bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion and sorption of organic liquids through polymer membranes. VI. Polyurethane, neoprene, natural rubber, nitrile butadiene rubber, styrene butadiene rubber, and ethylene propylene diene terpolymer versus organic esters
Authors: Khinnavar Rajashekhar S. , Aminabhavi Tejraj M.
Published: April 2003

Sorption and diffusion of eight esters into six commercial polymer membranes have been studied by immersion/weight gain experiments to determine how the transport behavior is affected by the choice of the solvent molecules and the chemical structures of the polymer membranes. The temperature dependence of transport parameters was found to follow the Arrhonius activation theory. It has been proved that the kinetics of equilibrium concentration can be described by the first‐order kinetic rate equation. Furthermore, the results of transport parameters have been discussed in terms of the size, shape, and chemical nature of the diffusant molecules.
Semi‐ and fully‐interpenetrating polymer networks based on polyurethane–polyacrylate systems. XII. The influence of polymerization pressure on morphology and properties
Authors: Hourston D. J. , Huson M. G.
Published: April 2003

Polyurethane–poly(methyl acrylate) interpenetrating polymer networks (IPNs) of fixed composition (50/50) were prepared at 60°C and a range of pressures. Increased synthesis pressures generally resulted in improved mixing of the two networks. The physical properties of the IPNs initially improved as a result of the enhanced mixing, reaching a maximum for specimens synthesized at 250 MPa. The poorer properties for the IPNs, prepared at higher synthesis pressures, have been ascribed to decreased uniformity in the network.
Synthesis and properties of cationic resins derived from polyether/polyester‐modified epoxy resins
Authors: Lee Lung‐Ta , Yang Chin‐Ping
Published: April 2003

Four polyether and one polyester‐modified cationic resins were synthesized by reacting polyether/polyester‐modified epoxy resins with 2‐ethylhexanol‐blocked‐toluene diisocyanate (2‐EH‐blocked TDI) and diethanolamine and subsequently neutralizing the resins with acetic acid. Four different polyethers and one polycaprolactone diol (PCP) were used to react with epoxy resin to form polyether‐modified epoxy resins (1a–d) and polyester‐modified epoxy resin (1e). The extent of reaction of epoxy resin and polyether or polyester was evaluated by the change of epoxy equivalent weight and the gel permeation chromatography curve of the resulting product. Cationic resins were dissolved in suitable solvents and were mixed with deionized water to form emulsions. Some factors, such as pH value of emulsion, solvent content, and applied voltage affecting the emulsion and electrodeposition properties, were investigated. Cationic resins, prepared from PPG (#1000)‐modified epoxy resins, yielded a wider pH range of stable emulsion and also yielded deposited films with a pleasing appearance. PEG (#1000)‐modified cationic resins produced a higher deposition yield, but higher throwing power was obtained by deposition of the PCP (#530)‐modified cationic resins.
The effect of chemical composition on the miscibility of styrene/acrylonitrile/fumaronitrile terpolymers with styrene/acrylonitrile copolymers
Authors: Warakomski John M. , Dion Robert P.
Published: April 2003

Blends were prepared of styrene–acrylonitrile–fumaronitrile (SANFN) terpolymers with styrene–acrylonitrile (SAN) copolymers and of SANFN terpolymers with SANFN terpolymers of different compositions. Miscibility was determined by differential scanning calorimetry. For three SANFN terpolymer compositions containing 11–17% fumaronitrile, a range of miscible SAN copolymers was defined. The miscibility can be predicted by using a Flory–Huggins‐type mean‐field approach.
Monitoring thermoset polymerization by using piezoelectric measurements
Authors: Perrissin‐Fabert I. , Feve M. , Jayet Y. , Merle G.
Published: April 2003

The electric impedance of a piezoelectric element placed inside a polymeric system depends on the viscoelastic property of the polymer. Its measurement is a sensitive and nondestructive method for monitoring the curing of such materials. The validity of this new method is shown by comparison with traditional viscoelastic and ultrasonic techniques.
Photosensitive polyimides developable with basic aqueous solutions (II)
Authors: Takano Kei , Mikogami Yukihiro , Nakano Yoshihiro , Hayase Rumiko , Hayase Shuzi
Published: April 2003

Positive and negative photosensitive polyimides developable with basic aqueous solutions are reported. The results consist of poly amic acids and naphthoquinone diazides in which sulfonate groups have to be substituted at 4‐position. It depends on the naphthoquinone structures whether positive or negative patterns are obtained. In order to fabricate resist patterns, High‐Temperature‐Post‐Exposure‐Process (HIT‐PEB) must be utilized. The reaction mechanisms are also discussed. © 1992 John Wiley & Sons, Inc.
Annealing of commercial block polypropylene. I. Thermal and physical properties
Authors: Ito Jun‐Ichi , Mitani Katsuo , Mizutani Yukio
Published: April 2003

Investigations were carried out regarding the effect of annealing of ethylene–propylene block copolymer (block PP) moldings on their tensile impact strength (TIS), brittle temperature (Tb), and other mechanical properties. Annealing near the melting point improves TIS and Tb as the result of recrystallization. With a system in which a minute amount of talc is added as a nucleating agent, the degree of improving TIS through annealing is considerably less than that with a nonnucleated system. The effect of annealing on the impact strength is due to changes of fine texture and morphology of crystallites and is explicable by recrystallization and polymer diffusion. © 1992 John Wiley & Sons, Inc.
Self‐condensation of aqueous hexa(methoxymethyl) melamine: Effects of concentration, pH, and alcohol content
Authors: Snyder Donald M. , Vuk Thomas J.
Published: April 2003

Dilute aqueous solutions of hexa(methoxymethyl)melamine have been found to form colloidal suspensions of cross‐linked polymer under acidic conditions in a manner similar to nonalkylated methyolmelamines. Experiments have shown that the time to onset of turbidity is quite sensitive to solution pH, with a sharp maximum in the rate observed at pH 1.22 under the specific conditions used in this study. Solutions were unexpectedly stable at pH values below the maximum. Suppression of the condensation process was also observed in the presence of added alcohols, with the magnitude of the rate‐retarding effect influenced by the alcohol structure. © 1992 John Wiley & Sons, Inc.
Free‐radical polymerization of styrene with a binary mixture of symmetrical bifunctional initiators
Authors: Yoon Won Jung , Choi Kyu Yong
Published: April 2003

The kinetics of bulk styrene polymerization catalyzed by a binary mixture of symmetrical bifunctional initiators has been investigated. When the bifunctional initiators having different thermal stabilities are mixed, an unsymmetry in the initiator functions is formed in situ via propagation, chain transfer, and termination reactions. For the quantification of the polymerization kinetics, a kinetic model has been developed using the molecular species modeling technique. For various polymerization conditions, good agreements between the model predictions and experimental data have been obtained. It is shown that polymerization rate and molecular weight can be easily regulated under isothermal reaction condition by changing the initiator composition. A comparison of the detailed kinetic model with a simple kinetic model for monofunctional initiators has also been made to illustrate the molecular weight increasing effect of the bifunctional initiator system. © 1992 John Wiley & Sons, Inc.
DAC‐coated resins for hemoperfusion
Authors: Yan Jun , Xu Rongnan , Zhou Peiqing , Lu Zhounian , Wu Xinhua , Wu Zhaoguang
Published: April 2003

This paper reports the use of diacetylchitin (DAC)‐coated macroreticular resin HS‐12 as an adsorbent in hemoperfusion. Sixteen dogs acutely intoxicated with pentobarbital were hemoperfused, either with the coated resin (n = 8) or raw resin (n = 8). The results showed the coating greatly improved resin hemocompatibility. The clearance rates for the coated and raw resins were 195 mL/min for the first 5 min at a flow rate of 200 mL/min. In clinical practice, 12 patients who were acutely intoxicated by drugs, such as pentobarbital and phenobarbital, were hemoperfused and saved. © 1992 John Wiley & Sons, Inc.
Supermicron poly(butyl acrylate)/polystyrene core‐shell latexes
Authors: Cook D. G. , Rudin A. , Plumtree A.
Published: April 2003

Latex particles of up to 2 μm can be made by standard emulsion polymerization methods, but attempts at larger sizes usually results in a crop of smaller particles or coagulation of the latex. In this work, it is shown that use of an oil‐soluble initiator (2,2′ azodiisobutyronitrile [AIBN]) provides a means by which large (6 μm diameter) polybutyl acrylate latex particles can be made by sequential core‐shell polymerizations. It is suggested that the limited water solubility of AIBN decreases the formation of secondary particles and that the lower ionic strength of the water phase enhances stability of the latex compared to a conventional persulfate initiator. To further minimize formation of secondary particles, long reaction times and progressively larger proportions of seed latex are used in successive reactions. © 1992 John Wiley & Sons, Inc.
Effects of CF4/O2 gas plasma power/exposure time on dielectric properties and breakdown voltages of PVDF films
Authors: Mammone Robert J. , Binder Michel
Published: April 2003

Dielectric properties and electrical breakdown strengths were measured on 12‐μm‐thick poly(vinylidene fluoride) films before and after exposure to various power levels and exposure times in a 96% CF4/4% O2 gas plasma. Significant changes in dielectric constant, dielectric losses, and breakdown voltages were observed. Breakdown voltages for PVDF films as a function of exposure time and plasma power appear to go through a maximum. © 1992 John Wiley & Sons, Inc.
Speciality polyurethane soft segments. II. Mixing studies in micro‐RIM using polyether diamine oligomers containing backbone urea moieties
Authors: Harris Robert F. , Anderson Robert M. , Shannon David M.
Published: April 2003

Polyether polyamines containing preformed urea moieties in their backbone, prepared by the reaction of aminated polyglycols with urea, were used to fabricate high modulus urea polymers by reaction injection molding (RIM) on micro‐RIM equipment. A formulation was studied based on a 2000 g/mol molecular weight polyether diamine containing about 4 internal urea moieties/molecule as the soft segment and Isonate 143L and diethyltoluenediamine (DETDA) as the hard segment (60 vol %). Mixing was measured by the temperature rise produced by injection of the components into an adiabatic cup as a function of the B‐side Reynolds number at the mixhead. B‐Side Reynolds numbers of about 300 or above were required for adequate mixing in this system. Plaques were made and compared to the corresponding polyether diamine without urea moieties. The formulation containing preformed urea moieties in the soft segment produced urea polymers with superior properties such as higher modulus, greater strength, increased hardness, superior organic solvent resistance, and improved green strength at demold. Impact properties were reduced. © 1992 John Wiley & Sons, Inc.
Transmittance and mechanical properties of PMMA‐fumed silica composites
Authors: Abramoff Bennet , Covino Josephine
Published: April 2003

The transmittance, flexure strength, Young's modulus, and Vickers hardness of poly(methyl methacrylate) (PMMA), filled with fumed silica, was measured. Transmittance decreased with increasing content of filler. At 2 vol % filler content, composites had a higher transmittance with a lower surface area of fumed silica (larger primary particle size) because the lower surface area filler was better dispersed. At 4 vol % filler content, composites had a higher transmittance with a higher surface area fumed silica (smaller primary particle size). Flexure strength and Young's modulus of the composites was measured using three point bending. Addition of fumed silica led to a decrease of strength. Also, addition of fumed silica led to an increase of Young's modulus and Vickers hardness. © 1992 John Wiley & Sons, Inc.
Gel permeation chromatography of vegetable‐oil‐based printing ink vehicles
Authors: Erhan S. Z. , Bagby M. O.
Published: April 2003

The apparent weight‐average molecular weights (Mw) of ink vehicles made from soybean, safflower, sunflower, cottonseed, and canola oils were compared by gel permeation chromatography (GPC), and the correlation between viscosity and Mw of these vehicles was established. Apparent Mw of vegetable oil gels that were used in vehicle preparation were also obtained by GPC. © 1992 John Wiley & Sons, Inc.
Effect of epoxy–amine stoichiometry on cured resin material properties
Authors: Palmese G. R. , McCullough R. L.
Published: April 2003

Sizings and/or surface treatments are commonly employed to enhance the interaction of fiber reinforcements in polymer matrix composites. These modifications can induce physical and chemical interactions that cause local stoichiometric imbalances to occur that can affect the properties of the polymer matrix in the vicinity of the fiber surface. This work reports the results of an experimental study of the influence of stoichiometric imbalance on the thermoelastic properties of an epoxy–amine resin. It is shown that the modulus and glass transition temperature are significantly affected by relatively small variations in stoichiometry. These results suggest that a fiber‐induced interphase region in thermosetting composites can exhibit material properties that are significantly different from those of the bulk resin. © 1992 John Wiley & Sons, Inc.
Photograft copolymerization of methyl methacrylate on viscose fiber using titanium(III) chloride–potassium persulfate redox initiator in a limited aqueous system
Authors: Maji Tarun Kumar , Banerjee Amar Nath
Published: April 2003

The graft copolymerization of methyl methacrylate (MMA) onto viscose fibers were studied under photoactive conditions with visible light using titanium(III) chloride—potassium persulfate as redox initiator in a limited aqueous system. Polymerization carried out in the dark at 40 ± 1°C produced little graft copolymer whereas that in the presence of light at 40 ± 1°C produced significant grafting. Percent grafting, percent total conversion, and grafting efficiency (%) were studied by varying time, initiator concentration, monomer concentration, solvent composition, and pH of the medium. High percent grafting (∼ 200%), high grafting efficiency (∼ 98%), and percent total conversion (∼ 47%) were obtained with little homopolymer formation. A suitable mechanism for grafting has been discussed and also the characterization of the grafted fibers were studied by Fourier transform infrared (FTIR) spectroscopy, thermogravimetry and scanning electron microscopy (SEM). © 1992 John Wiley & Sons, Inc.
XPS surface studies of injection‐molded poly(phenylene ether)/nylon 6,6 and poly(phenylene ether)/HIPS blends
Authors: Bhatia Qamar S. , Burrell Michael C. , Chera J. J.
Published: April 2003

The surface compositions of a series of poly(phenylene ether)/nylon 6,6 blends (PPE/PA), and PPE/HIPS blends, prepared by melt compounding and injection molding, have been quantitatively measured using XPS. For PPE/PA blends, the surface is dominated by the PA component for blends containing more than 25 wt % PA in the bulk. The enrichment of the PA component, which is actually the component of highest surface free energy, is rationalized in terms of the bulk morphology that consists of PPE domains in a PA continuous phase. Blends prepared by reactive extrusion processes, which form compatibilizing PPE/PA copolymers, show a decrease in surface PA enrichment with increasing copolymer content in the final blend. PPE/HIPS blends have a surface composition equal to the formulated value over the entire composition range, for both molded and solvent cast blends. The addition of 5% PVME to a 60/40 PPE/HIPS blend results in a molded surface containing 35–40 wt % PVME. © 1992 John Wiley & Sons, Inc.
Study of the interactions of model polymer surface with cold plasmas. II. Degradation rate versus pressure and gas flow rate
Authors: Shi M. K. , Clouet F.
Published: April 2003

This work deals with the influence of pressure, gas flow rate, and gas mixture on the etching rates of polymer model molecules such as hexatriacontane (C36H74) and octadecyl octadecanoate (OOD) treated in an oxygen or argon plasma. Mass spectrometry and optical emission spectroscopy have been used to monitor the formation and evolution of the fragments coming from chain breaking in terms of their concentration and emission intensity, respectively. It was demonstrated that pressure and gas flow rate are two important parameters in the interaction of cold plasmas and of polymer surfaces. The results obtained can be explained by combined effects such as electron energy and its density, residence time, “quenching effect,” as well as chemical reactions. © 1992 John Wiley & Sons, Inc.
Studies on tributyl tin methacrylate (TBTM). VI. Thermal and tensile behavior of copolymer of tri‐n‐butyl tin methacrylate and methyl methacrylate
Authors: Samui A. B. , Patri M. , Deb P. C.
Published: April 2003

The thermal and tensile properties of polytributyl tin methacrylate (PTBTM) and n‐tributyl tin methacrylate–methyl methacrylate (TBTM—MMA) copolymers have been studied. Thermogravimetric study showed that with increasing the TBTM content in the copolymer the thermal stability decreases. The glass transition temperature (Tg) decreases continuously as the TBTM content increases. All the polymers showed multistep decomposition. MS study showed that in addition to monomer formation several other side reactions also take place during degradation, leading to formation of other products. Studies on tensile properties show that the tensile strength decreases with increasing TBTM content, whereas elongation at break increases. © 1992 John Wiley & Sons, Inc.
The study of curing behavior and thermal properties for soybean oil fatty acid‐modified glycidyl methacrylate
Authors: Lee Wen‐Fu
Published: April 2003

The characteristics of glycidyl methacrylate (GMA)–modifiers, including the polymerization properties, curing properties, and thermal stability, were studied. The degree of crosslinkage for (GMA–modifier)polyols increases with increasing hexamethoxymethylmelamine (HMMM) content and reaches maximum when HMMM content is about 40 wt %. The gels obtained from thermal free‐radical polymerization for GMA‐modifier monomer decrease with increasing acid value. UV curing experiments indicate that the energy of ultraviolet might be insufficient to promote the curing reaction through transetherification with short‐term irradiation. Kinetic parameters for the thermal decomposition of the polymer were measured with TG thermograms. © 1993 John Wiley & Sons, Inc.
Arylidene polymers. XVIII. Synthesis and thermal behavior of organometallic arylidene polyesters containing ferrocene derivatives in the main chain
Authors: Abd‐Alla Mohamed M. , El‐Zohry Maher F. , Aly Kamal I. , Abd‐El‐Wahab Mohamed M. M.
Published: April 2003

A new interesting category of organometallic polyesters based on diarylidenecycloalkanones containing ferrocene derivatives in the polymer main chain has been prepared by interfacial polycondensation of 1,1′‐dichlorocarbonyl ferrocene or 1,1′‐dichlorocarbonyl‐4,4′‐diiodoferrocene with 2,5‐bis(p‐hydroxybenzylidene)cyclopentanone, 2,5‐divanillylidenecyclopentanone, 2,6‐bis(p‐hydroxybenzylidene)cyclohexanone, 2,6‐divanillylidenecyclohexanone, and 2,7‐bis(p‐hydroxybenzylidene) cycloheptanone. The resulting polyesters were characterized by elemental analyses, infrared spectroscopy, solubility, and viscometry measurements. The thermal behavior of the synthesized polymers was evaluated by thermal gravimetric analysis and correlated with their structures. The crystallinity of all polymers were examined by x‐ray diffraction analysis. Moreover, the electrical conductivity of a selected example of polymer was investigated above the temperature range (300–500 K) and showed that it followed an Arrhenius‐type equation with activation energy 2.09 eV. © 1993 John Wiley & Sons, Inc.
The chemistry and development of branched PRF wood adhesives of low resorcinol content
Authors: Scopelitis E. , Pizzi A.
Published: April 2003

Phenol–Resorcinol–Formaldehyde (PRF) resins of good adhesive performance, and of resorcinol content much lower than in traditional PRF cold‐setting adhesives, were prepared by introducing small amounts of urea as a branching unit during preparation of the resin. Resorcinol contents as low as 10.6% were obtained by this method while still maintaining an acceptable pot‐life of the resin. Resorcinol contents as low as 8%, still with a good adhesive performance, were obtained, although the pot‐life obtained was too short. GPC, FT–IR and C13 NMR indicated that the small amount of urea branching unit used leads to the reduction of resorcinol content mostly by rapid doubling of the average linear length of the PF intermediates and of the final PF oligomers. Tridimensional branching in the liquid resin, contrary to what was previously thought, does not appear to be an important contributory factor and better adhesives are often prepared when branching is totally, or almost totally, absent. Reduction of resorcinol content is achieved simultaneously by two mechanisms: (i) the decrease of resorcinol percentage on resin solids due to the rapid lengthening (doubling) of average oligomers length and (ii) the need for these resins to operate at lower solids content, due to the increased viscosity obtained during their preparation. © 1993 John Wiley & Sons, Inc.
Relationship between melt viscosity and dielectric relaxation time for a series of epoxide oligomers
Authors: Koike Tsuneo
Published: April 2003

Melt viscosity has been investigated for a series of bisphenol‐A type epoxide oligomers with different weight‐average mol wts (M̄w), ranging from 388 to 2640. The temperature dependence of the melt viscosity is described by the Williams–Landel–Ferry (WLF) equation. The melt viscosity η is correlated with both the direct current (dc) conductivity σ and the dielectric relaxation time τ. The two relationships between these three properties, σ·ηκ = const (0.63 ≦ κ ≦ 1.12) and η/τℓ = const (0.73 ≦ ℓ ≦ 1.06), are experimentally derived. Both exponents, κ and ℓ, depend on the M̄w of the oligomer. The lower M̄w oligomer has the larger value of κ. The κ value is close to unity for the low M̄w oligomer, which agrees with Walden's rule, σ·.η = const, applicable to most low mol wt liquids. The ℓ value is near unity for the epoxide oligomer with higher M̄w than 2000, which means that the melt viscosity is proportional to the dielectric relaxation time. The low M̄w oligomer (M̄w < 2000), on the other hand, has a smaller value of ℓ below unity. The result indicates that the melt viscosity is not proportional to the dielectric relaxation time for the low M̄w epoxide oligomer, whose dielectric α‐relaxation is not governed by the Debye equation. © 1993 John Wiley & Sons, Inc.
Surface graft polymerization of ionic monomers onto poly(ethylene terephthalate) by UV‐irradiation without degassing
Authors: Uchida Emiko , Uyama Yoshikimi , Ikada Yoshito
Published: April 2003

Graft polymerization of anionic and cationic monomers was performed onto the surface of poly(ethylene terephthalate) (PET) film with a simultaneous UV irradiation method, but using no photo‐sensitizer. To effect graft polymerization, the PET film was immersed in an aqueous solution containing a monomer and periodate (NaIO4) of appropriate concentrations, followed by UV irradiation without degassing. The monomers used were 2‐acrylamide‐2‐methylpropane sulfonic acid and acrylic acid as anionic and N,N‐dimethyl aminopropyl acrylamide and dimethyl aminoethyl methacrylate as cationic monomer. The role of NaIO4 at the polymerization was to make the concentration of oxygen dissolved in solution zero by the photochemical reaction with the oxygen. The surface structure of grafted films was characterized by their contact angle, dyeing, X‐ray photoelectron spectroscopy, and zeta potentials. Graft polymerization took place, not merely on the outermost surface, but also within the thin surface region of the PET film without any change in bulk properties. © 1993 John Wiley & Sons, Inc.
TG–Temperature property (TgTP) diagram for thermosetting systems: Anomalous behavior of physical properties vs. extent of cure
Authors: Wang Xiaorong , Gillham John K.
Published: April 2003

The relationships between the isothermal physical properties in the glassy state of amorphous thermosetting crosslinked polymers and chemical conversion are anomalous and complex. In this manuscript, a generalized framework for correlating the basic physical properties of a high‐Tg thermosetting amine/epoxy system vs. extent of cure at isothermal temperatures from above Tg to deep in the glassy state is reported in terms of the Tg‐Temperature Property (TgTP) Diagram. The framework arises from consideration of the isothermal shear modulus and the isothermal physical aging rate vs. extent of cure, both of which display maxima and minima throughout a wide range of temperatures below Tg. Use of Tg as a direct measure of conversion results in linearization of the relationships between the temperatures of the maxima and minima of the physical properties and extent of cure in the TgTP Diagram. The anomalous behavior is related to specific phenomena, such as the glass transition (vitrification) and the glassy‐state β‐transition (Tβ), the temperatures of which change with conversion, and also to gelation. The different types of behavior of a property of the material vs. extent of cure correspond to different regions in the diagram. Such simple diagrams are intellectually useful for understanding the properties of materials for both undercured materials (with change of conversion) and fully cured materials (with change of stoichiometric ratio). © 1993 John Wiley & Sons, Inc.
An X‐ray investigation of terminally carboxyl oligo (ethylene oxide) monomethyl ethers‐substituted side‐chain liquid crystalline polysiloxanes
Authors: Jeng Gow‐Pyng Cheng , Kuo Jen‐Feng , Chen Chuh‐Yung
Published: April 2003

4′‐[Oligo(ethylene oxide) monomethyl ether carbonyl] biphenyl‐4‐yl 4‐(alkenyloxy) benzoate side‐chain liquid crystalline (LC) polysiloxane polymers with various lengths of a terminal group and spacer were prepared. The mesophase structure and transition temperature of those polymers were investigated using methods of X‐ray diffraction, polarized optical microscopy, and differential scanning calorimetry, respectively. The mesophases of the polymers were smectic ones. The layer spacing d1s and the side‐chain distance of d2s obtained were around 29–34 Å and 4.4–4.6 Å, respectively. d1s were much shorter than twice the lengths of the side chains presumed in the fully extended conformation. Hence, the two‐layer end‐on packings or the packing with overlapping of tails model seemed not able to interpret the mesophase structure of those polymers studied. The effects of temperature on the mesophase microstructure of 4′‐[ethylene oxide monomethyl ether carbonyl] biphenyl‐4‐yl 4‐(pentenyloxy) benzoate side‐chain LC polysiloxane polymer were also studied using the X‐ray diffraction method. It was found that both d1 and d2 of the polymer in the mesophase temperature range became shorter with decreasing temperature and the long‐and short‐range order could remain, to some extent, at temperatures above the isotropic transition temperature and temperatures below the melting temperature. © 1993 John Wiley & Sons, Inc.
Application of the microbond technique. IV. Improved fiber–matrix adhesion by RF plasma treatment of organic fibers
Authors: Biro David A. , Pleizier Gerald , Deslandes Yves
Published: April 2003

The microbond technique is a modification of the single‐fiber pullout test for measuring interfacial shear strength. Briefly, a cured microdroplet of material is debonded in shear from a single fiber. Ultra‐high modulus polyethylene (Spectra) fibers and aramid fibers (Kevlar) were treated using a radio frequency plasma in order to increase the interfacial bond between the fibers and an epoxy resin. The treated fiber surface was subsequently analyzed by X‐ray photoelectron spectroscopy (XPS). Plasma treatment resulted in an increased concentration of oxygen containing functionalities on the fiber surface. The interfacial shear strength as determined by the microbond test increased by 118% for the Spectra fibers and by 45% for the Kevlar fibers with the same epoxy resin. Scanning electron microscopy indicated little change of the surface topography of either fiber following plasma treatment. Effects of friction and surface composition of the plasma‐treated fibers is discussed. © 1993 John Wiley & Sons, Inc.
Densimetry for on‐line conversion monitoring in emulsion homo‐ and copolymerization
Authors: Canegallo Stefano , Storti Giuseppe , Morbidelli Massimo , Carrà Sergio
Published: April 2003

The use of on‐line densimetry to monitor conversion in batch emulsion polymerization reactors are investigated. Some characteristics of the sampling circuit connecting the reactor to the densitometer, which allow one to obtain reliable on‐line estimations of monomer conversion in the whole range of conversion, are discussed in detail. Moreover, the amount of collected data provides a practically continuous monitoring of the system evolution in time, which allows one to estimate directly the rate of conversion as a function of time. The technique has been applied both to homopolymerization systems [i.e., styrene (STY) and methyl methacrylate (MMA)] as well as to copolymerization systems [i.e., STY–MMA, acrylonitrile (ACN)–MMA, vinyl acetate (VAC)–MMA]. In the latter case, the density measurements are combined with a reliable model which provides for polymer composition as a function of conversion, in order to obtain accurate measurements of monomers conversion. © 1993 John Wiley & Sons, Inc.
Statistical mechanics of “dual‐mode” sorption in polyimides
Authors: Silverman B. D.
Published: April 2003

A statistical mechanical description of the gas takeup or sorption in polyimides below their glass transition temperature is proposed. The model treated is formally similar to Fowler's early model of monolayer adsorption of gases on solid surfaces. It is expected to be appropriate for polymers exhibiting a significant degree of crystallization, e.g., the aromatic polyimides at temperatures well below their glass transition temperature. The model assumes that the penetrant gas molecules bind to a spectrum of states characterized by a distribution of binding energies. If it is assumed that the penetrant molecules bind to the polymer with only two well‐defined interaction energies, namely, zero as well as some particular finite value, a “dual‐mode” expression for sorption is obtained. It is pointed out that this “dual‐mode” or “two‐state” model is not consistent with some recent data obtained on carbon dioxide sorption in a polyimide. Two other simplified models are examined, a “uniform‐density‐of‐states” model and a “three‐state” model. The present treatment yields explicit expressions for the temperature dependence of the sorption parameters. This dependence reflects the thermodynamic redistribution of penetrant molecules among the available fixed density‐of‐states as the temperature is varied. It is pointed out that the temperature dependence of the Langmuir capacity constant obtained from nonlinear least squares fitting the standard “dual‐mode” sorption expression to the polyimide sorption data may lead to an erroneous inference concerning the decrease in “unrelaxed volume” as the temperature is increased from well below the glass transition temperature of the polymer. The “three‐state” model yields sorption isotherms that parallel the data of Sada et al. closely. This suggests the presence of multiple carbon dioxide binding sites in the polyimide. © 1993 John Wiley & Sons, Inc.
The modification of porous chromato‐gel surface for liquid chromatography by poly(4‐vinylpyridine) microgels
Authors: Ma Guanghui , Fukutomi Takashi , Nozaki Shohei
Published: April 2003

A porous chromato‐gel for liquid chromatography was modified by fixing poly(4‐vinylpyridine) (P4VP) microgels of homogeneous size on its surface, and the microgels were further quarternized by using iodomethane or bromoacetic acid, in order to vary the chromatographic characters of the original chromato‐gel. The character of the porous chromato‐gel before and after modification was investigated by the retention volume (Ve) of dextran and pullulan standards with various molecular weights (MW: 2 × 10–2 × 106 g/mol). It was found that a single layer of microgels had been fixed compactly on the surface of the chromato‐gel, and the retention volume (Ve) and the limit exclusion molecular weight (LEMW) [the molecular weight where the d(Ve)/d(MW) became maximum] were affected remarkably by the sizes and chemical characters of the fixed microgels. The retention volume and LEMW decreased when the pore size formed by microgels was smaller than the hole size of the chromato‐gel, while the reverse result was obtained when the pore size formed by the microgels became larger than the hole size of the chromato‐gel. After the microgels were quarternized, the retention volume decreased further. Furthermore, the chromato‐gel quarternized by bromoacetic acid showed excellent chromatographic character. This study provided an advantage in that the chromatographic characters of the chromato‐gel can be varied and improved easily. © 1993 John Wiley & Sons, Inc.
Optimization of covalently coupling enzymes to polymeric membranes: EPR studies of papain
Authors: Zhuang Ping , Butterfield D. Allan
Published: April 2003

In an effort to better understand bioreactor systems, papain (EC 3.4.22.2) was covalently immobilized onto vinyl alcohol/vinyl butyral copolymer (PMB) membrane by means of glutaraldehyde (GA), 1,1'‐carbonyldiimidazole (CDI), or 2‐fluoro‐1‐methylpyridinium toluene‐4‐sulfonate (FMP). Various kinetic and performance characteristics of the immobilized papain were evaluated. It was found that the characteristics of the membranebound papain depended on the immobilization methods. The CDI‐ and FMP‐immobilized papain bioreactors showed better storage and thermal stability than did the GA‐immobilized papain bioreactor, although the apparent Michaelis constant, Km, of the GA‐immobilized papain was closer to the free enzyme than to the corresponding CDI‐ and FMP‐immobilized enzymes. In separate experiments, a 6‐carbon spacer was inserted between the membrane surface and the covalently bound enzyme. It was found that the insertion of a spacer reduced the disturbance of the enzyme systems, resulting in Km values intermediate between the free and directly bound enzymes for all three immobilization methods. Electron paramagnetic resonance spectroscopy was also used to investigate the conformational change and the active site structure of papain. It was found that the active site SH group of papain immobilized with a 6‐carbon spacer had faster motion than that of directly bound enzyme, but slower motion than that of the free enzyme. With both direct‐coupling and with a spacer, the SH group motion at the active site of papain by CDI and FMP immobilizations was similar, but slower than the corresponding GA immobilization. The conformational changes of the active site of papain upon immobilization with and without a spacer were in agreement with the functional properties of the enzyme. There was a good correlation between the motion of spin‐labeled cysteine in the active site of papain and kinetic properties of this protease: As motion slowed, Km increased and Vmax decreased. Of the immobilization procedures used, GA immobilization with a spacer yielded kinetic and structural characteristics most similar to the free enzyme while providing increased stability and reusability relative to the latter. © 1993 John Wiley & Sons, Inc.
The cure of epoxy novolacs with aromatic diamines. II. Statistical parameters of the resulting networks
Authors: Oyanguren P. A. , Williams R. J. J.
Published: April 2003

The buildup of the network arising from the reaction of an epoxy novolac (derived from a phenol—formaldehyde novolac resin), with 4,4'diaminodiphenylsulfone (DDS), was modeled using a kinetic‐statistical procedure that takes into account (i) the complex structure of the starting novolac, (ii) the actual polymerization kinetics including the different reactivity of primary and secondary amine hydrogens, and (iii) the formation of intramolecular cycles. Predictions of gel conversion and sol fraction were in excellent agreement with experimental results. Glass transition temperaturesTg's of networks prepared at different stoichiometries were predicted using Nielsen's equation (J. Macromol. Sci.‐Rev. Macromol. Chem.,C3, 69, 1969) and the concentration of elastic chains arising from the model. Theoretical predictions explained the presence of a maximum in the experimentalTgfor formulations containing a 20% amine excess. Experimental values ofTgas a function of conversion, for stoichiometric samples, were correlated using a model proposed in the literature. © 1993 John Wiley & Sons, Inc.
The interaction of water with polyurethanes containing block copolymer soft segments
Authors: Schneider N. S. , Illinger J. L. , Karasz F. E.
Published: April 2003

The saturation water uptake and nonfreezing water, determined as a function of temperature in a polyurethane containing the pure polyethylene oxide soft segment (I) and in polyurethanes containing block copolymer polyethylene oxide/polypropylene oxide soft segments (II), show significantly different behavior. In sample I, the water content and nonfreezing water are only weakly dependent on temperature from 276 to 333 K. In the samples based on II, with various ratios of the hydrophilic and hydrophobic segments, there is a strong decrease in solubility with temperature and a steep drop above 303 K. The nonfreezing water exhibits a parallel trend. This behavior is interpreted in terms of the temperature‐dependent phase compatibility of the polyethylene oxide and polypropylene oxide segments of II. © 1993 John Wiley & Sons, Inc.
Curing of unsaturated polyester resins: Effects of comonomer composition. II. High‐temperature reactions
Authors: Huang Yan‐Jyi , Chen Chaur‐Jeng
Published: April 2003

The effects of comonomer composition of the curing kinetics of unsaturated polyester (UP) resins at 100–120°C were investigated by differential scanning calorimetry (DSC) and infrared spectroscopy (IR) over the entire conversion range. One commercial UP resin, UP2821, with 6.82 unsaturated CC bonds per polyester molecule, was used. For styrene/UP2821 reactions, experimental results of the initial and maximum reaction rates by DSC at 100–120°C revealed that the styrene content, as well as the reaction temperature, would affect the formation of microgel structures. As the initial molar ratio of styrene to polyester CC bonds increased, the styrene swelling effect could enhance the intramicrogel crosslinking reactions, while the styrene dilution effect could diminish the intermicrogel crosslinking reactions. The competition between the two reactions would depend on the reaction temperatures. Finally, a microgel‐based reaction mechanism was proposed for the high temperature reactions. © 1993 John Wiley & Sons, Inc.
The reaction engineering of the anionic polymerization of isoprene
Authors: Chang C. C. , Halasa A. F. , Miller J. W.
Published: April 2003

The anionic solution polymerization of isoprene with n‐butyllithium (n‐BuLi) initiator and tetramethylethylenediame (TMEDA) modifier or n‐butyllithium (n‐BuLi)initiator and tripiperidinophosphine (TPPO) modifier was studied and kinetic and reactor models are proposed for both systems. Reactor conversion, molecular weight distribution, and polymer glass transition temperature had been calculated from the model and compared favorably to actual data for various combinations of reactor system and operating conditions. Simulations of the models can be used to design reactor systems, and predict polymer properties of a large‐scale operation from results of small‐scale batch reactor runs. © 1993 John Wiley & Sons, Inc.
Aerobic biodegradation of cellulose acetate
Authors: Buchanan Charles M. , Gardner Robert M. , Komarek Ronald J.
Published: April 2003

Two separate assay systems were used to evaluate the biodegradation potential of cellulose acetate: anin vitroenrichment cultivation technique (closed batch system), and a system in which cellulose diacetate (CDA) films were suspended in a wastewater treatment system (open continuous feed system). Thein vitroassay employed a stable enrichment culture, which was initiated by inoculating a basal salts medium containing cellulose acetate with 5% (v/v) activated sludge. Microscopic examination revealed extensive degradation of CDA (DS = 2.5) fibers after 2–3 weeks of incubation. Characterization of the CA fibers recovered from inoculated flasks demonstrated a lower average degree of substitution and a change in the mol wt profiles.In vitroenrichments with CDA (DS = 1.7) films were able to degrade > 80% of the films in 4–5 days. Cellulose acetate (DS = 2.5) films required 10–12 days for extensive degradation. Films prepared from cellulose triacetate remained essentially unchanged after 28 days in thein vitroassay. The wastewater treatment assay was less active than thein vitroenrichment system. For example, approximately 27 days were required for 70% degradation of CDA (DS = 1.7) films to occur while CDA (DS = 2.5) films required approximately 10 weeks before significant degradation was obtained. Supporting evidence for the biodegradation potential of cellulose acetate was obtained through the conversion of cellulose [1‐14C]‐acetate to14CO2in thein vitroassay. The results of this work demonstrate that cellulose acetate fibers and films are potentially biodegradable and that the rate of biodegradation is highly dependent on the degree of substitution. © 1993 John Wiley & Sons, Inc.
Crystallization of rare earth oxide‐filled polypropylene
Authors: Liu Jingjiang , Tang Gongben , Qu Guijie , Zhou Huarong , Guo Qipeng
Published: April 2003

A study has been made of the crystallization behavior of polypropylene (PP) filled with rare earth oxides under isothermal conditions. These rare earth oxides include lanthanum oxide (La2O3), yttrium oxide (Y2O3), and a mixture of rare earth oxides containing 70% Y2O3 (Y2O3–0.70). A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt. During isothermal crystallization, dependence of the relative degree of crystallinity on time was described by the Avrami equation. It has been shown that the addition of any of the three rare earth oxides causes a considerable increase in the overall crystallization rate of PP but does not influence the mechanism of nucleation and growth of the PP crystals. The analysis of kinetic data according to nucleation theories shows that the increase in crystallization rate of PP in the composites is due to the decrease in surface energy of the extremity surfaces. The relative contents of the β‐form in the composites are somewhat higher than that in the plain PP. However, the contents of the β‐form in the plain PP and the composites are all very low relative to those of the β‐form and the influence of the formation of the β‐form on the crystallization kinetics can be neglected. © 1993 John Wiley & Sons, Inc.
Effect of solid‐state curing on the viscoelastic properties of poly(phenylene sulfide)
Authors: Scobbo James J.
Published: April 2003

PPS is a thermosetting/thermoplastic resin. The resin, upon exiting the polymerization process, is generally a low viscosity, low molecular weight material. The thermosetting character is therefore exploited in a solid state cure process in the presence of air at elevated temperatures. This produces a resin with a more desirable property profile. Melt state dynamic mechanical measurements have been made on a series of cured PPS resins to elucidate structural changes that occur on the molecular level during the cure process. Increases in viscosity, non‐Newtonian behavior, and relative elastic response were observed with increasing cure time and have been attributed to an increasing molecular weight and broadening molecular weight distribution achieved through branching/crosslinking. The effects of various environments on curing have also been investigated. © 1993 John Wiley & Sons, Inc.
Mixtures of tetrabromobisphenol‐A polycarbonate and bis (2‐ethoxyethyl) ether: Examples of a lower critical solution temperature
Authors: Beck H. N.
Published: April 2003

Tetrabromobisphenol‐A polycarbonate was found unexpectedly to form mixtures with the solvent bis(2‐ethoxyethyl) ether that display a lower critical solution temperature at about normal room temperature and less than about 10 wt % polymer. © 1993 John Wiley & Sons, Inc.
A generalized model to predict the viscosity of solutions with suspended particles. I
Authors: Sudduth Richard D.
Published: April 2003

Several suspension equations available in the literature have been found to have a common derivative form. This common derivative was found to be equivalent to a ratio of the intrinsic viscosity, [η], and a quantity, Vint, defined as the ldquo;relative suspension interaction volume” available for particle flow. Vint was, in general, found to be a relatively simple function of the suspension particle volume fraction, φ, the maximum particle packing fraction, φn, and a new variable, σ, defined as the particle interaction coefficient. Different forms of this common derivative were obtained by modifying VInt with a simple adjustment for the value for the interaction coefficient, σ. Integration of this generalized derivative yielded a generalized suspension viscosity equation that was found to predict the form of many suspension equations that have previously appeared in the literature. For example, by varying the interaction coefficient, σ, the Arrhenius equation resulted when σ = 0, the Kreiger‐Dougherty equation resulted when σ = 1, and when σ = 2, the Mooney equation resulted. Fractional values for the particle interaction coefficient were also found to be useful when optimizing the empirical fit of the literature data of Vand and Eiler. Additional insight from such a data fit can also be obtained from the magnitude of both the particle interaction coefficient, σ, and the packing fraction, φn. © 1993 John Wiley & Sons, Inc.
Preparation and performance of poly(vinyl butyral) membrane for ultrafiltration
Authors: Gotoh Masao , Tamiya Ellchi , Karube Isao
Published: April 2003

Ultrafiltration membrane was prepared from poly(vinyl butyral). The effects of membrane thickness, polymer concentration, evaporation time, and evaporation temperature, etc., on the performance of the resulting membranes have been studied. Dimethylacetamide was used as a casting solvent. The membrane formed by casting the polymer from a 15 wt % solution and evaporation at 25°C for 30 s had a flux value of 250 cm3 / cm2 h (4.8 kg/cm2, 26°C) at 92.9% rejection level for dextran sodium sulfate (average mol. wt. 550,000) separation. © 1993 John Wiley & Sons, Inc.