bluuebunny/crossref_metadata_2025 huggingface dataset:
On the role of oxygen in the horizontal flame spread of polypropylene
Authors: Jakes K. A. , Drews M. J.
Published: April 2003

The 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

The 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

In 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

New 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

The 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

A 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

A 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

The 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

This 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

Polyaryl 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

In 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

ESCA 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

The 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

The 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

Some 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.
A new method for reactivity ratios calculation
Authors: Chen Func Bor , Bufkin B. G.
Published: April 2003

A new method is proposed to calculate the reactivity ratios based on the polynomial approximation of unreacted monomers during the reaction period. From the published data of Meyer the reactivity ratios were recalculated in reasonable agreement with the original author.
Photoregulated binding ability of azoaromatic polymer for surfactant
Authors: Ishihara Kazuhiko , Negishi Naoki , Shinohara Isao
Published: April 2003

Water‐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

Acrylamide, 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

The 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

Ce(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

The 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

Air‐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

The 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.
Multifunctional polycondensation and gelation: A kinetic approach
Authors: Stafford J. W.
Published: April 2003

The size distributions of a number of multifunctional polycondensation systems have been derived from kinetic reaction schemes. The size distribution obtained for a self‐condensing multifunctional monomer is equivalent to the classic distributions derived by Flory and Stockmayer, and distribution expressions for mixtures of monomers of different functionalities have also been obtained. Molecular weight expressions have also been calculated for the same systems. In some case, these are exactly the same as those calculated by others, and in some cases the expressions differ from those by others only in the kind of average used for the mean functionality of the mixed monomer systems, but in other cases, the differences are more marked. In gelation, comparison with a number of actual gel point data shows that although the critical point Pcrit for gel formation calculated from Pcrit = 2/f was generally closer to actually measured gel points than when Pcrit = 1(f –1), neither method of calculating Pcrit can be regarded as completely reliable. The cause of the divergence from theory is interpreted in terms of intramolcular reaction, and the nature of this type of reaction is discussed and comparisons made with other gelling systems.
The nonaqueous, potentiometric titration of free hydrochloric acid in chloride‐containing polymers
Authors: Reigler Paul F. , Larson Jeff , Bowman Lyle
Published: April 2003

The thermal and/or catalytic degradation of chloride‐containing polymers causes dehydrohalogenation which produces hydrochloric acid. A nonaqueous method has been developed for the termination of hydrochloric acid. The sample is dissolved in tetrahydrofuran and titrated potentiometrically with a standard tetrabutylammonium hydroxide solution in a 7.5% (V/V) aqueous tetrahydrofuran solution with a combination glass‐calomel electrode. The method has a relative precision of ±3.7% at the 95% confidence limit and a sensitivity of 25 ppm HCI.
Functional polymers. XIV. Grafting of 2(2‐hydroxy‐5‐vinylphenyl)2H‐benzotriazole onto polymers with aliphatic groups
Authors: Pradellok Witold , Vogl Otto , Gupta Amitava
Published: April 2003

Successful grafting of 2(2‐hydroxy‐5‐vinylphenyl)2H‐benzotriazole onto saturated aliphatic CH groups of polymers has been accomplished. When the grafting reaction was carried out in chlorobenzene at 150–160°C with di‐tertiary butylperoxide as the grafting initiator, grafts as high as 20–30% at grafting efficiencies of 50 and 80% have readily been obtained. It was very important to carry out the grafting reaction in tubes sealed under high vacuum since trace amounts of oxygen cause complete inhibition of the grafting reaction by the phenolic monomer. Grafting reactions were carried out on a variety of different polymers including atactic polypropylene, ethylene/vinyl acetate copolymer, poly(methyl methacrylate), poly(butyl acrylate), and polycarbonate.
Methylene malonamide. I. Synthesis and reactivity of the monomer
Authors: Jasne S. J. , Haas H. C. , Moreau R. D. , MacDonald R. L.
Published: April 2003

The first confirmed synthesis of methylene malonamide (MeMal) is reported. This monomer was prepared by the thermal elimination or fluoride‐ion‐initiated elimination of trimethylsilyl chloride from α‐chloro‐α(trimethylsilyl‐2‐methyl) malonamide. Spectral data for the monomer are given. MeMal has been shown to be unstable in a variety of protic organic solvents, including water and alcohols, thus giving the appropriate (α‐methyl) substituted malonamides. MeMal is stable in most aprotic solvents.
Polymerization of acrylonitrile. Kinetics of the reaction initiated by the Ce(IV)/thioacetamide redox system
Authors: Samal Rajani K. , Nayak M. C. , Panda G. , Suryanarayana G. V. , Das D. P.
Published: April 2003

Vinyl polymerization of acrylonitrile initiated by the Ce(IV)/thioacetamide redox system has been investigated in aqueous sulfuric acid in the temperature range of 10–20°C. The rate of polymerization (Rp) and the rate of Ce(IV) disappearance (−RCe) were measured. The effect of certain water‐soluble organic solvents, added electrolytes, and aromatic and heterocyclic organic nitrogen compounds on the rate of polymerization has been investigated. Depending on the experimental results, we have suggested a suitable reaction scheme for the system which involves the production of initiating radicals from the oxidation of thioacetamide (TAm) by ceric ion and the termination of the polymer chain by metal ions.
Kinetics and mechanism of HCN evolution from nylon 66 and design of apparatus
Authors: Jellinek H. H. G. , Dunkle S. R.
Published: April 2003

The evolution of HCN from the oxidation of nylon 66 has been studied in three apparatuses of different design (all based on stream flow) over a temperature range from 390 to 700°C. Although the numerical values for rate constants (diffusion controlled) and energies of activation differ, the same mechanism is deduced from the results of the three designs. It is concluded that a simple horizontal tube in a furnace is the most efficient apparatus as far as sweeping out volatile products is concerned. The mechanism of thermal oxidative degradation has been evaluated in detail. It is shown that mechanisms where the first reaction step is not the slowest or the slowest one of first or second order all fit the experimental results. However, it is concluded that the mechanism where the first step is first order and the slowest one is the most likely one. The respective parameters have been evaluated for the results obtained from the horizontal tube apparatus.
Reduction of electroactive polymers via polyelectron transfer processes at solid electrodes
Authors: Funt B. Lionel , Hsu Li‐Chien , Hoang P. M. , Martenot J. P.
Published: April 2003

The reduction of an electroactive polymer at an electrode involves the transfer of a large number of electrons to a single molecule. A quantitative study of this process indicates whether the system behaves ideally. The electron transfer process in polyvinylbenzophenone and in polyvinylbenzophenone‐co‐styrene in N,N‐dimethylformamide solution was investigated by voltammetry at a rotating disk electrode. It is concluded that benzophenone (BP) groups attached to the polymer backbone are noninteracting electroactive centers and that every BP group is reducible at the electrode. The relationship between limiting current and molecular weight was examined quantitatively for a series of polymers of low dispersity with molecular weights ranging up to 300,000, and with a controlled, varied content of electroactive groups. The diffusion coefficient was determined as a function of molecular weight from the electrochemical data, and was found to be in good agreement with the theoretical model based on transport properties. The dependence of the diffusion coefficient on concentration of polymer and on temperature were investigated and activation energies determined.
Regular copolymers derived from bis(2‐oxazolines). II. Synthesis of polyamides and polyamide‐imides containing oxyethylene linkages
Authors: Chau Nguyen , Muramatsu Taeko , Iwakura Yoshio
Published: April 2003

New diamines containing amide and oxyethylene linkages were prepared by reduction of the corresponding dinitro compounds which were obtained by the reaction of p‐nitrophenol with arylenebis(2‐oxazolines) in dimethylformamide at 130°C. Moderate‐ to high‐molecular‐weight polyamides and polyamide‐imides containing oxyethylene linkages were prepared by the polycondensation of the diamines with diacid chlorides and tetracarboxylic acid dianhydrides, respectively. The polyamides were soluble in dimethylacetamide containing 5% of lithium chloride and dichloroacetic acid, while the polyamide‐imides dissolved only moderately in the latter solvent. Thermogravimetric analysis showed that thermo‐oxidative decomposition started at 310–330°C and at around 325°C for the polyamides and polyamide‐imides, respectively.
Photocrosslinking and photografting of vinyl polymers using poly(styrene‐co‐p‐vinylbenzophenone‐p′‐tert‐butyl perbenzoate) as a comonomer
Authors: Gupta I. , Gupta Satyendra N. , Neckers Douglas C.
Published: April 2003

Styrene has been copolymerized with low percentages of p‐vinylbenzophenone‐p′‐tert‐butyl perbenzoate (VBPE). The resulting copolymer has been used to make graft copolymer with methyl methacrylate using UV irradiation (366 nm). The grafting efficiency has been observed to increase with time of irradiation and percentage of VBPE in the copolymer. The copolymer has also been observed to crosslink efficiently with photochemical irradiation.
Nylon 6–polyisobutylene sequential copolymers. II. Synthesis, characterization, and morphology of di‐, tri‐, and radial block copolymers
Authors: Wondraczek Reinhard H. , Kennedy Joseph P.
Published: April 2003

Nylon 6–PIB diblock, triblock, and tristar radial block copolymers have been synthesized from telechelic hydroxyl‐terminated polyisobutylene, PIB(OH)n (n = 1,2,3), by conversion of this prepolymer with hexamethylene diisocyanate (HMDI), toluene diisocyanate (TDI), N‐chlorocarbonyl diisocyanate (NCCI), and oxalyl chloride (OxCl) and using the resulting materials as macroactivators for anionic caprolactam polymerization. Prepolymers with molecular weights from 6000 to 38,000 have been employed. Derivatization with NCCI and subsequent anionic caprolactam polymerization gave highest yields and blocking efficiencies. The block copolymers have been characterized by molecular weight and composition. In addition to the expected Tg and Tm characteristics of long PIB and nylon 6 segments, DSC studies showed an intermediate glass transition at ca. −20°C. Transmission electron microscopy of di‐, tri‐, and radial blocks show increasing segregation and orientation of rubbery/crystalline domains. Tensile strengths and elongations of the block copolymers range from 16.5 to 41 MPa and 15 to 30%, respectively, and stress‐strain diagrams show the effect of block architecture on these properties.
Cu (DPM)2–initiated vinyl polymerization
Authors: Chatterji Prabha R. , Nandi Uma S.
Published: April 2003

The behavior of cupric dipivaloylmethide in vinyl polymerization systems was investigated with a view to understanding the mechanism of polymerization initiation. Results of polymerization reactions together with spectral investigation data are presented. Polymerization in the presence of the chelate proceeds through a free‐radical process. The corresponding kinetic and transfer constants and activation energy values suggest a normal propagation step. With the help of spectral data an attempt is made to suggest a plausible mechanism of initiation.
Reactivity ratios of ethyl acrylate, n‐butyl methacrylate copolymer system by 1H‐NMR
Authors: Pitchumani S. , Reddy C. Rami , Rajadurai S.
Published: April 2003

Ethyl acrylate (EA) and n‐butyl methacrylate (n‐BMA) copolymers were prepared in solution and the composition of the copolymer samples was estimated by 1H‐NMR spectroscopic techniques. Because the characteristic signals, which vary with the composition of the copolymer, were absent, the ratio of intensities of down‐field protons to that of the total protons was used for the estimation of copolymer composition. Reactivity ratios were calculated from these values by using the Kelen‐Tudos differential linear equation.
Synthesis and thermal characteristics of bisimides. I
Authors: Varma Indra K. , Fohlen George M. , Parker John A.
Published: April 2003

Ten structurally different bisimide resins were prepared by reacting maleic anhydride/citraconic anhydride and benzophenone tetracarboxylic dianhydride with aromatic diamines and fused aromatic structures or heterocyclic groups. The amines included were 1,5‐diaminonaphthalene, 2,5‐bis(p‐aminophenyl)1,3,4‐oxadiazole, 3,3‐bis(p‐aminophenyl)phthalide, 9,9‐bis(p‐aminophenyl)fluorene. and 10,10‐bis(p‐aminophenyl)anthrone. These monomers were characterized by infrared (IR). 1H‐NMR, mass spectroscopy, and elemental analysis. Thermal polymerization of these monomers was investigated by differential scanning calorimetry. Broad exothermic peaks were observed for a temperature range of 225–380°C. Temperature of exothermic peak position was influenced by the presence of substituents at the olefinic bond, and in biscitraconimides it was 40–50°C lower than in the corresponding bismaleimides. Anaerobic char yields of cured bisimide resins ranged from 44 to 64%. Oxadiazole‐containing bisimides had low thermal stability. Increase in formula weight between the imide groups did not influence the char yields in a systematic manner. Graphite cloth laminates with two of these bisimide resins were fabricated and tested for a number of physical properties. Their limiting oxygen index was 70–72%.
Preparation of phosphorus‐containing polymers. XXVII. Polyester‐imides that contain phenoxaphosphine rings
Authors: Sato Moriyuki , Kondo Hitoshi , Yokoyama Masaaki
Published: April 2003

New phenoxaphosphine‐containing polyester‐imides were prepared by the interfacial polycondensation of a dichloroformyl‐phenoxaphosphine derivative containing a preformed imide ring with five bisphenols. The polymerizations, which were carried out in a chloroform‐aqueous sodium hydroxide mixture, afforded polyester‐imides with reduced viscosities of 0.60–1.55 dL/g in 61–95% yields. The preformed imide ring did not undergo hydrolysis under the polymerization conditions. Several of the polymers were soluble in chloroform and could be cast into flexible and transparent films. The phenoxaphosphine‐containing polyester‐imides have good thermal properties, exhibiting little decomposition below 400°C. They appear to be more thermally stable than phenoxaphosphine‐containing polyesters, but are not as thermally stable as the corresponding polyimides and polyamide‐imides. The order of thermal stability for phenoxaphosphine‐containing polymers in air is polyimide ≳ polybenzoxazole > polyamide‐imide ≳ polybenzimidazole > polyester‐imide > poly‐1,3,4‐oxadiazole ≳ polyamide > polyester. The polyester‐imides exhibited self‐extinguishing behavior.
Syntheses of 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl‐β‐D‐altropyranose and of 1,6‐anhydro‐2‐0‐benzyl‐3,4‐0‐isopropylidene‐β‐D‐galactopyranose and their ring‐opening copolymerizations with 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl (or p‐methylbenzyl)‐β‐D‐glucopyranose
Authors: Uryu Toshiyuki , Hatanaka Kenichi , Yoshinari Kaoru , Matsuzaki Kei
Published: April 2003

The cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl‐β‐D‐altropyranose (TBLAT, M2) failed to give the fourth stereoregular 1,6‐α‐linked polysaccharide because of its very low homopolymerizability. However, the 1,6‐anhydro‐altrose monomer was found to copolymerize with 1,6‐anhydro‐2,3,4‐tri‐0‐(p‐methylbenzyl)‐β‐D‐glucopyranose (LGTXE, M1) with PF5 as catalyst at low temperature, giving highly stereoregular copolymers. The monomer reactivity ratios calculated by Kelen‐Tüdös method were r1 = 1.52 and r2 = 0.06. The differences in the reactivity between TBLAT monomer and other 1,6‐anhydro sugar derivatives are discussed. Moreover, 1,6‐anhy‐dro‐2‐0‐benzyl‐3,4‐0‐isopropylidene‐β‐D‐galactopyranose (ABIGA, M4), which showed no homopolymerizability under various conditions, was also copolymerized with 1,6‐anhydro‐2,3,4‐tri‐0‐benzyl‐β‐D‐glucopyranose (LGTBE, M3) at low temperature. The monomer reactivity ratios of r3 = 2.2 and r4 = 0.0 indicate that in the copolymers every galactose unit distributed as a single unit through the main chain. The cause for the lower polymerizability of ABIGA is discussed. Hydrolysis of the copolymer with trifluoroacetic acid gave a copolymer in which only galactose units contained free hydroxyl groups, which were then methylated by methyl iodide. Stereoregular 1,6‐α‐linked galactoglucan composed of free sugar units was prepared by debenzylation of the ABIGA‐LGTBE copolymer followed by hydrolysis.
X‐ray structure determination of new monomers to establish their polymerizability: Copolymerization of two tetrasubstituted electrophilic olefins with electron‐rich styrenes giving polymers with an average 1.25 functional groups per chain carbon atom
Authors: Hall H. K. , Reineke K. E. , Ried J. H. , Sentman R. C. , Miller D.
Published: April 2003

X‐Ray crystal structure determination for two tetrasubstituted electrophilic olefins, tetramethyl ethylenetetracarboxylate TMET and dimethyl dicyanofumarate DDCF, revealed two fundamentally different molecular structures. TMET is a nonplanar molecule that possesses two opposite ester groups planar and the others above and below the molecular plane. In contrast, DDCF is a molecule for which both ester groups lie in the plane of the double bond and nitrile groups. DDCF underwent thermal spontaneous copolymerization with electron‐rich styrenes to give 1:1 alternating copolymers in moderate yields and molecular weights. These copolymers, which result from the first copolymerizations of a tetrasubstituted olefin, possess an average functionality of 1.25 per chain carbon atom. Polymerization is made possible by low steric hindrance and the high delocalization in the propagating radical. The yields were limited by competing cycloaddition reaction. The corresponding diethyl ester also copolymerized, but not so well. Neither electrophilic olefin homopolymerized under γ‐irradiation. TMET did not copolymerize at all when treated under identical conditions.
Nematogenic block copolymers via the yamazaki reaction
Authors: Asrar J. , Preston J. , Ciferri A. , Krigbaum W. R.
Published: April 2003

A novel extension of the Yamazaki reaction is used to prepare block copolymers having rigid blocks of poly‐(p‐benzamide) (PBA) and semiflexible blocks of polyamide‐hydrazide. A PBA prepolymer having M ≅ 10,000 was synthesized by the usual Yamazaki reaction using triphenylphosphite. As previously reported, higher‐molecular‐weight PBA could be obtained using 4‐N‐(4′‐aminobenzamido)benzoic acid containing a preformed amide linkage. Addition of p‐aminobenzhydrazide and terephthalic acid then led to formation of the polyamide‐hydrazide blocks using as the active reactant the diphenylphosphite formed as a by‐product in the first polymerization. Evidence that a block copolymer is produced includes an increase in inherent viscosity during the second step, differences in the solubility of the copolymer compared to the homopolymers, and comparison of the phase diagram of the block copolymer in N‐methylpyrrolidone having 4% added LiCl with those of a random copolymer, and of mixtures of the two homopolymers. The critical concentration required to form a nematic phase in solutions of the block copolymers is correlated with the length (or axial ratio) of the rigid block, and with its proportion in the copolymer.
New processable polyaromatic ether‐keto‐sulfones as colorless, clear film‐forming materials
Authors: Lee Byung H. , Marvel C. S.
Published: April 2003

New processable polyaromatic ether‐keto‐sulfones were prepared from 4,4′‐diphenoxydiphenyl sulfone, terephthaloyl chloride, isophthaloyl chloride, and bis‐p‐carboxyphenylacetylene dichloride (IV) in a Friedel‐Crafts‐type polymerization. The white polymers obtained form colorless, transparent, strong films and can be cast into a glass‐fiber laminate. One polymer was prepared which incorporated biphenylene‐2,6‐dicarboxylic acid dichloride as crosslinking sites; this heat‐cured polymer was completely insoluble in sulfuric acid.
Determination of rate constants of benzoyl peroxide and azobisisobutyronitrile dissociation via polymerization kinetics
Authors: Ng S. C. , Chee K. K.
Published: April 2003

A linear expression is derived from Tobolsky's equation related to the dead‐end polymerization method to determine the rate constant for the initiator dissociation. This novel graphical method applies remarkably well to the kinetic data collected by dilatometry from the polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile and benzoyl peroxide in toluene at 60°C. Results obtained for these two initiators are consistent with those published in the literature. Applicability of the method is confined to at least 5% and at most 13% decomposition of initiator. However, these limiting values are sensitive to the experimental techniques employed. The effects of induced decomposition of benzoyl peroxide and thermal polymerization of methyl methacrylate are shown to be negligible in the present investigations.
Nonionic polymer surfactants
Authors: Landoll L. M.
Published: April 2003

Nonionic water‐soluble polymeric surfactants have been prepared by addition of long‐chain n‐alkyl epoxides to nonionic cellulose ethers. The polymers exhibit properties which can be explained by interchain association. The relationship between hydrocarbon‐modifier carbon number and the onset of association follows a linear relation analogous to those observed for monomeric nonionic surfactants.
Acid‐base properties of solid polyelectrolytes: Dissociation of cellulosic polyanions
Authors: Shet R. T. , Atanu E. Y.
Published: April 2003

The potentiometric titration behavior of nitrogen dioxide and periodate‐chlorite oxycellulose has been studied both in the presence and absence of sodium chloride. The apparent pK values in general increase with increasing degree of dissociation, but the reverse is true for periodate‐chlorite oxycellulose in the absence of added salt. This behavior is interpreted in terms of electrostatic and hydrogen bonding interaction of carboxyl groups. The Gibbs–Donnan theory of polyaid dissociation was applied to calculate the intrinsic dissociation constant pK′0. Assuming a model having a uniform potential distributin throughout the fiber, good agreement with the expected value of 3.24 was found (compared to pK′0 = 3.25 calculated for periodate‐chlorite oxycellulose).
Emulsion polymerization of styrene: Nucleation studies with nonionic emulsifier
Authors: Piirma Irja , Chang Manchium
Published: April 2003

The nucleation mechanism of styrene emulsion polymerization in the presence of the nonionic surfactant Emulphogene BC‐840 was investigated. It was found that the conversion‐time curves of this system show two rate regions. The change in rate occurs at ca. 40% conversion. Second‐stage nucleation leads to a faster rate and consequently to a bimodally dispersed latex. The particle size distribution is relatively narrow before 40% conversion. The bimodally dispersed latex shows a bimodal molecular weight distribution in gel permeation chromatography and the results from fractional “creaming” of the latex indicate that the small‐size particles contain the higher‐molecular‐weight polymer.
A study of the spectra of diacetylenic phospholipid polymers in solvents and dispersions
Authors: Pons Miquel , Johnston David Samuel , Chapman Dennis
Published: April 2003

Phospholipids, of which phosphoryl cholines are a specific example, are the most common lipid components of cell membranes. Synthetic acetylenic phospholipids form closed model membranes, vesicles, or liposomes when dispersed in water. Below the temperature at which lipid chain crystallization occurs irradiation of vesicles causes polymerization of the diacetylene groups. In chloroform solution the spectrum of the polymer is independent of temperature. However, when the polymer is dissolved in methanol or dispersed in water with another lipid spectral changes occur. As solution or dispersion is cooled a second peak appears on the long wavelength side of the original absorption and gradually increases in intensity. Evidence that suggests that this peak is associated with aggregated polymer chains is presented. It appears that within the aggregates exciton coupling splits the excited state into two new levels and only transitions to the level of lowest energy are allowed.
γ Radiolysis of poly(4,4′‐isopropylidene diphenylene sebacate)
Authors: Gupta Mool C. , Srivastava Ashok K.
Published: April 2003

Poly‐(4,4′‐isopropylidene diphenylene sebacate) (PIDPS), a condensation product of bisphenol‐A and sebacic acid, was irradiated with 60Co γ rays. Viscosity, end‐group analysis, and IR spectral measurement techniques were used to study the chemical changes occurring during γ radiolysis. It is observed that PIDPS undergoes random chain scission owing to weak links which may be present or be incorporated by the oxygen from air. The G value of random chain scission is estimated to be 9, whereas the enthalpy of fusion is found to be 6.2 kcal/mol repeat unit of PIDPS.
Polyaromatic ether‐ketones containing various biphenylene units as crosslinking sites
Authors: Sutter A. , Schmutz P. , Marvel C. S.
Published: April 2003

Polyaromatic ether‐ketones were prepared from diphenyl ether, isophthaloyl dichloride, and small amounts of 2,6‐, 2,7‐, 1,5‐, and 1,8‐dicarboxylic acid chloride of biphenylene, respectively, by Friedel–Crafts reaction. Biphenylene units were incorporated as crosslinking sites. Crosslinking is achieved by curing the polymers at 310–350°C for several hours. While the uncured resins are soluble in concentrated sulfuric acid, the fully crosslinked polymers are completely insoluble.