bluuebunny/crossref_metadata_2025 huggingface dataset:
New perfluoropolyether soft segment containing polyurethanes
Authors: Tonelli Claudio , Trombetta Tania , Scicchitano Massimo , Castiglioni Giovanni
Published: April 2003

New segmented polyurethanes (FPU) with perfluoropolyether (PFPE) blocks have been synthesized by a two‐step process. In the first step, a fluorinated isocyanate end‐capped prepolymer has been obtained by reaction of a fluorinated macrodiol with alicyclic diisocyanates in the presence of solvent. The following chain extension has been carried out by reaction of the prepolymer with short hydrogenated polyols giving a polymeric matrix. Tensile properties, dynamical–mechanical (DMA), and calorimetric (DSC) analyses have been evaluated, and relationships between chemical structure and final properties are established. These polymers show unusual low‐temperature elastomeric behavior, due to the low glass transition (Tg) of the continuous fluorinated phase. In general, with respect to traditional polyurethanes (HPU), thermal stability and chemical resistance are strongly improved by the effect of the highly inert fluorinated chains. © 1995 John Wiley & Sons, Inc.
Nonisothermal crystallization of poly(ethylene terephthalate) and its blends in the injection‐molding process
Authors: Okamoto Masami , Shinoda Yoshihiro , Kinami Nobuyuki , Okuyama Tomoko
Published: April 2003

We investigated the nonisothermal crystallization during the cooling process of injection molding of poly(ethylene terephthalate) (PET), PET/talc, and PET/Surlyn blends. We applied the isothermal crystallization parameters obtained by the Hoffman–Lauritzen theory to the kinetics of nonisothermal crystallization and then calculated the relative crystallinity χ/χc as a function of the mold temperature. χ/χc were nicely interpreted by calculation without effect of the pressure history on crystallization in PET and PET/talc (1 wt %) blends. In contrast, in the PET/Surlyn (3 wt %) blend, crystallization occurred at a lower mold temperature than predicted by our calculation. The transmission electron micrograph near the surface of the injection‐molded PET/Surlyn blend showed deformation and stretching of dispersed Surlyn particles, suggesting that orientation of the PET matrix proceeds with the flow in processing. The orientation of the PET matrix resulted in acceleration of the crystallization in the injection molding. © 1995 John Wiley & Sons, Inc.
Use of factorial experimental design in static and dynamic light scattering characterization of water‐soluble polymers
Authors: Hester R. D. , Flesher L. M.
Published: April 2003

When characterizing solutions of random coil polymers by static light scattering (SLS) or dynamic light scattering (DLS), linear regression is used to fit experimental data to theoretical relationships. These relationships are expressed as polynomial equations, which contain two independent variables—sample concentration and scattering angle—and a response or dependent variable that is related to radiation intensities (SLS) or intensity fluctuations (DLS). The coefficients of the terms in the polynomial are used to estimate parameters such as molecular weight and polymer coil radius of gyration. One major problem during data analysis involves deciding which polynomial model is appropriate for use with the data that inherently contains a high level of random noise that is produced by the presence of dust in the solutions. Dust is an especially troublesome problem when dealing with large polymers in aqueous solutions. Polynomial models having more terms than justified are unacceptable because the coefficients of these models are excessively corrupted by the noise. Thus, conclusions from unjustified models can be erroneous. This article discusses use of a factorial experimental design technique that obtains an acceptable model for fitting light scattering data containing high levels of random noise. © 1995 John Wiley & Sons, Inc.
Transfer of copper and zinc in polymeric materials oxidized in contact with brass
Authors: Lin D. G. , Eliseeva I. M.
Published: April 2003

Transfer particularities were investigated for zinc and copper in polymeric films oxidized in contact with brass. Inversion in selectivity of alloy component transfer proved to be the fact for a wide range of polymers. The results obtained are explained by an irregular development of oxidative transformations within the polymer layer, thus leading to a two‐stage mode of transfer in the case of catalytically active metals. The influence of various factors (e.g., oxidation temperature, polymer film thickness, polymer origin) on the level of ultimate concentrations of copper and zinc accumulated in polymers was considered. © 1995 John Wiley & Sons, Inc.
Poly(vinyl alcohol)–poly(sodium acrylate) composite hydrogels. I. Kinetics of swelling and dehydration
Authors: Graiver Daniel , Hyon Suong‐Hyu , Ikada Yoshito
Published: April 2003

Incorporation of sodium polyacrylate (NaPAA) in poly(vinyl alcohol) (PVA) gels as small, uniformly distributed precipitates greatly accelerates their volume expansion during swelling in water to form hydrogels. In addition to the usual water absorption, the swelling process includes dissolution of the precipitates that leads to a locally high osmotic pressure that in turn causes a further increase in water penetration and volume expansion. During swelling, soluble NaPAA is released into the water phase with a high initial release rate that then decreases continuously. The release can be described by an exponential decay function with a power dependent rate coefficient. Because the diffusion of NaPAA through the PVa walls is too slow to account for this release rate, a morphology of a closed cell foamlike structure with interconnecting channels is proposed. An aqueous solution of NaPAA seems to diffuse out of the hydrogel through these channels. © 1995 John Wiley & Sons, Inc.
Copper (II) transfer through carboxylic ion‐exchange membranes prepared by paste method
Authors: Alexandrova I. , Iordanov G.
Published: April 2003

Interpolymer carboxylic membranes were prepared by the paste method. Transport of copper through the membrane was investigated by using a system containing HCl (receiver solution) and CuCl2 (feed solution). The transfer rate was found to be greatly affected by the membrane composition and HCl concentration in the receiver solution. A membrane based on poly(vinyl chloride)/poly(methyl methacrylate‐co‐divinylbenzene) with 5 wt % divinylbenzene showed the highest transfer rate. © 1995 John Wiley & Sons, Inc.
Mechanism and kinetics of adiabatic anionic polymerization of ϵ‐caprolactam in the presence of various activators
Authors: Kim Kap Jin , Kim Yun Young , Yoon Byung Sook , Yoon Kee Jong
Published: April 2003

Nylon 6 was prepared by adiabatic anionic polymerization of ϵ‐caprolactam using hexamethylene dicarbamoyl dicaprolactam (HDC), cyclohexyl carbamoyl caprolactam (CCC), or phenyl carbamoyl caprolactam (PCC) as activators and sodium caprolactamate (NaCL) as a catalyst at various initial reaction temperatures ranging from 130 to 160°C. Adiabatic temperature rise was recorded as a function of polymerization time to investigate polymerization kinetics. Kinetic parameters for polymerization, which are more accurate than data reported to date, could be obtained by fitting the temperature rise data with a new polymerization kinetic equation involving crystallization exotherm and thermal conduction. The polymerization rate highly depended on the chemical structure of the activator used, which indicates that the initiating step where the activator is attacked nucleophilically by NaCL is a very important reaction step, affecting the overall polymerization rate. CCC showed the fastest polymerization rate, whereas HDC and PCC showed the medium and the slowest rate, respectively. The contributions of crystallization exotherm and thermal conduction to the resultant temperature rise during polymerization were significant, when the initial reaction temperature was lower than 140°C. In all cases, the molecular weight obtained from intrinsic viscosity measurement was greater than the expected molecular weight. This may be attributed to the branching and/or crosslinking reaction through Claisen‐type condensation reactions. © 1995 John Wiley & Sons, Inc.
A study on the preparation and properties of the heterogeneous cation‐exchange membranes of sulfonated polystyrene/divinyl benzene on an acetal base
Authors: Lam‐Leung Suei Y. , Li Huan R.
Published: April 2003

The heterogeneous acetal‐based membranes containing 50, 60, 70, 80, and 90% (w/w) of the sulfonated polystyrene crosslinked with 7% divinyl benzene were fabricated and studied. In addition, the heterogeneous acetal‐based membranes of 85% (w/w) sulfonated polystyrene crosslinked with 1, 4, and 7% divinyl benzene were also prepared and studied. The gel water content, dimensional stability, ion‐exchange capacity, area and specific ohmic resistance, permselectivity, and rate of ion exchange of the acetal‐based membranes were determined. The sulfonated polystyrene crosslinked with 7% divinyl benzene resin was found to be the better material for preparing the acetal‐based membrane with comparable good characteristics. A commercially available heterogeneous membrane (Shanghai Chemicals, 3361) of dry‐molding sulfonated polystyrene–divinyl benzene resin was used as the reference membrane for the present investigation. © 1995 John Wiley & Sons, Inc.
Poly(ethylene‐2,6‐naphthalenedicarboxylate) fiber for industrial applications
Authors: Jager J. , Juijn J. A. , van den Heuvel C. J. M. , Huijts R. A.
Published: April 2003

Poly(ethylene‐2,6‐naphthalenedicarboxylate) (PEN) has been prepared from commercial dimethyl‐2,6‐naphthalenedicarboxylate (DM‐2,6‐NDC) and ethylene glycol (EG) according to the well‐known transesterification/polycondensation route. PEN fibers, intended for industrial yarn applications, were obtained by melt spinning and drawing high molecular weight PEN. The properties of these yarns were measured in detail and compared with those of PET industrial yarns. The development of molecular orientation in the spinline is more pronounced for PEN than for PET. Because the yield stress is lower, PEN yarns can more easily be drawn. Breaking tenacities of PEN yarns are comparable with those of PET yarns, but the modulus is much higher and the thermal shrinkage is lower. Therefore, PEN yarns have a better dimensional stability than PET yarns. In addition, it was demonstrated that the thermal resistance of PEN yarns is better. © 1995 John Wiley & Sons, Inc.
Measurement of diffusivities of sulfur mustard (SM) and its analog oxygen mustard (OM) in cured butyl, nitrile, and natural‐rubber sheets by weight gain and FTIR–ATR methods
Authors: Banerjee Susanta , Semwal Rajendra P. , Agarwal Seema
Published: April 2003

The breakthrough time of butyl, nitrile, and natural‐rubber sheets (cured) of different compositions against a potent chemical warfare (CW) agent have been determined using the spot disc test (SDT) method. It was observed that butyl rubber is the best material in comparison to nitrile and natural rubber for protection against sulfur mustard (SM). One of the butyl formulations provides more than 100 h protection against SM. The diffusion coefficient of oxygen mustard (SM analog) for the same formulation (F8) and one nonblack butyl formulation (F5) was determined by weight gain as well as by FTIR–ATR methods. Both methods provide consistent results and the diffusion coefficient of oxygen mustard (OM for butyl rubber is in the order of 10−9cm2/s. The diffusion coefficient of SM for the form lation F8 and F5 was also determined from the SDT retardation time. © 1995 John Wiley & Sons, Inc.
Statistical design in isothermal aging of polyimide resins
Authors: Sutter James K. , Jobe J. Marcus , Crane Elizabeth A.
Published: April 2003

Recent developments in research on polyimides for high temperature applications have led to the synthesis of many new polymers. Among the criteria that determines their thermal oxidative stability, isothermal aging is one of the most important. Isothermal aging studies require that many experimental factors are controlled to provide accurate results. In this article we describe a statistical plan that compares the isothermal stability of several polyimide resins, while minimizing the variations inherent in high‐temperature aging studies. © 1995 John Wiley & Sons, Inc.
Measurement of cure in optical fiber coatings by infrared microspectroscopy
Authors: Louden J. D.
Published: April 2003

A method suitable for measuring the state of cure in acrylate optical fiber coating is described. Both the outermost (secondary) and the innermost (primary) coatings cure states can be determined. The method is reproducible and suitable for manufacturing process control and quality control in produced fiber. © 1995 John Wiley & Sons, Inc.
New measures of polydispersity from rheological data on polymer melts
Authors: Shroff R. , Mavridis H.
Published: April 2003

The rheological properties of polymer melts depend strongly on the underlying molecular structure: molecular weight distribution, and long chain branching. It is of considerable importance, both fundamental and practical, to relate the molecular architecture to polymer melt rheology. The focus of the present work is in extracting a measure of polydispersity from rheological data. Various polydispersity measures that have been proposed in the literature are critically examined and their limitations are pointed out. New measures of polydispersity are proposed that overcome these limitations. The evaluation of the various polydispersity measures is performed by reference to rheology fundamentals, with model calculations and examples drawn from industrial practice. The issues of eliminating molecular weight and temperature effects in characterizing polydispersity are comprehensively addressed. The presence of small levels of long chain branching in an otherwise linear polymer alters most of these measures of polydispersity dramatically, while no detectable change appears in the molecular weight distribution obtained using a gel permeation chromatograph. It is demonstrated that the polydispersity measures proposed in the present work, and which are extracted from frequency response data in the linear viscoelastic region, can be used reliably to characterize polydispersity in polymer melts. © 1995 John Wiley & Sons, Inc.
Physical principles of using polyelectrolyte hydrogels for purifying and enrichment technologies
Authors: Budtova T. , Suleimenov I.
Published: April 2003

The main physical regularities which allow one to use a strongly charged hydrogel in purifying and/or enrichment technologies are analyzed. The proposed cyclic method is based on the two known phenomena—the salt concentration redistribution in the presence of the polyelectrolyte hydrogel and the reversible gel contraction under electric current. It is shown that in order to obtain high degrees of purification and/or concentration the salt concentration must be lower than that of the polymer. Under these conditions, there is no dependence on the nature of the salt and the cycle may be repeated several times without regeneration of the gel. © 1995 John Wiley & Sons, Inc.
Ring‐opening polymerization of ethylene oxide by anion initiation using sulfadiazine as parents compound
Authors: Huang Junlian , Wang Haiyuan , Zhou Cunling
Published: April 2003

A new kind of anion initiator using sulfadiazine as the parent compound was prepared by the reaction of sulfadiazine with epoxy ethylene, and then the metal potassium. The structure of the intermediate was characterized in detail by NMR, MS, UV, IR, and DSC. Ring‐opening polymerization of epoxy ethylene could be carried out by this initiation system. The molecular weight of the polymerized product, polyethylene oxide with a sulfadiazine end group (PEOsf), is in the range of 3000–4000. © 1995 John Wiley & Sons, Inc.
Terpene–anhydride resins as coating materials
Authors: Trumbo D. L. , Giddings C. L. , Wilson L. R. A.
Published: April 2003

Low to moderate molecular weight terpene–anhydride resins were synthesized and evaluated in coatings applications. The terpenes used were terepinolene, β‐pinene, and alloocimene. The comononmers used were maleic or itaconic anhydride. The terpene–anhydride resins were used to formulate solvent‐borne coatings with an epoxy or diol as a coreactant. The coatings were evaluated as films over aluminum or steel panels. When a diol was used as a coreactant, the film properties were relatively poor. When epoxy was used as a coreactant, the properties of the films were much improved in terms of resistance to solvent and hardness. © 1995 John Wiley & Sons, Inc.
Empirical models for melt blowing
Authors: Milligan M. W. , Haynes B. D.
Published: April 2003

A large data set obtained for melt blowing using a single hole die has been used to develop empirical models which express final average fiber diameter as a function of dimensionless independent variables. The resulting empirical models or equations have been compared to multihole melt‐blowing die data. The conclusion of this investigation is that appropriate first‐order variables have been identified and the dependence of average final fiber diameter on the independent variables has been established. The resulting model should prove very useful for use in melt‐blowing process control and in the design of melt‐blowing equipment for polypropylene with an MFR between 500 and 900. © 1995 John Wiley & Sons, Inc.
Chemical stability of polyimide membranes at temperatures near Tg
Authors: Rezac Mary E. , Koros William J. , Miller Stephen J.
Published: April 2003

The success of polymeric membranes for use in high temperature gas separation applications relies, in part, on the chemical stability of these materials in separation environment. This paper details experimental evaluation of the stability of the membranes prepared using a polyimide as the selective separating layer when exposed to butane/butene/hydrogen mixtures at temperatures near the glass transition temperature of the polymer, 310°C. Further, the effects of small concentrations of sulfur and ammonia compounds in the feed mixture were investigated, as was the influence of a simulated air leak. The gas transport rates and selectivities were unchanged when testing in the hydrocarbon/hydrogen environment for over 30 days. Further, no changes in transport properties were observed when hydrogen sulfide or ammonia was added to the feed mixture. However, degradation due to oxygen exposure was observed. The chemical stability of the polyimide layer appears to be sufficient to be utilized for the separation of high temperature petrochemical streams. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of model associative polymers
Authors: Jenkins Richard D. , Bassett David R. , Silebi Cesar A. , El‐Aasser Mohamed S.
Published: April 2003

Model linear associative polymers with number average molecular weights in the range of 16,600 to 100,400 were prepared by connecting blocks of commercially available poly(oxyethylene) with isophorone diisocyanate, followed by capping with either hydroxyl, dodecyl, or hexadecyl linear alkyl end groups. The molecular weight distributions measured by gel permeation chromatography are somewhat broad, as expected from the synthetic method. In a 40/60 by weight solvent mixture of diethylene glycol monobutyl ether (Butyl Carbitol) and water, the relative viscosities of model associative polymers and poly(oxyethylene) standards collapsed to a single master curve; viscosity average molecular weights obtained from the intrinsic viscosities measured in this solvent mixture compare favorably to those obtained by size exclusion chromatography. In water, the model polymers with alkyl end groups interact at extremely dilute concentrations to produce a pronounced increase in reduced viscosity that increases as concentration and alkyl end group length increase. The Huggins parameters for solutions of model associative polymers with the hexadecyl and dodecyl end groups vary between 1 and 16, and decrease as molecular weight increases, as hydrophobe length decreases, and as temperature increases. The concentration at which the viscosity data deviate from the Huggins equation is less than the polymer coil overlap concentration, which is on the order of 1–3 g/dL, as estimated from the reciprocal of the intrinsic viscosity data. This suggests that we can define a critical network concentration c*h as the concentration at which the associative polymers hydrophobic end groups first interact to form a rheologically significant network. However, the transition occurs over a concentration range, rather than at a particular critical micellar concentration, as is the case of ordinary surfactants or hydrophobically modified hydroxyethylcellulose. The dimensions of the associative polymer coils in solution, and the signs and relative magnitudes of heat and entropy of dilution as estimated from classical molecular theories, are similar to those obtained by other authors for poly(oxyethylene) homopolymers. A physical model based on equilibrium kinetics for the association process correctly mimics the dependence of viscosity on molecular weight and concentration, and indicates that the free energy of association must become larger as the length of the alkyl end groups becomes larger relative to the hydrophilic backbone. © 1995 John Wiley & Sons, Inc.
Kinetics of adsorption and desorption of water‐soluble associative polymers on planar titanium dioxide surfaces by ellipsometry
Authors: Filippov Leonid K. , Silebi Cesar A. , El‐Aasser Mohamed S.
Published: April 2003

The adsorption and desorption kinetics of water‐soluble associative polymers with different molecular weights on crystals of titanium dioxide [TiO2(001)] have been studied by ellipsometry. The model water‐soluble associative polymers used in the kinetic study are nonionic polyurethanes based on polyethylene glycol, and have average molecular weights of 17,000, 51,000, and 100,000 with a C16H33 linear alkyl group on each end of the molecule. It is shown that the adsorption and desorption kinetics over a wide range of polymer concentrations is governed by: (1) the kinetics of adsorption and desorption of polymer chains at the interface, (2) the kinetics of adsorption and desorption at the interfaces as well as simultaneous diffusion in the adsorbed layer, and/or (3) diffusion in the adsorbed layer. The existence of regimes (1), (2), and (3) of the adsorption and desorption kinetics are justified by using the experimental data for the adsorption and desorption of water‐soluble associative polymers with different molecular weights. It is shown that the adsorption is an irreversible process for the strongly convex adsorption isotherms. Equations were derived to calculate: (a) the rate constant for polymer adsorption and desorption processes, (b) the coefficient of diffusion, (c) the activation energy of diffusion in the adsorbed layer, and (d) the time needed to attain the equilibrium states for the adsorption and desorption processes by using adsorption and desorption kinetics data with associative polymers of different molecular weights at different polymer concentrations. © 1995 John Wiley & Sons, Inc.
Orientational ordering of grafted nonmobile rod polymers
Authors: Vugmeister B. E. , Hong Daniel C.
Published: April 2003

We studied the orientational ordering of grafted rod polymers on the surface. The rod polymers were nonmobile and allowed to have two configurations: either lying down on the surface or standing up. The only interaction between the rods were hard core interaction. We computed the orientational order parameter using the recently developed random local field theory. We found that the order parameter increased monotonically as a function of the concentration of the rods and, thus, there existed no pancake‐brush transition. © 1995 John Wiley & Sons, Inc.
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

This 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

In 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

Film 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

The 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

Rubber 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

A 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

Coir 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

Poly(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

Poly(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

The 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

A 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

Thiophosphoryl 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

The 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

Various 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

Tri‐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

2,6‐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

Poly(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

Slurry 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

In 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.