bluuebunny/crossref_metadata_2025_split huggingface dataset:
ESCA study of oxidized wood surfaces
Authors: Hon David N.‐S. 
Published: April 2003

AbstractResults of a preliminary study of the surface of wood exposed to outdoor weathering as well as to UV irradiation showed that ESCA provides valuable information and insight into the manifestation of weathering and photooxidation. From the ESCA spectra, the increase in signal intensities of carbon–oxygen bonds and oxygen–carbon–oxygen bonds (or unsaturated carbon oxygen bond) and oxygen‐to‐carbon ratio, and the decrease in carbon–carbon and carbon–hydrogen bonds of weathered and UV‐irradiated wood surfaces suggested that wood surface was oxidized. Nevertheless, it was a superficial effect. Only a slow oxidation was observed at 100 μm under the exposed wood surfaces. From the oxygen‐to‐carbon ratio data, it revealed that weathered wood surface was rich in cellulose, poor in lignin. The leached‐away degradation products from weathered wood surface accounted for the discrepancy between the ESCA line shapes of UV‐irradiated and weathered wood surfaces.
Molecular characterization of hydroxyl‐terminated polybutadienes
Authors: Inagaki Hiroshi , Donkai Nobuo , Saitoh Akihisa , Zenitani Yukio 
Published: April 2003

AbstractA comparative study has been made on the functionality distribution of two hydroxyl terminated polybutadiene products which are used largely as prepolymers for sealants, adhesives, and solid propellants. They are known to possess nearly the same molecular characteristics. To this end, each product was fractionated into 17 fractions with different molecular weights by the preparative GPC technique. Sample fractions thus obtained were subjected to “polarity‐controlled adsorption” thin‐layer chromatography (TLC) to determine the functionality distribution. From these experimental results it was concluded that a decisive difference between these products consists in the functionality distribution, within a molecular weight range higher than 7000.
Effects of copper and molybdenum oxides on the pyrolysis of model compounds of poly(vinyl chloride)
Authors: Lattimer Robert P. , Kroenke William J. , Getts Ronald G. 
Published: April 2003

AbstractNumerous transition metal compounds can be added to poly(vinyl chloride) to decrease the smoke evolved during burning or smoldering conditions. Model compound pyrolysis experiments have been carried out to investigated the mechanisms by which smoke retarder additives function in PVC. Three models were used: 3‐chloropentane, 2,4‐dichloropentane, and 2,4,6‐trichlorohenptane. The additives MoMO3 and Cu2O both enhanced the rate of dehydrochlorination and promoted the formation of crosslinked products (oligomers) during model compound pyrolysis, but their mechanistic pathways were found to be different. The choice of model compounds also was an important influence in determining the observed decomposition pathways. While much of the pyrolysis chemistry can be explained by Lewis acid catalysis, other effects also appear to be important. The pyrolysis results are interpreted in terms of an “early crosslinking” mechanism of smoke retardation in PVC. In this mechanism the metal smoke retarder works primarily by catalytically promoting early crosslinking of decomposing PVC chains to yield char as a residue.
X‐ray analysis of α‐, β‐, and γ‐phase Ag–Hg alloy films produced on polymer substrates by casting polyacrylamide–AgNO3 aqueous solution in Hg atmosphere
Authors: Lee Jiunn Yih , Ohtsuka Kiyoto , Takezoe Hideo , Fukuda Atsuo , Kuze Eiichi , Iwanaga Hiroshi 
Published: April 2003

AbstractIt is reported that, by dropping Hg metal on the wet α‐phase Ag–Hg alloy film formed on the cast polyacrylamide–AgNO3 aqueous solution, the α phase of fcc structure can be converted into other phases that contain more Hg. The X‐ray analysis of these phases reveals that they are the β phase of hexagonal structure and the γ phase of bcc structure. It is also shown that the lattice constant of the α phase can be controlled to some extent by pH of the aqueous solution of PAAm from which the alloy film is formed.
Phase behavior of binary mixtures of oligomeric styrene/allyl alcohol copolymers and aliphatic polyesters
Authors: Woo E. M. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractThe phase behavior of binary mixtures of copolymers containing varying amounts of styrene and allyl alcohol (SAA) with a wide range of aliphatic polyesters has been examined. All of the copolymers and most of the polyesters had low molecular weights in the oligomeric range; hence, entropy effects were a significant factor in the observed phase behavior. The polyesters employed had CH2/COO ratios over the entire range from 2 to 12. The SAA copolymers were completely miscible with polyesters in the middle of this range based on the observation of a single composition‐dependent glass transition for these mixtures. Upper critical solution temperature behavior was observed for blends of SAA copolymers with polyesters having ratios of CH2/COO immediately on either side of this optimum region of Polyester structure. Complete immiscibility was noted for blends with polyesters having CH2/COO ratios at either extremity of the range examined. Interaction parameters were deduced from either melting point depression data or the cloud point observations and correlated with the structure of the components.
Effect of stirring on cellulose graft copolymerization. III. Acrylic and methacrylic monomers
Authors: Graczyk Tomasz , Hornof Vladimir 
Published: April 2003

AbstractAcrylate and methacrylate monomers were grafted onto dissolving pulp by the xanthate process. All the nine monomers tested showed a well‐defined dependence of conversion on stirring speed. Total conversion and conversion to copolymer vs. agitator speed curves for each monomer were very similar in shape, but they varied widely from monomer to monomer. For the homologous series acrylate and methacrylate esters, optimum stirring speed was found to increase with increasing the size of the alkyl group. The breadth of the maximum also depended on the type of monomer. Monomers partially soluble in water forming water‐insoluble polymers were found to be the most reactive.
Viscosity–molecular weight relationships for poly(ethylene terephthalate) in hexafluoroisopropanol–pentafluorophenol using SEC–LALLS
Authors: Berkowitz Steven 
Published: April 2003

AbstractViscosity–molecular weight characterization of poly(ethylene terephthalate) (PET) in hexafluoroisopropanol (HFIP), pentafluorophenol (PFP), and HFIP/PFP is reported for the first time using size exclusion chromatography‐low angle laser light scattering (SEC–LALLS) measurements. These strong solvents are capable of dissolving PET under very mild conditions and therefore minimize polymer degradation. In addition these solvents are capable of dissolving PET samples which have poor solubility in more traditional PET solvents such as orthochlorophenol (OCP) and phenol/tetrachloroethane (PTCE). By combining molecular weight information, obtained without the need of any SEC calibration curves, with intrinsic viscosity measurements, on several broad molecular weight PET samples, the Mark–Houwink coefficients for the five PET–solvent systems mentioned above have been determined. The coefficients correspond to those which would be obtained by using a large number of relatively monodisperse samples of PET covering a molecular weight range of about 2 × 103 to 2 × 105. Data is also provided which shows that intrinsic viscosities for PET in HFIP, PFP, HFIP/PFP, OCP, and PTCE can be determined from a single viscosity measurement at a finite concentration. Data for interconverting intrinsic viscosities determined in any of these five solvents is also given.
Structural changes in polyester fibers during fatigue
Authors: Oudet Ch. , Bunsell A. R. , Hagege R. , Sotton M. 
Published: April 2003

AbstractStructural changes occurring during the fatigue failure of polyester fibers have been identified, and a comparison has been made with untested fibers and fibers which were subjected to cyclic loading conditions which did not produce fatigue. Fatigue failure was seen to result in a distinctive fracture morphology. Infrared spectrometry and X‐ray diffraction revealed a lowering of crystallinity under fatigue conditions but not under other loading conditions. Transmission electron microscopy and electron diffraction revealed the creation of amorphous zones which are supposed as coalescing to form an amorphous band seen along and ahead of the fatigue crack. The zone just ahead of the fatigue crack tip is shown to contain voids. Crack propagation involves, therefore, the joining up of these voids and development along the amorphous band.
Temperature dependence of mooney scorch time of rubber compounds
Authors: Lee C. H. , Poh B. T. 
Published: April 2003

AbstractA study of the temperature dependence of Mooney scorch time was carried out by using two grades of natural rubber, Hevea Brasiliensis(SMR L and SMR 10), and on synthetic rubber, styrene—butadiene rubber (SBR), in the temperature range of 100–180°C. Results show that the scorch time for SBR system is greater than that of the other grades of natural rubber. This is attributed to the lower degree of unsaturation in SBR. Effects of 2‐mercaptobenzothiazole (MBT) and other types of accelerators on the scorch properties were also investigated and discussed. One black‐filled compound was used to study the dependence of carbon black on the scorch property, and data indicate that the effect is more evident for temperature lower than 100°C.
Structural modification of brominated epoxy resins by reaction with phosphoric or poly(phosphoric acid)
Authors: Mikroyannidis John A. , Nir Zohar 
Published: April 2003

AbstractA modification process of some commercial brominated epoxy resins by reacting them with phosphoric or poly(phosphoric acid) is described. The influence of the reactants ratio on the thermal stability of the modified resins was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The resin obtained from complete esterification of phosphoric acid showed the highest thermal stability. In addition, the resins prepared by reacting phosphoric acid with brominated epoxy resins of different molecular weight were thermally characterized by DSC and TGA. Most of the modified resins were thermally more stable than the corresponding unmodified resins. The chemical reactions that possibly take place during the process are discussed. Furthermore, the structure of the modified resins was investigated by Fourier‐transform‐infrared (FT–IR) spectroscopy.
Grafting onto wool. XXIII. Graft copolymerization of methyl methacrylate by use of chromium acetyl acetonate–perchloric acid system: Effect of tertiary butyl hydroperoxide
Authors: Sood D. S. , Rawat B. R. , Misra B. N. 
Published: April 2003

AbstractMethyl methacrylate (MMA) has been graft copolymerized onto Himachali wool in an aqueous medium by using chromium acetyl acetonate in the presence of perchloric acid at 45, 55, 65, and 75°C for various reaction periods. Percentage of grafting has been determined as functions of various reaction variables. Tertiary butyl hydroperoxide (TBHP) was found to influence grafting of MMA. Rate of grafting (Rp) and induction period (Ip) of MMA towards graft copolymerization were determined as function of total initial monomer concentrations. In the absence of TBHP, Rp does not change markedly with the increase in monomer concentration. When the graft copolymerization was carried out in the presence of TBHP, an increase in Rp and a decrease in Ip were observed.
The mechanism of cellulose alkalization in the isopropyl alcohol–water–sodium hydroxide–cellulose system
Authors: Yokota H. 
Published: April 2003

AbstractThe mechanism of cellulose alkalization in isopropyl alcohol (IPA)–water–sodium hydroxide system was studied from the viewpoint of the selective distribution of sodium hydroxide between cellulose and the medium, and of the lattice transition of cellulose. A mixture of IPA, water, and sodium hydroxide spontaneously separates into two layers, i.e., the upper layer solution (ULS) consists of IPA, water, and a small amount of sodium hydroxide and the lower one (LLS) consists of sodium hydroxide, water, and a very small quantity of IPA. The role of the ULS and the LLS was distinctive. The ULS has a function to distribute sodium hydroxide with water in cellulose uniformly according to the distribution equilibrium between ULS and cellulose, and the ULS recovers sodium hydroxide with water from the LLS as the distribution equilibrium shifts in the alkalization of cellulose. The concentration of sodium hydroxide in the LLS and that of IPA in the ULS exerts an influence on the lattice structure of alkali cellulose. During the transformation from cellulose I to alkali cellulose, decrystallization does not occur. Some portion of alkali cellulose reverted to cellulose I by regeneration.
Development of poly(meta‐phenylene terephthalamide) as a membrane material for the reverse osmosis process
Authors: Chandorikar M. V. , Korat D. R. , Devmurari C. V. 
Published: April 2003

AbstractThe low temperature, homogeneous, solution polycondensation method is optimized to synthesize poly(meta‐phenylene terephthalamide). The product is characterized and is also evaluated as a membrane material by studying its dense membrane. The fabrication technique of the osmotic flat membrane of poly(meta‐phenylene terephthalamide) is studied and its high‐pressure performance is tested. The optimized flat membrane is characterized.
Characterization of branched polydisperse polymers. Influence of solvents on the branching parameters
Authors: Dobkowski Zbigniew 
Published: April 2003

AbstractThe influence of solvents on the branching degrees G (the ratio of intrinsic viscosities) and g (the ratio of radii of gyration), and on the branching exponent b in equation G = gb has been estimated using the recently reported equations for branched polymers. The following relations have been found: G < ḡ0, ḡx, = ḡx0, and b > b0, where subscripts 0 and x denote the unperturbed (or theta) conditions and the type of average value for polydisperse polymers, respectively. Hence the expansion coefficients of branched and linear macromolecules are related by αη,br < αη,lin and αsbr = αs,lin.
Structural heterogeneities of suspension poly(vinyl chloride). II. Formation of compact glassy particles and the cause of their difficult processing
Authors: Lukáš Rudolf , Michalcová Jaroslava , Ková Věra Tyráč 
Published: April 2003

AbstractBy modifying the polymerization process of suspension polymerization of vinyl chloride, poly(vinyl chloride) (PVC) samples were prepared containing various amounts of compact glassy particles. It was found that these particles probably arise by a different polymerization mechanism than usual suspension particles, namely, as a result of the nonhomogeneous distribution of initiator in vinyl chloride drops of the polymerization system. It was proved experimentally that the lower heat stability of difficultly processible particles is due to a side reaction between the initiator radical and the PVC polymer chain which causes dehydrochlorination of PVC already under polymerization conditions. This reaction may also explain the yet unknown mechanism of formation of internal double bonds in PVC produced by the radical polymerization of vinyl chloride. In conclusion, the difficult processibility of compact glassy particles is discussed as a consequence of the insufficient drying of these particles in the usual drying process.
Intumescent flame retardant for polymers. III. The polypropylene–ammonium polyphosphate–polyurethane system
Authors: Montaudo G. , Scamporrino E. , Puglisi C. , Vitalini D. 
Published: April 2003

AbstractThe action of some mixtures of ammonium polyphosphate (APP) and polyurethanes (PUr) as flame retardant (FR) agents for polypropylene (PP) was examined. The APP–PUr systems behave as intumescent flame retardant (IFR) formulations. The IFR action of these systems is described by the comparison of the oxygen index (OI) values measured on molded pellets and on molded rods, by measurements of the polymer temperature just below the burning surface and by visual observations. A strong synergism between APP and some polyurethanes, having piperazine units in the polymer chain, was ascertained with a maximum 3:1 ratio. Our results also indicate that only polyurethanes with specific structure, in combination with APP, are active as IFR agents on PP combustion.
Mechanical properties and morphology of crosslinked PP/PE blends and PP/PE/propylene–ethylene copolymer blends
Authors: Chiu Wen‐Yen , Fang Shwu‐Jen 
Published: April 2003

AbstractBlending is an effective method for improving polymer properties. However, the problem of phase separation often occurs due to incompatibility of homopolymers, which deteriorates the physical properties of polyblends. In this study, isotactic polypropylene was blended with low‐density polyethylene. Crosslinking agent and copolymers of propylene and ethylene (either random copolymer or block copolymer) were added to improve the interfacial adhesion of PP/LDPE blends. The tensile strength, heat deflection temperature, and impact strength of these modified PP/PE blends were investigated. The microstructures of polyblends have been studied to interpret the mechanical behavior through dynamic viscoelasticity, wide‐angle X‐ray diffraction, differential scanning calorimetry, picnometry, and scanning electron microscopy. The properties of crosslinked PP/PE blends were determined by the content of crosslinking agent and processing method. For the material blended by roll, a 2% concentration of peroxide corresponded to a maximum tensile strength and minimum impact strength. However, the mechanical strength of those products blended by extrusion monotonously decreased with increasing peroxide content because of serious degradation. The interfacial adhesion of PP/PE blends could be enhanced by adding random or block copolymer of propylene and ethylene, and the impact strength as well as ductility were greatly improved. Experimental data showed that the impact strength of PP/LDPE/random copolymer ternary blend could reach as high as 33.3 kg · cm/cm; however, its rigidity and tensile strength were inferior to those of PP/LDPE/block copolymer blend.
Vinyl ester resins. II. Effect of styrene on electrical properties
Authors: Goel T. C. , Tripathi A. , Rao B. S. , Choudhary M. S. , Choudhary V. , Varma I. K. 
Published: April 2003

AbstractBisglycidyl methacrylate of bisphenol A (vinyl ester resin) having systematically varying styrene content was cured by using benzoyl peroxide as a initiator. Thermally stimulated discharge current (TSDC) and ac dielectric measurements of the cured resins were carried out. The polarization of these resins depended on the presence of polar groups and space charge. The lowest dielectric constant was observed with the resin having 30% styrene.
Method for gel permeation chromatography calibration and the evaluation of Mark–Houwink constants
Authors: Mahabadi H. Kh. 
Published: April 2003

AbstractA novel and simple method is described for evaluation of the Mark–Houwink constants and developing of GPC calibration curve for a polymer where only broad molecular weight distribution samples are available. The method demands the GPC calibration curve for polystyrene and measurement of the intrinsic viscosity and GPC chromatogram of several samples. Results of applying the procedure to polystyrene and poly(methyl methacrylate) are presented.
Gas permeability of polyacetylenes carrying substituents
Authors: Takada Koichi , Matsuya Hidehiko , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractThe gas permeabilities of three polyacetylene films, prepared from poly[1‐(trimethylsilyl)‐1‐propyne], poly(tert‐butylacetylene), and poly(1‐chloro‐2‐phenylacetylene), were studied. Although depending on conditions of polymerization and membrane preparation, typical permeability coefficients P of the polymers to oxygen and nitrogen at 25°C were as follows: poly[1‐(trimethylsilyl)‐1‐propyne], PO2 = 40 × 10−8, PNr2 = 20 × 10−8; poly(tert‐butylacetylene), PO2 = 3.0 × 10−8, PN2 = 1.0 × 10−8; poly(1‐chloro‐2‐phenylacetylene), PO2 = 9.4 × 10−10, PN2 = 2.0 × 10−10 cm3(STP) · cm/(cm2 · s · cm Hg). Thus PO2 of a poly[1‐(trimethylsilyl)‐1‐propyne] film is the largest among those ever known, and the values of poly(tert‐butylacetylene) and poly(1‐chloro‐2‐phenylacetylene) films are also fairly large. Influences of polymer structure, measuring temperature, and so forth on the PO2 and PN2 of these polyacetylene films were studied. The possibility of applying these films to oxygen enrichment of air are being discussed.
Alkaline hydrolysis of ethyl acrylate–acrylonitrile–divinylbenzene copolymer beads
Authors: Seidl Josef , Matějíček Alois , Krejcar Emil , Horký Jaroslav 
Published: April 2003

AbstractThis article deals with the alkaline hydrolysis of ethyl acrylate–acrylonitrile–divinylbenzene copolymer beads. Chemical changes during hydrolysis were evaluated by means of determination of total weight exchange capacity and of infrared spectroscopy. The influence of reaction temperature, concentration of the hydrolytic agent, degree of copolymers crosslinking as well as the influence of particle size upon the rate of hydrolysis were studied as a function of time. The mathematical and statistical calculations of experimental data were carried out. With respect to time dependence of hydrolysis of the copolymer functional groups, the average values of reaction rate constants as well as the values of assumed diffusion coefficients were calculated. The analysis is based on partial linearization of experimental results by means of semilogarithmic transformation. The empirical relations expressing dependences of reaction rate constants and of diffusion coefficients on conditions of hydrolysis were determined.
Differential scanning calorimetry of phenol–formaldehyde resols
Authors: Christiansen A. W. , Gollob L. 
Published: April 2003

AbstractDifferential scanning calorimetry was used on a range of synthesized phenol–formaldehyde (PF) resols to discover relationships between formulation parameters or physical properties of resols, and their thermal behavior during cure. The thermograms showed either one or two exothermic reactions. The lower exothermic peak temperature varied between 98 and 129°C with changes in the free formaldehyde content. This exotherm is caused by the addition of free formaldehyde to phenolic rings. The upper exothermic peak temperature varied from 139 to 151°C, with the higher temperatures occurring when the formaldehyde‐to‐phenol molar ratio was low or the total amount of sodium hydroxide relative to phenol was high. These two factors led to resins which contain a somewhat higher level of unreacted ortho or para aromatic ring positions and no free formaldehyde. Consequently, condensation is probably not solely by the faster self‐condensation through hydroxymethyl groups, but also includes the slower condensation of hydroxymethyl groups with unreacted ring positions. Gel times show trends with changes of formulation parameters somewhat similar to trends of the upper exothermic peak temperatures.
On thermal conductivity of some fabrics
Authors: Ismail M. I. , Ammar A. S. A. , El‐Okeily M. 
Published: April 2003

AbstractThe apparent density and the thermal conductivity of some samples of different wool/terylene blends were measured. It was shown that by increasing the terylene percentage, both the apparent density and the overall thermal conductivity increase to a maximum, and then decrease again. The blend consisting of 50% wool and 50% terylene has the maximum values of both thermal conductivity and apparent density.