bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐condensation of oxidized lignosulfonate. II. Condensation behaviors
Authors: Chen Rubie , Wu Guoxiong 
Published: April 2003

AbstractStudies have been made on the principal parameters that affect the self‐condensation of oxidized lignosulfonate, such as lignin content, pH, temperature, time of hot pressing, and oxidation. During condensation, the hydroxyl groups in both the lignosulfonate and carbohydrate molecules could react with carboxyl, sulphonic acid, and carbonyl groups to form an ester bond and result in (hemi) ketal and (hemi) acetal structures. These structures made condensation products having excellent resistance in water and in alkaline solutions. The results also demonstrated that the oxidized lignosulfonate could be condensed at a higher rate than could the untreated one.
Invariant kinetic parameters of polymer thermolysis. III. The influence of a fire‐retardant additive on polypropylene thermolysis
Authors: Vyazovkin S. V. , Bogdanova V. V. , Klimovtsova I. A. , Lesnikovich A. I. 
Published: April 2003

AbstractThe present paper analyzes the thermolysis gross‐kinetics of polypropylene (PP) and a PP‐based fire‐resistant composition containing 10% of hexabrominecyclododecane (HBCD) as the fire‐retardant additive. The kinetic parameters of thermolysis of an individual PP are calculated by the isoconversion method. The increasing dependence of the effective activation energy on the transformation degree has been established. This dependence is attributed to the competitive character of the processes of thermodestruction initiated by oxidation and to the PP pyrolysis. Thermolysis in the helium atmosphere leads to oxidation suppression and increases the effective activation energy at the initial stage of thermolysis. A similar effect can be attained by introducing HBCD into PP, which permits considering the ability of inhibiting the oxidation process proceeding in the condensed phase as one of the reasons of the fire‐retardant activity of this additive.
Analysis of reaction‐injection‐molded polyurethanes by near‐infrared diffuse reflectance spectroscopy
Authors: Miller Charles E. , Eichinger B. E. 
Published: April 2003

AbstractThe ability of near‐infrared (NIR) diffuse reflectance spectroscopy to characterize reaction‐injection‐molded (RIM) polyurethane elastomers is demonstrated. The advantage of NIR spectroscopy over other analytical methods is its ability to analyze samples without any preparation. In this work, the specific effects of composition, density, phase separation, and moisture content on the NIR spectra of the polymers are identified. In addition, the ability of NIR spectroscopy to make rapid assessments of physical properties, such as heat sag and flex modulus, is demonstrated. In order to perform these analyses, the multivariate statistical methods of principal components analysis (PCA) and partial least squares (PLS) are used.
Preparation of asymmetric film by blending two kinds of polymer emulsions having greatly different storage stabilities
Authors: Okubo Masayoshi , He Yuan 
Published: April 2003

AbstractTwo kinds of anionic polymer emulsions with different particle sizes were blended and cast on a release‐paper at 30°C. One was poly(butyl acrylate) emulsion, and the other was ethyl acrylate–methyl methacrylate (1 : 1, weight ratio) copolymer emulsion. They were produced by emulsifier‐free emulsion polymerization. The blend films prepared in an appropriate range of the blend ratio had a great difference in tackiness between both surfaces: The air‐side surface exhibited tackiness and the release‐paper side showed nontackiness. The forming mechanism is discussed.
Kinetics and properties of a photopolymerized dimethacrylate oligomer
Authors: Cook Wayne D. 
Published: April 2003

AbstractThe free radical photopolymerization of two urethane dimethacrylate oligomer systems, used in dentistry as elastomeric impression materials, was investigated. When cured in thick section, these materials have a limited depth of cure that depends on the irradiation conditions. A mathematical model is presented that considers the spatial dependence of the polymerization process on the attenuated radiation intensity and the local concentration of radical scavenging inhibitors. The predicted dependence of the depth of cure on the logarithm of radiation intensity and exposure time is confirmed. DSC studies revealed that for thin sections the rate of polymerization had the conventional square root dependence on radiation intensity over a 1000‐fold range of intensities. These results are discussed in terms of a decoupling of the mobility of the pendant methacrylate group from the chain to which it is attached. In an oxygen environment, inhibition of the photopolymerization caused an induction period that was proportional to the reciprocal radiation intensity. Modulus measurements during cure also illustrated the rapid nature of photopolymerization process and showed that in comparison to conventional two‐component materials used for the same purpose the rates of buildup in properties for the photocured materials were superior. The tear energy of the cured photocured materials were compared with conventional types of elastomeric impression material, and the differences were interpreted in terms of energy dissipation mechanisms.
Model esterification of neopentyl glycol and trimethylol propane with 1,4‐tert‐butyl benzoic acid
Authors: McCarthy Jennifer L. , Scholtens Boudewijn J. R. 
Published: April 2003

AbstractThe esterification kinetics of difunctional neopentyl glycol and trifunctional trimethylol propane with monofunctional 1,4‐tert‐butyl benzoic acid was studied in the melt phase at 200°C in the presence of a metal catalyst. The rate of conversion was monitored via titrations and by determination of the relative concentrations of products and reactants using HPLC with a UV detector. A small but significant positive substitution effect was found for neopentyl glycol (KDA = 1.15) and none was found for trimethylol propane. The reaction rate constant of neopentyl glycol with the acid is about 40% higher than that of trimethylol propane with the acid. A second‐order overall reaction order was used to compute the rate constants.
Studies on the preparation and properties of conductive polymers. III. Metallized polymer films by retroplating out
Authors: Huang Chueh‐Jung , Yen Chih‐Chao , Chang Teh‐Chou 
Published: April 2003

AbstractA novel method to prepare polymer metallized films was found by using polymer metal chelate films treated with wetted metal plates (or metal powders). The polymer metal chelate films were prepared by metal salts mixed with the polymers containing a functional group, such as poly(vinyl alcohol) (PVA), polyamide, polyacrylamide (PAAm), and polyurethane (PU). This novel method is called the retroplating‐out method. Polymer metallized films exhibited low surface resistivity around 10−1 Ω/cm2 by using this novel method. The surfaces of these films were shown to be metallized by means of X‐ray analysis. The conduction mechanism was verified reasonably well by using scanning electron microscope (SEM) and UV‐visible absorption data.
Characterization of hydroxypropylcellulose–indomethacin grafts as a function of molecular weight
Authors: Meyer Glenn A. , Lostritto Richard T. , Johnson Julian F. 
Published: April 2003

AbstractThe physical characterization of hydroxypropylcellulose–indomethacin grafts (HPC–IND) is described. Using size‐exclusion chromatography (SEC) and serial differential refractive index (dRI) and ultraviolet spectrophotometric (UV) detection methods, it was possible to characterize the chemical substitution of the HPC–IND graft. Using the acid chloride of IND as the reactive intermediate, the HPC–IND graft was synthesized. The amount of IND grafted onto the polymer as a function of the HPC molecular weight (MW) was then quantitatively estimated. It was found that the substitution of IND onto the HPC was not uniform, representing chemical heterogeneity of the first kind. Increasingly higher substitution (of IND to HPC) was observed as the MW decreased (<250,000 Daltons) for the HPC backbone. Lower, more uniform substitution was observed for the higher molecular weight regions of the HPC (>250,000 Daltons). Possible contributing factors affecting the observed nonuniform substitution include (1) the chain coiling of the HPC in solution, thus limiting the availability of the pendant hydroxyl groups, (2) nonuniform substitution of the hydroxypropyl moiety onto the cellulose backbone, and (3) steric effects resulting from the incorporation of the bulky aromatic drug molecule onto the backbone HPC.
Synthetic resin. XI. Preparation and characterization of resins derived from picoline and lutidine/aromatic hydroxy, amino, and chloro compounds/formaldehyde
Authors: Mohanty Pronab K. , Lenka Subasini 
Published: April 2003

AbstractA number of resin copolymers have been prepared by condensing α‐picoline, γ‐picoline, and lutidine separately with hydroxy acetophenone, hydroxy, amino, chloro benzoic acids, and toluic acid in the presence of sodium hydroxide and succinic acid as catalyst. The resins were characterized by infrared spectra of the characteristic groups. The solubility parameters were calculated from Small's group's contribution. The antifungal activity of the resins have also been investigated.
Diffusion and sorption of organic liquids through polymer membranes. I. Polyurethane versus n‐alkanes
Authors: Khinnavar R. S. , Aminabhavi T. M. 
Published: April 2003

AbstractSorption and diffusion studies of n‐alkanes through a commercial polyurethane membrane have been investigated in the temperature interval of 25–60°C. Liquid diffusivity through polyurethane was measured by using the immersion/weight gain method and the diffusion mechanism was explained in terms of the Fickian model. The activation energies of sorption and diffusion processes have been estimated and used to investigate the thermodynamic interactions between polyurethane chains and n‐alkanes. Furthermore, sorption data were used to estimate the molar mass between crosslinks of the network polymer.
Bead‐spring macromolecules that perturb the solvent: Scleronomic, monogenic, molecular forces
Authors: Grisafi S. 
Published: April 2003

AbstractWhen linear, conservative, molecular forces are used in this bead‐spring model of a polymer solution, a viscoplastic constitutive equation results. Using nonlinear intramolecular forces removes this viscoplasticity. The analysis shows that the anisotropy of the normal stresses is related to the anisotropy of the molecular forces. At the theta temperature the anisotropy of the intramolecular force alone determines the normal stress anisotropy. Nonlinear molecular forces are necessary for the analysis to predict a shear rate dependence for the stress in steady homogeneous flow. The symmetry of the stress tensor constrains the Hooke's law constants used to model the molecular forces. No overshoot is predicted for the stress response to a step change in shear rate when linear forces are used. Using linear forces, the stress response to a unit step shear rate shows a tendency of the polymer solution to undergo plastic deformation and to take a set.
Grafting onto wool fibers: Graft copolymerization of methyl methacrylate onto wool fibers initiated by KHSO5/Fe(III) couple
Authors: Giri Gitisudha , Samal Rajani K. 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate (MMA) onto wool fibers has been carried out in an aqueous medium under deaerated condition initiated by potassium monopersulphate (KHSO5/Fe(III) system, at varying concentration of the reactants and temperature. The effect of various salts and organic solvents on the extent of grafting has also been studied. Maximum graft percentage of 210.8% was obtained in 4 h at 40°C with the concentration of MMA (0.46 M), KHSO5 (0.0195 M), Fe(III) (1.25 × 10−4 M) in the presence of 50% formic acid. Various improved properties of the grafts have been studied and compared with the parent fiber.
Side reactions of phenylisocyanate in N,N‐dimethylacetamide
Authors: Matsui Toshimi , Kamatani Hiroyoshi , Arimatsu Yoshikazu , Kaji Atsushi , Hattori Kazuhiro , Suzuki Hajime 
Published: April 2003

AbstractSide reactions of isocyanate groups in N,N‐dimethylacetamide (DMAC) were studied. Although 4,4′‐diphenylmethane diisocyanate (MDI) in DMAC was stable and no changes occurred at 3°C, the isocyanate content decreased and a gel was finally formed at 40°C. Using phenyl isocyanate (PI) as a model compound of MDI, the identification of PI side‐reaction products in DMAC were studied. From these experiments, the following five products were identified; (1) 1,3‐diphenylurea (DPU), (2) 1,3‐diphenyl‐5‐phenylcarbamyl‐6‐dimethylaminouracil (PUR), (3) 1,3,5‐triphenylbiuret (TPB), (4) triphenyl‐s‐triazine‐2,4,6‐trione (TTT), and (5) 1,1‐dimethyl‐3‐phenylurea (DMPU). Among these identified products, the novel side reaction product PUR, which was formed between PI and DMAC as solvent, was found along with TPB and TTT, which were already known to cause three‐dimensional network formation.
Synthesis and thermal stability, dielectric, and conductivity characteristics of polymers with pendant and backbone anthracene sulfonyl groups
Authors: Majumdar Amitava , Biswas Mukul 
Published: April 2003

AbstractAnthracene‐mono‐ and disulfonyl derivatives of polystyrene and poly (N‐vinylcarbazole) have been prepared and the thermal stability, dielectric, and conductivity of these polymer pendant sulfones have been evaluated. The anthracene‐based benzene, naphthalene, anthracene, and biphenyl copolysulfones have also been prepared and characterized in regard to the above‐cited properties. Interesting variations in these properties between these two classes of polymers carrying pendant and backbone sulfonyl groups have been noted and rationalised from structural considerations.
Prefailure damage processes in highly filled glass/mica/epoxy composites
Authors: Regola M. , Baer E. , Hiltner A. 
Published: April 2003

AbstractIn the present study, the prefailure damage processes of a series of short glass fiber/mica/epoxy composites under three‐point bending were elucidated using acoustic emission (AE) coupled with in situ scanning electron microscopy (SEM) observations. This study consisted of a detailed investigation of the damage tolerance of composite systems that had constant inorganic content of 75% by weight with a varying ratio of glass fibers to mica. The flexural strength was found to increase from 11 to 21 ksi as the glass fiber content increased (mica content decreased), while the flexural modulus decreased from 5.0 to 2.5 Msi. By monitoring the AE during flexural deformation of the glass fiber‐to‐mica ratio composites, it was determined that low amplitude (0–42 db) AE events, which occurred throughout the deformation process, were caused by matrix cracking, whereas the high‐amplitude (43–100 db) AE events, which occurred just prior to failure, were caused by a fiber‐related mechanism. In situ SEM observations of the composites during flexural deformation allowed a correlation between the AE and the damage mechanisms as a function of strain. In the all‐mica composite, microcracking initiated in the linear region at preexisting flaws, on the order of 10 μm, located at the mica interface. These microcracks grew along the mica contours over the majority of the deformation process, emitting low‐amplitude events, until final fracture occurred at relatively low strains. In the glass fiber‐containing composites, microcracking initiated in the linear region at preexisting flaws and voids, on the order of 10 μm. These microcracks grew slowly, emitting low‐amplitude events, as the strain increased, but were prevented from causing failure at low strains because of the toughening effect of the glass fibers. At sufficiently high strains, however, fiber breakage and fiber pull‐out occurred that corresponded to the high‐amplitude events detected by the AE. At strains just prior to failure, catastrophic crack growth occurred, producing a rapid increase in both low‐and high‐amplitude events, causing ultimate failure.
Impregnation of white pine wood with unsaturated polyesters to produce wood–plastic combinations
Authors: Doss N. L. , Elawady M. M. , Elawady N. I. , Mansour S. H. 
Published: April 2003

AbstractTwo unsaturated polyester resins based on poly(1,2 propylene–maleate–phthalate) (PE1), and poly(oxy–diethylene–maleate–phthalate) (PE2) were used for the impregnation of oven‐dried white pine wood samples in admixture with styrene (S). Curing was affected by the initiator‐heat technique by either using 0.1–0.2% by weight of benzoyl peroxide (Bz2O2), or 1% by weight of methyl ethyl ketone peroxide (MEK). It was found that the use of PE1/S mixture resulted in the formation of wood–plastic combinations (wpc) with higher percent retention and higher percent polymer loadings than those obtained by the impregnation of wood samples with PE2/S imxtures. The use of different swelling solvents including ethanol, acetone or chloroform, did not influence the percent retention or polymer loadings of wpc for either PE1/S or PE2/S mixtures. Physical tests performed on wpc showed that compression, hardness, static bending were generally enhanced, water absorption was decreased, and dimensional change was retarded to different extents for both polyesters used, but no permanent stabilization was attained.
Analysis of thermal degradation for plastic optical fibers
Authors: Takezawa Yoshitaka , Tanno Seikichi , Taketani Noriaki , Ohara Shuichi , Asano Hideki 
Published: April 2003

AbstractAttenuation loss of plastic optical fibers (POFs) gradually increases with long use at high temperatures. We separated attenuation loss of the POFs before and after heating at 150°C in air into four loss factors, and identified the main factor for attenuation loss increase as electronic transition absorption loss (αe). The increase of αe was caused by a thermal oxidation reaction of the core polymer in the POF. But, according to NMR and FT‐IR spectra, elementary analysis, etc., hardly any reaction products were detected. We assume that the reaction products were only a small amount of the conjugated carbonyl groups. So we fabricated POFs containing model compounds with conjugated carbonyl groups, and measured their attenuation loss. The attenuation loss spectra of these POFs were similar to those of thermally degraded POFs. Consequently, a very small amount of conjugated carbonyl groups were formed by the thermal oxidation reaction of core polymer so that αe increased to an unacceptable level.
Swelling effect of semicrystalline poly(vinyl alcohol) in hydrogen peroxide
Authors: Lee Ping I. 
Published: April 2003

AbstractThe effect of hydrogen peroxide on the physicochemical properties of semicrystalline poly(vinyl alcohol) (PVA) has been investigated. Significant and irreversible increases in equilibrium water swelling, dissolved oxygen permeability, and surface wettability have been observed in PVA samples treated with concentrated hydrogen peroxide. Based on the small amount of carbonyl content detected and the crystallinity reduction in hydrogen‐peroxide‐treated poly(vinyl alcohol) samples, a mechanism involving a combination of hydrogen‐peroxide‐induced oxidative chain scission and dissolution of crystalline regions in poly(vinyl alcohol) is proposed for the observed swelling kinetics and associated changes in polymer properties.
Synthesis of telechelic dithiol oligomers containing sulfur atoms‐moisture barrier properties
Authors: Pujol J. M. , Brossas J. , Catala J. M. 
Published: April 2003

AbstractThe aim of this work was to synthesize new polysulfide materials from butadiene, styrene, isoprene, and methacrylate monomers and to study their moisture vapor permeability. For this purpose, a series of telechelic dithiol polysulfide oligomers were prepared by a polycondensation reaction between dianionic species of the corresponding monomer and sulfur or by reduction of the resulting cyclic polysulfide polymers. This last process was followed by 1H‐NMR and elemental analysis. It was established that the scission of the polysulfide linkages to thiol end groups was fastest with the greatest number of sequential sulfur atoms. The thiol reactivity was used to prepare cured materials from the liquid oligomers and manganese dioxide: Networks were obtained from butadiene dithiol oligomers, whereas chain extension occurred for the others. Infrared analysis suggests that the reticulation reaction results from thiol addition to the double bond. The moisture vapor transmission test applied to these different materials showed that these new compounds present good moisture barrier properties.
Study on the crystallization kinetics of PP/GF composites
Authors: Tai Horng‐Jer , Chiu Wen‐Yen , Chen Leo‐Wang , Chu Line‐Hwa 
Published: April 2003

AbstractThe crystallization kinetics and morphology of glass fiber‐reinforced polypropylene (PP/GF) were investigated in this work. Both isothermal and nonisothermal crystallization behaviors of 90PP/10GF, 80PP/20GF, and 70PP/30GF were examined with a DSC instrument. It was found that the addition of glass fiber would increase the crystallization rate of PP and increase the content of β spherulite, which was most likely formed at temperatures between 390 and 400 K. The morphology of spherulites of PP/GF composites were examined with SEM and a polarized microscope. All experimental observations conformed rather well with the theoretical approach, a dynamic crystallization model, proposed in our previous work. The size of α spherulites of PP would decrease at lower crystallization temperature, or at higher cooling rate, or by adding glass fiber in it.
Optimal periodic control of a continuous “living” anionic polymerization. III. Presence of impurities in the monomer feed
Authors: Vega J. R. , Frontini G. L. , Meira G. R. 
Published: April 2003

AbstractPrevious publications have demonstrated that when “living” anionic polymerizations are carried out in continuous reactors under forced periodic operation of the feed flows then: (a) In the absence of impurities and within certain limitations, it is possible to produce polymers with any prespecified values of the number‐average chain length, the polydispersity and the polymer production; and (b) even small concentrations of impurities in the monomer feed, drastically inhibit such a possibility. In this work, the optimal periodic control problem has been reformulated, including the presence of impurities. In all cases, the flexibility of the control is reduced with respect to the impurities‐free case.
Plastic optical fibers with fluoroalkyl methacrylate copolymer as their core
Authors: Takezawa Yoshitaka , Tanno Seikichi , Taketani Noriaki , Ohara Shuichi , Asano Hideki 
Published: April 2003

AbstractNovel plastic optical fibers having a core made of a crosslinking copolymer containing mainly fluoroalkyl methacrylate (FMA–POFs) were fabricated and their optical properties were analyzed. In the visible wavelength region, attenuation losses of as‐manufactured FMA–POFs were low and their loss spectra were similar to that of the plastic optical fiber whose core was made of methyl methacrylate copolymer (MMA–POF). But after heating at 160°C in air, increases in attenuation losses of FMA–POFs were about 10 times smaller than that of the MMA–POF. FMA–POFs had an optical window at 780 nm. There was hardly any change in loss at 780 nm compared with the loss increase at 660 nm. This indicated that FMA–POFs would be applicable to optical communications at 780 nm in the near‐IR region.