bluuebunny/crossref_metadata_2025 huggingface dataset:
Self‐curing epoxy compounds
Authors: Mikroyannidis John A.
Published: April 2003

A new series including eight structurally different self‐curing epoxy compounds bearing azomethine linkages were synthesized, characterized and polymerized. 4‐(2,3‐Epoxypropoxy)‐benzaldehyde (EPB) or 2,3‐epoxypropyl glyoxylate monohydrate (EPG), prepared by reacting 4‐hydroxybenzaldehyde or glyoxylic acid monohydrate, respectively, with excess of epichlorohydrin in the presence of benzyltrimethylammonium bromide as catalyst, were used as starting materials. EPB or EPG reacted with an equimolar amount of a substituted aromatic amine (4‐aminobenzoic acid, 5‐aminoisophthalic acid, 4‐aminophenol, or 1,4‐phenylene‐diamine) to afford the epoxy compounds. They were characterized by IR and 1H‐NMR spectroscopy. Their thermal polymerization was investigated by DTA. The thermal stabilities of cured resins were evaluated by dynamic TGA and isothermal gravimetric analysis (IGA). The polymers of the epoxy compounds derived from EPB were stable up to 225–298°C in N2 and afforded anaerobic char yield of 57–62% at 800°C.
Viscosity of aqueous solutions of polysaccharides and their carboxylate derivatives
Authors: Nomura Hiroyasu , Koda Shinobu , Hattori Futoshi
Published: April 2003

The viscosities of aqueous solutions of methyl cellulose, dextran, and their carboxymethyl derivatives were measured as functions of molecular weight and concentration. Furthermore, effects of ionic group and added salt on the viscosity of aqueous solutions of carboxymethyl derivatives were investigated. The viscosities of dextran and carboxymethyl dextran solutions did not show any shear stress dependence, but those of methyl and carboxymethyl cellulose solutions strongly depended on shear stress even at low concentrations. The results were discussed on the basis of the points of molecular structure and hydration and ionic interaction of a polymer chain in solutions.
Physicochemical changes in stabilized, orientated polypropylene films during the initial stages of thermal oxidation
Authors: Horrocks A. Richard , D'souza Jennifer A.
Published: April 2003

Orientated, stabilized, isotactic polypropylene films have been oven‐aged at 130°C for times shorter than required for their embrittlement. The structural changes occurring during this induction period have been studied using tensile tensiometric, density, thermal analytical (DTA and TGA), and infrared spectrophotometric techniques. After an initially rapid annealing, films show similar time‐dependent changes in tensile, density‐derived crystalline and thermogravimetric behaviors. Comparison with vacuum‐aged sample properties shows that these changes reflect the effects of oxidative attack of polypropylene chains. Infrared examination shows that, even after the longest aging times studied and close to the induction period for embrittlement, the presence of oxidized chain groups is only just discernible. Oven aging reduces post‐fusion oxidative onset and maximum mass loss temperatures determined by TGA. Kinetic analysis demonstrates that the apparent activation energies and Arrhenius factors are reduced during aging as the post‐fusion oxidation mechanism becomes more complex. The results suggest that, during the induction period, changes in both physical and chemical structural features of orientated polypropylene occur which have possible importance in determining the lifetime of the polymer in use.
Polystyrene/Polycarbonate/Polystyrene‐block‐Polycaprolactone blends. Emulsification and mechanical performance
Authors: McKay Ian D.
Published: April 2003

Two polystyrene–polycaprolactone diblock copolymers, of differing molecular weights, have been extrusion‐blended with polystyrene and polycarbonate. The morphologies of the resultant blends were studied using differential scanning calorimetry and scanning electron microscopy. In all compositions studied, the polystyrene and polycarbonate phases exhibited discrete glass transitions indicative of the immiscibility of these components. However, addition of the copolymer increased the extent of dispersion of the homopolymer components within one another quite effectively. Blend specimens were tested with respect to tensile, flexural, impact, thermal, and flow characteristics to probe the effects of morphology and composition on these factors. In general, the blends were rigid, brittle materials with thermal characteristics in the range between those of the polystyrene and polycarbonate components. Addition of polystyrene‐block‐polycaprolactone polymer to the blends resulted in increased brittleness, reduced thermal performance, maintenance of rigidity, and improved flow.
Studies on the synthesis of a methacrylate‐based dental restorative resin
Authors: Sheela M. S. , Selvy K. Tamare , Krishnan V. Kalliyana , Pal S. N.
Published: April 2003

The synthesis of bisphenol A–glycidyl methacrylate (BIS–GMA), the resin component in most dental composite restorative materials, catalyzed by different tertiary amine accelerators such as N,N′‐dimethyl‐p‐toluidine (DMPT), N,N′‐dimethylamino phenethyl alcohol (DMAPEA), and N,N′‐dimethylamino ethyl methacrylate (DMAEMA) is reported in this work. The effect of varying concentrations of accelerators and the reaction conditions of the synthesis as a function of time is studied in detail. The kinetics of the reaction between epoxide and carboxyl group during the formation of BIS–GMA is monitored using infrared (IR) and chemical techniques. The reaction is found to follow first‐order and zero‐order kinetics with respect to epoxide and acid, respectively. The degree of epoxide and acid conversion has been calculated as a function of time. The percentages of various isomers, formed under different reaction conditions have been reported. Characterization procedures for BIS–GMA have been developed.
Rubber‐modified epoxies. II. Influence of the cure schedule and rubber concentration on the generated morphology
Authors: Verchere D. , Pascault J. P. , Sautereau H. , Moschiar S. M. , Riccardi C. C. , Williams R. J. J.
Published: April 2003

The morphology of a system consisting of a bisphenol A diglycidylether (DGEBA) based epoxy, cured with a cycloaliphatic diamine (4,4′‐diamino‐3,3′‐dimethyldicyclohexylmethane, 3DCM), in the presence of an epoxy‐terminated butadience‐acrylonitrile random copolymer (ETBN), was studied as a function of the cure schedule and the initial rubber concentration. Scanning (SEM) and transmission (TEM) electron microscopy, differential scanning calorimetry (DSC) and dynamic mechanical analysis were used to characterize the generated morphology. SEM results were not affected by the type of mechanical test and strain rate. Trends observed for the particle size distribution, the volume fraction of dispersed phase, the concentration of dispersed phase particles and the composition of both phases as a function of polymerization temperature and rubber concentration, were discussed. A correlation between the viscosity at the cloud point and the average size of dispersed phase particles was found for different systems, independently of the cure temperature and the initial rubber amount.
Rubber‐modified epoxies. III. Analysis of experimental trends through a phase separation model
Authors: Moschiar S. M. , Riccardi C. C. , Williams R. J. J. , Verchere D. , Sautereau H. , Pascault J. P.
Published: April 2003

A phase separation model was used to simulate the morphologies obtained in a system consisting of a diepoxide based on bisphenol‐A diglycidylether cured with a cycloaliphatic diamine, in the presence of an epoxy‐terminated butadiene‐acrylonitrile random copolymer (ETBN). A detailed analysis of experimental factors affecting resulting morphologies was previously reported. The model, based on a thermodynamic description through a Flory–Huggins equation, and constitutive equations for polymerization and phase separation rates, could explain most of the observed trends. A nucleation‐growth mechanism was believed to take place because of the very low values of interfacial tensions for this type of systems. Conditions which would lead to spinodal demixing are also discussed.
Tetrahydropyranyl‐ and furanyl‐protected polyhydroxystyrene in chemical amplification systems
Authors: Hesp Simon A. M. , Hayashi Nobuaki , Ueno Takumi
Published: April 2003

Tetrahydropyranyl‐ (THP) and furanyl‐ (THF) protected polyhydroxystyrene (PHS) polymers have been investigated for their potential use in conjunction with onium salt acid precursors to yield high‐sensitivity resist systems. The synthesized polymers have high transmittance at 248 nm (the wavelength used in next‐generation excimer laser, KrF exposure tools). At 248 nm the transmittance for a 1‐μm thick film is ∼ 80% (Abs = 0.097 μm−1). The acid sensitivity of the acetal functionality at room temperature is high, requiring careful handling of all materials to prevent any premature deprotection of the hydroxy group. The highest lithographic sensitivities obtained so far with a system consisting of poly(p‐tetrahydropyranyl‐oxy‐styrene) base resin and 1 mol % of bis (p‐tert‐butyl phenyl) iodinium triflate (TBIT) was ∼ 2 mJ / cm2. High‐resolution line and space patterns (0.35 μm) were obtained with a system comprising PHS‐p‐THP and an acid precursor, using an excimer laser step and repeat exposure at 248 nm.
Melt spinning of shear modified plasticized polystyrene
Authors: Qian J. W. , Rudin Alfred
Published: April 2003

Polystyrene is not normally shear‐modifiable. Addition of small amounts of plasticizer (butyl benzyl phthalate) result in changes in melt viscosity and elasticity during extrusion. Fiber spinning experiments are shown to provide useful indications of the rheological state of polymers that are sensitive to shear history. Here, the density, modulus and work to rupture of lightly plasticized polystyrene is shown to vary with extrusion history of the material.
Role of itaconic acid in latex particle nucleation
Authors: Lock Michele R. , El‐Aasser Mohamed S. , Klein Andrew , Vanderhoff John W.
Published: April 2003

Itaconic acid, a carboxylated water‐soluble monomer, was examined in terms of its role in latex particle nucleation when copolymerized with acrylate monomers. From emulsion polymerizations in which the particle number concentrations were followed as a function of monomer conversion, it was found that the greater the amount of itaconic acid present, the larger the final latex particle diameter. This was interpreted as the result of the lower number of primary particles being initially nucleated. The above observations can be explained by the incorporation of the hydrophilic itaconic acid into acrylate oligomeric radicals that initially form. This incorporation increases the water‐solubility of the radicals such that a lower proportion of these radicals is likely to precipitate to form primary particles.
Fracture and structure of highly crosslinked polymer composites
Authors: Cook Wayne D.
Published: April 2003

The fracture toughness of silica filled dimethacrylate resins has been found to increase with the degree of cure of the network, and was previously attributed to increased crosslinking or the concomitant reduction in unreacted monomer (sol species). Studies of the dependence of the polymerization on the photoinitiator concentration and cure time of dimethacrylate resins illustrate the interrelation of the wt % sol and the degree of cure and reveal that a considerable amount of residual monomer remains in undercured networks, as predicted by simple gelation theory. In an attempt at separating the effects of residual monomer and crosslinking on the fracture behavior, several series of filled dimethacrylate and epoxy resins were studied in which the crosslink density and sol levels were independently varied without introducing significant changes in the chemical composition of the network. Although the fracture energy and toughness were raised by increasing the crosslink density in the epoxy resins, no significant variation was found for the dimethacrylates. Saturated analogues of dimethacrylates (used to represent residual monomer) significantly impaired the fracture resistance, suggesting that the reduction in residual monomer is responsible for the improved fracture toughness observed with postcured dimethacrylate networks.
Preparation and characterization of polyelectrolyte copolymers containing methyl methacrylate and 2‐hydroxyethyl methacrylate. I. Polymers based on methacrylic acid
Authors: Wen Shao , Yin Xiaonan , Stevenson William T. K.
Published: April 2003

Acidic polyelectrolyte copolymers containing 2‐hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and methacrylic acid (MAA) were prepared by free radical polymerization to high conversion in solution. Copolymer yields were obtained by gravimetry (all in the 30–50% range), relative molecular weights estimated by intrinsic viscosity measurements (all in the 50–70 cc/g range), tacticity by 13C nuclear magnetic resonance (NMR) spectroscopy (all polymers predominantly syndiotactic with some atactic content), and composition by acid/base titrations in conjunction with 1H‐NMR spectroscopy (all close to the monomer charge ratios). Acid strengths or apparent pKa's were examined as a function of extent of ionization. Measurements performed in water indicated that the compact/extended coil transformation in predominantly syndiotactic polymethacrylic acid occurs also in copolymers of similar tacticity containing moderate to high concentrations of MAA. The apparent pKa of such polymers containing only small amounts of MAA did not vary with extent of ionization, indicating a low degree of interaction between the acid groups. In copolymer pairs containing similar amounts of MAA but differing HEMA and MMA contents, the polymer containing more HEMA appeared the stronger acid, presumably due to a better solvation of that polymer which would increase the net spatial charge–charge separation and decrease cooperative effects that lead to suppressed ionization.
Mooney scorch time of epoxidized natural rubber
Authors: Poh B. T. , Tan B. K.
Published: April 2003

The scorch property of accelerated sulfur vulcanization of three grades of expoxidized natural rubber (viz. ENR 10, ENR 25, and ENR 50) was studied by using Mooney Shearing Disk Viscometer in the temperature range of 100–180°C. Effects of accelerator types, concentration of accelerator, and carbon black on ENR 10 were also determined. Results obtained indicate a similar scorch behavior as that reported earlier for SMR L. However, some differences in the magnitude of scorch times in the temperature and concentration studies are observed between ENR and SMR L. These differences are attributed to the activation of a double bond by the adjacent epoxide group in ENR, the effect being more significant for a higher degree of epoxidation of natural rubber. In the case of ENR 50, differential scanning calorimetry measurement suggests that additional crosslink occurs via a ring‐opening reaction at about 155°C. Based on first‐order reaction kinetics, the apparent activation energy of vulcanization for the rubbers studied is estimated and discussed.
A simulation of the enthalpies of fusion of unplasticized poly(vinyl chloride)
Authors: Obande O. P.
Published: April 2003

Enthalpies of fusion were measured by differential scanning calorimetry for PVC compounds processed within the range 150°–220°C by twin‐screw extrusion or compression molding. It was observed that the effects of polymer molar mass (K‐value) or sample formulation on values of the experimental enthalpy change follow identical pattern as effects of the same parameter on elastic response established by rheometry. It was assumed that the “amorphous” phase is made up of a matrix of locally ordered chain segments and occluded free‐volume and that this matrix constitutes what is described as “secondary crystallinity” of bulk PVC. On the basis of this assumption, a model was developed incorporating a parameter for the contribution of enthalphy of relaxation of free volume to the observed enthalpy of fusion of the secondary crystallinity. Graphical comparison of the simulated enthalpy changes with the measured values produced accurate measures of the critical temperature where a change in melt flow activation energy has been established by rheometry. The comparison further predicts that if PVC was processed below 190°C, an increase in shear intensity should reduce the free‐volume content of the product, while processing above 200°C should result in the converse. Also, with increasing processing temperature above 200°C a shear‐independent linear decrease in free‐volume of the bulk product is suggested to be operative. Thus, the material produced by extrusion or compression molding between 190 and 200°C should be least dense and least crystalline in line with previous observations.
Performance of treated hybrid fiber reinforced‐thermoplastic composites under extreme conditions. IV. Use of glass fiber and sawdust as hybrid fiber
Authors: Maldas D. , Kokta B. V.
Published: April 2003

The mechanical properties and dimensional stability of hardwood aspen in the form of sawdust and surface‐treated glass fiber‐polystyrene composites were evaluated under various extreme conditions, e.g., variation in the testing temperature (from +25° to −20°C), exposure to boiling water and heat in an oven at +105°C. The compatibility of wood fiber with glass fiber and with polystyrene improved by precoating the wood fiber with a coupling agent, e.g., 8% isocyanate, 4% silane and polymer. The mechanical properties of the composites, in particular, treated sawdust/glass fiber‐filled composites, increased under extreme conditions in comparison with those filled with nontreated sawdust/glass fiber. Under the same conditions, dimensional stability also supports this observation.
Structural and electrical behavior of polyacrylonitrile‐polypyrrole composite film
Authors: Bhat N. V. , Sundaresan E.
Published: April 2003

Polyacrylonitrile‐polypyrrole composite films were prepared by a vapor phase technique. The films obtained by this method have high conductivity and good mechanical properties. Growth of polypyrrole on the surface of polyacrylonitrile was investigated by electron microscopic studies. Electrical properties of composite films were investigated as a function of FeCl3 content as well as polypyrrole uptake. The current‐voltage characteristic suggest an ohmic conduction. The conductivity of these composite films was measured as a function of temperature yielding an activation energy of 0.16 eV.
Blends of polyurethane carboxylates with styrene vinylpyridinium copolymers
Authors: Rutkowska Maria , Eisenberg Adi
Published: April 2003

This is a continuation of an ongoing investigation of miscibility enhancement via ionic interactions in urethane‐styrene blends. The present study deals with a polyurethane which contains in the hard segments pendant carboxylate groups neutralized by ammonium ions while the polystyrene contains pendant vinyl pyridinium methyl iodide groups. Miscibility of the styrene is seen with the hard segments of the urethane because of ion pair/ion pair interactions. Methanol extraction raises the Tg because it eliminates low molecular weight components, without removing the microions.
Properties of PET fibers with high modulus and low shrinkage (HMLS). I. Yarn properties and morphology
Authors: Rim P. B. , Nelson C. J.
Published: April 2003

Classical morphological analysis has been performed on novel PET fibers of high modulus and low shrinkage (HMLS). As expected, amorphous orientation controls the degree of shrinkage and tenacity. The uniqueness of these materials is derived from a high “effective” crosslink density which results in a high retractive force during elevated temperature shrinkage and significant stress‐amplification during room temperature extension. Although the morphological origin of the high effective crosslink density is unknown, it is speculated that the interfibrillar regions contribute to the observed behavior by suppressing yielding.
Stress relaxation behavior of short kevlar fiber‐reinforced thermoplastic polyurethane
Authors: Kutty Suni L. K. N. , Nando Golo K. B.
Published: April 2003

Stress relaxation behavior of short Kevlar fiber‐reinforced thermoplastic polyurethane (TPU) is studied with respect to strain level, strain rate, fiber loading, and fiber orientation and temperature. The existence of a two‐step relaxation mechanism for unfilled stock and a three‐stage relaxation mechanism for the fiber‐filled stock is reported.
Evaluation of DGEBA
Authors: Tamareselvy K. , Sheela M. S. , Kalliyanakrishnan V. , Pal S. N.
Published: April 2003

Analytical studies using chemical, spectral, and chromatographic methods have been carried out for four commercial diglycidyl ether of bisphenol A (DGEBA) resins (AER, EER, DER, and NER) in order to evaluate the essential parameters of DGEBA for synthesizing 2,2‐bis [4‐ (2‐hydroxy‐3‐methacryloyloxypropoxy)] phenyl propane (BIS‐GMA), an impportant precursor for dental composites. Parameters such as epoxy equivalent weight, hydroxyl value, and hydrolyzable chlorine content have been estimated. The role of these parameters in determining the final purity of BIS‐GMA has also been discussed.
On oxygen plasma‐treated polypropylene interfaces with air, water, and epoxy resins. II. Epoxy resins
Authors: Occhiello E. , Morra M. , Morini G. , Garbassi F. , Johnson D.
Published: April 2003

XPS, SEM, SSIMS, FTIR‐ATR, water‐in‐air, and air‐in‐water contact angle measurements have been used to unambiguously characterize the locus of failure of PP/epoxy joints. In the case of untreated PP, the fracture has been found adhesive, whereas in oxygen plasmatreated PP, it is cohesive, within bulk PP, but close to the modified PP‐bulk PP interface. The smoothness of fracture surfaces allowed us to exclude mechanical interlocking effects. Shear‐strength measurements showed that the mechanical strength of the joint was improved by plasma treatment. Preliminary thermal equilibration of the plasma‐treated PP sample and changes in the curing cycle of the epoxy resin did not change either the locus of failure or the shear strength of the joint. The reason is probably because the number of polar functions left at the surface after thermal equilibration is sufficient to induce adhesion. The mechanical strength of the PP surface layer may be the determining factor. Fracture energy calculations showed that the observed locus of failure is the same as predicted on the basis of surface energy considerations.
Hydrolytic degradation of nonoriented poly(β‐propiolactone)
Authors: Mathisen Torbjörn , Lewis Monica , Albertsson Ann‐Christine
Published: April 2003

The hydrolytic degradation of poly(β‐propiolactone) with a molecular weight Mw of 32,000 has been studied in a buffered salt solution (pH 7.2) at 37°C. Within 42 days, the embrittlement of the samples made tensile strength measurement impossible, which is due to the rapid reduction of molecular weight, 50% reduction after 49 days. The maximum weight due to water absorption was measured to 1.2 wt %, reached after 2 days. The absorbed water acts as a plasticizer in poly(β‐propiolactone) observed by the displacement in the maxima of the tan δα peak. A fast increase of crystallinity in the samples has been observed during the first 50 days of degradation, with the increase continued up until 190 days, after which a decline of the crystallinity can be observed, indicating hydrolityc degradation of the crystalline part of the samples. The mass loss of the samples becomes prominent after 150 days of immersion and reached a value of 14.6% after 260 days.
Studies on modification of some flammability characteristics by plasma. II. Polyester fabric
Authors: Akovali G. , Takrouri F.
Published: April 2003

Cold plasma treatment of polyester fabric in the presence of several volatile monomers containing expected flame retardant elements was made and some of the flammability characteristics of the plasma/monomer‐treated fabric were studied. The plasma treatment on the fabric caused a slight decrease in both oxygen index values and burning rates. It is believed that crosslinking outweighs the effect of grafted elements. The results of wettability and TGA tests as well as SEM data are included.
Self‐vulcanizable rubber blend systems based on epoxidized natural rubber and chlorosulfonated polyethylene: Effect of blend composition, epoxy content of epoxidized natural rubber, and reinforcing black filler on physical properties
Authors: Mukhopadhyay Sujata , De S. K.
Published: April 2003

Mill mixed blend of epoxidized natural rubber and chlorosulfonated polyethylene forms a self‐vulcanizable rubber blend during molding at high temperatures in absence of any vulcanizing agent, which is confirmed by FTIR studies. The extent of vulcanization reaction not only depends upon time and temperature of molding but also on the level of epoxidation in ENR and its proportion present in the blend. Physical properties of the blends are comparable to that of conventional rubber vulcanizates. Such blends can be reinforced by carbon black filler.
Prediction of monomer compositions in terpolymerization
Authors: Padwa A. R. , Schwier C. E.
Published: April 2003

An efficient algorithm has been developed allowing iterative solution of the Alfrey–Goldfinger equation. The algorithm is shown to result in rapid convergence for terpolymerization calculations and can be extended to polymerizations with more than three monomers.
Butadiene polymerization with nickel compounds: Effect of cocatalysts
Authors: Throckmorton M. C.
Published: April 2003

The preparation of a high cis‐1,4‐polybutadiene, using a novel ternary catalyst system composed of triethylaluminum, a soluble nickel compound, and boron trifluoride diethyl etherate has been reported in the literature. The present paper reports the polymerization results obtained when the triethylaluminum was replaced with other alkylaluminums and the BF3 · Et2O was replaced with other BF3 complexes or HF · Et2O. When utilizing BF3 · Et2O, both the polymerization rate and the polymer DSV decreased significantly as the length of the alkyl group in the alkylaluminum increased from C1 to C6. However, the length and nature of the alkyl group had virtually no effect when utilizing BF3 · phenolate (BF3 · 2C6H5OH) and only a small effect with HF · Et2O; although the length of the alkyl group had no significant effect when using BF3 complexes of aromatic aldehydes, the branched alkyl groups gave greater polymerization rates than did the corresponding n‐alkyls. In summary, the strongly acidic complexes, BF3 · phenolate and HF · etherate, promoted rapid polymerization when employed with any of the alkylaluminums. However, with other BF3 complexes, the alkylaluminum selected had an important influence upon either the conversion and/or the polymer DSV.
Structural changes on plasma irradiation of ethyl–cyanethyl cellulose as revealed by infrared spectroscopic technique
Authors: Zhao Qiang , Long Fujin , Liu Xushu
Published: April 2003

Ethyl–cyanethyl cellulose was treated with oxygen plasma using the RF glow discharge technique. Three different plasma‐treated samples, including gel fraction, soluble fraction, and newly polymerized product by small moleculars given off by ethyl–cyanethyl cellulose, were obtained. With the infrared spectroscopic technique, the structural differences caused by plasma were studied. The effect of different gas plasma N2, Ar, and O2 on the structure of ethyl–cyanethyl cellulose was also studied.
Crosslinked latex blends based on gelatin: Synthesis, morphology, thermal, and mechanical properties
Authors: Ramaraj B. , Rajalingam P. , Radhakrishnan Ganga
Published: April 2003

Latex blends of different compositions of poly(methyl methacrylate‐co‐n‐butylacrylate) and gelatin have been synthesised in latex form with crosslinking agents. These latex blends were characterized by thermal and mechanical properties. The morphology of cross‐linked latex blends were studied by scanning electron microscopy (SEM).
Hydrophobic polymer films plasma‐polymerized from CF4/hydrocarbon and hexafluroacetone/hydrocarbon mixtures
Authors: Inagaki N. , Tasaka S. , Mori K.
Published: April 2003

Polymer films were deposited from the plasma polymerization of the mixtures of hydrocarbons, ethane, ethylene, and acetylene, and tetrafluoromethane (CF4) or hexafluoroacetone (HFA). The surface properties, the advancing contact angle of water, and surface energy of the films deposited and the chemical composition at the outermost layer of the films are discussed from the data of the angular XPS measurements. The plasma polymers deposited from the CF4/hydrocarbon and HFA/hydrocarbon mixtures contained fluorine atoms whose content depended on the CF4 or HFA concentration of the mixtures. The hydrophobicity of the films deposited could not be determined by the fluorine content of the films but by the chemical composition of the fluorine moieties at the outermost layer of the films. The CF3 moieties rather than the CF2 and CF moieties contribute largely to the hydrophobicity of the films. The plasma polymer films deposited from the HFA/acetylene (87.5 mol % HFA) showed higher hydrophobicity (the surface energy is 9.7 mJ/m2) than those from the CF4/acetylene mixture (87.5 mol % CF4) (the surface energy is 13 mJ/m2).
Epoxy–imide resins based on bis (carboxyphthalimide)s
Authors: Adhinarayanan K. , Packirisamy S. , George Reena S. , Rao V. Lakshmana , Ramaswamy R.
Published: April 2003

Epoxy–imide resins have been obtained through the reaction of Araldite GY 250 (diglycidylether of bisphenol‐A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac‐epoxy resin; polyfunctional) with bis(carboxyphthalimide)s derived from 4,4′‐diaminodiphenylsulfone, 3,3′‐diaminodiphenylsulfone, 4,4′‐diaminodiphenylmethane and 4,4′‐diaminodiphenylmethane and trimellitic anhydride. For each epoxy‐imide resin system, epoxy equivalent to carboxy equivalent ratio has been optimised to obtain the maximum tensile lap shear adhesive strength on stainless steel substrates at room temperature. The lap shear strength at 100, 150, and 175°C has been determined for the optimum ratio. Araldite EPN‐1138‐based systems give the lap shear strength of 141–182 kg/cm2 at room temperature for the optimum compositions and retain about 84–100% of the lap shear strength at 150°C. Araldite GY‐250‐based systems have lap shear strength of 183–193 kg/cm2 and retain 76–84% of the lap shear strength at 150°C except for the one cured with bis (carboxyphthalimide) prepared from 4,4′‐diaminodiphenylmethane, which retains only 17% of the lap shear strength. Among the systems studied, Araldite GY 250 cured with bis (carboxyphalimide) synthesized from 3,3′‐diaminodiphenylsulfone appears to be the best, retaining 75% (138 kg/cm2) of the lap shear strength at 175°C.
Plasma polymer deposition from indium acetylacetonate and its application to chemical sensor devices
Authors: Inagaki N. , Ohkubo J.
Published: April 2003

Plasma polymerization of indium acetylacetonate (InAcAc) was investigated from the viewpoint of the material preparation for application to chemical sensor devices. The plasma polymerization of InAcAc resulted in the deposition of films, which were hydrocarbon‐like polymers with fine particles of indium oxides. The deposition rate and the chemical composition of the deposited films were strongly influenced by the system pressure in operating the plasma polymerization, as well as by the substrate temperature. The deposited films possessed n‐type semiconductive properties and responded to reducing gases, such as CO, H2, C3H8, and C2H5OH, with increasing the conductivity. The sensor device composed of the films deposited from InAcAc showed extremely high sensitivity to CO and higher gas selectivity than the sensor devices consisting of SnO2 and ZnO2.
Miniemulsion polymerization—a comparative study of preparative variables
Authors: Tang P. L. , Sudol E. D. , Silebi C. A. , El‐Aasser M. S.
Published: April 2003

Variations in the conditions used to prepare miniemulsions of monomers in water have resulted in substantial differences in polymerization kinetics and final particle sizes and distributions. These variations have included (1) surfactant amount and type; (2) cosurfactant amount and type; (3) monomer (s) type; (4) temperature of preparation and polymerization; (5) means and conditions of homogenization; and (6) degree of aging of the emulsion. In an effort to unify some of the disparate information of previous work, a systematic study of some of the above variables was undertaken using styrene as the oil phase with sodium lauryl sulfate as surfactant. Based on the polymerization kinetics and particle sizes obtained, the following conclusions are drawn: The finest droplet size miniemulsions are obtained by (1) using a cosurfactant; (2) homogenizing at elevated temperature; (3) homogenizing using a uniform high shear device (Microfluidizer); and (4) limiting the aging time prior to polymerization.
Separation of organic vapor from air by aromatic polyimide membranes
Authors: Feng Xianshe , Sourirajan S. , Tezel H. , Matsuura T.
Published: April 2003

An attempt was made to prepare dry asymmetric membranes of aromatic polyimide material for the separation of air–organic vapor mixtures. Membrances with the permeability of organic vapor two orders of magnitude higher than that of air could be obtained. The membrane performance depends strongly on the conditions of membrane preparation. It was found that the permeability of organic vapors exhibits a strong correlation with their cohesive energy data.
Graft copolymerization of methyl methacrylate onto polypropylene oxidized with ozone
Authors: Yamauchi Jun , Yamaoka Akiyoshi , Ikemoto Kunji , Matsui Tetsuji
Published: April 2003

After the reaction of polypropylene by ozone oxidation, methyl methacrylate was graftcopolymerized onto the polypropylene. The active species determined by ESR spectroscopy as a peroxyl radical was converted to hydroperoxide, and the hydroperoxide was broken by heating, giving alkoxyl and hydroxyl radicals, the former of which initiated graft copolymerization. The effect of the ozone‐oxidation time and polymerization time on the graft copolymerization was investigated. At the constant polymerization time, the total conversion and the degree of the grafting increased with the ozone‐oxidation time, while the graft efficiency decreased. On the other hand, at the constant oxidation time, the total conversion and the degree of grafting increased with the polymerization time, while the graft efficiency decreased. These results were compared with a polyethylene case. The mechanism of the ozone oxidation and the initiation of the graft copolymerization were also discussed.
Polymerization of olefins through heterogeneous catalysis. IX. Experimental study of propylene polymerization over a high activity MgCl2‐supported Ti catalyst
Authors: Hutchinson R. A. , Ray W. H.
Published: April 2003

Results from an experimental study of propylene polymerization in heptane diluent over a high activity Mg‐supported Ti catalyst are presented. The study provides an examination of the effect of operating conditions on polymerization rate, product melt index, and powder bulk density. Among the findings are that product bulk density decreases with increasing operating temperature and decreasing operating pressure while prepolymerization increases the bulk density. The results support the hypothesis that polymer morphology is closely linked to mass transfer limitations within the growing polymer particle during the early stages of polymerization.
A quantitative adhesion test for thin polymer films on silicon substrates
Authors: Goldberg H. D. , Cha G. S. , Brown R. B.
Published: April 2003

The standard 90° peel test was modified in order to apply it to testing adhesion of thin polymer films to surfaces of silicon substrates, such as the silicon nitride passivation layer used in our solid‐state chemical sensors. The goal of this task was to develop a procedure for testing adhesion of both dry and wet films, which would yield repeatable, quantitative results quickly, and with simple sample preparation. It is important to produce valid comparisons of adhesion both over variations of a given polymer composition, and between films made of dissimilar polymer matrices. The method described herein could be applied to adhesion testing of a wide variety of thin polymer layers to solid surfaces.
Competitive adsorption of water‐soluble polymers on attapulgite clay
Authors: Chang S. H. , Ryan M. E. , Gupta R. K.
Published: April 2003

The individual, competitive, and displacement adsorption of polyvinyl alcohol (PVOH), hydroxyethyl cellulose (HEC), and hydroxypropylmethyl cellulose (HPMC) in aqueous solution onto an attapulgite clay has been systematically studied. For the individual adsorption experiments, the amount of polymer adsorbed at equilibrium decreased in the order PVOH, HEC, HPMC. In the competitive adsorption experiments, the adsorption level of each polymer is diminished by the presence of a competing polymeric species. Binary mixtures of a cellulosic polymer (HEC or HPMC) with PVOH result in a substantial reduction in the amount of cellulosic polymer adsorbed. In the displacement adsorption studies, the sequential addition of HEC or HPMC is not able to displace previously adsorbed PVOH molecules to any appreciable extent. However, the addition of PVOH to previously equilibrated HEC/clay or HPMC/clay suspensions results in a large amount of the adsorbed cellulosic polymer being displaced by PVOH, especially under conditions of high surface coverage. These results indicate that PVOH is preferentially adsorbed on the clay surface and the strength of attachment to the surface is greater for PVOH than for either cellulosic polymer.
Preparation and electrostatic properties of antistatic acrylics
Authors: Park Yun Heum , Kim Yong Kweon , Nam Sung Woo
Published: April 2003

Very good antistatic acrylic films or fabrics can be prepared by exposing the acrylic samples containing oxidizing agent to aniline vapor. The conductivity, the maximum static charge, and the half‐life time are used for estimation of electrostatic properties. The effects of the content of polyaniline and the temperature and time of exposure to aniline vapor on the electrostatic properties have been investigated. The stability of conductivity to ambient air exposure and the temperature dependence of conductivity for antistatic acrylic films have also been investigated.
Reinforcing effect of a magnesium silicate treated with a 4‐amino methyl pyridine in epichlorhydrin rubber (ECO) vulcanizates
Authors: González Luis , Rodríguez Andrés , Ibarra Luis
Published: April 2003

This paper reports on the chemical surface changes of sepiolite, a natural magnesium silicate, caused by adsorption of 4‐amino methyl pyridine, and the application of this product as a reinforcing filler in epichlorhydrin rubbers. The amine group of the reagent used in the surface modification of the mineral reacts with elastomer upon vulcanization. This gives rise to stronger rubber‐filler bonds with the consequential improvement of the technological properties of the vulcanizates.
Physical studies of ionically‐terminated polytetrahydrofuran polymers. I. Dilute solution behavior
Authors: Ali S. A. M. , Hourston D. J.
Published: April 2003

A series of tetrahydrofuran polymers, terminating at one end with a pyridinium bromide group, were prepared; their hydrodynamic behavior contrasted with the equivalent methoxyterminated polytetrahydrofurans. This article reports viscometry studies of these polytetrahydrofurans in cyclohexane, toluene, tetrahydrofuran, methyl ethyl ketone, and cyclohexanone.
Effects of modified air quenches on the high‐speed melt spinning process
Authors: Hotter J. F. , Cuculo J. A. , Tucker P. A.
Published: April 2003

A high molecular weight polyethylene terephthalate was spun into fibers in the speed range from 3,000–7,000 mpm. The effect of modifying threadline dynamics through a combination of enhanced and/or retarding air quenches on the resulting spinning performance, fiber structure, and mechanical properties was examined. Particular combinations of these threadline temperature profile modifications were shown to result in significant improvements in spinning performance and as‐spun fiber structure. Extensive characterization of select fiber samples revealed higher orientation and crystallinity, larger crystal dimensions, and greater mechanical properties. These results also demonstrated the ability to provide continued improvement in fiber properties at very high take‐up speeds where typically a decline is observed. It is concluded that the threadline temperature profile can be altered in such a way as to significantly enhance the resulting spinning performance and fiber structure over a wide range of take‐up speeds.
Slow‐gelling Cr+3/polyacrylamide solutions for reservoir profile modification: Dependence of the gelation time on pH
Authors: Lockhart Thomas P. , Albonico Paola , Burrafato Giovanni
Published: April 2003

Systematic studies of the gelation of both buffered and unbuffered aqueous Cr+3/polyacrylamide solutions show that the gelation time is a strong function of pH, increasing by about one order of magnitude per unit decrease in pH for polyacrylamides less than about 7.5% hydrolyzed. The gelation rate also depends strongly on the Cr+3 concentration, the degree of polymer hydrolysis, and temperature. At 25°C, gelation delays of more than 10 months have been obtained; the maximum delay observed at 60°C is about 1 month and at 90°C 1 d. The resistance of buffered gel solutions to change in pH results in significantly longer gelation times at 90°C and low pH than for identical unbuffered solutions; at lower temperatures, however, the differences are insignificant. Most importantly, the use of low pH to control the gelation time of Cr+3/polymer solutions provides an attractive, inexpensive substitute for the environmentally unacceptable Cr+6/reductant method currently employed for profile modification treatments.
Influence of nonsolvents on dissolution characteristics of nylon‐6
Authors: Raju K. V. S. N. , Yaseen M.
Published: April 2003

The dissolution of nylon‐6 has been made effective by adding a nonsolvent to the primary solvents that in turn created potential combined contact sites and enhanced the process of dissolution. It is found that 50% of a primary solvent like m‐cresol or phenol could be replaced by solvents that are relatively economical and safe to handle. Nylon‐6 is found to get dissolved at a faster rate and with ease in a blend of 45 : 55 phenol‐toluene compared to other solvent blends. The dependence of limiting viscosity on solute‐binary solvent interactions is used as a measure of the solvency power of solvent blends for nylon. The lowering of temperature is found to favour the dissolution of nylon‐6 in m‐cresol. Its dissolution is found to be optimum in phenol at 55°C and further increase in temperature has adverse effects on it.
Dimethyl acetamide sorption equilibria in a urethane/urea/ether block copolymer
Authors: Gou M. M. , Koros W. J. , Goldman G. W.
Published: April 2003

A study of the interaction of solvent in a urethane/urea/ether copolymer belonging to the spandex family of materials is presented. Sorption and desorption isotherm data for N,N‐dimethylacetamide (DMAc) in spandex solutions are used to determine thermodynamic parameters of solvent/polymer interaction. Isosteric enthalpies for sorption of DMAc tend to approach the heat of evaporation of DMAc at high sorbed concentrations. A qualitative mechanism for assemblage of hard‐segment domains in the polymer during desorption is presented and interpreted in terms of the sorption isotherms and isosteric enthalpy data. The study provides useful insights into the influence of particulate additives, such as titanium dioxide (TiO2) in the solution.
Application and development of synthetic polymer membranes. VI. Pervaporation of aqueous ethanol solution through quaternized poly[3‐(N′,N′‐dimethyl) aminopropylacrylamide‐co‐acrylonitrile] membranes
Authors: Yoshikawa Masakazu , Ochiai Satoshi , Tanigaki Masataka , Eguchi Wataru
Published: April 2003

Membranes obtained from polymers, quaternized poly[3‐(N′,N′‐dimethyl) aminopropylacrylamide‐co‐acrylonitrile]s, showed selective separation of water from aqueous ethanol solution by pervaporation. The separation factor toward water reached over 15,000. Membrane performance showed a good correlation to membrane polarity. Differential scanning calorimetric melting endotherms of the water‐swollen membranes were studied to clarify the state of water in the membranes. The results suggested that there are two states of water in the membrane: bound and free. The higher the fraction of bound water in the membrane, clearly, the more preferentially was water permeated.
Coated alginate microspheres: Factors influencing the controlled delivery of macromolecules
Authors: Wheatley M. A. , Chang M. , Park E. , Langer R.
Published: April 2003

A systematic study of the mild alginate/polycation microencapsulation process, as applied to encapsulation of bioactive macromolecules such as proteins, was conducted. When protein drugs were suspended in sodium alginate solution and sprayed into 1.3% buffered calcium chloride to form cross‐linked microcapsules, large (up to 90%) losses of encapsulation species were encountered, and moderate to strong protein‐alginate interactions caused poor formation of capsules. As a result, a diffusion‐filling technique was adopted in which blank alginate beads, coated twice with small amounts of polycation, were formed prior to drug loading. Protein was then loaded into these capsules by stepwise diffusion from solutions of increasing drug concentration. The drug‐loaded capsules were coated with a final layer of polycation. In all, three polycation coatings were used, two prior to filling and one after filling. The first coating strongly influenced the size, integrity, and loading capacity of the capsules. Low concentrations of polycation resulted in poorly formed capsules with very low retention of the drug in the final capsule, while very high concentrations prevented the drug from entering the capsule at the filling stage. This first coat also affected the duration of drug release from the capsule and the size of the burst effect. The second coat had less effect on the capsule integrity, but it did influence the drug payload and relase profile. The final, sealing‐coat had little effect on drug payload and only limited effect on the release profile up to a critical concentration, above which the release profile was not affected. For all coats, increasing polycation concentration decreased the burst effect, and caused the release profile to be more sustained. Encapsulation of a series of dextrans with increasing molecular weight revealed that the release profile was directly related to the molecular weight of the diffusing species, which was more sustained as molecular weight increased. We have shown that the choice of coating parameters in the diffusion‐filled, alginate/polycation system is critical for successful drug delivery from these capsules. By carefully choosing the coating parameters, both the drug payload and the release profile can be fine‐tuned to meet the desired profile.
Enzymatic hydrolysis of water‐soluble random copolypeptides
Authors: Hayashi Toshio , Iizuka Yasuko , Oya Masanao , Iwatsuki Makoto
Published: April 2003

Two component water‐soluble random copolypeptides consisting of N‐hydroxyethyl L‐glutamine and hydrophobic L‐amino acids such as L‐alanine, L‐leucine, L‐phenylalanine, or L‐valine, were prepared by carrying out aminolysis reactions with 2‐amino‐1‐ethanol (E) on starting copolymers consisting of γ‐benzyl L‐glutamate (B) and the corresponding hydrophobic L‐amino acid. The effects of copolymer composition and sequential distributions, as well as molecular conformations, on the rate of degradation by bromelain in a PECF at pH 7.4 and 37.0°C to simulate in vivo polymer degradation. All the samples were found to be extensively degraded by random chain fracture with bromelain. Further, the degradation data for these samples followed the Michaelis‐Menten rate law, being of the first order in papain concentration. The nature of side chains and the molecular conformations are important to the rate of degradation by bromelain.