bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acoustic relaxation and infrared spectroscopic measurements of the plasticization of poly(methyl methacrylate) by water
Authors: Gilbert A. S. , Pethrick R. A. , Phillips D. W. 
Published: April 2003

AbstractMeasurements are reported on the acoustic attenuation and velocity of dry and wet samples of poly(methyl methacrylate) over a temperature range of 5° to 70°C and over a frequency range of 5 to 35 MHz. Lowering of the glass transition temperature with increase in water content was reflected in an increase in the acoustic attenuation and a lowering of the velocity at high temperature. Comparison of the infrared spectra of wet and dry thin films indicates that water exhibits spectroscopic characteristics of isolated rather than highly clustered molecules. A study of the temperature dependence of the diffusion coefficient of water into the polymer matrix provided an activation energy for the migration process. The data suggest that water plasticizes poly(methyl methacrylate) via specific local interactions with the backbone.
The determination of moisture transitions in cellulosic materials using differential scanning calorimetry
Authors: Nelson Robert A. 
Published: April 2003

AbstractThe association of water with cellulose is of significant technological importance. It forms the basis for the manufacturability of paper and ultimately controls, either directly or indirectly, mechanical, electrical, thermal, and optical properties. Differential scanning calorimetry has been used to characterize moisture transitions in these materials. Total bound water contents have been determined. Specific transitions for the model system, cotton linters, have been identified including free water incorporation point (0.05 g/g), total bound water (0.18 g/g), and fiber saturation point (0.05 g/g). Results are compared to those found in a pulsed nuclear magnetic resonance study in which a moisture distribution model was generated; free water point (0.046 g/g) and total bound water (0.19 g/g). The differential scanning calorimetry technique can provide a more readily available, less expensive, and simpler technique for paper/cellulose characterization and study.
Studies in the molecular weight distribution of epoxide resins. IV. Molecular weight distributions of epoxide resins made from bisphenol a and epichlorohydrin
Authors: Batzer H. , Zahir S. A. 
Published: April 2003

AbstractThe molecular weight distribution of epoxide resins made from bisphenol A and epichlorohydrin at high ratios of epichlorohydrin to bisphenol A are compared with the theoretically predicted distributions for two theoretical models: the “taffy” process A, the direct reaction of epichlorohydrin with bisphenol A; and the “taffy” process B, the self‐polymerization of a monoglycidyl ether of bisphenol A followed by postglycidylation. At high ratios of epichlorohydrin to bisphenol A, process B is shown to give more low molecular weight products than process A. Deviations of the experimentally measured distributions from the theoretically predicted distributions for high epichlorohydrin/bisphenol ratios are attributed to the higher reactivity of epichlorohydrin to the phenolic compared with the aryl glycidyl ether functional group. Preliminary kinetic data are presented using a modified gel chromatographic method which enables the separation of most of the intermediates formed in this reaction.
Porosity and pore size determination in polysulfone hollow fibers
Authors: Cabasso I. , Robert K. Q. , Klein E. , Smith J. K. 
Published: April 2003

AbstractAverage pore sizes and effective porosity of microporous polysulfone hollow fibers were determined by the gas permeability method. Surface structure and porosity were determined by scanning electron microscopy. The values of effective porosity ε/q2 (porosity/tortuosity factor) are approximately one order of magnitude lower than those reported previously for flat sheet porous membrane. These lower values are a direct outcome of a higher polymer concentration in the spinning dope. Correlations between the wall void volume, equivalent pore size, and hydraulic permeabilities of the hollow fibers have been determined. Rather low values of ε/q2 have been calculated compared to those of the void volume; these effective porosity values indicate either a very high tortuosity factor or a large number of “dead end” pores. Exposure of the fibers to elevated temperature (110°C) for a short period of time drastically reduces the surface pore size and narrows the pore size distributions, whereas overall fiber dimensions are reduced only by 1%, and 85% of the fiber's hydraulic permeability is retained. The scanning electron microscopy study reveals the formation of a relatively dense skin in some spun fibers. For such “skinned” fibers, kinetic (permeability) evaluation of static structure such as mean pore size is not realistic and is further generalized to the term “equivalent pore size.”
Stabilization of poly(vinyl chloride). III. Synergism between metal soaps and masking agents on the stabilization of poly(vinyl chloride)
Authors: Iida Takeo , Kataoka Nobukazu , Ueki Norihito , Gotō Kunio 
Published: April 2003

AbstractThe stabilization mechanism by synergetic metal soaps containing complementary colors was previously reported. With increased heating times, the color of heated poly(vinyl chloride) (PVC) films containing Cd/Ba and Zn/Ca synergetic soaps markedly deviated from the polyene color. These color deviations usually decreased the thermal stability of PVC. Discoloration from polyene color to blue appeared especially on PVC films containing Zn/Ca synergetic soap and was concomitant with a marked decrease in thermal stability. The stabilization of PVC containing synergetic metal soaps can be improved by masking or removing the excessive color. In this work, the addition of various masking agents, such as ethylenediaminetetraacetic acid, o‐phenanthroline, triethanolamine, urea, N,N′ ‐dimethylolurea, melamine, stearylamide, and lactams, to PVC containing synergetic metal soaps was investigated. It was shown that these masking agents do markedly slow down the discoloration of PVC.
Domain structure and time‐dependent properties of a crosslinked urethane elastomer
Authors: Lagasse R. R. 
Published: April 2003

AbstractThe morphology of a chemically crosslinked urethane elastomer is correlated with its time‐dependent mechanical properties. Evaluation of this amorphous elastomer by electron microscopy and small‐angle x‐ray scattering reveals that incompatible chain segments cluster into separate microphases having a periodicity in electron density of about 90 Å. This observed domain structure is similar to that seen previously in uncrosslinked, thermoplastic urethane elastomers. As in earlier studies on such linear system, thermal pretreatment of the crosslinked elastomer causes a time‐dependent change in its room temperature modulus. However, the magnitude of this modulus change (about 20%) is generally less than observed previously with the linear systems. Another contrast with previous findings is that this time‐dependent phenomenon is apparently not caused by thermally activated changes in microphase segregation. Rather, the observed time dependence in modulus is believed to be caused by molecular relaxation resulting in densification of amorphous packing within the hard‐segment domains. The validity of this proposed mechanism is supported by differential scanning calorimetry experiments showing evidence of enthalpy relaxation during room‐temperature aging of the elastomer. This relaxation is qualitatively similar to that observed previously during sub‐Tg annealing of single‐phase glassy polymers.
Crosslinking and mechanical property of liquid rubber. I. Curative effect of aliphatic diols
Authors: Minoura Yuji , Yamashita Shinzo , Okamoto Hiroshi , Matsuo Tadao , Izawa Michiaki , Kohmoto Shun‐Ich , Minoura Yuji , Yamashita Shinzo , Okamoto Hiroshi , Matsuo Tadao , Izawa Michiaki , Kohmoto Shun‐Ich 
Published: April 2003

AbstractThe structure–property relationships of polyurethane elastomer derived from liquid hydroxylterminated polybutadiene/low molecular weight aliphatic diol/diisocyanate system were studied. The effects of the amount of low molecular weight diol on the mechanical properties of elastomer were discussed on the basis of the results of the stress–strain curve, swelling, dynamic viscoelasticity, x‐ray diffraction, and others. It was found that some particular combinations of low molecular weight diol and diisocyanate specifically affect the properties of elastomers. When the mechanical properties of the elastomers were plotted against the number of methylene carbons in low molecular weight diol, the characteristic zigzag patterns were obtained. These patterns were explained by the difference in the packing and the dependence of the ability of intermolecular hydrogen bonding on whether the number of the methylene carbons was even or odd. This assumption was confirmed by x‐ray diffraction.
The effect of short air exposure periods on the performance of cellulose acetate membranes from casting solutions with high cellulose acetate content
Authors: Sirkar Kamalesh K. , Agarwal Nirmal K. , Rangaiah Gade Pandu 
Published: April 2003

AbstractHighly productive cellulose acetate membranes were cast under conditions of very short air exposure periods from cellulose acetate–acetone–formamide casting solutions having a high cellulose acetate (CA) content and lying close to the phase boundary. Air exposure periods as short as 0.05 sec were used with CA content up to 32 wt‐%. Membranes from a casting solution containing 30 wt‐% cellulose acetate (E‐398‐3), 45 wt‐% acetone, and 25 wt‐% formamide perform as well as membranes from other compositions at all salt rejection levels for a 0.5 wt‐% NaCl feed at 600 psig. Partial replacement of acetone by dioxane in the casting solution substantially increases the water flux from membranes cast with short air exposure periods at any given salt rejection level below 96% salt rejection. Addition of small amounts of ZnCl2 to nondioxane casting solutions with 32 wt‐% CA improves membrane performances remarkably for lower salt rejection levels, while the improvement in performance of membranes from 30 wt‐% CA casting solutions with dioxane due to ZnCl2 addition is marginal. Variation in air exposure from 0.05 to 2 sec results in minor performance variations in the membranes having any of these compositions. With air exposure periods beyond 2–3 sec, membrane fluxes drop drastically. The concept of a thinner skin satisfactorily explains the improvement in mixed solvent systems, whereas ZnCl2 acts as a swelling salt. A Kimura‐Sourirajan‐type membrane performance plot indicates that for a 0.5 wt‐% NaCl feed at 600 psig, membranes of the present work perform as well as the best performing membranes reported in the literature for conversion of brackish water.
Graft polymerization on magnetic polymer substrates
Authors: Bolto B. A. , Dixon D. R. , Eldridge R. J. 
Published: April 2003

AbstractFunctional monomers were graft polymerized onto substrates consisting of magnetic iron oxides in a crosslinked PVA matrix. Initiation was carried out with H2O2 and FeSO4; other common chemical initiating systems proved unsuccessful. Peroxide treatment of the substrates must be carried out separately from the reaction with Fe2+ and monomer. The amount of grafting achieved is highly variable, depending on the nature of the monomer. Strong base and weak acid magnetic shell resins prepared by graft polymerization are useful in water treatment by flocculation and moving‐bed ion exchange, respectively. A wider range of products can be obtained by chemical modification of grafted chains. The mechanism of grafting is discussed in an endeavor to explain the highly specific nature of the reaction.
The photodegradation of polypropylene. IV. UV stabilizer decomposition
Authors: Carlsson D. J. , Grattan D. W. , Suprunchuk T. , Wiles D. M. 
Published: April 2003

AbstractThe destruction of various UV stabilizers in polypropylene films during irradiation has been examined both in the presence and absence of air and oxidation products. Although some stabilizers were destroyed in the absence of oxygen, all were more sensitive when irradiated in the presence of air. Several stabilizers were highly effective but were destroyed so rapidly that photoprotection of the polymer must have resulted from stabilizer products. Work with preoxidized polymer and with model hydroperoxides and peroxides indicated that most stabilizers were destroyed by the attack of oxygen‐centered radicals, with peroxy radical attack appearing to dominate.
The permeation behavior of metal complex solutions through cellulose acetate membranes
Authors: Kamizawa Chiyoshi 
Published: April 2003

AbstractTransport phenomena of several kinds of metal complexes were investigated with cellulose acetate membranes annealed at 65°–76°C. In reverse osmosis experiments, the rejections of metal complexes involving organic sequestering agents such as EDTA or citric acid were much higher than those of the corresponding metal ions. While, in the case of metal complexes involving small inorganic ligands such as NH3or SCN‐, their rejections did not necessarily increase with the increase in the coordination numbers of the metal ions. To more precisely understand such transport behaviors, the distribution and the diffusion coefficients of metal complexes were obtained by desorption‐rate measurements with dense cellulose acetate membranes. The results revealed that the distribution of a metal ion to the membrane was largely depended on the coexisting ligands. Attempts were also made to explain the distribution coefficient from the microscopic point of view by using Glueckauf's equation.
Partially dehydrochlorinated PVC. I. Structure
Authors: Wirsén Anders , Flodin Per 
Published: April 2003

AbstractPVC made by suspension and anionic polymerization was partially dehydrochlorinated by three different methods. In the first one, a solution in THF and in the second one, particles swollen by dioxane were treated with alcoholic KOH at low temperatures. In the third method, a solution of PVC in DMF was heated to 130°C or refluxed (153°C). The reactions were followed by UV spectrophotometry and the products analyzed by GPC. Furthermore, the products were ozonolyzed and the molecular weights of the polymeric residues determined by GPC. Treatment with KOH in THF yielded products with randomly distributed polyene sequences. At higher degrees of dehydrochlorination a slight decrease in molecular weight was observed. The polymers were shown to be built up by PVC segments with an average degree of polymerization between 70 and 80, interspaced by polyene segments each with relatively few conjugated double bonds in sequence (fewer than 15). The reaction of KOH with particles swollen in dioxane was slower but yielded products with the same molecular structure. Thermal dehydrochlorination in DMF gave rise to long polyene sequences. They were fewer in number as evidenced by the higher molecular weights of the residues after ozonolysis.
Thermal shrinkage of drawn polystyrene
Authors: Ito Eiko , Horie Takashi , Kobayashi Yasuji 
Published: April 2003

AbstractMany papers have reported on the thermal shrinkage mechanism of drawn polymers. The cause of the thermal shrinkage is very complex, because that relates to many factors. In this study, atactic polystyrene, a noncrystalline polymer, was used to eliminate factors related to the melting and crystallization effects, and it is considered that there is a relation between the change of the polymer's structure due to heat treatment and thermal shrinkage. It is observed in a certain temperature range that the thermal shrinkage of drawn polystyrene is not caused by increase of the entropy but results in decrease of the entropy.
Crystalline transitions and the solid‐state extrusion of polymers
Authors: Aharoni S. M. , Sibilia J. P. 
Published: April 2003

AbstractExtrusion experiments on eight polymers in our laboratory and eight additional polymers in other laboratories reveal that solid‐state extrusion and malleability occur in semicrystalline polymers that have a reversible crystalline transition, Tc, and do not occur in crystalline polymers devoid of Tc, The solid‐state extrusion takes place only in the temperature range of Tc ≪ T < Tm. The transparency of the solid‐state extrudates was shown to be largely due to void disappearance and may be due in part to the diminution in size of the scattering species. Increases in Tm were shown not to be correlatable with lamellar thickening or chain extension.
Polyester–Polycarbonate blends. IV. Poly(ε‐caprolactone)
Authors: Cruz C. A. , Paul D. R. , Barlow J. W. 
Published: April 2003

AbstractPolycarbonate blends with poly(ε‐caprolactone) were prepared by both melt‐blending and solution‐blending techniques, and the properties of these blends were studied by thermal analytical and dynamic mechanical testing methods. Each blend composition was found to have a single glass transition temperature, and the temperature location of this transition was found to be a function only of blend composition and to be independent of the blending technique employed. This behavior led to the conclusions that these two polymers form blends containing a single amorphous phase comprised of the two materials and that this miscible phase results primarily from physical rather than chemical interactions between the two polymers. A reversible liquid‐liquid‐type phase separation was found to occur when the blend system was heated to high melt temperatures. The temperature required for phase separation, the lower critical solution temperature, was found to vary with blend composition and component molecular weight in the manner expected from thermodynamic considerations. The level of crystallinity of poly(ε‐caprolactone) was affected by the presence of the polycarbonate. The polycarbonate also crystallized to an appreciable extent in many of the blends.
Grafting vinyl monomers onto silk fibers. II. Graft copolymerization of methyl methacrylate onto silk by hexavalent chromium ion
Authors: Nayak Padma L. , Lenka Subasini , Pati Nrusingha C. 
Published: April 2003

AbstractThe feasibility of chromium(VI) to induce graft polymerization of methyl methacrylate onto silk was investigated. The rate of grafting was determined by varying monomer concentration, chromium(VI) concentration, temperature, acidity of the medium, nature of the silk, reaction medium, and redox system. The graft yield increased with increasing monomer concentration up to 0.65M, and with further increase of monomer the graft yield decreased. The graft yield increased with increasing chromium(VI) concentration. The grafting is considerably influenced by chemical modification of silk prior to grafting. The graft yield is influenced by thiourea concentration, decreasing with increasing thiourea concentration. The effect of certain inorganic salts and anionic surfactants on the rate of grafting was investigated.
Solution and rheological properties of poly(m‐phenyleneisophthalamide) in dimethylacetamide/LiCl
Authors: Harwood Daniel , Aoki Hiroshi , Lee Yu‐Der , Fellers John F. , White James L. 
Published: April 2003

AbstractAn experimental study of the solution properties of poly(m‐phenyleneisophthalamide) (MPD‐I) in dimethylacetamide (DMA)/LiCl solutions is presented. Differential refractometry, light scattering photometry, dilute and concentrated solution viscometry, and normal stress experiments are reported and interpreted. This polymer in the concentration range investigated does not exhibit mesophase behavior in contrast to its para‐linked analog. Generally, it behaves as a flexible polymer molecule; however, its capacity to become a polyelectrolyte strongly influences its behavior in the presence of LiCl. MPD‐I is self‐associated when dissolved in pure DMA but dissociates in DMA/LiCl solvent systems. The Zimm plots of MPD‐I in DMA/LiCl solutions show distortion, probably due to polymer–salt interactions.
Hydrostatic extrusion under back pressure of high‐density polyethylene
Authors: Nakayama Kazuo , Kanetsuna Hisaaki 
Published: April 2003

AbstractThe possibility of hydrostatic extrusion of solid polymer under back pressure has been studied. Operation of equipment is described that permits hydrostatic extrusion under back pressure at elevated temperatures. To understand how the pressure influences hydrostatic extrusion, extrusions of polyethylene under back pressure up to 392 MPa were conducted at temperatures below the melting point of polyethylene at atmospheric pressure (Tm1). Furthermore, hydrostatic extrusion in the solid phase could be conducted at temperatures beyond Tm1, since the melting point of polyethylene increased markedly with increasing back pressure.
Experimental confirmation of extent of reaction at the gel point in a polyisocyanurate
Authors: Alberino Louis M. 
Published: April 2003

AbstractTheoretical equations were developed to relate the extent of reaction at the gel point for a system where three functional groups trimerize to a ring structure during the polymerization reaction. Specific relationships were developed for a difunctional monomer where the two functional groups are of unequal reactivity and for a mixture of difunctional monomer where the two functional groups are of unequal reactivity and for a mixture of difunctional and monofunctional monomer where all three functional groups are of unequal reactivity. These two cases were tested experimentally by determining the extent of reaction at the gel point for the system isocyanate reacting to form isocyanurate. In the case of 4,4′‐diisocyanatophenylmethane (MDI), the extent of reaction at gelation was determined experimentally to be 60%. When this data was analyzed according to the theory developed, a reactivity ratio of 2.38 was calculated for the rate of the first isocyanate group to react as compared to the second. Experiments were also performed with 2,4‐toluene diisocyante, which gave a 72% conversion at the gel point. The extents of reaction at the gel point for mixtures of MDI and phenyl isocyanate were also determined experimentally. An analysis according to the theory developed further supported the idea that all three isocyanate groups in this system have different reactivities. Theoretical relationships also were developed for a trifunctional isocyanate reacting to form isocyanurate. Experimentally, a crude MDI was used, and approximate relationships were used to analyze the results.
Loss of additives from polymers: A theoretical model
Authors: Calvert P. D. , Billingham N. C. 
Published: April 2003

AbstractThe rate at which an additive is lost from the surface of its solution in a polymer is considered to depend upon three factors—the solubility of the additive, the rate at which it volatilizes from the polymer surface, and its diffusion coefficient within the bulk of the polymer. By adapting the mathematics of heat flow in a solid, the loss of additive from a polymer is mathematically modeled in terms of these three variables for bulk polymer and for film and fiber samples. Two cases are considered—loss of additive by volatilization or dissolution from the polymer surface and loss by precipitation on the surface from a supersaturated solution of the additive. The results are applied to a discussion of the relative importance of the three parameters under various conditions occurring or expected in practical application of additives as oxidation stabilizers for polyethylene and polypropylene.
Methods for lowering loss angle tangent of thin polystyrene films obtained by electrical discharge in styrene vapor
Authors: Sar C. , Valentin M. , Ai Bui 
Published: April 2003

AbstractThe thin films of polystyrene obtained in an electrical discharge present a value of tan δ higher than that of traditional polystyrene films. It appears that oxygen is one of the factors bringing on this failure. A noticeable improvement of loss factor can be obtained either by addition of antioxydant or by reducing the electrodes spacing.