bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterization of core/shell ionomeric latexes. I. Latex and film properties
Authors: Arora A. , Daniels E. S. , El‐Aasser M. S. 
Published: April 2003

AbstractThis research work involved studies on the synthesis and characterization of core/shell ionomeric latexes in order to understand the process of ionic aggregate formation. The core/shell structure of the ionomeric latexes prepared in this study confines the ionic domains to the copolymeric matrix within the shell polymer, and in addition, benefits from the ionomeric properties and core/shell structure simultaneously. Core/shell ionomeric latexes with polystyrene cores and styrene/n‐butyl acrylate/methacrylic acid terpolymer shells were synthesized by a semicontinuous seeded emulsion copolymerization process. The distribution of the methacrylic acid in the core/shell latexes was determined using conductometric titration techniques. The results of the conductometric titration analysis indicate that the principal locus of the carboxyl groups in the core/shell latexes is at the particle surface, but specific information about the differences in the distribution of methacrylic acid inside the latex particles could not be obtained. Mechanical characterization of the core/shell ionomeric latex films was carried out to understand the structure‐property relationships using Dynamic Mechanical Analysis (DMA) and tensile testing. It was discovered that the core/shell latexes exhibited significantly different properties, owing to the differences in the overall carboxyl content and surface loading. Extensive studies were carried out to study the effect of water plasticization on the mechanical behavior of the core/shell ionomeric latex films; water adsorption causes the solvation of ionic aggregates. A preliminary investigation of the effect of the type of counterion used for the neutralization of carboxyl groups on the properties of core/shell ionomeric latex films was also carried out. © 1995 John Wiley & Sons, Inc.
Simultaneous interpenetrating networks of a polyurethane and poly(methyl methacrylate). II. Partitioning of MMA monomer in the last stages of polymerization
Authors: Mishra V. , Du Prez F. E. , Goethals E. J. , Sperling L. H. 
Published: April 2003

AbstractIn a model polyurethane/poly(methyl methacrylate) (PU/PMMA) system, the partitioning of unreacted methyl methacrylate monomer (MMA) is studied in the late stages of its polymerization, simulated by incorporating controlled amounts of MMA in otherwise fully cured simultaneous interpenetrating networks (SIN) samples. Glass transitions temperatures (Tg) were determined using dynamic mechanical spectroscopy and differential scanning calorimetry as a function of MMA content of the SINs. The lowering of Tg in each phase due to the plasticization effect of MMA is used to calculate a plasticization coefficient for each phase, finally allowing calculation of the partition coefficient of MMA between the two phases. It is found that the MMA monomer distributes itself almost uniformly across the two phases of the current SIN system, leading to speculation as to the locus of late SIN polymerization. © 1995 John Wiley & Sons, Inc.
Interfacial aspects of strength development in poly(methyl methacrylate)‐based latex systems
Authors: Yoo S. , Harelle L. , Daniels E. S. , El‐Aasser M. S. , Klein A. 
Published: April 2003

AbstractFilm formation from poly(methyl methacrylate) (PMMA) latex and PMMA copolymer latex incorporating N‐(iso‐butoxymethyl)acrylamide (IBMA) or methacrylic acid (MAA) has been investigated in terms of the development of tensile strength as a function of annealing time and temperature. Tensile strength is developed through a combination of macromolecular interdiffusion and interfacial crosslinking. The relative rates of interdiffusion vs. crosslinking reactions were studied as a function of temperature and the chemical nature and concentration of the IBMA and MAA functional groups. For low concentrations of these two functional monomers it appears that polymer chain interdiffusion between adjacent latex particles during the film formation process dominates the kinetics of strength development. However, at higher IMBA and MAA concentrations, the higher glass transition temperature at the latex particle surface and intraparticle crosslinking hinders interdiffusion, as reflected by differences in the power law exponent values obtained from the log‐log dependence of tensile strength on annealing time. The power law exponents were higher in the case of PMMA than for both IBMA‐ and MAA‐containing copolymers. There was a greater influence temperature on the tensile behavior for the MAA copolymer system as compared to the IBMA copolymer. In the interfacially crosslinked latex polymer system, there is competition between the interdiffusion and crosslinking mechanisms in determining the final mechanical strength of films during the annealing process. © 1995 John Wiley & Sons, Inc.
Core—shell structured latex particles. II. Synthesis and characterization of poly(n‐butyl acrylate)/poly(benzyl methacrylate—styrene) structured latex particles
Authors: Segall I. , Dimonie V. L. , El‐Aasser M. S. , Soskey P. R. , Mylonakis S. G. 
Published: April 2003

AbstractThe synthesis of structured latex particles involved the preparation of a slightly crosslinked poly(n‐butyl acrylate) (PBA) seed and a poly(benzyl methacrylate‐styrene) [P(BM‐St)] shell. It was found that structured core‐shell latex particles prepared by semicontinuous monomer addition yielded better coverage of the seed particles than those polymerized by batch and that poly(benzyl methacrylate) yielded better coverage than polystyrene (PS). Polymerizations in the presence and absence of a chain transfer agent indicated that the presence of isooctyl mercaptopropionate (IOMP) causes the second‐stage monomer to polymerize as an isolated, single patch of shell material. In the absence of IOMP, smaller patches of shell material are spread throughout the PBA seed surface. The different morphologies obtained under different polymerization conditions were attributed to thermodynamic and kinetic factors such as polymer‐polymer interfacial tensions and viscosity effects. © 1995 John Wiley & Sons, Inc.
Interfacial studies in CTBN‐modified epoxies
Authors: Bagheri R. , Pearson R. A. 
Published: April 2003

AbstractRubber particle cavitation and concomitant shear deformation of the matrix is known to be a major source of toughening in rubber‐modified epoxies. The role of the rubber‐matrix interface in this toughening mechanism, however, is not well studied. It has been claimed by Chen and Jan [Polym. Eng. Sci., 31,577 (1991)] that introduction of a ductile interphase around the rubbery phase enhances plastic dilation of particles and thus contributes to fracture energy of modified blend. In spite of this promising development in rubber toughening, very few studies on the use of ductile interfaces to improve the fracture resistance of rubber‐modified polymers have been initiated. The objective of this investigation is to examine the role of ductility of interface on the fracture toughness of rubber‐modified epoxies. Both ductile and rigid interphases are incorporated around CTBN particles in a DGEBA epoxy matrix via end‐capping of rubber with epoxy monomers different from that of the matrix. The results of this investigation suggest that introduction of a ductile interphase may indeed further improve the crack growth resistance of material under certain test conditions. In contrast, introduction of the rigid interphase, in the system studied, promoted interfacial debonding and plastic dilation but did not alter the mechanical performance of the rubber‐modified blend. © 1995 John Wiley & Sons, Inc.
Poly(vinyl chloride)/styrene‐butadiene rubber blends prepared by dynamic vulcanization with nitrile rubber as the compatibilizer
Authors: Zhu S.‐H. , Chan C.‐M. , Zhang Y. X. 
Published: April 2003

AbstractA new kind of thermoplastic elastomer is obtained by dynamic curing of PVC/SBR blends. A compatibilizer is necessary, and of three tested—NBR and two ABSs—NBR‐18 is the best. Sulfur and Dicumyl peroxide were chosen as the two different curing agents for the blends. The curing agent and its concentration have a dramatic effect on the mechanical properties. Di(2‐ethyl hexyl)phthalate was used as the plasticizer for PVC. Variations in the PVC and di(2‐ethyl hexyl)phthalate concentrations can produce materials having a wide range of hardness and strength to meet the needs of different applications. The effects of processing parameters such as blending time and processing temperature and the effect of filler in the blend on the mechanical properties were also investigated. The material, after processing five times, showed no significant changes in physical properties. © 1995 John Wiley & Sons, Inc.
Effect of chemical modification on FTIR spectra. I. Physical and chemical behavior of coir
Authors: Samal R. K. , Panda B. B. , Rout S. K. , Mohanty M. 
Published: April 2003

AbstractCoir fibers were chemically modified through alkali treatment, and crosslinking with formaldehyde, para‐phenylene diamine, phthalic anhydride, and combined crosslinking‐cyanoethylation reactions in appropriate solvent and catalyst. The parent and chemically modified coir were characterized by FTIR spectra. The percent moisture regain, tensile strength, and behavior toward some chemical reagents (solubility %) of parent and chemically modified fibers have also been evaluated. The modified fibers showed significant hydrophobicity, improved tensile strength, and good chemical resistance. © 1995 John Wiley & Sons, Inc.
In situ chemical analysis of domains in polymer biends by optical fluorescence microscopy
Authors: Dibbern‐Brunelli D. , Atvars T. D. Z. 
Published: April 2003

AbstractPoly(vinyl alcohol) (PVA)/poly(vinyl acetate) (PVAc) blends in different proportions show phase separation in the solid state. The dimensions, shapes, and distributions of the domains produced by the phase separation process are dependent on the composition and can be observed by conventional optical microscopy. However, using fluorescence optical microscopy of polymer blends in different compositions containing anthracene and/or fluorescein molecules dissolved in the matrices we were able to do a chemical discrimination of each domain. We also observed that anthracene is mainly localized in PVAc domains and fluorescein in PVA domains, and that the diffusion process of these fluorophers within the matrices is controlled by specific polymer–dye interactions. © 1995 John Wiley & Sons, Inc.
Properties of biodegradable hydrogels prepared by γ irradiation of microbial poly(ϵ‐lysine) aqueous solutions
Authors: Kunioka Masao , Choi Hyuk Joon 
Published: April 2003

AbstractPoly(ϵ‐lysine) (PL) hydrogels have been prepared by means of γ irradiation of PL produced by Streptomyces albulus in aqueous solutions. When the dosage of γ irradiation was 70 kGy or more and the concentration of PL in water was 1–7 wt %, transparent hydrogels (opaque hydrogels for 1–3 wt % PL concentration) could be produced. In the case of 70 kGy of γ irradiation and 5 wt % PL concentration, the specific water content (wt of absorbed water/wt of dry hydrogel) of the PL hydrogel was approximately 160. Specific water contents of PL hydrogels decreased markedly with an increase in the dosage of γ irradiation. The specific water contents were increased with an increase in PL concentration in the irradiated solution. This result indicates the presence of a radical scavenger in the PL solution. Swelling equilibria of PL hydrogels were measured in water or in aqueous solutions of various pHs or concentrations of NaCl, Na2SO4, and CaCl2. Under acid conditions, the PL hydrogel swelled due to the ionic repulsion of the protonated amino groups in the PL molecules. The degree of deswelling in electrolyte solution was smaller than that of other ionic hydrogels [poly(γ‐glutamic acid), poly(acrylic acid) etc.]. In addition, the enzymatic degradations of PL hydrogel were studied at 40°C and pH 7.0 in an aqueous solution of the neutral protease [Protease A (Amano)] produced from Aspergillus oryzae. The rate of enzymatic degradation of the respective PL hydrogels was much faster than the rate of simple hydrolytic degradation. The rate of enzymatic degradation decreased with the increase in γ‐irradiation dose during preparation of the PL hydrogel. © 1995 John Wiley & Sons, Inc.
Studies on the kinetics of free‐radical bulk polymerization of multifunctional acrylates by dynamic differential scanning calorimetry
Authors: Thakur A. , Banthia A. K. , Maiti B. R. 
Published: April 2003

AbstractThe course and kinetics of nonisothermal bulk polymerization of multifunctional acrylates were studied by dynamic differential scanning calorimetry (DSC). Measurements were carried out for four straight‐chain monomers, diethylene glycol diacrylate (DEGDA), triethylene glycol diacrylate (TEGDA), tetraethylene glycol diacrylate (TTGDA), and poly(ethylene glycol)diacrylate (PEGDA) (mol. wt. 600), to study the effect of the backbone chain length, atmosphere, and type of initiator on the crosslinking kinetics. 4,4′‐Azobis(4‐cyanovaleric acid) (1.0%, w/w) was used as a free‐radical initiator. From the dynamic scanning of polymerization of DEGDA at five heating rates (2–30°C/min), the average heat of polymerization (ΔHp) was found to be 524.2 J/g. An activation energy of 108.8 kJ/mol and preexponential factor 5.34 × 1012 s−1 were obtained from the Arrhenius plot, In dα/dt. The rate of polymerization was found manyfold greater at 20–60% conversion than at the initial stage (2–8% conversion). Polymerization was studied under both nitrogen and air atmosphere. The results corresponded well with the theory of oxygen inhibition. Different types of initiators, e.g., 4,4′‐azobis(4‐cyanovaleric acid) (ABCVA), 2,2′‐azobisisobutyronitrile (AIBN), and benzoyl peroxide (BPO) were used for polymerization and ABCVA was found to be the most efficient among all. © 1995 John Wiley & Sons, Inc.
Studies on damping behavior of PS/P(EA‐nBA) LIPNs
Authors: Weijiang Peng , Shucai Li 
Published: April 2003

AbstractA series of polystyrene/poly(ethyl acrylate‐n‐butyl acrylate) [PS/P(EA‐nBA)] latex interpenetrating polymer networks (LIPNs) were synthesized by the two‐stage emulsion polymerization method. The influence of composition, crosslinker content, chain transfer agent, polar group, and feeding sequence on the damping properties of the LIPNs were investigated with a Rheovibron Viscoelastometer. The results show that the PS/P(EA‐nBA) LIPNs are a partially miscible system, and that LIPNs favor the broadening of the damping temperature range. The influence of crosslinker content of network I on the damping properties of the LIPNs is not the same as that of network II. The damping properties of the PS/P(EA‐nBA) LIPN is superior to that of P(EA‐nBA)/PS LIPN. Moreover, the introduction of polar groups into the system can increase the damping properties, and adding chain transfer agent can broaden the damping temperature range. © 1995 John Wiley & Sons, Inc.
Thiophosphoryl disulfides: Novel coupling agents for styrene‐butadiene rubber/carboxylated nitrile rubber blends
Authors: Biswas Tapasi , Naskar Nityananda , Basu Dipak Kumar 
Published: April 2003

AbstractThiophosphoryl disulfide was successfully used as a novel coupling agent to form a coherent blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar styrene‐butadiene rubber (SBR) establishing close proximity between them through chemical bridging. The study reveals that XNBR in the presence of thiophosphoryl disulfide greatly improves the physical properties of SBR and thus acts as a reinforcing filler. It is noted that the physical properties of the vulcanizates obtained from the SBR‐XNBR blend depend upon the SBR : XNBR ratio and the mode of cure. SEM studies corroborate the observed facts. © 1995 John Wiley & Sons, Inc.
Polyacrylamide gels filled with ferromagnetic anisotropic powder: A model of a magnetomechanical device
Authors: Kłapciński T. , Galeski A. , Kryszewski M. 
Published: April 2003

AbstractThe concept of a magnetomechanical system able to show permanent magnetization if compressed or to deform in a uniform magnetic field, is presented. The system design is based on polyacrylamide gel filled with demagnetized hard ferrite particles. The ferrite filled gel is deformed by plane strain compression and magnetized while compressed. The orientation of individual magnetized particles was randomized upon compression release. Such samples exhibit no magnetic moment if decompressed and produce magnetic field intensity from 3 to 30 G if compressed. The samples exposed to external uniform magnetic field show macroscopic contraction or expansion of up to 40% of the initial dimensions. The most efficient ferrite was neodymium ferrite in the form of flakes. © 1995 John Wiley & Sons, Inc.
Hydrogenation of ring opening metathesis polymerization polymers
Authors: Sohn B. H. , Gratt J. A. , Lee J. K. , Cohen R. E. 
Published: April 2003

AbstractVarious methods of hydrogenating ring opening metathesis polymerization (ROMP) polymers were investigated as part of an effort to improve their stability and increase their usefulness as matrix materials for nanocluster synthesis. Hydrogenation with Pd/BaSO4 catalyst in high‐pressure hydrogen gas was only partly successful and limited to unfunctionalized polymers such as polymethyltetracyclododecene. Block copolymers containing phosphine or carboxylic acid functionalities were successfully hydrogenated by diimide generated in situ from p toluenesulfonylhydrazide. © 1995 John Wiley & Sons, Inc.
Intramolecular effects in cellulose mixed benzyl ethers blended with poly(ε‐caprolactone)
Authors: Frazier Charles E. , Glasser Wolfgang G. 
Published: April 2003

AbstractTri‐O‐benzyl cellulose, tri‐O‐p‐fluorobenzyl cellulose, and a corresponding series of cellulose mixed benzyl ethers were synthesized and blended with poly(ε‐caprolactone) (PCL). Mechanical and thermal analyses indicated that none of the cellulose benzyl ethers of the cellulose mixed benzyl ethers was miscible with PCL. However, there was evidence of a limited degree of compatibility that exhibited a dependence on the substituent ratio, or copolymer composition, of the cellulose mixed benzyl ethers. The weak interactions in these blends were found to be nonspecific, and thus the limited compatibility is thought to arise from intramolecular interactions within the cellulose mixed benzyl ethers. The treatment of cellulose mixed derivatives as copolymers and the potential use of intramolecular effects in cellulose derivative blending is discussed. © 1995 John Wiley & Sons, Inc.
In situ preparation of N,N‐dimethyl‐n‐butylamine for 2,6‐dimethylphenol polymerization
Authors: Li Kuo‐Tseng , Lin Chen‐Chin 
Published: April 2003

Abstract2,6‐Dimethylphenol (2,6‐DMP) polymerization with a catalytic complex of Cu2O/HBr/N,N'‐di‐tert‐butylethylene diamine (DBEDA)/N,N‐dimethyl‐n‐butylamine (DMBA)/dibutylamine (DBA) was studied, in which DMBA was prepared in situ from the methylation of n‐butylamine over four different solid acid catalysts (two different γ‐alumina, one silica‐alumina, and one zeolite). The effectiveness of the unpurified methylation product solutions for promoting the 2,6‐DMP polymerization was strongly dependent on the type of solid acid catalysts used. The performance of the best one (untreated product solution from the methylation reactor with Condea γ‐alumina catalyst) was very similiar to that of the reagent grade DMBA. Infrared spectrum studies showed that DMBA acted as the external base for the 2,6‐DMP polymerization catalyst system to neutralize the excess hydrobromic acid and to increase the polymerization rate. © 1995 John Wiley & Sons, Inc.
Synthesis of pyridine‐moieties‐containing poly(acylhydrazone)s and solute separation through their membranes
Authors: Oikawa Eizo , Tamura Satoko , Arai Yohsuke , Aoki Toshiki 
Published: April 2003

AbstractPoly(acylhydrazone)s containing pyridine moieties were synthesized from 2,6‐pyridinedicaboxaldehyde and each of five dihydrazides. Although most of the polycondensates were insoluble or sparingly soluble and of low molecular weight, the polymers from malonyldihydrazide were highly soluble and readily gave tough films. Their performances as separation membranes were exammed in reverse osmosis, gas separation, and pervaporation (PV). The membranes showed a good performance in PV and were water permselective for aqueous alcohols and aprotic solutes, showing to be very effective to break azeotropes with high separation factors and to preferentially separate water from high concentration feeds, particularly in butanols and THF. Deviation from ideal flux, swelling degree, and some physicochemical parameters such as solubility parameter, molar volume, and vapor pressure were correlated to the membrane performances in a wide range of feed concentrations of the above two solute groups. © 1995 John Wiley & Sons, Inc.
Propene polymerization with MgCl2‐supported TiCl4/dioctylphthalate catalyst. I. Catalyst behavior
Authors: Yang Chun B. , Hsu Cheng C. 
Published: April 2003

AbstractSlurry polymerization of propene using MgCl2‐supported TiCl4/dioctylphthalate catalysts were carried out in a semibatch reactor at a constant pressure to examine the effects of polymerization conditions on catalyst activity and polymer isotacticity. The catalysts were prepared at 80, 90, and 105°C, which gave different compositions of chemical complexes associated with the diester. Five alkyl aluminums (triethyl, triisobutyl, tri‐n‐hexyl, tri‐n‐octyl, and isoprenyl) were studied as cocatalysts. Among these, triethyl aluminum was found to be most effective for the catalysts prepared at 80 and 95°C, and tri‐n‐hexyl aluminum for the catalyst prepared at 105°C. Dimethoxydiphenyl silane and 2,2,6,6‐tetramethylpiperidine were employed to study their effects as an external Lewis base for the catalyst prepared at 105°C. In both cases, a small amount of either base resulted in significant increase in activity and isotacticity, which can be attributed to the high level of phthaloyl chloride complex in the catalyst. © 1995 John Wiley & Sons, Inc.
Propene polymerization with MgCl2‐supported TiCl4/dioctylphthalate catalyst. III. Effects of polymerization conditions on molecular weights and molecular weight distribution
Authors: Yang Chun B. , Hsu Cheng C. 
Published: April 2003

AbstractIn propene polymerization over the MgCl2‐supported TiCl4/dioctylphthalate (DOP) catalyst, the weight‐ and number‐average molecular weights and the molecular weight distribution (MWD) of polypropene products and of the isotactic and atactic polymer portions were studied. The average molecular weights and MWD were found to be independent of time. The isotactic polymer had higher molecular weight and broader distribution than the atactic portion by almost an order of magnitude. An increase in temperature and cocatalyst/catalyst ratio resulted in lowering molecular weight due to increasing transfer reaction. Alkyl aluminum was used as a cocatalyst, and the molecular weight did not vary significantly with different alkyl groups. Of the three external bases studied, 2,2,6,6‐tetramethyl piperidine (TMPIP), dimethoxydiphenyl silane (DMDPS), and t‐butylmethyl ether (TBME), the addition of a small amount of one of the first two bases caused a substantial increase in both molecular weight and polydispersity of the isotactic polymer. Those increases leveled off quickly with increasing amounts of the external base. On the other hand, both average molecular weights and polydispersity of the atactic polymer decreased with a net increase in the molecular weight of the whole polymer. TBME, however, has no significant effect on either molecular weight or MWD. These effects are discussed in the context of the roles of the external base in propene polymerization. © 1995 John Wiley & Sons, Inc.