. These essays were performed varying the process pressure from 70 mTorr to 1000 mTorr, process time from 1 min to 10 min and RF power input from 50 W to 200: W. The surfaces of the treated samples were analyzed by Fourier transform infrared attenuated total reflection spectroscopy (FTIR- ATR). The evolution of the C-OH, and C=O and R-O chemical groups were observed as a function of the plasma process parameters. The analysis of the IR spectra showed that there are experimental cond...

Platinum blue staining of cells grown in electrospun scaffolds

Fibroblast cells grown in electrospun polymer scaffolds were stained with platinum blue, a heavy metal stain, and imaged using scanning electron microscopy. Good contrast on the cells was achieved compared with samples that were gold sputter coated. The cell morphology could be clearly observed, and the cells could be distinguished from the scaffold fibers. Here we optimized the required concentration of platinum blue for imaging cells grown in scaffolds and show that a higher concentration causes platinum aggregation. Overall, platinum blue is a useful stain for imaging cells because of its enhanced contrast using scanning electron microscopy (SEM). In the future it would be useful to investigate cell growth and morphology using three-dimensional imaging methods.

EFFECT OF THE ATMOSPHERE IN THE ABLATION OF CARBON-PHENOLIC COMPOSITES USED IN THERMAL PROTECTION SYSTEMS

Ablatives composite materials are vastly employed in rocket nozzle components and as thermal protection shields in aerospace industry. In this work, an experimental study on the influence of atmospheric pressure on the ablation of carbon-phenolic composites is performed. The composite is produced by wrapping process and used in the manufacture of thermal re-entry protections. Samples were tested in the following thermal fluxes: 0.626; 0.903; 1,376 and 1,725 MW/m2 in the 30, 50, 70 and 90 sec exposure times in a plasma tunnel simulating the pressure of 400 Pa and compared to the results obtained in the same thermal fluxes and exposure times at atmospheric pressure. Results were also compared with a computational simulation and a simple and reliable model is proposed to express the influence of environment pressure, presenting good agreement and physical coherence. The specific mass loss rate at rarefied pressure was lower than obtained at dense atmospheric pressure but this difference decreases with the increase of the exposure time due to the process of densification of the carbonized layer. The low concentration of oxygen existing in the rarefied air pressure contributes to slow pyrolysis reaction during the ablation process

Trends in polymeric electrospun fibers and their use as oral biomaterials

Electrospinning is one of the techniques to produce structured polymeric fibers in the micro or nano scale and to generate novel materials for biomedical proposes. Electrospinning versatility provides fibers that could support different surgical and rehabilitation treatments. However, its diversity in equipment assembly, polymeric materials, and functional molecules to be incorporated in fibers result in profusion of recent biomaterials that are not fully explored, even though the recognized relevance of the technique. The present article describes the main electrospun polymeric materials used in oral applications, and the main aspects and parameters of the technique. Natural and synthetic polymers, blends, and composites were identified from the available literature and recent developments. Main applications of electrospun fibers were focused on drug delivery systems, tissue regeneration, and material reinforcement or modification, although studies require further investigation in order to enable direct use in human. Current and potential usages as biomaterials for oral applications must motivate the development in the use of electrospinning as an efficient method to produce highly innovative biomaterials, over the next few years. Impact statement Nanotechnology is a challenge for many researchers that look for obtaining different materials behaviors by modifying characteristics at a very low scale. Thus, the production of nanostructured materials represents a very important field in bioengineering, in which the electrospinning technique appears as a suitable alternative. This review discusses and provides further explanation on this versatile technique to produce novel polymeric biomaterials for oral applications. The use of electrospun fibers is incipient in oral areas, mainly because of the unfamiliarity with the technique. Provided disclosure, possibilities and state of the art are aimed at supporting interested researchers to better choose proper materials, understand, and design new experiments. This work seeks to encourage many other researchers–Dentists, Biologists, Engineers, Pharmacists–to develop innovative materials from different polymers. We highlight synthetic and natural polymers as trends in treatments to motivate an advance in the worldwide discussion and exploration of this interdisciplinary field.