bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rayleigh–brillouin scattering from reacting epoxy resins: Comparison with torsional braid analysis
Authors: Kondo Shingo , Igarashi Takashi , Nakamura Tsutomu 
Published: April 2003

AbstractThe rheological study for isothermal curing processes of two kinds of epoxy/amine systems made by Rayleigh–Brillouin spectroscopy was compared with torsional braid analysis. The Brillouin shift increased with the increase in the density during the process. The intensity ratio of Rayleigh line to Brillouin lines (LP ratio) increased remarkably in accordance with the onset of gelation measured by extraction. The increase of scattered light suggests that some kind of density fluctuation of the order of the light wavelength takes place prior to the gelation. The longitudinal elastic modulus and the attenuation of sound in the hypersonic region changed monotonically from the start of measurement and almost leveled off after the transition to the glassy state determined by dilatometry. While the relative shear modulus in a low‐frequency region (0.1 ∼ 1 Hz) was not sensitive to the onset of gelation, it was markedly affected by the approach to the glassy state.
Ultradrawing and crystallization of isotactic polystyrene and blends with atactic polystyrene
Authors: Wang Li‐Hui , Porter Roger S. 
Published: April 2003

AbstractPure isotactic polystyrene (iPS, Mw = 8.89 × 104, Mw/Mn = 4.89) and its blends with an atactic polystyrene (aPS, Mw = 3.9 × 105, Mw/Mn < 1.13) were subjected to draw by solid state coextrusion at 127°C within polyethylene. The content of amorphous iPS in these blends was varied from 100 to 24.4 wt %. The extent of draw‐induced crystallization was found to depend on the draw ratio and on iPS concentration. The blend with 24.4% iPS was coextruded in two stages. The highest effective draw ratio (EDR) was 7.6 and 13.7 for one‐ and two‐stage draw, respectively. The highest crystallinity of 33.2% was obtained for pure iPS at the maximum EDR of 7.6. Considerable crystallinity was induced in blends, requiring successively higher draw ratio to reach similar crystallinity with increased aPS content. The tensile modulus increased from 1.5 to 3.2 GPa, independent of iPS concentration. Thermal shrinkage results indicate that the elastic recovery of draw in the blends is near quantitative for an EDR < 8. For pure iPS, extrudate elastic recovery was dramatically altered by the draw‐induced crystallinity.
Copolymerization of pentachlorophenyl acrylate with vinyl acetate and ethyl acrylate. Polymer‐bound fungicides
Authors: Pittman Charles U. , Stahl G. Allan 
Published: April 2003

AbstractCopolymers of pentachlorophenyl acrylate (M1) with both vinyl acetate and ethyl acrylate were prepared (in benzene at 60°C initiated by t‐butyl peroxypivalate) at a variety of M1/M2 ratios. The reactivity ratios for the vinyl acetate (M2) copolymerizations were r1 = 1.44 and r2 = 0.039, while for ethyl acrylate copolymerizations r1 = 0.21 and r2 = 0.88. The glass transition temperatures were obtained as a function of the M1/M2 ratio. The values of Tg for the copolymers fell between those of poly(pentachlorophenyl acrylate) and either poly(vinyl acetate) or poly(ethyl acrylate). A series of bulk copolymers with low pentachlorophenyl acrylate content were studied as biocidal coatings using accelerated growth agar dish tests inoculated with Aspergillus sp., Pseudomonas sp., Alternaria sp., and Aureobasidium pullulans. The copolymers retarded or prevented growth but did not give a zone of inhibition around the coatings. Pentachlorophenol, when added to coating polymers, did exhibit a zone of inhibition due to migration of this biocide into the agar medium.
Correlation between the mechanical behavior and relaxation processes in the plastically deformed polycarbonate
Authors: Hong Jauwhei , Brittain J. O. 
Published: April 2003

AbstractThe low‐temperature β relaxation has been studied via thermally stimulated depolarization current (TSD) method for polycarbonate that had been cold‐rolled and subsequently undergone the α′ relaxation at 70°C as a function of time. It has been found that the intensity of the β process increased as the annealing at 70°C increased. The analysis of the activation energy spectrum associated with the β relaxation indicated that the enhancement in the β intensity was due to the liberation of local dipoles from their aligned orientation as a result of undergoing the α′ relaxation process. Tensile flow curves have also been determined for the same set of specimens. Similar enhancement was also observed in the yield stress behavior. In view of the good correlation between the mechanical property and the structural change revealed by the relaxation study, it was concluded that the variation of the yield stress and the work‐hardening in the rolled polymer was primarily associated with those parts of the chain that had been disoriented from their frozen‐in conformations.
Morphological effects on the bulk polymerization of trioxane in the solid state by γ‐radiation
Authors: Kiss Gabor , Kiss Klara , Kovacs A. J. , Wittmann J. C. 
Published: April 2003

AbstractThe solid‐state polymerization by γ‐radiation and postpolymerization of bulk samples of trioxane has been investigated. Different thermal treatment results in radically different initial morphologies of the melt‐crystallized trioxane which in turn have a profound influence on the yield and morphology of the resulting poly(oxymethylene) (POM). The polymerization yield increases in the following series: melt‐crystallized trioxane with an “opaque” (small grains) morphology, as‐grown needles, trioxane with a “quasi‐transparent” morphology, and finally thermally oriented crystals. Furthermore, little additional POM is formed during repeated polymerization cycles. The observation of an extensive nodulation of the polymer fibrils when the yield is high is consistent with a multiple‐stage growth model for the solid‐state polymerization of trioxane.
Influence of tacticity and sorbed water on the material properties of poly(N,N'‐dimethylacrylamide)
Authors: Mohajer Y. , Wilkes G. L. , McGrath J. E. 
Published: April 2003

AbstractThe effects of variation in tacticity on the thermal, morphological, stress–strain and stress–relaxation properties (both in the dry state and 140°C, and at a RH of 72% and ambient temperature) were evaluated for a series of homopolymers of poly(N,N‐dimethylacrylamide). In the range of 19 to 23% tacticity (isotactic content), a fundamental change in the level of crystallinity and morphology occurs for this series of polymers which in turn greatly affects the above‐mentioned properties. Below 19% tacticity, the polymers are amorphous, but above 23% they are distinctly semicrystalline. Sorbed water plasticizes all these polymers, but the influences of the water on the stress–strain properties is greatest for the amorphous polymers, where the relative sorption of water is also highest.
Catalysis of the reaction between isocyanates and protonic substrates. I. Metal salt–amine complexes as catalysts in the polyurea foaming process
Authors: Borsus J. M. , Jérôme R. , Teyssié Ph. 
Published: April 2003

AbstractTertiary amines and metal [Cu(II), Zn(II)] salts exhibit a synergistic effect in the catalysis of the isocyanate water reaction. The amino complexes of zinc and copper salts display a very large versatility in defining the most suitable formulations for the polyurea foam production. The foaming process is indeed controlled by the nature and the composition of these new catalytic combinations; kinetics of foaming and textural characteristics of final foams are easily modified in that way.
Condensation products from imidobis(sulfuryl chloride)
Authors: Argyropoulos D. , Lenk R. S. 
Published: April 2003

AbstractA study of model compounds and polycondensation products derived from imidobis(sulfuryl chloride) (IBSC), HN(SO2Cl)2, has been carried out and their structures determined. The model compounds were reaction products of IBSC with aniline or ethyl alcohol. Polymeric products were obtained by polycondensations with (1) p‐phenylenediamine and (2) 2,2‐bis(4'‐hydroxyphenyl)‐propane. The products were characterized by elemental analysis, infrared, NMR, DSC, TGA, and viscometry data.
Block copolymers obtained by free radical mechanism. II. Butyl acrylate and methyl methacrylate
Authors: Gunesin Binnur Z. , Piirma Irja 
Published: April 2003

AbstractBlock copolymers were synthesized using methyl methacrylate and butyl acrylate as the monomers and a multifunctional initiator, di‐t‐butyl 4,4'‐azobis(4‐cyanoperoxyvalerate). The polymerizations for the formation of the block copolymers were carried out in two stages. First the poly(methyl methacrylate) polymeric initiator was synthesized and isolated. In the second stage, the thermallyactivated azo group in the polymer backbone initiated the polymerization of butyl acrylate. Upon termination by combination a tri‐block results. Selective solvent fractionation was used to separate the block from the homopolymers.
Grafting vinyl monomers onto cellulose. IV. Graft copolymerization of methyl methacrylate onto modified cellulose using peroxydiphosphate as the initiator
Authors: Lenka Subasini , Nayak Padma L. , Mishra Munmaya K. 
Published: April 2003

AbstractThe graft copolymerization of methyl methacrylate onto modified cellulose was studied at 60° causing peroxydiphosphate as the initiator. The rate of grafting in case of different modified cellulose was determined by varying peroxydiphosphate, monomer, nature of substrate, and temperature. The molecular weight of the isolated polymer has been determined, and the mechanism of grafting is discussed.
Modification of polyvinylchloride in solution or suspension by nucleophilic substitution
Authors: Marian S. , Levin G. 
Published: April 2003

AbstractNucleophilic displacement of chlorine from polyvinylchloride (PVC) suspended either in water or in solution can be achieved using a nucleophile such as a sodium thiolate (RS−, Na+). The nucleophilicity of the salt increases if an ether linkage exists in a β position to the thiol group [RO(CH2)2S−, Na+]. Addition of a solvent such as cyclohexanone (which is a good solvent for PVC) to the slurry increases substantially the degree of substitution. Elemental analysis shows that every chlorine displaced from the polymer is replaced by a thiolate group; thus almost no dehydrochlorination occurs. It is possible to obtain by this method a grafted polymer in which 33% of the chlorine atoms are replaced by the β‐ether thiolate group. The resulting polymer behaves like an internally plasticized PVC. The higher the degree of substitution of chlorine, the greater the flexibility of the grafted polymer is. Other compounds, such as lauryl thiolate and diethyl dithiocarbamate, also were used as nucleophiles, the latter one resulting in a brittle crosslinked polymer whenever sulfur was above 2%. Grafting of polytetrahydrofuran from PVC also was achieved using tetrahydrofuran as solvent and silver‐perchlorate as catalyst. The resulting flexible grafted polymer is believed to consist of longer chains of polytetrahydrofuran grafted from few displaced chlorine atoms along the PVC chain.
Rate characteristics for the reaction of carboxyl‐modified polyamide with potassium hydroxide
Authors: Healy E. M. , Ramsley A. O. , Herz M. L. 
Published: April 2003

AbstractNylon 66 fiber, carrying 2.0 meq/g of carboxyl groups from radiation grafting of acrylic acid, was found to display chemical kinetics strongly first order with respect to the potassium hydroxide. The apparent rate constant k' remains nearly unchanged as the initial bath pH is varied from 8.3 to 10.5. At this point, the value of k' drops sharply, and continues to drop as the initial pH is increased. This discontinuity is attributed to a previously reported morphological transition indicated by a break in titration data at the corresponding equilibrium point of pH 9.2.
Influence of external environments on fracture toughness of epoxy resin
Authors: Mizutani K. , Iwatsu T. 
Published: April 2003

AbstractCrack propagation in an epoxy resin in the presence of organic solvents was investigated. Fracture toughness (KIC, a critical stress intensity factor) of the epoxy resin in various external environments was measured using a double cantilever beam specimen. Fracture toughness for initiation (KICi) of the resin in the presence of organic solvents was larger than that in the absence of solvents, and the epoxy resin showed a minimum value of KICi in the presence of the organic solvent whose solubility parameter was about 11 (cal/cm3)1/2. This was due to large plastic deformation at a crack tip and the yield strength was lowered by exposure to organic solvents. The former increases KIC, while the latter decreases KIC. Fracture surfaces of the resin fractured in solvents suggest that a crack grew slightly when accompanied by a large plastic deformation, and then propagated at high speed.
Prediction of second virial coefficients from intrinsic viscosities
Authors: Kok Chong Meng , Rudin Alfred 
Published: April 2003

AbstractOne of the most readily available characteristics of a polymer sample is its intrinsic viscosity in a particular solvent. This datum can often be estimated reasonably from a single relative viscosity measurement. A number of theories permit the calculation of the second virial coefficient of a polymer/solvent mixture given the intrinsic viscosity and polymer molecular weight. The intrinsic viscosity of the polymer under theta conditions is also needed, but this can be estimated, if necessary, from the molecular weight. This article compares the efficiencies of various alternative models for the prediction of second virial coefficients of a series of polymers and solvents. The most effective technique for this purpose first calculates the concentration‐dependent equivalent hydrodynamic volume of a solvated polymer coil. This value is used with a primitive statistical mechanical theory for virial coefficients of hard‐sphere suspensions to calculate the osmotic pressure or turbidity of the polymer solution. These simulated experimental values are fitted with a least‐squares line as in the real experiment, and the second virial coefficient is derived from the slope. The computations are relatively simple; the average deviation between observed and predicted virial coefficient was less than 16% for a variety of polymer types, molecular weights, and solvents.
Biodegradation of gelatin–g‐poly(ethyl acrylate) copolymers
Authors: Kumar G. Sudesh , Kalpagam V. , Nandi U. S. , Vasantharajan V. N. 
Published: April 2003

AbstractGelatin‐g‐poly(ethyl acrylate) copolymers were prepared in an aqueous medium, using K2S2O8 initiator. The composition of the graft copolymers was dependent upon temperature and duration of the reaction. The number of grafting sites was small and molecular weight of the grafted poly(ethyl acrylate) branches was high. Three copolymer samples with grafting efficiencies of 33.3%, 61.0%, and 84.0%, were tested for their microbial susceptibility in a synthetic medium employing a mixed inoculum of Bacillus subtilis, Pseudomonas aeruginosa, and Serratia marcescens and the percent weight losses were 12%, 10.1%, and 6.0%, respectively, after 6 weeks of incubation. The extent of degradation seems to decrease with increasing grafting efficiency. There was initial rapid weight loss accompanied by the exponential increase in bacterial population and pH of the culture medium during the first week. The nitrogen analysis also showed the utilization of the polymer. A parallel set of experiments, carried out by employing the samples as the only source of both carbon and nitrogen, showed a marginal but definite increase in the utilization of the polymer.
Poly(vinyl chloride)–polyol (AB)x block copolymers: Synthesis, characterization, and mechanical properties
Authors: Laverty John J. , Gardlund Zack G. 
Published: April 2003

AbstractPoly(vinyl chloride)–polyol (AB)x block copolymers have been prepared by the condensation polymerization of low‐molecular‐weight hydroxy‐terminated poly(vinyl chlorides) (PVC) and diisocyanate‐capped polyester and polyether diols. The difunctional poly(vinyl chlorides) were synthesized by ozonization of commercial resin followed by metal hydride reduction. The (AB)x block copolymers, which contained 3000 or 4300 molecular weight PVC block sizes and 1000–2000 molecular weight polyol segments, had a wide range of mechanical properties, depending on overall polymer structure. Tensile strengths ranged from 7.8 to 31.5 MPa, elongations from 125% to 610% and torsional stiffness temperatures (Tf) from 25°C to −22°C.
The radiation crosslinking of poly(vinyl chloride) with trimethylolpropane trimethacrylate. I. Dose dependence and the effects of thermal treatment
Authors: Bowmer T. N. , Davis D. D. , Kwei T. K. , Vroom W. I. 
Published: April 2003

AbstractThe radiation crosslinking of poly(vinyl chloride), PVC, with trimethylolpropane trimethacrylate, TMPTMA, has been examined. The polyfunctional TMPTMA undergoes rapid polymerization incorporating the PVC into a three‐dimensional network. The kinetics and mechanism of these crosslinking reactions were studied with particular reference to dose dependence and thermal treatment. The gel was rapidly formed with a TMPTMA polymerization rate greater than that of the PVC grafting reaction. Only 30–40% of the available bonds were used in the initial polymerization. The remaining 60–70% of the double bonds predominantly react in the final stages of crosslinking (80–100% gelation). The macroscopic properties (e.g., solubility, glass transition temperatures, mechanical characteristics, etc.) of the PVC–TMPTMA blend are discussed in terms of the molecular crosslinking mechanism. The effect of thermal treatment, during and after irradiation, on the reaction rates and mechanism is examined.
Study of domain structure in linear and crosslinked polyurethanes using pulsed proton NMR
Authors: Assink R. A. , Wilkes G. L. 
Published: April 2003

AbstractPulsed proton magnetic resonance was used to study the domain structure of a series of polyurethanes which had been crosslinked to various degrees at 210°C. The difference between segmental mobility of the hard and soft phases decreases with crosslinking. The fraction of rigid segments in the linear material decreases in two distinct stages as the temperature increases, while the fraction of rigid segments in the crosslinked material decreases in a continuous fashion as the temperature increases. Crosslinking also decreases the rate of domain formation following thermal treatment. These effects are attributed to the inability of the segments in the crosslinked material to completely segregate into domains.
Factors affecting initial bond strength in solvent‐based contact adhesives
Authors: Kozakiewicz Janusz , Kujawa‐Penczek Bibianna , Penczek Piotr , Puton Krzysztof 
Published: April 2003

AbstractNovel interpretation is given for the development of initial bond strength maximum in solvent‐based contact adhesives at particular elastomer/resin ratios in the adhesive films. Complex relations between initial bond strength, tack of adhesive films, adhesive open time, solvent retention, and resin content in adhesive films are discussed. These results are based on data using polychloroprene adhesives modified with butylphenolic resins and also on previous studies with other contact adhesives. It is suggested that solvent retention is the main factor affecting initial bond strength in solvent‐based contact adhesives.
Photooxidation of the surfaces of polyphenylene oxide and polysulfone
Authors: Peeling James , Clark David T. 
Published: April 2003

AbstractChanges in the composition and structure of the surfaces of polyphenylene oxide (PPO) and polysulfone caused by UV photooxidation are followed using ESCA. The surface stoichiometry of PPO changes from C8O1 to C8O4.8 on photooxidation, the oxygen being added in the form of carbonyl and especially carboxyl groups. Surface photooxidation is rapid, the ESCA spectra showing substantial changes after a few minutes of irradiation, and no further changes being detected after 10 h of reaction. The surface photooxidation of polysulfone occurs in three stages. In the first 2 h rapid oxidation takes place at carbon atoms, the levels of C—O, carbonyl, and carboxyl groups increasing at comparable rates. This is followed by slower oxygen incorporation up to 15 h of reaction, during which time carbonyl and carboxyl levels increase and oxidation of the sulfone sulfur is observed. Some degradation occurs as groups containing carbon and oxygen are lost from the surface. Further oxidation then produces a decrease in the surface levels of C—O and carbonyl groups, and further degradation. The photooxidized surface has a stoichiometry of C10O6S, compared with C27O4S in the unreacted polymer.
Polyimide structure–property relationships. III. Polyimides from multi‐ring diamines
Authors: Bell Vernon L. , Kilzer L. , Hett E. M. , Stokes George M. 
Published: April 2003

AbstractThe effects of increasing the distance between, and varying the isomeric positions of, the amine groups on the glass transition temperatures of aromatic polyimides were studied in order to investigate routes to improve processability. A number of isomers of three‐ and four‐ring benzenoid diamine systems were polymerized with 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride to poly(amic acids), which were converted to polyimides. The use of methylene and carbonyl groups to connect the benzene rings of the diamines, and in one case the dianhydride, afforded a comparison of the thermomechanical properties of the polyimides to those prepared from diphenylmethane‐ and benzophenone‐diamines, respectively. Generally, the dilution of the imide content by the insertion of benzylene and benzoylene segments into the diamines significantly reduced the glass transition temperatures, with the benzylene group being more effective in that respect than the benzoylene. However, there was evidence that the position isomerism (ortho, meta, para) of the amine groups was more influential in affecting the glass transition temperatures of aromatic polyimides than was the dilution of the imide content.
A reinvestigation of parabanic acid–formaldehyde polymerization
Authors: Cassidy Patrick E. , Fawcett Newton C. , Thomas Richard W. 
Published: April 2003

AbstractAn earlier paper reported the synthesis of derivatives of parabanic acid, mono‐ and dimethylol parabanic acid, and their polymerizations with themselves and with aqueous formaldehyde. The study is reported herein to clarify that work. The reported synthesis of monomethylol parabanic acid was not reproducible. Identical low‐molecular‐weight polymers were obtained from the condensation of parabanic acid with formalin and from the self‐condensation of dimethylol parabanic acid. The final polymer contains a little of the original parabanic acid and a large amount of the condensation product from a ring opening byproduct. Commonly, two products are possible, a soluble one at lower reaction times and temperatures and an insoluble one at longer times and temperatures. Films cannot be formed by solvent casting or heat pressing. Elemental analyses and infrared spectra show that the actual products are not of the structure originally proposed.
Miscible blends of poly(styrene‐co‐allyl alcohol) with poly‐ϵ‐caprolactone
Authors: Barnum R. S. , Goh S. H. , Paul D. R. , Barlow J. W. 
Published: April 2003

AbstractBased on the single, composition‐dependent glass transition criterion, poly‐ϵ‐caprolactone (PCL) was found to be miscible with each of four poly(styrene‐co‐allyl alcohol) (SAA) copolymers with hydroxyl contents between 1.3 and 7.7 wt %. Melting point depression of the PCL in the blends was used to evaluate the blend interaction parameter B for each miscible system. The parameter B was found to be negative and to vary with copolymer composition in a way that suggests that an optimum density of alcohol moieties in the copolymer exists for achieving maximum interaction with PCL.