bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural changes in rubber during milling
Authors: Kumar N. R. , Roy S. , Gupta B. R. , Bhowmick A. K. 
Published: April 2003

AbstractProcessing operations such as milling, change the chemical structure of rubber. Infrared (IR) spectroscopy and electron spectroscopy for chemical analysis (ESCA) have been used to detect the formation of functional groups during the milling of natural rubber (NR), epoxidised natural rubber (ENR), styrene butadiene rubber (SBR), neoprene (CR), and acrylic rubber (AR). The concentration of carbonyl () groups as detected by IR spectroscopy increases with the time of milling for all the rubbers. The concentration of hydroxyl groups (OH) in NR and ENR also increases during milling. ESCA spectra of the rubbers before and after milling reveal that the peaks are broader for milled rubber, and that the concentration of oxygen is also greater. In the case of ENR, however, the concentration of epoxide rings decreases and that of furan rings increases with the time of milling.
Studies on the adhesion of polyimide coatings on copper foil
Authors: Chen K.‐M. , Ho S.‐M. , Wang T.‐H. , King J.‐S. , Chang W.‐C. , Cheng R. P. , Hung A. 
Published: April 2003

AbstractThe peel strength and the color of the copper foil peeled at 90 degrees from five different polyimide films were studied. The interfacial surfaces of copper foil and polyimide were examined by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and energy dispersion analysis by X‐ray (EDAX). There is a correlation between peel strength, and the color of the interfacial side copper caused by oxygen diffusion. Study of the imidization process carried out in vacuum indicates that the geometric arrangements of the atoms of polyimide also play a very important role in peel strength.
Copolymer composition control by means of semicontinuous emulsion copolymerization
Authors: van Doremaele G. H. J. , Schoonbrood H. A. S. , Kurja J. , German A. L. 
Published: April 2003

AbstractThe effect of two different monomer addition strategies on the chemical composition distribution of the copolymer formed by the (seeded) semicontinuous emulsion copolymerization of styrene and methyl acrylate has been investigated. 1. The addition of a mixture of the monomers at a constant feed rate results in a homogeneous copolymer, provided that extremely long process times are used (starved conditions). When not starting from a seed latex, aqueous phase polymerization was observed at low feeding rates. When using a seed latex, aqueous phase polymerization appeared to be negligible. 2. In order to achieve an optimal monomer addition pattern, a pragmatic approach is presented. An optimal monomer addition profile was calculated from accurate monomer partitioning data using a short iteration procedure. Gradient high performance liquid chromatography (HPLC) was successfully applied as a rigorous test of the homogeneity of the copolymer formed. The information obtained contains much more detail than in the case of using differential scanning calorimetry of 1H NMR. In contrast to 1H NMR that provides only average cumulative chemical compositions, the complete chemical composition distribution can be obtained by means of HPLC.
Dynamic analysis of flat‐spring supported polymers
Authors: Ding Jianfu , Xue Gi , Cheng Rongshi 
Published: April 2003

AbstractA flat‐spring supported sample technique has been developed for studying the dynamic mechanical properties of a polymer in all its mechanical states, especially for materials with insufficient tensile strength for tensile mode test. The results obtained by this new technique show good agreement with the data from tensile mode tests for poly(ethylene terephthalate) and polystyrene. A high crystallization rate in temperature region 110–160°C for a quenched poly(ethylene terephthalate) and a secondary relaxation at the temperature of 100°C above Tg for a monodispersed polystyrene with a molecular weight of 3 × 105 could be measured quantitatively by the flat‐spring supported polymer technique. This is an important improvement over the existing supported sample techniques.
Preparation and electrodeposition properties of trimethylolpropane–toluene diisocyanate–dimethylaminoethanol/2‐ethylhexanol resins
Authors: Yang Chin‐Ping , Chen Yahn‐Haur 
Published: April 2003

Abstract2,4‐Toluene diisocyanate (TDI) was partially blocked with equimolar mixtures of dimethylaminoethanol (DMAE) and 2‐ethylhexanol (2EH) of different ratios to form the DMAE/2EH half‐blocked TDIs, which were subsequently reacted with 1/3 mol trimethylolpropane (TMP) to yield the trimethylolpropane–toluene diisocyanate–dimethylaminoethanol/2‐ethylhexanol (TMP–TDI–DMAE/2EH) resins having various content of tertiary amine groups. These resins were neutralized with acetic acid and then dispersed in deionized water, resulting in the milky emulsions used for cationic electrodeposition. Some electrodeposition properties, such as deposition yield, conductivity, rupture voltage, and throwing power, of the resins were investigated. In addition, one of the obtained resins (added as a crosslinker) and an amine–epoxy adduct were codispersed in deionized water, and the nature of electrodeposition of the two‐component emulsion is discussed.
Effect of coupling agent and absorbed moisture on the tensile properties of a thermoplastic RRIM composite
Authors: Otaigbe J. U. 
Published: April 2003

AbstractThe effect of introduction of a silane coupling agent and absorbed moisture (i.e., equilibrium hygroscopic state) on the tensile properties of a thermoplastic reinforced reaction injection molding (RRIM) composite, having a fiber volume fraction of 0.33, was evaluated. The composite was produced by anionically polymerizing caprolactam monomer within a continuous strand (swirl) glass fiber mat using a RRIM method. In addition to the expected strong dependence of the composite tensile stiffness and strength on introduction of 1.5 wt % (based on the total weight of glass fibers) of γ‐amino propyl triethoxy silane coupling agent, the effect of the mode of application of the coupling agent on the resultant composite properties, under tensile loading, was observed to be insignificant in the dry state but quite important in the wet state. Microscopic examination of the fracture surfaces revealed a three‐stage tensile failure mechanism that is associated with debonding at low strains of the fibers, fiber failure (at the weakest point), and pull‐out of the fibers resulting in catastrophic failure, at the ultimate tensile strain, of the composite.
Gas solubility and diffusion in a polystyrene–polybutadiene block copolymer
Authors: Rein D. H. , Baddour R. F. , Cohen R. E. 
Published: April 2003

AbstractOver the temperature range of 20 to 90°C, the equilibrium solubility of methane or argon in a star‐branched polystyrene–polybutadiene (SB) block copolymer can be reliably estimated from a volume‐fraction‐weighted average of the homopolymer solubilities; the value of heat of solution for SB block copolymer lies between the two values associated with the constituent homopolymers. Diffusion coefficients for gases in the block copolymer are bracketed by the homopolymer values over the range of temperature employed, but the activation energies for diffusion in SB are higher than either of the homopolymer values. The anomalous temperature dependence and the inability of a computer simulation to reproduce experimental diffusion coefficients supported the concept of a temperature‐dependent restriction on chain mobility in the polybutadiene regions of the block copolymer. This β factor embodies the relative reduction in the rate of gas diffusion through the B regions of the copolymer compared to B homopolymer; β has a value of about 2–3 at room temperature but decreases to unity when the polystyrene chains become mobile at the polystyrene Tg.
Effect of melt annealing on the morphology and properties of polycarbonate blends
Authors: Cheng T. W. , Keskkula H. , Paul D. R. 
Published: April 2003

AbstractThe effect of quiescent annealing for brief periods at melt‐processing temperatures (e.g., 270°C) were designed to simulate certain conditions that can occur during molding or extrusion. It was found that significant changes in the phase morphology of polycarbonate‐based blends can occur in less than 2 min under these conditions. Such morphological rearrangements are detrimental to the mechanical properties of multiphase blends of polycarbonate with rigid polymers, viz., polystyrene, poly(methyl methacrylate), and styrene/acrylonitrile copolymers and core‐shell impact modifiers.
Synthesis and characterization of formal‐group‐containing diisocyanates and polyimides therefrom
Authors: Avadhani C. V. , Wadgaonkar P. P. , Vernekar S. P. 
Published: April 2003

AbstractFour new formal‐group‐containing diisocyanates, namely, bis(3‐isocyanatophenoxy) methane, bis(4‐isocyanatophenoxy)methane, bis[2‐(3‐isocyanatophenoxy)ethyl] formal, and bis[2‐(4‐isocyanatophenoxy)ethyl] formal, were synthesized by the Curtius rearrangement from the corresponding dicarboxylic acids. The diisocyanates were polycondensed with pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylic dianhydride (BTDA) in dimethylacetamide (DMAc) to obtain formal‐group‐containing polyimides. These polyimides were characterized by viscosity measurements, IR spectroscopy, X‐ray diffraction, and thermogravimetric analysis.
Ultraviolet‐radiation‐induced graft copolymerization of styrene and acrylonitrile onto cotton cellulose
Authors: Shukla S. R. , Gopala Rao G. V. , Athalye A. R. 
Published: April 2003

AbstractPhotoinitiated graft copolymerization of the vinyl monomers, styrene and acrylonitrile, onto cotton cellulose was studied using uranyl nitrate and ceric ammonium nitrate as photoinitiators. Uranyl nitrate photoinitiation showed a higher level of grafting for styrene, whereas in the case of acrylonitrile ceric ammonium nitrate was found to be the better photoinitiator. Optimized conditions of grafting, when employed to cotton swollen with sodium hydroxide and zinc chloride, enhanced the graft levels for both monomers. Grafted samples were subjected to thermal analysis, as well as estimation of moisture regain and tenacity. Thermal stability increased, whereas, the moisture regain and tenacity decreased, with the increase in graft add‐on in the case of both monomers. Acrylonitrile‐grafted cotton showed dyeability with cationic dye that improved with the level of graft add‐on. Possible explanations have been given.
The effects of functional azo initiator on PMMA and polyurethane IPN systems. I. Synthesis, characterization, and thermal effects
Authors: Roha M. , Wang B. 
Published: April 2003

AbstractThe use of functional azo initiators and the thermal history of the materials have been shown to exert significant effects on the properties of interpenetrating polymer networks (IPNs). The IPNs prepared with a reactive azo initiator from MDI and 1,2‐PBD (1,2‐polybutadiene diol) with PMMA have been found to exhibit greater ductility, lower rigidity, and lower moduli than IPNs prepared with AIBN. This probably resulted from the attached PMMA blocks modifying the properties of the PU matrix phases. Increasing thermal treatment of IPNs prepared from either the reactive or the normal azo initiators exhibited increased Tg values in both DSC and DMTA scans. These results have been explained by increased association from chemical reactions between the hard segments of the polyurethane and poly(methyl methacrylate) ester groups.
Methods for preparation of absorbent microspherical tannin resin
Authors: Yamaguchi Haruhiko , Higuchi Mitsuo , Sakata Isao 
Published: April 2003

AbstractTannin beads formed by reaction of Mimosa tannin (condensed‐type tannin) with formaldehyde in nonpolar polybutenous medium were microspherical resins. Resins prepared with 37.5% tannin concentration were porous spherical resins with 139.22 m2/g of surface area (adsorption method of iodine in n‐hexane, 2.1 m2/g for the dried beads by the Braunauer‐Emett‐Teller (BET) method) and were strong enough to withstand use on a column. The spherical resin adsorbed 3.7 mmol of Cr6+ ions per one gram dry weight of resin (by batch method), this adsorption being comparable to commercial adsorbent.
Biodegradable natural composites. I. Processing and properties
Authors: Gatenholm P. , Kubát J. , Mathiasson A. 
Published: April 2003

AbstractThis paper presents an investigation of the properties of composites of bacteria‐produced polyesters reinforced with wood cellulose. Although cellulose fibers improved the strength and stiffness of the polyhydroxybutyrate (PHB), the samples were very brittle. The impact strength and elongation at break of these composites were significantly improved when PHB copolymers with increased amounts of hydroxyvalerate (HV) were used as the matrix. Dynamic mechanical properties of PHB copolymers of varying compositions and of cellulose‐filled composites were investigated. The introduction of cellulose resulted in a decreased loss factor owing to restrictions of the chain mobility in the amorphous phase. An improvement was observed in the dynamic modulus, which was seen to be greatest at elevated temperatures. An excellent dispersibility of cellulose fibers was achieved in the PHB matrix as compared with such synthetic matrices as polystyrene or polypropylene. The degree of dispersibility was strongly affected by processing conditions. The defibrillation observed on extracted fibers suggests a possible hydrolysis of cellulose by crotonic acid formed in situ as a result of the thermal decomposition of the PHB matrix.
Reinforcement of natural rubber with nylon 6 short fibers
Authors: Younan A. F. , Ismail M. N. , Yehia A. A. 
Published: April 2003

AbstractThe properties of natural rubber vulcanizates reinforced with nylon 6 short fibers were studied. It was found that the stress of vulcanizates decreased with initial fiber loading, followed by an increase with increasing the amount of fiber. The effect of reinforcing carbon black HAF on the physicomechanical properties was studied in the presence and absence of hydrated silica.
Thermodynamic interactions of solvents with styrene–butadiene–styrene triblock copolymers
Authors: Romdhane I. Hadj , Plana A. , Hwang S. , Danner R. P. 
Published: April 2003

AbstractFundamental thermodynamic interaction data for various solvents with two styrene–butadiene–styrene triblock copolymers (Kraton D‐1101 and Kraton D‐1300X) have been collected by the use of inverse gas chromatography at infinite dilution. Experimental results are presented for nine D‐1101/solvent systems and nine D‐1300X/solvent systems at 308, 328. and 348 K. Weight‐fraction activity coefficients and Flory–Huggins χ interaction parameters have been calculated from the retention volumes. The χ parameter is used as a measure of the strength of interaction and therefore as a guide in the prediction of polymer–solvent compatibility. In addition, partial molar heats of mixing, ΔHm∞, and heats of solution, ΔHs, were determined. The Hildebrand–Scatchard solubility theory was combined with the Flory theory in order to estimate the solubility parameter of the thermoplastic rubbers at the three different temperatures.
Swelling equations for confined homogeneous and heterogeneous polymeric networks: Calculation of M̄c in swellable two‐phase systems
Authors: Harland Ronald S. , Peppas Nikolaos A. 
Published: April 2003

AbstractSwelling equations were derived for polymeric networks that consist of two swellable but distinct phases. These equations can be used to describe the equilibrium swelling behavior of certain two‐phase network systems. Using physicochemical measurements of the equilibrium polymer volume fraction, it was possible to calculate the number‐average molecular weight between crosslinks, M̄c, using these equations. The influence of several structural parameters on M̄c was investigated. © 1992 John Wiley & Sons, Inc.
Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. I. Kinetics in VDC–BMA emulsion polymerization and surface and colloidal properties of VDC–BMA latexes
Authors: Lee K. C. , El‐Aasser M. S. , Vanderhoff John W. 
Published: April 2003

AbstractVinylidene chloride (VDC)—butyl methacrylate (BMA) comonomer mixtures with various composition (83 : 17, 60 : 40, 33 : 67 in mol %) were polymerized at 25°C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization. The reactivity ratios determined in VDC (M1)—BMA (M2) emulsion copolymerization system were r1 = 0.22 and r2 = 2.41. Seven 35% solids (83 : 17 mol %) VDC–BMA copolymer latexes were prepared: one batch (G), one seeded batch (F), and 5 seeded semicontinuous polymerizations of 5 different monomer feed rates ranging from 0.27 (A) to 1.10 wt %/min (E). The kinetic studies of seeded semicontinuous polymerizations A‐E showed that the rates of polymerizations (Rp) were controlled by the monomer addition rates (Ra). The conversion versus time curves for the polymerizations of 0 : 100–100 : 0 VDC–BMA mixtures by batch polymerization showed that the rate of polymerization (Rp) was a function of the number of particles, and that the rate of polymerization in a latex particle (Rpp) increased with increasing proportions of butyl methacrylate in the monomer mixture. All of the latexes had narrow particle size distributions. The greater particle number density in VDC polymerization and the greater water solubility of VDC suggest that the homogeneous nucleation mechanism is operative in VDC–BMA copolymerizations. The latex copolymers prepared by semicontinuous polymerization had lower number‐and weight‐average molecular weights than those of the corresponding batch copolymers, resulting from the monomer starvation occurring during the semicontinuous polymerization. The surface characterization study of the cleaned latexes showed that for the latexes by batch process, the surface charge density derived from strong‐acid groups decreased with increasing proportion of VDC in the monomer mixture. On the other hand, for the latexes prepared by semicontinuous polymerization, the surface charge density derived from strong‐acid groups did not depend on the monomer composition of the copolymers.
Elimination of stress whitening in high‐molecular‐weight polyethylene
Authors: Lee Y. W. , Kung S. H. 
Published: April 2003

AbstractHigh‐molecular‐weight polyethylene (HMWPE) sheets have been cold rolled biaxially to different reductions in thickness. After 40% or more reduction in thickness by cold rolling, the stress‐whitening phenomenon in HMWPE was eliminated. To find out the reason of elimination of stress whitening by cold rolling, different techniques were employed. The measurement of hardness, density, and strain distribution of the specimens were carried out for the study of the differences in mechanical and physical properties of the stress whitened and nonwhitened specimens. Recovery of density, hardness, and dimensions of the specimens due to heating were also studied. Differential scanning calorimetry (DSC) and polarized‐light microscopy were used to study the melting, and recrystallization behavior and scanning electron microscopy (SEM) were used to study the surface texture of the specimens. Based on the results of the different techniques employed, it is concluded that after cold rolling, especially biaxially rolled, due to the combined forces of compression and shear acting on the specimens from different directions, the macro‐and micro‐imperfections of the material may be eliminated to some extent. At 40% or more rolling reduction, the imperfections were largely eliminated; hence stress whitening did not occur.
Melt‐rheological properties of PP/EVA blend
Authors: Gupta A. K. , Ratnam B. K. , Srinivasan K. R. 
Published: April 2003

AbstractThis paper describes a study of melt‐rheological properties of the binary blend of isotactic polypropylene (PP) and ethylene–vinyl acetate copolymer (EVA) at varying blending ratios (from 0 to 40 wt % EVA content) and using three samples of EVA containing different vinyl acetate contents (VA %), viz. 9, 12, and 19%. Measurements made on a capillary rheometer at three different temperatures (210, 220, and 230°C) in a shear stress range of 104–106 Pa (shear rate 101–104 s−1) are presented and discussed for the effects of blend composition and shear stress on the flow curves, melt viscosity and melt elasticity. Morphology of the blend studied through scanning electron microscopy revealed distinct differences in size and number density of dispersed EVA droplets, which are discussed in terms of the variation of average size and number density of the dispersed EVA droplets as a function of blend composition and shear stress. Melt‐rheological properties and morphology of dispersion are correlated and found quite consistent.
Formation and structural characteristics of porous ethylene glycol dimethacrylate networks
Authors: Okay Oğuz , Gürün Çiğdem 
Published: April 2003

AbstractThe relationships between the synthesis conditions and the morphology of ethylene glycol dimethacrylate (EGDM) networks were investigated. EGDM networks were prepared by free‐radical polymerization in toluene as a diluent. The networks were characterized by swelling, porosity, and pendant vinyl group content measurements. The accessibility of pendant vinyls to low molecular weight compounds was tested using pyrrolidine as a model reactant. The results show that the polymerization of EGDM in toluene is accompanied by a phase separation in the system. The networks thus obtained are heterogeneous and exhibit an inhomogeneity in the porosity and swelling distributions. Both the weight swelling ratio and the pore volume of the networks increase with increasing monomer dilution. It was also found that the accessibility of pendant vinyls increases as the cross‐linking density of the network decreases or as its porosity increases. The results can be explained with the formation of highly cross‐linked microgels as the intermediates in the network formation processes. Two equations were derived to predict the equilibrium weight swelling ratio and the pore volume of heterogeneous networks. Satisfactory agreement of the results of measurements with the predictions of the equations was observed.
Crystallization of polymer melts under fast cooling. II. High‐purity iPP
Authors: Piccarolo S. , Saiu M. , Brucato V. , Titomanlio G. 
Published: April 2003

AbstractSamples of a high‐purity isotactic polypropylene (iPP) were quenched from the melt so as to monitor cooling history. A continuous variation of morphology and crystal structure was obtained with cooling rate. This is discussed in relation to sample thermal history evidencing that cooling history relevant to quenched samples is in the neighborhood of 90°C. In particular the samples are essentially mesomorphic when at this temperature cooling rates larger than 80°C/s were adopted, while below a few tens of °C/s only α‐monocline form is obtained. Densities of quenched samples were compared with predictions of an isokinetic extrapolation of Avrami model of polymer crystallization kinetics.