bluuebunny/crossref_metadata_2025_split huggingface dataset:
Semicontinuous emulsion polymerization of vinyl acetate: Effect of ethoxylation degree of nonionic emulsifiers
Authors: Sarac Ayfer , Erbil H. Yildirim , Yildirim Hüseyin 
Published: September 2002

AbstractPoly(vinyl acetate) latices were prepared in the presence of an ammonium persulfate initiator, 10–50 mol of an ethoxylated nonylphenol nonionic emulsifier, and a poly(vinyl alcohol) colloid stabilizer by applying semicontinuous emulsion polymerization (delayed monomer and initiator addition process) in a laboratory scale similar to industrial practice. Two approaches were applied: the molar concentration of the nonionic emulsifier was kept constant and the weight ratios in the polymerization recipe varied or the weight ratios were kept constant. The effects of the change in the ethoxylation degree of the emulsifier to the final latex viscosity, average polymer molecular weight, polymer grafting degree, surface tension of the latex, and the surface free energy of the dried films were investigated. It was determined that the resultant latex viscosity decreases and the viscosity‐average polymer molecular weight increases with increase of the nonionic emulsifier ethoxylation degree. The increase of the ethoxylation degree does not seriously affect the surface tension of the resultant latex or the surface free energy of the dried poly(vinyl acetate) films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 844–851, 2002
Rheology of polyflavonoid tannin–formaldehyde reactions before and after gelling. II. Hardener influence and comparison of different tannins
Authors: Garnier S. , Pizzi A. , Vorster O. C. , Halasz L. 
Published: September 2002

AbstractGood correspondence of the gel‐time values obtained by two different methods, G′ = G″ and 1/η0→0, was observed for different types of natural and modified tannin extracts. The pH presents the predominant effect on both the activation energies and the gel times observed, while the proportion of a paraformaldehyde hardener has a much lesser effect on these parameters. The rate constants of the different phases of the reaction of polycondensation with formaldehyde, both before and after the gel point, were obtained for the six commercial tannin extracts tested. The viscoelastic properties of the different tannins/formaldehyde gels were measured. The gel stiffness S, relaxation coefficient n, and relaxation time λ were determined and their dependence on the proportion of the formaldehyde hardener, on the temperature, and on the type of tannin was determined. The gel stiffness S appears to be influenced considerably by the proportion of the formaldehyde hardener. Its value decreased as the percentage of the hardener increased: This was due to early network immobilization and the resulting lower level of crosslinking resulting from it. The influence on S of the temperature is not very pronounced. The relaxation coefficient n appears to depend mainly on the reactivity of the tannin used: The faster the reactivity, the higher was the value of n. This appears to be valid exclusively in tannin extracts where the colloidal state is still present, while it is not valid in extracts where the colloidal state was eliminated by, for example, solvent extraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 864–871, 2002
Rheology of polyflavonoid tannin–Formaldehyde reactions before and after gelling. I. Methods
Authors: Garnier S. , Pizzi A. , Vorster O. C. , Halasz L. 
Published: September 2002

AbstractThe gelling and hardening reactions of different, commercial polyflavonoid tannin extracts of the prorobitenedin/profisetinidin, procyanidin, and prodelphinidin types with formaldehyde were studied by parallel‐plate rheometry. To do this, methods to determine the rheological characteristics of tannin–formaldehyde polycondensation reactions both before and after the gel point were developed. The validity of some modifications of known methods was checked on the best‐known commercial tannin extract, namely, the reaction of the mimosa tannin extract with 5% paraformaldehyde, over a range of different temperatures. The gel point was determined by three different methods, namely, by the crossover point of viscous and elastic moduli, by the extrapolation to ∞ of the zero‐frequency viscosity, and by determining the point at which the value of tan δ is constant whatever frequency is used in the measurement. The results obtained were critically compared. The comparisons obtained were good and were reproducible when the first two methods were used, but not when the third one was used. This allowed the determination of the energy of activation at different stages in the tannin–aldehyde polycondensation reaction and the calculation of the degree of conversion of the tannin–aldehyde polycondensation before, at, and after the gel point. Mathematical expressions defining the degree of conversion for tannin–aldehyde reactions before, at, and after the gel point as a function of different moduli were developed and checked with the experimental data obtained. Methods and mathematical expressions for the determination of the rate constants of the different stages of the reaction were also developed and checked. After the gel point, the system was modeled using both a diffusion‐controlled model and a second‐order kinetic law. The applied results obtained indicated that, although a certain element of diffusion control is present, a second order, diffusion‐independent kinetic is more valid under the experimental conditions used. This indicates that the rheometry approach to a polycondensation network is limited mostly by the capability of the equipment to the region after the gel point, where diffusion control does not as yet play a predominant role. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 852–863, 2002
Challenges in forming successful mixed matrix membranes with rigid polymeric materials
Authors: Mahajan Rajiv , Burns Ryan , Schaeffer Michael , Koros William J. 
Published: September 2002

AbstractMixed matrix materials comprised of molecular sieve domains embedded in processable polymer matrices have the potential to provide membranes with higher permselectivity and equivalent productivity compared to existing membrane materials. It has been shown that successful mixed matrix materials can be formed using relatively low glass transition (Tg) polymers that have a favorable interaction with the sieves. This article extends this earlier work to include the use of more practical rigid matrix polymers with high Tgs that can ultimately be used in forming high‐performance mixed matrix layers for composite membranes. Initial attempts to form mixed matrix materials based on high Tg polymers with a type 4A zeolite resulted in poor adhesion between the polymer and sieve. Correcting this problem was pursued in this study by forming the composite material close to the Tg of the polymer by addition of a plasticizer to match the matrix Tg with the solvent volatility. Forming the films at elevated temperatures presented substantial challenges, and this work discusses overcoming these challenges in detail. With some modifications in the film casting procedure, successful materials were achieved. Promising oxygen/nitrogen transport results are presented for these zeolite 4A–Matrimid®/plasticizer membranes, and this data compares favorably with predictions of the well‐known Maxwell model for composite systems. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 881–890, 2002
The rheological behavior of immiscible polymer blends
Authors: Choi Gwan‐Young , Kim Ho‐Gyum , Kim Young‐Ho , Seo Chang‐Wook , Choi Jin‐Hwan , Han Dong‐Hee , Oh Dae‐Hee , Min Kyung‐Eun 
Published: September 2002

AbstractThe complex shear modulus of immiscible polymer blends was measured by a frequency sweep experiment for polystyrene (PS)/low density polyethylene (LDPE) and poly(methylmethacrylate) (PMMA)/LDPE blends at constant composition (13.5/86.5 vol %) and compared with the prediction model of Palierne. Different morphologies of each blend were also prepared using a rheometer with a constant shear rate and different strain. There was morphological dependency on the complex shear modulus at constant temperature. However, this dependency disappeared at specific temperatures in the frequency sweep experiment. There seemed to be a specific temperature like critical flow temperature (Tcf) of amorphous polymer. The difference in morphology affected the complex shear modulus of blends below the specific temperature, Tcf, but did play a major role in determining the complex shear modulus of blends at over specific temperature. A new method may be needed to determine the critical flow temperature of an amorphous polymer via the measurement of a complex shear modulus for immiscible polymer blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 917–924, 2002
Modified cellulose fibers prepared by the N‐methylmorpholine‐N‐oxide (NMMO) process
Authors: Niekraszewicz B. , Czarnecki P. 
Published: September 2002

AbstractCellulose fibers with modified properties have been prepared from cellulose solutions in N‐methylmorpholine‐N‐oxide (NMMO). Poly(ethylene oxide) as a hydrophilic modifier and polyethylene as a hydrophobic modifier were added to the spinning solution. Based on microscope examination and measurements of such properties of fibers as porosity, moisture absorption, water retention, and tensile strength, structural changes as well as physical and mechanical properties of the resultant fibers depending on the amount of modifier added to the spinning solution were analyzed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 907–916, 2002
Comparison of polycarbonate precursors synthesized from catalytic reactions of bisphenol‐A with diphenyl carbonate, dimethyl carbonate, or carbon monoxide
Authors: Kim Won Bae , Lee Jae Sung 
Published: September 2002

AbstractTransesterification of bisphenol‐A with diphenyl carbonate or dimethyl carbonate, and direct oxidative carbonylation of bisphenol‐A were compared to obtain polycarbonate precursors for phosgene‐free polycarbonate synthesis. The melt‐transesterification of bisphenol‐A and diphenyl carbonate occurred readily to produce reactive precursors without a significant equilibrium constraint. On the other hand, the transesterification of bisphenol‐A and dimethyl carbonate showed a serious equilibrium limitation in obtaining reactive polycarbonate precursors leading to high molecular weight polymers, and coproduced a significant amount of methylated bisphenol‐A. The direct oxidative carbonylation of bisphenol‐A with CO produced diphenolic‐ended oligomers and a significant amount of by‐products, which are the least reactive in the subsequent polycondensation step of the phosgene‐free polycarbonate process. A novel method to synthesize the reactive polycarbonate precursors was proposed that employed the coupled oxidative carbonylation of both bisphenol‐A and phenol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 937–947, 2002
Poly(ethylene glycol) electrolyte gels prepared by condensation reaction
Authors: Koo Jahyun , Kim Dukjoon 
Published: September 2002

AbstractPoly(ethylene glycol) electrolyte gels were prepared by condensation reaction in the presence of tetraethoxysilane. Differential scanning calorimetry and X‐ray diffraction spectroscopy were used to investigate the thermal transition behavior and crystalline structure of polymer gels prepared. Both formation of crosslinks and incorporation of salts or plasticizers reduced the development of crystalline structure of poly(ethylene glycol)s. Cyclic voltammetric and ion‐conducting behaviors of polymer gels were analyzed using potentiostat and impedance spectroscopy, and those were also considerably affected by the crosslinking density of polymers and the concentration of electrolyte salt or plasticizers incorporated. Poly(ethylene glycol) gels possessing certain levels of electrolyte salt and plasticizer were expected to have applications of solid electrolytes for lithium polymer secondary batteries. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 948–956, 2002
Preparation and characterization of novolac type phenolic resin blended with poly(dimethylsiloxane adipamide)
Authors: Hung Albert Y. C. , Wang Feng‐Yih , Ma Chen‐Chi M. , Sun Yih‐Min 
Published: September 2002

AbstractPhenolic resin/poly(dimethylsiloxane adipamide) (PDMSA) blends, which have been prepared, show miscibility due to intermolecular H‐bonding existing between phenolic resin and the PDMSA. The specific H‐bonding of novolac type phenolic/PDMSA blends was characterized by means of glass transition temperature behavior and Fourier Transform Infrared Spectroscopy (FTIR). The strength of intermolecular H‐bonding within the phenolic blend is a function of the H‐bonded group of the PDMSA modifier and corresponds to the deviation glass transition temperature (ΔTg). Phenolic/PDMSA blends were completely miscible, as confirmed by the Tg study. The FTIR result is in good agreement with the inference from Tg behavior. The char yield of phenolic/PDMSA corresponds to the phenolic resin content. The molecular mobility of phenolic/PDMSA blends increases with PDMSA content in the phenolic‐rich region. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 984–992, 2002
Studies on photosensitive homopolymer and copolymers having a pendant photocrosslinkable functional group
Authors: Balaji R. , Nanjundan S. 
Published: September 2002

AbstractThe methacrylate monomer 4‐methyacryloyloxyphenyl‐3′,4′‐dimethoxystyryl ketone (MPDMSK), having a free‐radical polymerizable group and a photocrosslinkable functional group, was synthesized. The homopolymer and copolymers of MPDMSK with glycidyl methacrylate were synthesized by free‐radical solution polymerization. The structures of the newly synthesized monomers, homopolymer, and copolymers were confirmed by different spectroscopic techniques. The average molecular weights of the polymers were determined by gel permeation chromatography. The thermal stability of the polymers was measured by thermogravimetric analysis in air and the glass‐transition temperatures were determined by differential scanning calorimetry under nitrogen atmosphere. The copolymer compositions were determined by 1H‐NMR analysis. The monomer reactivity ratios were determined by the application of conventional linearization methods such as Fineman–Ross, Kelen–Tüdös, and extended Kelen–Tüdös methods. The photoreactivity of both the homopolymer and the copolymers having pendant chalcone moieties was studied in various solvents. The effects of various factors such as solvents, concentrations, copolymer ratios, and photosensitizers on the rate of photocrosslinking of the newly synthesized polymers were investigated and the results were discussed for using the polymers as negative photoresists. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1023–1037, 2002
Optimal reaction conditions for the minimization of energy consumption and by‐product formation in a poly(ethylene terephthalate) process
Authors: Ha Kyoung‐Su , Rhee Hyun‐Ku 
Published: September 2002

AbstractWe determined the optimal reaction conditions to minimize the energy cost and the quantities of by‐products for a poly(ethylene terephthalate) process by using the iterative dynamic programming (IDP) algorithm. Here, we employed a sequence of three reactor models: the semibatch transesterification reactor model, the semibatch prepolymerization reactor model, and the rotating‐disc‐type polycondensation reactor model. We selectively chose or developed the reactor models by incorporating experimentally verified kinetic models reported in the literature. We established the model for the entire reactor system by connecting the three reactor models in series and by resolving some joint problems arising when different types of reactor models were interconnected. On the basis of the simulation results of the reactor system, we scrutinized the cause and effect between the reaction conditions and the final quality of the polymer product. Here, we set up the optimization strategy by using IDP on the basis of the integrated reactor model, and the process variables with significant influence on the properties of polymer were selected as control variables with the help of a simulation study. With this method, we could refine the reaction conditions at the end of each iteration step by contracting the spectra of control regions, and the iteration process finally stopped when the profile of the optimal trajectory converged. We also took the constraints on the control variables into account to guarantee polymer quality and to suppress side reactions. Constituting six different strategies by setting weighting vectors differently, we examined the differences in optimal trajectories, the trend of optimality, and the quality of the final polymer product. For each of the strategies, we conducted the optimization to examine whether the number‐average degree of polymerization approached the desired value. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 993–1008, 2002
Influence of the crystallization conditions on the morphology of the contact layer of polyethylene crystallized on graphite: Atomic force microscopy studies
Authors: Tracz Adam , Jeszka Jeremiasz K. , Kucińska Iwona , Chapel Jean‐Paul , Boiteux Giséle , Kryszewski Marian 
Published: September 2002

AbstractThe influence of crystallization conditions on the morphology of the contact layer of high‐density polyethylene crystallized on graphite has been investigated. The characteristic morphology of the polyethylene contact layer consists of striated, ribbonlike structures organized in domains in which the striations follow the same direction. The directions in different domains reflect the threefold symmetry of the graphite lattice. From the dependence of the width of ribbons on the crystallization conditions (i.e., the cooling rate and annealing), it has been concluded that the polymer chain is aligned parallel to the striation directions and that the ribbon width corresponds to the lamellar width. Therefore, the lamellar width in the contact layer (60 and 80 nm for cooling rates of 10 and 0.2°/min, respectively) is considerably bigger than in the bulk (ca. 26 nm). In addition, the chain orientation can be uniform over large areas, but the domain orientation can be disturbed by the presence of pits only one atomic layer deep (0.335 nm) if they are formed on the graphite surface. These results show the great importance of the nanostructure of the support for polymer chain alignment and epitaxial crystallization of polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1329–1336, 2002
Transformation of polyethylene crystals by high‐pressure annealing
Authors: Kazmierczak T. , Galeski A. 
Published: September 2002

AbstractWe investigated the possibility of obtaining high‐density polyethylene (PE) samples with crystals in a broad range of thicknesses. PE samples solidified by slow cooling were subjected to hydrostatic pressure at room temperature and then heated to the region of mobile pseudohexagonal form, without being passed through melting. The chains were allowed to rearrange for a period of time to a more extended chain conformation, forming larger crystals. During cooling under pressure, the transformation to orthorhombic crystals of larger thickness occurred. The thickness of the crystals was then controlled by pressure, temperature, and annealing time at high temperatures. The temperature and the pressure in the high‐pressure cell was maintained at constant level within 230–295°C and 260–630 MPa, respectively. In this way, we transformed under pressure chain‐folded PE crystals to partly chain‐extended crystals with peak melting temperatures up to 144.85°C. A range of samples with crystals 20–160 nm thick were produced and characterized with several techniques, including wide‐ and small‐angle X‐ray scattering, conventional and temperature‐modulated differential scanning calorimetry, dynamic mechanical analysis, and scanning electron, atomic force, and light microscopy as well as low‐frequency Raman spectroscopy. Changes in crystallographic unit cell dimensions were observed for crystals with different thicknesses. Crystallinity degree increased with increases in the lamellar thickness up to some level. The initial spherulitic structure deteriorated due to a multifold increase in the lamellar thickness. Oriented samples subjected to annealing in the pseudohexagonal region did not lose the crystal orientation while crystals grew thicker and the crystallinity degree increased; however, no drastic change to noncrystalline phase topology and structure was noticed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1337–1350, 2002
Modeling of polymer crystallization in plates, pipes, and rods during cooling
Authors: Piorkowska Ewa , Galeski Andrzej 
Published: September 2002

AbstractWe modeled crystallization of isotactic polypropylene inside plates, rods, and pipes during cooling. The modeling was based on the solution of the heat conduction equation, which takes into account the liberation of the heat of crystallization. The predictions of polymer crystallization kinetics was based on differential scanning calorimetry data and on spherulite growth rate measurements. The influence of size on the crystallization process was determined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1363–1372, 2002
Spherulitic structure development during crystallization in a finite volume
Authors: Piorkowska E. , Billon N. , Haudin J. M. , Kolasinska J. 
Published: September 2002

AbstractThis study was devoted to the formation of a spherulitic pattern in a confined space. Thin poly(methylene oxide) films, one wide and the second of width of average spherulite diameter, were crystallized isothermally at the same temperature and studied. In the narrow sample, the number of spherulites per unit area increased, whereas the length of interspherulitic boundary lines per unit area and the number of triple points, impingement points of three spherulites, per unit area were significantly smaller than in the wide sample. Computer simulation of the spherulitic crystallization demonstrated not only a decrease in the number of boundary lines and triple points per unit area due to limits of space available for the spherulitic nucleation and growth but also differences in the progression of the spherulitic structure formation between wide films and narrow strips. A model of the spherulitic pattern development in narrow strips of the polymer based on probability theory is elaborated. The model allows one to predict the rates of formation of the interspherulitic boundaries and also the distributions of distances from the spherulites centers to the boundaries for an isothermal and a nonisothermal crystallization. The total length of interspherulitic lines and the total number of triple points between spherulites can be also calculated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1373–1385, 2002