bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal behavior of holo‐ and hemicellulose obtained from rice straw and bagasse
Authors: Sefain Magdi Z. , El‐Kalyoubi Samira F. , Shukry Nadia 
Published: April 2003

AbstractThermal gravimetric analysis, and differential thermal behavior of holo‐ and hemicelluloses obtained from rice straw and bagasse were investigated. Degradation was found to be of first order reaction. The activation energy values and the rate constants were calculated from the kinetic of weight loss. Hemicellulose was found to be less stable than holocellulose, and the stability of the samples was arranged in the order, rice straw holo‐ > bagasse holo‐ > rice straw hemi‐ > bagasse hemicellulose. Degradation of rice straw (holo‐ as well as hemicellulose) was performed via two exothermic processes, whereas bagasse hemicellulose combustion was completed through three exothermic processes. The magnitude and the shape of the exotherms depend, mainly, on the chemical composition of the sample.
Preparation and characterization of poly(copper 2,3,9,10,16,17,23,24‐octacyanophthalocyanine)
Authors: Lin John W‐P. , Dudek Les P. 
Published: April 2003

AbstractDark blue poly(copper 2,3,9,10,16,17,23,24‐octacyanophthalocyanine) has been prepared by reacting 1,2,4,5‐tetracyanobenzene with cuprous chloride in 1‐methyl‐2‐pyrrolidone at ca. 150°C. The product has been characterized by elemental analysis, thermal analysis, infrared and UV‐VIS spectroscopies. The polymer has high purity and exhibits good thermal stability in an inert atmosphere.
An ESCA investigation of the inductively coupled RF plasma polymerization of fluoronaphthalene and fluoronaphthalene/hydrogen mixtures
Authors: Munro H. S. , Till C. 
Published: April 2003

Abstract1‐Fluoronaphthalene was plasma polymerized and its composition and structure, as a function of position, power, and temperature, were examined by ESCA. The F:C ratio of the deposited film was lower than that of the starting monomer both at room temperature and at 150°C. An asymmetry of the main C1s photoionization peak was noted. Plasmas were also excited in fluoronaphthalene/hydrogen mixtures where extensive fluorine elimination and hydrogen incorporation occurred. This gave direct evidence that the height of step function or asymmetry of the main C1s peak is related to the degree of saturation in the compound.
Polyetherimides. I. Preparation of dianhydrides containing aromatic ether groups
Authors: Takekoshi T. , Kochanowski J. E. , Manello J. S. , Webber M. J. 
Published: April 2003

AbstractA general synthetic method and characterization of bis(ether anhydride)s, the ether containing aromatic dianhydrides of the following structure, are presented.
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The method involves aromatic nitro‐displacement of N‐substituted 3‐ or 4‐nitrophthalimide with bisphenoxides to form N‐substituted arylene‐bis(phthalimido)ethers or bis(ether imide)s. Sixteen structurally different bis(ether imide)s have been prepared and subsequently converted to the corresponding bis(ether anhydride)s. Bis(ether anhydride)s are stable crystalline compounds of a moderate reactivity. Unlike highly reactive dianydrides such as pyromellitic and benzophenonetetracarboxylic dianhydrides bis(ether anhydride)s are semipermanently stable against hydrolysis in the presence of atmospheric moisture.
Conversion of solid poly(methyl vinyl ether‐alt‐maleimide) to poly(methyl vinyl ether‐alt‐maleic anhydride)
Authors: Field Nathan D. , Li Chi 
Published: April 2003

AbstractSolid poly(methyl vinyl‐alt‐maleimide), when subjected to heating at 100°C while being vacuum pumped at 0.1 mm Hg pressure, was converted to a copolymer in which a substantial portion of the imide groups were converted to anhydride groups. Similarly, heating at 100°C at atmospheric pressure in a circulating air oven brought about the same reaction but at a faster rate. This confirms the hypothesis that the formation of maleic anhydride comonomer units from poly(methyl vinyl ether‐alt‐ammonium maleamate) not only proceeds directly by ring closure of amic acid formed by loss of ammonia but probably also includes, as a parallel pathway, hydrolysis by atmospheric moisture of maleimide comonomer units.
Polyhalogenated polyamides IV. Synthesis and characterization of polyhalogenated polyamides in a melt–solid process at high temperature and in solution at low temperature
Authors: Díz F. R. , Tagle L. H. , Padilla M. E. 
Published: April 2003

AbstractA new series of polyhalogenated, principally polybrominated polyamides have been prepared either by polymerization in a melt‐phase process at high temperature or by a low‐temperature solution process. The polymers were obtained from perchloroterephthaloyl‐, perbromoterephthaloyl‐, and 2,5‐dibrometerephthaloyl dichlorides and tetrabromophthalic anhydride with aromatic and aliphatic diamines. They were characterized by elemental analysis, infrared spectroscopy, intrinsic viscosities, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and flame‐resistance testing.
Copolymerization of vinyl ketones with allylbenzene in the presence of zinc chloride
Authors: Masuda Seizo , Omochi Teruyuki , Ota Tadatoshi 
Published: April 2003

AbstractCopolymerization of 3‐buten‐2‐one (MVK) and 3‐methyl‐3‐buten‐2‐one (MIPK) with allylbenzene (AB) in the presence of zinc chloride (ZnCl2) was studied. The apparent monomer reactivity ratio decreased with an increasing concentration of ZnCl2 added. By assuming a terpolymerization system as free vinyl ketone (M1), vinyl ketone complexed with ZnCl2 (M2), and AB(M3), the absolute monomer reactivity ratios were determined by using the least squares method: k11/k12 = 0.0038, k11/k13 = 11.77, k22/k21 = 1.37, and k22/k23 = 3.77 for the MVK‐AB system, and k11/k12 = 0.0070, k11/k13 = 55.47, k22/k21 = 1.84, and k22/k23 = 11.16 for the MIPK‐AB system, respectively. It is seen from these values that the complexed vinyl ketones are more reactive to both polymer radicals which have free and complexed vinyl ketone units at its terminal position than the free vinyl ketones. Q and e values for MVK and MIPK complexed with ZnCl2 were found to be Q = 850, e(MVK)2ZnCl2 = 2.97, Q = 2.62, respectively.
The effect of temperature and solvent on the synthesis and properties of nylon 610 made from sebacyl bisketene
Authors: Garner David P. , Fasulo Paula D. 
Published: April 2003

AbstractPolyamides were synthesized at −60°, −40°, −20°, and 0°C from sebacyl bisketene and 1,6‐hexamethylenediamine in either acetone or methylene chloride. At the lower reaction temperatures oligomers predominated in solution but at 0°C the product was crosslinked. The polyamides were subjected to m‐cresol extraction at elevated temperatures for up to 14 days. The m‐cresol soluble and insoluble fractions were characterized by weight, infrared spectroscopy, dilute solution viscosity, and gel permeation chromatography. Infrared analysis of the soluble and insoluble portions showed the degree of branching of the polyamide, identified the branching point at the secondary amide proton position, and gave an indication of the degree of branching required before insoluble products resulted. Dilute solution viscosity and gel permeation chromatography were used to demonstrate the existence of low molecular weight (Mw) oligomer species in the soluble portion. Differential scanning calorimetry experiments revealed that polyamides synthesized below their glass transition temperature would not crystallize which resulted in abnormal thermal characteristics. Annealing at elevated temperatures allowed crystallization to occur and the expected thermal character to develop.
Polymerization of water‐in‐oil microemulsions: Methyl methacrylate, acrylic acid, and sodium acrylamidostearate
Authors: Chew C. H. , Gan L. M. 
Published: April 2003

AbstractWater‐in‐oil (w/o) microemulsions of methyl methacrylate (MMA), acrylic acid (AA), sodium acrylamidostearate (NaAAS), and water were investigated. MMA, AA, and NaAAS could be terpolymerized in these microemulsions. For a composition of 54% MMA, 34% AA, 2% NaAAS, and 10% H2O, polymers of high molecular weights of about 1,000,000 were obtained between 3.5 to 24% polymer conversion. The system became a transparent gel when conversion exceeded 36%. Transparent solid terpolymer containing water up to 16% were also obtained after fully polymerizations of certain compositions.
Further investigations into the formation of imide linkages during the amidation of mono‐ and difunctional aroxyacetyl chlorides
Authors: Clark A. J. A. , Lenk R. S. 
Published: April 2003

AbstractThis paper further investigates imide formation in amidation reactions involving Bischloride A2 and suitably selected mono‐ and difunctional analogues on the one hand, and primary aromatic mono‐ and diamines on the other. It also investigates the reaction of these acid chlorides with secondary mono‐ and diamines. If, say, N,N′ dimethyl p‐phenylene diamine and hydroquinone dioxyacetyl chloride or bischloride A2 were to react quantitatively, then a linear unbranched polyamide would be expected to be the result which, in the absence of any hydrogen remaining at the amide link, would no longer present a site for further electrophilic attack on the part of the exceptionally reactive aroxyacetyl chloride. There also arises the possibility that a monoamine such as aniline could conceivably act as a difunctional reagent in the presence of aroxyacetyl chlorides. In the event of this reaction proceeding quantitatively one would expect to obtain a linear polyimide in which each imide–nitrogen atom carries a phenyl group. In carrying out the experimental preparative work which is required to elucidate these points we used both monofunctional reactants as model compounds and difunctional reactants in order to assess the polymeric resultants. The products were characterized by means of 1H‐NMR, 13C‐NMR, IR spectroscopy, TLC, and Tg determinations. The conclusions drawn on the basis of the experimental work provided a satisfactory interpretation of the complex reactions which occur during the polyamidation of bischloride A2. They also point to interesting possibilities for the use of difunctional aroxyacetyl chlorides as modifying comonomers in minor amounts in the preparation of copolyaramides with reduced crystallinity. Such copolyaramides would be expected to have better solubility in common solvents and to be more easily processable than the rather specialized and extremely high‐melting polyaramides currently commercially available and could therefore extend the range of useful applications for this class of polymers.The experimental section is preceded by an introduction which briefly reviews the “state of the art,” especially as far as bischloride A2‐based polyamidation reactions are concerned. It is followed by a discussion of the results, by the conclusions, and a brief summary.
Photocrosslinking of poly(2,3‐epithiopropyl methacrylate) by the oxidation of pendant episulfide groups
Authors: Tsunooka Masahiro , Tanaka Shingo , Tanaka Makoto , Egawa Hiroaki , Nonaka Takamasa 
Published: April 2003

AbstractIn the photocrosslinking of poly(2,3‐epithiopropyl methacrylate) (PETMA) films the effect of the pendant episulfide group's oxidation on the crosslinking of PETMA was investigated. Thermal crosslinking of PETMA is promoted by peroxides such as benzoyl peroxide and hydrogen peroxide. IR spectrum of the crosslinked PETMA showed that the reaction proceeded through the oxidation of episulfide groups by the peroxides. The anthracene (An) sensitized photocrosslinking of PETMA films also proceeded via the oxidation of episulfide groups by singlet oxygen. It was found that residual tetrahydrofuran (THF) in the films remarkably increased the rate of the photocrosslinking and/or reduced the induction period. From the further investigation concerning casting solvents it was found that residual CS2, CCl4, and CHCl3 in films increased the rate of the photocrosslinking and/or reduced the induction period of the photocrosslinking. The disappearance rate of An in the films was also increased by the presence of residual CS2, CCl4, and CHCl3, differring from the result of THF. These results were explained by a difference in lifetime of singlet oxygen in the films. From the results were explained by a difference in lifetime of singlet oxygen in the films. From the results concerning the effects of hydroperoxides such as THF hydroperoxide and t‐butyl hydroperoxide on the photocrosslinking of PETMA films the acceleration effect of the residual THF was deduced to be due to the promotion of singlet oxygen‐oxidation of sulfide groups by protic compounds such as THF hydroperoxide and H2O in the THF.
The mechanisms of thermal degradation of polymethyl acrylate using pyrolysis gas chromatography mass spectrometry
Authors: Gunawan L. , Haken J. K. 
Published: April 2003

AbstractThe pyrolysis of polymethyl acrylate is reported with identification of the major pyrolysis products. The mechanism involving random homolytic scission of the chain followed by a series of intermolecular and intramolecular transfer reactions as proposed by Cameron and Kane and extended by Haken, Ho, and Houghton is further developed. Reaction mechanisms are postulated for all of the products produced and ion fragmentation mechanisms for the various spectra produced are shown. The paper also forms the basis for a study of the homologous alkyl polyacrylates, both straight and branched chain esters being considered these having not been previously extensively studied.
Introduction of hydrophilicity of polyacetylene film surfaces
Authors: Guiseppi‐Elie Anthony , Wnek Gary E. 
Published: April 2003

AbstractPolyacetylene films have been rendered hydrophilic by treatment with aqueous KMnO4. The treated films were characterized by contact angle measurement, infrared spectroscopy, and x‐ray photoelectron spectroscopy. We found that it is possible to lower the contact angle of H2O on polyacetylene from 72° to ca. 10° without significantly affecting the electrical conductivity afforded after I2 doping compared with similar doping of untreated films. The treated, hydrophilic films were found to be more permeable to aqueous ionic solutions than pristine polyacetylene.
Vinyl polymerization of acrylamide initiated by Thallium(III) ions in solution
Authors: Misra Sivananda , Sahu Gangadhar 
Published: April 2003

AbstractKinetics of polymerization of acrylamide initiated by Thallium(III) perchlorate was investigated in aqueous perchloric acid medium in the temperature range of 55–70°C. The rates of polymerization were measured varying the concentration of the monomer, initiator, and perchloric acid. The rate of polymerization was found to increase with increase of temperature, monomer concentration, initiator concentration, and perchloric acid concentration. The effect of additives like different solvents, surfactants, and retarders on the rate of polymerization was studied. Molecular weights of the polymer were determined by viscometry. The chain transfer constants for the monomer (CM) and that for the solvent dioxan (Cs) were calculated to be 7.33 × 10−3 and 6.66 × 10−3, respectively. From the Arrhenius plot, the overall activation energy (Ea) was calculated to be 10.68 kcal/mol. The energy of initiation was calculated to be 12.36 kcal/mol. Depending on the results obtained, a suitable reaction mechanism has been suggested and a rate equation has been derived.
Poly(bismethylene hydroquinone) (PBHQ). I. Synthesis and characterization
Authors: Dalal V. F. , Litt M. H. , Rickert S. E. 
Published: April 2003

AbstractPoly(bismethylene hydroquinone) (PBHQ) has been synthesized. Fourier transform infrared, 13C solid‐state CP/MAS NMR and elemental analysis provide strong evidence of two methylene bridges per hydroquinone molecule. The polymer was (1) air oxidized using ammonia and (2) chemically oxidized using bromine/KOH. The initial structure and oxidation process was studied by comparison of the unoxidized and oxidized polymers using Fourier transform infrared, elemental analysis, and 13C solid‐state CP/MAS NMR.
A kinetic model for predicting oxidative degradation rates in combined radiation‐thermal environments
Authors: Gillen Kenneth T. , Clough Roger L. 
Published: April 2003

AbstractThe complex degradation behavior of a poly(vinyl chloride) (PVC) cable jacketing material in combined radiation/temperature/air aging environments is experimentally separated into two dominant radiation dose‐rate effect mechanisms. The first, operative at high dose rates, involves diffusion‐limited oxidation, which leads to heterogeneously oxidized samples. The second, important at low dose rates, involves thermally‐induced breakdown of intermediate peroxides. In the homogeneous degradation regime, a theoretical kinetic model is derived which, based on experimental evidence, assumes unimolecular termination kinetics and rate‐determining, hydroperoxide‐mediated branching reactions. Dependent upon the ratio of particular rate constants, the model predicts that dose‐rate effects will either continue to increase or eventually disappear as the dose rate is lowered. Theoretical analysis of sequential (radiation followed by temperature exposures) aging experiments allows a time–temperature–dose rate shifting procedure to be developed. Using this procedure, higher temperature combined environment results can be shifted to a lower reference temperature, thereby extending the lower temperature results to lower (and experimentally inaccessible) dose rates. By applying this procedure to experimental PVC data, evidence in support of the theoretical model is obtained. In addition, model predictions are shown to agree with 12‐year real‐time aging results.
Synthesis, characterization, and complexing properties of a polymethacrylate bearing pendant macroheterocyclic structures
Authors: Herweh J. E. 
Published: April 2003

AbstractThe synthesis of a polymerizable methacrylate bearing the dibenzo‐18‐crown‐6 moiety (5) was effected in three steps by condensation of 3,4‐dihydroxybenzaldehyde with 1,2‐bis[2′‐(2″‐chloroethoxy)ethoxy]benzene (2), reduction of the resulting 4‐formyldibenzo‐18‐crown‐6 (3) to 4 and subsequent reaction of 4 with methacryloyl chloride. The methacrylate (5) was polymerized in solution using 2,2′‐azobis(isobutyronitrile) (AIBN) as the initiator and gave a solid polymer (6) having a midrange Tg of 67°C. The polymethacrylate bearing pendant crown‐ether structure (6) was found to effectively complex potassium ions and was clearly more effective in its complexing ability than dibenzo‐18‐crown‐6 (7) or a polyurethane bearing the dibenzo‐18‐crown‐6 moiety (8) in the polymer backbone. The subject polymer (6) was also found to complex and consequently solubilize several metal 7,7,8,8‐tetracyanoquinodimethane (TCNQ) salts to give semiconducting compositions. Evidence is given that in the presence of the neutral acceptor molecule, 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ), the polymethacrylate (6) acting as a donor, gives rise to a charge‐transfer (C/T) complex.
Polyamides from 2,6,(7)‐diamino‐9,10‐dihydro‐9,10‐ethanoanthracene and 2,6,(7)‐diaminoanthracene
Authors: Frazer A. H. , Anderson B. C. , Garver L. C. , Fukunaga T. 
Published: April 2003

AbstractHigh‐molecular‐weight, film‐forming, amorphous polyamides have been prepared from 2,6(7)‐diamino‐9,10‐dihydro‐9,10‐ethanoantracene with adipic, sebacic, dodecanoic, isophthalic, 4,4′‐oxybibenzoic, 2,6‐naphthoic, 4,4′‐bibenzoic, and terephthalic acid. Thermal elimination of ethylene from these polymers has yielded the corresponding polyamides from 2,6(7)‐diaminoanthracene which were of high molecular weight, film forming, and crystalline.
A contribution to the theory of accelerated sulphur vulcanization of natural rubber and polybutadiene BR with tetramethyl thiuram disulphide and bis(2‐benzothiazolyl) disulphide
Authors: Huson M. G. , McGill W. J. , Wiggett R. D. 
Published: April 2003

AbstractA number of simple natural rubber (NR) and polybutadiene (BR) formulations were vulcanized in a differential scanning calorimeter. From the shapes of the exothermal cure curves the interaction of curatives can be examined. It is suggested that polysulphidic‐accelerator‐terminated pendent groups could either crosslink, or be chelated with zinc ions. The latter reaction allows interaction with accelerator molecules to reform the unchelated pendent group, and a zinc accelerator complex, that, in turn, can react with sulphur and rubber molecules to give pendent groups. Differences in the behavior of NR and BR are attributed to the relative rates of these two reactions in the elastomers. Bis(2‐benzothiazolyl) disulphide does not react with zinc, and it is suggested that it coordinates with the zinc dithiolate accelerator complex, increasing its activity.
On the synthesis and polymerization of t‐butyl‐p‐vinylperbenzoate and the grafting of its homo‐ and copolymers
Authors: Schaefers Klaus , Schneider Christel 
Published: April 2003

AbstractThe monomer initiator t‐butyl‐p‐vinylperbenzoate (TBVP) was synthesized and its homo‐ and copolymerization with styrene, methacrylonitrile, isoprene and phenylmethacrylate was investigated. TBVP is preponderantly incorporated in all four systems; values of Q = 2.27 and e = −0.13 characterize TBVP as a weak donor with a high monomer reactivity. Kinetic considerations show that all propagation steps in which TBVP takes part are faster or at least as fast as the self‐propagation steps of the comonomers used. Rate constants and activation energies of the thermal decomposition of poly(t‐butyl‐p‐vinylperbenzoate) and poly(t‐butyl‐p‐vinylperbenzoate‐co‐styrene) were determined. The polymer initiators were used for grafting experiments with styrene, acrylonitrile, and methyl methacrylate. The data evaluated for the grafting efficiency, the success of grafting, and the degree of grafting show that these polymers of p‐vinylperbenzoate are efficient initiators.
Reduction in the moisture absorption of cured MY720/DDS epoxy resins
Authors: Fisher C. M. , Gilbert R. D. , Fornes R. E. , Memory J. D. 
Published: April 2003

AbstractThin films of cured MY720/DDS epoxy resins were treated with blocking reagents for hydroxyl, amine, and epoxide functional groups. Infrared spectroscopy (IR) and differential scanning calorimetry (DSC) were used to monitor the progress of the reaction. Treated films were soaked in distilled water at 30°C for 720 h, and the corresponding moisture absorption determined gravimetrically. Samples treated with N‐methyl‐N‐t‐butyldimethylsilyl trifluroacetamide (MTBSTFA) containing 1% t‐butyldimethylchlorosilane (TBDMCS) in dimethylsulfoxide (DMSO) at 30°C showed a maximum reduction in the IR peak at 3400 cm−1 (OH and NH) of 39% and a 100% reduction in the epoxide peak at 904 cm, −1. The moisture absorption was 1.9%, a reduction of 58% compared to the untreated films (ca. 4.5%). The reactions show dependencies on time and temperature and are diffusion controlled. Samples treated with trimethylsilyl isocyanate (TMSI) in DMSO a 70°C showed 72% reduction in the 3400 cm−1 IR peak; DSC thermograms do not show an exothermic energy, suggesting that all epoxide groups reacted. These reactions are primarily dependent on time and temperature. The moisture absorption of TMSI treated samples was 1.0% (75% reduction). Samples were also treated with m‐trifluoromethyl phenyliscyanate (MTFPI). The reduction in the IR peak at 3400 cm−1 was 9%, but the moisture absorption was 2.4%—a reduction of 47%.