bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative rheological characteristics of industrial polyflavonoid tannin extracts
Authors: Garnier S. , Pizzi A. , Vorster O. C. , Halasz L. 
Published: October 2004

AbstractCommercial, industrially produced mimosa, quebracho, pine, and pecan polyflavonoid tannin extracts water solutions of different concentrations were examined by rheometry by measuring dynamic moduli both as a function of strain amplitude and at varying frequency. The water solutions of these materials have been found to behave in general mainly as viscous liquids at the concentrations that are generally used for their main industrial applications. Clear indications of viscoelastic response are also noticeable, among these the crossover of the elastic and viscous moduli curves at the lower concentrations of the range investigated, with some differences being noticeable between each tannin and the others—pine and quebracho tannin extracts showing the more marked viscoelastic behavior. Other than pH dependence (and related structural considerations), the parameters found to be of interest as regards the noticeable viscoelastic behavior of the tannin extracts were the existence in the solutions of labile microstructures that can be broken by applied shear. This is supported by the well‐known thixotropic behavior of concentrated, commercial polyflavonoid tannin extracts water solutions. Such microstructures appear to be due (1) to the known colloidal interactions of these materials already reported, or (b) to other types of secondary interactions between tannin oligomers and particularly between tannin and carbohydrate oligomers. The latter is supported by the dependence of this effect from both the average molecular masses of the tannin and of the carbohydrate oligomers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1634–1642, 2001
Effect of comonomers on the rate of crystallization of PET: U‐turn comonomers
Authors: Connor Daniel M. , Allen Scott D. , Collard David M. , Liotta Charles L. , Schiraldi David A. 
Published: October 2004

AbstractThe effect of incorporating phthalate, 1,8‐naphthalenedicarboxylate, and 1,8‐anthracenedicarboxylate structural units on the crystallization rate of PET are evaluated by isothermal and dynamic calorimetry. Although all of the comonomers retard crystallization, the 1,8‐naphthalene unit shows no concentration dependence between 2.5 and 10% incorporation, in contrast to the smaller phthalate and larger anthracene units. The greater rate at which the 1,8‐naphthalene copolymer crystallizes, relative to that of the other copolymers, is consistent with the notion that the U‐turn geometry induces chain folding and nucleates crystallization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1675–1682, 2001
Release of indomethacin from a novel chitosan microsphere prepared by a naturally occurring crosslinker: Examination of crosslinking and polycation–anionic drug interaction
Authors: Mi Fwu‐Long , Sung Hsing‐Wen , Shyu Shin‐Shing 
Published: October 2004

AbstractNovel chitosan microspheres with lower cytotoxicity were fabricated in this study and their drug release characteristics were investigated. Genipin, a naturally occurring crosslinking reagent that has been used in herbal medicine and in the production of food dye, was used to prepare crosslinked chitosan microspheres by a water‐in‐oil dispersion method. The crosslinking mechanism examined by FTIR and 13C–NMR suggests that the crosslinking of chitosan by genipin leads to the formation of secondary amide and heterocyclic amino linkage. The polycation–anionic drug interaction between chitosan and indomethacin was pH dependent and could affect the dissolution property of indomethacin. By examination of the release profiles of the crosslinked chitosan microsphere, it was found that the release of indomethacin from the microsphere was sustainable and influenced by factors such as crosslinking of microsphere and chitosan–indomethacin interaction, thus establishing crosslinked chitosan microsphere as a very promising polymeric carrier for drug release. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1700–1711, 2001
Morphological and mechanical properties of PP/ABS blends compatibilized with PP‐g‐acrylic acid
Authors: Patel Alpesh C. , Brahmbhatt Ragesh B. , Sarawade B. D. , Devi Surekha 
Published: October 2004

AbstractPolypropylene (PP) and acrylonitrile–butadiene–styrene (ABS) blends were prepared by a melt extrusion process. PP‐g‐acrylic acid was used as a compatibilizer. Blends with various compositions of PP, compatibilizer, and ABS were prepared and studied for morphological and mechanical properties. PP‐rich ternary blends showed good morphological and mechanical properties. The use of 5 wt % PP‐g‐acrylic acid as a compatibilizer resulted in a fine and homogeneous dispersion of the ABS phase in the PP phase. The experimental data of the tensile modulus showed good agreement in PP‐rich compositions with that generated from Kerner's model with perfect adhesion. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1731–1741, 2001
Effect of montmorillonite on thermal and moisture absorption properties of polyimide of different chemical structures
Authors: Tyan Horng‐Long , Wu Chao‐Yin , Wei Kung‐Hwa 
Published: October 2004

AbstractThe thermal properties and the moisture absorption of three types of polyimide/montmorillonite nanocomposite were investigated: 3,3′,4,4′‐biphenyltetracarboxylic dianhydride‐4,4′‐oxydianiline (BPDA‐ODA); pyromellitic dianhydride‐ODA (PMDA‐ODA); and 3,3′,4,′‐benzophenone tetracarboxylic dianhydride‐ODA (BTDA‐ODA). The inhibition effect on in‐plane coefficients of thermal expansion (CTE) and moisture absorption of these polyimide nanocomposites by layered silicates from montmorillonite was found to decrease with the crystallinity in the pristine polyimides. The largest reduction, 30% in in‐plane CTE occurred in the case of amorphous BTDA‐ODA containing 5 wt % montmorillonite as compared with that of pure BTDA‐ODA, while the reduction in in‐plane CTE was 20% for the case of semicrystalline BPDA‐ODA. The maximum reduction in moisture absorption, 43%, also took place for the case of 3/97 ODA‐Mont/BTDA‐ODA as compared with that of pure BTDA‐ODA, whereas the semicrystalline 1/99 PPD‐Mont/BPDA‐ODA showed a 30% reduction as compared with that of pure BPDA‐ODA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1742–1747, 2001
Reaction kinetics for solid‐state polymerization of poly(ethylene terephthalate)
Authors: Duh Ben 
Published: October 2004

AbstractA simple kinetic model capable of describing the behaviors of solid‐state polymerization (SSP) of poly(ethylene terephthalate) (PET) has been developed. According to this model, there are two types of end groups, namely active end groups and inactive end groups, and the solid‐state polycondensation reaction is a second‐order reaction with respect to the active end group concentration. The inactive end groups include chemically dead end groups and functional end groups that are immobilized by the crystalline structure. The inactive end group concentration determines the ultimate intrinsic viscosity (IV) or molecular weight achievable in the SSP—the lower the inactive end group concentration, the higher the ultimate IV. Four pulverized PET prepolymers with IV values ranging from 0.20 to 0.35 dL/g were solid‐state polymerized in a fluid‐bed reactor at temperatures between 200 and 230°C to generate data to test the model. The experimental results fit the proposed rate equations very well, confirming the adequacy of the proposed kinetic model. Under these SSP conditions, the activation energy is about 23.6 kcal/mol and the average SSP rate about doubles with each 10°C increase in temperature. The rate constant increases, while the inactive end group concentration decreases, with increasing temperature and prepolymer IV. This explains why the reaction rate and the ultimate IV increase with increasing prepolymer IV as well as temperature in the SSP of PET. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1748–1761, 2001
Effect of hydrolysis on porosity of cellulose acetate reverse osmosis membranes
Authors: Košutić K. , Kunst B. 
Published: October 2004

AbstractThe alkaline hydrolysis of asymmetric cellulose acetate membranes was investigated. The changes of cellulose triacetate and cellulose diacetate membrane performances caused by hydrolysis of the membrane material were measured, and the data were analyzed in terms of pore size distributions and effective number of pores in the upper membrane layer before and after hydrolysis. The resulting membranes rejection factors decrease of 10–25%, and a noticeable permeation rates increase were caused by closing of a part of the smallest “network” membrane pores and by increasing the size of the other pores. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1768–1775, 2001
Water crosslinking reactions of silane‐grafted polyolefin blends
Authors: Shieh Yeong‐Tarng , Chuang Hui‐Chun , Liu Chih‐Ming 
Published: October 2004

AbstractWater crosslinking reactions of LDPE, PP, LLDPE, and the LDPE/PP and LDPE/LLDPE blends are investigated. Degrees of crosslinking of these samples are quantitatively compared and discussed in detail in terms of crosslinking ability, phase‐separation behavior, molecular weight (or viscosity), morphology of the constituents in blends, or in the pure state. It is found that PP gives negligible crosslinking reactions in the pure state and in blends with LDPE. LDPE and LLDPE are both capable of giving considerable degrees of crosslinking, with LLDPE giving a higher degree of crosslinking than LDPE at all conditions studied. Degrees of crosslinking of the LDPE/LLDPE blends are not linearly but are zigzagly related to the compositions of the blends with the LDPE/LLDPE = 50/50 blend giving a relatively high degree of crosslinking at 100, 120, and 140°C for a certain time except the condition at 140°C for 12 h compared with the LDPE/LLDPE = 75/25 and 25/75 blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1799–1807, 2001
Adherence evaluation of paint coatings using a three‐point flexure test and acoustic emission
Authors: Devos P. , Baziard Y. , Rives B. , Michelin P. 
Published: October 2004

AbstractThe adherence of paint coatings on aluminum substrates was tested using a three‐point flexure test (TPFT) combined with acoustic emission (AE) evaluation. The mechanical test was defined according to the French Standard. During bending of the paint‐coated specimen, acoustic emission signals were recorded and analyzed. Substrate pretreatments were chosen to show a set of visual interfacial ruptures and a set of visual cohesive ruptures in the paint. The formulation of the paint was fixed by industrial regulations. The varying nature of systems showed different AE patterns, particularly for two types of specimens: those that corresponded to solvent degreasings and the others to aqueous chemical pretreatments. The behavior of the paint coating differed, with significant AE, damage, and crack propagation in the first case and instantaneous phenomena in the other case. It is then possible to establish a relationship between the analysis of the recorded AE signal and the type of joint rupture. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1848–1857, 2001
Effect of CaCO3 on the performance of Partex surface modification by ultraviolet radiation curing method
Authors: Rahman M. Mizanur , Khan Mubarak A. , Uddin M. Khabir , Idriss Ali K. M. , Mustafa A. I. 
Published: October 2004

AbstractSeveral UV‐curable formulations containing epoxydiacrylate (EB‐600) oligomer with a tri‐functional monomer, trimethylol propane triacrylate (TMPTA), and photoinitiator Irgcure‐369 were developed to improve the surface of Partex. Filler or extender CaCO3 was incorporated into the solution. Thin polymer films were prepared on glass plate with these formulated solutions and finally applied on polished Partex surface, and both were cured under UV‐radiation. The properties of UV‐cured thin films were studied as a function of CaCO3 concentration. Pendulum hardness and gel content were found to decrease on glass plate with the increase of CaCO3 concentration. Pendulum hardness, scratch hardness, and abrasion resistance of the cured Partex were found to be higher with the increase of CaCO3 content up to 4%. Thus, the formulation containing 4% CaCO3 showed the best performance over all formulations containing CaCO3. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1858–1867, 2001
Evidence of irradiation‐induced crosslinking in miscible blends of poly(vinyl chloride)/epoxidized natural rubber in presence of trimethylolpropane triacrylate
Authors: Ratnam Chantara Thevy , Nasir M. , Baharin A. , Zaman Khairul 
Published: October 2004

AbstractElectron‐beam initiated crosslinking of a poly(vinyl chloride)/epoxidized natural rubber blend (PVC/ENR), which contained trimethylolpropane triacrylate (TMPTA), was carried out over a range of irradiation doses (20–200 kGy) and concentrations of TMPTA (1–5 phr). The gelation dose was determined by a method proposed by Charlesby. It was evident from the gelation dose, resilience, hysteresis, glass‐transition temperature (Tg), IR spectroscopy, and scanning electron microscopy studies that the miscible PVC/ENR blend underwent crosslinking by electron‐beam irradiation. The acceleration of crosslinking by the TMPTA was further confirmed in this study. Agreement of the results with a theory relating the Tg with the distance between crosslinks provided further evidence of irradiation‐induced crosslinking. The possible mechanism of crosslinking induced by the irradiation between PVC and ENR is also proposed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1914–1925, 2001
Effect of hydrogen donor on the thermal degradation of poly(vinyl acetate) in solution
Authors: Madras Giridhar , Chattopadhyay Sujay 
Published: October 2004

AbstractThe thermal decomposition of poly(vinyl acetate) (PVAc) in solution was investigated both in the presence and absence of a hydrogen donor (H‐donor). Thermal degradation experiments at 220–250°C were conducted in a batch reactor by dissolving PVAc in diphenylether. The molecular weight distributions were measured as a function of reaction time. Experimental data indicated that the polymer degrades by random chain scission. The random scission degradation rate coefficient was between 9.01 × 10−4 and 6.12 × 10−3 min−1. The activation energy, determined from the temperature dependence of the rate coefficient, was 31.5 kcal/mol. The effect of an H‐donor, diphenylamine, was also investigated by varying the concentration from 0 to 0.472 mol/L. The data indicated that the presence of diphenylamine increases the PVAc degradation rate from 3.67 × 10−3 to 4.59 × 10−3 min−1 at 240°C. This is in contrast to the reduction in the degradation rate of polystyrene in the presence of diphenylamine. Continuous distribution models have been developed by treating molecular weight as a continuous variable. The experimentally observed variation of the degradation rates with H‐donor concentration is satisfactorily explained by a continuous distribution model based on the radical mechanism that involves the elementary reactions including the hydrogen abstraction steps. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1996–2000, 2001
Synthesis and characterization of polymers derived from selenophene
Authors: Del Valle M. A. , Moreno J. , Díaz F. R. , Tagle L. H. , Bernède J. C. , Tregoüet Y. 
Published: October 2004

AbstractThe synthesis of poly(2,5‐selenophen‐oxo‐1,4‐phenylen‐selenide‐1,4‐phenylene‐oxo) (I) and poly(2,5‐selenophen‐oxo‐1,4‐phenylen‐diselenide‐1,4‐phenylen‐oxo) (II) by reaction of 2,5‐bis(1,4‐bromo‐phenylen‐oxo‐)‐selenophene with sodium selenide or diselenide, respectively, using dimethylformamide as solvent, is described. Both monomers and polymers were characterized by elemental analysis, melting point, and FTIR spectroscopy. Polymers I and II were doped with iodine and SbF5 and characterized by SEM and XPS. Also, the conductivity and the Tg values were determined. For both polymers the best doping agent was iodine, although polymer II always presented higher conductivity, reaching values of about 6 · 10−9 S · cm−1. The Tg values suggest a likely crosslinking of the chains in polymer II when doped with SbF5. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2019–2026, 2001
Dynamic‐mechanical study of water‐blown rigid polyurethane foams with and without soy flour
Authors: Chang Li‐Chung , Xue Yu , Hsieh Fu‐Hung 
Published: October 2004

AbstractGlass transition temperatures of water‐blown rigid polyurethane foams at three levels of initial water content, 4.5–5.5%, and five levels of soy flour, 0–40%, were determined by dynamic‐mechanical instrumentation at the temperature range of 50–280°C and the frequencies from 0.1 to 20 Hz. The results showed that both the addition of soy flour in the rigid polyurethane foam system and increasing initial water content contributed to a higher glass transition temperature. Moreover, increasing the percentage of the soy flour in the rigid polyurethane foam system led to higher compressive strength and broader master curves for the imaginary part of the elastic modulus. The KWW function fitted the master curve better than the HN and CD functions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2027–2035, 2001
Kinetics of NMBA polymerization in a starved feed reactor
Authors: Cao Gui‐Ping , Zhu Zhong‐Nan , Zhang Ming‐Hua , Le Hui‐Hui , Yuan Wei‐Kang 
Published: October 2004

AbstractA starved feed reactor (SFR) is a semibatch polymerization reactor in which initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. The added initiator decomposes instantaneously, and the added monomer polymerizes immediately. The monomer concentration in the SFR is very low, ideally approaching zero. The reactor is in a starved status for reactants. The molecular weight of the product polymer can be effectively controlled by the feed ratio of monomer to initiator. This article presents a study on the kinetics of NBMA polymerization in an SFR. The model parameters were regressed with the experimental data. Although the mass fraction of polymer in the SFR was high (higher than 50%), viscosity was not high and the “gel effect” was weak because of the low molecular weight of the products. It was found that the termination rate constant is a power function of polymer concentration, and the lumped rate constant, kp/(k)1/2, can be modeled by the Arrhenius equation. The initiator efficiency, f, remained constant at a temperature less than 120°C, and increased with the temperature increasing at temperatures greater 120°C. The other parameters remained constant in the experiment range. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2068–2075, 2001
Semi‐interpenetrating polymer networks from castor oil‐based polyurethane and nitrokonjac glucomannan
Authors: Gao Shanjun , Zhang Lina 
Published: October 2004

AbstractNew semi‐interpenetrating polymer networks (semi‐IPNs) coded as PUNK were successfully synthesized from castor oil‐based polyurethane (PU) prepolymer and 10–40 wt % nitrokonjac glucomannan (NKGM) containing a degree of substitution of 2.4 and a weight‐average molecular weight of 4.75 × 104. The semi‐IPN sheets that were 100 μm thick were cured more speedily than PU, with curing times of 5 h for PUNK and 16 h for PU at 50–70°C. The structure and miscibility of the semi‐IPN sheets were studied by Fourier transform infrared spectroscopy, ultraviolet spectroscopy, and scanning electron microscopy. The results showed that a strong intermolecular interaction caused by hydrogen bonding between NKGM and PU exists in PUNK, resulting in good miscibility. When the NKGM content of the semi‐IPNs sheets was 20 wt %, the tensile strength and light transmittance were obviously higher than that of the PU sheets. The NKGM in the semi‐IPN sheets plays an important role not only in accelerating the cure but also in improving the mechanical properties and biodegradability. As a new material prepared from renewable resources, PUNK has potential applications because of its biodegradability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2076–2083, 2001
The use of positron annihilation lifetime technique to study the effect of doping metal salts on polyhydroxamic acid polymers
Authors: Mazzroua A. , Mostafa N. , Gomaa E. , Mohsen M. 
Published: October 2004

AbstractPolyhydroxamic acid (PHA) from polymethacrylamide (PMAA) was prepared. Chromium chloride (CrCl3) and ferric chloride (FeCl3) salts were added to the polymer in order to increase its electrical conductivity, i.e., the dopants help produce semiconducting properties. The positron annihilation lifetime technique spectroscopy (PALS) was used to study the changes in the free volume as a function of FeCl3 and CrCl3 concentrations. ortho‐Positronium lifetime components were used to estimate the free volume parameters. It was found that the hole size and the total free volume fraction decreased with FeCl3 concentration. On the other hand, the hole size increased slightly with CrCl3 concentration and then decreased, while the total free volume fraction increased continuously. The free volume distributions were determined from ortho‐positronium distributions. The electric conductivity as a function of FeCl3 and CrCl3 concentrations showed fluctuation behavior and showed a continuous increase with the increase in temperature. The correlation between positron annihilation parameters and electric conductivity were discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2095–2101, 2001
Depolymerization of polyethyleneterephthalate in supercritical methanol
Authors: Kim B.‐K. , Hwang G.‐C. , Bae S.‐Y. , Yi S.‐C. , Kumazawa H. 
Published: October 2004

AbstractThe depolymerization of polyethyleneterephthalate (PET) in supercritical methanol was carried out using a batch‐type autoclave reactor. The total conversion and the yield of dimethylterephthalate (DMT) increased with rising temperature. The final yield of DMT at 300°C and 310°C reached 97.0% and 97.7%, respectively. The yield of DMT was markedly increased when the methanol density was 0.08 g/cm3, and leveled off at higher densities. A kinetic model to describe the depolymerization of PET in supercritical methanol was proposed, where the scission of one ester linkage in PET by a methanol molecule produces one carboxymethyl group and one hydroxyl group. The values of the forward reaction rate constant at different temperatures were determined by comparing the observed time dependence of carboxymethyl group concentration with that calculated by the proposed model. The activation energy was evaluated to be 49.9 kJ/mol, a value close to a literature value (55.7 kJ/mol). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2102–2108, 2001