bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation‐grafted polymers for biomaterial applications. II. The morphology and structure of 2‐hydroxyethyl methacrylate and ethyl methacrylate homopolymer grafts
Authors: Cohn Daniel , Hoffman Allan S. , Ratner Buddy D. 
Published: April 2003

AbstractThe 2‐hydroxyethyl methacrylate (HEMA)/ethyl methacrylate (EMA) graft copolymer system has been found to be a useful model for investigating blood/polymer interactions. Studies of the structure of both HEMA and EMA radiation‐grafted regions were conducted using extraction methods and transmission electron microscopy of selectively stained HEMA grafts. The effect of the extraction procedure on the surface topography of HEMA‐ or EMA‐grafted films was studied by means of scanning electron microscopy. The existence of internal cells in the bulk of the HEMA network was demonstrated, and their osmotic nature was investigated. As grafting proceeds, the HEMA network becomes increasingly porous. The extraction studies carried out on EMA grafted showed that with this system an increasingly dense structure is obtained as grafting proceeds.
Near infrared measurements of terminal epoxides in polymer resin systems. I. Analytical considerations
Authors: Peck M. C. Paputa , Carter R. O. , Qaderi S. B. A. 
Published: April 2003

AbstractTerminal epoxides display a group specific near infrared absorption at 4532 cm−1. This combination tone is reasonably free of interferences and can be employed to measure oxirane ring concentrations for epoxy coating resin systems during synthesis and crosslinking. With the use of low signal‐to‐noise FTIR supported by computer data manipulation, chloroform solutions of five commercially available resins were analyzed for epoxide equivalent weight and correlated with results obtained by perchloric acid titrations. The near infrared technique displays linearity for epoxy concentrations of 3.6–20.7 meq/L. Similar results were obtained via a serial concentration study, indicating that the technique is not strongly affected by matrix effects.
Birefringence of a polymeric cholesteric liquid crystal measured by refractometry
Authors: Laivins G. V. , Gray D. G. 
Published: April 2003

AbstractThe Abbé refractometer provides a convenient way to measure the refractive indices and birefringence of polymeric liquid crystalline solutions. The cholesteric mesophase formed by (acetoxypropyl) cellulose and its solutions in dibutyl phthalate were examined at 26°C and 50°C. The measured refractive indices were dependent on the direction of shear when the polymer was applied to the refractometer plates. The initial shear‐induced nematic‐like order relaxed slowly to the equilibrium planar cholesteric structure. The refractive index for the isotropic solutions and the two refractive indices for the anisotropic solutions all varied linearly with polymer concentration, and the width of the intermediate two‐phase region was readily determined. The changes in refractive index with polymer concentration and with orientation on the refractometer plate were rationalized with a simple model of the cellulosic mesophase, and an order parameter of 0.7 was estimated. The layer birefringence calculated from optical rotatory dispersion measurements of the cholesteric reflection band intensity was in good agreement with the birefringence measurements.
Effect of triallyl cyanurate on the properties of bis‐maleimide resins
Authors: Varma Indra K. , Gupta S. P. , Varma D. S. 
Published: April 2003

AbstractThis paper describes the improved processibility of 4,4'‐bis‐maleimidophenyl methane (BM) chain extended by 4,4'‐diaminodiphenyl methane (DADPM) by coreaction with triallyl cyanurate (TAC). Curing of BM, chain‐extended BM, and mixture of BM and DADPM (1 : 0.3 molar ratio) in the presence of 5, 10, 15, and 20% (w/w) of TAC was followed by differential scanning calorimetry (DSC) and thermal stability of cured resins was evaluated by thermogravimetric analysis. TAC had insignificant effect on char yield (at 800°C) of BM resin. Glass‐ and graphite fabric‐reinforced composites were fabricated using chain‐extended BM containing 10% TAC and methyl ethyl ketone (MEK) as solvent. Interlaminar shear strength was found to be 7620 psi for graphite fabric laminate containing 40% resin. Good retention of mechanical properties of laminates at 220°C up to 320 h was observed.
Latex interpenetrating polymer networks based on acrylic polymers. III. Synthesis variations
Authors: Hourston D. J. , Satgurunathan R. , Varma H. 
Published: April 2003

AbstractTwo latex interpenetrating polymer networks, one from a supposedly compatible pair and the other from an incompatible pair of polymers, were prepared by two‐stage emulsion polymerization. The synthesis conditions in each case were varied by altering the ratio of the glassy polymer to the rubbery polymer and also by reversing the order of synthesis. Fabricated samples of these latex interpenetrating polymer networks were subjected to hardness, stress‐strain, and dynamic mechanical measurements. Hardness and stress‐strain measurements showed that, although the second formed polymer dominated the final mechanical properties, the compatibilities of the polymer pairs played an important role. Dynamic mechanical analysis for the inverse systems showed evidence of enhanced mixing.
Graft copolymerization of styrene onto ethylene‐vinyl p‐nitrobenzoate copolymer by chain transfer reaction
Authors: Nakamura Shigeo , Kasatani Hideo , Matsuzaki Kei 
Published: April 2003

AbstractThe effect of steric hindrance on the attack of growing polymer radicals to the reaction sites on a trunk polymer was examined in the graft copolymerization of styrene onto a trunk polymer with pendant aromatic nitro groups by chain transfer reaction of growing polymer radicals to the pendant nitro groups. The nitro groups on ethylene‐vinyl p‐nitro benzoate copolymer (EVNB) are more effectively utilized in the graft copolymerization than those on the vinyl p‐nitro benzoate homopolymer (PVNB) previously used as a trunk polymer, because the nitro groups are distributed less frequently on the trunk polymer in the former than in the latter. This was also confirmed by the higher chain transfer constant of growing polystyrene radicals to EVNB compared to that of PVNB.
Synthesis, characterization, properties, and derivatives of poly(starch‐g‐(1‐amidoethylene)). I. Synthesis and characterization
Authors: Meister John J. , Sha Mu Lan 
Published: April 2003

AbstractPoly(starch‐g‐(1‐amidoethylene)) can be formed by aqueous, free radical polymerization of 2‐propenamide on lintnerized, potato starch. Initiation is by attack of cerium ions (+IV) on the D‐glucopyranosyl units of starch. The reaction produces a water‐soluble thickener with molecular properties of the product controlled, in part, by the gel effect induced in virtually all syntheses. Yield of product varies from 38 to 100% with yields of 90–100% being common. Products containing less than 50 wt % sidechain were found to be difficult to dissolve once they were recovered from the synthesis mixture. A sample with a design molecular weight of 0.8 × 106 and 4 grafts per backbone formed 3.9 wt % of a water‐insoluble solid in the reaction mixture. The solid, which had a composition similar to that of the reaction mixture, may be the result of selective reaction within the distribution of backbone molecules.
Thermal properties of rigid polymers. I. Measurement of thermal conductivity and questions concerning contact resistance
Authors: Hall J. A. , Ceckler W. H. , Thompson E. V. 
Published: April 2003

AbstractSeveral studies of the influence of contact resistance on the measurement of thermal conductivity of polystyrene using a steady‐state device are presented. In each case it is seen that, although this influence can perhaps be minimized, it cannot be eliminated as an experimental complication. A novel technique is then described which does eliminate entirely contact resistance as a variable, and this technique is shown to yield an unequivocal value of thermal conductivity.
Calorimetric quality control of UV cured optical fiber‐coatings
Authors: Nicolais L. , Apicella A. , Grimaldi P. 
Published: April 2003

AbstractThe application of ultraviolet (UV)‐curable polymeric coatings provides optical fibers with improved strength, microbending resistance, and long‐term durability. To ensure constant optical properties of the glass fibers during their life, fully polymerized coatings are needed. Test methods capable of determining the degree of cure and the consistency of the polymeric materials used are therefore required by the fiber technology. This investigation deals with the description of a calorimetric test method for the direct determination of the prepolymer reactivity and its final degree of cure. The analytical technique uses a modified differential scanning calorimeter (DSC) capable of direct measurements of heat fluxes generated during the UV‐activated polymerization of photoinitiated acrylic prepolymers. Finally, the degree of cure and the glass transition temperatures were determined for the polymerized coating also in presence of sorbed moisture.
Photoprotective agents for wool. Synergism between UV absorbers and antioxidants
Authors: Carr C. M. , Leaver I. H. 
Published: April 2003

AbstractSeveral antioxidants alone, and in combination with sulfonated UV absorbers, have been evaluated as photoprotective agents for wool. Mixtures of phenolic antioxidants and sulfonated UV absorbers of the 2‐hydroxyphenylbenzotriazole class were found to exhibit synergistic behavior; the most effective UV absorber also gave the strongest synergistic effect with the antioxidants. Of the systems studied, the hindered phenol, calcium bis ((ethyl‐(3,5‐di‐t‐butyl‐4‐hydroxybenzyl)‐phosphonate)) (Irganox 1425), when used in conjunction with a sterically hindered benzotriazolesulphonate, afforded wool the best protection against photoyellowing and phototendering in sunlight, behind window glass. Sulfonated derivatives of hindered phenols acted synergistically with UV absorbers when treated fabrics were exposed to an artificial light source, but not when fabrics were exposed to sunlight through glass.
Mercerized and cross‐linked cotton yarns I. Effect of tension during mercerization on degree of cross‐linking and distention index
Authors: Pandey S. N. , Nair Prema 
Published: April 2003

AbstractA study of the effect of tension during mercerization on the distention index and distribution of cross‐link in cotton yarns cross‐linked by different processes with formaldehyde is reported. The yarns were slack mercerized and then restretched to 90–103% of their original lengths. The mercerized samples were then cross‐linked with formaldehyde by form W and form D processes. Estimation of sol‐gel, distention index (DI), and distribution of cross‐links in cotton yarn samples are discussed. The results of these analyses provide important information on the gross uniformity of the distribution of the cross‐link in the fiber structure of cotton yarn mercerized under varying tensions and cross‐linked.
The crystallization and formation of cluster of ethylene ionomer during physical aging
Authors: Kohzaki Mamoru , Tsujita Yoshiharu , Takizawa Akira , Kinoshita Takatoshi 
Published: April 2003

AbstractThe effect of the physical aging of ethylene ionomers was studied for the samples with the acid content of 5.4 mol%, and the degree of neutralization, 0%, 60% Na, 60% Zn, and 90% Zn. The information about the crystal and the cluster part of the physically aged ionomers was obtained by differential scanning calorimetry and by dynamic viscoelastic measurements, respectively. The degree of crystallinity and the dynamic modulus for the ionomers of the degree of neutralization 0%, 60% Na and 60% Zn increased gradually with the aging time; on the other hand, the crystallinity of 90% Zn remained constant and the modulus at 100°C increased to a certain value up to a period of 100 h, but thereafter the crystallinity increased remarkably and the modulus remained. These facts indicate that the crystallization of neutralized ethylene ionomer starts after clustering and the clustering would finish at early stage of the physical aging for intermediately neutralized ethylene ionomer. The physical aging effect of the ethylene ionomers was, thus, found to be important to material design.
Bulk functionalization of ethylene‐propylene copolymers I. Influence of temperature and processing on the reaction kinetics
Authors: Greco R. , Maglio G. , Musto P. V. 
Published: April 2003

AbstractThe dicumylperoxide (DCPO) promoted functionalization of an ethylene‐propylene copolymer (EPR) by means of dibutyl meleate (DBM) has been studied in bulk at constant reactant composition (100 : 10 : 1 by wt EPR‐DBM‐DCPO) in the range of temperature from 140 to 200°C. The reactants have been premixed in a Brabender‐like apparatus at 90°C in which no decomposition of the radical initiator could occur. This was done in the frame of a general discussion of polyolefin functionalization, to assure the homogeneity of the reactant mixture before the reaction occurred.The kinetics of the reaction followed by an infrared (IR) technique was carried out according to two different procedures: a static one in a thermostatic bath and a dynamic one in the same mixer used for the premixing step. The kinetics in the two cases are very comparable, and a common activation energy of 40 kcal/mol has been measured. Some minor differences exist, however, which are very interesting from a scientific point of view.The kinetics of EPR degradation during the reaction has been indirectly monitored by means of solution viscosimetry. The results have been compared with the reaction kinetics.A thorough discussion of the proposed mechanism for grafting and degradation reactions has been also provided.Further work is in progress to analyze the effect of the EPR copolymer and of reactant composition on the functionalization and degradation reactions.
Elastomeric domain‐type interpenetrating polymer networks
Authors: Silverstein M. S. , Narkis M. 
Published: April 2003

AbstractElastomeric latex interpenetrating polymer networks (IPNs) can result from a two‐stage emulsion polymerization procedure in which styrene is polymerized and cross‐linked on a lightly cross‐linked polyacrylate (PA) seed latex in a ratio of 75 : 25 PA‐PS. The multiphase nature of these IPNs is indicated by two distinct Tgs and is confirmed by cold‐stage transmission electron microscopy and by the unique mechanical and rheological properties that are intimately related to the material's structure. PS microdomains reinforce the elastomeric PA, yielding a significant modulus, and interparticle PS physical ties yield a significant ultimate tensile strength. The elastomeric latex IPN's dual thermoset‐thermoplastic nature is revealed in a stick, slip, roll flow mechanism of the cross‐linked submicrometer particles, which can be injection molded as a thermoplastic. The relationships among the polymerization procedure, the structure, and the physical properties are characterized by the examination of several different materials using a variety of analytic techniques.
Properties of cotton fibers containing the cellulose IV crystal structure
Authors: Zeronian S. Haig , Ryu Hyo‐Seon 
Published: April 2003

AbstractComplete conversion of the crystal form in cotton fibers to cellulose IV (cell IV cotton) was obtained by heat treatment of ethylamine‐treated cotton cellulose in either saturated steam or formamide. Degradation of the fibers was not extensive during the conversion process; oxidative damage appeared to have been confined primarily to the accessible regions of the fibers. Examination by scanning electron microscopy indicated that the surface of the cell IV cotton was smoother than that of the same cotton with other crystal forms, namely, the starting cotton (cell I cotton), mercerized cotton (cell II cotton), and ethylamine‐treated cotton (cell III cotton). Fiber accessibility increased in the order cell I cotton < cell III cotton ≤ cell IV cotton < cell II cotton. Using leveling‐off degree of polymerization as the measure, it appeared that the lengths of the crystallites in cell I cotton were much higher than those in cell II, III, and IV cotton. The strength of cell IV cotton was comparable to that of cell I cotton even though its degree of polymerization was significantly lower. It is suggested that heat treatments in formamide have an annealing effect on cotton that results in increases of strength.
Mass spectrometric studies of sulfonyl esters of diazonaphthalenones: Relationship between fragmentation patterns and photolithographic mechanisms
Authors: Sorbier B. M. Du , Kulkarni S. , Vouros Paul , Kirby D. P. 
Published: April 2003

AbstractEsters of 2‐diazonaphthalenone sulfonic acid were examined by mass spectrometry using electron impact and chemical ionization techniques. Charactristic differences in the fragmentation patterns of positional isomers have been observed. In a manner analogous to photo‐induced decompositions, the diazoketo functional groups fragment by elimination of N2 to form an indenoketene ion. An alternative process involves the apparent loss of 26 mass units from the molecular ion. The latter process is explained by evoking the abstraction of two hydrogen atoms following the loss of N2. With deuterium isotope labeling, it has been shown that the hydrogens are abstracted from the surface of the probe tip used for introduction of the samples into the mass spectrometer. It is concluded that an environment rich in hydrogen or proton‐donating properties promotes and enhances the incorporation of the hydrogen atoms and formation of the [M‐26] species at the expense of the ketene moiety, which is an important intermediate in the photoresist process. By extrapolation it may be inferred that the efficiency of the photolithographic process could be influenced by the availability of protons in the photoresist matrix.
Thioxanthone derivatives as photoinitiators in micelle photopolymerization
Authors: Fouassier Jean‐Pierre , Lougnot Daniel‐Joseph 
Published: April 2003

AbstractThis paper provides a complete survey of the primary processes involved in typical oil‐and water‐soluble thioxanthane derivatives dissolved in sodium dodecyl sulfate micelles, in the presence of monomers and amines. Special emphasis is laid on the determination of the rate constants of the different processes and the absorption spectra of the transients. Relevant data are shown and discussed with reference to the effectiveness of these molecules as photopolymerization initiators.
Divinylbenzene‐crosslinked terpolymer consisting of hemin, styrene, and 2‐methyl‐5‐vinylpyridine as cyanide ion exchanger. Preparation of the polymer in the form of beads by suspension polymerization
Authors: Kokufuta Etsuo , Saito Kiyoshi 
Published: April 2003

AbstractBead‐shaped, divinylbenzene‐cross‐linked terpolymers, consisting of hemin (ferri‐protoporphyrin IX chloride), styrene, and 2‐methyl‐5‐vinylpyridine, were prepared by suspension polymerization in which all or part of styrene monomer was replaced with divinylbenzene. Analogous terpolymers of the cross‐linked and uncross‐linked formless types were also prepared by solution polymerization. All the terpolymers obtained were characterized by electron spin resonanance spectroscopy, scanning electron microscopy, and measurement of specific surface area. The characteristic of the adsorption of cyanide ion onto the terpolymer beads was investigated and compared with those adsorbed onto their analogs. The column separation of cyanide ion with the terpolymer beads was carried out to examine the ion‐adsorbing capacity. It was found that the suspension polymerization is just appropriate to prepare a cyanide ion exchanger in the form of beads.
Laser pyrolysis of characterized cyanurate network polymers
Authors: Cozzens Robert F. , Walter Peter , Snow Arthur W. 
Published: April 2003

AbstractA series of bisphenol A dicyanate network polymers with degree of crosslinking varied by addition of 4‐cumylphenylcyanate were prepared and characterized by model compound study, infrared spectroscopy, DSC, TGA, and statistical analysis. Laser ablation energy measurements varied from 14 to 18 kJ/g and were found to linearly increase with degree of crosslinking. Comparative ablation energy analysis was made with other aromatic, nonaromatic, linear, and crosslinked polymers.
Mechanical behavior of quenched isotactic polypropylene crystallized by thermal and solvent treatments
Authors: Candia F. De , Russo R. , Vittoria V. 
Published: April 2003

AbstractFilms of quenched isotactic polypropylene were either annealed at 80, 90, 100, 110°C for 30 min or kept in different liquids for 24 h at 25°C. The liquids were cyclohexane, chloroform, and carbon tetrachloride. Both treatments induce crystallization of quenched films and the development of crystallinity was detected by carrying out density and wide‐angle x‐ray scattering measurements. Small‐angle light scattering experiments, performed on the starting and on the crystallized samples, show that in the zones in which spherulites are present the basic gross morphology does not change after the treatments, although the increase of crystallinity is substantial for all the samples. The analysis of the mechanical behavior also indicates the absence of relevant morphological changes following the different treatments. On the other hand the increased crystallinity strongly influences the complex structural and molecular rearrangement characterizing the transition from the spherulitic to the fiber morphology. The results are discussed in terms of the great significance that structural modifications have on the physical properties.
Graft copolymerization of methyl methacrylate on holocellulose
Authors: Okieimen E. F. , Idehen K. I. , Ahiedu H. 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate initiated by ceric ion in aqueous medium on bleached holocellulose was studied at 29°C. It was found that an increase in the concentration of ceric ion and oxidation of the holocellulose with aqueous potassium dichromate solution resulted in increased levels of incorporation of poly(methyl methacrylate) graft copolymer, but were associated with reductions in the efficiency of grafting. Thiol groups were introduced on the holocellulose by treatment with dilute thioglycollic acid solutions at 29°C. The influence on the level of grafting and on the molecular weight of the grafted polymer by the incorporated thiol groups on the substrate was examined.
New aspects in cationization of lignocellulose materials. IX. Flame retardancy effect of modification with nitrogen and sulfur containing groups
Authors: Šimkovic Ivan , Pastýr Jan , Antal Miroslav , Balog Karol , Košik Štefan , Plaček Jan 
Published: April 2003

AbstractLignocellulose materials were modified with 3‐chlor‐2‐hydroxypropyltrimethylammoniumchloride, 1,3‐bis(3‐chlor‐2‐hydroxypropyl)imidazoliumhydrogensulphate, and 2‐chlorethyl‐sodiumsulphonate and the flame‐retardant properties of materials obtained were studied. The flame‐retardant effect was proved using the limited oxygen index (LOI) method and values up to 32.8 vol % of oxygen were determined. The LOI values were higher when the modification was done without using NaOH for activation, but in that case the alkylating groups were not chemically bonded to the material. The NaOH activation was necessary to obtain material with flame‐retardant properties stable against washing. No synergistic effects were observed when the material was modified with both nitrogen‐ and sulfur‐containing groups.