bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations on the curing of epoxides with phthalic anhydride
Authors: Steinmann Bettina
Published: April 2003

The anhydride curing of epoxides was studied by performing copolymerizations of epichlorohydrin, phenyl glycidyl ether (PGE), or bisphenol‐A‐diglycidyl ether (BADGE) with phthalic anhydride (PSA). As initiators, tertiary amines or ammonium salts were used. In the case of epichlorohydrin, linear polyesters were obtained at 100°C. At higher temperatures (140–160°C), a side reaction of the CH2Cl group took place which caused branching and partial crosslinking of the polymer. The reaction of phenyl glycidyl ether with phthalic anhydride gave linear, strongly alternating copolymers at temperatures of 120–160°C. Molecular weights (M¯n) were in the range of 4000–87,000, depending on the purity of the starting materials and the initiator used. The reaction of the diepoxide BADGE with phthalic anhydride yielded highly crosslinked products. Their crosslink densities (which correlate with the glass transition temperature Tg). however, did not show the same dependence on initiator and purity of the starting materials as the molecular weights of the linear polyesters obtained by the “model reaction” of PGE with PSA. Possible reasons for this effect are discussed.
Study and control of phase morphology in liquid crystal polyester–poly(alkylene terephthalate) blends
Authors: Croteau J. ‐F. , Laivins G. V.
Published: April 2003

Scanning electron microscopy (SEM) reveals that the morphologies of poly(hexamethylene terephthalate) (PHMT) and poly(p‐oxybenzoate co‐ethylene terephthalate) (LCP6/4) blends are biphasic. When LCP6/4 is the minor component, liquid crystalline domains are embedded in the matrix. The reaction in the melt between the polymers apparently increases the adhesion of the matrix to the embedded domains. As the reaction proceeds, the chemical composition of the matrix progressively becomes modified. High reaction temperatures, small particle size, mixing coupled with particle dispersion and high LCP6/4 content in the mixture promote the melt reaction and decrease the PHMT content in the polymer formed. At 260°C, the coaddition of di‐n‐octadecyl phosphite (DNOP) at a 2% weight fraction with PHMT and LCP6/4 inhibits the reaction between the polymers for 2 h.
Hollow fiber membranes spun from lewis acid : Base complexes. I. Structure determination by oxygen plasma ablation
Authors: Fritzsche A. K. , Cruse C. A. , Kesting R. E. , Murphy M. K.
Published: April 2003

The structures of polysulforne hollwo fiber membranes, spun from the propionic acid : N‐meth‐ylpyrrolidone complex and from a formylpiperidine/formamide mixture were investigated as a function of progressive surface removal with an oxygen plasma. Oxygen plasma ablation experiments were performed on both unexposed and isopentanetreated hollow fiber membrances. Pure gas permeation rates were obtained on these samples as well as oxygen plasma etched samples which were then subsequently coated with polydimethyl‐siloxane from an isopentane solution. The results show that the hollow fiber membrane spun from the propionic acid : N‐methylpyrrolidone complex has both a thinner active separating layer and a thinner skin than the polysulfone hollow fiber membrane spun from the formylpiperidine/formamide mixture. Also, the resistance to flow of the porous substrate of the complex spun hollow fiber membrane is significantly less than that of the polysulfone hollow fiber membrane spun from the mixture. Therefore, the substrate of the PA : NMP complex spun hollow fiber membrane has greater porosity and less tortuosity than its FP/FA congener. The oxygen plasma ablation results and the scanning electron micrographs demonstrate a nonequivalence between the active separating layer and the microscopically observable skin of the hollow fiber membrane. It is believed that membranes prepared from Lewis acid : base complex solvents possess a porous substructure and a nonuniform (graded‐density) skin which consists of a very thin active separating layer whose effective thickness varies depending upon the gases to be separated and a thin less dense transition layer, which may contain pores whose sizes are below the limits of resolution by SEM. Both are components of the microscopically observable skin. Membranes possessing this structure belong to the trilayer class of integrally skinned membranes. If membranes are so fabricated that the density gradient in the active separating layer approaches zero, a bilayer membrane with a porous substructure and a thin skin of uniform density results. Membranes prepared from conventional solvent/nonsolvent mixtures, i.e., formylpiperidine/formamide, exhibit a diminished density gradient in the skin approximating the bilayer model.
Purification of styrene for anionic polymerization
Authors: Priddy Duane B. , Pirc Michael
Published: April 2003

Anionic polymerization of styrene in CSTR processes demands monomers which are highly pure. Lithium aluminum hydride (LAH) is a highly reactive material which reacts with the impurities in styrene that interfere with anionic polymerization. The LAH/impurity reaction products are not compatible with anionic polymerization and therefore must be isolated or removed from the styrene before polymerization. This problem is most readily solved by supporting the LAH on ion exchange resin beads such that the impurity reaction products are chemically bound to the support. We have demonstrated the preparation of > 50 mol of polystyrene/mol of n‐butyl lithium by passing the polymeization feed through a column filled with LAH/ion exchange resin. This represents > 10‐fold improvement in yield (based on n‐butyl lithium) over previously described feed purification techniques.
Preparation and properties of a series of thermotropic liquid crystalline copolyesters
Authors: Kim Han Do , Paul D. R.
Published: April 2003

A series of thermotropic liquid crystalline copolyesters were prepared by melt polymerization using p‐hydroxybenzoic acid (HBA) and terephthalic acid (TPA) as mesogenic monomers, poly(ethylene terephthalate) (PET) to give a flexible linkage, and 1,4‐dihydroxynaphthalene (1,4‐DHN) as a dissymmetrical monomer. The composition of these monomers was varied as a means of manipulating processing temperature, morphology, and properties. Copolyesters with inherent viscosities near 0.7 that were melt processible in the temperature range of 200–300°C were obtained. The glass transition, thermal degradation, and melting temperatures, and crystal size all increased with increasing mesogenic unit content. The heterogeneous structure consisting of a PET‐rich phase and a phase rich in mesogenic units was observed by SEM after chemical etching and by X‐ray diffraction analysis. Highly anisotropic melts were observed indicating the presence of a nematic mesophase. The thermotropic LC copolyesters exhibit unusually well developed and highly oriented fibrillar structure at the neck area when injection molded. The orientation developed during processing is very similar to those of short‐fiber‐filled polymer composites. The LC copolyesters commonly have three relaxations in the temperature range of −100–200°C. By dynamic mechanical thermal analysis at 10 Hz, the relaxation temperatures were found to increase with increasing content of mesogenic units and of 1,4‐DHN. For the temperature range of 25–120°C, the storage modulus of one of the members of this series were compared with Vectra (Celanese) and with Eastman PHB80, which have almost the same mesogenic contents. This new copolyester maintained its modulus until 80°C, while the modulus of Vectra decreased in two steps; a small depression at 40°C and then a large reduction at 85°C. PHB80 shows a large single transition at 50°C.
The rheooptical properties of polymer blends: Polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Greener J. , Machell J. S.
Published: April 2003

The stress‐optical coefficients (SOCs) of miscible polystyrene (PS)/poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PRO) blends were measured in the melt state over a wide range of compositions. The flow birefringence measurements were performed with a slit die rheometer using a simplified procedure which eliminates the need to specify the distribution of extinction angles in the flow space. The SOC of the PS/PPO system at ∼Tg + 110°C follows a linear blending law and full optical compensation (SOC = 0) is observed at ∼61 wt% PS. This value is lower by ∼10% relative to values obtained by film stretching techniques. Measurements of SOC in the glassy state also yield linear dependence of SOC on composition but no compensation is obtained in this case because of the sign reversal in the SOC of PS in the glass transition range.
Changes in void content and free volume in fibers during heat setting and their influence on dye diffusion and mechanical properties
Authors: Murthy N. S. , Reimschuessel A. C. , Kramer V.
Published: April 2003

The contributions of the changes in porosity and free volume to the differences in the properties of dry and wet heat set fibers are analyzed. Nylon 6 fibers heat set in wet atmosphere (autoclave and Superba process) show a significantly higher small‐angle X‐ray scattering intensity between 0.5° and 1.5° (Cu Kα) relative to corresponding non‐heat‐set fibers, whereas the fibers heat set in dry atmosphere (Suessen process) do not. This scattering arises from the electron density contrast due to pores and free volume which lower the elctron density between the fibrils. The average diameter of the crystalline fibrils, as calculated from the Guinier analysis of diffuse scattering, increases from ca. 50 to 65 Å in all fibers upon heat setting. Additional scattering at much lower angles is attributed to aggregates of fibrils. Transmission electron microscopic studies of fibers stained by AgI, through I2/methanol/AgNO3 treatment, suggest that as AgI crystallizes in a dendritic network along the paths opened up by the diffusion of iodine, it brings about large structural changes in the polymer; this process reveals defects and latent diffusion paths in the fiber. The dendritic structures of AgI are more extensive in wet heat set fibers than in dry heat set and non‐heat‐set fibers. The ordering within the crystalline domains, the interlamellar spacing, and the density of the fiber increase during both wet and dry processes. The role of these changes in the structure and the morphology of the fibers on the dyeing and ozone fading behavior, and on the strength and the modulus of the fibers, are discussed.
A sphere buoyant in a dilute polymer solution
Authors: Grisafi S.
Published: April 2003

The density and pressure fields of a dilute polymer solution are nonuniform at the surface of a small sphere even when there is no fluid motion. The polymer solution is modeled by an ensemble of Hookean dumbbells. A hard core potential is assumed as the only interaction between the sphere and the macromolecules. The pressure field about the sphere is transversely isotropic. The perpendicular component of the pressure at the interface is greater than the isotropic pressure in the bulk of the fluid. The parallel component of the pressure at the interface is less than the bulk isotropic pressure. The surface adsorption (cf., surface pressure) and the film thickness vary with a parameter that is the ratio of the sphere radius, a, to the root mean square extension of the dumbbells, R0. The spherical results coincide with the plane wall results for a/R0 greater than approximately 100.
Permeation of CO2 through polyurethane
Authors: Xiao H. , Ping Z. H. , Xie J. W. , Yu T. Y.
Published: April 2003

The permeability of CO2 through polyurethane was investigated. It is found that the permeability increases with the decrease of hard segment content and the increase of soft segment length; however, no change of activation energy is involved. The permeability increases with the elevation of annealing temperature. The temperature dependence of permeability observes the Arrhenius equation at temperatures below 60–80°C, but it deviates at temperatures above this range. This deviation would be attributed to the increase of mixing of hard and soft segments as a result of the dissociation of short‐range order in hard segment domains.
Multiple transitions in a dimethacrylate network
Authors: Wilson T. W.
Published: April 2003

Triethylene glycol dimethacrylate, TEGDM, was cured to various dose levels (0.15–2.0 Mrad) by γ‐irradiation at 40°C and its dynamic mechanical properties were evaluated. The resultant products had up to four transition phenomena dependent upon dose. The highest temperature transition (IV) was due to the ultimate glass transition. Transition III (ca. 40°C) was due to additional reaction occuring just above the cure temperature. Transition 1 (ca. ‐60°C) occurred at low doses and was associated with residual monomer. Transition II (ca. ‐10°C) is due to association of (CH2CH2O) units in TEGDM monomer, and the associated regions persist in the crosslinked polymer.
Effect of internal lewis bases on recrystallized MgCl2–TiCl4 catalysts for polypropylene
Authors: Kang Kyung‐Suk , Ok Myung‐Ahn , Ihm Son‐Ki
Published: April 2003

The effect of different Lewis bases in TiCl4 catalysts supported on MgCl2, which was modified by the recrystallization method, has been investigated in terms of activity, selectivity, and morphology. Ethyl benzoate (EB) and 2,2,6,6‐tetramethylpiperidine (TMPip) were tested as the internal Lewis bases. Propylene polymerizations were performed at 50°C and 7 atm, using Al(C2H5)3 as co‐catalyst and TMPip as external modifier. Both supports and catalysts were characterized by BET, X‐ray, SEM, and other techniques. It was found that the electron donor plays an important role in the recrystallization step of MgCl2 from alcoholic MgCl2 solution. Ethyl benzoate was the more effective internal donor leading to the porous, free‐flowing, and stable high‐activity catalyst, while TMPip was not so effective as internal donor owing to its decomposition by SiCl4 during the support preparation. From short time polymerization kinetics, EB was found to increase both the values of the active site concentration ([C*]) and the propagation rate constant (kp). Comparison with the ball‐milled catalyst has been made in view of the morphology. The morphology of the polymers formed with the recrystallized catalysts was the globule‐like structure, while that with the milled catalyst was the broken structure due to its low surface area.
Preparation of transparent conducting acrylic composite and its electrical properties
Authors: Park Yun Heum , Kim Yong Kweon , Lee Doo Sung
Published: April 2003

Polyacrylonitrile (PAN)/polythiophene (PTP) composite films were prepared by polymerizing thiophene vapor in PAN films impregnated with sulfuric acid or aluminum chloride as an initiator. After polymerization of thiophene for 1 h, the electrical conductivities of composites reach in the range of 10−7–10−3S/cm depending on the initiator and its concentration. The stability of conductivity to ambient air exposure is excellent. The transparency of composite films has been estimated by transmittance at the maximum absorption wavelength of 593 nm. The transmittance of composite film prepared with 10% of sulfuric acid on the weight of PAN reaches above 90%. The transparency has been maintained for the period of experiment, i.e., 1 month under ambient air exposure. Sulfuric acid is more effective than aluminium chloride for the preparation of transparent conducting PAN/PTP composite films.
Photodegradation of polyethylene: Factors affecting photostability
Authors: Torikai Ayako , Shirakawa Hajime , Nagaya Shigeo , Fueki Kenji
Published: April 2003

Four kinds of annealed polyethylene (PE) films with varying densities were photo‐irradiated with a medium pressure mercury lamp. Photodegradation processes were followed by ultraviolet (UV) and Fourier transform infrared (FTIR) spectroscopic techniques and by gel and mechanical property measurements. Oxygenated products build‐up was more favored in linear low density (LLD) PE and the rate of formation increased in the reverse order of polymer density. A similar trend was seen in gel formation. Measurements of elongation at break (%) showed that the embrittlement time of photo‐irradiated PE increased with the decrease of polymer density. The experimental results on unquenched samples were compared with those of quenched samples. It was found that the density (or crystallinity) and crystal size of PE play important roles in determining photostability.
Preparation of ultra‐high modulus polyvinyl alcohol fibers by the zone‐drawing method
Authors: Kunugi Toshio , Kawasumi Tamio , Ito Takashi
Published: April 2003

The zone‐drawing method has been applied to prepare ultra‐high modulus polyvinyl alcohol fibers. First, the suitable temperature for zone‐drawing was decided. In the first zone drawing, when drawing temperature was as high as near melting point, the highest draw ratio and modulus were obtained. The modulus was further increased by repeating zone drawing and heat treatment. In this study, the highest dynamic moduli were 115 GPa at room temperature and 42 GPa at 200°C. The fiber has a sharp melting peak that appeared at 246°C and a small peak at 260°C in the DSC curve.
Application of UV‐curable diazoresin. I. Immobilization of glucose oxidase into PVA in the presence of UV‐sensitive diazoresin and sensitizers
Authors: Liu Jui‐Hsiang , Chen Ming‐Yi , Lin Ming‐Te
Published: April 2003

A study of the immobilization of glucose oxidase into poly(vinyl alcohol) membrane in the presence of UV light sensitive diazcresin and benzoic acid and/or sodium benzoate sensitizers was carried out. An effective enzyme electrode by using the immobilized glucose oxidase membrane was developed. The effect of the concentration of diazoresin and sensitizers in poly(vinyl alcohol), UV nght irradiation on the degree of insolubility as well as the activity yield of the membrane were examined for the immobilized glucose oxidase using glucose as a substrate. An unstable phenomenon was found in the initial usage of the immobilized glucose oxidase membrane prepared from poly(vinyl alcohol)‐sensitizer system. Activity yields of 39.98 and 35.30 for poly(vinyl alcohol)‐diazoresin and poly(vinyl alcohol)‐sensitizer system were obtained, respectively.
Miscibility of poly(chloromethyl methacrylate) with bisphenol‐A polycarbonate
Authors: Goh S. H. , Lee S. Y. , Neo M. K.
Published: April 2003

Poly(methyl methacrylate) (PMMA) and bisphenol‐A polycarbonate (PC) are important commerical polymers. PMMA/PC blends were once considered as immiscible blends.1–3 However, recent studies have shown that the miscibility of PMMA/PC blends depends on the method of preparation.4–8 Chiou and co‐workers4 reported that PMMA/PC blends prepared by solution casting and melt mixing were immiscible while blends prepared by precipitation from solution using n‐heptane as nonsolvent were miscible over the whole composition range. Kyu and Salhanda5 reported that PMMA/PC blends cast from tetrahydrofuran (THF) at room temperature were immiscible but those cast from THF at temperatures above 47°C were miscible. In this communication, we report the miscibility of poly(chloromethyl methacrylate) (PCMMA) with PC. It will be shown that the miscibility behavior of PCMMA/PC blends is similar to that of PMMA/PC blends.
Miscibility enhancement of polystyrene and poly(alkylene oxide) blends using specific intermolecular interactions
Authors: Weiss R. A. , Beretta C. , Sasongko S. , Garton A.
Published: April 2003

Acid–base interactions were used to enhance the miscibility of blends of polystyrene and oligomeric poly(alkylene oxide). The polystyrene was modified by sulfonation of less than 5% of the styrene rings. The poly(alkylene oxides) were low molar mass polyethylene oxide chains (M = 900 and 6000) that were end capped with propyl amine groups. Blends of the poly(alkylene oxide) diamines with polystyrene were immiscible. Blends with the sulfonated polystyrenes were miscible due to proton transfer from the sulfonic acid groups to the basic amino groups of the functionalized poly(alkylene oxide). This was confirmed by FTIR. DSC and dynamic mechanical analyses were used to verify the one‐ or two‐phase nature of the blends.
Polymérisation radicalaire du pentadiène‐1,3. IV. Détermination de la composition et du “run number” des copolymères de cis‐ ou trans‐pentadiène‐1,3 et d'acrylonitrile par pyrolyse éclair couplée à la chromatographie en phase gazeuse
Authors: Petit Alain , Néel Jean
Published: April 2003

This paper investigates the possibility of using the method of flash pyrolysis‐gas chromatography for the quantitative determination of the composition of free‐radically prepared cis‐ or trans‐1,3‐pentadiene–acrylonitrile copolymers and for evaluation of their comonomer sequence distributions in terms of the run numbers. The experiments (sample weight: 50 μg, pyrolysis time: 4 s) were carried out, under a flow of helium, at a thermolysis temperature ranging from 450 to 900°C with a Curie‐point pyrolyzer. After discussion of the respective thermal behaviors of the poly(1,3‐pentadiene), polyacrylonitrile, mixtures of these homopolymers, and various kinds of copolymers (radically or fully alternating samples), the pyrolysis–gas chromatographic characterization of the primary structure of copolymers was studied, between 500 and 800°C, through the quantitative treatment of the corresponding liberated monomers which appeared on the pyrograms. By applying the both‐side boundary effect theory on the molar amounts of these degradation products, which depend both upon copolymer composition and triad sequence distributions in the chain, the relative values of the monomer formation probability constants were calculated. The composition and the run number of each pyrolyzed sample were then determined using these parameters. The analytical data obtained by means of the procedure suggested are in very good agreement with those predicted, from reactivity ratios, by the usual theory of copolymerization (terminal‐unit model) and with the evaluations provided by the 13C‐NMR spectroscopy.
Characterization of radiation induced ethyl methacrylate grafted nylon‐6 fibers
Authors: Basak Anindita , Nayak Padm A. L. , Lenka S.
Published: April 2003

Ethyl methacrylate grafted nylon‐6 fibers prepared by mutual irradiation technique was characterized to determine the modifications in its properties arising as a result of grafting. Scanning electron microscopy study provides some information about the presence of grafting. Density of fibers were found to increase constantly with percentage graft. Where as alkali solubility, moisture regain decreased with percentage graft thereby decreasing the dyeability of the fiber. However the ethyl methacrylate grafted nylon‐6 fiber showed improvements in its thermal properties over the original nylon‐6 fiber.
Effect of absorbed water on undercured epoxy/amine thermosets
Authors: Johncock P.
Published: April 2003

The effect of water immersion at 70°C on undercured epoxy thermosets obtained from tris[4‐(2,3‐epoxypropoxy)phenyl]methane and 4,4′‐diaminodiphenylsulphone and from N,N‐bis(2,3‐epoxypropyl)aniline and 1,3‐diaminobenzene was investigated. It is concluded from water absorption studies, Tg measurements, and gravimetric data that the predominant reaction is that of additional cure induced by the plasticising and catalytic effect of the absorbed water.
Epoxy resin modified by aliphatic cyclic carbonates
Authors: Rokicki Gabriel , Wojciechowski Cezary
Published: April 2003

Bidentate and tridentate cyclic carbonates obtained from the reaction of aliphatic epoxy compounds with carbon dioxide were used for the modification of an epoxy resin. The compositions obtained exhibited low viscosity, short gel time, and low exothermic effect accompanying the crosslinking. On the basis of model reactions, a mutually accelerating effect of epoxy and cyclic carbonate groups on the crosslinking of the studied systems by triethylenetetramine was found (synergistic effect). The cured epoxide–cyclic carbonate compositions exhibited considerably higher impact resistance and tensile strength in comparsion with epoxy resins.
Efficient syntheses of the triblock copolymer styrene‐b‐tetrahydrofuran‐b‐styrene by coupling of preformed blocks
Authors: Chien James C. W. , Hong Jin‐Long , Lillya C. Peter
Published: April 2003

The triblock copolymer styrene‐b‐tetrahydrofuran‐b‐styrene was prepared from commercially available hydroxyl‐terminated poly(tetrahydrofuran), Mn = 1,650 and mono‐hydroxyl‐terminated polystyrene, Mn = 7,600. Poly(tetrahydrofuran) blocks were first chain extended by reaction by with 1.1 equivalents 4,4′‐diphenylmethane diisocyanate (MDI) and subsequently end capped with 20% excess of hydroxyl‐terminated polystyrene. Gel permeation chromatography revealed clearly the success of the end capping step to give triblock copolymer mixed with a small amount of excess polystyrene. 1H NMR revealed a gross composition by weight of 50% styrene, 41% tetrahydrofuran, and 9% MDI. DSC revealed a 5°C elevation of the PTHF glass transition and a 15°C lowering of PS glass transition temperature as compared with those of the individual component blocks. These values along with behavior of films as a tough elastomer are consistent with triblock structure and microphase separated morphology. The polymer does not flow readily below 125°C which is well above Tg of the polystyrene domains.
Water sorption in styrene crosslinked polyesters
Authors: Bellenger V. , Mortaigne B. , Verdu J.
Published: April 2003

Various polyester samples differing essentially by the diol nature, the proportion of unsaturated diacid, or the prepolymer chain length were studied by gravimetry at 30, 40, or 50°C, 95% RH. The water equilibrium concentration increases with the test temperature and with the polar group concentration: esters, ethers and alcoholic or acidic chain ends. The diffusivity appears as an increasing function of the crosslink density which can be due to the “bonding” effect of chain ends through strong hydrogen bonds and/or to the fact that local motions are as favoured as the chain end concentration decreases.
Changes of structure and morphology of regenerated cellulose caused by acid and enzymatic hydrolysis
Authors: Lenz J. , Esterbauer H. , Sattler W. , Schurz J. , Wrentschur E.
Published: April 2003

The kinetics of the enzymatic hydrolysis of regenerated cellulose fibers before and after acid prehydrolysis has been investigated. This pretreatment changes the kinetics from a monophasic to a biphasic first order reaction. Prolonged acid prehydrolysis increases the proportion of the enzymatically easily hydrolyzable cellulose form. The kinetics were correlated with corresponding changes of the degree of polymerization, crystallinity and crystallite size.
Cathodically depositable systems based on epoxy resin and blocked isocyanates with cardanol
Authors: Balakrishna R. S. , Sathyanarayana M. N. , Vishwanath B. Balaji , Shirsalkar M. M.
Published: April 2003

Cathodically electrodepositable binders based on the reaction products of epoxy amine adduct and various proportions of partially blocked isocyanates with cardanol were prepared. Paints were formulated from the above binders using rutile titanium dioxide as pigment in the pigment volume concentration, ranging from 0–50%. A comparative study has been made on the physicochemical properties and electrodepositable characteristics of binders and the paints.
Synthetic resin. IX. Preparation and characterization of resins prepared from resacetophenone, quinacetophenone/aromatic hydroxy, amino and chloro compounds/formaldehyde
Authors: Nayak Pramod K. , Lenka Subasini , Nayak Padma L.
Published: April 2003

A number of new resins were synthesized from 2,4‐dihydroxyacetophenone and 2,5‐dihydroxyacetophenone by reaction with substituted hydroxy, amino, and chloro compounds and formaldehyde in presence of various acids and bases as catalyst. The resins were characterized by IR spectra. The solution and chemical properties of the resins were investigated. The solubility parameter was calculated from Small's and Hoy's group contribution methods. The fungicidal properties of the resins synthesized have been evaluated.
Heat setting of oriented poly(ethylene terephthalate): Effects of deformation mode, strain level, and heating medium
Authors: Buckley C. P. , Salem D. R.
Published: April 2003

We continue a previous study of the α and α′ mechanical relaxation processes in oriented poly(ethylene terephthalate) by means of heat‐setting experiments on drawn filaments between room temperature and the melting region. Both processes were exhibited in both torsion and bending deformations, but heat setting was found consistently to be greater in bending than in torsion: this was accounted for by the known anisotropy of the α relaxation. In both modes of deformation, increasing strain level gave reduced recovery, and results suggested this arose from high stresses activating at room temperature the stress relaxation mechanisms, which at low stresses occurred only at elevated temperatures (α if as‐drawn, α′ if preset). Results were found to be independent of whether blown air or stirred oil was used as heat transfer medium, in contrast to some previous reports in the literature; the reason lay in differences in the precise sequences of deformation and temperature employed.
Controlling photoimaging of epoxies by blending to a specific molecular weight
Authors: Russell David J.
Published: April 2003

An epoxy formulation developed for a photoimaging application was found to exhibit poor clean‐out in the developing solvent depending on the lot of one of the base resins. Size exclusion chromatographic (SEC) analysis of the residual material showed it to be a high molecular weight (Mw) fraction of the base resin EpiRez SU‐8. The resin was fractionated, and it was demonstrated that removing the high Mw fraction from the formulation enhanced its developability. Lower Mw versions of this resin were evaluated and found to be unsuitable. However, blending one of these resins (EpiRez SU‐6) with the SU‐8 resulted in a formulation that exhibited excellent developability. Mathematical relationships were calculated that enabled blends to be made, resulting in a defined molecular weight regardless of the lots of resins used.
Miscibility of poly(acrylonitrile‐co‐methyl acrylate) with some thermoplastic polymers
Authors: Percec Simona , Melamud Lucy
Published: April 2003

The phase behavior of binary mixtures of poly(acrylonitrile‐co‐methyl acrylate) (70 : 30) copolymer (B200) with various polymers including poly(N,N‐dimethyl acrylamide) (PNNDA), poly(maleic anhydride) (PMA), poly(vinyl pyrrolidone) (PVP), poly(2‐ethyl‐2‐oxazoline) (PEOX), poly(styrene‐co‐maleic anhydride) (50 : 50) copolymer (SMA), and poly(ϵ‐caprolactone) (PCL) was examined by differential scanning calorimetry (DSC). Miscibility of B200 with some of these polymers was observed over a limited range of composition. Several equations existing in the literature (Fox, Gordon—Taylor, and Kwei) have been employed to describe the dependence of glass transition temperature of the miscible blends as a function of the blend composition. In most cases a deviation from the weight‐average values of the experimental glass transition temperatures and of the values predicted by various equations was found. This has been attributed to specific interactions between the molecular constituents of the polymer pair.
Preparation of polystyrene‐block‐(ethylene oxide)s and characterization of the products
Authors: Uyanik Nurseli , Baysal Bahattin M.
Published: April 2003

Block copolymers containing segments of poly(ethylene oxide) and polystyrene were synthesized. Dihydroxyl‐terminated polyethers (PEG‐4000 and PEG‐20,000) were reacted with an aliphatic diisocyanate (3‐isocyanatomethyl‐3,5,5‐trimethyl‐cyclohexyl‐isocyanate) and with an aliphatic hydroperoxide (t‐butyl hydroperoxide). The resulting polymeric peroxycarbamates were used as free radical initiators for vinyl polymerization. Formation of block copolymers was illustrated by several characterization methods such as chemical and UV analysis, infrared spectroscopy, and DSC thermograms. Mechanical characterization of the copolymers was made on the basis of the stress—strain curves obtained from a mechanical testing instrument (Tensilon).
Grafting onto polypropylene. V. Graft copolymerization of 4‐vinyl pyridine and binary mixture of 4‐vinyl pyridine with acrylonitrile by preirradiation method
Authors: Kaur Inderjeet , Barsola Raghuvir
Published: April 2003

Radiation‐induced graft copolymerization of 4‐vinyl pyridine (4‐VP) and its binary mixture with acrylonitrile (AN) onto isotactic polypropylene has been studied in aqueous medium. Percentage of grafting has been studied as a function of different reaction parameters and the optimum conditions for affording maximum percentage of grafting have been evaluated. It was observed that there exists an optimum composition of the binary mixture at which percentage of grafting is maximum. The maximum percentage of grafting is obtained at the total monomer concentration of [AN + 4VP] = 0.009 moles. The graft copolymers were characterized by IR spectroscopic methods. An attempt has been made to discuss the effect of acceptor monomer (AN) on percentage of grafting of donor monomer (4‐VP).
Thermal behavior of carbon black filled polymers
Authors: Gandhi Khushroo , Salovey R.
Published: April 2003

DSC measurements suggest that polybutyl methacrylate interacts more strongly with carbon black than polystyrenes and corresponding random copolymers do, showing an increase in Tg of 8.6°C, compared to 2–3°C, by the inclusion of 20% carbon black of surface area 625 m2/g, in agreement with rheological studies. Enthalpy relaxation in the vicinity of Tg is increased by annealing at Tg – 10°C, attaining a maximum of 1.65 kJ/kg for polybutyl methacrylate and 2.6 kJ/kg for polystyrene. At constant annealing temperature, the rate of enthalpy relaxation in polybutyl methacrylate was reduced by a factor of about two by the addition of carbon black. However, both pure polystyrene and polybutyl methacrylate show the same rate of enthalpy relaxation as the corresponding filled polymers, following annealing at the appropriate Tg – 10°C.
Preparation and application of semiconductor–polymer composites
Authors: Miyama Hajime , Yokoyama Hidekuni , Nosaka Yoshio
Published: April 2003

Copper sulfide–polymer composite was prepared by depositing copper into porous polyolefine film with a method of electroless plating and sulfurizing the copper. The composite was an n‐type semiconductor and useful as a component of p–n junction device and as a gas detector. The method was also useful for the preparation of silver sulfide–, nickel sulfide–, and cobalt sulfide–polymer composites.
A new method for rapid evaluation of long‐chain branching in polymers
Authors: Chunshan Jin , Qipeng Guo
Published: April 2003

A new method for rapid evaluation of long‐chain branching (LCB) in polymers was developed. The crude GPC chromatogram and the measured value of intrinsic viscosity of the whole polymer are the only data required. By using trial and error in combination with graphic analysis, the threshold value M0 and average molecular weights M̄w and M̄n, as well as LCB can be simultaneously evaluated. The advantage of this method lies in avoiding predetermination of the M0 for a given resin. The results obtained by this method for NBS Branched Polyethylene Standard Reference Material SRM 1476 and for a branched cis‐1,4‐polybutadiene sample were in good agreement with those given by the conventional Ram–Miltz method.
The inhibition of spontaneous ignition by flame‐retarding cotton fabrics
Authors: Khattab M. A. , Price D. , Horrocks A. R.
Published: April 2003

The spontaneous ignition behavior of flame‐retarded cotton cellulose has been investigated using differential thermal analysis (DTA). One durable, phosphonium salt‐urea‐ammonia polycondensate (Proban CC), and one nondurable, ammonium polyphosphate (Amgard TR) commercially flame‐retardant‐treated fabrics have been studied. The information obtained is compared to that previously reported for untreated cotton cellulose. The onset of spontaneous ignition, temperature Ti, was determined as a function of [O2] in the flowing O2/N2 atmosphere to which samples were exposed in the DTA furnace, whose temperature was raised at a known linear heating rate. The activation energy Ep for the rate‐determining pyrolysis reaction was calculated. In the case of the Amgard TR fabric, Ep increased from 145 kJ mol−1 at 21% O2 to 261 kJ mol−1 at 50% O2, whereas that for the Proban fabric increased from 230 to 400 kJ mol−1.

A plot of 1/Ti vs. In [O2] shows two linear regions that interact at about 40% O2, which is just above the limiting oxygen index values for these two flame‐retarded samples. This intersection is interpreted as indicating that the combustion mechanism of these flame‐retarded fabrics changes as [O2] passes through this 40% level. Below this value, significant amounts of char remained after the DTA experiment, suggesting that volatiles only were ignited, whereas above this value, both volatiles and char were burnt away. This is supported by evidence from the DTA traces. The difference in slopes of the two regions of the 1/Ti vs. [O2] plots is used to obtain a value for Eox, the activation energy for gaseous oxidation. Values for Eox of 270 and 536 kJ mol−1 were obtained for the Amgard TR and Proban CC fabrics, respectively. These are considerably higher than is the value of 215 kJ mol−1 previously reported for untreated cotton. Thus, one of the ways in which these flame retardants reduce the ease of combustion of the cotton is by increasing the activation energy for the oxidation of the evolved organic species.
Crystal orientation in injection molding of talc‐filled polypropylene
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo
Published: April 2003

The crystal orientation in injection molding of talc‐filled polypropylene has been studied by means of polarizing microscopy and X‐ray diffraction measurements. The plate planes of talc particles are aligned parallel to the surface of injection molding. The c‐ and a*‐axes of polypropylene crystals are bimodally oriented to the flow direction, and the b‐axes are oriented to the thickness direction. Namely, the crystals in the injection molding of talc‐filled polypropylene show a kind of uniplanar‐axial orientation according to the classification of Heffelfinger and Burton. The degree of the bimodal orientation of c‐ and a*‐axes decreases toward the interior of the injection molding. The b‐axis orientation is strong throughout the thickness direction, although it is a little weaker at the surface skin and central regions. This peculiar crystal orientation originates from the flaky shape and crystallization nucleation ability of talc particles. In a mold cavity, talc particles are aligned parallel to the cavity wall by the action of flow, and crystallization progresses, with the (040) plane of polypropylene crystal piling on the plate planes of talc particles and the b‐axis, which is the growth direction of polypropylene crystal, being aligned to the thickness and cooling direction of injection molding. The crystal orientation in injection molding of unfilled polypropylene is basically similar to that of talc‐filled polypropylene, although the b‐axis orientation to the thickness direction is much weaker.
Vinyl‐terminated oligomeric ethers: A study of the crosslinking process
Authors: Barton S. J. , Ghotra J. S. , Matthews A. E. , Pritchard G.
Published: April 2003

A thermosetting resin consisting of a mixture of vinyl‐terminated oligomeric ethers was prepared by a two‐step synthesis. This required the reaction of 1,4‐bis (chloromethyl) benzene with the potassium salt of bisphenol A, and subsequent vinylation of the chloromethyl end groups by means of a Wittig reaction. The linear vinyl prepolymers were thermally crosslinked through their reactive styryl end groups (without the addition of catalyst) to produce castings and woven glass laminates. A study of the crosslinking process was carried out by differential scanning calorimetry (DSC). The water absorption and the thermooxidative stability of the crosslinked polymer were investigated. A styrene solution of the oligomeric ethers was also crosslinked, using benzoyl peroxide as a catalyst. The moisture absorption characteristics of the crosslinked styrene copolymer were compared with those of the crosslinked homopolymer. Both substances showed hydrophobic character.
Studies on laser‐induced irreversible surface softening in a thermoset polymer of allyl diglycol carbonate (CR‐39)
Authors: Kukreja Lalit Mohan
Published: April 2003

It is shown that controlled irreversible surface softening can be obtained in thermoset polymer of allyl diglycol carbonate (CR‐39) without degrading its bulk properties on treating it with a cw‐CO2 laser. An average value of the threshold fluence for the onset of softening is found to be about 9 J/cm2, which changes slightly with the interaction time and power density of the laser beam. Beyond this threshold the hardness of the treated surface decreases on increasing the power density and/or the interaction time till the onset of volatile decomposition in this polymer, which takes place at the laser fluence of 25 J/cm2. Thereafter, the hardness tends to saturate at nearly 60% of its original value for the untreated surface. Formation of a new heterogenous interlinked porous microstructure has been observed in the laser softened polymer surface. Solution of the 1‐dimensional heat flow equation incorporating the temperature‐dependent decomposition energy of CR‐39 has shown that at 9 J/cm2 the surface attains the maximum temperature of about 280°C and then cools at a rate of about 103°C/s. The starting value of the surface cooling rate increases with the fluence. A part of the absorbed energy goes in for the depolymerization, which is found to increase from about 0.004 to 4.5 J/cm2 when the laser fluence is increased from 9 to 25 J/cm2. The laser‐induced depolymerization and subsequent rapid cooling of the surface explain the observed effects.
Plasticized PVC films/petroleum oils: The effect of ultraviolet irradiation on plasticizer migration
Authors: Duvis T. , Karles G. , Papaspyrides C. D.
Published: April 2003

Plasticizer migration from flexible poly(vinyl chloride) comprises an important aspect, especially when packaging foodstuffs and pharmaceuticals. Much of the published work has been intended either to correlate migration into simulants with that into foods or to study migration into simpler extractants, enabling the various parameters involved in migration to be studied in isolation. According to the latter approach, the migration of dioctyl phthalate into petroleum oils has been studied already in our laboratory and in this paper results are presented in an attempt to reduce or prevent migration by u.v. irradiation. The effect of irradiation time on short and long‐term migration behavior was examined together with the influence of the immersion temperature. The nature of the liquid environment seemed to be a predominant aspect: high viscosity oils presented a satisfactory behavior in contrast with those of lower viscosity in which the prevention effect was rather negligible. On the other hand, primary kinetics studies yielded similar results with those already established for untreated material (i.e., good conformity to the short time Fickian approximation).
Poly(sodium acrylamidoalkanoate) s: Syntheses and solution properties in relation to flocculation study in water treatment
Authors: Gan L. M. , Yeoh K. W. , Chew C. H. , Koh L. L. , Tan T. L.
Published: April 2003

The micelle‐forming monomers of sodium 6‐acrylamidocaproate (Na 6‐AAC), sodium 11‐acrylamidoundecanoate (Na 11‐AAU), sodium 11‐(N‐methylacrylamido) undecanoate (Na 11‐MAAU), and sodium 11‐(N‐ethylacrylamido) undecanoate (Na 11‐EAAU) have been synthesized and polymerized. Except poly(Na 6‐AAC), the molecular weights of the other three poly(sodium acrylamidoalkanoate) s were over 106. They behave as strong anionic polyelectrolytes in aqueous solutions. Their solution properties, such as viscosity, charge density, and radius of gyration, were investigated. The performance of these anionic polyelectrolytes as coagulant aids in water treatment were assessed by jar test. Poly(Na 6‐AAC) and poly (Na 11‐AAU) were superior to poly (Na 11‐MAAU) and poly (Na 11‐EAAU) in terms of flocs settling. All these four anionic polyelectrolytes tested in water treatment are as effective as a commercially available cationic polyamine organic coagulant (Hyperfloc CP 753).
Segmented block copolymers based on liquid natural rubber
Authors: Ravindran T. , Nayar M. R. Gopinathan , Francis D. Joseph
Published: April 2003

Segmented block copolymers were prepared from hydroxyl‐terminated liquid natural rubber (HTNR) and poly(ethylene oxide) (PEO). Toluene 2,4 diisocyanate (TDI) was used as the coupling agent for combining both types of segments. Keeping the molecular weight of HTNR constant, a series of materials were prepared using PEO with varying molecular weights. Their thermal and mechanical properties were evaluated. With increasing the PEO content, the properties vary from soft to rigid elastomers and rubber‐toughened plastics. This variation in properties is caused by the changes in the sample morphology, which depends on the relative fractions of the hard and soft segments. Water absorption capability of these block copolymers was determined. Hydrogels with water content approximately up to 80% were obtained.
Properties of polypyromellitimides containing phosphorus
Authors: Varma I. K. , Kumar Ramakant , Saxena Sneh , Varma D. S.
Published: April 2003

The paper deals with the synthesis and characterization of seven polypyromellitimide samples having varying contents of phosphine oxide and ether linkages in the backbone with pendant maleimido groups. Curing characteristics and thermal stability of polymers were evaluated by differential scanning calorimetry and dynamic thermogravimetry. It was observed that an increase in pendant maleimido groups resulted in an increase in the heat of polymerization. Char yield also increased with increase in phosphorus content. Conductivity and dielectric parameters were also evaluated. The mechanism of conduction was found to be a combination of electronic and ionic type.
Sulfonated polyisobutylene telechelic ionomers. XIV. Viscoelastic behavior of concentrated solutions in nonpolar solvents
Authors: Tant Martin R. , Wilkes Garth L. , Kennedy Joseph P.
Published: April 2003

The effect of molecular variables upon the dynamic viscoelastic behavior of solutions of sulfonated polyisobutylene telechelic ionomers in nonpolar solvents has been investigated. Intermolecular association of the ionic end groups in nonpolar media results in the formation of a transient ionic network which displays a viscous response at low frequencies and an elastic response at high frequencies. The frequency of the transition from viscous behavior to elastic behavior, as well as the plateau storage modulus, is dependent upon molecular variables such as architecture, molecular weight, neutralizing cation, and extent of neutralization. Variables which affect the strength of the ionic interactions, such as temperature and the type of solvent, also influence the viscoelastic response. Solutions of ionomers neutralized with cations of Groups IA and IIA, such as potassium and calcium, behave elastically over most of the experimentally accessible frequency range, while those neutralized with transition metals, such as zinc, display viscous flow over a rather wide range at low frequencies. As in previous studies of dilute solution viscosity behavior, the threearm star trifunctional species was found to form a more extensive network in nonpolar solvents than the linear difunctional species at equivalent concentrations. The failure of time–temperature superposition indicates that these solutions are thermoheologically complex.