bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of dyes and dyeing on the mechanical properties of polymeric materials
Authors: Ugbolue S. C. O. , Aula S. M. 
Published: April 2003

AbstractThe effect of reactive and disperse dyes and dyeing on the mechanical properties of cotton and polyester fibers, respectively, has been studied. It is observed that reactive dye (Procion Brilliant Red MX‐2B) and disperse dye (Dispersol Red B‐2B) caused a decrease in the tensile strength of the fiber which was often accompained by a decrease in the extensibility and general improvement in the tensile stiffness of the fibers. A linear relationship exists between percent disperse dye on the fiber and the square root of time of dyeing for poly(ethylene terephthalate) fibers in the initial region of dye uptake.
Surface characterization of plasma‐treated poly‐p‐xylylene films
Authors: Nowlin T. E. , Smith D. Foss 
Published: April 2003

AbstractPlasma‐treated poly‐p‐xylylene films have been characterized by neutron activation oxygen analysis, internal reflection (IRS) and transmission infrared spectroscopy, transmission electron microscopy (TEM), and surface contact angle measurements. The results indicate that an oxygen plasma roughens the surface and that oxygen is incorporated into the surface. Oxygen is not detected in the bulk of the sample. The infrared transmission spectra exhibited no carbonyl band, but the relative band intensities changed, indicating a change in ring substitution by a loss of chlorine in the chlorinated poly‐p‐xylylenes. The IRS spectra of the surface of films treated with oxygen plasma did contain carbonyl bands at 1730 and 1640 cm−1. Argon and helium plasmas generally decreased the water contact angle measured on plasma‐treated poly‐p‐xylylene surfaces more than oxygen or nitrogen plasma treatments. Regardless of the plasma utilized, the water contact angles increased with time after the treatment but did not recover to the original level. IRS spectra of the surface of films treated with argon plasma contained carbonyl bands at 1730 and 1695 cm−1. The adhesion of a polyurethane thermosetting material to a poly‐p‐xylylene surface is greatly improved if a plasma treatment is used prior to the application of the polyurethane. The degree of improvement in adhesion was dependent on the type of plasma and the treatment time.
Polyparaxylylene electrets usable at high temperatures
Authors: Raschke C. R. , Nowlin T. E. 
Published: April 2003

AbstractThin coatings of various polyparaxylylenes were transformed into electrets by corona charging them and then overcoating with more polyparaxylylene to protect the charge layer. For such electrets, the extrapolated ten‐year use temperature depended on the thermo‐oxidative stability of the polyparaxylylene layer and was greater than 100°C for the most stable electrets. The voltage levels and surface charge densities were always greater than or equal to those of charged Teflon electrets, similar to those used in commercial devices.
Comparison of laboratory techniques for evaluating the fracture toughness of glassy polymers
Authors: Ting R. Y. , Cottington R. L. 
Published: April 2003

AbstractSeveral test methods were employed to determine polymer fracture toughness (𝒢Ic, the opening‐mode strain energy release rate) at room temperature. The materials used included DGEBA epoxies and those modified by the addition of CTBN elastomers. Double‐cantilever beam specimens were used to determine the fracture toughness both of bulk resins and of an adhesive layer bonded between two aluminum half‐beams. The adhesive fracture toughness of a 0.025‐cm bond was slightly less than the bulk 𝒢Ic value, attributed to the bond thickness effect. Fracture toughness of bulk resins was also evaluated by using both rectangular and round compact tension specimens. The results, when compared with those obtained with the bulk double‐cantilever beams, are quite acceptable. The thickness of compact tension specimens, ranging from 0.64 to 1.0 cm, might not give pure plane‐strain conditions, and thus some plane‐stress contribution to 𝒢Ic should be expected for the tougher materials. Izod impact tests were also carried out to determine sample fracture toughness at high loading rate.
Catalytic effect of hydrogen chloride on the degradation of poly(vinyl chloride)
Authors: Owen Eryl D. , Pasha Ishrat , Moayyedi Faezeh 
Published: April 2003

AbstractThe distribution of polyenes which results from the chemical dehydrochlorination of poly(vinyl chloride) has been studied in dichloromethane (DCM) and tetrahydrofuran (THF) solvents. A higher percentage of longer polyenes is formed in DCM than in THF. On the addition of trifluoroacetic acid to DCM solutions of the polyenes, new species are formed with strong absorptions in the region 500–800 nm. The absorptions are probably due to polyenylic ions formed by protonation of the polyenes, and the interrelated changes in their intensities can be explained by the migration of short polyene sequences along the polymer chain with the formation of longer sequences. The species are extremely photosensitive and are bleached in a few seconds with light from a medium‐pressure mercury lamp. The relevance of these experiments to the effect of HCl on the polyene distribution and on the rate of photocrosslinking is discussed.
Preparation and surface modification of poly(vinylbenzyl chloride) latices
Authors: Chonde Y. , Liu L‐J. , Krieger I. M. 
Published: April 2003

AbstractMonodisperse stable latices with reactive methyl chloride surface functionalities were prepared in the presence of mixed surfactants using vinylbenzyl chloride in various ways: as a homopolymer, crosslinked with divinylbenzene, copolymerized with styrene, and overpolymerized onto uniform polystyrene latices. In homopolymerization of vinylbenzyl chloride, the effect of monomer content and concntration and type of surfactant are reported. Nucleophilic displacement of the surface chloride by sulfite ions was accomplished by reaction with aqueous sodium sulfite, without change in latex particle size. Also discussed are ways to control the amount of water‐soluble polyelectrolyte produced as a result of the sulfonation reaction.
Studies on the semirigid chain polyamide—poly(1,4‐phenyleneterephthalamide)
Authors: Jingsheng Bao , Anji You , Shengqing Zhang , Shufan Zhang , Chang Hu 
Published: April 2003

AbstractIn this article, the polycondensation of terephthaloyl chloride and p‐phenylenediamine was systematically studied, including the liquid–crystalline state of the solution and the spinning of poly(1,4‐phenyleneterephthalamide) (PPTA). High‐molecular‐weight PPTA with εinh = 5–7 was prepared and the main factors influencing the solution polycondensation of 1,4‐phenylenediamine with terephthaloyl chloride were studied in detail. Experimental results showed that the water content of the reaction system, reactant concentration, and volume ratio of mix solvents have a great influence on the inherent viscosity of the poly(1,4‐phenyleneterephthalamide) obtained. The highest εinh was obtained at 0.3M/liter reactant concentration in a mixed solvent ratio HMPA/DMAC of 4/1 (by volume), at 0.35M/liter reactant concentration in a mixed solvent of HMPA/NMP = 7/3, and at 0.5M/liter of reactant concentration in a mixed solvent of HMPA/THF = 9/1. The water content must be controlled to less than 100 ppm in the polymerization system. In the early stage of the polycondensation process, the εinh of the polymer obtained increased rapidly with time. The system gelled within 2 or 3 min, while the monomer conversion reached about 100%. However, the reaction of polycondensation continued after gelation and the εinh of the polymer increased appreciably. We have studied the viscosity behavior at 20–155°C for the anisotropic solution of PPTA in 100% sulfuric acid (εinh of PPTA 2.5–4.9). Experimental results showed that, at low concentrations the viscosity of isotropic solution increases with the increase of polymer concentration to reach a maxium near the critical polymer concentration, beyond which the solution changes to an anisotropic liquid–crystalline solution. The appropriate spinning region was obtained as shown in the phase diagram determined by viscosity, degree of depolarization anisotropy, and region of thermal depolymerization. Fibers of PPTA with high modulus and high tenacity were obtained by dry‐jet wet spinning. The fibers obtained have a tenacity of ∼22 g/denier, a modulus of ∼600 g/denier, and elongation at break ∼3.5%.
Polyester chain scission by selective chemical site attack
Authors: Hogsed M. J. , Carlson B. A. , Maerov S. B. 
Published: April 2003

AbstractTribenzylamine moieties copolymerized into poly(ethylene terephthalate) (PET) are selectively cleaved by mild hypochlorous acid oxidation to give dibenzylamines plus aldehyde and/or carboxyl groups. When either 3,3′‐dicarboxytribenzylamine (DCTBA) or 4,4′‐DCTBA were used, molecular weight was reduced, consistent with a mechanism where only two of the three carbon–nitrogen bonds which cleave can give polyester backbone scission. When copolymerized 3,5 DCTBA was cleaved, no chain scission resulted, but about one‐third of the nitrogen content was lost, again consistent with the random statistical oxidative attack at each of the three carbon–nitrogen bonds. Borane ester, B[(CH2)10CO2Me]3, copolymerized into PET, lost molecular weight progressively after melt spinning, drawing, and boil off of the resulting fibers. Chain scission resulted from rapid oxidation of borane bonds to borate esters followed by hydrolytic cleavage to boric acid and/or intermediate boronic acids.
Evaluation of number‐average molecular weight of poly(tetrafluoroethylene) irradiated with γ rays
Authors: Takenaga Mitsuru , Yamagata Kyozo 
Published: April 2003

AbstractThe number‐average molecular weight of poly(tetrafluoroethylene) (PTFE) irradiated from a 60Co source in air at room temperature has been estimated from the experimental results of tensile creep measurements and electron microscopy. The viscoelastic method which makes use of the maximum relaxation time was used for samples with low radiation doses. The mean chain length of highly irradiated samples, which can form fully extended chain crystals upon crystallization from the melt, was obtained from the bandwidth distribution on micrographs of the fracture surfaces. The dependence of the average molecular weight on the radiation dose is derived on the basis of a statistical treatment in which effects of cages in the process of chain scission and of molecules evolved out of the specimen, together with random decomposition of polymer backbone chains, are considered. Good agreement between the experimental and calculated results is attained over a wide range of radiation doses.
Mechanical behavior of gradient polymers
Authors: Martin G. C. , Enssani E. , Shen M. 
Published: April 2003

AbstractGradient polymers are multicomponent networks which contain a spatial gradient in the concentration of the components in the blend. In this study, the properties of a system of gradient polymers consisting of a rubbery addition to a glassy matrix [poly(methyl methacrylate)] and a glassy addition to a rubbery matrix [poly(2‐chloroethyl acrylate)] were investigated. Dynamic mechanical spectroscopy was used to characterize the compatibility of the polymers. The PMMA matrix gradients were found to be incompatible, while the PCIEA matrix gradients and the interpenetrating network exhibited compatibility. The tensile properties and the fracture strength of the polymers were measured and interpreted in terms of the composition and the deformation mechanism of the materials.
Cryogenic crushing of polystyrene
Authors: Vivatpanachart Somsak , Nomura Hiroyasu , Miyahara Yutaka 
Published: April 2003

AbstractAtactic and isotactic polystyrene powders were fractured with a ball mill at −196°C. The molecular weight distributions at various milling times measured by GPC show an initial asymmetric broadening and then a gradual returning to the original narrow bell‐shaped distribution. Analysis of molecular weight distributions suggests a preferential chain scission near the chain ends. X‐ray diffraction spectra of isotactic polystyrene samples show that after 24 hr of milling, the semicrystalline polystyrene was completely transformed into an amorphous polymer. DSC thermogram of the milled isotactic polystyrene reveals several crystallization peaks preceding melting when the samples were heated.
Polymer purification through solvent addition: Physical implications and modeling of separation units
Authors: Carrà S. , Morbidelli M. , Santacesaria E. , Niederjaufner G. 
Published: April 2003

AbstractAddition of solvents may ease removal of small amounts of volatile residues from polymeric materials. Enhanced separation thus obtained is due to the influence of the solvent on the vaporpolymer–liquid equilibria and to its influence on the increase of the diffusion rate of the impurities. The problem has been examined through a mathematical model describing the behavior of the units employed in the purification. Examples of applications are illustrated in which prediction of the behavior of purification units are performed from small‐scale apparatus experiments.
Storage hardening and “abnormal” groups in guayule rubber
Authors: Angulo–Sanchez J. L. , Jimenez–Valdez L. L. , Campos–Lopez E. 
Published: April 2003

AbstractThe hardening process of natural (Hevea brasiliensis) rubber, that takes place when this rubber is stored in dry conditions over long periods of time, has been correlated with the presence of reactive “abnormal” groups directly grafted on the polymeric chain and in the serum of the latex. In the present work, natural Hevea (HR) and Guayule (Parthenium argentatum) rubber (GR) were stored under accelerated conditions and the changes in Mooney viscosity and molecular weight measured. The results showed that while HR undergoes hardening, GR keeps its Mooney viscosity constant, as does a constant viscosity (CV) Hevea rubber. These results are explained by the absence of functional “abnormal” groups that sustain the hardening reactions.
Kinetics of dielectric‐loss microwave degradation of polymers: Lignin
Authors: Chan R. Wai‐Chun , Krieger Barbara B. 
Published: April 2003

AbstractThe rate of product formation as well as detailed product composition were measured in the rapid pyrolysis of a 1.3‐cm cylindrical pellet of lignin, a major component of biomass. Volume heating by dielectric‐loss microwave heating resulted in rapid weight loss with an apparent rate coefficient of 1–5 min−1. Char yield was surprisingly low (33%) owing to the rapid heating rate and high temperature of the pellet. Total gas yield was 38%, of which 12% were simple hydrocarbons and H2 (both weight percent, of original lignin). Product composition showed extensive secondary reaction at high temperatures evidenced by the significant yields of C2H2,H2, and condensed aromatics as well as the typical lignin cracking products such as phenols. Poor coupling of microwave energy to lignin required large power settings in order to initiate reaction. Once initiated, the reaction rate was difficult to control because of the exothermic nature of the reactions. Additives of a suitable composition to increase coupling may be a possible solution to this problem and may result in more favorable economics.
Copolymerization of styrene with acrylamide derivatives in an emulsifier‐free aqueous medium
Authors: Kawaguchi Haruma , Sugi Yoshishige , Ohtsuka Yasuji 
Published: April 2003

AbstractAcrylamide derivatives were copolymerized with styrene in an emulsifier‐free aqueous medium, and the copolymerization mode and the characteristics of the resulting latices were compared with those of a styrene–acrylamide copolymerization system. In their copolymerization mode, N‐(hydroxymethyl)acrylamide and N,N‐dimethylacrylamide resembled acrylamide, and their heterogeneous copolymerization course was divided into three stages on the basis of the main reaction locus. Copolymerization of styrene–methacrylamide did not resemble that of the others. The interfacial property and reactivity of acrylamides affected not only the polymerization mechanism but also the latex properties, e.g., particle size, distribution of acrylamides units in the latex, etc. The narrowest distribution of particle size was obtained in styrene–N‐(hydroxymethyl)acrylamide copolymerization at a monomer ratio of 10:1. Delayed addition of styrene into the aqueous solution of N‐(hydroxymethyl)acrylamide prepolymerized to some extent was found to be effective in preparing a latex with nearly monodisperse and large particles.
Photoconductivity of poly(vinyl alcohol) films with Fe3+ complexes and ESR study of their structures
Authors: Sumita Osao , Fukuda Atsuo , Kuze Eiichi 
Published: April 2003

AbstractWe have studied whether photoconductivity is observed in polymer films containing the first transition metal complexes. Polymers investigated were poly(vinyl alcohol) (PVA), polyacrylamide, poly(acrylic acid), poly(vinyl pyrrolidone), and polyethylene glycol. Transition metal salts used were CrCl3, MnCl2, FeCl3, CoCl2, NiCl2, FeBr3, Fe(NO3)3, Fe2(SO4)3, and Fe(ClO4)3. Only in the PVA–FeCl3 film was relatively large photoconductivity due to the photoreduction of Fe3+ observed. ESR spectra indicate that an Fe3+ ion is chelated with two in‐plane OH residues of PVA and coordinated with three Cl−ions on the meridian. UV irradiation causes an electron transfer from Cl− to Fe3+. The produced chlorine atom extracts an electron from the oxygen of a neighboring OH residue. The unpaired electron thus formed can move from one oxygen to another through hydrogen bonding. In other words, the photoconductivity is due to holes produced in the network of PVA hydrogen bonding by the reduction of Fe3+. Finally, we have tried to explain why the photoconductivity is observed only in the PVA–FeCl3 film.
Effects of structural features of cotton cellulose on enzymatic hydrolysis
Authors: Focher B. , Marzetti A. , Cattaneo M. , Beltrame P. L. , Carniti P. 
Published: April 2003

AbstractTextile cotton wastes were treated with γ rays and 18% NaOH and 70% ZnCl2 solutions and were subjected to enzymatic hydrolysis. The untreated and treated samples were characterized both before and after hydrolysis by means of parameters concerning molecular structure (degree of polymerization), supermolecular structure (x‐ray diffraction), accessibility, and reactivity (moisture regain, enzyme adsorption, and solubility in FeTNa). These parameters were correlated to kinetic parameters of the hydrolysis reaction. The Vmax and Km values were evaluated from Lineweaver–Burk plots at different temperatures. The Vmax/Km ratio, analogous to the specificity constant, proved to be less sensitive to experimental errors and more suitable for a comparison of the kinetic behavior of the samples. The modifications of both supermolecular structure and morphology of cellulose were of primary importance to attain high yields and rates of hydrolysis. Furthermore, the structural and morphologic parameters chosen to characterize the samples can be correlated to the kinetic parameters of enzymatic hydrolysis, in particular to Km values.
Thermomechanical analysis of Tg and T > Tg transitions in polystyrene
Authors: Keinath Steven E. , Boyer Raymond F. 
Published: April 2003

AbstractPhenomenological softening points were measured on a series of 13 anionic, nearly monodisperse, atactic polystyrenes using a DuPont 943 thermomechanical analyzer (TMA) in a penetration mode. Although TMA cannot identify the nature of the “transition” observed as such, the results obtained support the evidence for the Tg, Tll, and T′ll transition in polystyrene discussed in recent literature. Tg and Tll were found to vary with molecular weight in a systematic manner, while T′ll could only be observed at very high molecular weight. The technique appears to be quite useful in offering rapid and reproducible information on the various transitions in the liquid state of polystyrene.
Simulation of molecular weight distribution and cyclic oligomer formation in the polymerization of nylon 6
Authors: Gupta Santosh K. , Naik C. D. , Tandon Pravin , Kumar Anil 
Published: April 2003

AbstractThe reversible polymerization of nylon 6 including ring opening, polycondensation, polyaddition, and cyclization reactions as well as the reaction with monofunctional acids was simulated for an isothermal batch reactor at 235°C. The cyclic oligomer concentrations, the molecular weight distributions, and its moments have been computed using a chain length‐dependent equilibrium constant for the cyclization reaction. Even though the cyclization step does not influence the monomer conversion considerably, it does effect the molecular weight distribution and its moments.
Manufacture of ultrahigh‐modulus poly(oxymethylenes) by die drawing
Authors: Hope P. S. , Richardson A. , Ward I. M. 
Published: April 2003

AbstractA stable experimental die drawing process has been operated for poly(oxymethylene) over a range of temperature. Rods possessing room‐temperature Young's moduli up to 23 GPa were produced using a homopolymer grade, the values obtained from a copolymer being somewhat lower. This compares favorably with the best modulus achieved by hydrostatic extrusion but is rather lower than that produced by conventional drawing; reasons for this are discussed. A stable die drawing process has also been operated for glass fiber‐reinforced poly(oxymethylene), but extensive macroscopic void formation occurred in the products under all conditions, reducing their potential for practical application.
Morphology and properties of poly(vinyl chloride)–polyurethane blends
Authors: Wang Carl B. , Cooper Stuart L. 
Published: April 2003

AbstractThe objective of this research was to study the morphology and properties of PVC–polyurethane blends. Studies on blends of a segmented polyether polyurethane with PVC were carried out utilizing differential scanning calorimetry, Rheovibron, stress–strain, infrared peak position studies, and infrared dichroism experiments. This thermodynamically incompatible system was made kinetically compatible by precipitation from tetrahydrofuran (THF) solutions. THF–dioxane solution casting and melt processing produced an incompatible system. The compatible polyurethane–PVC system contains a well‐mixed PVC–polyether matrix phase as evidenced by Tg shifts, orientation characteristics, and infrared peak position changes. The aromatic urethane segments which exhibit microphase separation in the pure polyurethane are not solubilized by blending with PVC by any of sample preparation methods used in this study.
The effect of network structure on moisture absorption of epoxy resins
Authors: Diamant Y. , Marom G. , Broutman L. J. 
Published: April 2003

AbstractAn investigation of the effect of modifying the network structure on moisture absorption of epoxies was performed. The network was modified by crosslinking the epoxides with various mono/diamine proportions, resulting in decreasing density and increasing free volume. It was discovered, however, that concomitant effects, i.e., the formation of a two‐phase structure, and changes in resin polarity and in resin–water affinity predominated. Thus, compositions with higher chain molecular weights between crosslink points yet exhibited lower diffusion coefficients. Also, when drastic swelling conditions (such as a water‐boil treatment) were employed, moisture absorption was facilitated by penetration via newly formed microcracks.
Combustion and pyrolysis of poly(ethylene terephthalate). II. A study of the gas‐phase inhibition reactions of flame retardant systems
Authors: Day M. , Suprunchuk T. , Wiles D. M. 
Published: April 2003

AbstractA device to measure the flammability limits of the gaseous pyrolysis products of polymeric materials has been developed and applied to a study of untreated and flame‐retarded poly(ethylene terephthalate). The results indicate that phosphorus‐containing compounds, like bromine‐containing compounds, are capable of inhibiting the gas‐phase free radical combustion reactions of the pyrolysis products obtained from poly(ethylene terephthalate).