bluuebunny/crossref_metadata_2025 huggingface dataset:
Epoxy composites based on glass beads. I. Viscoelastic properties
Authors: Amdouni N. , Sautereau H. , Gerard J. F.
Published: April 2003

The viscoelastic behavior of glass beads composites are studied. Untreated, silane‐treated and elastomer‐coated glass beads were used, dispersed in a DGEBA–DDA–BDMA epoxy matrix. Using low frequency experiments, the three‐phase structure of coated glass bead composites is demonstrated. The characteristics of both the α and β relaxations of the epoxy networks are analyzed and discussed. The β relaxation is independent of volume fraction and glass treatment. On the contrary, the position of the α relaxation increases strongly with glass volume fraction and silane treatment. The introduction of the elastomer as a thin layer at the filler/matrix interface induces a large chain mobility, thus decreasing the temperature position of the α peak. © 1992 John Wiley & Sons, Inc.
The heterogeneous character of the dilute acid hydrolysis of crystalline cellulose. III. Kinetic and X‐ray data
Authors: Lin Chyong‐Huey , Conner Anthony H. , Hill Charles G.
Published: April 2003

Thirteen prehydrolyzed samples of cellulose, including native, mercerized, and regenerated materials were hydrolyzed in 1% and 1.5% sulfuric acid at 160, 170, and 180°C. Pseudo first‐order rate constants and weight average degrees of polymerization were determined for each sample. For all cellulose samples, data from several experiments were used to determine the dependence of the rate of hydrolysis on sulfuric acid concentration. The results obtained in this study indicate that Sharples' end‐attack model is consistent with kinetic data for the hydrolysis of cellulose II samples, but is not applicable to the hydrolysis of cellulose I samples. X‐ray diffraction analyses indicated that, for native and mercerized cellulose samples, structural changes during dilute acid hydrolysis are not significant. However, data for rayon indicated that such changes may need to be taken into account in analysis of the reaction kinetics.
Poly(butylene terephthalate)/high density polyethylene alloys. II. Mechanical properties and rheology
Authors: Joshi M. , Maiti S. N. , Misra A.
Published: April 2003

Alloys of poly(butylene terephthalate) (PBT) and high density polyethylene (HDPE) in 80 : 20 ratio were prepared using a polyethylene‐based ionomer as a compatibilizer. The effect of the addition of this compatibilizer on mechanical and rheological properties of the PBT/HDPE blends was examined. The mechanical properties studied were tensile, flexural, and impact properties as a function of ionomer content. Ultimate mechanical properties showed significant improvement on addition of ionomer. This has been attributed to an increase in the interfacial adhesion between the two phases in the presence of the compatibilizer. Rheological measurements showed that shear viscosity increased for the blend with the addition of the compatibilizer. An explanation for this behavior is presented on the basis of the theory of emulsions.
Crystallization of fiber‐reinforced poly(phenylene sulfide) composites. II. Modeling the crystallization kinetics
Authors: Desio Glenn P. , Rebenfeld Ludwig
Published: April 2003

The kinetic data obtained by differential scanning calorimetry for the isothermal crystallization from the melt of unreinforced poly(phenylene sulfide) (PPS) and of model carbon, aramid, and glass fiber‐reinforced PPS composites has been analyzed and modeled on the basis of the Avrami equation. The classical Avrami model provided a good description of the volume fraction crystallized for PPS and for those composites that did not exhibit transcrystallinity in thin‐film specimens. Nonlinear Avrami behavior was observed for those composite systems that did exhibit transcrystallinity, for which parallel and series dual Avrami models were used. A series crystallinity model, which corrects the volume fraction crystallized for structural, imperfections, was applied to all the systems, providing a reasonable modeling of the data. In this model, we postulate an initial primary crystallization followed by a secondary crystallization. The temperature dependencies of the Avrami rate constants were analyzed through Arrhenius relationships, and the resultant activation energies and frequency factors were interpreted in terms of nucleation and growth phenomena. We found the frequency factor for primary crystallization to be indicative of the nucleating abilities of the fiber surfaces and to correlate with the presence of transcrystallinity.
Mechanical properties of poly(ethylene terephthalate) fibers imparted hydrophilicity with aminolysis
Authors: Fukatsu Kazuhiko
Published: April 2003

Poly(ethylene terephthalate) fibers were aminolyzed with hydradine hydrate and ethylenediamine. The moisture regain of aminated fibers increased with increasing weight loss. It was suggested that the aminolysis reaction took place mainly in the amorphous regions. This leads to an increase of the accessibility of moisture. The mechanical properties of the aminated fibers were reported as a function of the weight loss by the aminolysis reaction; tenacity, stiffness, and wrinkle recovery were considered and discussed with regard to fine structures. General trends of decreasing tenacity, stiffness, and wrinkle recovery with increasing weight loss were observed for fibers aminated by hydrazine hydrate and ethylenediamine. Within this trend, there is difficulty for application of aminolysis that will not provide superior performance in the polyester fiber property such as tensile strength, stiffness, and wrinkle recovery.
Polymerization of acrylamide in the presence of calcium sulfate dihydrate and calcium sulfate hemihydrate
Authors: Stav Elisha , Bentur Arnon , Kohn David H.
Published: April 2003

The homopolymerization of acrylamide in water alone and also in the presence of calcium sulfate dihydrate and of calcium sulfate hemihydrate has been studied. Polymerizing acrylamide with the redox pair potassium persulfate—sodium bisulfite, the rate increased steadily with increasing initiator concentration. In the presence of up to 25% dihydrate, the rate was like that of acrylamide alone. However, when adding the “reactive” hemihydrate that is hydrated to the dihydrate concurrently with the progressing polymerization, the rate is somewhat slower in comparison with the two other systems. For determination of the compositions of the various reaction products, a method combining DTA and XRD data has been developed.
Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. II. Physical and mechanical properties of copolymer latex films
Authors: Lee K. C. , El‐Aasser M. S. , Vanderhoff John W.
Published: April 2003

Vinylidene chloride (VDC)–butyl methacrylate (BMA) copolymer latex films of various compositions (83 : 17, 60 : 40, 33 : 67 in mol %), prepared by batch and semicontinuous processes, were investigated for their physical properties by infrared spectroscopy, 13C solidstate NMR spectroscopy, X‐ray diffraction, solubility in various solvents, differential scanning calorimetry (DSC), and water vapor transmission rates (WVTR), and for their mechanical properties by dynamic mechanical spectroscopy (DMS), and tensile strength measurements. Semicontinuous latex films were found to be homogeneous in composition and amorphous in character. On the other hand, batch latex films containing high VDC monomer content were heterogeneous in composition and crystalline in character. These differences were found to reflect the effect of mode of monomer addition during the emulsion polymerization process, and correlated well to the results on kinetics, colloidal, and surface properties of the VDC‐BMA copolymer latexes, as described in the first part of this study.
Diffusion of acids into epoxy resin compositions
Authors: Kalenda P.
Published: April 2003

The study deals with the diffusion of aqueous acid solutions into diethylenetriamine‐hardened epoxy resins. The results obtained indicate that the diffusion of acids into epoxy resins is affected heavily by the epoxy resin structure, the epoxide group content in the respective resin, and thus also by the molecular mass of the resin concerned. A straight‐line dependence has been found between the diffusion coefficient of acids and the epoxide group contents in the resin.
Polymer matrix controlled release systems: Influence of polymer carrier and temperature on water uptake and protein release
Authors: Sheppard Norman F. , Madrid M. Yvette , Langer Robert
Published: April 2003

The release of bovine serum albumin (BSA) from two types of ethylene‐co‐vinyl acetate (EVAc) polymer matrices was studied over the temperature range 4–50°C. Protein release and weight change of the matrices were evaluated in uitro. The copolymers were characterized using differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). During release, the devices initially exhibit a rapid increase in weight to a maximum, followed by a more gradual decrease for the duration of the release. The time to the maximum weight and the magnitude of the maximum weight gain are temperature dependent. These effects are related to the temperature‐dependent diffusivity of the BSA and elastic modulus of the EVAc. The DSC and TMA reveal melting of the crystalline phase of the polymer. The corresponding loss of mechanical integrity of the polymer leads to anomalous weight gains at these temperatures. The observed swelling and release is explained by a model in which the osmotic pressure of the protein within the pore network causes elastic deformation of the polymer matrix.
Independent control of mechanical and chemical properties of monodispersed polystyrene–divinyl benzene microspheres by two‐step polymerization
Authors: Kobayashi K. , Senna M.
Published: April 2003

Monodispersed polystyrene (PS) latices of the particle size ranging between 4 and 10 μm were prepared by a conventional dispersion polymerization technique using poly‐(acrylamide) as a stabilizer. Styrene containing 2–20% of divinyl benzene (DVB) was subsequently polymerized on the surface of the latex by a seeded polymerization technique for the purpose of modifying the thermo‐mechanical and chemical properties of the microspheres. The softening temperature during hot pressing and the resistance against the dissolution on swelling in toluene or methyl ethyl ketone increased with increasing amount of DVB. The state of seeded polymerized particles was revealed to depend more on the total amount than the composition of the monomer added. By using the present technique, it is possible to prepare chemically stable, monodispersed microspheres with their diameters and softening temperature varying from 4.5 to 12 μm and from 106 to 126°C, respectively, with a free combination by choosing the appropriate dispersion polymerization condition and the amount of DVB during subsequent seeded polymerization.
Phosphorylation of the waste products from the dimethyl terephthalate production with the dimethyl ester of the 1,2‐di(methoxycarbonyl)ethane phosphonic acid
Authors: Todorov K. , Georgieva A. , Troev K. , Borisov G.
Published: April 2003

It is demonstrated that the dimethyl ester of 1,2‐di(methoxycarbonyl)ethane phosphonic acid can be used as a phosphorylating agent of the production wastes of dimethyl terephthalate. The products obtained have different characteristics depending on the mode of phosphorylation.
Analysis of the internal crazes in notched SAN
Authors: Shin E. S. , Hiltner A. , Baer E.
Published: April 2003

Crazing in styrene–acrylonitrile copolymer (SAN) under a triaxial stress state was examined. The damage zone that formed ahead of a semicircular notch under slow tensile loading consisted of two kinds of crazes: internal notch crazes that grew out from the notch root and discontinuous surface crazes. Examination of the damage zone in the optical and scanning electron microscopes revealed that the internal notch crazes sometimes extended through most of the thickness but never penetrated the free surfaces, whereas the surface crazes penetrated about 10–50 μm inward from the surface. Initially, the internal craze tips defined a crescent‐shaped zone. The plane strain elastic stress distribution at the zone boundary satisfied a constant mean stress condition, and the critical mean stress for craze tip growth was determined to be about 35 MPa. This value varied slightly for different resins but was independent of thickness. Propagation of the internal notch crazes occurred in a straight line parallel to the minor principal stress vector at the point of origin on the notch surface, whereas the surface crazes followed the minor principal stress trajectories. The presence of the internal notch crazes resulted in significant stress redistribution, the stress redistribution was described quantitatively using both the deviation of the craze trajectory from the minor principal stress trajectory, and the deviation of the zone shape from the critical elastic mean stress condition.
Studies of thermal transition behavior in plasticized poly(vinyl butyral‐co‐vinyl alcohol) with solid‐state NMR and thermal analysis techniques
Authors: Parker A. A. , Hedrick D. P. , Ritchey W. M.
Published: April 2003

Samples of plasticized poly(vinyl butyral‐co‐vinyl alcohol) (PVB) are found to exhibit multiple thermal transitions as observed by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Arrhenius plots using DSC and DMA data suggest that two of the transitions are glass‐type ones. Variable temperature solid‐state 13C‐NMR experiments show a temperature‐dependent line‐broadening pattern for all PVB backbone carbons with maximum broadening at 55°C or at about 50°C above the second‐order‐type transitions α1 and α2 as measured by DSC. Using Arrhenius plots, the NMR transition is found to best correlate with α1, which is consistent with glass transition behavior. The solid‐state NMR spectra also show that vinyl alcohol tacticity remains unresolved up to a temperature of about 95°C, beyond which line narrowing begins to occur. High‐temperature thermal transitions are also observed by DSC and DMA, which suggest that the onset of motion involving vinyl alcohol sequences may be responsible for these transitions.
Fibers made from concentrated viscose solutions
Authors: Laszkiewicz B. , Wcislo P. , Cuculo J. A.
Published: April 2003

Cellulose xanthate solutions with α‐cellulose content from 9 to 14% were obtained and their properties were examined. It has been found that viscoses containing urea are more stable and possess lower viscosity as compared with conventional viscoses. Properties of fibers obtained from viscoses with increased α‐cellulose content were discussed. It has also been found that such fibers show higher linear density and their tensile strength depends on the α‐cellulose content in the viscose.
Study by means of computerized spectroscopy of copolymerization grafting
Authors: Rodríguez A. S. , López B. E. M. , Fucugauchi L. A.
Published: April 2003

Experiments were performed in an attempt to explain the probable mechanism present in the polymeric grafting process and to determine the percentual ratio between N‐4‐[4‐(dietylamine) fenil] fenilmetilene‐2–5‐cyclohexadiene‐1‐ilidene‐N‐etil ammonium monomer and the sulfate (1 : 1) (Green Vinyl Malachite: GVM) in poly‐N‐vinylcarbazole/Green Vinyl Malachite, PNVC/GVM, specimens of the copolymerization product. Computerized spectroscopic techniques, optimized for maximum absorption and minimum effect noise, were utilized to subtract the spectral information of the GVM monomer noncopolymerized species from the macromolecular base with no special sampling techniques. The samples were processed using the standard PECDS software with the infrared Data Station. The copolymerization process resulted in a 52.91% concentration of a noncopolymerized fraction consisting of dimerized structures of the reactant monomer.
Studies on the effect of an external flaw on the tensile strength of short kevlar fiber–thermoplastic polyurethane composites
Authors: Kutty Sunil K. N. , Nando Golok B.
Published: April 2003

The effect of an external flaw on the tensile strength of short kevlar fiber–thermoplastic polyurethane (TPU) composites has been studied with respect to fiber content, fiber orientation, location of the external flaw, and the temperature of test. The composites showed a three‐step reduction in tensile strength with increasing flaw size. The critical flaw‐length region was shifted to higher flaw‐size levels with increasing fiber content. With increasing temperature, the critical flaw length was increased in the case of unfilled TPU, whereas it remained more or less constant in the case of short kevlar fiber‐filled–TPU composite.
Flame‐retardant PVC compound for cable applications
Authors: Reddy P. V. , Sridhar S. , Ratra M. C.
Published: April 2003

The low‐melting ternary sulfate and modified sulfate glasses based on transition metals like copper, nickel, and vanadium reduce the smoke generation during burning of the PVC compound. With increase in concentration of these glasses, the smoke‐density rating values decrease without appreciably altering the oxygen index values. Although trihydrated alumina and potash alum improve flame‐retarding properties, the latter cannot be used as it considerably reduces the thermal stability of the PVC compound. Formulations to meet the flame‐retardant requirements of a PVC compound suitable for cable sheathing have been developed.
Nylon 4/HEMA chemical homografted membrane
Authors: Lai J. Y. , Chen M. H. , Hsu K. Y.
Published: April 2003

To enhance the degree of grafting, homografting copolymerization of 2‐hydroxyethyl methacrylate (HEMA) onto nylon 4 using a chemical initiator has been attempted. The factors that affect the grafting copolymerization are the concentration of reactants, reaction time, and temperature. The dialysis permeabilities of solutes, water content, surface energy, mechanical properties, and blood compatibility of the membrane were investigated. Under the same reaction conditions, the degree of grafting by the homografting method is remarkably higher than of the heterografting method for the nylon 4–HEMA grafting system. The dialysis permeabilities of NaCl, vitamin B12, and ovalbumin of the homografted membrane with a 14.8% degree of grafting are 2.760, 0.392, and 0.073 × 10−5 cm2/min, respectively. These permeabilities are higher than the corresponding ones of ungrafted nylon 4 membrane. The mol ratios of adsorbed fibrinogen/albumin (F/A) of the heterografted membranes were found to decrease from 0.53 to 0.33, and the surface energy, to increase from 40.6 to 46.4 dyn/cm with the degree of grafting in the range of 12.5–29.9%, and their relationship is not remarkable for the homografted membranes for which the mol ratios of F/A are about 0.22–0.32 with the degree of grafting in the range of 14.8–103.8%. Observed from scanning electron micrographs of the membrane surface, denseness was found to be important to improve blood compatibility. Based on the dialysis permeabilities of solutes and the blood compatibility observed in this study, the homografted nylon 4/HEMA membrane can be considered as a hemodialysis material.
New composite reverse osmosis membranes made from poly‐2‐vinylimidazoline
Authors: Hurndall M. J. , Jacobs E. P. , Sanderson R. D.
Published: April 2003

Novel ultra‐thin film (UTF) composite reverse osmosis (RO) membranes were fabricated in situ by the interfacial polymerization of poly‐2‐vinylimidazoline (PVI) precursors and aromatic acid chloride crosslinking agents. The syntheses of three different forms of PVI, which were used as precursors, are described. 3‐(Chlorosulphonyl)benzoyl chloride, 3,5‐di(chlorosulphonyl)benzoyl chloride and 1,3‐benzenedicarbonyl dichloride were used as crosslinking agents. Both flat‐sheet and tubular membranes were fabricated and tested for their salt retentions and permeate fluxes. The RO performances of the two sets of tubular membranes PVI I and PVI II crosslinked with 3‐(chlorosulphonyl)benzoyl chloride, prepared according to optimized fabrication formulations, were recorded. These were 97.1 ± 0.1% retention; 730 ± 24 lmd flux and 98.2 ± 0.7% retention; 560 ± 150 L/m2/day (lmd) flux, respectively. The RO performances of initial tubular membranes made from PVI III and 3‐(chlorosulphonyl)benzoyl chloride was 97.0 ± 1.1% retention and 643 ± 74 lmd flux.
Compatibility studies on some solutions of rubber blends by ultrasonic techniques
Authors: Sidkey M. A. , Fattah A. M. Abd El , Abd El All N. S.
Published: April 2003

The degree of compatibility of the blend solutions, SBR—NR, SBR—BR, and SBR—NBR, dissolved in toluene was studied using ultrasonic methods. The variation of longitudinal ultrasonic velocity with composition is linear with SBR—NR and SBR—BR blends indicating compatible systems. For SBR—NBR the plots of ultrasonic velocity versus composition deviates from linearity according to the degree of compatibility of this blend system. The behavior was confirmed by heat of mixing calculations as well as ultrasonic attenuation measurements.
Oligomerization reactions in acrylonitrile‐N‐Naphthyl‐N′‐acryloylthiourea copolymers in the solid state
Authors: Hamza S. M. , Aly I. M.
Published: April 2003

N‐naphthyl‐N′‐acryloylthiourea homopolymer (PNAT) and a series of copolymers of acrylonitrile (AN) with N‐naphthyl‐N′‐acryloylthiourea (NAT) have been prepared and characterized by a variety of analytical and spectral methods. Thermogravimetry (TG) and differential thermal analysis (DTA) data showed that the homopolymer (PNAT) undergoes homolytic scission followed by depolymerization and decomposition upon heating. On the other hand the comonomer (NAT) initiates the nitrile oligomerization reaction in the copolymers upon heating. A mechanism for the initiation of the NAT units in the nitrile copolymers was also proposed.
Surface modification of polyethylene powder using plasma reactor with fluidized bed
Authors: Inagaki N. , Tasaka S. , Abe H.
Published: April 2003

The fluidization technique was applied for the surface modification of powder by plasma, and whether the technique was a practically useful one in the surface modification of powder or not was discussed. Polyethylene powder was used as a specimen to be modified. The oxygen plasma treatment of the polyethylene powder in the fluidized state showed a capability that the surface of the powder was changed from hydrophobic to hydrophilic. The contact angle of water for the treated powder surface was 51°C, which was estimated from the dynamic wicking data. The hydrophilic surface modification of the polyethylene powders in the fluidized bed required the operation of the plasma treatment for at least 3 h. The requirement of the plasma operation for long time rises mainly from large surface area of the powder. The oxygen plasma treatment led to the formation of oxygen functionalities including C  O and C(O)O groups at the outermost layer of the powder. The concentration of the CO and C(O)O functionalities reached 10 and 6% of the total carbon elements being in the XPS sampling depth, respectively. From these results we conclude that the fluidization technique is a useful manner in the surface modification of powder by plasma.
Effect of titanate coupling agent on electromagnetic interference shielding effectiveness and mechanical properties of PC–ABS–NCF composite
Authors: Chiang Wen‐Yen , Chiang Yung‐Shin
Published: April 2003

Nickel‐coated carbon fibers (NCF) treated with a coupling agent (CA) have been used for preparing composites of polycarbonate (PC) and acrylonitrile—butadiene—styrene (ABS) (90/10%) by melt blending. These composites have been evaluated for electromagnetic interference shielding effectiveness (EMI SE), mechanical properties, dispersion, and adhesion of the polymer to a filler using the scanning electron microscope (SEM). There is an improvement in the EMI SE, tensile strength, and impact strength of the composite when the carbon fiber is coupled with titanate CA. In loading NCF in composite, the optimum concentration of the CA Lica 38 used is about 2.0 phf combined with 1.5 phf calcium stearate (Ca.st.) (on the weight percentage of fillers); the composite can reach an SE of 50 dB by the coaxial transmission line test method.
Gelatin‐based composite polymers
Authors: Xu G. , Ruckenstein E.
Published: April 2003

Composite polymers containing gelatin and polymethyl methacrylate (PMMA) have been prepared by employing a gel pathway. The gels have been obtained by mixing mechanically at 50°C an aqueous solution of gelation containing a surfactant (sodium dodecylsulphate, SDS) with a monomer (methyl methacrylate, MMA) containing an initiator (AIBN). Two kinds of gels have been identified: high‐viscosity liquid gels, which lose their stability after half to two hours at room temperature, and solid‐type gels, which maintain their stability for a long time at room temperature. Composite polymer materials have been obtained by the polymerization of MMA in these gels. The polymerization of liquid‐type gels has been carried out in two steps: under mixing for the first hour and without mixing for 23 h. The polymerization of the solid‐type gels was performed in two different ways: (1) at room temperature for a few days followed by heating at 50°C for 4 h, and (2) the same procedure as for the liquid‐type gels (since at 50°C the solid‐type gels transform in liquid‐type gels).The phase behavior of the gels was investigated and scanning electron microscopy (SEM) was used to examine the morphology of the composite polymers. The swelling experiments have shown that at suitable gelatin concentrations, these composites are insoluble in water, methanol, octane, and cyclohexane but have a relatively high solubility in toluene.
Particle morphology in artificial composite polymer latex systems
Authors: Chen Yi‐Cherng , Dimonie Victoria , El‐Aasser Mohamed S.
Published: April 2003

Artificial composite latex particles were prepared by direct emulsification of a toluene solution of a blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The morphology of the composite particles from the higher molecular weight polymers showed polystyrene particles partially encapsulated by PMMA on the surface. On the other hand, for the lower molecular weight polymers, the reverse morphology was observed. The morphologies of the artificial composite latex particles swollen with solvent were examined when kept under agitation. The degree of phase separation between the two polymers in the composite particles was found to be affected by agitation to different extent, depending on the viscosity of polymer phases, the interfacial tension, and degree of mixing at interface between the two polymers. Extended agitation of the composite latex particles of high molecular weight polymers resulted in mixed morphologies that included individual PS and PMMA particles along with the original morphology of the composite particles. On the other hand, composite latex particles with the lower molecular weight polymers resisted complete phase separation due to lower interfacial tension and better mixing at the interface between the two polymers.
Effect of alkalies on suspension polymerization of vinyl acetate monomer, properties of poly(vinyl acetate) beads and poly(vinyl alcohols)
Authors: Verma S. K. , Arvindakshan P. , Bisarya S. C.
Published: April 2003

The use of weak alkalies such as sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3) and their 1 : 1 molar mixture, and strong alkalies such as sodium hydroxide (NaOH) and sodium methoxide (NaOMe) as pH controllers in suspension polymerization of vinyl acetate monomer (VAM) has shown to have diverse effects on the yield of resulting poly(vinyl acetate) (PVAC) beads. Carbon dioxide as such or the carbonate seems to influence the yield. Further, these alkalies have a deep‐seated effect not only on properties like viscosity, stereoregularity, glass transition temperature (Tg), and swelling coefficient (Q) of the PVAC beads but also on those of poly(vinyl alcohol) (PVA) obtained by alcoholysis of PVAC beads. The PVAC beads obtained using Na2CO3 showed higher viscosity, higher swelling coefficient (Q), and the PVA derived from these beads had higher Q, higher syndiotacticity/isotacticity ratio, and lower Tg.
Diffusion and sorption of organic liquids through polymer membranes. VIII. Elastomers versus monocyclic aromatic liquids
Authors: Harogoppad Shivaputrappa B. , Aminabhavi Tejraj M.
Published: April 2003

Sorption and diffusion of five monocyclic aromatic liquids—three halogenated benzenes, nitrobenzene, and aniline—with five engineering polymers—ethylene propylene diene ter‐polymer, nitrile butadiene rubber, styrene butadiene rubber, natural rubber, and neoprene—have been investigated in the temperature interval of 25–60°C. Solvent diffusivity into polymer membranes was determined from the immersion/weight gain experiments. Permeability coefficients were also calculated from the diffusion and sorption data. A temperature dependence of sorption and transport was also investigated to estimate the activation parameters. The experimental results and computed quantities were used to study the type of transport mechanism and the nature of polymer‐solvent interactions.
Effects of the t‐butyl substituent on the miscibility of polyarylates with polyamides
Authors: Dean B. D. , Harris J. E.
Published: April 2003

Amorphous polyarylates derived from 12–50 mol % of a t‐butyl‐substituted diacid, e.g., 5‐t‐butylisophthalic acid, exhibit miscibility with the amorphous phase of polyamides having aromatic and aliphatic character. Equally critical to blend miscibility is the aliphatic/aromatic carbon atom ratio (exclusive of the amide functionality) of the polyamide. An aliphatic/aromatic carbon atom ratio (α) greater than 1.4 but less than 2.5 is necessary. © 1992 John Wiley & Sons, Inc.
Use of continuous viscometer and light scattering detectors in characterization of polyolefins: Comparisons of data from individual and combined detectors
Authors: Pang Simon , Rudin Alfred
Published: April 2003

Molecular weights of polyethylenes have been characterized using differential refractometer (DRI), continuous viscometer (CV), and low‐angle laser light (LALLS) detection. In normal operation with the latter two detectors, the DRI is also employed as a concentration detector. The intrinsic viscosity of the whole polymer can be derived from the CV without use of a DRI concentration detector. If one calibrates the size exclusion chromatography (SEC) columns using the CV detector, it is possible to use this universal calibration relation and the CV detector to calculate number average molecular weight (Mn) of the polymer. Weight average molecular weight (Mw) of the sample can be calculated using data from the LALLS alone, without reference to the DRI. These variations of the analysis were tested and the advantages and limitations of the different detectors were compared using standard reference polyethylene samples in solution in 1,2,4‐trichlorobenzene at 145°C. © 1992 John Wiley & Sons, Inc.
Electrodeposition properties of self‐crosslinking epoxy–amine cationic resin modified by polycaprolactone diol
Authors: Yang Chin‐Ping , Ting Chih‐Yang
Published: April 2003

A self‐crosslinking polycaprolactone diol (PCD)‐modified epoxy–amine adduct was prepared by first synthesizing the PCD‐modified epoxy resin from diglycidyl ether of bisphenol A (DGEBA), PCD and bisphenol A (BPA), then reacting the partially pendant hydroxyl groups of this modified resin with 2‐ethylhexanol half‐blocked with toluene diisocyanate (2‐EH half‐blocked TDI), and finally reacting the terminal epoxy groups with secondary amines such as N‐methyl ethanol amine (MEA) and di(2‐methylisobutylketimino‐ethyl)amine (DKI). This epoxy–amine adduct was neutralized by acetic acid and could be dispersed in deionized water to form a stable emulsion, which could be used for the electrodeposition coating. The effects of solid content, pH value, solvent content of the emulsion, bath temperature, and applied voltage on the deposition yield and the throwing power of the resin were investigated. Meanwhile, the optimum crosslinking condition of the deposition film was also studied. It was found that the electrodeposition properties of the emulsion derived from the modified epoxy resin are superior to those of emulsion derived from the unmodified DGEBA epoxy resin.
Rheology of rigid–flexible liquid crystalline polymer/poly(methyl methacrylate) blends
Authors: Schild H. G. , Kolb E. S. , Gaudiana R. A. , Chiang Y. , Schwarzel W. C.
Published: April 2003

The random liquid crystalline copolymer poly(4,4′‐biphenylene azelate)‐co‐(2‐methyl‐1,4‐phenylene azelate), synthesized by condensation polymerization, was found to be soluble in chloroform and methylene chloride. DSC, rheology, and optical microscopy indicated that this LCP broadly melts at ca. 160°C to a weakly birefringent melt that becomes isotropic at approximately 180°C. DSC and optical microscopy of blends with poly(methyl methacrylate) (PMMA) at wLCP = 0.06, 0.16, 0.34, and 0.69, indicated little compatibility between the polymers at middle compositions. Dynamic and steady shear flow rheological measurements, using cone/plate geometry, showed the PMMA‐rich (6 wt % LCP) and LCP‐rich (69 wt % LCP) blends to be essentially homogeneous, and dominated by the properties of the major component. However, at 16 wt % and 34 wt %, the resulting phase separation led to lower dynamic moduli (than either LCP or PMMA separately), and increased shear thinning. This behavior supports the notion that the LCP acts as a lubricant by promoting the flow of the non‐LCP. The results reported in this article show that these rheological effects, which were previously observed in blends of insoluble, rigid LCPs and engineering thermoplastics, still exist with a much less rodlike LCP mixed with a commodity polymer.
Synthesis and photoconductivity study of phthalocyanine polymers. I. PAA–CuPc(NO2)2
Authors: Chen Hongzheng , Wang Mang , Feng Linxian , Shen Xuebin , Yang Shilin
Published: April 2003

Cu–dinitro–diamino phthalocyanine was synthesized and converted to the diazonium salt. Polyacrylamide bonded CuPc(NO2)2 [PAA–CuPc(NO2)2] (I) was synthesized by hot polymerization of acrylamide and this diazonium salt. Polymer(I) is water soluble and contains about 7 mol % CuPc(NO2)2 rings, which are covalently bonded to PAA. Polymer(I) shows good photoconductivity, which is much better than that of the corresponding phthalocyanine monomers. By doping with iodine (I2), the photosensitivity of polymer(I) is increased, which through fluorescence analysis is explained by the fact that a charge–transfer complex (CTC) of polymer(I) with I2 is formed. The influence of interface layer (IFL) and charge–transportation material (CTM) on the photoconductivity of polymer(I) were also studied.
Chemical modifications of insoluble polystyrene derivatives
Authors: Migonney V. , Lacroix M. D. , Douzon C. , Jozefowicz M.
Published: April 2003

The development of biospecific polymeric biomaterials requires new methods of chemical treatment that may be achieved whatever the involved polymeric surface without any degradation of the macromolecular structure. To check whether substitution of polymeric surfaces by epoxy groups could be a suitable way of synthesis to reach this goal, functionalization of polystyrene by epoxy groups was carried out. The respective reactions of carboxylic acids, alcohols, aldehydes, hydrochloric and sulfuric acid, and benzylamines have been extensively studied and suitable characterization has been performed on the respective polystyrene derivatives using infrared spectroscopy, elemental analysis, argentimetric titration, and acidimetric titration. In addition, a method of titration of the epoxy groups' content of insoluble functionalized polymers has been developed by the use of 14C‐labeled benzylamine.
Association phenomena between copolymers of p‐styrenesulfonate(Cs+)/3‐methacryloxypropyltrimethoxysilane and hydroxypropylcellulose in aqueous solution and solvent‐cast films
Authors: Schultz Gerald
Published: April 2003

Association between copolymers of p‐styrenesulfonate (Cs+)/3‐methacryloxypropyltrimethoxysilane [copolySS(Cs+)/MAPTMS], and hydroxypropylcellulose (HPC) are shown to exist in dilute aqueous solution. Gels form at concentrations as low as 0.05 g/dL. The tendency to form gels is a function of mol % MAPTMS in the copolymer and molecular weight of HPC. Gels can be dispersed by the addition of dimethylformamide (DMF), a known disruptor of hydrogen bonding. Homopolymers of SS(Cs+) and MAPTMS were also prepared. PolyMAPTMS shows anamolous behavior with regards to association with HPC in that gels form to a lesser degree than the trend exhibited by the copolymers. This is rationalized on the basis of the lack of chain expansion due to the absence of salt groups and their intrapolymer repulsions. In addition to the hydrodynamic data, the phase relationship of blends of HPC with either copolySS(Cs+)/MAPTMS, polySS(Cs+), or polyMAPTMS cast from aqueous solution strongly suggests specific interactions between polymers.
Thermal degradation of epoxy/silica composites monitored via dynamic mechanical thermal analysis
Authors: Unsworth J. , Li Y.
Published: April 2003

A dynamic mechanical thermal analyzer (DMTA) was used to monitor changes of dynamic mechanical properties during thermal degradation of two types of epoxy/silica composites, both of which are used as electrical insulation in power apparatus. It was found that the peak value of the dynamic loss factor (tan δ), glass transition temperature (Tg), and dynamic storage modulus (E′) above Tg changed considerably with increasing thermal degradation, while E′ at the glassy state only underwent a moderate change with increased thermal degradation. It is concluded that the DMTA technique is very sensitive to the structural changes in the investigated epoxy composites due to the thermal degradation. It is also confirmed by DMTA tests that further cross‐linking and loss of dangling chains are occurring slowly during the stage prior to the onset of the severe degradation. © 1992 John Wiley & Sons, Inc.
Effect of chemical cross‐linking under elongation on shape restoring of poly(vinyl alcohol) hydrogel
Authors: Hirai Toshihiro , Maruyama Hidetoshi , Suzuki Takashi , Hayashi Sadao
Published: April 2003

An anisotropically swollen hydrogel of poly(vinyl alcohol) (PVA) was found to be able to restore an isotropic physical shape by restoring isotropic physical cross‐links induced by anisotropically distributed chemical cross‐links. The anisotropic chemical cross‐links were introduced in the isotropic physical gel by cross‐linking with glutaraldehyde under elongation. The physical gel was made from the PVA aqueous solution by repetitive freezing and thawing. The chemically cross‐linked gel had kept its original shape and physical properties despite the chemical treatment under strain. However, by the heat treatment in boiling water, the gel changed its form anisotropically depending on the strain applied in the chemical treatment. The anisotropically swollen gel was deswollen in methanol and then reswollen in water. The reswollen gel took back its original isotropic shape, suggesting that the anisotropic chemical cross‐links thus introduced in the gel have a memory effect on the restoration of isotropic physical cross‐links. © 1992 John Wiley & Sons, Inc.
Reaction mechanisms of the metal chelates with epoxy oligomers and the structures of the epoxy—chelate metal‐containing matrixes
Authors: Kurnoskin A. V.
Published: April 2003

A theoretical generalization of the experimental results of the investigation of the properties of the metalliferous epoxy chelate polymers (MECP) based on diglycidyl ether of bisphenol‐A (DGEBA) has been carried out. Shown is the possibility of adjusting the structure and properties of MECP by changing the temperature of hardening and the content of a chelate hardener in an epoxy compound and by varying the composition of a chelate molecule, i.e., its structural fragments—a metal, ligand, and anion, which leads to changing the predominant mechanism of the reaction of the epoxy oligomer with the hardener, which can be catalytic or can proceed with the amino groups of a complex cation or unconnected ligand and with an anion. As a result, the epoxy chelate matrixes of different structures are formed. A correlation between the tensile strength (σt) and tensile modulus (Et), flexural strength (σf), and flexural modulus (Ef) of MECP—σt (Et) and σf = f(Ef)—has been established. The form of this correlation corroborates the presumption that the polymerization mechanism of the epoxy oligomer is changed and the various structures of the polymer matrixes are formed. © 1992 John Wiley & Sons, Inc.
Specialty polyurethane soft segments. III. Synthesis and characterization ofN‐isopropyl polyether polyamine oligomers containing backbone urea or amide moieties
Authors: Harris Robert F. , Habermann Clarence E.
Published: April 2003

Primary polyether polyamine oligomers containing preformed urea or amide moieties in their backbones were converted to the correspondingN‐isopropyl polyether polyamine oligomers (secondary amines) by reaction with acetone and hydrogen in the presence of a catalyst. The best results were from reactions carried out at about 150°C using a supported platinium or palladium catalyst in a fixed bed. Reactants and products were monitored by quantitative carbon‐13 NMR, size exclusion chromatography, and amine titration. Perchloric acid titration was used to quantify the number of urea moleties per molecule. Amide backbone materials gave very little backbone degradation. However, some backbone degradation was observed with urea backbone materials, leading to products with lower molecular weights. These polyether polyamine oligomers, containing urea or amide moieties in their backbones, are useful in urethane/urea polymer systems. The lower reactivity of these secondary amines (toward polyisocyanates) results in their utility in a broader range of polyurethane fabrication technologies. © 1992 John Wiley & Sons, Inc.
Chemically induced porogen decomposition in premembranes for porogen derived membranes
Authors: Eyal A. M. , Hajdu K. , Hazan B. , Edelstein D.
Published: April 2003

Studies of chemically induced porogen decomposition in Porogen Derived Membranes show that substantially complete decomposition of porogen molecules, molecularly dispersed in the polymeric matrix, is attainable. Several hours are required for decomposition by reagents penetrating into the premembrane at ambient. Decomposition rate is determined by characteristics of polymer, porogen, and reagent used, by polymer/porogen weight ratio, by reagent concentration, and by temperature. The concept of decomposition by an internal catalyst was also validated. In addition to direct relevance to the new method of membrane formation, the study provides better understanding of phenomena of general interest, such as transport of small molecules through changing polymeric matrices. © 1992 John Wiley & Sons, Inc.
Solvent effect on the curing of polyimide resins
Authors: Hsu Tzu‐Chien J. , Liu Zu‐Ling
Published: April 2003

The effect of the solvent 1‐methyl‐2‐pyrrolidinone (NMP) on the curing of polyimide resins synthesized from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA) has been investigated. Three polyimide precursors, i.e., the polyamic acid (PAA), with controlled amount of NMP were prepared. The study was aimed first to independently investigate the decomplexation process, which involved the evolution of hydrogen‐bonded NMP from PAA, without interference from imidization. This was accomplished by TGA at varying heating rates using different solvent content in PAA. The observed one‐stage decomplexation process suggested that the complex formation of NMP and PAA was not the same as the model compound studied by others. An average value of 150 kJ/mol for the activation energy of the decomplexation process was obtained. The study then sought to identify the effect of the decomplexation on the imidization kinetics by employing DSC at several drying temperatures and also varying heating rates. This allowed one to control the extent of plasticization that occurred to facilitate the imidization process. Our DSC data showed that over‐drying PAA resulted in prolonged imidization due mainly to the lack of plasticization by decomplexed NMP. The estimated enthalpy of imidization and that of decomplexation were 114 KJ/mol and 53 kJ/mol NMP, respectively. Finally, the imidization kinetics was independently investigated using FTIR, without the interference from decomplexation process. The results indicated that there were four stages during the entire imidization process. Up to a temperature of 150°C, less than 20% of amide groups had reacted to give imide groups and the reaction was slow. Most of the imidization took place between 150 and 180°C with conversion as high as 90%. The imidization process was completed after the temperature was further raised to 250°C. Above 250°C, the reverse reaction became more significant (due probably to configurational and packing preference) and resulted in a lowering of final conversion back to 80%. © 1992 John Wiley & Sons, Inc.
Toughening of graphite–epoxy composites with an electrocopolymerized high‐temperature thermoplastic interphase
Authors: Wimolkiatisak Angel S. , Bell James P.
Published: April 2003

Electrocopolymerization of a high‐temperature 3‐carboxyphenylmaleimide‐styrene interphase onto graphite fibers was carried out in an effort to toughen graphite—epoxy composites. The effects of the interphase and its thickness on the mechanical properties and the failure modes were investigated. The optimum interphase thickness was found to be about 0.16 μm. At this thickness, the average value of the DCB Mode I critical strain energy release rate is improved by about 100%, the average notched Izod impact resistance is improved by about 60%, and the average interlaminar shear strength is maintained at about the same value as the control composites. The failure mode was shifted toward more ductile failure with the inclusion of an interphase. © 1992 John Wiley & Sons, Inc.
Structure of heat‐treated nylon 6 fibers. II. Structural stability and dye leveling
Authors: Simal Abigail Lisbão , De Godoy Oriani Luis Alberto
Published: April 2003

Nylon 6 fibers were submitted to three types of heat treatments at different temperatures and times in order to find the best conditions to achieve structural stability. The boiling water treatment proved to be more effective in promoting profound structural modifications than the other treatments (dry treatment and the dry treatment followed by a 5‐h boiling water heat setting). Also, the fibers reached their maximum structural transformations after 1 h of treatment. Thus, a 5‐h boiling water treatment was chosen to heat‐set the fibers. Then, the heat‐set fibers were submitted to dyeing and migration experiments with different disperse dyes. The obtained results demonstrate that the discontinuities observed in the curves of migration factor versus square root of time might be related to the mechanism of the migration experiments. The different solubilities of the disperse dyes in water helped the understanding of this mechanism. Also, this study with nylon 6 fibers reveal that the proposed model can be used for leveling time prediction, and the discontinuities mentioned above can for practical purposes be neglected. © 1992 John Wiley & Sons, Inc.