bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recovery of indan derivatives from polystyrene waste
Authors: Ogawa Taichi , Kuroki Takeshi , Ide Shoaki , Ikemura Tadashi 
Published: April 2003

AbstractThe recovery of indan derivatives from polystyrene waste for the purpose of efficient utilization of plastic wastes was studied. An attempt was made to construct the apparatus, in which thermal decomposition of polystyrene and catalytic reaction of its decomposition products over silica–alumina catalyst could be controlled continuously at the same time. The reaction temperature for thermal decomposition of polystyrene in the upper part of a reactor tube was 420°C, while that for catalytic reaction of the thermal decomposition products in the bottom of a reactor tube was 300°C. These results indicated that the composition of thermal decomposition products of polystyrene could be controlled by the use of a flow reactor. The indan derivatives recovered were two 1‐methyl‐3‐phenylindans, one 1‐methyl‐1‐phenylindan, and 1‐phenylindan. The yields of these indan derivatives were 20% of the weight of the liquid products recovered. On the basis of the results obtained in the present work, the most suitable reaction conditions to recover indan derivatives from polystyrene waste is discussed.
The curing of novolacs with paraformaldehyde
Authors: Adabbo H. E. , Williams R. J. J. 
Published: April 2003

AbstractThe curing of novolacs with paraformaldehyde is analyzed with several experimental techniques (DSC, IR, sol fraction) as well as statistical arguments. Results for typical novolacs show that a maximum crosslinking density is attained at a mass ratio mP/mN close to 0.20. However, at mP/mN greater than 0.10, hemiformals appear in the cured product, increasing the amount of extractable formaldehyde. The heat of reaction increases linearly from mP/mN = 0 to 0.15, attaining a maximum value of −ΔH = 98 cal/g novolac at mP/mN ∼ 0.20. The curing kinetics follows an overall second‐order law with an activation energy E = 32.5 kcal/mol and a preexponential factor A = 1.1 × 1015 min−1 (both for mP/mN > 0.1).
Straining phenomena of POY revealed by thermal retraction and other techniques
Authors: Selivansky Dror , Lewin Menachem 
Published: April 2003

AbstractPartially oriented polyesters yarns (POY) were strained at different strain rates (0.03–12.00 min−1) and temperatures above and below Tg (3–92°C). Thermal retraction, density, DSC, and WAXS techniques show that strain‐induced crystallization takes place by straining at temperatures above as well as below Tg. Above Tg, depending upon the strain rate, two regimes are observed: Below the strain rate of 1.5 min−1, the flow regime; the degree of crystallinity is reduced as the strain rate increases. Above the strain rate of 1.5 min−1, the strain‐induced crystallization regime; the degree of crystallinity increases as the strain rate increases. Thermal retraction, stress–relaxation, and sonic modulus techniques indicate that, upon cold straining, instead of the original Tg at 65–69°C, two glass transitions occur: an upper Tg (u) and a lower Tg (l). For POY strained at 3°C and at a strain rate of 10 min−1, the values are 78°C and 37°C, respectively. The higher the strain rate and the lower the straining temperature, the large the difference between Tg (u) and Tg (l).
Thermal oxidation of polypropylene close to industrial processing conditions
Authors: Hoff Ariel , Jacobsson Sven 
Published: April 2003

AbstractThermal oxidation of isotactic polypropylene (PP) at 220 and 280°C in air was studied. Gas chromatography–mass spectrometric analysis was used to separate and identify the volatile products of PP oxidation. Twenty‐three products were identified and 15 substances were quantified. The aldehydes are the principal products formed, followed by ketones, acids, and alcohols. The main organic product quantified was acetaldehyde. The volatile organic products formed constitute about 3% of the amount of water formed. The relative amounts of the most volatile products formed in the range 220–280°C are practically independent on the temperature of oxidation. The mechanism of formation on the oxidation products is discussed.
Phase separation in segmented polyurethanes
Authors: Kwei T. K. 
Published: April 2003

AbstractPhase separation in a segmented polyurethane has been studied by differential scanning calorimetry. The glass transition temperature of the soft phase decreases logarithmically with time to a limiting value at each annealing temperature. The magnitude of the decrease is larger at low annealing temperatures, but the normalized rate of logarithmic decrease is smaller. At high annealing temperatures, long sequences of hard segments are excluded from the soft phase in which short segments are still soluble. At low temperatures, even short hard segments separate from the soft phase. The exclusion of the hard segments from the soft phase is a relatively fast process, but the development of order in hard domains takes longer time to reach steady state.
Non‐steady‐state transport of diffusants in ternary laminate slabs
Authors: Le Poidevin Graham J. 
Published: April 2003

AbstractEquations describing transient diffusion in ternary laminate slabs are presented. The equations developed can be applied to: (I) asymmetric ABC slabs separating two semi‐infinite baths, each bath containing either the same or different concentration(s) of permeant; (II) asymmetric ABC slabs separating a semi‐infinite bath from an impermeable substrate; (III) asymmetric ABC slabs with impermeable substrates attached to laminas A and C. Further, the equations can be applied to slabs containing initially uniform, but not necessarily equilibrial, concentrations of permeant in each lamina. Some numerical examples of the aforementioned diffusion systems I and II are discussed.
Gas sorption and transport in poly(phenylene oxide) and comparisons with other glassy polymers
Authors: Toi K. , Morel G. , Paul D. R. 
Published: April 2003

AbstractThe sorption and transport of several gases in poly(phenylene oxide) were measured at 35°C, and the results have been analyzed in terms of the dual sorption/mobility models which have been successfully employed for this purpose for other glassy polymers. Both the extent of sorption and rate of permeation of gases are quite large for poly(phenylene oxide) compared to other glassy polymers with rigid chain backbones. It is shown that the high extent of sorption is owing to the high glass transition temperature of this polymer, but this is not a significant factor in its high permeability to gases. The latter stems from large diffusion coefficients. It is shown that the capacity of the Langmuir mode of sorption inherent to glassy polymers is related to the value of the glass transition temperature in a general way for a wide variety of polymers. Observations about the diffusion coefficients for numerous gas–polymer pairs are discussed.
Glass‐transition behavior of particle composites modeled on the concept of interphase
Authors: Theocaris P. S. , Spathis G. D. 
Published: April 2003

AbstractThe thermomechanical behavior of particle composites was investigated in their transition region. In particular, the value of the glass‐transition temperature Tg, which constitutes an upper limit for the structurally important glassy region, was examined. According to experimental evidence existing in the literature the introduction of a reinforcing filler in a polymeric matrix causes Tg of the latter to increase, unless mechanical imperfections counterbalance the reinforcing effect or even produce a Tg for the composite which is lower than that of the matrix. Based on mechanical theories, valid for the mechanical moduli of viscoelastic particle composites, a model was introduced that explains why the glass transition of composite materials may be reduced in some cases, whereas it may be increased in others. The concept of interphase between inclusions and matrix was used for the development of the model. Interphase is assumed to be a region, which is created between the matrix material and the filler particles, both considered as homogeneous and isotropic, whose thermomechanical properties and volume fraction may be determined from the overall thermomechanical behavior of the composite.
Stress‐induced chemiluminescence from nylon 66 fibers
Authors: George G. A. , Egglestone G. T. , Riddell S. Z. 
Published: April 2003

AbstractThe emission of visible light during the tensile deformation of medium‐ and high‐tenacity nylon 66 yarns in air has been studied at strain rates of 0.63–200%/min and at temperatures of 20–110°C. Emission is observed only in an oxidative atmosphere and increases with temperature according to an Arrhenius relation. The activition energy decreases with applied stress. The intensity at any temperature can be described by the sum of a component linear with stress and another exponential in stress above ∼60% of the ultimate strength. These results and the measured spectral distribution suggest that light emission arises from bimolecular termination of alkyl peroxy macroradicals. The chemiluminescence growth curves indicate that the applied stress increases the oxidation rate of the fiber due to internal and external frictional heating while, at high strains, stress‐induced main‐chain scission occurs up to fiber failure. The growth curve is sensitive to the load history of the fiber. The chemiluminescence decay curves are a sensitive probe of radical reactions such as cage termination and stabilizer scavenging in the amorphous region of the polymer.
Yields and composition of sirups resulting from the flash pyrolysis of cellulosic materials using radiant energy
Authors: De Jenga Chine I. , Antal Michael Jerry , Jones Maitland 
Published: April 2003

AbstractCellulosic materials have been flash pyrolyzed using concentrated solar energy. The sirups obtained were composed mainly of levoglucosan. Radiant flash pyrolysis has thus been identified as a potentially attractive means of selectively degrading biomass material into good yields of relatively few products. The techniques and equipment employed to determine the composition of the pyrolyzates are described.
Epoxy‐resin‐cured carboxylated nitrile rubber
Authors: Chakraborty Sunity K. , De Sadhan K. 
Published: April 2003

AbstractCuring of carboxylated nitrile rubber (XNBR) with epoxy resin in presence of different fillers has been studied. It was observed that 7.5 phr of resin give a compromise combination of properties in FEF black (N 550)‐filled vulcanizates at 40 phr loading. Further studies at different loadings of black, reinforcing silica and clay were done at 7.5 phr resin. Technical properties at different filler loadings have been determined. Polymer‐filler interaction involving FEF black, silica, and clay was examined by a Kraus plot and the equation of Lorenz and Parks. Silica and carbon black give a similar type of reinforcement, but clay shows nonreinforcing characteristics. In the case of carbon black–XNBR system, polymer‐filler attachment is similar to that existing in carbon black–natural rubber system. In the case of silica, reaction of the silanol group with the epoxide group of the epoxy resin and the carboxyl group of the base polymer may be responsible for the polymer‐filler attachment. Scanning electron microscopy (SEM) studies of the fracture surfaces corroborate the findings on technical properties and polymer‐filler interaction.
Grafting of methyl methacrylate onto collagen initiated by tributylborane
Authors: Kojima Kuniharu , Iguchi Shuichi , Kajima Yoshihiro , Yoshikuni Masako 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate onto collagen initiated by tributylborane was investigated in aqueous medium. The total conversion, percentage of grafting and efficiency of grafting increased with increasing collagen content. The optimum conditions on the percentage of grafting and efficiency of grafting were determined by varying initiator concentration, monomer concentration, and polymerization temperature. The grafting onto denaturated collagen was also studied. It has been suggested that the grafting onto collagen proceeds by a radical mechanism via a complex of TBB and hydrated collagen.
Preparation of high‐modulus and high‐strength isotactic polypropylene fiber by zone‐annealing method
Authors: Kunugi Toshio , Ito Taihei , Hashimoto Minoru , Ooishi Masashi 
Published: April 2003

AbstractThe zone‐annealing method was utilized to prepare a high‐modulus and high‐strength fiber from isotactic polypropylene. The dynamic storage modulus at room temperature of the fiber obtained reached 21 times; 1010 dyn/cm2, which corresponded to 51% of the crystal modulus along the molecular chains, 41.2 × 1010 dyn/cm2. The relationships between mechanical properties and superstructure were investigated based on results of measurements of orientation, crystallinity, tensile properties, and dynamic viscoelasticity. It was found that the excellent mechanical properties were directly attributed to the large number of tie molecules and to the high orientation of the amorphous chains. Further, the characteristics of this method were discussed compared with the results obtained by other investigators.
Polycaprolactone degradation by mixed and pure cultures of bacteria and a yeast
Authors: Benedict Christine V. , Cameron J. A. , Huang Samuel J. 
Published: April 2003

AbstractThe degradability of three high molecular weight polycaprolactones (M̄w = 35,000, 18,600, and 7,130) and one low molecular weight polycaprolactone diol(M̄w = 2060) by mixed and pure cultures of microorganisms was assayed. A yeast, Cryptococcus laurentii, a gram‐negative rod, Acinetobacter calcoaceticus var. lwoffi, and a gram‐positive coryneform rod were used in the pure culture assays. The analysis of degradation by gel permation chromatography (GPC) allowed for quantitation independent of the growth of the organisms or the addition of supplementary growth factors. GPC analysis showed that the degradation effected by pure cultures was often enhanced when alternate carbon sources were present. This was not the case for mixed cultures. Mixed cultures. Mixed cultures completely metabolized polymer breakdown products while in some cases pure cultures did not.
Dielectric loss behavior of cross‐linked polyethylene and analog materials
Authors: Jang Y. T. , Phillips P. J. 
Published: April 2003

AbstractThe dielectric loss behavior of crosslinked polyethylene has been determined over the frequency range 10–5 kHz and over the temperature range −150 to 100°C. Major loss effects occur at the lower temperatures and are caused by libration of the organic byproducts of the crosslinking agent, dicumyl peroxide. Analog materials prepared from linear low density polyethylene by blending in of either acetophenone or 2‐phenyl‐2‐propanol confirm the hypothesis. The effects of concentration of by products and of orientation of the polymer have been studied. Activation energy analyses suggest that room temperature losses will occur in the microwave region. The behavior is significantly affected by curing with steam, typical loss peaks being an order of magnitude lower than for dry cured specimens. A new loss region appears close to but below, 0°C.
Polypropylene/nylon 6 blends: Phase distribution morphology, rheological measurements, and structure development in melt spinning
Authors: Liang Bo‐Run , White James L. , Spruiell Joseph E. , Goswami Bhuvenesh C. 
Published: April 2003

AbstractA series of polypropylene (PP)/nylon 6 (N6) blends of composition 75/25, 50/50, and 25/75 have been prepared in a screw extruder combined with a Koch static mixer. The phase morphology was observed with a scanning electron microscope. The influence of heating in the reservoir of a rheometer followed by subsequent extrusion through a capillary on the phase morphology was investigated. Phase size growth as a function of time was observed under quiescent and mild deformation rate conditions. The discrete phase size was observed to decrease with increasing extrusion rate through dies. The shear viscosity and principal normal stress difference of the blends were measured as a function of composition. The crystalline orientation of both polypropylene and nylon 6 in blend melt spun fibers was characterized by wide angle X‐ray diffraction and interpreted in terms of Hermans–Stein orientation factors. The orientation increases with drawdown ratio. The orientation factors for the polypropylene phase vary with spinline stress in a manner independent of composition and identical to that for pure polypropylene. Extracting melt spun blend fibers with formic acid has produced small‐diameter polypropylene minifilaments with diameters of the order of microns.
Determination of number‐average and weight‐average molecular weights of polymer sample from diffusion and sedimentation velocity measurements in theta solvent
Authors: Okabe Masaru , Matsuda Hideomi 
Published: April 2003

AbstractSeveral methods to determine number‐average molecular weight Mn and weight‐average molecular weight Mw, of a polymer sample are proposed from diffusion and sedimentation velocity measurements at the θ point. According to these methods, Mn and Mw are determined from the diffusion constant vs. molecular weight relationship, and also from the equations of Svedberg and Flory–Mandelkern, using the 2nd‐order and the –2nd‐order diffusion constants. These methods have been applied to four samples of polydisperse polystyrene in the θ solvent, cyclohexane at 35°C. It was experimentally ascertained that Mn and Mw of each sample determined by the present methods were in good agreement with the results of column fractionation, light scattering, and calculated values from molecular weight distribution curve within experimental errors. It is concluded that the present methods are useful for determining Mn and Mw, since the reliabilities of Mn and Mw values, which are fundamental quantities of polymer characterization, can be raised by comparing the experimental data observed by conventional methods such as osmotic pressure, light scattering, and the Archibald method with those observed by the present methods.
Time–temperature–transformation (TTT) cure diagram: Modeling the cure behavior of thermosets
Authors: Enns John B. , Gillham John K. 
Published: April 2003

AbstractThe times to gelation and to vitrification for the isothermal cure of an amine‐cured epoxy (Epon 828/PACM‐20) have been measured on macroscopic and molecular levels by dynamic mechanical spectrometry (torsional braid analysis and Rheometrics dynamic spectrometer), infrared spectroscopy, and gel fraction experiments. The relationships between the extents of conversion at gelation and at vitrification and the isothermal cure temperature form the basis of a theoretical model of the time–temperature–transformation (TTT) cure diagram, in which the times to gelation and to vitrification during isothermal cure versus temperature are predicted. The model demonstrates that the “S” shape of the vitrification curve depends on the reaction kinetics, as well as on the physical parameters of the system, i.e., the glass transition temperatures of the uncured resin (Tg0), the fully cured resin (Tg∞), and the gel (gelTg). The bulk viscosity of a reactive system prior to gelation and/or vitrification is also described.
Solid‐state polymerization of poly(ethylene terephthalate)
Authors: Chang Shuya , Sheu Ming‐Fa , Chen Shu‐May 
Published: April 2003

AbstractSolid ‐state polymerization of poly(ethylene terephthalate) (PET) is carried out by heating the low molecular weight prepolymer at temperatures below its melting point but above its glass transition temperature. Postcondensation occurs and the condensation byproducts can be removed by applying vacuum or inert gas. Polymers obtained usually have high molecular weight, low carboxyl and acetaldehyde content, and can be used for beverage bottle or industrial yarns. Polyesters for textile purposes are manufactured by a melt process. Chemical reactions involved in the solid state polymerization are transesterification, esterification, as well as the diffusion of byproducts. Overall reaction rate was governed by the molecular weight, carboxyl content of prepolymer, crystallinity, particle size, reaction temperature, and time. Prepolymer for solid state polymerization should have intrinsic viscosity 0.4 dL/g or more, density 1.38 g/mL, and minimum dimension 3 mm or less. The reaction temperature could be 200–250°C. When textile grade PET is used as prepolymer, crystallization at 180–190°C for 1–2 h increases the density to 1.38 g/mL. Polymerization at 240–245°C for 3–5 h can raise the intrinsic viscosity to 0.72 dL/g and carboxyl content less than 20 meq/kg. Appropriate reaction conditions are subject to the properties of prepolymers and the design of reactors. Reactor used for solid state polymerization could be vacuum dryer type or stationary bed. The former is suitable for a small capacity and is run batchwise. The latter is a continuous process and is economically feasible for large ‐scale production.
Hydrolytic degradation of cured urea–formaldehyde resin
Authors: Dutkiewicz Jacek 
Published: April 2003

AbstractThe degradation of cured urea–formaldehyde (UF) resin in aqueous suspension was investigated by gravimetric analysis of the changes in the content of nonextractable low‐molecular components. In acid conditions (pH 4.0) at 47°C the consecutive processes of post‐curing and of polymer break‐down (activation energy 90 kJ/mol) are detectable whereas at 80°C and 97°C only the formation of the extractable hydrolysates is observed. The degraded polymer contains less carbonyl groups than does the original resin substrate as shown by means of infrared (IR) analysis. In contrast to the results of the tests carried out in acid conditions, in neutral and basic aqueous media the hydrolytic decomposition of UF macromolecular network is less significant. During the hydrolysis of UF polymer at 30°C–45°C the concentration of formaldehyde released from the resin to the aqueous phase increases initially (2 days) at a relatively high rate both at acid and alkaline pH. Then its growth slows down but is still detectable in acid conditions, whereas in basic medium no further liberation of HCHO is observed.
Semi‐ and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. III. Polyurethane–poly(methyl acrylate) semi‐2‐interpenetrating polymer networks
Authors: Hourston D. J. , Zia Y. 
Published: April 2003

AbstractTwo series of semi‐2‐IPNs based on a polyurethane and a poly(methyl acrylate) crosslinked with divinyl benzene were prepared and investigated using dynamic mechanical analysis, sonic velocity measurements, and electron microscopy. In the one series, the level of crosslinking was varied to give ultratight networks. In the other, the composition was altered, but the amount of the crosslinking agent used was kept constant. For the first series, it was concluded that the degree of crosslinking had a significant influence on the morphology and properties by controlling the amount of enforced mixing. The dynamic mechanical data for the second series fitted the Davies modulus–composition equation, indicating that both phases are continuous.