bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of liquid chromatography for the characterization of novolac resins
Authors: Podzimek Ŝ. , Hroch L. 
Published: April 2003

AbstractNovolac resins made by condensation of phenol or p‐cresol with formaldehyde in various mole ratios were analyzed by reversed‐phase high‐performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). Number‐average molecular weights (Mn) of phenol novolacs were determined by GPC and vapor‐phase osmometry (VPO) and compared. A relationship was found between the content of dihydroxydiphenylmethane (DHDPM) and Mn of phenol novolacs. Attention was also paid to the quantitative determination of the content of phenol and DHDPM in the analyzed samples. The molecular characters of novolacs synthesized from phenol or p‐cresol under the same conditions were compared. A relation was found between the molecular weight of phenol novolac and the tensile strength of abrasive material based on it. © 1993 John Wiley & Sons, Inc.
Dielectric and morphological investigations of phase separation and cure in rubber‐modified epoxy resins: Comparison between teta‐ and DDM‐based systems
Authors: Delides Costas G. , Hayward David , Pethrick Richard A. , Vatalis Argyris S. 
Published: April 2003

AbstractReal‐time and equilibrium dielectric measurements, covering the frequency range 10−1–105 Hz, are reported on a series of rubber‐modified epoxy resins, based on reaction of the diglycidyl ether of bisphenol A (DGEBA) with either triethylenetetramine (TETA) or diaminodiphenylmethylene (DDM). The rubber modifier used was a carboxyl‐terminated butadiene acrylonitrile (CTBN) reactive oligomer and the phase‐separated structure, the results of which was examined using both dielectric and electron microscopic techniques. The mixture was initially homogeneous, but after a short period of time, it underwent phase separation and this process was marked by the appearance of a dielectric peak associated with ion‐charge migration within the occluded rubbery phase. Analysis of the peak provided information on the morphology of the system and these data were compared with information obtained from scanning electron microscopy. A phase‐separated morphology was observed consisting of spherical rubber particles dispersed in an epoxy matrix. For high concentrations of rubber ≥ 10 wt %, precipitation of epoxy domains within the rubbery phase was observed. Detailed dielectric studies of the peak associated with phase separation revealed that in the case of the TETA system the peak continued to shift after vitrification, whereas in the case of DDM, it was invariant with time. The point at which the peak appears was used to determine the time at which phase separation occurred. Differences observed in the lower temperature dielectric spectra were associated with variations in the form of the phase structure and possibly reflect different degrees of densification of the matrix. Good agreement was observed between the predictions of the Maxwell—Wagner—Sillers (MWS) theory and experimental observation for these systems. © 1993 John Wiley & Sons, Inc.
Surface modification of ultrahigh molecular weight polyethylene fibers by plasma treatment. I. Improving surface adhesion
Authors: Gao Shanglin , Zeng Yeguang 
Published: April 2003

AbstractThe fiber/epoxy resin adhesion increases after plasma treatment on ultrahigh molecular weight polyethylene (UHMW‐PE) fibers. The surface modification of UHMW‐PE monofilaments was studied using a combination of techniques: contact‐angle measurements, SEM, and pullout tests. The results may be summarized as follows: Infiuenced by different plasma parameters and draw ratios of the monofilaments, the adhesion increases by at least four times by plasma treatment. Failure in the pullout tests involve rupture within a treated monofilament and the skin of it was peeled off; the degree of peeling‐off is affected by different plasma treatment conditions and draw ratios of the monofilaments. There is only a slight decrease in the surface energy of the treated monofilaments with aging time. Ways of combining plasma etching with other chemical treatments to further improve the fiber/resin adhesion have also been studied. © 1993 John Wiley & Sons, Inc.
Electrochemically oxidative polymerization of aniline in aromatic copolyamide matrix
Authors: Xue Zhijian , Bi Xian‐Tong 
Published: April 2003

AbstractComposite films from polyaniline (PAn) and a copolyamide, poly(p‐phenylene terephthalamide/diphenylether terephthalamide) (PPDTA), have been obtained by the electrochemical polymerization of aniline on a PPDTA/Pt (or Ni, stainless steel) working electrode in water or a mixed‐solvent electrolyte solution. This PAn/PPDTA composite has higher mechanical properties than does the PPDTA matrix and the electrical conductivity close to pure PAn. The electrochemical polymerization of aniline can be carried out only in the electrolyte solution with PH < 2. The PAn/PPDTA film is electroactive material and very stable in air. © 1993 John Wiley & Sons, Inc.
Kinetic and thermogravimetric analysis of thermal degradation of polychlal fiber/polyester fiber blend
Authors: Fukatsu Kazuhiko 
Published: April 2003

AbstractThe flammability behavior of a series of polychlal fiber/polyester fiber blends has been investigated in terms of the oxygen index and the thermal degradation characteristics. The thermal degradation behavior of these fiber blends has been studied by a conventional dynamic thermogravimetric technique in a flowing air atmosphere at several heating rates. Quantitative data are presented that pinpoint how the flammability behavior of the blends differs from that of the components. These results indicate that interactions occur between the polychlal and polyester fibers in the blends. © 1993 John Wiley & Sons, Inc.
Thermally stimulated current of iodine‐doped acrylonitrile–butadiene–styrene thin films
Authors: Bakr N. A. 
Published: April 2003

AbstractStructural change of acrylonitrile–butadiene–styrene (ABS) terpolymer due to iodine doping has been reported using both infrared (IR) and thermally stimulated current (TSC) techniques. IR investigation revealed the presence of a new stretching band at 640 cm−1 that indicates the formation of the C‐I structure. The TSC spectrum consists of two different decaying charge distributions of opposite polarity, which simply superpose to yield the net current observed. The variation of the position of the negative peak relaxation and its intensity as the iodine percentages increases indicates the formation of different ionic iodine species. The induced ionic dipoles superpose the α‐relaxation of ABS. © 1993 John Wiley & Sons, Inc.
Reductions in rate of yellowing following irradiation of poly[N(n‐butoxymethyl) methacrylamide]‐grafted silk fibers
Authors: Tsukada Masuhiro , Shiozaki Hideki , Crighton John S. , Kasai Nobutami 
Published: April 2003

AbstractThe physical properties, including changes in the yellowness index, following UV irradiation of Bombyx mori silk fibers loaded with poly[N(n‐butoxymethyl) methacrylamide], poly(BMA), are examined in relation to the amount of held polymer. The percentage weight gain by the silk fibers observed after 45 min at 80°C increased with increasing initial amounts of BMA monomer in the reaction system. Differential scanning calorimetry (DSC) observations suggest that the thermal decomposition behavior of the heated silk fiber was little affected, with but an apparent small shift of the endothermic decomposition temperature range to higher temperatures. The tensile properties of the treated silk fibers remained effectively unchanged, independent of the polymer weight gains. There was, however, a marked effect of the poly(BMA) weight gains onto silk in maintaining the whiteness and reducing the rate of yellowing following irradiation of treated habutae silk fabrics. These observations suggest that the rate of photoyellowing of silk fabrics can be retarded by the presence of the poly(BMA) in the fabric. © 1993 John Wiley & Sons, Inc.
The viscometric methods in the investigation of the polyacid‐polybase interpolymer complexes
Authors: Staikos G. , Bokias G. , Tsitsilianis C. 
Published: April 2003

AbstractTwo viscometric methods in the investigation of interpolymer complexes are presented. It has been shown that a presentation of the reduced viscosity ratio (experimental to ideal value) of a mixture of a polyacid with a nonionic polymer at constant total concentration as a function of the polymer mixture composition gives a better insight into the interpolymer association than a presentation of the specific viscosity at constant polyacid concentration as a function of the unit molar ratio. The formation of an expanded structure interpolymer complex is more easily revealed by the former procedure. © 1993 John Wiley & Sons, Inc.
Properties of hydroxypropyl methylcellulose–polyvinyl alcohol water systems, dispersants in vinyl chloride suspension polymerization
Authors: Zilberman E. N. , Lerner F. , Joseph H. M. , Alon M. 
Published: April 2003

AbstractAqueous solutions of partly hydrolyzed polyvinyl acetate (polyvinyl alcohol, PVA) and hydroxypropyl methylcellulose (HPMC) are used together as dispersants in vinyl chloride suspension polymerization. Surface tension, viscosity, and cloud point (CP) of diluted PVA and HPMC solutions at room temperature, viscosity of concentrated solutions as a function of temperature, and incipient gelation temperatures (IGT) were determined. Viscosity measurements show synergism of binary polymer mixtures. The synergetic effect diminishes with rise of temperature. IGT of PVA–HPMC solutions do not differ remarkably from those of solutions containing only HPMC and are much higher than the corresponding CP. At definite relative concentrations of HPMC and PVA, separation of the mixtures into two immiscible phases occurs. Each phase contains both polymers, but in the denser and more concentrated phase (lower layer), PVA is the prevailing component. The mutual influence of the two polymers causes changes in solute–solvent interaction, that is, dehydration of the polymers' molecules. It is assumed that in the processes occurring in the system, preferential molecules of definite structure take part. The merits of a system using both polymers as dispersants in the vinyl chloride polymerization are discussed in the light of ascertained data. © 1993 John Wiley & Sons, Inc.
Heat‐resistant thermosetting polyimide matrix resins containing keto, ether, hexafluoroisopropylidene linkages and maleimido‐ and nadimido‐ end capped groups
Authors: Kumar Devendra , Kaur Jasmeet , Gupta Alka D. 
Published: April 2003

AbstractVarious heat‐resistant thermosetting polyimides containing hexafluoroisopropylidene and keto and ether groups suitable for fiber‐reinforced composites development have been synthesised by thermal polymerization of maleimido and nadimido end capped polymer precursors. Thermal polymerization involving addition reactions was performed at 225°C for 1.5 h and post‐curing at 290°C for 0.5 h. Tough polymers XVIII to XXIII were obtained. The thermal polymerization was monitored using infrared spectroscopy. The polymer precursors were characterized by IR,1H‐NMR, and elemental analysis. The synthesized polymers were evaluated for thermal stability using dynamic thermogravimetric analysis (TGA). All the polymers showed thermal decomposition temperatures in the range of 430–435°C in nitrogen and in air. The char yield of the polymers was in the range of 60–67% in nitrogen at 800°C. This study indicated that thermally synthesized polymers from hexafluoroisopropylidene, keto, and ether containing polymides are potential candidates for the development of advanced materials for aerospace and high‐tech applications. © 1993 John Wiley & Sons, Inc.
Preparation and characterization of electropolymerized poly(N‐substituted maleimide‐co‐styrene) coatings on copper substrates
Authors: Liang Jeng‐Li , Bell James P. , Iroh J. O. , Mehta Ashit 
Published: April 2003

Abstractpoly(N‐substituted maleimide‐co‐styrene) copolymer films were electropolymerized onto copper substrates as possible candidates for electronic applications. The N‐substituted moieties that were investigated include phenyi, 3‐carboxyphenyl, and 4‐carboxyphenyl. Uniform coatings of 25 μm or more thickness were successfully applied using each of the three N‐substituted maleimides. The thickness was controlled by manipulating the monomer concentration, current density, and reaction time. Not only did the 3‐ and 4‐carboxyphenylmaleimide (CMI)/styrene copolymers have high glass transition temperatures (220°C) and fairly good thermal stability (≈ 430°C), but they also have rather low dielectric constants (2.55 for 4‐CMI/styrene), comparable to those of polyimides. Polymerization of the coatings was observed by in‐situ Fourier transform infrared spectroscopy (FTIRS), using a special cell that made the observation of the polymer structure development possible. It was found by FTIRS that all three monomers, when used with styrene, produced alternating copolymers. © 1993 John Wiley & Sons, Inc.
Dynamic mechanical properties of polyurethane grafted onto styrene–styrene sulfonic acid copolymers
Authors: Rutkowska Maria , Jastrzebska Mariola , Kim Joon‐Seop , Eisenberg Adi 
Published: April 2003

AbstractThe object of this study was the exploration of the dynamic mechanical properties and thereby also of the phase behavior of partly sulfonated polystyrenes containing polyurethane grafts. The synthesis was accomplished by stepwise grafting onto the partly sulfonated polystyrene of N‐methyldiethanoloamine, via ionic interactions resulting from proton transfer followed by chain growth on the hydroxyl sites of the polyurethane structures. NMR spectra confirmed that the protons of the sulfonic acid groups had been transferred exclusively to the tertiary nitrogen of the N‐methyldiethanoloamine. If the grafts consist of only hard segments, then a single glass‐transition temperature is observed that depends on the length of attached hard segment. If, on the other hand, soft segments are also included in the grafts, then these phase‐separate and yield a new glass‐transition temperature. For the phase‐separated systems, the grafts yield a low Tg phase of higher purity than blending of sulfonated polystyrene with the preformed polyurethane of the same composition. © 1993 John Wiley & Sons, Inc.
Dynamic mechanical studies of a highly filled composite structure: A lightweight coated paper
Authors: Hagen Roger , Salmén Lennart , De Ruvo Alf 
Published: April 2003

AbstractA composite sandwich structure, consisting of a paper sheet as a middle layer and two porous coating layers of a highly filled acrylate–styrene–butadiene copolymer, has been studied by means of a dynamic mechanical test in torsion. Stiffness and mechanical damping, tan δ, were recorded over the temperature region where the latex polymer exhibits a glass transition. The mechanical damping decreases with increasing filler content in the coating. Variations in the thickness of the coating layers did not influence the mechanical damping. The glass transition temperature of the latex polymer increases with increasing volume fraction of filler at high filler contents as an effect of filler–matrix interaction. The outer layers partly penetrate into the middle layer, as indicated by thickness measurements on the coated paper. A theoretical comparison of the peak heights of the mechanical damping using lamination theory shows a discrepancy in the experimental results. If penetration of the outer layer is allowed for, i.e., if using a thicker outer layer of the composite in the calculations, a favorable correlation between the theoretical and the experimental results is obtained. © 1993 John Wiley & Sons, Inc.
Silane cross‐linking of PVC. II. Influence of silane type and conditions on cross‐linking by water
Authors: Kelnar I. , Schätz M. 
Published: April 2003

AbstractThe cross‐linking of plasticized and unplasticized poly(vinyl chloride) (PVC) grafted with amino‐ and mercaptoalkyltrialkoxysilanes has been studied in water and in air at 20–140°C. In both media, the cross‐linking occurs faster for plasticized PVC grafted with aminosilanes; however, at temperatures above 100°C, the effect of degradation cross‐linking is apparent. For mercaptosilanes, a marked dependence of the cross‐linking rate on the silane structure was found; plasticized PVC with grafted 3‐mercaptopropyltrimethoxysilane was cross‐linked in water at 100°C after 6 h, whereas this process took 12 h for 5‐mercaptopentyltriethoxysilane. Practically no cross‐linking occurred in unplasticized PVC below Tg, whereas the rate at 100°C was comparable with that for plasticized PVC. The cross‐linking rate is affected by the chain mobility, water content, and diffusion of water into the material; a very slight dependence on the thickness of the material was found for plasticized PVC. © 1993 John Wiley & Sons, Inc.
The acetylation and enzymatic degradation of starch films
Authors: Parandoosh Shohreh , Hudson Samuel M. 
Published: April 2003

AbstractThe preparation of films from starch and their degradation by amylase enzymes is described. Starch acetate was prepared by acetylation of starch with a pyridine/acetic anhydride mixture. The resulting polymer was cast into films from solutions of 90% formic acid. A series of films with a range of acetyl content were then exposed to buffered amylase solutions and the retained tensile strength measured. It was found that with a sufficient acetyl content the wet strength of the films was maintained in the aqueous solutions, but that the acetyl content was sufficiently low enough to permit degradation by a mixture of alpha and beta amylases within a period of 1 h. These films could be useful as membranes in bioreactors, which could be degraded at will by the addition of enzymes to the system. © 1993 John Wiley & Sons, Inc.
Morphology‐property relationship of segmented polyurethaneurea: Influences of soft‐segment structure and molecular weight
Authors: Xiu Yuying , Wang Dening , Hu Chunpu , Ying Shengkang , Li Junxian 
Published: April 2003

AbstractThe relationships of the morphology and properties of a series of segmented polyurethaneurea (PUU) were studied in film form by using SEM and tensile stress‐strain data. The polyether‐based and polyester‐based PUU block copolymers were synthesized using poly(propylene oxide) ‐ethylene oxide polyether or poly(butylene adipate) polyester with different molecular weights, 4,4‐methylene bis(phenyl isocyanate), and diethyltoluene diamine. The extent of phase separation increased with increasing molecular weight of the soft segment. The polyether‐based PUU showed better phase separation than did polyesterbased PUU with the same molecular weight soft segment. The polyether‐ester‐based PUU showed the morphology of both polyether‐based and polyester‐based PUU but with larger domain size and interface. © 1993 John Wiley & Sons, Inc.
Melt blends of SAN with SAN‐graft‐polybutadiene (PB)
Authors: Kim B. K. , Shin G. S. 
Published: April 2003

AbstractMelt blends of SAN with SAN‐graft‐polybutadiene (PB) (g‐ABS) were prepared in a Brabender plasticorder. The effect of g‐ABS on the morphology and mechanical and viscoelastic properties of the blends was studied up to 60 wt % g‐ABS. The brittle‐tough (BT) transition occurred around 20 wt % g‐ABS, and the viscosity increased monotonically with g‐ABS, showing yield behavior at ≥ 20%. The lower and higher glass transition temperatures (Tg) of g‐ABS, each corresponding to the Tg of PB and grafted SAN, decreased and increased with the addition of free SAN, and this was interpreted in terms of graft SAN—PB phase separation. © 1993 John Wiley & Sons, Inc.
Semi‐interpenetrating polymer networks composed of poly(ethylene terephthalate) and vernonia oil
Authors: Barrett L. W. , Shaffer O. L. , Sperling L. H. 
Published: April 2003

AbstractSemi‐interpenetrating networks have been synthesized from vernonia oil‐sebacic acid polyester network and poly(ethylene terephthalate) (PET). Bond interchange reactions during mixing of the two materials led to the formation of a miscible copolymer mixture, in which the vernonia oil was then cross‐linked with sebacic acid. The materials were phase‐separated, exhibiting two glass transitions, when the network was synthesized at 160°C, below the crystallization temperature of PET: however, a single stable glass transition (Tg) results after the material is heated to above the melting temperature of PET and cooled. When the vernonia polyester network was completely formed at 250°C, above the crystallization temperature of PET, noncrystalline, single‐Tg material was created. The two‐phase semi‐IPNs were much tougher than were their constituent materials, with the 50% semi‐IPN over 15 times tougher than the PET from which it was made and over 50 times tougher than the neat vernonia oil elastomer, with tensile energy to break of 1780 kJ/m3. The single‐Tg material was nearly 2.5 times as tough as the two‐phase material, with energy to break of 4400 kJ/m3. The microstructure of the two‐phase 50% semi‐IPN was investigated by transmission electron microscopy, which showed regularly shaped spherulites of 10–20 μm in diameter, as compared to irregularly shaped spherulites observed in a similar 50/50 castor oil urethane/PET semi‐IPN, in which the network formed simultaneously with PET crystallization. Scanning electron microscopy of the semi‐IPN fracture surfaces showed microscopic fibrils several hundred nanometers in diameter in both the two‐phase and single‐Tg materials, although only the two‐phase semi‐IPN had a macroscopically rough surface. © 1993 John Wiley & Sons, Inc.
Study of the effect of annealing, draw ratio, and moisture upon the crystallinity of native and commercial gutta percha (transpolyisoprene) with DSC, DMTA, and X‐rays: Determination of the activation energies at Tg
Authors: Arvanitoyannis Ioannis , Kolokuris Ioannis , Blanshard John M. V. , Robinson Colin 
Published: April 2003

AbstractThe transitions occurring in gutta‐percha (transpolyisoprene) below the melting point were determined with DMTA and DSC. A comparison of the results obtained with these two methods showed satisfactory agreement. The thermal properties of native and commercial gutta‐percha samples (Tg = 38 ± 2°C and Tm = 69 ± 3°C) were investigated, both before and after annealing (at different times and temperatures), and at environments of different relative humidities. An increase in the draw ratio also proved to enhance the percentage crystallinity (% K) and improve the thermal stability (higher Tgs and Tms) of gutta‐percha. Finally, the activation energies ΔE (33.9–40.2 kj/mol × K) at glass transition temperature were determined and correlated to the percentage content (%) of the commercial gutta‐percha samples in native gutta‐percha. © 1993 John Wiley & Sons, Inc.
Synthesis and microbial degradation of poly(2‐methyl phenylene oxide)
Authors: Li Li‐Xia , Grulke Eric A. , Oriel Patrick J. 
Published: April 2003

AbstractThe synthesis and biodegradation of poly(2‐methyl phenylene oxide) was studied as an example of a synthetic polymer containing a biodegradable aromatic backbone. Polymer prepared with cuprous 2,2‐isopropoxy ethyl pyridine catalyst demonstrated good blending properties with polystyrene. In soil experiments, the homopolymer degraded readily with over 50% reduction in 40 days. No. oligomeric intermediates were observed by gel permeation chromatography, suggesting degradation by cell‐associated enzymes. © 1993 John Wiley & Sons, Inc.