bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

The 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

The 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

Highly 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

Functional 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

The 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

Transport 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

PVC 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

Many 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

Extrusion 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

Polycarbonate 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

The 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

An 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

The 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

Theoretical 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

The 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

The 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.
Reversible plasticization of nylons 6 and 11 with anhydrous ammonia and their deformation by solid‐state coextrusion
Authors: Zachariades Anagnostis E. , Porter Roger S.
Published: April 2003

Reversible plasticization of nylons with anhydrous ammonia is a new concept. In the present studies, nylons 6 and 11 have been plasticized with anhydrous ammonia and subsequently were solid‐state coextruded below the melting point. The plasticization is attained by a temporary disruption of the strong hydrogen bonding between amide groups of adjacent nylon chains. Thermogravimetric and infrared analysis show that for the nylons 6 and 11 the amount of ammonia absorbed is 18% and 10% of the weight of the dry samples, respectively. The ammonia incorporation to preformed nylon ribbons prior to extrusion alleviated significantly the processing difficulties encountered with untreated nylons and aided the rapid extrusion of highly oriented states (EDR 12). The extent of orientation is documented by the high total birefringence values (8.25 × 10−2 for nylon 6 and 5.8 × 10−2 for nylon 11), by the significant increase in crystallinity (23.5%–53% for nylon 6 and 25.7%–40% for nylon 11), and by the enhanced tensile moduli (13 GPa for nylon 6 and 4 GPa for nylon 11).
Block copolymers obtained by free‐radical mechanism. I. Methyl methacrylate and styrene
Authors: Piirma Irja , Chou Lee‐Pei H.
Published: April 2003

Block copolymers were synthesized using styrene and methyl methacrylate as the monomers and a multifunctional initiator, di‐t‐butyl 4,4′‐azobis(4‐cyanoperoxyvalerate). The unique feature of this sequential initiator is the fact that the formation of the free radicals can be achieved thermally and/or by a redox system at different stages. The polymerizations for the formation of the block copolymer were carried out in two stages. First, a polymeric initiator was synthesized, which was then used in the second stage to initiate the polymerization of the second monomer. Styrene and methyl methacrylate were used as the comonomers. Selective solvent fractionation was used for the separation of the block from the homopolymers. The separation technique was found to be efficient, giving pure block copolymers which could subsequently be characterized by GPC, NMR, IR, and EM techniques.
Release rate characteristics of microencapsulated 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine
Authors: Noren G. K. , Korpi G. K. , England G. J.
Published: April 2003

The rate at which 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine (TMP) is released from a microcapsular controlled delivery device was determined using aqueous methanol as an extraction medium. The microcapsules were prepared by in situ polymerization of a urea–formaldehyde resin. Release rate studies demonstrated that the amount of 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine released is proportional to t−1/2 and the solubility of 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine in the extraction medium. These relationships are characteristic of a porous, monolithic delivery system.
Copolyester studies. V. Preparation and characterization of tetramethylene terephthalate–poly(tetramethylene oxide) random block copolymers
Authors: Boussias C. M. , Peters R. H. , Still R. H.
Published: April 2003

Random block copolymers of tetramethylene terephthalate and polytetrahydrofuran (PTHF) were prepared by melt polycondensation. Five different molecular weights of PTHF were used in the polymerizations with up to 30% by weight incorporation. The copolymers so obtained were characterized in terms of their molecular weight by means of endgroup analysis and solution viscometry. Compositions were established by nuclear magnetic resonance spectroscopy. Thermal properties were studied by differential scanning calorimetry and dynamic mechanical methods. Melting and glass transition temperatures are discussed in terms of the structural differences, particularly the effect of polyether composition and block size on chain flexibility.
Stabilization of poly(vinyl chloride). V. Synergism between metal soaps and polyols upon stabilization of poly(vinyl chloride)
Authors: Iida Takeo , Gotō Kunio
Published: April 2003

The marked discolorations observed on aged poly(vinyl chloride) (PVC) containing synergetic metal soaps, in the early heating stage, were due to the excessive coloration of π complex of metal chloride and double bonds in the polyene chain. These excessive colorations were inhibited by masking the excessive metal chloride with some masking agents, thereby slowing down the abrupt discoloration of PVC. In this paper, the masking effect of various alcohols such as 1,2‐butanediol, 1,3‐butanediol, 1,4‐butanediol, 2,3‐butanediol, hexylene glycol, glycerol, 1,2,4‐butanetriol, trimethylolethane, trimethylolpropane, meso‐erythritol, pentaerythritol, sorbitol, and dipentaerythritol is investigated. The polyhydric alcohols, except dihydric alcohols, showed superior masking effect and markedly improved the thermal stabilization effects of synergetic metal soaps. The mechanism for the synergetic effects between polyols and metal soaps should be based on the masking effect of polyols, owing to the formation of the colorless complex of polyols with excess metal chlorides obtained from the metal soap.
Hydrophilic behavior of HSPAN/PVA membrane
Authors: Turner John E. , Shen Mitchel , Lin Chen‐Chong
Published: April 2003

The hydrophilic behavior including water absorption, swelling, and dielectric spectrum of pure HSPAN as well as HSPAN/PVA blends are investigated. The HSPAN/PVA membranes still absorb a considerable amount of water. The effect of water upon mechanical properties is also investigated for these membranes. Formalization of membrane enhances mechanical properties and reduces weight losses during swelling with much loss in the water absorption ability of PVA. This kind of blend shows promise as material for hydrophilic membranes.
Characterization of a new composite material: Fe2O3‐impregnated poly(tetrafluorethylene). Particle size determination and photoacoustic spectroscopy
Authors: Galembeck F. , Ghizoni C. C. , Ribeiro C. A. , Vargas H. , Miranda L. C. M.
Published: April 2003

Iron carbonyl sorption in PTFE, followed by in situ oxidation, gives the composite material, iron oxide–PTFE. Oxide particle size determination was performed by electron microscopy. The particles were found to be nearly spherical and very small, having diameters in the 30–40 Å range on average. Optical absorption spectra were obtained by photoacoustic spectroscopy, and their intensities show a complex dependence on iron oxide concentration in the samples.
Study on the graft copolymerization of lignosulfonate and acrylic monomers
Authors: Chen R. , Kokta B. V. , Valade J. L.
Published: April 2003

Graftings of acrylonitrile and methyl methacrylate onto lignosulfonate were studied, respectively, with and without the lignosulfonate ozonized. Copolymerization was redox‐initiated by peroxideferrous ions. Monomer conversion and grafting efficiency depended essentially on reaction medium and the maount of peroxide charged. Among the media employed, the magnitude of the medium effect on conversion was found to be in the following order: water, dioxane, and methanol. The conversions in water of acrylonitrile and methyl methacrylate were 55 and 90%, respectively, when using 3% hydrogen peroxide. Beyond this 3 % charge, both the grafting efficiency and the degree of lignosulfonate grafted approached certain limits. Ozonization appeared to be capable of stimulating the active centers in lignin macromolecules, whereon acrylic monomers could be grafted. Better grafting efficiency was obtained with the ozonized lignosulfonate.
Metal acetylacetonates as latent accelerators for anhydridehyphen;cured epoxy resins
Authors: Smith J. D. B.
Published: April 2003

Twenty‐two metal acetylacetonate compounds have been evaluated as possible latent accelerators for epoxy‐anhydride solventless resins. Experimental data have revealed that titanium (IV) oxyacetylacetonate, chromium (III), zirconium (IV), cobalt (III), and cobalt (II) acetylacetonates are particularly effective with anhydride cured epoxy resins. When added to the resin at a level of 0.05–0.10% (w/w), they provide very fast gel times at 150–175°C combined with very good storage stabilities (> six months) at room temperature. The power factor values of cured resin samples, containing these preferred metal acetylacetonates, have been found to be between 2.0 and 2.5% at 150°C and 60 Hz. Correlation between the catalytic effectiveness of these metal acetylacetonates, as latent accelerators for epoxy‐anhydride resins, and their thermal stabilities suggest that decomposition products may be the active species responsible for initiating polymerization in epoxyanhydride resin systems.
Prediction of rheological behavior of branched polyethylene from molecular structure
Authors: Bersted B. H. , Slee J. D. , Richter C. A.
Published: April 2003

The general description of steady shear melt viscosity as a function of shear rate for polyethylene, containing any level of long chain branching, in terms of molecular structure is reported. A model, developed previously by B. H. Bersted for the prediction of rheological properties from the molecular structure of linear materials, and which has been subsequently modified by Ram and Pedersen for application to highly branched low‐density polyethylene, is extended to describe the flow behavior of branched high‐density polyethylene. The description of the branched high‐density polyethylenes, which characteristically show dramatic viscosity enhancement relative to linear polyethylene, is effected by considering these materials to be blends of branched and linear species. A logarithmic rule of mixtures was found adequate at all shear rates for the description of blends of branched and linear materials.
Effect of concentration and second polymer on elution volumes in gel permeation chromatography
Authors: Narasimhan V. , Huang R. Y. M. , Burns C. M.
Published: April 2003

Shifts have been observed in the elution volumes of solutions of polystyrene, polybutadiene, and mixtures of the two in gel permeation chromatography using tetrahydrofuran as solvent. Such shifts are examined in terms of the effect on the hydrodynamic volumes of concentration, of molecular weight, and of the presence of an incompatible polymer. Suitable concentration ranges to minimize these shifts have been found.
Push–pull extrusion: A new approach for the solid‐state deformation illustrated with high density polyethylene
Authors: Shimada Toshio , Zachariades Anagnostis E. , Watts Michael P. C. , Porter Roger S.
Published: April 2003

The crystalline state deformation of high density polyethylene has been examined at an extrusion draw ratio of 30 over a range of temperatures and pressures. The experiments involve combined pushing (extrusion) and pulling through a conical die. The pressure dependence of the extrusion rate through conical dies is given by a logarithmic relation and the temperature dependence by an activation energy of ∼95 kcal/mole. An equation established for the total applied force linearly relates the pulling and extrusion pressure components and represents a force balance at the die entrance and exit. Steady‐state extrusion, with or without pulling, was feasible in a pressure range beyond which fractures occurred owing to strain rate and shear or tensile failure. Under some circumstances the extrusion rate was increased by ten times. The mechanical properties and mode of deformation were not affected by pull load and fibers with a tensile modulus of 55 GPa were produced at T < 110°C.
Emulsion polymerization of styrene with ionic comonomer in the presence of methanol
Authors: Chonde Y. , Krieger I. M.
Published: April 2003

Soap‐free emulsion polymerization of styrene with sodium vinylbenzyl sulfonate (NaVBS) was studied in the presence of water–methanol mixtures. In the presence of both methanol and NaVBS, the particle size and uniformity increased with methanol content. Increasing the concentration of NaVBS decreased the particle size. Initiator and electrolyte level had similar effects on particle size as in recipes prepared in aqueous medium.
Investigations on nylon 4 membranes: Synthesis and transport properties. II. Transport properties of nylon 4 polymer membranes
Authors: Huang R. Y. M. , Kim U. Y. , Dickson J. M. , Lloyd D. R. , Peng C. Y.
Published: April 2003

The reverse osmosis, ultrafiltration, and dialysis properties of nylon 4 membranes to separations of sodium chloride, urea, a series of ethylene glycols and other compounds in the aqueous phase were investigated. The nylon 4 membranes were prepared from a formic acid solution with and without organic or inorganic additives. The effects of polymer concentration, amount of additives, casting time, and temperature on the membrane performance in terms of salt separation and product rate were investigated. The tensile properties of the nylon 4 membranes in both the dry and wet states were determined. It was found that the highest salt separation of a 0.1% sodium chloride solution did not exceed 53.3%. However, these membranes showed some intersting dialysis properties which were comparable to those of commercial cellophane and cellulose acetate membranes.
Onset of phase separation in segmented urethane polymerization
Authors: Castro J. M. , López‐Serrano F. , Camargo R. E. , Macosko C. W. , Tirrell M.
Published: April 2003

The development of heterogeneous structure during the polymerization of a polyurethane system using a polyether diol of M̄n = 2000 as the soft segment and 4,4′‐diphenylmethane disocyanate extended with 1,4‐butanediol as the hard segment was monitored following the amount of light transmitted by the sample and the increase in viscosity of the reacting mixture. The amount of light transmitted by the reacting sample was observed to decrease sharply at a given point in the reaction. The cloud point was taken as the onset of phase separation in the system and the number average sequence at this point was found to be fairly constant at about 1.3 independent of reaction temperature and system composition. In many cases, the cloud point occurred at quite low conversion, meaning that a significant amount of subsequent polymerization occurs in a heterogeneous medium. It was also found that the viscosity of the material reached very large values at partial conversions of the monomers and presented throughout the reaction values larger than those expected from an increase in molecular weight alone. Viscosity is apparently sensitive to a different aspect of the phase separation process than the light transmission.
Hydrolytic stability of some uncured epoxy resins
Authors: Pearce P. J. , Davidson R. G. , Morris C. E. M.
Published: April 2003

The hydrolytic stability of triglycidyl(4‐aminophenol) (ERL 0500), tetraglycidyl(methylenedianiline) (MY720), and a number of model compounds has been investigated. It has been shown that at 60°C and 96% relative humidity undiluted N‐glycidyl aromatic amine‐based epoxy resins readily undergo hydrolysis followed by homopolymerization. Impurities in the resin may significantly accelerate the rate of reaction. The effect of the consequent loss of epoxide on the performance of an adhesive based on ERL 0500 has been studied. The high‐temperature tensile‐shear strength of Joints was markedly reduced when the adhesive was aged, before cure, for 24 hr at 60°C and 96% relative humidity. Some implications of these findings for aerospace applications of epoxy compounds are discussed.
Structure‐property relationships of an electron beam cured model urethane prepolymer
Authors: Joseph Eugene , Wilkes Garth , Park Kisoon
Published: April 2003

A semicrystalline urethane prepolymer derived from polycaprolactone was crosslinked below and above the melt to different levels using electron beam radiation. Studies at room temperature on the systems crosslinked under ambient conditions, which is below the melting temperature, show that changes in mechanical properties which occur as the electron beam dose is increased are due principally to the increase in crosslink density and to the changes in the crosslinking mechanism. Specifically, crosslinking takes place mainly at the acrylate double bonds or may also occur along the polymer backbone. All systems, however, are semicrystalline and possess a spherulitic texture. Mechanical and rheo‐optical testing above the melt on these same systems indicate that at extensions up to 125% classical rubber elasticity theory and photoelasticity theory is obeyed. Isothermal crystallization kinetics measurements show that the rate of crystallization decreases as the electron beam dose is raised. When the systems are crosslinked above the melt again a spherulitic texture results. Mechanical testing above the melting temperature on the prepolymer crosslinked up to 4 Mrad shows that at elongations up to 125% classical rubber elasticity theory is obeyed. At room temperature these latter crosslinked systems exhibited a lower modulus compared to the materials crosslinked below the melt. Polarizing optical microscopy carried out above the melting temperature strongly suggested that no order was present in these systems during crosslinking in contrast to those crosslinked below the melting temperature.
Dry etching durability of positive electron resists
Authors: Harada Katsuhiro
Published: April 2003

The effects of positive electron resist structures and G values for scission on dry etching durability have been studied with regard to plasma etching, reactive sputter etching, and plasma ashing. Polymers of aromatic methacrylates, especially poly(α‐methylstyrene), all of which contain a benzene ring in the side chain, exhibit superior durability for each etching system. On the other hand, polymers of fluorinated and chlorinated methacrylates show low durability compared with the nonsubstituted polymethacrylates. In addition, they vary in durability with respect to the etching gas used. The sputtering effect which is induced by ion bombardment in flat bed‐type reactors produces a significant loss in thickness of positive resists. Rough correlations between dry etching rates and Gs(scission) as the indication of sensitivity were obtained. The large dispersion of the correlations implies the possibility of more useful positive electron resists of high durability and high sensitivity.
Thermal and pulse NMR analysis of water in poly(2‐hydroxyethyl methacrylate)
Authors: Sung Y. K. , Gregonis D. E. , John M. S. , Andrade J. D.
Published: April 2003

Hydrophilic three‐dimensional methacrylate polymer networks (hydrogels) were prepared from 2‐hydroxyethyl methacrylate (HEMA) monomer and tetraethylene glycol dimethacrylate (TEGDMA) as crosslinker. The nature and states of water in these hydrogels were studied by differential thermal analysis and pulse NMR relaxation spectroscopy. The thermal studies showed no endotherm peak for ice melting in the lower water content (bound water region); there are two endotherms peaks for higher water content hydrogels near 0°C. The amounts of bound water, intermediate water, and bulklike (free) water in the hydrogels were determined from a quantitative analysis of the endotherms of the water melting transitions. The water structure ordering in the hydrogels were discussed in terms of the fusion entropy and enthalpy obtained from the endotherm. Nuclear magnetic relaxation spectroscopy was also used to understand the mobilities of the water protons in the hydrogels and the interaction of water molecules with the gel networks. The measured spin‐lattice relaxation time (T1) values for water protons in the hydrogels are greatly reduced compared to that of liquid water. The measured values of spin–spin relaxation times (T2) of water protons in the hydrogels are approximately 10 times less than that of T1 and are almost constant in the region of bound water content. Beyond the bound water content region in the hydrogels, the T2 values rapidly increase as the water content increases.
Low‐density polyethylene filled with chalk and liquid modifier
Authors: Kaliński R. , Galeski A. , Kryszewski M.
Published: April 2003

Based on the concept of introducing a liquid layer between the polymer and filler, a composition containing low‐density polyethylene, chalk, and oligomer of ethylene oxide was proposed. Compositions containing up to 50% chalk modified with ethylene oxide exhibit typical thermoplastic behavior, i.e., neck formation and plastic deformation. They also show high‐impact strength and other good properties. On the basis of mechanical data, the main action of the ethylene oxide oligomer in the system is to inhibit crack generation and propagation.
Three‐stage interaction of dimethyl phthalate, dibutyl phthalate, and poly(vinyl acetate) with poly(methyl methacrylate)
Authors: Olayemi J. Y. , Oniyangi N. A.
Published: April 2003

The interaction of dimethyl phthalate (DMP), n‐dibutyl phthalate (DBP), and poly(vinyl acetate) (PVAc) with poly(methyl methacrylate) (PMMA) was studied. Changes in the tensile strength, elastic modulus, and percentage elongation at break of the PMMA‐additive films produced were followed using the Instron testing machine. The three additives produced (1) an initial plasticization, with a decrease in tensile strength and modulus and a possible increase in elongation; (2) an antiplasticization, with accompanying increase in tensile strength and modulus and an anomalous increase in elongation; and (3) a final plasticization, with a marked decrease in tensile strength and modulus and a definite increase in elongation of PMMA. The three effects were influenced by the molecular weight of the PMMA. A spacer effect by the interposition of the molecules of the additives between those of PMMA is proposed for the initial plasticization, while for the final plasticization, a lubrication action of the plasticizers on PMMA is suggested. Antiplasticization is explained by the formation of secondary bonds between the antiplasticizer and the PMMA molecules.
Photochemical grafting of acrylated azo dyes onto polymeric surfaces. V. Grafting of some acryloxy‐substituted aromatic diazenes as model molecules onto polypropylene, polycaprolactam, and poly(ethylene terephthalate) films
Authors: Calgari S. , Selli E. , Bellobono I. R.
Published: April 2003

Photochemically induced grafting (1) and graft polymerization (2) from N,N‐dimethylformamide solutions of four acryloxy‐substituted aromatic diazenes, chosen as model molecules of acryloxy azo dyes, were investigated kinetically at 25°C onto polypropylene, polycaprolactam, and poly(ethylene terephtalate) films, by polychromatic irradiations. Quantum efficiencies at zero concentration of dyes and lifetimes of excited states for processes (1) and (2) were evaluated from experimental data by Stern–Volmer plots. The surface density of grafted molecules at the end of process (1) was not affected by the concentration of dyes in solution, but varied sensibly with the chemical nature of polymers and dyes. The relevant parameters are discussed on the basis of the proposed mechanism.
Removal of mercuric ions by systems based on cellulose derivatives
Authors: Tashiro Tatsuo , Shimura Yukio
Published: April 2003

A few cellulose derivatives were prepared by the reaction of chlorodeoxycellulose (CDC) with ethylenediamine (ED), thiourea, thiosemicarbazide, thioacetamide, and others. These derivatives were found to be able to remove mercuric ions to an extent greater than 99% from a 10 ppm aqueous solution of mercuric chloride. For example, thiocellulose obtained by reacting CDC with thiourea and subsequently hydrolyzing it showed such good removal in the batch and continuous removal tests which involved passing the solution through a column packed with this cellulose derivatives.
Recovery of indan derivatives from polystyrene waste
Authors: Ogawa Taichi , Kuroki Takeshi , Ide Shoaki , Ikemura Tadashi
Published: April 2003

The recovery of indan derivatives from polystyrene waste for the purpose of efficient utilization of plastic wastes was studied. An attempt was made to construct the apparatus, in which thermal decomposition of polystyrene and catalytic reaction of its decomposition products over silica–alumina catalyst could be controlled continuously at the same time. The reaction temperature for thermal decomposition of polystyrene in the upper part of a reactor tube was 420°C, while that for catalytic reaction of the thermal decomposition products in the bottom of a reactor tube was 300°C. These results indicated that the composition of thermal decomposition products of polystyrene could be controlled by the use of a flow reactor. The indan derivatives recovered were two 1‐methyl‐3‐phenylindans, one 1‐methyl‐1‐phenylindan, and 1‐phenylindan. The yields of these indan derivatives were 20% of the weight of the liquid products recovered. On the basis of the results obtained in the present work, the most suitable reaction conditions to recover indan derivatives from polystyrene waste is discussed.
The curing of novolacs with paraformaldehyde
Authors: Adabbo H. E. , Williams R. J. J.
Published: April 2003

The curing of novolacs with paraformaldehyde is analyzed with several experimental techniques (DSC, IR, sol fraction) as well as statistical arguments. Results for typical novolacs show that a maximum crosslinking density is attained at a mass ratio mP/mN close to 0.20. However, at mP/mN greater than 0.10, hemiformals appear in the cured product, increasing the amount of extractable formaldehyde. The heat of reaction increases linearly from mP/mN = 0 to 0.15, attaining a maximum value of −ΔH = 98 cal/g novolac at mP/mN ∼ 0.20. The curing kinetics follows an overall second‐order law with an activation energy E = 32.5 kcal/mol and a preexponential factor A = 1.1 × 1015 min−1 (both for mP/mN > 0.1).
Straining phenomena of POY revealed by thermal retraction and other techniques
Authors: Selivansky Dror , Lewin Menachem
Published: April 2003

Partially oriented polyesters yarns (POY) were strained at different strain rates (0.03–12.00 min−1) and temperatures above and below Tg (3–92°C). Thermal retraction, density, DSC, and WAXS techniques show that strain‐induced crystallization takes place by straining at temperatures above as well as below Tg. Above Tg, depending upon the strain rate, two regimes are observed: Below the strain rate of 1.5 min−1, the flow regime; the degree of crystallinity is reduced as the strain rate increases. Above the strain rate of 1.5 min−1, the strain‐induced crystallization regime; the degree of crystallinity increases as the strain rate increases. Thermal retraction, stress–relaxation, and sonic modulus techniques indicate that, upon cold straining, instead of the original Tg at 65–69°C, two glass transitions occur: an upper Tg (u) and a lower Tg (l). For POY strained at 3°C and at a strain rate of 10 min−1, the values are 78°C and 37°C, respectively. The higher the strain rate and the lower the straining temperature, the large the difference between Tg (u) and Tg (l).
Thermal oxidation of polypropylene close to industrial processing conditions
Authors: Hoff Ariel , Jacobsson Sven
Published: April 2003

Thermal oxidation of isotactic polypropylene (PP) at 220 and 280°C in air was studied. Gas chromatography–mass spectrometric analysis was used to separate and identify the volatile products of PP oxidation. Twenty‐three products were identified and 15 substances were quantified. The aldehydes are the principal products formed, followed by ketones, acids, and alcohols. The main organic product quantified was acetaldehyde. The volatile organic products formed constitute about 3% of the amount of water formed. The relative amounts of the most volatile products formed in the range 220–280°C are practically independent on the temperature of oxidation. The mechanism of formation on the oxidation products is discussed.
Phase separation in segmented polyurethanes
Authors: Kwei T. K.
Published: April 2003

Phase separation in a segmented polyurethane has been studied by differential scanning calorimetry. The glass transition temperature of the soft phase decreases logarithmically with time to a limiting value at each annealing temperature. The magnitude of the decrease is larger at low annealing temperatures, but the normalized rate of logarithmic decrease is smaller. At high annealing temperatures, long sequences of hard segments are excluded from the soft phase in which short segments are still soluble. At low temperatures, even short hard segments separate from the soft phase. The exclusion of the hard segments from the soft phase is a relatively fast process, but the development of order in hard domains takes longer time to reach steady state.
Non‐steady‐state transport of diffusants in ternary laminate slabs
Authors: Le Poidevin Graham J.
Published: April 2003

Equations describing transient diffusion in ternary laminate slabs are presented. The equations developed can be applied to: (I) asymmetric ABC slabs separating two semi‐infinite baths, each bath containing either the same or different concentration(s) of permeant; (II) asymmetric ABC slabs separating a semi‐infinite bath from an impermeable substrate; (III) asymmetric ABC slabs with impermeable substrates attached to laminas A and C. Further, the equations can be applied to slabs containing initially uniform, but not necessarily equilibrial, concentrations of permeant in each lamina. Some numerical examples of the aforementioned diffusion systems I and II are discussed.