bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological behavior of partially hydrolyzed poly(vinyl acetate‐co‐ethylene)
Authors: Han Chang Dae , Ma Yu‐Jiang , Chu Sung Gun 
Published: April 2003

AbstractThe rheological behavior of partially hydrolyzed poly(vinyl acetate‐co‐ethylene) (VAE) was investigated, using a Rheometrics Dynamic Mechanical Spectrometer. For the investigation, measurements of storage modulus (G′), loss modulus (G″) and loss tangent (tan δ) of the materials were recorded as functions of temperature at a fixed frequency (i.e., using temperature scans) and, also, as functions of frequency at a fixed temperature (i.e., using frequency scans). For the hydrolysis, three different grades of copolymer (containing 34, 47, 62 mol% of vinyl acetate) were used to yield poly(vinyl acetate‐co‐ethylene‐co‐vinyl alcohol) (VAEOH) with varying amounts of hydroxyl group. For comparison purposes, the viscoelastic properties of blends of VAE copolymer with poly(vinyl alcohol) (PVOH), having varying blend compositions, were also measured. The blends were prepared by first mixing a solution of VAE copolymer, which was dissolved in a toluene/dichloroethane mixed solvent, and an aqueous solution of PVOH, and then freeze drying the mixture to a constant weight. Also measured were the glass transition temperature (Tg) of the VAE copolymers and the Tg and melting point (Tm) of the VAEOH terpolymers, using a DuPont Thermal Analyzer equipped with a 910 DSC Module. It has been found that (1) introduction of hydroxyl group into the backbone of the amorphous VAE copolymer has made the resulting VAEOH terpolymer semicrystalline; (2) the Tm, Tg, G′, and the complex viscosity (η*) of the VAEOH terpolymers increase with increasing amounts of hydroxyl group; (3) the physical blending of PVOH with VAE copolymer has not affected the Tg of the VAE copolymer; (4) the G′ and η* of the VAE/PVOH blends are found to increase with the amount of PVOH in the blend. The use of logarithmic plots of G′ versus G″ has been found to be very useful for discerning the differences in the structure of the materials tested.
Graft copolymers from peroxidized EPDM rubber
Authors: Dean Barry D. 
Published: April 2003

AbstractThe transition metal catalyzed peroxidation of the pendant allylic functionality in EPDM rubbers with tertiary butyl hydroperoxide results in elastomeric, high polymer peroxides. The peroxidized EPDM rubbers are useful as free radical initiators for the polymerization and grafting of vinyl monomers in the preparation of comb‐type structures. The grafted EPDM rubbers are efficient impact modifiers for thermoplastic resins so long as the polymer grafted onto the EPDM is identical to or is thermodynamically miscible with the composition of said thermoplastic resin.
Study of polymer–solvent interactions by gas chromatography. Copolymers of vinyl acetate and vinyl alcohol with hydrocarbons and alcohols
Authors: Castells Reynaldo César , Mazza Germán Delfor 
Published: April 2003

AbstractThe specific retention volumes of nine hydrocarbons and 12 alcohols were measured at several temperatures within the range 120–150°C in columns whose stationary phases were poly(vinyl acetate) (PVAc) and four copolymers of vinyl acetate and vinyl alcohol with 94.8, 74.4, 60.9, and 43.4 mol % of vinyl acetate units (mol % VAc). No chromatographic retention for hydrocarbons was detected in columns loaded with poly(vinyl alcohol) (PVA) or a copolymer with 11.9 mol % VAc. The retention trends are discussed and the polymers solubility parameters (δ2) were computed from the measured Flory–Huggins χ parameters. The copolymers δ2 values increase almost linearly with decreasing mol % VAc; PVAc, however, has a distinct behavior. The limitations of the approach in the prediction of χ parameters are discussed.
Microcavity formation in poly(ester–carbonate) exposed to hot, humid environments
Authors: Robeson L. M. , Dickinson B. L. , Crisafulli S. T. 
Published: April 2003

AbstractThe behavior of polycarbonate in hot, humid environments has been well documented in the technical literature. Poly(ester–carbonate)s based on bisphenol A connected with carbonate and tere/isophthalate units are the subject of this investigation. Poly(ester–carbonate) exhibits many similarities to polycarbonate in microcavity formation when exposed to cycling hot, humid environments. These microcavities consist of concentric bands around a central nucleation site. Scanning electron microscopy reveals that the bands consist of rings of dense material alternating with rings of material containing microvoids. Water phase separation at the nucleation site (due to cycling temperature) leads to internal pressure and thus a dilatant stress around the edge of the microcavity. It is hypothesized that this allows for the ease of further water phase separation at the periphery of the microcavity, thus yielding microvoids. The mechanical properties of poly(ester–carbonate) exposed to 96°C water immersion and 132°C steam sterilization cycling were determined and show significant loss in performance in these environments similar to that previously reported for polycarbonate.
Ionic photoinitiators for radical polymerization in direct micelles: The role of the excited states
Authors: Fouassier J. P. , Lougnot D. J. 
Published: April 2003

AbstractRadical photopolymerization reactions of MMA in direct anionic and cationic micelles are investigated in the presence of different types of ionic initiators, through steady state illumination experiments and time‐resolved laser spectroscopy. The positively charged ionic photoinitiator BP+ appears as the more efficient. The reactivity of the excited states involved as well as the behavior of the side radicals produced seem to govern for a large part the practical efficiency of these compounds. A general discussion on the role of the different factors (localization, electronic effects, monomer quenching, electron and proton transfer processes, radical exit from the micelle, and acid–base equilibrium) is presented.
Poly(phenylene oxide) composites containing crosslinked polystyrene microspheres. I. Stress–strain properties
Authors: Zhikuan Chai , Tiangui Wang , Qipeng Guo 
Published: April 2003

AbstractThe stress–strain properties of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polystyrene composites containing crosslinked polystyrene microspheres have been measured at strain rates of 0.167, 1.67, and 16.7 min−1. It is found that Young's modulus almost has no increase with the filler content. The elongation at break and tensile strength decrease with the volume fraction of the filler, but both tend to flatten out at the volume fraction νf > 0.25 at the strain rate of 1.67 min−1. The two ultimate tensile properties also have maximum values in the relationship with strain rate at the same filler concentration and strain rate conditions. Considering that elongation can be brought about by both matrix and filler, the well‐known equation of elongation at break becomes
Low‐angle laser light scattering–aqueous size exclusion chromatography of polysaccharides: Molecular weight distribution and polymer branching determination
Authors: Yu Li‐Ping , Rollings J. E. 
Published: April 2003

AbstractA low‐angle laser light scattering detector (LALLS) used with size exclusion chromatography (SEC/LALLS) has been applied for the determination of molecular weight, molecular weight distribution (MWD), and degree of branching of polysaccharides in 0.5N NaOH aqueous solution. Data from both detectors [differential refractive index (DRI) and LALLS] are used to calculate the absolute molecular weight at each point in a sample chromatogram. The correct average molecular weight and MWD can be obtained without calibration methods used in conventional SEC. As a consequence of this technique, Mark—Houwink coefficients can be predicted from a single broad‐distribution, homopolymer without recourse to time‐consuming fractionation methods. Moreover, the hydrodynamic volume separation mechanism of SEC can be exploited with the SEC/LALLS method to gain information about polymer branching. In the studies described in this paper, SEC/LALLS has been employed to obtain data about the branching parameters gv and gM for samples of amylose, amylopectin, starch, and glycogen. For three homopolymers (amylose, amylopectin, and glycogen), branching frequency (as measured by chemical means), and the branching parameters (gv and gM) are inversely related. This trend is consistent with theoretical predictions. For starch, a nonhomogeneous branching distribution is observed as a function of molecular weight.
Derivative ultraviolet and visible spectrophotometry: Applications to polymer analysis
Authors: Mori Sadao 
Published: April 2003

AbstractFirst‐ to fourth‐derivative spectra of humic acids, polystyrene, and mixtures of several prepolymers were measured and the advantage of derivative spectrophotometry such as resolution enhancement and background correction was discussed. Although the vis‐absorption spectra for humic acids in pH solutions from pH 2.0 to 10.0 could be hardly discriminated, humic acids in solutions above pH 7.0 could be clearly distinguished from those in solutions below pH 6.0 by first‐derivative spectrophotometry. Similarly, the first‐derivative spectra of the copper‐humic acid complex were different from those of free humic acids, though both absorption spectra resembled each other. UV absorption spectrum of a mixture of phenol‐novolac resin and methylated methylol‐melamine resin was similar to and the second‐derivative spectrum was different from that of phenol‐novolac resin. The difference of derivative spectra of a mixture of polycarbonate and epoxy resin was also discussed. Shoulder and unresolved peaks were clearly revealed by differentiation of absorption spectra and peak assignments from the fourth‐derivative spectra were more accurate than those from the absorption spectra. This advantage was discussed by using polystyrene as an example.
Effect of thermal hysteresis on melting of syndiotacticity‐rich poly(vinyl alcohol) hydrogel
Authors: Yamaura Kazuo , Takahasi Tatsuya , Tanigami Tetsuya , Matsuzawa Shuji 
Published: April 2003

AbstractThe melting temperatures (TM) of hydrogels prepared by chilling aqueous solutions of syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA) at 0°C were measured rising temperature of gels from the initiative temperature (TI) of 0–70°C (every 10°C). The apparent enthalpies of fusion of a junction ΔH's were estimated from the relation between the logarithm of polymer concentration (log C) and 1/TM. ΔH depended on TI, showing that the melting point of gels depended on a thermal hysteresis. The highest polymer concentration CH in those of the gels which have no melting point above an initiative temperature was determined and ΔH was estimated from the relation between log CH and the reciprocal melting point of the gels with CH, 1/TIM. The ΔH was 15.1 kJ/mol in the range of higher polymer concentrations and 43.9 kJ/mol in the range of lower concentrations.
Analysis of the flow behavior of HDPE/LDPE blends using a kinetic network model
Authors: Manero O. , Rangel‐Nafaile C. , García‐Rejón A. 
Published: April 2003

AbstractTheoretical predictions of the flow behavior of high and low‐density polyethylene polymer blends have been obtained using the kinetic network model proposed by Williams et al. The results show that this model can be used even in the case of polydisperse components having similar relaxation spectra. Furthermore, in order to obtain meaningful predictions, the characterization of the complete system (blends and pure components) should be carried out on samples with the same thermomechanical history. Experimental data show that the shearing history influences the rheological properties of the pure homopolymers to a measurable and significant degree and that it has to be taken into account when these properties are used to predict the flow behavior of their blends.
Study on ketalization reaction of polyvinylalcohol by ketones. I. Reaction between polyvinylalcohol and acetone
Authors: Nakamura Naofumi 
Published: April 2003

AbstractKetalization reaction of polyvinylalcohol (PVA) by acetone, dimethylsulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out and the synthesis of polyvinylketal with any ketalization degree was successfully performed. This reaction proceeds in bimolecular reaction, the equilibrium constant is ca. 0.07 at 40°C and roughly 10−5 less compared with the acetalization reaction between PVA and aldehydes. Synthesis in aqueous media is difficult. However, the heat of reaction for both cases is 7.5 kcal/mol and both reactions are considered to proceed in an identical reaction mechanism. Ketalization reaction starts from isotactic OH portion and proceeds finally to syndiotactic OH portion, however, 100% ketalization is extremely difficult. The effects of water on reaction was confirmed both from theoretical and experimental viewpoints, and even though the presence of water lowers the degree of ketalization, it was observed that the presence of water below 0.1 mol against 1 mol of PVA will not significantly affect final ketalization degree. Polyvinylketals thus obtained are soluble in DMSO, dimethylformamide (DMF), and alcohols.
Characterization of the cure of TGDDM/DDS epoxy resins by chemiluminescence I. Spectral and thermal analysis
Authors: George G. A. , Schweinsberg D. P. 
Published: April 2003

AbstractThe emission of weak visible chemiluminescence (CL) during the cure of a tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM)‐based epoxy resin, with three different concentrations of 4,4′‐diaminodiphenylsulfone (DDS) has been studied at 135°C. Spectral analysis indicates that the CL originates from trace oxidation of the TGDDM resin and the emission intensity is sensitive to the viscosity changes during cure. From thermal analysis data, sharp discontinuities in CL intensity are shown to occur at the gel point. The temperature dependence of CL from a cured resin also shows a sharp discontinuity at Tg. These results indicate that CL provides a sensitive monitor of both the kinetics of gelation and the network formation in this epoxy resin.
Dielectric properties of an epoxy resin and its composite II. Solvent effects on dipole relaxation
Authors: Reid Jonathan D. , Buck Richard P. 
Published: April 2003

AbstractDipole relaxation dielectric loss behavior of a fiberglass‐epoxy composite has been studied following submersion in polar and nonpolar organic solvents as well as in acidic and basic aqueous solutions. Certain adsorbed organic solvents, such as 1,2‐dichloroethane, had little influence on the epoxy relaxation behavior. Other solvents, including chloroform, increased the composite relaxation intensity and shifted the temperature‐frequency region over which the relaxation occurred. Both the amount of solvent uptake and the degree of interaction of solvent molecules with epoxy polar functional groups appear to control the amount of relaxation behavior perturbation. Arrhenius activation energies for relaxation were lowered by solvent uptake from the dry composite value of 18 kcal/M to between 6 and 16 kcal/M, depending on the solvent adsorbed. Submersion in methanol and chloroform sharply increased the direct current conductivity of the composite. Two molar acidic and basic solutions had little influence on composite dipole relaxation behavior other than the well known behavior associated with moisture uptake.
Selective separation of water from water–ethanol solution through quarternized poly(4‐vinylpyridine‐co‐acrylonitrile) membranes by pervaporation technique
Authors: Yoshikawa Masakazu , Yukoshi Takashi , Sanui Kohei , Ogata Naoya 
Published: April 2003

AbstractPolymer membranes having cationic charge site, poly(1‐alkyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (alkyl: methyl, butyl, or octyl) were prepared in terms of coulombic interaction for separation of water–ethanol mixtures. The incorporation of cationic charge site into the membrane led to improve not only separation factors (selectivity toward water) but also flux number in the separation of aqueous ethanol solution by pervaporation technique. Target values, which were requested to have from the viewpoint of industrial utilization for separation of aqueous ethanol solution were attained as follows: separation factor toward water over 50 and flux value over 500 g m−2 h−1, through poly(1‐methyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (membrane 3) (quarternized fraction of pyridinium moiety, 89.5%; mol fraction of pyridinium moiety, 0.034) and poly(1‐butyl‐4‐vinylpyridinium iodide‐co‐acrylonitrile) (membrane 5) (quarternized fraction, 100%; mol fraction of pyridinium moiety, 0.038). It was found that the introduction of cationic charge site into the membrane was one of feasible methods to obtain suitable membranes for water permselective membranes in the separation of water–ethanol mixtures.
Rates of property change in plasticized filled PVC compounds
Authors: Ajji A. , Schreiber H. P. , Rudin Alfred 
Published: April 2003

AbstractRheological and mechanical properties of polyvinyl chloride (PVC) compounds vary with the polymer entanglement state at the time of testing. Controlled shearing episodes and thermal histories applied to the compounds produce major property variations. These then relax toward steady‐state values at rates which are consistent with diffusion‐controlled processes, presumably connected with the development of steady‐states in entanglement couplings. Activation energies of 4–7 kcal/mol apply to the proposed re‐entanglement processes. Rates of property variation can be altered by the addition of fillers to the compounds, the interactions between polymer and filler being an important factor in this regard. CaCO3 samples with strong affinity for the PVC retard the rate of property variations (i.e., the filler tends to stabilize non‐steady‐state entanglement couplings). Fillers, surface treated so as not to interact strongly with the polymer, produce lesser effects on relaxation rates. The data indicate the feasibility of controlling both the sensitivity of polymer properties to processing variables, and the rates of property change associated with the attainment of steady‐state polymer entanglement morphologies.
The application of bulk polymerized acrylic and methacrylic interpenetrating polymer networks to noise and vibration damping
Authors: Foster J. N. , Sperling L. H. , Thomas D. A. 
Published: April 2003

AbstractNovel acrylic/methacrylic interpenetrating polymer networks (IPNs) were examined by dynamic mechanical spectroscopy for their damping capabilities. While simple homopolymers exhibit high damping properties only over a 20–30°C range, multicomponent polymer systems with controlled degree of miscibility, such as IPNs, may exhibit high damping properties over temperature ranges as broad as approximately 100°C. Two series of IPNs based on poly(n‐butyl acrylate) and poly(n‐butyl methacrylate) were synthesized and the dynamic mechanical properties were investigated using a Rheovibron. Graphite was incorporated into the poly(n‐butyl acrylate) homopolymer and a few IPNs to measure the change in the damping properties. For important IPN compositions, tan δ values between 0.4 and 0.85 were observed over a 75°C plus temperature range. Graphite increased the damping properties of poly(n‐butyl acrylate) and the IPNs, as indicated by the tan δ values.
Concentration dependence of solvent self‐diffusion coefficients
Authors: Vrentas J. S. , Chu C.‐H. 
Published: April 2003

AbstractThe concentration dependence of solvent self‐diffusion coefficients is examined near the pure solvent limit. It is shown that it is possible to explain an apparently anomalous concentration dependence for the solvent self‐diffusion coefficient at high penetrant mass fractions within the framework of the free‐volume theory of transport.
The effect of thermal history on the distribution of residual stresses in PMMA rods
Authors: Mittal Ramesh K. , Rashmi Vibhu 
Published: April 2003

AbstractA nondestructive technique based on the photoelastic properties of transparent polymers has been used to monitor the distribution of residual stress components in circular rods of poly(methyl methacrylate) (PMMA). The influence of various thermal histories on these stresses as well as on the molecular birefringence has been determined. The technique has been further simplified to obtain the values of maximum tensile and compressive residual stresses with the help of just two photoelastic measurements. The stresses so obtained are within 10% of the values obtained using detailed experimental measurements and their analysis. The simplified procedure is, therefore, suitable for “on‐line” determination of residual stresses in extrusion industry.
The effect of sorbed penetrants on the aging of previously dilated glassy polymer powders. I. Lower alcohol and water sorption in poly(methyl methacrylate)
Authors: Connelly R. W. , McCoy N. R. , Koros W. J. , Hopfenberg H. B. , Stewart M. E. 
Published: April 2003

AbstractSorption kinetics and equilibria for methanol, ethanol, and n‐propanol in 0.544 μm diameter poly(methyl methacrylate) microspheres were determined at 35°C over a wide range of relative pressures. Sorption isotherms were concave to the pressure axis at low relative pressures and convex to the pressure axis at higher relative pressures. These results, considered in the context of recently reported data for high pressure sorption of gases in polymeric glasses, suggest that the S‐shaped isotherms reported here are examples of a generalized isotherm which describes sorption behavior of all penetrants in glassy polymers if an appropriate range of concentration is traversed by the experimental protocol. The effects of dialating the microspheres by preswelling with methanol were studied by subsequent low pressure sorption of water, methanol, ethanol, and n‐propanol at 35°C. The preswollen microspheres exhibited initially higher sorption capacities than the as‐Received samples, but tended to consolidate with time following the preswelling treatment. The aging process, monitored by periodic short‐term sorption with the various penetrant probes, was arrested by contacting the microspheres with an activity of n‐propanol sufficient to maintain a sorbed concentration of approximately 1 wt %. The aging was significantly retarded by the presence of low concentrations of water and ethanol. Conversely, the aging process appeared to be essentially unaffected by the presence of correspondingly low concentrations of methanol. The complex kinetics describing the sorption of the various penetrants ranged from Fickian diffusion to polymer relaxation‐controlled absorption, depending upon penetrant, relative pressure, and prior exposure history. The low temperature preswelling of the microspheres markedly increased the rate of sorption as well as the respective apparent equilibrium sorption.
Residual stress and thermal expansion of spun‐on polyimide films
Authors: Elsner Gerhard 
Published: April 2003

AbstractThe residual stress in spin coated films and the effect of heat treatments on this stress were determined by the Fizeau interference method. Three types of spin coated polyimide (PI) films have been studied. Two of them were prepared by thermal conversion of their poly(amic acid)s (PAAs) and the third one by solvent evaporation of the soluble preimidized PI. For the imidized PI films the residual stress vs. bake temperature shows an inclined steplike behavior while this function for soluble PI is approximately linear. The room temperature stress relative to silicon substrates in fully baked films (400°C) is between 40 and 70 MPa and nearly independent of the film thickness. From the stress measurement, the thermal expansion coefficient and Young's moduli have also been obtained. The thermal expansion coefficient and the Young's modulus are in the order of 9.0 × 10−6°C−1 and 10 GPa, respectively. These values deviate from those published for bulk material which is explained by the in‐plane orientation of the molecular chains in spun‐on PI films.