bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biocidal polymers active by contact. II. Biological evaluation of polyurethane coatings with pendant quaternary ammonium salts
Authors: Nurdin N. , Helary G. , Sauvet G. 
Published: April 2003

AbstractFilms of polyurethane were prepared by reaction of hydroxytelechelic polybutadienes carrying covalently bound quaternary ammonium salts with an aliphatic triisocyanate. These coatings exhibited high biocidal activity against Gram‐positive and Gram‐negative bacteria, yeasts, and moulds. It was found that many parameters controlled the bioactivity such as the time of contact between films and bacteria, the [NCO]/[OH] ratio used to prepare the cured polyurethane, the concentration of quaternary ammonium salts in the coating, and the length of the alkyl chain from C8 to C16 linked to the quaternary nitrogen atom. A secondary phenomenon of diffusion only observed with the shorter alkyl chains (C8 and C10) was shown to be due to synthesis residues. After these water‐soluble impurities are eliminated, the biocidal activity remains excellent: then it is due only to a contact polymer bacteria. © 1993 John Wiley & Sons, Inc.
Solubility characteristics of poly(4‐methyl‐1‐pentene)
Authors: Beck H. N. 
Published: April 2003

AbstractRelative solubility determinations in over 50 compounds have identified numerous good solvents as well as nonsolvents for poly(4‐methyl‐1‐pentene) (TPX) at elevated temperatures. The better solvents include hydrocarbons and esters that contain significant amounts of aliphatic or cycloaliphatic character. Equilibrium phase‐transition temperatures for dissolution upon heating and phase separation upon cooling were determined by a hot‐stage light microscopic method. The significance of the results is related to the ability to determine precisely the relative solvent power of different solvents and related to the preparation of permselective membranes from the polymer solutions. © 1993 John Wiley & Sons, Inc.
Study of solution properties of poly(α‐methyl styrene) in various solvents by dilute‐solution viscometry
Authors: Chee K. K. , Ng S. C. 
Published: April 2003

AbstractThe values of Mark–Houwink–Sakurada constants were determined for poly(α‐methyl styrene) (PαMs) of high and low molecular weights in a variety of solvents by a new approach, which requires only polydisperse samples. The results are in accord with those reported in the literature. In addition, the present work reports the values of the Flory interaction parameter for PαMs in 13 solvents of distinct solvent power at various temperatures. Three refined methods pertaining to both polar and nonpolar solvents were applied to estimate the solubility parameter (δ2) of PαMs resulting in δ2 = 18.75 ± 0.15 (J/mL)1/2 at 30°C. Finally, the scatter data of the Huggins coefficient over a range of expansion factors varying from 0.7 to 2.6 seem to conform better to a newly proposed empirical equation than to the contemporary model after Imai. © 1993 John Wiley & Sons, Inc.
Effects of surface roughness and the chemical structure of materials of construction on wall slip behavior of linear low density polyethylene in capillary flow
Authors: Chen Yuhming , Kalyon Dilhan M. , Bayramli Erdal 
Published: April 2003

AbstractThe presence of wall slip during the flow of polymeric melts has significant ramifications on the melts' processability. In this study, the effects of materials of construction and surface roughness on the wall slip behavior of a linear low density polyethylene were investigated, using capillary flow. Capillaries, constructed from copper, stainless steel, aluminum, and glass, were used. The inner surface roughness of the capillaries were characterized by the employment of a profilometer and scanning electron microscopy. The roughness profiles of copper capillaries were also altered by the employment of chemical etching. Using Mooney's analysis, the wall slip velocity values were determined to be in the range of 0.09 to 1.34 mm/s. The wall slip velocity values were the highest for stainless steel and were negligible for aluminum. The relative work of adhesion values of polyethylene were the smallest for stainless steel and copper and the highest for glass. Overall, the wall slip velocity values increased with decreasing surface roughness of the capillaries and with decreasing work of adhesion. © 1993 John Wiley & Sons, Inc.
A kinetic scheme for anhydride curing of diglycidyl ester with tertiary amine as catalyst
Authors: Khanna Umang , Chanda Manas 
Published: April 2003

AbstractA kinetic model has been developed on the basis of reaction mechanisms proposed for the anhydride curing of diepoxides, using tertiary amine as catalyst. The model has been tested for the cure reaction of a diglycidylester model compound, bis‐(2,3‐epoxypropyl)‐1,3‐benzenedicarboxylate, with hexahydrophthalic anhydride as the curing agent and benzyldimethylamine as the catalyst, over the temperature range 100–120°C, the rate being measured by means of differential scanning calorimetry, using an isothermal approach. The rate expressions derived for the model are half order and first order, with respect to reacted and unreacted functional groups, respectively, in the initial stage. For the later stage of curing, up to the point of vitrification, the model indicates a 1.5 order with respect to the unreacted functional groups. These are in good agreement with the kinetic orders of 0.5 and 1.5, with respect to reacted and unreacted functional groups, respectively, reported earlier from a phenomenological approach for the whole range of curing prior to the onset of vitrification. © 1993 John Wiley & Sons, Inc.
The temperature dependence of the doolittle equation parameter for polymer liquids
Authors: Lee Myung Ho , Han Do Hung , Cho Bongkee 
Published: April 2003

AbstractThe Doolittle equation parameter for polymer liquids is a function of temperature. Its dependence on temperature can be expressed by a quadratic equation. The constants in the equation are determined for four vinyl‐type polymer liquids: polystyrene (PS), poly(vinyl acetate) (PVAc), polydimethylsiloxane (PDMS), and polyisobutylene (PIB). It was found that the Doolittle parameter decreases with increasing temperature. Equations are presented for the pressure and temperature coefficients of viscosity, isoviscous temperature coefficient of volume, and the constant Km in the Miller equation. Comparisons of the predictions of the equations, with those in the literature, are favorable. © 1993 John Wiley & Sons, Inc.
Formation of microporous polymer fibers and oriented fibrils by precipitation with a compressed fluid antisolvent
Authors: Dixon David J. , Johnston Keith P. 
Published: April 2003

AbstractPolymer morphology is controlled over a continuum from microspheres to interconnected bicontinuous networks to fibers with a versatile new process: precipitation with a compressed fluid antisolvent. The results are explained qualitatively as a function of phase behavior, mass‐transfer pathways, and the formation rates of skin on the flowing jet. By spraying dilute polystyrene in toluene solutions into liquid carbon dioxide, extremely small 100 nm microspheres are formed. For concentrations above the critical composition, fibers are produced that are not only microcellular, but, in some instances, even hollow. Mass‐transfer pathways that cross the binodal near the critical composition produce interconnected networks, likely due to spinodal decomposition. In this region, fibers composed of highly oriented microfibrils are produced at high shear rates. Preaddition of CO2 influences the morphology because of dilution, in a similar manner as a liquid antisolvent, except that the viscosity reduction is larger due to added free volume. Because CO2 diffuses through the glassy polystyrene skin faster than does a conventional liquid antisolvent such as methanol, it produces more porous fibers, which are also more cylindrical. © 1993 John Wiley & Sons, Inc.
Further studies on biodegradation of aliphatic poly(ester‐amides)
Authors: Chen X. , Gonsalves K. E. , Cameron J. A. 
Published: April 2003

AbstractTwo types of aliphatic poly(ester‐amides) (PEAs) were subjected to microbial degradation in basal mineral salt broth, under the attack of a yeast, Cryptococcus laurentii, at 20°C. PEA‐I copolymers were made by the anionic ring‐opening copolymerization of ϵ‐caprolactone and ϵ‐caprolactam, whereas PEA‐II copolymers were synthesized by a two‐step polycondensation reaction of hexanediol‐1,6, hexanediamine‐1,6, and adipolyl chloride. These copolymers were found to be readily degradable under biotic conditions, based on weight loss, GPC, NMR spectroscopy, and tensile property measurements. Compared to abiotic hydrolysis, biodegradation occurred much faster under milder conditions. Furthermore, NMR spectroscopic analysis proved that the biodegradation of poly(ester‐amides) involves the enzymatic hydrolysis of ester groups on the backbones of polymers into acid and hydroxyl groups. No breakdown of amide bonds was observed under the given biotic conditions. © 1993 John Wiley & Sons, Inc.
Synthesis and properties of multiacrylic resins from epoxy resins
Authors: Boutevin B. , Parisi J. P. , Robin J. J. , Roume C. 
Published: April 2003

AbstractThe action of methacrylic acid onto tetraglycidyl methylene dianiline, tetraglycidyl sulfone dianiline, triglycidyl triphenylmethane (TACTIX), and epoxy novolac resins was performed using different catalysts. In each case, a comparative study of these catalysts was investigated depending upon the polarity of the solvent and of the temperature. Chromium complexes are better in low polar solvents. The reactions were monitored by 1H‐NMR, by epoxide titration, and by size exclusion chromatography (SEC), and the reactivity of these resins could be compared. Finally, the study of these materials obtained after radical and photochemical cross‐linking, especially by dynamic mechanical analysis (DMA), shows that these materials exhibit high Tg's (200°C for methacrylated TACTIX) compared to those of the corresponding multiepoxides cured by diamines. © 1993 John Wiley & Sons, Inc.
Proton exchange membranes by radiation grafting of styrene onto FEP films. I. Thermal characteristics of copolymer membranes
Authors: Gupta B. , Scherer G. G. 
Published: April 2003

AbstractThermal behavior of radiation‐grafted and sulfonated poly(tetrafluoroethylene‐hexafluo‐ropropylene)‐g‐polystyrene membranes was evaluated using thermogravimetric analysis. A three‐step degradation pattern was observed from thermograms of all the membranes and was attributed to the dehydration, desulfonation, and degradation of the FEP backbone. The evidence for desulfonation was reflected in the loss in ion exchange capacity of the heat‐treated samples. The membranes were found to undergo loss in ion exchange capacity beyond ∼ 200°C. No trace of sulfonic acid groups as the ion exchange sites was found above ∼ 350°C. The swelling of heat‐treated membranes was also reduced considerably. However, the loss in swelling was much higher than that in the ion exchange capacity of the corresponding membrane. The results were explained in terms of cross‐linking reaction occurring in the membrane matrix during the desulfonation process that imparts rigidity in the membrane matrix. © 1993 John Wiley & Sons, Inc.
Solid‐state polycondensation of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. I.
Authors: Karayannidis George P. , Kokkalas Demetris E. , Bikiaris Demetris N. 
Published: April 2003

AbstractPoly(ethylene terephthalate) (PET), taken from postconsumer soft‐drink bottles, was subjected to solid‐state polycondensation, as received or after dissolution in various solvents and precipitation in methanol. The solvents used were: benzyl alcohol, phenol/tetrachloroethane 60/40, or o‐chlorophenol. The effect of various reaction parameters, such as reaction temperature (180, 200, 220, and 230°C), and time on intrinsic viscosity [η] and carboxyl and hydroxyl end‐group content have been investigated. During the solid‐state polycondensation of PET that was used as received, both esterification and transesterification took place at all temperatures, while in PET samples, used after dissolution, the transesterification was observed only at 230°C. The highest number average molecular weight, Mn = 60,200, was obtained from PET with initial Mn = 20,300, dissolved in o‐chlorophenol, after solid‐state polycondensation at 230°C for 8 h. © 1993 John Wiley & Sons, Inc.
Photodegradation of polymer materials containing flame‐cut agents
Authors: Torikai Ayako , Kato Hitoshi , Fueki Kenji , Suzuki Yuji , Okisaki Fumio , Nagata Masatoshi 
Published: April 2003

AbstractPhotodegradation of incombustible materials [polystyrene (PSt) and polypropyrene (PP) containing 2 wt% of decabromodiphenyl oxide (DBDE) or tetrabromobisphenol‐A (TBA) as a flame‐cut agent] were studied using Okazaki Large Spectrograph (OLS). Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm, UV‐visible spectra and FTIR spectra were measured to identify the chemical structural changes of the polymers. Number of chain scissions, which is a measure of the polymer degradation, was estimated from the results of GPC measurements. It was found that the photostability of PP and PSt was reduced by the addition of DBDE or TBA. Photodegradation of these polymers took place by the irradiation of the light of wavelengths lower than 320 and 360 nm for the polymers containing TBA and DBDE, respectively. The most effective irradiation wavelengths for main chain scission are found to be 260–280 and 300 nm for PP or PSt–TBA samples and PP or PSt–DBDE samples, respectively. © 1993 John Wiley & Sons, Inc.
Sorption of aromatic compounds in water using polymer sorbents containing amino groups
Authors: Martel Bernard , Morcellet Michel 
Published: April 2003

AbstractPorous organic sorbents containing primary amino groups and crosslinked with divinylbenzene or ethyleneglycol dimethacrylate were used for the recovery of various organic pollutants from aqueous solutions. The kinetics of sorption of these solutes is dependent on the specific area and the average pore radius of the sorbent. Physical sorption and chemical interaction of the acid solutes with the amino functions are both involved in the sorption process. The variation of the sorption capacity with the specific area of the solute depends on the nature of the solute. Experiments with mixtures of organic solutes show that the sorption of a given solute may be increased or decreased by the presence of another one. The capacity is increased during cycles of using and regenerating the sorbent. © 1994 John Wiley & Sons, Inc.
Fibers from DMAc‐LiCl solutions of steam exploded wood
Authors: Focher B. , Marzetti A. , Conio G. , Marsano E. , Cosani A. , Terbojevich M. 
Published: April 2003

AbstractPoplar wood was steam exploded under various experimental conditions (230°C, 120–360 sec) and was then dissolved in dimethylacetamide‐lithium chloride (DMAc‐LiCl). Solutions of different concentrations (cp 4–10%) were obtained without any activation. Mesophases were not formed in any of the conditions tested. The good spinnability of the solutions led to wood fibers that were evaluated in terms of physico‐mechanical properties and morphological and supramolecular characteristics. The tensile strength and the modulus of the wood fibers, improved through delignification treatments, were comparable to those of conventional rayons. After annealing treatments at 260°C in protic solvent, X‐ray and CP MAS 13C–NMR experiments revealed evidence of a marked modification of the fiber supramolecular structure. © 1994 John Wiley & Sons, Inc.
Effect of E/P ratio and VA content on flow behavior of EPDM and EVA blends
Authors: Ghosh M. K. , Das C. K. 
Published: April 2003

AbstractThe effect of E/P ratio of EPDM rubber and VA content of EVA copolymer on the flow behavior along with the extrudate morphology of EVA and EPDM blends have been studied as a function of shear rate and processing temperature. High E/P ratio EPDM rubber and low VA content EVA render high viscosities to the blend within the temperature range studied. The same trends hold true for extrudate swell. Stored elastic energy and relaxation time are higher for high E/P ratio EPDM and low VA content EVA. However, compositions with low E/P ratio EPDM exhibit higher shear modulus. At a particular blend composition these rheological parameters show a change in their pattern. Melt fracture occurs to a larger extent for the high E/P ratio EPDM in its blend with low VA content EVA. © 1994 John Wiley & Sons, Inc.
Preparation and application of low molecular weight poly(vinyl chloride). I. Preparation and thermal stability
Authors: Yamamoto Kikuo , Maehara Takashi , Mitani Katsuo , Mizutani Yukio 
Published: April 2003

AbstractPoly(vinyl chloride) with relatively low molecular weight (LMW‐PVC) was prepared by suspension polymerization in the presence of some chain‐transfer agents, such as mercapto compounds. It is elucidated by means of thermogravimetry, dehydrochlorination, color difference, and discoloration that the resultant LMW‐PVC has good thermal stability. The degree of dehydrochlorination of the LMW‐PVC obtained by using n‐dodecylmercaptan increases with increasing the content of component from the chain‐transfer agent. It is found that the LMW‐PVC obtained by using mercapto compounds shows better thermal stability (discoloration property) than does the one obtained without using these agents, at the same weight‐average polymerization degree. © 1994 John Wiley & Sons, Inc.
An FTIR solid‐state analysis of the diffusion of hindered phenols in low‐density polyethylene (LDPE): The effect of molecular size on the diffusion coefficient
Authors: Möller Kenneth , Gevert Thomas 
Published: April 2003

AbstractLow‐density polyethylene (LDPE) has been investigated with respect to the diffusion of hindered phenol antioxidants added to the polymer matrix. In the study, a simple method was used to measure the diffusion coeficient, with the aid of FTIR spectroscopy without any extraction or refining steps in the analysis. The diffusion coefficient, D, of five phenols containing the same 3(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) structure but with different lengths of the hydrocarbon tail were obtained in the temperature range 30–60°C. The number of carbon atoms in the tail varied between 1 and 18. It was found that the logarithm of D decreased linearly with increasing molecular size. The temperature‐dependence of the phenols could be described by an Arrhenius‐type relationship. It was found that the activation energy, Ed, incresed linearly with increasing molecular size. © 1994 John Wiley & Sons, Inc.
Thermal degradation of segmented polyurethanes
Authors: Petrović Zoran S. , Zavargo Zoltan , Flyn Joseph H. , Macknight William J. 
Published: April 2003

AbstractThermal degradation of polyurethane samples was studied by a thermogravimetric method. The effect of soft‐segment length and soft‐segment concentration on activation energy of the degradation process was measured. Three methods of calculation gave activation energies at different stages of the very complex weight loss process. It was shown that at initial stages of the weight loss the process was dominated by hard‐segment degradation. Activation energy of the whole process calculated by the Ozawa–Flynn method did not offer clear insight into the structure–stability relationship of polyurethanes. The second method showed that activation energy of the initial stage of degradation increased with decrease in hard‐segment length. The Flynn method of calculating activation energy produced fairly constant activation energy of the first 40% degradation, at around 150 kJ/mol, for polymers in the C series. Generally, calculation of kinetic parameters of a complex degradation process as in polyurethanes gives results that are not easy to interpret. It has been shown qualitatively that polymers with higher soft‐segment concentration display lower initial weight loss and higher onset temperatures of degradation. © 1994 John Wiley & Sons, Inc.
Degradation of enhanced environmentally degradable polyethylene in biological aqueous media: Mechanisms during the first stages
Authors: Albertsson Ann‐Christine , Barenstedt Camilla , Karlsson Sigbritt 
Published: April 2003

AbstractDegradation of LDPE films containing a biodegradable starch filler and a pro‐oxidant formulation was performed in aqueous media inoculated with bacteria or fungi at ambient temperatures for 1 year. The samples were characterized with the aim of elucidating the mechanisms that occur during the first stages and that are responsible for initiating the degradation of the LDPE matrix. Two interactive mechanisms were observed: The basal salt medium (water containing trace elements) triggered autoxidation of the pro‐oxidant through decomposition of trace hydroperoxides, which, in synergistic combination with biodegradation of the starch, eventually initiated autoxidation of the LDPE matrix as monitored by chemiluminescence (CL), differential scanning calorimetry (DSC), and confocal scanning laser microscopy (CSLM). The length of the induction period was dependent on the sample thickness and on the activity of the microbiological system. Up to 48% of the starch was consumed during the first year as revealed by polarized‐light microscopy. © 1994 John Wiley & Sons, Inc.
Relationship between superficial response to environmental changes and adhesive property of polyurethane cross‐linked polyacrylate network
Authors: Xu Mei Xuan , Gao Wei , Zhang Wen Hua , Peng Tao , Yao Kang De , Chen Hui Yin , Lu Yin Xian 
Published: April 2003

AbstractA polyacrylic network containing carboxyl groups was cross‐linked with polyurethane. The dynamic contact angles (DCA) on specimens were estimated in water. The effect of ingredient ratio and average molecular M̄n of poly(oxypropylene glycol) (PPG) on DCA were investigated. Data obtained are correlated with 180° peel strength by using the polymer network as an adhesive to adhere both poly(vinyl chloride) (PVC) and polyethylene (PE) film. Results reveal that there is correlation of the surface response to bilateral adhesion of polar and nonpolar substrates. © 1994 John Wiley & Sons, Inc.
Studies on the sulfonation of poly(phenylene oxide) (PPO) and permeation behavior of gases and water vapor through sulfonated PPO membranes. II. Permeation behavior of gases and water vapor through sulfonated PPO membranes
Authors: Fu Hongyong , Jia Lianda , Xu Jiping 
Published: April 2003

AbstractThe permeation behaviors of water vapor and gases were studied for both PPO and SPPO of different sulfonation degree. It was found that the permeability of water vapor increased, and those of oxygen and nitrogen decreased; thus the selectivity for water vapor over gases increased remarkably with the increase of sulfonation degree. The possibility of using SPPO as a gas dehumidification membrane material is discussed. © 1994 John Wiley & Sons, Inc.