bluuebunny/crossref_metadata_2025 huggingface dataset:
Retardation spectra for the existence of interphase in fiber composites
Authors: Theocaris P. S. , Kefalas V. , Spathis G.
Published: April 2003

Retardation spectra, derived from dynamic measurements of extension compliances along three decades on the logarithmic scale of frequencies in standard specimens prepared from a fiber‐reinforced composite with their fibers parallel to the longitudinal axis of the specimens, have revealed the structure of the matrix material of the composite. The experimental results were used to prove that the physicochemical rearrangements in the vicinity of the inclusions, consisting of restrained development of the macromolecules and especially their side chains due to the presence of the other phase, concentration of voids and dirt, shrinkage stresses developed during curing and creating microcracks (radial as well as along the interface), are activated by the existence of high stress gradients and eventually stress singularities due to the strong adhesion developed between phases.
Thermal oxidation of polypropylene in the temperature range of 120–280°c
Authors: Hoff Ariel , Jacobsson Sven
Published: April 2003

Thermal oxidation of isotactic polypropylene films at 120–280°C in air was studied. Separation and identification of the volatiles formed was carried out by gas chromatography–mass spectrometry. Sixteen products were tentatively identified for the first time. Altogether, 50 compounds representing hydrocarbons, ethers, alcohols, aldehydes, ketones, and acids are reported. Oxygen deficiency is manifested in diffusion‐limited products of olefines, dienes, and aromatic compounds. The relative amounts of acetaldehyde and acetone are almost temperature independent in the range of 120–280°C. This indicates a similarity of oxidative degradation of the polymer in a broad temperature range. Addition of an antioxidant to the polymer depresses the evolution of the main volatiles by 9–10 times at 280°C. The relative amounts of the volatiles formed are, nevertheless, the same as for the polymer without an antioxidant. The mechanism of formation of the degradation products is discussed.
Diffusive permeability of solutes in poly(vinyl alcohol) membranes as a function of the degree of hydration
Authors: Kojima Y. , Furuhata K. , Miyasaka K.
Published: April 2003

Sorption and permeation of sodium chloride, Congo Red (a direct dye), and Sunset Yellow (an acid dye) in PVA membranes were measured to discuss the relation among the degree of hydration H, permeability P, and diffusion coefficient D. Above H of 0.9, the permeability and diffusion coefficient of various solutes could be described by free volume theory provided that the value of V*s/Vfw is estimated properly, where V*s is the ratio of critical volume of permeating molecule to vander Waals volume of water and Vfw is the free volume fraction of water. Below H of 0.9, however, Ogston's relation which predicts a linear relation between (1‐H) and the logarithm of P or D fits better than the free volume relation. It seemed to indicate that the polymer networks simply had a geometrical obstruction effect in the diffusion of solutes. The diffusion coefficient extrapolated at H = 1 in Ogston's plot decreased with the increase in the interaction between solute and polymer as suggested by the partition coefficient. The hydration dependence of the partition coefficient K changed at H = 0.8 corresponding to the maximum amount of the bound water.
Liquid crystalline behavior of polymeric glycols terminated with aromatic diester and diacid mesogenic groups
Authors: Hoshino H. , Jin J.‐I. , Lenz R. W.
Published: April 2003

A series of bis(benzylterephthaloyl‐p‐oxybenzoyl)esters (mesogen I) and bis(p‐carboxybenzoyl‐p‐oxybenzoyl)esters (mesogen II) of several different polymeric glycols was prepared, and their thermotropic liquid crystalline behavior was studied by differential scanning calorimetry and by visual observation on the hot stage of a polarizing microscope. The polymeric glycols used were poly(ethylene oxide) (A), poly(tetramethylene oxide) (B), polybutadiene (C), and the hydrogenated polybutadiene (D) glycols, with molecular weights between 650 and 6000. With one exception, the benzyl ester derivations were not thermotropic, but the corresponding carboxylic acid derivatives were, and the related model compound, the bis(p‐carboxybenzoyl‐p‐oxybenzoyl)ester of 1,12‐dodecanediol, was also found to be liquid crystalline. The nature of the mesophases formed by the diacids derived from the macroglycol derivatives could not be clearly identified by their optical textures. Several of the diacid derivatives formed elastomeric films, even though they were still of low molecular weight, presumably because of chain extension by dimerization and association of the terminal mesogenic groups.
Thermal degradation of polyester thermosets prepared using dibromoneopentyl glycol
Authors: Skinner G. A. , Haines P. J. , Lever T. J.
Published: April 2003

Polyester thermosets have been prepared from maleic anhydride, phthalic anhydride, dibromoneopentyl glycol, and styrene, and their thermal degradation has been studied. Thermogravimetry has shown that degradation in air occurs in three main stages. For the 10% bromine polyester, the weight losses corresponded to 16.3%, 69.7%, and 13.9% of the original polymer weight—the temperatures of the DTG peak maxima being 217°C, 345°C, and 530°C, respectively. Infrared analysis of the residues showed that above 250°C there was a gradual reduction in the absorbance of all peaks with increasing temperature, indicating the degradation of all parts of the 3‐dimensional polymer structure was occurring in a simultaneous manner. Degradation of the dibromoneopentyl glycol polyesters at 530°C in air proved to be a very complex process since a mixture of organic products was produced which gave rise to well over 100 peaks in the capillary column chromatograms. Under the conditions used, the low temperature degradation products proved to be rich in phthalic anhydride with no benzaldehyde being detected. The yields of benzene, toluene, styrene, and naphthalene increased with increase in temperature.
Characterization of commercial polyvinylbutyral by gel permeation chromatography
Authors: Mrkvičková L. , Daňhelka J. , Pokorný S.
Published: April 2003

Fractions of commercial polyvinylbutyral “Movital” were investigated by the “off‐line” combination of gel permeation chromatography and viscometry. Parameters of the Mark–Houwink equation were determined for polyvinylbutyral in tetrahydrofuran at 25°C. Real values of the molecular parameters were obtained by the evaluation of chromatographic data using the principle of universal calibration.
Structural heterogeneities of suspension poly(vinyl chloride). I. Compact glassy particles
Authors: Lukáš R. , Tyráčková V. , Kolínský M.
Published: April 2003

By using the modified suspension polymerization of vinyl chloride, samples of poly(vinyl chloride) (PVC) were prepared with a high content of unprocessible particles which were isolated and subjected to a morphological investigation. Their structure was examined viscometrically, by the light‐scattering method, GPC, IR spectroscopy, and X‐ray analysis; the specific surface area of the particles was measured, and their heat stability was determined. The results lead to a conclusion that the unprocessibility of the particles compared with the usual particles of suspension PVC is not caused by differences on the level of molecular structure, but ensues from the difference in their morphology.
High‐temperature coupling of high‐speed GPC with continuous viscometry. II. Ethylene–vinyl acetate copolymers
Authors: Lecacheux D. , Lesec J. , Quivoron C. , Prechner R. , Panaras R. , Benoit H.
Published: April 2003

An application of the high temperature coupling of a gel permeation chromatograph with a home‐made continuous viscometric detector is described. It concerns the comprehensive characterization of ethylene–vinyl acetate copolymers. Suitable chromatographic conditions are chosen to enable a correct use of the universal calibration concept. Through analysis of poly(vinyl acetate) fractions and commercial polyethylene samples, a comparison is made with the results of classical measurements. Average molecular weights as well as intrinsic viscosity appear to be in good agreement within experimental error, which proves the system for the characterization of random ethylene–vinyl acetate copolymers. In attempting to obtain a reliable estimate of long chain branching frequency λ, a series of commercial samples has been selected, with the vinyl acetate weight fraction within the range 0–45%. As a rule, experimental viscosity law exhibits two parts, a straight line with a Mark–Houwink exponent 0.7 in the low molecular weight region and a curvature, well smoothed by a third‐degree polynomial regression. Consequently, long chain branching does not appear before a limiting molecular weight of about 50,000. Beyond this limit, λ is 0.5 × 10−4, with no dependence on molecular weight, which resembles low density polyethylene.
Resistivity behavior of filled electrically conductive crosslinked polyethylene
Authors: Narkis M. , Vaxman A.
Published: April 2003

The electrical resistivity of crosslinked high‐density polyethylene loaded with conductive blacks and carbon fibers was studied as a function of filler concentration and temperature. A thermoelectric switching phenomenon (a sudden resistivity increase in the vicinity of the polyethylene melting point) in such semicrystalline conductive systems was investigated. Significant switching behavior was exhibited by compounds containing very low concentrations of carbon fibers. Some crosslinked compounds filled with mixtures of carbon black and carbon fibers were also studied.
Compatibility and thermal stability studies on PVC/chlororubber‐20‐graft polyblend‐styrene–vinyl acetate–acrylonitrile blends. II
Authors: Singh Y. P. , Singh R. P.
Published: April 2003

Compatibility and Thermal stability studies have been performed on PVC blends with chlororubber‐20‐graft polyblend‐styrene–vinyl acetate–acrylonitrile (1:1:1) [CR‐20gp‐SVAAN (1:1:1)]. The grafting of styrene, vinyl acetate, and acrylonitrile onto chlororubber‐20 backbone chain generates some amount of heterogeneity in the system. The compatibility behavior of PVC/CR‐20gp‐SVAAN (1:1:1) blends has been reflected in the ultrasonic velocity and absolute viscosity vs. composition plots of the blend. These blends have been found to be thermally miore stable than PVC/chlororubber‐20 blends, but less stable than PVC/KM‐365B blends. The rate of degradation is equal to that of the PVC/chlororubber‐20 blends. The results have been discussed on the basis of compatibility, stabilizing, and destabilizing behavior of various component polymers with PVC matrix.
Compatibility of poly(ϵ‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) (SAN) blends. II. The influence of the AN content in SAN copolymer upon blend compatibility
Authors: Chiu Shao‐Cheng , Smith T. G.
Published: April 2003

The compatibility of polymer blends of poly(ϵ‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) (SAN) containing various acrylonitrile (AN) contents was studied to evaluate the influences of copolymer composition and PCL concentration upon blend compatibility. Blend compatibility was characterized by the occurence of a single glass transition intermediate between the transitions of the respective pure components. The glass transitions were determined by differential scanning calorimetry (DSC) and dynamic mechanical measurement (Rheovibron). It was found that SAN and PCL form compatible blends when the AN content of SAN ranges from 8% to 28% by weight. These blends are compatible in all proportions except for SAN 28 (AN wt % = 28) and PCL blends containing 70 or 85 wt % PCL. Blends of PCL and SAN were found to be incompatible when the AN content in SAN is greater than 30 wt % or less than 6 wt %. Lower critical solution temperature (LCST) behavior, which can be attributed to phase separation, was found to occur when these blends were heated to elevated temperatures. The cloud point, or phase separation, was found to vary with AN content in SAN and the concentration of SAN in the blend.
Critical stress for crystallization in the threadline during high‐speed spinning of poly(ethylene terephthalate)
Authors: Garg Sunil K.
Published: April 2003

The development of structure during steady‐state high‐speed spinning of poly(ethylene terephthalate) has been correlated with the stress on the threadline. In particular, it is shown that a critical stress at the freeze point of 0.08–0.09 g/denier (9.5–10.6 MPa) is necessary for the occurrence of threadline crystallization independent of polymer molecular weight or process variables such as windup speed or filament character.
Photoacoustic study of UV, UV–thermal, and weathering degradation of rigid foam polyurethane
Authors: Abu‐Zeid M. E. , Nofal E. E. , Tahseen L. A. , Abdul‐Rasoul F. A. , Ledwith A.
Published: April 2003

Degradation of polyurethane samples by UV, combination of UV–thermal, and natural weathering were studied by photoacoustic spectroscopy. This study reveals that degradation of polyurethane could be initiated at a relatively low temperature of 40°C and low UV dosage. It was also found that the effect of heat is more pronounced than the effect of UV. The reaction mechanism of polyurethane degradation is fully in agreement with photoacoustic absorption spectra.
Experimental measurements and monte‐carlo simulation of water diffusion into epoxy matrices
Authors: Majerus M. S. , Soong D. S. , Prausnitz J. M.
Published: April 2003

Sorption and desorption data are reported for water in epoxy at 25°C and 70°C. A Monte Carlo model based on the dual‐sorption theory is formulated to explain observed diffusion behavior. Random walk of particles is followed through a regular lattice with randomly distributed adsorption sites. Comparison of predicted results with experiment shows that the model predicts sorption data well. A modification to the model is proposed to improve prediction of desorption data.
Polyurethane ionomers. I. Structure–properties relationships of polyurethane ionomers
Authors: Hsu S. L. , Xiao H. X. , Szmant H. H. , Frisch K. C.
Published: April 2003

The influence of chemical structure on mechanical properties of polyurethane ionomers (PU ionomers) has been examined. NCO‐terminated prepolymers prepared from primarily 4,4‐methylene bis(phenyl isocyanate) (MDI) and poly(oxytetramethylene) glycol (PTMO) were chain extended with tertiary amine‐containing diols and the ionomers obtained by quaternization of the prepolymers. The N‐methyldiethanolamine chain extender gave the best physical properties. The mechanical properties of the PU ionomers were improved with decreasing chain length of PTMO and with increasing concentration of quaternary ammonium centers (or NCO/OH ratio of PU prepolymers). A lower degree of quaternization resulted in a decrease in the mechanical properties of the resulting PU ionomers, but their properties could be improved by post‐quaternization. The adhesion of the PU ionomers to aluminum and the glass transition temperature increased with increasing concentration of quaternizing centers.
Curing reaction of epoxy resins with diamines
Authors: Riccardi C. C. , Adabbo H. E. , Williams R. J. J.
Published: April 2003

The curing reaction of a commercial bisphenol A diglycidyl ether (BADGE) with ethylenediamine (EDA) was studied by differential scanning calorimetry. Different kinetic expressions were found with isothermal (low temperature range) and dynamic (high temperature range) runs. Two competitive mechanisms are shown to be present: an autocatalytic one (activation energy E = 14 kcal/mol) and a noncatalytic path characterized by a second‐order reaction with E = 24.5 kcal/mol. At low temperatures both mechanisms took place simultaneously, showing a significant decrease in the reaction rate after the gel point. At high temperatures only the noncatalytic reaction was present, without showing a noticeable rate decrease in the rubber region. Also, a third‐order dependence of the glass transition temperature on reaction extent is shown.
Biodegradability of photooxidized polyalkylenes
Authors: Cornell John H. , Kaplan Arthur M. , Rogers Morris R.
Published: April 2003

Representative polyolefin films were exposed to UV radiation from light sources having different intensities and spectral distribution including the quartz mercury arc fluorescent lamps, xenon arc, and sunlight. Films exposed were polyethylene, polypropylene, and sensitized polyethylene. The oligomer fractions supported microbial growth, but the high polymers gave minimal or no growth. It was concluded that photooxidative degradation of polyolefins does not per se induce progressive attack by microorganisms. Oligomers present originally in the polymer are augmented by those produced by photooxidation. These oligomers support growth if separated from the polymer matrix. These observations explain some of the contradictory reports in the literature concerning the microbial degradation of sensitized polyolefins.
Electric conductivity of silicone elastomers vulcanized by the hydrosilation reaction
Authors: Yokoyama Takashi , Kinjo Noriyuki
Published: April 2003

Electrical conductance and hardness of silicone elastomers, prepared by the vulcanization reaction of hydrosilyl groups with vinyl groups in the presence of platinum catalyst, were measured. It is shown that the electric conductivity of the elastomers decreases as hardness increases and as the temperature decreases. An empirical equation is derived expressing electric conductivity σ as a function of hardness H and absolute temperature T, log σ = −0.03H − 3200/T − 3, where σ is S/m and H is Shore A, over the temperature range of 100–150°C.
ESCA study of oxidized wood surfaces
Authors: Hon David N.‐S.
Published: April 2003

Results 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

A 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

Numerous 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

It 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

The 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

Acrylate 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

Viscosity–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

Structural 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

A 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

A 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

Methyl 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

The 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

The 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

The 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

By 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

The 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

Blending 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

Bisglycidyl 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

A 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

The 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

This 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

Differential 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

The 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.
Processable aromatic polyimides
Authors: Burks Harold D. , St. Clair Terry L.
Published: April 2003

Two similar polyimide systems were synthesized and characterized. The only structural difference was a sulfide linkage in the anhydride‐derived portion of the first system vs. a sulfone linkage in the second. Their physical, mechanical, melt‐flow and thermal properties, and their resistance to some of the more common solvents were determined. The flow properties of these polyimides indicate a potential for melt processability.
Plasticization of glassy polymers by CO2
Authors: Chiou J. S. , Barlow J. W. , Paul D. R.
Published: April 2003

A technique is described which uses differential scanning calorimetry to estimate the glass transition of polymers containing a dissolved gas. The technique is simple and appears to give reliable results. The effects of CO2 sorption at pressures up to 25 atm were examined in detail for poly(methyl methacrylate) and its blends with poly(vinylidene fluoride). Less extensive results for polystyrene, polycarbonate, poly(vinyl chloride), and poly(ethylene terephthalate) are also given. Reductions in Tg of up to 50°C are observed. A theoretical relation by Chow predicts results in reasonable agreement with the experimental data. These findings are relevant to various applications such as membrane separation processes for gases.
Free‐radical grafting of cellulose in N‐methylmorpholine oxide: Water‐soluble pam‐g‐cellulose copolymers
Authors: Nelson Edward C.
Published: April 2003

The homogeneous graft copolymerization of acrylamide (AM) onto cellulose initiated by t‐butylperoxy‐2‐ethylhexanoate in a cellulose solvent, N‐methylmorpholine oxide (NMMO), was investigated. The method afforded water‐soluble PAM‐g‐cellulose copolymers in fair yields. The copolymers produced are of low molecular weight (50,000–100,000 M̄w). Little apparent homopolymerization was observed.
The effect of heat on the molecular weight of poly(ethyl 2‐cyanoacrylate) adhesive
Authors: Guthrie J. , Otterburn M. S. , Rooney J. M. , Tsang C. N.
Published: April 2003

Steel–steel ethyl 2‐cyanoacrylate adhesive bonds have been thermally aged and the polymeric material isolated from the glue line. Molecular weight measurement by gel permeation chromatography suggest that a significant degree of post‐curing occurs followed by a slight decrease in molecular weight. This decrease in molar mass is not considered large enough to explain the observed decrease in bond strength. It is postulated that poly(ethyl 2‐cyanoacrylate) undergoes thermal degradation in a manner similar to that reported for poly(methyl methacrylate). The loss in bond strength is thought to be due to the disruption of the polymer–metal interface by monomer molecules produced during the thermal depolymerization.
Analysis of the flow behavior of irradiated polyethylene through transient network models
Authors: García‐Rejón A. , Manero O. , Rangel‐Nafaile C.
Published: April 2003

The chemical and physical properties of polymers can be dramatically affected by exposure to high‐energy radiation. Two polyethylene samples (HDPE and LDPE) were irradiated with a 60Co source. Radiated samples with doses ranging between 0.5 and 5 Mrad were melted and their viscoelastic properties characterized. Results show the normal drastic changes in their flow behavior: higher viscosity and interesting changes induced in their elasticity, particularly in the case of LDPE. An explanation of the change in flow behavior is forwarded in terms of transient network models using the concept of creation and destruction of entanglements.
Curing of epoxy resins with diphenyliodonium salts as thermal initiators
Authors: Gu Juesheng , Narang Subhash C. , Pearce Eli M.
Published: April 2003

The curing reaction of a thermally curable epoxy system containing diphenyliodonium hexafluoroarsenate was investigated by using the dynamic and isothermal techniques of differential scanning calorimetry (DSC). It was shown that the curing involved two consecutive reactions. The heat of the total curing reaction and overall kinetic parameters for the two reactions were obtained.
Hydrolysis of cellulose fiber in the presence of 12‐tungstosilicic acid
Authors: Arai Kenichiro , Ogiwara Yoshitaka
Published: April 2003

Hydrolysis of cellulose fiber in the presence of 12‐tungstosilicic acid was investigated, and the acid was found to show a higher catalytic activity than did hydrochloric acid at the same concentration of acid, although the ratio of the activities of 12‐tungstosilicic acid to hydrochloric acid depended on the concentration. The influence of the ionic strength on the reaction rates was examined, and it was believed that the difference in the ionic strength between 12‐tungstosilicic acid and hydrochloric acid at the same concentration of acid was one of reasons for the higher catalytic activity of 12‐tungstosilicic acid. From the examinations of change in degree of polymerization of the cellulose fiber with the hydrolysis and adsorption behavior of 12‐tungstosilicic acid by the cellulose, fiber, it was found that 12‐tungstosilicic acid, in spite of its bulky structure, easily penetrated into the amorphous region of the cellulose fiber, as does hydrochloric acid, and catalyzed the hydrolysis of glucoside bond there.
A chemical means to study the in vitro hydrolytic degradation of poly(glycolic acid)
Authors: Chu Chih‐Chang , Louie May
Published: April 2003

A chemical means was developed to examine the in vitro hydrolytic degradation of both γ‐irradiated and nonirradiated poly(glycolic acid) (PGA)‐absorbable polymers for the purpose of obtaining information how irradiation affected PGA degradation and how the results related to the previously observed mechanical and morphological data. The method was based on the chemical reaction between the degradation product of the polymer, glycolic acid, and chromotropic acid, and the subsequent measurement of the absorbance of the reaction products by a UV/visible spectrophotometer. It was found that the unirradiated PGA specimens exhibited a two‐stage hydrolytic degradation mechanism. This observation supported the previously hypothesized hydrolytic degradation mechanism on the basis of the level of crystallinity data. As the dosage of irradiation increases, the characteristic two‐stage degradation mechanism becomes less profound and eventually disappears at 20 Mrads. A monotonic degradation profile was then observed at this dosage level. As reported in the literature, the widespread use of mechanical properties to evaluate the degradation phenomena of this class of polymer does not, however, provide the details of the degradation mechanism as revealed by the present study. The interrelationship between tensile strength, level of crystallinity, glycolic acid concentration, and pH levels of the medium, and their changes as hydrolytic degradation proceeds, are discussed for the purpose of elucidating the mechanism in more detail.