bluuebunny/crossref_metadata_2025_split huggingface dataset:
Processable aromatic polyimides
Authors: Burks Harold D. , St. Clair Terry L. 
Published: April 2003

AbstractTwo 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

AbstractA 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

AbstractThe 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

AbstractSteel–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

AbstractThe 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

AbstractThe 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

AbstractHydrolysis 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

AbstractA 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.
Control of free‐radical emulsion polymerization of methyl methacrylate by oxygen injection. I. Modeling study
Authors: Louie Brian M. , Chiu Wen Yen , Soong David S. 
Published: April 2003

AbstractOxygen injection has been proposed as an effective control measure for limiting the rate of heat release and altering the rate of polymerization in emulsion processes. A detailed mathematical model is developed to describe the system behavior with and without oxygen injection. Because of the rapid penetration of dissolved oxygen into the polymer particles, growing radical chains are terminated prematurely, lowering product molecular weights. Moderate oxygen flows and moderate set point temperatures are found to give the optimal response without significant lowering of the final molecular weight.
Molecular weight distribution control in a semibatch “living” anionic polymerization. I. Theoretical study
Authors: Couso D. A. , Alassia L. M. , Meira G. R. 
Published: April 2003

AbstractA method to produce homopolymers of preestablished molecular weight distribution (MWD), through “living” anionic polymerizations carried out in homogeneous semibatch reactors is proposed and theoretically justified. In the direct form of the technique, very fast reactions are assumed, and the monomer and “killing” agent feed flows are obtained from the knowledge of the desired MWD, the system spreading function, the total reaction time, the initial reaction volume, and the reagent concentrations. Alternatively, by controlling a reactor outlet flow instead of the “killing” agent feed, an external deactivation of the “living” ends can be implemented. The method can be extended to slow reactions, to more elaborated mechanisms, and to take into account the unwanted deactivation of “living” ends by impurities in the monomer solution feed.
Foam extrusion characteristics of thermoplastic resin with fluorocarbon blowing agent. III. Foam sheet extrusion of polystyrene and low‐density polyethylene
Authors: Yang Heng‐Huey , Han Chang Dae 
Published: April 2003

AbstractAn experimental study was conducted on the extrusion of polystyrene and low‐density polyethylene foam sheets, using fluorocarbon blowing agents and a tubular die. The effects of the type and concentration of blowing agent, die temperature, and takeoff speed on foam extrusion characteristics were investigated. They are foam density, tensile modulus, and cell morphology. It has been found that die temperature greatly influences the open cell fraction and foam density and that the takeoff speed greatly influences cell orientation, which, in turn, has a profound influence on the tensile modulus of the foam sheets produced.
Equilibrium disperse dye sorption by drawn polypropylene films
Authors: Yonetake Koichiro , Nagamatsuya Kotoku , Masuko Toru 
Published: April 2003

AbstractIsotactic polypropylene (PP) films drawn at various temperatures ranging from 100 to 155°C have been dyed at 80°C with p‐aminoazobenzene (PAAB) or C.I. Disperse Yellow 7 (Y‐7). The equilibrium dye sorption (M0) of PAAB obtained for these films decreased with an increase in draw ratio (λ) of the films. The M0 values of Y‐7, however, increased with increasing in λ similarly the crystallinities of these films increased slightly with draw ratios. By use of fine structural data of these films, the change in M0 of Y‐7 for drawn PP films were analyzed in terms of a mosaic‐block structural model. The increase in M0 with increasing in λ was thus ascribed to enhanced sorption by the amorphous side region between crystalline cores located parallelly in the direction to the molecular axis. The side regions of the drawn systems become rich in interfibrillar tie chains in a higher range of λ. The side region seem to have a strong affinity particularly to a long rodlike dye molecule such as Y‐7; this feature is probably associated with the amount of the amorphous chains having extended chain conformation, the fraction of which increases during drawing.
Copolymers of ethylene with butene‐1 and long chain α‐olefins. I. Decene‐1 as long chain α‐olefin
Authors: Seppälä Jukka Veli 
Published: April 2003

AbstractThe possibility was studied of using decene‐1 as comonomer with ethylene in a slurry type polymerization with Ziegler–Natta catalysts. Under the reaction conditions used decene contents remained at the 2 wt% level in ethylene/decene‐1 copolymers. When additionally butene‐1 was present in the polymerization, decene‐1 contents were significantly higher. A synergistic effect was identified in the reactivities of butene‐1 and decene‐1 in terpolymerization with ethylene. The comonomer reactions were determined and comonomer contents measured by 13C‐NMR spectroscopy. Decene‐1 content had an effect on the polymer density and crystallinity, but virtually no effect on melting temperature. With high comonomer contents an additional melting range was identified in DSC curves at about 100°C.
Physical properties of barium titanate‐filled rubber‐modified epoxies
Authors: Tse Mun‐Fu 
Published: April 2003

AbstractRubber‐modified epoxies (RME) filled with different levels of barium titanate (BaTiO3) have been characterized by using DSC, TGA, and TMA. The presence of the filler does not affect the glass transition temperature or the activation energy of pyrolysis; however, it does change other thermal properties. The dielectric constant increases markedly, but the dissipation factor remains fairly constant with increasing BaTiO3 loading. The polymers, in MEK, exhibit slightly different degrees of swelling and their sol fractions vary. Mechanical properties, such as stress‐strain relation, friction, abrasion, scratch hardness, and scrape adhesion of the polymers, will be described.
Optimization of batch polymerization processes—narrowing the MWD. I. Model simulation
Authors: Louie Brian M. , Soong David S. 
Published: April 2003

AbstractSeveral control strategies for the free‐radical polymerization of methyl methacrylate are analyzed with a detailed constitutive model incorporating the gel and glass effects. Optimal temperature history, photoinitiation intensity variation, and programmed monomer and solvent additions, employed alone and in combination, represent cases simulated by this model. Solvent addition is selected for further experimental studies, due to some attractive features. The product molecular weight distribution is narrowed, while the molecular weight averages are maintained high. Model predictions of the solvent injection history exhibit a strong sensitivity to the constitutive equations for describing the gel and glass effects.
Synthesis of a novel polyesterimide
Authors: Dolui Swapan Kumar , Pal Dhananjay , Maiti Sukumar 
Published: April 2003

AbstractA new polyesterimide has been synthesized from trimellitic acid anhydride, diaminodiphenylsulfone, and bisphenol‐A following three different routes. Solubility behavior in different solvents, solution viscosity, density, crystallinity, and thermal and electrical properties of the polyesterimide have been discussed. Results indicate that the polyesterimide thus prepared has medium thermal stability.
Fracture behavior of short fiber reinforced thermoplastics I. Crack propagation mode and fracture toughness
Authors: Jang B. Z. , Lieu Y. K. 
Published: April 2003

AbstractThe fracture behavior of several short glass fiber reinforced thermoplastics has been studied. The fracture toughness of these materials may be related to local crack propagation mode, which is found to be highly rate dependent. At low test rates the crack growth in the reinforced polymers tend to follow a fiber avoidance mode, creating a greater area of new surfaces, which in conjunction with greater degree of interfacial debonding and fiber pullout friction leads to a higher fracture resistance. An increase in loading rate in general results in a more straight and flat crack path, as well as a lesser extent of fiber debonding and pullout. Therefore the fracture toughness is reduced although the frequency of fiber breakage is increased. The fracture behavior of these short fiber reinforced polymers appears to be dictated by the matrix properties when the loading rate is high.
The turbulent drag reduction by graft copolymers of guargum and polyacrylamide
Authors: Deshmukh S. R. , Chaturvedi P. N. , Singh R. P. 
Published: April 2003

AbstractCommercial guargum is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum start degrading within 8 hrs. of their preparation and after 65 hrs., they degrade completely. In the present investigation, the graft copolymers of guargum and polyacrylamide have been prepared. It has been shown that the purification and grafting enhance the drag reduction effectiveness and biodegradation resistance considerably in guargum.
Dynamic mechanical properties and adhesive strengths of epoxy resins modified with liquid rubber. I. Modification with ATBN
Authors: Takemura Akio , Tomita Bun‐Ichiro , Mizumachi Hiroshi 
Published: April 2003

AbstractThe dynamic mechanical properties and the adhesive strengths of Epikote 828 and Epikote 828‐ATBN blend systems were investigated. The ATBN blend systems were proved to be completely incompatible with the dynamic mechanical measurement and also fitted well with Takayanagi's model which was designed for completely incompatible two‐phase systems. The epoxy resin had a nonreacted part when cured at room temperature. The blending of ATBN reduced the nonreacted part of the epoxy resin, and made contributions to the adhesive strengths. In the case of tensile test of crosslap specimens using aluminium as adherends, the adhesive strengths of ATBN blend systems were almost 1.5‐fold of those of epoxy resin without blending of ATBN. As for wood adherends, the maximum of the adhesive strengths was found at 60°C for epoxy resin without blending of ATBN, and at 0°C for ATBN blend systems. The facts meant that there were mutual interactions between the adhesive strengths and the viscoelastic behavior of the adhesive polymers in the two‐phase systems as observed in completely miscible polymer blends. There was not pronounced distinction between epoxy resins without blending of ATBN and ATBN blend system, as to the shear adhesive strengths.
Effect of plasma treatment on the structure and allied textile properties of mulberry silk
Authors: Nadiger G. S. , Bhat N. V. 
Published: April 2003

AbstractStudies on the effect of nitrogen plasma on morphology and textile properties of mulberry silk fibers and fabrics have been conducted. The changes in the morphological structure have been monitored by transmission electron microscopy, X‐ray diffraction, and internal reflection infrared spectroscopy. The changes in some of textile properties such as wettability, drying rate, and crease recovery owing to plasma treatment have also been investigated. It has been found that the surface of mulberry silk gets etched away, even affecting the crystalline region. This behavior is opposite to our findings on tassar silk. Therefore, an explanation of this differential behavior of mulberry with tasar on the basis of amino acid linkages vis‐à‐vis bonding, wettability, drying rate, and water retention capacity has been attempted. These results have been used to arrive at an understanding of internal structure of mulberry.
Phase behavior of polycarbonate blends with selected halogenated polymers
Authors: Woo E. M. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractBisphenol A polycarbonate is shown to be miscible with a vinylidene chloride based polymer containing 13.5% by weight of vinyl chloride. On the other hand, polycarbonate is found to be immiscible with poly(vinyl chloride), poly(vinylidene fluoride), and polyepichlorohydrin.
Dynamic mechanical properties of some nylons and their blends
Authors: Ong Eng Seong , Kim Yunghoon , Williams H. Leverne 
Published: April 2003

AbstractThe dynamic mechanical properties of nylons 6, 11, 12, 66, 610, 612, and 666 are compared. The spectra are very similar with peaks in the loss curves at about −120, −40, and 85°C. The similarity suggests that attempts to determine whether the nylons could in fact be incompatible when blended might not be successful. Calculations based in turn on calculated cohesive energy densities and interaction parameters also suggest that only nylon, 6 and 66 would be compatible. By using the nature of the major loss peak at the glassy transition which is high and narrow for nylons 11 and 12 and broader and shorter for nylons 6, 66, and 666, it is possible to deduce that nylons 6 and 12 are somewhat incompatible but that the other combinations are most likely dynamically compatible.
Dynamic mechanical and impact properties of PP/SEBS blend
Authors: Gupta A. K. , Purwar S. N. 
Published: April 2003

AbstractStudies on impact behaviour of the blend of isotactic polypropylene (PP) with styrene‐b‐ethylene‐co‐butylene–b‐styrene triblock copolymer (SEBS) in the composition range 0–25 wt % SEBS at three temperatures, viz., ambient, −30°C, and −190°C, are presented. Dynamic mechanical properties on a torsion pendulum in the temperature range −100−100°C are also studied for this blend at various compositions. Scanning electron microscopic studies of the impact‐fractured surfaces are presented to illustrate the differences in the mode of fracture at the three temperatures of impact tests. Choice of the three temperatures for impact tests was such that the effect of shear yielding mechanism of toughening of PP at ambient temperature remains suppressed at −30°C, whereas at the lowest temperature (i.e., −190°C) the elastomeric role of the inclusion SEBS is suppressed. The observed considerably large difference in impact toughening at ambient temperature and at −;30°C seems not entirely accountable by the prevalence of shear yielding or crazing mechanisms in the respective temperature regions. A third mechanism, viz., viscoelastic energy dissipation, is invoked to account for the observed large difference of impact toughening at these two upper temperatures. Correlation of peak area of dynamic mechanical loss peaks occurring below the impact test temperature with the impact strength is also shown. This suggests greater significance of viscoelastic energy dissipation mechanism in the toughening of this blend at ambient temperature than at −30°C.
Photoregulated sorption of dyes to polymers I. The effect of polymers on some photochemical properties of acid yellow 38
Authors: Petrak K. , Douglas P. , Leyshon L. L. 
Published: April 2003

AbstractThe effect of polymers [gelatin, dextran, poly(vinyl alcohol), polyvinylimidazoles] on the photochemical and thermal isomerization of the water‐soluble bisazo dye, Acid Yellow 38, has been studied. The absorption spectrum curve of the cis AY38 isomer was obtained using the method of Fischer. We have shown that the rate of thermal cis–trans isomerization of AY38 is first order and independent of pH from 6 to 9. An activation energy of 84 ± 4 kJ mol−1 has been calculated for this process. The effect of added polymers on the rate of this conversion is relatively small. The quantum yields for the trans‐cis and cis–trans conversions have been estimated to be 0.15 ± 0.01 and 0.34 ± 0.03, respectively, for irradiation at 380 nm. Only polyvinylimidazoles were found to influence the behavior of the dye to any degree. For quaternized polyvinylimidazole the polymer/dye ratio determined solution turbidity, wavelength of maximum absorption, molar absorptivity, and the degree of conversion at photoequilibrium. The effect of polymer was interpreted in terms of increased dye/dye interactions due to high local concentration of the dye bound to polymer. The charge neutralization and crosslinking by the dye due to ionic interactions are seen to be the cause of polymer/dye complex precipitation. Precipitation occurs over a narrow [polymer]/[dye] ratio range.
A study on blends of nylon‐6 and nylon‐66
Authors: Verma Anu , Deopura B. L. , Sengupta A. K. 
Published: April 2003

AbstractBlending of nylon‐6 and nylon‐66 was carried out by coextrusion in the whole range of compositions with particular emphasis on small amounts of one polymer in the other. Most significant improvement in properties is achieved at low blend compositions in which the minor component remains amorphous while severely affecting the crystallization behavior of the major component. The nylon‐6‐rich blends crystallize predominantly in the γ‐crystalline form, whereas the nylon‐66‐rich blends exhibit low crystallinity. Because of this property, the blends are more easily drawable, giving rise to a more highly oriented structure with improved tensile properties and uniformity. High tenacity and modulus are observed in drawn blends containing 70% nylon 6 and 30% nylon‐66.