Coating of Cotton Yarn with Poly(vinyl alcohol) and Poly(N-vinyl-2-pyrrolidone) Crosslinked via Ultraviolet Radiation

The coating of cotton fiber is used in the textile industry to increase the mechanical resistance of the yarn and their resistance to vibration, friction, impact, and elongation, which are some of the forces to which the yarn is subjected during the weaving process. The main objective of this study was to investigate the use of synthetic hydrophilic polymers, poly(vinyl alcohol) (PVA), and poly(N-vinyl-2-pyrrolidone) (PVP) to coat 100% cotton textile fiber, with the aim of giving the fiber temporary mechanical resistance. For the fixation of the polymer on the fiber, UV-C radiation was used as the crosslinking process. The influence of the crosslinking process was determined through tensile testing of the coated fibers. The results indicated that UV-C radiation increased the mechanical resistance of the yarn coated with PVP by up to 44% and the yarn coated with PVA by up to 67% compared with the pure cotton yarn, that is, without polymeric coating and crosslinking. This study is of great relevance, and it is important to consider that UV-C radiation dispenses with the use of chemical substances and prevents the generation of toxic waste at the end of the process. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 2560-2567, 2011

Crosslinking of Poly(N-vinyl-2-pyrrolidone) in the Coating of Cotton Yarn

Coating of cotton yarn is employed in the textile industry to increase the mechanical resistance of the yarns and resistance to vibration, friction, impact, and elongation, which are some of the forces to which the yarn is subjected during the weaving process. The main objective of this study is to investigate the usage of a synthetic hydrophilic polymer, poly(N-vinyl-2-pyrrolidone) (PVP), to coat 100% cotton textile yarn, aiming to give the yarn a temporary mechanical resistance. For the improvement of the mechanical resistance of the yarn, the following crosslinking processes of PVP were investigated: UV-C (ultraviolet) radiation, the Fenton and photo-Fenton reactions, and sensitized UV-C radiation. The influence of each crosslinking process was determined through tensile testing of the coated yarns. The results indicated that the best crosslinking process employed was UV-C radiation; increasing the mechanical resistance of the yarn up to 44% if compared with the pure cotton yarn, that is, without polymeric coating and crosslinking. POLYM. ENG. SCI., 51:445-453, 2011. (C) 2010 Society of Plastics Engineers

Electrical and optical properties of poly(2-dodecanoylsulfanyl-p-phenylenevnylene) and its application in electroluminescent devices

We describe the optical and electrical characterization of a poly(p-phenylenevinylene) derivative: poly(2-dodecanoylsulfanyl-p-phenylenevinylene) (12COS-PPV). The electrical characterization was carried out on devices with the FTO\PEDOT:PSS\12COS-PPV/Al structure. Positive charge carrier mobility mu(h) of similar to 1.0 x 10(-6) cm(2) V(-1) s(-1) and barrier height phi of similar to 0.1 eV for positive charge carrier injection at the PEDOT:PSS/12COS-PPV interface were obtained using a thermionic injection model. FTO\PEDOT:P55\12COS-PPV/Ca devices exhibited green-yellow electroluminescence with maximum emission at lambda = 540 nm.

FT-Raman investigation of biodegradable polymers: Poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

This work presents a FT-Raman study (lambda(0) = 1064 nm) of naturally occurring polyester poly[(R)-3-hydroxybutyrate] (PHB) and its copolymer poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) with 5,8 and 12 mol % of HV (hydroxyvalerate). The FT-Raman spectra of films indicate that full width at half height of the band centered at 1725 cm(-1) and relative intensity of bands at 1443 and 1458 cm(-1) can be use to estimate the crystalline degree in film samples. The similarity between Raman spectra of molten PHB and PHBV and theirs CDCl(3) solutions suggested that molten polymers present similar conformation than polymers in solution. Raman data of these samples showed that bands at 1220, 1402, 1725, 2998 and 3009 cm(-1) are due to crystalline helical structure and the bands at 1453, 1740, 2881, 2938 and 2990 cm(-1) are originated from disordered domains. It is shown that composition of PHBV samples can be estimated by analyzing the ratio of the intensity of the bands at 2938 cm(-1) (nu C-H) and 1740 cm(-1) (nu C=O) in the spectra of solutions and of bands at 1354 (wCH(2)) and 1740 cm(-1) (nu C=O) in spectra of molten polymers. (C) 2010 Elsevier B.V. All rights reserved.

Raman spectra of polymer electrolytes based on poly(ethylene glycol) dimethyl ether, lithium perchlorate, and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

Raman spectra of polymer electrolytes based on poly(ethylene glycol) dimethyl ether (PEGdME) with LiClO(4), PEGdME/LiClO(4), and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, PEGdME/[bmim]PF(6), are compared. Raman spectroscopy suggests stronger interactions in PEGdME/LiClO(4) than PEGdmE/[bmim]PF(6), thus corroborating previous results obtained by molecular dynamics simulations. Quantum Chemistry methods have been used to calculate vibrational frequencies and the equilibrium structure of segments of the polymer chain around the cation. A consistent picture has been obtained from Raman spectroscopy, density functional theory (DFT) calculations, and molecular dynamics simulations for these polymer electrolytes. (C) 2010 Elsevier B.V. All rights reserved.

Structure of chemically prepared poly-(para-phenylenediamine) investigated by spectroscopic techniques

The structure of chemically prepared poly-p-phenylenediamine (PpPD) was investigated by Resonance Raman (RR), FTIR, UV-VIS-NIR, X-ray photoelectron (XPS), X-ray Absorption at Nitrogen K edge (N K XANES), and Electron paramagnetic Resonance (EPR) spectroscopies. XPS, EPR and N K XANES data reveal that polymeric structure is formed mainly by radical cations and dication nitrogens. It excludes the possibility that PpPD chains have azo or phenazinic nitrogens, as commonly is supposed in the literature. The RR spectrum of PpPD shows two characteristic bands at 1527 cm(-1) and 1590 cm(-1) that were assigned to nu C=N and nu C=C of dication units, respectively, similar to polyaniline in pernigraniline base form. The presence of radical cations was confirmed by Raman data owing to the presence of bands at 1325/1370 cm(-1), characteristic of nu C-N of polaronic segments. Thus, all results indicate that PpPD has a doped PANT-like structure, with semi-quinoid and quinoid rings, and has no phenazinic rings, as observed for poly-o-phenylenediamine. (C) 2009 Elsevier Ltd. All rights reserved.

Stereochemical and electronic interaction studies of some N-methoxy-N-methyl-2-[(4 `-substituted)phenylsulfinyl]propanamides

The (1)H NMR spectra of N-methoxy-N-methyl-2-[(4`-substituted)phenylsulfinyl]-propanamides [Y-Ph-S(O)CH(Me)C(O)N(OMe)Me; Y = OMe 1, Me 2, H 3. Cl 4, NO(2) 5] along with the X-ray diffraction analysis of the nitro-derivative (5). have shown the existence of two pairs of diastereomers (racemic mixture) [C(R)S(S)/C(S)S(R) (diast(1)) and C(R)S(R)/C(S)S(S) (diast(2))] in the ratio of ca. 7:3. respectively. The v(CO) IR analysis of the title compounds supported by HF and B3LYP/6-31G** calculations of 3 and of the parent N-methoxy-N-methyl-propanamide (6) by HF, have shown that diast(1) exists in an equilibrium between the two more polar and more stable quasi-cis (q-c(1) and q-c(2)) conformers and the gauche(g) conformer. The population of the g conformer in the equilibrium increases with the increase in the solvent polarity, which is attributed to a larger solvation effect on the carbonyl and sulfinyl groups. Diast(2) of compound 3 occurs in the gas phase as an equilibrium between the most stable quasi-gauche (q-g) conformer and the quasi-cis (q-c) conformer, both presenting very similar dipole moments. The former is stabilized by electrostatic and charge transfer interactions, which results in a less solvated spatial arrangement. Moreover, all conformers of both diastereomers are stabilized by several intramolecular hydrogen bonds. X-ray single crystal analysis performed for diast(1) and for diast(2) of 5 indicates that both stereoisomers assume, in the solid state, the anti-clinal (gauche) conformation. For the crystal packing, diast(1) of 5 is made up of three molecules joined through two centro-symmetric H center dot center dot center dot O hydrogen bonds. (C) 2008 Elsevier B.V. All rights reserved.

Phenol-furfural resins to elaborate composites, reinforced with sisal fibers - Molecular analysis of resin and properties of composites

Resol type resins were prepared in alkaline conditions (potassium hydroxide or potassium carbonate) using furfural obtained by acid hydrolysis of abundant renewable resources from agricultural and forestry waste residues. The structures of the resins were fully determined by H-1, C-13, and 2D NMR spectrometries with the help of four models compounds synthesized specially for this study. MALDI-Tof mass spectrometry experiments indicated that a majority of linear oligomers and a minority of cyclic ones constituted them. Composites were prepared with furfural-phenol resins and sisal fibers. These fibers were chosen mainly because they came from natural lignocellulosic material and they presented excellent mechanical microscopy images indicated that the composites displayed excellent adhesion between resin and fibers. Impact strength measurement showed that mild conditions were more suitable to prepare thermosets. Nevertheless, mild conditions induced a high-diffusion coefficient for water absorption by composites. Composites with good properties could be prepared using high proportion of materials obtained from biomass without formaldehyde. (c) 2008 Wiley Periodicals, Inc.

Electropolymerization studies of PAni/(poly)luminol over platinum electrodes

This work presents a cyclic voltammetry study of the polyaniline/polyluminol copolymer on platinum electrodes. The results show that under determined conditions it is possible to obtain the copolymer deposited on a metallic surface. The luminol presence clearly affects the oxidation of aniline in the nucleation process and, additionally, changes the cyclic voltammetric characteristics of the obtained material. In this aspect, the copolymer presents hybrid characteristics when compared to the polyaniline and polyluminol separately obtained and seems to present intermediary conductivity.

Biobased composites from glyoxal-phenolic resins and sisal fibers

Lignocellulosic materials can significantly contribute to the development of biobased composites. In this work, glyoxal-phenolic resins for composites were prepared using glyoxal, which is a dialdehyde obtained from several natural resources. The resins were characterized by (1)H, (13)C, (2)D, and (31)P NMR spectroscopies. Resorcinol (10%) was used as an accelerator for curing the glyoxal-phenol resins in order to obtain the thermosets. The impact-strength measurement showed that regardless of the cure cycle used, the reinforcement of thermosets by 30% (w/w) sisal fibers improved the impact strength by one order of magnitude. Curing with cycle 1 (150 degrees C) induced a high diffusion coefficient for water absorption in composites, due to less interaction between the sisal fibers and water. The composites cured with cycle 2 (180 degrees C) had less glyoxal resin coverage of the cellulosic fibers, as observed by images of the fractured interface observed by SEM. This study shows that biobased composites with good properties can be prepared using a high proportion of materials obtained from natural resources. (C) 2009 Elsevier Ltd. All rights reserved.

Characterization of Polyurethane Resins by FTIR, TGA, and XRD

Fourier Transformed Infrared Spectroscopy, Thermogravimetric Analysis, and X-ray Diffractometry have been used to investigate the rigid, semi rigid, and soft polyurethane (PU) forms, which were developed by the Group of Analytic Chemistry and Technology of Polymers - USF - Sao Carlos. The -NCO/-OH ratios were 0.6, 0.5, and 0.3% for rigid, semi rigid, and soft PUs, respectively, showing that different ratios cause differences in thermal behaviors and crystalline structures of the synthesized PU resins. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 263-268, 2010