bluuebunny/crossref_metadata_2025_split huggingface dataset:
Encapsulation of pesticides in a starch‐calcium adduct
Authors: Shasha B. S. , Trimnell D. , Otey F. H. 
Published: April 2003

AbstractA simple method of encapsulating water‐insoluble pesticides in a starch matrix is described. The method consists of mixing the pesticide with alkali starch followed by precipitation with a calcium chloride solution. A starch–calcium adduct that entraps the pesticide in small cells within granular particles is formed. Liquid and solid pesticides were successfully encapsulated by the new method. By use of the herbicide trifluralin [2,6‐dinitro‐N,N‐dipropyl‐4‐(trifluoromethyl) benzenamine] as core material more than 90% recovery and encapsulation was achieved. Use of acid‐modified starches and flours resulted in a lower percentage of encapsulation. Effective encapsulation was also achieved by replacing calcium chloride with strontium chloride or barium chloride.
On the role of oxygen in the horizontal flame spread of polypropylene
Authors: Jakes K. A. , Drews M. J. 
Published: April 2003

AbstractThe horizontal flame‐spreading behavior of slabs of uninhibited polypropylene (PP) and commercial polymethylmethacrylate (PMMA) is described, and the flame spread and mass vaporization rates are discussed. The quantities of peroxide and carbonyl moieties formed on the surface of PP beneath the flame front, determined by an iodometric procedure and by reaction with 2,4‐dinitrophenylhydrazine, are presented. A statistical analysis was performed to ascertain the significance of these quantities formed in four combustion environments, each differing in oxygen concentration. Flame and surface temperatures of the PP samples at each oxygen concentration as well as flame and surface temperatures of samples burned in 23% oxygen with an added external radiant heat source are presented. The data support the concept that surface oxidative reactions occur in the combustion of PP, that the quantity of oxidative products is related to the concentration of oxygen in the combustion environment, and the possible importance of these reactions in producing heat to propagate the flame is indicated. Comparison of PP and PMMA show that the two are quite dissimilar in flame‐spreading behavior.
Plasma polymerization. IV. A systematic investigation of the inductively coupled RF plasma polymerization of pentafluorobenzene.
Authors: Clark D. T. , Abrahman M. Z. 
Published: April 2003

AbstractThe composition and gross structural features of plasma polymer films prepared by inductively coupled RF plasmas excited in pentafluorobenzene were investigated by ESCA as a function of the operating parameters. The rate of film deposition is dependent on the W/FM parameter and on site of deposition. The polymer formed in the glow region shows only small variations in structure as a function of power and pressure. Polymer films deposited in the regions away from the site of primary excitation typically have a higher fluorine content than those formed in the coil region; the stoichiometry for the latter is comparable to that of the starting material.
Kinetic relationships and mechanism of ozone reaction with polystyrene in CCl4 solution
Authors: Kefely A. A. , Rakovski S. K. , Shopov D. M. , Razumovskii S. D. , Rakovski R. S. , Zaikov G. E. 
Published: April 2003

AbstractIn this work a study is made of the degradation on ozonation of unfractionated polystyrene (PS) in CCl4 solution. It was found that the ozone attack of PS molecules is accompanied by hydrogen abstraction from tertiary CH bonds and by the formation of ozonides due to the reaction of ozone with the aromatic rings. A scheme of PS degradation in solution is suggested; several kinetic parameters are evaluated.
Graft copolymerization. I. Grafting of hydroxyalkyl methacrylates on poly(vinyl alcohol)
Authors: Gonen Semadar , Kohn David H. 
Published: April 2003

AbstractNew graft copolymers were synthesized by grafting hydroxyethyl methacrylate and hydroxpropyl methacrylate on poly(vinyl alcohol) in aqueous solution with Ce+4ions as initiator. The dependence of the percentage of grafting and monomer conversion on the concentration of the monomer, on the concentration of the initiator, on the total concentration of the reactants, and on temperature and duration of the reaction were investigated. Some basic properties of the graft copolymers and some preliminary permeation measurements of water vapors through films, made from these copolymers, are also reported.
Mechanism of amine catalyzed isomerization of itaconic anhydride to citraconic anhydride: Citraconamic acid formation
Authors: Galanti Anthony V. , Keen Brian T. , Pater Ruth H. , Scola Daniel A. 
Published: April 2003

AbstractThe amine catalyzed isomerization of itaconic to citraconic anhydride has been investigated. Studies show that the rate of isomerization is dependent on the base strength and solvent media. Triethylamine causes complete isomerization within 5 min at room temperature in acetone or chloroform solvent, whereas aromatic tertiary amines such as pyridine and N,N‐dimethylaniline require time perods as long as 23h at room temperature for almost complete isomerization. In the presence of aniline no isomerization occures even under acetone reflux conditions over a 24 h period. For the preparation of citraconamic acids from itaconic anhydrides and aliphatic diamines nuclear magnetic resonance and infrared spectroscopic evidence is presented to support the reaction path of initial isomerization of itaconic anhydride to citraconic anhydride followed by amine attack on the anhydride to form the corresponding cis‐citraconamic acids. The mechanism of isomerization of itaconic to citraconic acids is proposed.
Dechlorination of N‐chloro poly(hexamethylene adipamide) and N‐chloro poly(ε‐caprolactam) products to the corresponding polyamides
Authors: Koutinas A. A. 
Published: April 2003

AbstractA rapid dechlorination method of N‐chloro poly(hexamethylene adipamide) and N‐chloro poly(ε‐caprolactam) to the corresponding polyamides was studied. This method can be used for molecular weight determinations of N‐chloro polyamides by viscosimetric measurements. The dechlorination was achieved in formic acid solution by the reaction of N‐chloro polyamides with trialkyl phosphites. The reaction was exothermic and vigorous and was applied to a series of products of various degrees of N‐chlorination covering the range of 0–100%. No N—Cl was detected by iodimetric titration of the dechlorination products. The dechlorination of N‐chloro polyamides was demonstrated by infrared (IR) spectroscopy. No significant molecular weight reduction except that taking place in the N‐chlorination reaction of poly(hexamethylene adipamide) was observed.
The effect of mixed solvents pyridine–carbon tetrachloride on the radical polymerization of methyl methacrylate
Authors: Pavlinec Juraj , Borsig Eberhard 
Published: April 2003

AbstractA study was made of the methyl methacrylate (MMA) solution polymerization in CCl4‐pyridine mixtures as well as in net components at 30, 50, and 70°C. The results obtained show that there are no significant deviations from additivity in the overall chain transfer constants that fit the straight line between the values of Cs for CCl4 and pyridine. It can be concluded that the EDA interaction between CCl4 and pyridine does not change the sensitivity of each component for chain transfer from propagation PMMA free radical. The pyridine in the system increases the rate of MMA polymerization as a result of the higher rate of initiation.
Head‐to‐head vinyl polymers. IV. Preparation and characterization of equimolar head‐to‐head copolymers of acrylic acid and its esters
Authors: Quach Loc , Otsu Takayuki 
Published: April 2003

AbstractThe alternating copolymer of ethylene with maleic anhydride was esterified with a number of aliphatic alcohols to yield its monoesters, which correspond structurally to equimolar (1:1) head‐to‐head (h‐h) copolymers of acrylic acid with alkyl acrylates. In addition, they were methylated with diazomethane to 1:1 h‐h copolymers of methyl acrylate with alkyl acrylates. For comparison the 1:1 head‐to‐tail (h‐t) copolymers of methyl acrylate with alkyl acrylates were prepared by radical copolymerizations. Some chemical, physical, and thermal properties of these 1:1 h‐h and h‐t copolymers were evaluated and compared. The softening and glass transition temperatures of the 1:1 h‐h copolymers were somewhat higher than those of the corresponding 1:1 h‐t copolymers, which indicated that the h‐h replacements made the polymer chain stiffer and less flexible. The 1:1 h‐h copolymers were also observed to degrade thermally at somewhat higher temperatures and with higher rates than the 1:1 h‐t copolymers. The ratio of alcohol to monomer found in the pyrolysis products was higher for the 1:1 h‐h than for its respective 1:1 h‐t copolymer.
Effect of ionizing radiation on the chemical composition, crystalline content and structure, and flow properties of polytetrafluoroethylene
Authors: Fisher W. Keith , Corelli J. C. 
Published: April 2003

AbstractThis article describes a study of ionizing radiation‐induced changes in the chemical composition, crystalline content and structure, and flow properties in polytetrafluoroethylene (PTFE). Irradiatins conducted in the presence of oxygen cause acid fluoride end groups to be formed, which on exposure to water vapor hydrolyze to form carboxylic acid end groups. Analyses by infrared (IR) spectroscopy indicate that when irradiated in a vacuum PTFE exhibits defect absorption bands which have been attributed to branch and crosslink formation. The crystalline content of PTFE which increases after exposure to radiation was monitored by IR spectroscopy, density, x‐ray diffraction on unoriented samples, and differential scanning calorimetry (DSC) as the measurement probes. The melt viscosity of PTFE exposed to various radiation doses in air decreases dramatically after irradiation. Between 2.5 and 5 Mrd an increase in viscosity is attributed to the formation of branches and crosslinks. The effects of preirradiation crystallinity and postirradiation heat treatment were studied. A model is presented to explain the mechanism of the observed radiation effects.
Aromatic polyesters obtained directly from hydroxybenzoic acids by hexachlorocyclotriphosphatriazene (PNC) in pyridine
Authors: Higashi Fukuji , Kubota Koichi , Sekizuka Misuzu , Higashi Morio 
Published: April 2003

AbstractPolyaryl esters of moderate molecular weights were prepared by the direct polycondensation reaction of hydroxybenzoic acids and its derivatives with hexachlorocyclotriphosphatriazene (also known as phosphonitrilic chloride trimer, PNC) as a condensing agent in pyridine. Copolymerization of p‐hydroxybenzoic acid with several hydroxybenzic acid derivatives was carried out to improve the processability of the polymer of p‐hydroxybenzoic acid, which yields fusible and soluble copolymers of high inherent viscosities. Polymer solubility and thermal behavior were examined.
Effect of initiation conditions on the direct polycondensation reaction using triphenyl phosphite and pyridine
Authors: Higashi Fukuji , Taguchi Yuji , Kokubo Nobuyuki , Ohta Hidemi 
Published: April 2003

AbstractIn a model reaction of terephthalic acid with aniline by using triphenyl phosphite in a mixed solvent of pyridine and N‐methylpyrrolidone (NMP), mono‐ and dianilides were produced with relative yields varying with the content of pyridine in the solvent. The polycondensation of terephthalic acid with aromatic diamines was found to proceed more favorably via monoamidation, and highmolecular‐weight polyterephthalamides were prepared by controlling initiation conditions (selective activation of carboxylic groups), such as initial solvent systems, including the amount and kind of pyridines and initiation temperatures.
ESCA studies of natural weathering phenomena at selected polymer surfaces
Authors: Dilks A. , Clark D. T. 
Published: April 2003

AbstractESCA is used to characterize the surfaces of high and low density polyethylenes, nylon‐6,6, polyphenylene oxide, and polysulfone after exposure to the environment. Reactions that lead to degradation of the polymer surfaces can be detected straightforwardly and are discussed in terms of the known reactions found in the bulk polymers under similar conditions. The degree of surface oxidation is a strong function of polymer structure. The relative roles of different regions of the solar spectrum and other ambient conditions are examined by comparing the weathering characteristics in three mounting configurations.
Cationic polyelectrolytes. IV. Kinetic study of the reaction of acrylic polymers containing tertiary amine groups with halogenated compounds in dipolar aprotic solvents
Authors: Drăgan Stela , Petrariu I. , Dima M. 
Published: April 2003

AbstractThe reaction kinetics of halogenated compounds with tertiary amine groups attached at an acrylic macromolecular chain have ben studied. Three acrylic polymers were used. Two of them have mainly a structural unit of N, N‐dimethylaminopropylacrylamide and the third is poly(N,N‐dimethylaminoethylmethacrylate). Dimethylformamide, dimethylacetamide, and dimethylsulfoxide (DMSO) were used as dipolar aprotic solvents. Benzyl chloride and allyl chloride were considered as halogenated compounds with increased reactivity. The reaction kinetics depend on the polymer and halogenated‐compound structures as well as the nature of the solvent. In the most of the cases the reactions carried out on polymers are accompanied by self‐accelerating processes, with the exception of DMSO, which obviously has normal second‐order kinetics. The reaction of polymers containing units of N,N‐dimethylaminopropylacrylamide are compared with one having a low molecular weight, for instance N,N′‐bis(3‐dimethylaminopropyl)glutaramide.
Models for polyesterification kinetics. I. Esterfication kinetics in polar medium
Authors: Fradet Alain , Marechal Ernest 
Published: April 2003

AbstractThe kinetics of the reaction of 1‐octadecanol with octadecanoic acid and w‐carboxy polyxyethylene with w‐hydroxy polyoxyethylene in the absence of a cataylst were studied as models of polyesterification. Both rreactions are third order. Order two in acid and one in alcohol have been experimentally established by studies of nonstoichiometric systems. These results are not in agreement with recent work related to polyesterification kinetics. The mechanism involves autocatalysis by the acid and the presence of nondissociated ion pairs. Activation enthalpies and entropies are given.
Effect of monomer functional groups on the composition of some three component random phenolic copolymers
Authors: Chatterjee S. K. , Pandith R. L. , Pachauri L. S. 
Published: April 2003

AbstractSome three‐component random phenolic copolymers were prepared from three typical phenolic monomers; for example, p‐chlorophenol, p‐aminophenol, and p‐cresol. Several samples of the copolymer were prepared by changing the feed composition and the composition of the copolymers was established by estimating NH2 and OH groups by electrometric titration techniques in nonaqueous media. Halogen was estimated by Volhard's method. The average degree of polymerization (DP) of the copolymers was calculated from the features of the electrometric titration curves, and the effects of monomer functional groups on the composition of the copolymers were interpreted in terms of the electron‐donating and electron‐attracting nature of the substituents present in the monomers.
Photoregulated binding ability of azoaromatic polymer for surfactant
Authors: Ishihara Kazuhiko , Negishi Naoki , Shinohara Isao 
Published: April 2003

AbstractWater‐soluble polymeric azodyes containing an azobenzene moiety in their side chain, p‐phenylazoacrylanilide (PAAn)–acrylamide (AAm) copolymers, were synthesized and the adsorption‐desorption behavior of sodium dodecyl sulfate (SDS) onto these copolymers in water was investigated by means of conductivity measurements, with attention to the hydrophobicity of the copolymer. The conductivity of the PAAn‐AAm copolymer/SDS complex aqueous solution decreased with increasing PAAn composition in the copolymer. This result indicates that the SDS molecules adsorbed onto the copolymer. The adsorption state of SDS molecules on the copolymer was considered to take a micellelike form. When the hydrophobicity of the PAAn‐AAm copolymer was decreased by means of the photoisomerization of an azodye moiety, the conductivity of the PAAn‐AAm copolymer/SDS aqueous solution increased. This phenomenon can be explained as a result of desorption of SDS molecules from the copolymer. When the light source was cut off, the conductivity took on its original value. This indicated that SDS was desorbed by the photochemical trans to cis and adsorbed by cis to trans isomerization of the PAAn moiety.
ESR studies of some γ‐irradiated organic crystals
Authors: Kiliç Soner , Baysal Bahattin M. 
Published: April 2003

AbstractAcrylamide, N‐tert‐butylacrylamide, and propionamide crystals were irradiated at −196°C and the structures of radicals studied by ESR spectroscopy at various temperatures. The γ‐irradiated acrylamide crystals show a five‐line spectrum which is similar in shape to the signal obtained from the γ‐irradiated propionamide crystals. Two types of radicals are produced in irradiated acrylamide and propionamide crystals at −196°C. When the irradiated samples are kept at −78°C the spectrum of propionamide remains the same, except in intensity. In contrast to this, the acrylamide spectrum changes to a triplet because of dimerization. Upon warming the irradiated acrylamide sample to between −50 and −30°C, some small new peaks become apparent on either side of the triplet. These new peaks disappear above −20°C and the spectrum changes to a triplet because of polymerization. To observe the changes in the ESR spectra of γ‐irradiated N‐tert‐butylacrylamide we kept the sample at various temperatures from −196 to 100°C. From −196°C to about room temperature the spectrum is a quintet. At and above 35°C, the spectrum changes to a triplet with shoulders on either side of the main peaks. With further warming above 80°C the spectrum changes to a broad triplet.
The chemistry and kinetic behavior of Cu‐Cr‐As/B wood preservatives. I. Fixation of chromium on wood
Authors: Pizzi A. 
Published: April 2003

AbstractThe kinetic behavior of CrO3 in its reaction with wood has been elucidated. Various reactions take place between CrO3 and the lignin and cellulose in wood. CrO3 reacts with cellulose in a two‐step reaction: the first step is an adsorption of CrVI onto the cellulose to form CrVI/cellulose activated complexes. The second step is a CrVI → CrIII reduction taking place on the cellulose surface. The CrIII formed is only physically adsorbed to the cellulose or very weakly bound as small amounts of CrIII can be released into the reaction medium. The CrVI adsorbed by cellulose appears mainly to be reduced to CrIII. The reaction of CrVI with lignin has been shown to be the composition of the three successive reaction of Cr2O72−, HCrO4−, and CrO42− with the guaiacyl units of lignin. Insoluble and stable CrVI/lignin complexes in which chromium maintains its hexavalent oxidation state are formed. Rate constants and energies of activation for all the reactions have been determined. The fixation of CrO3‐derived compounds on wood has been explained as the combination of the various reactions investigated. The results indicate that 60% of Cr is fixed irreversibly to the lignin of wood as CrVI and 40% is weakly bound, probably just precipitated, on the cellulose surface as CrIII of which small amounts can be released in a water medium. The complex CrVI and CrIII species forming complexes with the guaiacyl units have been identified.
Ce(IV)‐induced polymerization of allyl methacrylate with cotton cellulose
Authors: El‐Alfy E. , Khalil M. I. , Hebeish A. 
Published: April 2003

AbstractCe(IV)‐induced polymerization of allyl methacrylate (AMA) with cotton cellulose was investigated under a variety of conditions. Polymer add‐on was directly related to AMA concentration. The same holds good for Ce(IV) ion concentration up to a certain concentration (30 mmol/L), after which it decreases. Polymer add‐on was higher at 60 than at 50 and 70°C. A methanol/water mixture (20/80) offers the best medium for polymerization. Addition of nitric acid (up to 400 mol equivalent/L) or perchloric acid (up to 800 mol equivalent/L) to the polymerization system caused significant enhancement in polymer add‐on. The reverse was the case with sulphuric acid irrespective of the concentration used. A comparison between polymer add‐on values based on increase in weight and those based on estimated allyl double bonds indicated that the latter undergo partial homopolymerization.
Chemical structure of poly(trisubstituted vinylsilane) produced by γ irradiation
Authors: Hayakawa Kiyoshi , Kawase Kaoru , Yamakita Hiromi , Yumoto Takaari 
Published: April 2003

AbstractThe chemical structure of polymers produced by the γ irradiation of monovinylsilanes was studied. γ‐ray addition polymerization of monovinylsilanes such as trialkylvinylsilane was very slow, and only the liquid oligomers were formed from them by large radiation dose. The presence of silethylene or silmethylene linkage was ascertained in these polymers by infrared absorption spectroscopy and 1H‐NMR measurement, even when no SiH bond existed in the monomers. The polymers were supposed to be produced by addition polymerization with intervening silalkylene linkage.
Small‐angle X‐ray scattering of air‐dried kangaroo tail tendon
Authors: Misra T. , Patra K. C. , Patel T. 
Published: April 2003

AbstractAir‐dired kangaroo tail tendon (KTT) is a protein sample similar to collagen and has been investigated by small‐angle x‐ray scattering treating it as a densely packed colloidal system which belongs to a general micelle system. Pore analysis of the substance yields a specific inner surface of 0.6282 × 10−5 Å−1, a range of inhomogeneity of 69.11 Å, a length of coherence of 248.2 Å, and air‐fraction percentage of 0.011. A Kratky camera of the latest design has been used for experimental measurements. As the logĨ vs. logX curve gives a slope of −3, KTT belongs to a densely packed two‐phase system. Here the theory of small‐angle scattering by densely packed systems as developed by Porod has been applied to find different physical parameters of KTT.
Thermal decomposition of polybutadienes by pyrolysis gas chromatography
Authors: Radhakrishnan T. S. , Rao M. Rama 
Published: April 2003

AbstractThe thermal decomposition of cis‐1,4‐, trans‐1,4‐, and 1,2‐polybutadienes (PBD) in the temperature range 450–900°C was investigated by pyrolysis gas chromatography (PGC). The cis‐ and trans‐PBDs have closely similar product distribution and can be readily distinguished at lower temperatures of pyrolysis from the 1,2‐PBD by the low amount of vinyl cyclohexene (VCH) produced by the 1,2 species. The amount of butadiene (BD) produced by 1,2‐PBD varies with the tacticity of the polymer; the greater syndiotactic yields a lesser amount of BD. A method of determining the 1,4 and the 1,2 contents of PBD based on the ratios of peak heights of ethylene (C2) to VCH, propylene (C3) to VCH, and BD to VCH is presented. The advantages of this method are discussed. The nature and composition of the products of pyrolysis in the temperature range 540–900°C are presented and the mechanism of degradation at these elevated temperatures is explained.