bluuebunny/crossref_metadata_2025 huggingface dataset:
Coatings and surface modification by methane plasma polymerization
Authors: Ho Chung‐Peng , Yasuda H.
Published: April 2003

Polymers formed from plasma‐polymerized methane were employed to modify the surface properties of silicone rubber membrane. Polymers were evaluated based on the energy input parameter W/FM, where W is the discharge power, F is the monomer flow rate, and M is the molecular weight of the monomer. Dealing with the characteristics of plasma polymerization and the deposited polymer film, the effect of pumping rate on deposition rate and the coating thickness, surface energy, and gas permeabilities of methane‐plasma‐polymer‐coated silicone rubber membrane were investigated in three plasma regions. Because more reactive species are expelled at high pumping rates, the monomer‐deficient region is reached at lower W/FM in the high pumping rate system than that in the low pumping rate system. The composite parameter W/FM had a strong influence on coating thickness, gas permeability, surface energy, and the polar component of the surface energy but little effect on its dispersion component. Examination of gas permeabilities indicated that coating thickness was another important controlling factor on the properties of plasma polymer.
Bismaleimide and bisazomethine high temperature polymers
Authors: Chattha M. S. , Siegl W. O.
Published: April 2003

Conjugated aromatic bisazomethine, resulting from the reaction of terephthaldicarboxaldehyde and aniline, has been found to react with bismaleimidodiphenylmethane to provide polymeric compositions with glass transition temperature higher than 300°C. These two materials form a low viscosity melt at ca. 150°C and the melt shows only a small viscosity increase when maintained at 120°C over a period of 8 h. Differential scanning calorimetry (DSC) of this composition shows that upon heating above 200°C, it cures rapidly to produce a thermally stable polymer. Thermal mechanical analysis (TMA) of the cured composition does not detect any softening up to 350°C. In the thermal gravimetric analysis (TGA), no weight loss is observed up to 400°C in air and the material leaves a rather large amount of residue (ca. 60%) even up to 600°C. Dynamic mechanical thermal analysis (DMTA) shows that the polymer maintains its high modulus with increasing temperature up to 250°C.
Copolymer of ketonic resin–polyacrylonitrile
Authors: Akar Ahmet , Gali̇oǧlu Oya , Göçmen Ayten , Sarac A. Sezai̇
Published: April 2003

The polymerization of acrylonitrile in the presence of Ce(IV) salts and ketonic resin such as methyl ethyl ketone/formaldehyde and cyclohexanone/formaldehyde resin was investigated. Block copolymer of ketonic resin–polyacrylonitrile was produced. The effect of Ce(IV) concentration, temperature, time, and monomer concentration on the yield and molecular weight was studied. Maximum yield was obtained at 50°C and ceric ammonium nitrate concentration of 0.033 mol/L.
X‐ray diffraction studies in resins: Effect of entanglements and chain structure
Authors: Swarup S. , Nigam A. N.
Published: April 2003

X‐ray diffraction halo of alkyd, amino, and epoxy resins were recorded. The effective d obtained from them was used to estimate certain physical parameters like cross‐sectional area, number of carbon atoms per chain, and stiffness parameters from the empirical curves of Boyer and Miller. Amino resin was found to behave differently than the rest of the resins which have a benzene ring in their backbone. These ideas find a confirmation from the ultrasonic and dielectric measurements performed on these very samples.
High performance size exclusion chromatography of poly(organo)phosphazenes
Authors: De Jaeger R. , Lecacheux D. , Potin Ph.
Published: April 2003

The determination of the molecular weights of polyorganophosphazenes can only be achieved with great care. The nature of the substituents, the proportion of residual chlorine atoms after substitution, and also any traces of hydrolysis can considerably modify the behavior of these polymers in solution and thus lead to erroneous results. In our current research we have been developing a characterization method based on steric exclusion chromatography, coupled with a light scattering detector. We have used columns with styrene–divinylbenzene organic micropacking as the stationary phase and THF with added LiBr (0.1 mol/L) as the eluent. This method has enabled us to establish accurate correlations between molecular weight, hydrodynamic volume, and viscosimetric measurements for polyaryloxyphosphazenes of varying structures and origins. The method also provides results which agree very well with the variables for the preparation of polyphosphazenes, which is based on polycondensation of P‐trichloro‐N‐dichlorophosphoryl monophosphazene Cl3P = NP(O)Cl2. Finally this method allows us to show that, despite their mineral backbone, these polymers obey Benoit's universal calibration concept.
Studies on the temperature dependence of extinction oxygen index values for cellulosic fabrics: III. Comparison with limiting oxygen index for commercial flame‐retarded cotton
Authors: Horrocks A. R. , Price D. , Tunc M.
Published: April 2003

Limiting oxygen index values of single and multilayer Proban CC‐ and Pyrovatex CP‐flame retardant finished cotton fabrics having a variety of area densities were determined as a function of igniter application time and temperatures up to 200°C. Except for the lightweight (140 g m−3) Proban CC‐treated fabrics, LOI, like comparable extinction oxygen index (EOI) values, increased as ignition times were increased from 2 to 10 s. Extrapolation to zero ignition time enabled [LOI]0 values to be determined at each temperature, which, for a given flame retardant, increased linearly with area density of mono‐ and multilayered fabric combinations. Comparison with earlier extinction oxygen index results showed that this [LOI]0 vs. area density dependence had significantly lower correlation than that for [EOI]0. These ṕoor former correlations further substantiated the claims that the EOI concept offers a more effective means of quantifying textile fabric flammability. Analysis of the linear relationships enabled intrinsic limiting oxygen index, L0, and area density‐dependent, L1, terms to be determined. Like conventional LOI values, L0, values also reduce significantly at elevated temperatures.
Surfactant effects in the emulsion polymerization of vinyl acetate
Authors: Lee C. H. , Mallinson R. G.
Published: April 2003

Continuous vinyl acetate emulsion polymerization was carried out by using a mixed surfactant system of “Aerosol” OT (AOT) and sodium dodecyl sulfate (SDS). It is well known that the AOT reduces surface tension considerably and has stronger monomer solubilization power than SDS. In this work, particular attention is given to observe the effects of the mixed surfactant on the molecular weights and polydispersities. In comparison with experiments using only SDS, the particle size appears similar, in the range of 190–280 nm. The conversion increased substantially to the 70% range from the 50% level observed with only SDS. All experiments were conducted at 60°C with a mean residence time of 30 min. The total surfactant concentration was maintained at 0.03 mol/L water for all experiments. It was found that once some AOT was included in the surfactant, the behavior was very similar to that observed with only AOT. The number average molecular weights were found to decrease substantially while the polydispersity increases dramatically to about 12. It is believed that AOT may act as a significant chain transfer agent in the polymerization.
Studies on the aging process of a highly condensed resol resin
Authors: Latocha Czesław , Balcerowiak Wojciech
Published: April 2003

The nature of the structure changes of a highly condensed resol resin during its aqueous solution storage was considered. To this end, the curing process of the resin was investigated by means of DTA and its structure was analyzed by means of NMR. The hypothesis relative to stability of the hemiformal bonds was made.
Acoustic properties of transparent polysiloxanes
Authors: Bosc D. , Mauguen P.
Published: April 2003

It is well known that the glass transition temperature of polydimethylsiloxane elastomers lies close to −120°C. According to the time temperature superposition principle, we may state that these materials keep their caoutchoutic state when they are excited by a 10 MHz mechanical wave. This is an important point particularly for acoustooptic applications. Thus, in the range of 1–10 MHz, materials with good efficiency are missed; low acoustic wave velocity is needed to give the best conditions, which means to be in a caoutchoutic state for polymeric materials. With this work, we show that three polysiloxanes, polymerized under different conditions, do not fulfill this condition. Thus the shift of Tg with frequency is very large and these polymers reach their glassy state at relatively low frequency. The acoustic wave velocity is in good agreement with mechanical predictions provided by master curves of the Young modulus.
The effect of agitation, purge time, and nonsimultaneous addition of acid and initiator on xanthated cellulose–polystyrene graft copolymer
Authors: Graczyk Tomasz , Hornof Vladimir
Published: April 2003

Conversion to polymer and molecular weight of grafted copolymer in the graft copolymerization of styrene initiated by the xanthate method is strongly dependent on reaction conditions even in the range of agitation speed when the effect of diffusion of monomer is neglected. When sulfuric acid and hydrogen peroxide are added simultaneously after 15 min of purging with nitrogen 99.99%, conversion and molecular weight vary little with stirring speed. Both parameters decrease with increasing stirring speed when H2 SO4 is added 1 min earlier than H2O2 and nitrogen is purged 15 min before starting the reaction. Both parameters increase when H2SO4 and H2O2 are added simultaneously after 60 min of purging with nitrogen. Highest conversion is observed when both reagents are added after 15 min of purging with nitrogen. Molecular weight is the highest at 310 rpm when H2SO4 is added 1 min earlier than H2O2, and at 1100 rpm when nitrogen is purged for 60 min.
New biodegradable films from exploded wood solutions
Authors: Paillet M. , Peguy A.
Published: April 2003

In this paper experimental results obtained with the exploded wood/tertiary amine oxide system are presented. The use of particular conditions leads to the formation of new biodegradable films. These films may have a natural color from brown to black. The mechanical properties are studied and a comparison with a black commerical synthetic film is made. The structure of the films is made. The structure of the films is studied as well as the role of lignin as an antioxidant.
Graft copolymerization onto wool fibers: Grafting of acrylamide onto wool fibers initiated by potassium monopersulphate/Fe (II) redox system
Authors: Giri Gitisudha , Sahoo Prafulla K. , Samal Rajani K.
Published: April 2003

Graft copolymerization of acrylamide (AM) onto wool fibers has been studied in aqueous solution with a new redox initiating system, KHSO5/Fe(II). For estimation of comparative influence of salts and selection of reaction medium, grafting has also been studied in the presence of a multitude of inorganic salts and some organic solvents. It was observed that the graft percentage was influenced by the reaction time, temperature, concentration of monomer initiator, FeSO4, and the base polymer. A maximum graft percentage of 120.5% was obtained at 35°C with the concentration of AM (0.8M), KHSO5 (0.0195M) and Fe (II) (2.5 X 10‐3 M) for reaction time of 2 h. From the experimental results, a suitable reaction mechanism for graft initiation and termination has been suggested. The water retention of the grafts and their behavior towards mineral acids and alkalis have been tested. The tensile strength and the thermal stability of the grafts have also been determined and compared with the base.
Yield and fracture mechanisms in ABS
Authors: Chen C. C. , Sauer J. A.
Published: April 2003

The deformation and fracture characteristics of ABS have been investigated under tension, compression, and tension‐compression fatigue cycling. The behavior of the rubber‐modified polymer is compared with that of unmodified styrene‐acrylonitrile, copolymer. The dispersed rubber particles in ABC cause extensive plastic deformation of the matrix material, markedly reduce the compressive yield stress, and, under tensile loading, cause yielding rather than early fracture. Under alternating stress conditions crazes occur sooner and lead to earlier craze breakdown, crack development, and reduced lifetime to fracture. The influence of rate of loading has been studied under applied tension and under fatigue cycling. The tensile yield stress varies linearly with the log of the strain rate in accord with the Eyring rate equation and, from the measured slope, the activation volume is estimated to be 2.2 nm3. The time to fatigue fracture reduces significantly with increasing frequency while cycles to fracture increase at a modest rate. Fatigue failure in ABS is not a cycle‐dependent process, nor is it in accord with a damage accumulation model, but it more nearly resembles the former. The influence of a dispersed rubber phase, and of loading rate, on fracture surface morphology is discussed.
Fatigue crack propagation in microlayer composites of polycarbonate and poly(styrene–acrylonitrile)
Authors: Ma M. , Im J. , Hiltner A. , Baer E.
Published: April 2003

The effect of layer thickness on fatigue crack propagation (FCP) in microlayer composites of polycarbonate (PC) and styrene–acrylonitrile copolymer (SAN) has been studied. Variation in layer thickness was achieved by increasing the number of layers from 49 to 776 while keeping the overall sheet thickness and composition the same. It was found that the 776 layer composite had a larger number of fatigue cycles from crack initiation to fracture, a longer stable crack length and higher value of critical strain energy release rate J1C. Microscopic characterization of the damage zone and resulting fracture surface revealed a transition from SAN crazing to shear deformation as layer thickness decreased from 18 to 1 μm; the resulting plastic deformation and ductile fracture of the 776 layer composite was responsible for the enhanced FCP resistance. The ductile fracture mechanism produced a measurable temperature rise at the crack tip that revealed the stop–start nature of crack propagation.
Studies on impact modification of polystyrene (PS) by ethylene–propylene–diene (EPDM) rubber and its graft copolymers. III. PS/EPDM‐g‐(styrene‐co‐maleic anhydride) blends and its relative performance
Authors: Shaw S. , Singh R. P.
Published: April 2003

The graft copolymer of ethylene–propylene–diene (5‐ethylidene‐2‐norbornene) rubber with styrene and maleic anhydride is synthesized, characterized, and blended with polystyrene. The tensile and the impact behaviors of the blends were investigated. The relative performance of EPDM‐g‐(styrene‐co‐maleic anhydride) as impact modifier for polystyrene has been evaluated.
Water‐soluble sulfonated amino‐formaldehyde resins. V. Effect of reaction condition on molecular weight distribution
Authors: Lahalih S. M. , Hovakeemian G.
Published: April 2003

The effect of reaction conditions of sulfonated urea‐melamine formaldehyde on molecular weight distribution was studied. It was found that the molecular weight distribution of these materials is influenced by the percent of urea to melamine in the mixture, the concentration of the reaction mixture, the pH and the time of reaction of the low pH condensation step, and finally, the reaction time during the high pH condensation and rearrangement step. Weight average molecular weights increased as percent melamine to urea, concentration of reaction mixture, the alkalinity of the third step, and the reaction time of the fourth step increased. The weight average molecular weight decreased as the reaction time of the third step decreased. The reaction variables influenced the fraction of the high molecular weight species that, in turn, influenced these materials performance. Finally, it appeared that the final product contained separate sulfonated urea formaldehyde and sulfonated melamine formaldehyde components in addition to sulfonated urea‐melamine formaldehyde polycondensates.
Pseudosteady states in semicontinuous emulsion copolymerization
Authors: Dimitratos J. , El‐Aasser M. S. , Georgakis C. , Klein A.
Published: April 2003

The appearance of pseudo‐steady states in semicontinuous emulsion copolymerization is studied. Different correlations between the monomer feed rate and the polymerization reaction rate proposed in the literature for homopolymerization systems can be derived from a unified view as presented in this work. The theoretical analysis for copolymerization systems predicts that the individual consumption rates of both monomers involved assume a constant value if the monomer addition rates are kept constant. Different cases for either fixed radical concentration or seeded polymerization with water‐soluble or sparingly water‐soluble monomers are considered. The assumptions and results of the analysis are tested against experimental data from the seeded copolymerization of vinyl acetate/n‐butyl acrylate.
Polyimides and polyamide–imides containing arylene sulfone ether linkages
Authors: Idage S. B. , Idage B. B. , Gunjikar V. G. , Vernekar S. P.
Published: April 2003

Polyimides and polyamide–imides containing arylene sulfone ether linkages were synthesized from 4,4′‐bis(4‐isocyanatophenoxy) diphenylsufone (SPI), 4,4′‐bis(3‐isocyanatophenoxy) diphenylsulfone (SMI), pyromellitic dianhydride (PMDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and trimellitic anhydride (TMA) using one‐step method. The diisocyanates SPI and SMI were synthesized from 4,4′‐bis (4‐carboxyphenoxy) diphenylsulfone (SPA) and 4,4′‐bis(3‐carboxyphenoxy) diphenylsulfone (SMA) by a Weinstock‐modified curtius rearrangement method. All the polycondensation reactions were carried out in N‐methyl‐2‐pyrrolidone (NMP) and the polymers obtained were characterized by infrared spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction.
Effect of γ‐irradiation and temperature on the structure of metal‐chloride‐treated poly(vinyl alcohol)
Authors: Rabie S. M. , Abdel‐Hakeem Nagwa , Moharram M. A.
Published: April 2003

The infrared and ultraviolet spectra of poly(vinyl alcohol)(PVA) treated with ferric chloride and zinc chloride were recorded. Careful examination of the infrared spectra revealed that these treatments cause significant changes in the crystallinity of PVA, particularly in the case of the treatment with ZnCl2. The results showed that exposure of untreated and FeCl3‐treated PVA to 12 or 28 Mrds results in no observable changes in their ultraviolet and infrared spectral features, whereas exposure of ZnCl2‐treated PVA at the same dosages, results in the appearance of an absorption band at 1595cm‐1 corresponding to β‐diketone groups. It was also found that γ‐irradiation of ZnCl2‐treated PVA produces a remarkable change in its crystallinity. Moreover, the effect of heat on the spectral features of the ZnCl2‐treated PVA was discussed. It was found that the treatment of PVA with ZnCl2 helps in oxidative degradation of PVA.
Synthesis and characterization of thermo‐sensitive polymeric beads
Authors: Abe Takashi , Egawa Hiroaki , Ito Hiroshi , Nitta Atsuhiko
Published: April 2003

Thermo‐sensitive polymeric beads were synthesized by inverse suspension polymerization of aqueous monomer solution containing N‐acryloylpyrrolidine (APR) and N,N′‐methylenebisacryl‐amide (MBA : crosslinking agent). The polymerization conditions such as dispersion medium, dispersing agent, monomer, and initiator concentration were investigated. Fine spherical gels with diameter of 50–500μm were obtained in high yield. The swelling volume of these gels in water continually decreased by raising atmospheric temperature and vice versa. The degree of swelling increased for the gels synthesized with lower degree of crosslinking or with lower monomer concentration at polymerization. The degree of swelling was high in water and alcohols, but the gels swelled even in nonpolar organic solvents, although the degree of swelling was low. The pore radius distribution of the gels was determined by aqueous size exclusion chromatographic method to investigate relations between pore characteristics of the gels and polymerization conditions. Monomer concentration had large effect on pore size, porosity, and pore volume of the gels. On the other hand, degree of crosslinking had little effect on these pore characteristics.
Cure kinetics of epoxy/anhydride thermosetting matrix systems
Authors: Woo E. M. , Seferis J. C.
Published: April 2003

The kinetics of bisphenol‐A diglycidyl ether epoxy (DGEBA) cured with trimellitic anhydride (TMA) were studied using differential scanning calorimetry (DSC) and FT‐IR under isothermal temperatures in the range of 100–200°C. The effects of an onium salt catalyst and styrene monomer (a reactive diluent additive) on cure kinetics of the DGEBA/TMA resin systems were also investigated. For the uncatalyzed DGEBA/TMA system, the reaction was found to be second order up to a fractional conversion of 0.8, where a diffusion‐limited reaction regime was observed as the matrix gelled. The apparent activation energy was calculated to be 11.3 kcal/mol. The cure reaction of the catalyzed DGEBA/TMA system was found to be second order up to a fractional conversion of 0.3 and first order thereafter. The apparent activation energy of the catalyzed resin system was calculated to be 12.3 kcal/mol. In the FT‐IR investigation, it was discovered that the KBr powder catalyzed the cure reaction. Additionally, the styrene component in the styrene‐DGEBA/TMA resin system polymerized independently in the later stage of the cure reaction of the epoxy component. Therefore, the styrene monomer had little effect on the kinetics of cure reaction of the epoxy system.
Polybutadiene grafting and crosslinking in high‐impact polystyrene bulk thermal process
Authors: Peng Fred M.
Published: April 2003

The grafting and the crosslinking of polybutadiene during the bulk thermal polymerization of high‐impact polystyrene were studied. The kinetic equations for these two reactions were derived by the use of the moments of the distribution functions. This kinetic model indicates that both the density of grafting and the degree of crosslinking increase with the increasing temperature of polymerization and, most significantly, with the increasing conversion of styrene.
Processing‐morphology‐property relationships in epoxy resins containing an organometallic cobalt complex
Authors: Mijović Jovan
Published: April 2003

An investigation was carried out into the effect of an organometallic complex, cobalt (III) acetylacetonate, on curing, morphology, and mechanical properties of several epoxy resins. Differential scanning calorimetry, electron microscopy, and a series of mechanical measurements were performed on bifunctional and terafunctional formulations. The addition of cobalt (III) acetylacetonate did not cause drastic changes in any of the systems investigated, although a slight effect on cure kinetics, Young's modulus, and fracture‐surface morphology was noted. Also, there was no effect on the impact strength or the critical stress intensity factor of any of our formulations.
Low pressure polymerization of propylene: Kinetics
Authors: Pandya M. V. , Lata K. V.
Published: April 2003

Kinetic studies on low pressure polymerization of propylene using the catalyst system VOCl3 + AIEt3 and Et2AlCl are reported. Effect of various parameters such as the [Al]/[V] ratio, catalyst concentration, reaction time, temerature, solvents, and additives on rate of the reaction, yield, and % conversion were studied. Each of these parameters had a profound effect on the yield and rate of the reaction for both the systems. Triethylamine was found to increase the yield and the rate of polymerization. We also found that aliphatic hydrocarbons acted as a better polymerization medium than aromatic ones.
Dynamic mechanical characterization of tire cord dip films
Authors: Das B. , Girgis M. M.
Published: April 2003

Various dip films with different amounts of F/R resins, polybutadiene latex, styrene/butadiene/vinyl pyridine terpolymer latex, and/or with carboxylated butadiene latex were prepared on a Teflon‐coated hot plate by spraying the properly formulated dip mixes using a Binks air gun. These dip films were cured at 300°F in hot air oven between two Teflon plates. A DDV‐IIC Rheovibron instrument was used to measure elastic modulus (E′), loss modulus (E″), and tan δ (E′′/E′) of different dip films. Dip films with higher F/R resin (11 vs. 7%) concentration gave higher tan δ values which peaked between −20 and −30°C. Films with higher resin concentrations were also found stiffer (higher E′), if all other ingredients of the films were identical. Dip films, where more than 40% of the film ingredient was polybutadiene, showed a phase‐separated glass transition temperature for polybutadiene between −60 and −90°C. Films, with 40% polybutadiene and 7.0% F/R resin and the rest of the ingredients being styrene/butadiene/vinyl pyridine and other additives such as wax, silanes, etc., gave two distinct glass transition temperatures: one between −60 and −80°C for polybutadiene and the other for complex between F/R resin and vinyl pyridine around −20 and −30°C. Tire cords coated with dip mixtures of lower tan δ values in the −20 to +20°C range gave better fatigue performance in the Gristmill tire test at room temperature. Tire cords coated with dip mixtures containing 40% polybutadiene and 7.0% F/R resin exhibited phase separated two distinct glass transition peaks in the temperature ranges of −60–−90°C and −20–−30°C. Films of the above formulations showed low modulus and high elongations. Cords coated with the above dip mixtures gave good fatigue performance in the Firestone cold wheel test at −50°C. It so happens that, in this temperature range of −30–−60°C, the above phase‐separated dip films go through a minimum damping value and, therefore, give superior tire performance.
Graft copolymerization by iniferter method; structural analyses of graft copolymer by glass transition temperature
Authors: Yamashita K. , Ito K. , Tsuboi H. , Takahama S. , Tsuda K. , Otsu T.
Published: April 2003

Since 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC) polymer easily cleaves at the C—S bond and generates benzyl radical, graft copolymerization of methyl methacrylate (MMA) or 4‐vinylpyridine (VPy) onto VBDC polymer is easily performed by UV irradiation. The structural analyses of the graft copolymers are performed through glass transition temperature measurements. The graft copolymers of MMA have one Tg and VPy graft copolymers have two Tg's arising from the main and side chains. It becomes clear that the mode of side chains propagation is significantly different for each of the second monomers used.
Effect of prevulcanisation of natural rubber latex on the chemical and physical properties of latex thread
Authors: Peethambaran N. R. , George Tessy K.
Published: April 2003

The effect of prevulcanisation on the processing properties and network structure of a series of latex compounds containing conventional and efficient vulcanisation (E.V. systems) systems for the manufacture of latex thread was evaluated. Prevulcanisation was effected at 70°C and the extent of crosslinks formed and compound viscosity at various periods of heating were studied. It is observed that the vulcanisation systems studied have a profound effect on the extent of crosslink formation during prevulcanisation. The network structure of the vulcanisate was also studied and found that polysulphidic content is high as the extent of prevulcanisation of the latex compound increases. Latex threads were also prepared from typical latex compounds which were prevulcanised to different degrees and their chemical and physical properties were evaluated. It is observed that the extent of prevulcanisation affects the aged and unaged physical properties of latex threads.
Pilot plant synthesis of methacrylate copolymer precursors to nonlinear optical materials
Authors: Katz H. E. , Bohrer M. P. , Mixon D. A. , Alonzo J. , Markham J. , Sohn J. E. , Cox D. I.
Published: April 2003

The copolymerization of methacrylates with methacrylates containing anilino side chains was investigated. Azobis(isobutyronitrile) was a better initiator than benzoyl peroxide. Continuous feed of initiator was advantageous compared to adding the initiator all at once. The reaction was scaled up using a 10‐L reactor, ultimately yielding hundreds of grams of the desired copolymers, which are valuable precursors to polymeric dyes used in nonlinear optical studies.
Polyurethanes from aromatic bischlorformates
Authors: Morgan Paul W.
Published: April 2003

Linear polyurethanes, having high molecular weight, were prepared by interfacial polycondensation from halogen substituted aromatic bischloroformates and aliphatic diamines, piperazines, and aromatic diamines. Examples of specific intermediates are hexamethylenediamine, piperazine, homopiperazine (see formula), m‐phenylendiamine, and the bischloroformates of 2,2‐bis (4‐hy‐droxy‐3,5‐dichlorophenyl) propane, 2,2‐bis(4‐hydroxy‐3,5‐dibromophenyl) propane, and 2,2‐bis(4‐hydroxyphenyl) hexafluoropropane:
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In comparison with corresponding unhalogenated polyurethanes, the polymers from this study, particularly those based on piperazines, had high glass transition and softening temperatures. Polyurethanes in this class, like most ring‐containing polyurethanes, do not have sufficient thermal stability at their high melting points for easy melt for easy melt forming. They were more soluble in a variety of common solvents and had excellent resistance to ultraviolet light. Surprisingly, the irregularity introduced into the polymer chain by the use of such intermediates as homopiperazine (formula above) or 2‐methylpiperazine did not inhibit crystallization. On the other hand the symmetry provided by trans‐2,5‐dimethylpiperazine greatly reduced solubility in many solvents. Several polyamides and a polyurea from homopiperazine are included.
Influence of the matrix thickness on radiation‐induced grafting of styrene onto poly(ethylene terephthalate) films and nuclear membranes
Authors: Zhitariuk N. I. , Zagorets P. A. , Kuznetsov V. I.
Published: April 2003

Radiation‐induced graft polymerization of styrene onto poly(ethylene terephthalate) (PET) nuclear membranes and films was performed by various methods, viz., preirradiation in air and in a vacuum. The grafting yield obtained via the preirradiation in a vacuum was considerably higher than that obtained under the same conditions by preirradiation in air. The higher the average distance between pores is, the higher the grafting yield. But when grafting is performed onto both the membranes with average distance between pores and films with different thickness, the grafting yield passes through the maximum as the thickness increases. When the average distance between the pore walls of a membrane is equal to the film thickness, the grafting rate onto the film is higher than that onto the membrane. This is attributed to growth of the termination rates both the active sites within the polymeric matrix and the growing macroradicals during graft polymerization. Both the processes proceed at the phase boundary. The boundary area increases as a result of chemical treatment in the course of nuclear membrane manufacturing. The values of the characteristic parameter α and the critical thickness for styrene grafting onto nuclear membranes and films have been obtained.
Synthesis and characterization of some polyaniline–organic acceptor complexes
Authors: Khor S. H. , Neoh K. G. , Kang E. T.
Published: April 2003

The charge transfer (CT) interactions between polyemeraldine (PEM) and six organic electron acceptors were studied. The complexing ability of the acceptors, based on the maximum attainable electrical conductivity of the resulting complex, could be arranged in the following ascending order:tetrachloro‐p‐benzoquinone (p‐chloranil), tetrafluoro‐p‐benzoquinone (p‐fluoranil), tetrabromo‐o‐benzoquinone (o‐bromanil), 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ), tetrachloro‐o‐benzoquinone (o‐chloranil), and tetracyanoethylene (TCNE). Conductivity in the order of 10‐1 S/cm was achieved in the PEM/TCNE complex. The complexes were also characterized by infrared (IR) absorption spectroscopy, thermogravimetric (TG) analysis, and X‐ray photoelectron spectroscopy (XPS). In most complexes, the CT interactions have proceeded further than the formation of pure molecular complexes. However, the mechanism of CT interaction was found to be analogous to that of protonation of PEM by protonic acids.
Fibers from polyurethanes based on halogen‐substituted bisphenols
Authors: Morgan Paul W.
Published: April 2003

Fibers were prepared on an experimental scale by wet and dry spining from eight, nonelastomeric polyurethanes based on halogen‐substituted bisphenols. The fibers had properties suited to clothing textile uses. They were examined primarily for their potential in wash and wear fabrics. The fibers had moderate water absorption, low shrinkage in hot water, modest lowering of tensile properties under wet conditions, high tensile and work recoveries, and good stability to ultraviolet light. The polyurethanes from piperazines and 2,2‐bis (4‐hydroxy‐3,5‐dichlorophenyl) propane bischloroformate had unusually high thermal transitions and good solubility combined with ease of orientation and crystallization in fiber form. Fibers from the 2‐methylpiperazine and homopiperazine urethanes were converted to fabrics. These fabrics exhibited a silklike handle, good wash wrinkle recovery, resistance to soil and bleach, stability to ironing at 200°C, and very low flammability.
Curing kinetics of polyurethane reactions
Authors: Chern Chorng‐Shyan
Published: April 2003

The curing reactions of polyurethane resins are accelerated by electron donors (e.g., hydroxyl group) and electron accepting materials (e.g., carboxyl group and dibutyltin dilaurate). As the critical extent of reaction is reached, a three‐dimensional cross‐linked network is formed. Afterwards, most of the reactive functional groups are attached to the cross‐linked network. The mobilities of these reactive functional groups are seriously restricted and the curing reactions become diffusion controlled. This could lead to incomplete extent of reaction. Based on elementary reaction mechanisms a kinetic model is developed. The concept of diffusion‐limited reactions is used to describe the phenomenon of limiting extent of reaction. Changes in free volume are related to changes in the rate constants with extent of reaction. When the model is applied to experimental data available in the literature, agreement between the model predictions and experimental data is reasonably good.
Dynamic mechanical properties of low‐density and linear low‐density polyethylenes. Influence of molecular segregation
Authors: Orozco J. A. Gonzalez , Rego J. M. , Katime Issa
Published: April 2003

The dynamic mechanical properties of different low‐density and linear low‐density polyethylenes have been measured as a function of crystallization conditions. The mechanical results have been explained accounting for molecular segregation as well as reorganization capacity of the crystallizable segments during isothermal thickening. The presence of a high amount of segregated material does not allow detection of any relationship between crystallization conditions and mechanical relaxations for three of the four samples. The average values of the resonance relaxation temperatures and the relaxation strengths are dependent on branch content and branch type.
High‐performance thermoplastic toughened BMI matrix system. II. Interface study
Authors: Liao Yih‐Tyan , Lin Chen‐Ron , Liu Wen‐Liang
Published: April 2003

Bis‐maleimide (BMI) has recently attracted condsiderable attention as an important matrix resin for high‐performance composites, due to its outstanding high‐temperature performance. First‐generation BMI is too brittle for primary strauture. Our toughening approach began by dissolving PEI (polyetherimide) into compatible dially compound (Matrimid 5292 B, Ciba Geigy) prior to coreaction with BMI resin. In this note, the toughness and interface properties were investigated for the toughened matrix system.
Influence of phthalic anhydride as a coupling agent on the mechanical behavior of wood fiber–polystyrene composites
Authors: Maldas D. , Kokta B. V.
Published: April 2003

The performance of phthalic anhydride used as a coupling agent in wood fiber‐filled polystyrene composites have been verified by evaluating the mechanical properties of the composites materials. Generally, mechanical properties improved along with the increase in concentrations of the coupling agent as well as wood fiber in the composites up to a certain limit and then decreased at the higher concentrations. The concentrations of phthalic anhydride and fibers which produce maximum improvements in mechanical properties differ with the change in wood species and pulping techniques. Compared to other efficient coupling agents (e.g., isocyanate), phathlic anhydride's performance seemed inferior.
Temperature dependence of the reaction between some metal oxides and polyacrylic acid
Authors: Rabie S. M. , Sawaby A. , Moharam M. A. , Nassar A. M. , Tahon K. H.
Published: April 2003

The temperature dependence of the reaction between some metal oxides and an aqueous solution of polyacrylic acid was investigated using the infrared measurements. The obtained data indicated that the divalent metal oxides MgO, ZnO, and PbO react rapidly with the polyacrylic acid forming carboxylate salts. The bonding between the acid groups and these metals is purely ionic in character. The reactivity between these metals and the carboxylic acid is inversely proportional to the radius of metal ions. The reaction of Bi2O3, Cr2O3, and TL2O3 is far from complete. However, SiO2 reacts slowly with polyacrylic acid at 0°C only. The results provided strong evidences that the rate of reaction between some metal oxides and polyacrylic acid depends on the temperature of reaction, This rate of reaction is enhanced as the temperature is lowered.
Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) diols. I. Comparison to commercial diols
Authors: Harris Robert F. , Joseph Michael D. , Davidson Carla , Deporter Craig D. , Dais Virginia A.
Published: April 2003

Poly(ethylene ether carbonate)diols (2025 mol wt) have been made by the molecular weight advancement of lower molecular weight oligomers and have been fabricated into polyurethane elastomers by reaction with 4,4′‐MDI and 1,4‐butanediol using the prepolymer method. Polymer structure has been delineated by carbon‐13 NMR. Comparisons have been made to a series of elastomers based on other polyester and polyether polyols (2000 mol wt) under conditions where the only variable was the soft segment structure. The poly(ethylene ether carbonate) diol gives a polymer with a partially phase mixed morphology, a higher ambient temperature modulus, and a lower ΔHm than the other polyester polyols. This lower ΔHm leads to a significantly lower rubbery plateau modulus than the other polyester polyols. Phase mixing is increased by post‐curing at 150°C. Organic solvent resistance is the most outstanding property. The poly(ethylene ether carbonate) diol produces a polymer with predominantly polyester polyol features.
Study of polymer latex coalescence by dielectric measurements in the microwave domain: Influence of latex characteristics
Authors: Cansell F. , Henry F. , Pichot C.
Published: April 2003

The coalescence process of polymer latex particles has been investigated by following simultaneously weight losses and dielectric constants variations during water evaporation in a latex deposited as a film in a resonant cavity at microwave frequency (5 GHz) and under controlled humidity and temperature. Different styrene (S) n‐butyl acrylate (BuA) emulsion copolymer latexes were examined so as to differentiate the behaviors of film forming or non‐film‐forming latexes. In the latter ones, both flocculation and maximum packing points were clearly evidenced, whereas only the first point was shown in the former ones. The effect of other colloidal variables (particle size distribution, surface charge density, particle diameter, ionic strength) have also been studied. It is found that the influence of the last three parameters is reflective of the latex stability and can be well detected by dielectric measurement. Such a method appears to be quite reliable for studying the film‐forming process of latexes having different colloidal characteristics.
The surface migration of extender oil in EPDM vulcanizates
Authors: Zinbo M. , Skewes L. M. , Theodore A. N.
Published: April 2003

Extender oil bloomed on the surface of ethylene–propylene–diene rubber (EPDM) vulcanizates has been analyzed by a dissolution/size exclusion chromatographic (SEC) method. Dissolution is here defined as the quantitative and selective removal of bloomed extender oil from the vulcanizates. The rate of migration of three potentially useful extender oils for windshield‐wiper materials has been determined by the method. In this work a bloomed oil includes both an excluded oil surfaced during the process of vulcanization and a migrated oil surfaced during the course of aging or weathering. Typical initial rates of oil migration in the presence and absence of an excluded oil on the surface of compression‐set EPDM vulcanizates were ca. 0.8 and 2.2 μg/cm2/h at 25°C, respectively. The rate of migration at an attained uniform oil concentration was found to be ca. 0.5 μg/cm2/h for the three extender oils.
The optimization of the smoke suppressant and flame retardant properties of flexible PVC
Authors: Carty P. , Metcalfe E. , Annison W. N.
Published: April 2003

The combination of mixture diagrams and quality functions can be a straightforward and rapid method of simultaneously optimizing polymer formulations for both flame retardancy and smoke suppression. For a semirigid PVC formulation using a three‐component additive mixture it was found possible to raise the limiting oxygen index by over 7 units, while simultaneously reducing smoke production by more than 20%.
Fibers from flexible liquid crystal main‐chain polymers. II. Functional copolymers based on the 4,4′‐dihydroxy‐2,2′‐dimethylazoxybenzene mesogen and spacers based on 2‐dodecenedioic and nonanedioic acids
Authors: Lin C. H. , Maeda M. , Blumstein A.
Published: April 2003

Fibers spun from liquid crystalline solutions or melts are characterized by a high degree of chain alignment which promotes high values of tenacity and tensile modulus in the direction of fiber axis but lower values in the transversal direction. Structural modifications are introduced into the flexible moiety and the mesogenic group to alleviate this shortcoming. The incorporation of a spacer based on 2‐dodecenedioic acids into a thermotropic liquid crystalline polyester was studied. A phase diagram was established to optimize the composition of such copolyesters. A significant increase in mechanical properties on crosslinking through UV irradiation was observed. A remarkable property of such systems is the retention of molecular chain order in spite of temperatures in excess of Tg. This is valid for both crosslinked and uncrosslinked systems. Remarkable also is the crystallization on annealing of a number of copolymer compositions in spite of a structural difference between the comonomer units.
DSC studies of tactic polypropylenes: The correlation of polymer stereochemistry with thermal properties
Authors: Burfield David R. , Loi Patrick S. T. , Doi Yoshiharu , Mejzík Jir̆í
Published: April 2003

A large number of polypropylene samples, of isotacticities spanning the range 0.35 to 1.00 mm, have been examined by differential scanning calorimetry (DSC) in order to establish a calorimetric index for determining stereostructure. Crystallization studies show that the crystallization onset temperature decreases in step with reduced isotacticity. However, samples prepared with supported catalysts show significantly lower crystallization onset temperatures than those from conventional catalysts which is believed to be due to differences in the inter‐ or intramolecular distribution of stereodefects. Furthermore, whole and fractionated samples cannot be fitted by one calibration curve. However, the enthalpy of crystallization is found to be related to the isotacticity by an equation of the form: log ΔH = m log (isotacticity) + c. This relationship is found to be applicable to samples from all types of catalysts examined and to both whole and fractionated samples. Fusion curves have been determined for “as received” as well as conditioned and annealed samples but the melting temperatures are not found to be a reliable guide to isotacticity. The respective enthalpies of fusion are found to follow the same logarithmic relationship stated above and thus can also be used as a basis for a calorimetric isotactic index. Examination of glass transition and related heat capacity data does not provide any clear‐cut alternative index.
Epoxy resins based on aromatic glycidylamines. II. Preparation ofN,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane from 4,4′‐diaminodiphenylmethane: Analysis of product by GPC and HPLC
Authors: Podzimek S̆. , Dobás̆ I. , S̆vestka S̆. , Horálek J. , Tkaczyk M. , Kubín M.
Published: April 2003

N,N,N′,N′‐tetrakis(2,3‐epoxypropyl)‐4,4′‐diaminodiphenylmethane (N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane, TGDDM) and an intermediate of its synthesis,N,N,N′,N′‐tetrakis(2‐hydroxy‐3‐chloropropyl)‐4,4′‐diaminodiphenylmethane (N,N,N′,N′‐tetrachlorohydrin of 4,4′‐diaminodiphenylmethane, TCHDDM), were analyzed by GPC and HPLC. The main impurities were identified by analogy withN,N‐diglycidylaniline (DGA) andN,N‐dichlorohydrin of aniline (DCHA) that had been analyzed in our previous work,1and by IR, NMR, and mass spectroscopy after their isolation by semipreparative HPLC. Attention was also paid to quantitative determination of the TGDDM content and to GPC elution behavior of TGDDM and TCHDDM‐based oligomers.
Surface modification by continuous graft copolymerization. IV. Photoinitiated graft copolymerization onto polypropylene fiber surface
Authors: Yao Zhang Pei , Rånby Bengt
Published: April 2003

Photochemically induced graft copolymerization (with UV light) of acrylamide (AM) and acrylic acid (AA) on polypropylene (PP) fiber surface by the presoaking method under nitrogen atmosphere in a continuous process has been developed. The results are measured by means of ESCA spectra. In grafting AM and AA, the relative intensity N1s/C1s and O1s/C1s of the fiber increase from 3–5 and 20% (background) to 8–13 and 23–39% in 9–10 s irradiation time, respectively. Titration results show that 1.75 3.58 mg/m2 poly(acrylic acid) has been grafted on the surface of PP fiber at various monomer concentrations of the presoaking solution. Commercial additives, such as antioxidant and UV stabilizer, affect the grafting yield of the fiber. As solvent in the presoaking solution, acetone is better than MEK and MPK. Various monomer and initiator concentrations in the presoaking solution have been studied. In the process developed 0.5–0.8 M acrylamide or 1.5–2.0 M acrylic acid and 0.2 M benzophenone (BP) in the presoaking solution are approapriate.