bluuebunny/crossref_metadata_2025 huggingface dataset:
Graft polymerization of methyl methacrylate on poly(ethylene terephthalate) fibers using H2O2 as initiator
Authors: Hebeish A. , Shalaby S. E. , Bayazeed A. M.
Published: April 2003

The presence of poly(ethylene terephthalate) (PET) fibers during polymerization of methyl methacrylate (MMA) using H2O2 as initiator resulted in a substantial, constant increase in the weight of the fibers after repeated extraction with acetone. Fractional precipitation curves of the extracted PET—MMA polymerization product and a physical mixture of PET and PMMA were different, indicating that the interaction of MMA with PET involved grafting. The magnitude of the latter enhanced considerably by increasing H2O2 concentration up to 30 mequiv/L, then decreased by further increasing H2O2 concentration. There was also an optimal temperature (80°C) for grafting; below or above this temperature, lower grafting was obtained. Similarly, carrying out the polymerization reaction at different pH values revealed that pH7 constituted the optimal. On the other hand, grafting increased upon increase of the methyl methacrylate concentration within the range studied (8–20%). Incorporation of Cu2+ or Fe3+ ions in the polymerization medium caused a decrement in grafting, irrespective of the metallic ion concentrations. Using methylene chloride as a swelling agent for the fibers failed to enhance the susceptibility of the latter toward grafting. On the contrary, tetrachloroethane was quite promising in this regard. The homopolymer formed during grafting was also reported.
Synthesis of some vinyl derivatives of cellulose and their grafting copolymerization with styrene
Authors: Akelah A. , Sherrington D. C.
Published: April 2003

Some new vinyl derivatives of cellulose have been synthesized under anhydrous conditions using potassium cellulosate. The unsaturated groups were introduced by esterification with acryloyl chloride and by etherification with vinylbenzyl chloride or via 5‐chloromethylsalicylaldyhyde derivatives. Levels of cellulose substitution of from ∼10–75% of glucose residues were achieved. Polystyrene was readily grafted onto all the derivatives via solution polymerization in toluene, using azobisisobutyronitrile as a thermal initiator. Weight fractions of styrene of up to ∼0.4 were readily obtained.
Distribution of polymer deposition in glow discharge polymerization in a capacitively coupled system
Authors: Inagaki N. , Yasuda H.
Published: April 2003

The manner by which polymers created by plasma uniformly deposit onto substrates was sought. By rotating the substrate placed midway between electrodes, completely uniform distribution of polymer deposition was accomplished, and the deviation of the polymer deposition in a radius direction of the rotating substrate was within experimental errors. Materials of the substrate on which the polymer deposited had no influence on uiniformity of polymer deposition, but the electrical circuit of power source, i.e., grounding an electrode, markedly disturbed the uniformity. Thickness of polymers deposited on the substrate was linearly proportional to reaction time. Surface energies of deposited polymers prepared from methane, ethylene, and acetylene by plasma were independent of reaction time and were rather higher than those for conventionally polymerized polyolefines.
Radiation‐induced seeded copolymerization of tetrafluoroethylene with propylene. I. Effects of agitation and dose rate
Authors: Watanabe Hiromasa , Ito Masayuki , Okamoto Jiro , Machi Sueo
Published: April 2003

Seeded copolymerization of teterafluoroethylene with propylene by radiation was studied by semibatch experiment at a constant pressure of 25 kg/cm2, a temperature of 40°C, and at various dose rates and monomer compositions in polymer particles. The polymerization rate and polymer molecular weight are in the ranges of 5.6–58.7 g/h.L‐H2O and 4.6 × 104–1.6 × 105, respectively. The polymerization rate increases with agitation speed up to 300 rpm and slightly decreases above 500 rpm. The polymer molecular weight is the highest at 300 rpm. The polymerization rate and polymer molecular weight increase with tetrafluoroethylene fraction. At lower tetrafluoroethylene fraction, the polymerization rate is proportional to the 0.7–0.9 power of the dose rate and the polymer molecular weight is almost independent. The dose rate effects are explained by considering that first‐order termination by degradative chain transfer to propylene is predominant at a lower tetrafluoroethylene fraction. Decrease in the dose rate dependence of the polymerization rate and increase in that of the polymer molecular weight with the tetrafluoroethylene fraction are due to the increase in second‐order termination by recombination.
Polymeric systems for acoustic damping. III. Blends of poly(vinyl chloride), segmented poly(ether ester), and poly(methyl acrylate)
Authors: Hourston D. J. , Hughes I. D.
Published: April 2003

A solution blend of poly(vinyl chloride) and a segmented poly(ether ester) and blends containing these two polymers plus poly(methyl acrylate) were investigated by dynamic mechanical analysis and electron microscopy. The binary blend, which contained 75% by weight of the poly(ether ester), showed only one loss peak, but also evidence of some phase separation. It is believed that the polyether sequences of the poly(ether ester) are extensively mixed with poly(vinyl chloride). Poly(methyl acrylate) was added to spread the damping range and produce a material of potential use as an acoustic damper. It is evident from both electron microscopy and dynamic mechanical analysis that poly(methyl acrylate) is substantially incompatible in the other polymers.
Solvent diffusion in amorphous polymers
Authors: Ju S. T. , Liu H. T. , Duda J. L. , Vrentas J. S.
Published: April 2003

New diffusivity data are presented for solvent diffusion in poly(vinyl acetate), poly(methyl methacrylate), and polystyrene. These data are used to test the predictive and correlative capabilities of a recently proposed free‐volume theory of diffusion. Comparisons of data and theory showed that the proposed theory provided an accurate description of diffusion in concentrated polymer solutions.
Moisture absorption phenomenon in permeable fiber polymer composites
Authors: Rao R. M. V. G. K. , Balasubramanian N. , Chanda Manas
Published: April 2003

Studies were conducted on the moisture absorption characteristics of jute fiber composites based on polyester and epoxy resin systems, under constant humidity (ø) and ambient temperature (T) conditions. The initial slope of the moisture absorption curve (a direct measure of the composite diffusivity) increased with increased superficial fiber volume fraction (Vf), where as the time (tm'), needed to reach the equilibrium moisture absorption value showed a reversed trend. This behavior is just a reverse to that observed1 in case of composites with practically impermeable fibers (e.g., glass and graphite) in the same resin matrices. The theoretical expressions governing moisture diffusion phenomenon in impermeable fiber composites were modified and analyzed for the case of composites containing a permeable fiber. The experimental data obtained on the latter were then discussed in relation to the modified theory. The meaning of a correct fiber volume fraction (Vf,) as applicable to permeable fiber composites was defined.
Prediction of Flory–Huggins interaction parameters from intrinsic viscosities
Authors: Kok Chong Meng , Rudin Alfred
Published: April 2003

Previous articles from this laboratory have described a model for predicting the second virial coefficient of a polymer solution given the polymer molecular weight and its intrinsic viscosity in the particular solvent. The same theory is used in this report to calculate values of the Flory–Huggins interaction parameter χ. The method is different in that χ is obtained through manipulation of simulated exprimental data in exactly the same way as in an actual experiment. Agreement between estimated χ values and those obtained at infinite dilutions from membrane osmometry or light scattering is within 2%, on the average. The model accounts for the molecular weight dependence of χ.
Modeling of poly(ethylene terephthalate) reactors. II. A continuous transesterification process
Authors: Ravindranath K. , Mashelkar R. A.
Published: April 2003

A comprehensive mathematical model for a continuous transesterification process has been built so as to enable prediction of the influence of different process and operational variables on productivity and by‐product formation. The influence of temperatures and temperature profiles, of residence time and residence time distribution, and also of the number of reactors in series has been investigated. The modeling has been done as close to the industrial practice as possible. Important pragmatic implications from the point of view of operation of continuous transesterification are highlighted.
Morphology and mechanical properties of radiation‐polymerized urethane–acrylates. I. Pure oligomers
Authors: Wadhwa Lachhman H. , Walsh W. K.
Published: April 2003

The morphology of electron beam cured polyacrylo–urethane films based on polyethylene adipate and toluene diisocyanate was characterized to explain their mechanical properties. The polyacrylo–urethane films have a one‐phase morphology in which the hard urethane segments and the soft polyester segments are homogeneously mixed. The films obtained from 1000‐molecular‐weight oligomer are hard and somewhat brittle due to their one‐phase morphology in which hard glassy segments play a dominant role. The films obtained from 4600‐ and 6000‐molecular‐weight oligomers are soft and tough, once again due to their one‐phase morphology in which soft rubbery segments are more effective. The original crystalline structure of 6000‐molecular‐weight oligomer is retained in the precrystallized γ‐irradiated film, but electron‐beam‐irradiated films showed partial melting of the crystallites due to the heat of polymerization. The solid state polymerized films have a lower eleongation, a higher modulus, and a higher breaking strength due to their crystallinity.
Liquid‐chromatographic determination of rate constants for the cellulose‐dimethyloldihydroxyethyleneurea reaction
Authors: Beck Keith R. , Pasad Dilip M.
Published: April 2003

Rates of the MgCl2‐catalyzed reaction between cellulose and 4,5‐dihydroxy‐1,3‐bis(hydroxymethyl)‐2‐imidazolidinone were measured at 70, 90, and 110°C. The rate constants were determined by curing the resin for various times, extracting the unreacted resin, and determining its concentration by liquid chromatography. The energy of activation was calculated from the rate data. This work confirms the pseudo‐first‐order behavior of this reaction.
Crystallinity and heats of crystallization of cellulose: A microcalorimetric investigation
Authors: Dale Bruce E. , Tsao George T.
Published: April 2003

We have used a sensitive adiabatic microcalorimeter to study cellulose dissolution in its metal complex solvents cadoxen and ferric sodium tartrate (FeTNa). Heats of crystallization of cellulose I and II have thereby been estimated and range from −4.07 kcal/mol to −5.43 kcal/mol. A solvent‐dependent heat of reaction factor has been invoked to explain differences in the heats of crystallization obtained by the two solvents. Conversion of cellulose I to cellulose II is an exothermic process with an enthalpy change of about −6.0 cal/g cellulose. The crystallinities of various cellulose samples have been determined using these thermodynamic data and have been found to be generally consistent with values given by more traditional means.
Modelling of poly(ethylene terephthalate) reactors. III. A semibatch prepolymerization process
Authors: Ravindranath K. , Mashelkar R. A.
Published: April 2003

A mathematical modelling of a semibatch prepolymerization process has been undertaken. Prepolymerization conducted at constant temperature and pressure and with a predetermined variation in temperature and pressure has been studied. Influence of DMT and TPA addition during prepolymerization has also been examined. The focus has been on investigation of the influence of processing and operational variables on productivity and side product formation, which controls product quality. The results of this investigation (which are applicable only up to DP ≃ to 30) are borne out by the limited experimental data available in the literature. Important pragmatic implications of the results of the work in terms of design and operation of prepolymerization reactors have been emphasized.
Orientation development in the tubular film extrusion of polypropylene
Authors: Shimomura Yasushi , Spruiell Joseph E. , White James L.
Published: April 2003

A basic study of orientation development in the tubular film extrusion of polypropylene is reported. WAXS and birefringence measurements were carried out on films prepared under conditions of known blowup ratio B, drawdown νL/νO, machine direction tension, and bubble pressure. Pole figures were constructed and biaxial orientation factors determined. The use of an orientation factor triangle diagram was found to be a useful method of representing the variation of orientation with processing conditions. The variation in orientation with processing parameters for polypropylene was found to have similar behavior to that previously found for polyethylene.
Diffusion of deterrents into a nitrocellulose‐based small arms propellant. The effect of deterrent structure and solvent
Authors: Fong C. W. , Cooke C.
Published: April 2003

The depth of penetration of five urea‐based deterrents and of dinitrotoluene into an extruded monoperforated nitrocellulose propellant has been studied. The depth of penetration is directly proportional to the concentration of the deterrent solution. Structural variation of the urea‐based deterrents and increasing the water content of the alcoholic deterrent solutions have significant effects on the depth of deterrent penetration. Dinitrotoluene penetrates more rapidly than the urea deterrents in all solvents studied. The results are consistent with a diffusion with interaction mechanism. It is suggested that some previous evidence for such a mechanism was not definitive.
Calibration of size‐exclusion chromatography columns with polydisperse polymer standards. II. Applications
Authors: Kubín M.
Published: April 2003

New methods for calibrating SEC columns by means of polydisperse polymer samples with known Mn and Mw have been tested with computer‐generated chromatograms and with experimental data of high‐performance SEC. Calculations with the artificial chromatograms show that accurate calibration dependences can be recovered even when polymers with broad and/or bimodal molecular weight distributions are used as standards. Polystyrene calibration calculated by the proposed method from chromatograms of five polydisperse polystyrenes follows closely the curve obtained in a conventional manner from nine narrow polystyrene standards. The dependence log M vs. ν for PMMA determined from chromatograms of six PMMA samples with moderately broad molecular weight distributions agrees well with the curve obtained by shifting the dependence for polystyrene using the universal calibration concept. The new method is particularly useful when SEC columns are to be calibrated for dextrans in water, where only a few standards having a rather broad molecular weight distribution are available, and can considerably improve the accuracy of molecular weight determination by SEC.
Orientation in acrylonitrile copolymers
Authors: Kumar Satish , Stein R. S.
Published: April 2003

Rubber modified and unmodified poly(acrylonitrile/methyl acrylate) (75/25) copolymers [(Barex® resins) (Barex® is a registered trademark of Vistron Corporation, a subsidiary of The Standard Oil Company, Ohio)] were stretched at varying strain rates at different temperatures. Molecular orientation of the stretched samples at different extension ratios was determined using birefringence, the X‐ray orientation factor, and infrared dichroism. The birefringence of rubber modified copolymers, which were prepared by graft copolymerization of the poly(acrylonitrile/methyl acrylate) copolymer with 10 parts (by weight) of a poly(butadiene/acrylonitrile) rubber, is found to be appreciably different as compared with the birefringence of unmodified poly(acrylonitrile/methyl acrylate) copolymer. The possible reasons for this difference are discussed. The orientation measured from the three techniques is compared, and the effects of temperature of stretching and of strain to are discussed. The maximum values of the birefringence of these two copolymers and that of the polyacrylonitrile have been estimated. Transition moment angles for CH2 and CN stretching bonds are obtained. From the birefringence data at various temperatures and strain rates, the activation energies of these two copolymers have been obtained.
Flow properties of various irradiated resins of PTFE (teflon)
Authors: Fisher W. Keith , Corelli J. C.
Published: April 2003

Changes in the melt viscosity of PTFE exposed to various radiation doses in air were measured using a capillary rheometer. The melt viscosity decreases dramatically after exposure to 2.5 MRad, but between 2.5 and 5 MRad there is an increase in viscosity which is attributed to the formation of branches and crosslinks. Above 5 MRad, the melt viscosity decreases with dose. Plots of log apparent melt viscosity vs. log apparent shear rate are given for PTFE exposed to various radiation doses. The data in each of these plots can be fit by a straight line (power law), and changes in the slopes of these lines are interpreted to indicate changes in the molecular weight distribution. It is postulated that the observed decrease in the slopes of these lines after irradiation is caused by a narrowing of the molecular weight distribution because of the decrease in the number of molecules at the high molecular weight end of the distribution. The melt viscosity of a PTFE sample irradiated to a given dose was less for a sample of low preirradiation crystallinity than for an otherwise identical sample of higher crystallinity. This crystallinity dependence of viscosity is related to differences in oxygen diffusion properties of crystalline and amorphous PTFE.
Effect of sodium lauryl sulfate on the polymerization of acrylonitrile
Authors: Patel N. , Mohammed I. , Das B. N. , Sinha B. K.
Published: April 2003

Micellar catalyzed polymerization of acrylonitrile using ceric(IV)–glycerol redox system in aqueous sulfuric acid solution in the presence of sodium lauryl sulfate (NaLS) has been studied. The polymerization experiments were conducted between 15°C and 25°C, under conditions where no oxidation of sodium lauryl sulfate by ceric ion would we expected. The rate of polymerization (Rp) increases with increasing concentration of NaLS. The rate of monomer (AN) disappearance was proportional to [AN]1.5 and [glycerol]0.5, but, however, Rp changes in a nonlinear manner with increase in Ce(IV) concentration in the presence of the surfactant. The rate of Ce(IV) disappearance was not proportional to its original concentration. The chain length of the polymer could not be determined viscometrically, as the polymer obtained in presence of NaLS was insoluble in organic solvents. The activation energy of this polymerization process was calculated by conducting the experiment at different temperatures. The infrared spectra of the polymers in the presence and absence of surfactant have also been examined.
Plasticizer transfer from plasticized PVC into ethanol–water mixtures
Authors: Messadi D. , Vergnaud J. M.
Published: April 2003

The transfer of plasticizer from compression‐molded sheets of plasticized poly(vinyl chloride) into ethanol–water mixtures was studied over the temperature range of 30–55°C. A simultaneous diffusion occurred for ethanol and water into polymer and for dioctylphthalate plasticizer from polymer into liquid. The concentration of ethanol transferred into the polymer was found to increase, rise to a maximum, and then decrease. Equations of diffusion in unsteady state were found to correlate well with experiments on plasticizer transfer, over the plasticizer concentration range of 25–50 wt %. Stirring, temperature, water concentration in ethanolic solutions, and plasticizer concentration were found to play important roles.
Investigation of thermal degradation of polystyrene by differential scanning calorimetry
Authors: Toh H. K. , Funt B. L.
Published: April 2003

Thermal degradation of polystyrene was performed in a differential scanning calorimeter under nitrogen atmosphere, and the glass transition temperature was measured continuously. From random chain scission kinetics and Tg‐molecular weight relationships, the rate constant for random scission was obtained. The rate constant was found to undergo a drastic change at a critical molecular weight (∽45,000), which corresponds to a similar observation in relaxation studies. A viscosity‐dependent mechanism for radical chain end termination is thus suggested.
Characterization of the imidization of the aromatic polyimide LARC‐160
Authors: Delos S. E. , Schellenberg R. K. , Smedley J. E. , Kranbuehl D. E.
Published: April 2003

The polyimide resin LARC‐160 was prepared from diethyl‐3,3′,4,4′‐benzophenone tetracarboxylate (BTDE), ethyl‐5‐norbornene‐2,3‐dicarboxylate (NE), and Jeffamine AP‐22. The imidization reactions of NE and BTDE were studied by HPLC, 13C‐NMR, and IR. NE imidizes slowly at 12°C; BTDE imidizes when the resin is heated above 100°C. Both imidization reactions proceed directly to the imide. Neither amic acid is present in significant quantities at any stage of the imidization reactions. The monomer mixture has been stored at 12°C for periods up to 14 months. The effects of resin aging at this temperature on the chemical composition of the resin monomer mixture and the imidized polymer formed on curing were investigated. Aging the resin monomer mixture has the effect of partially advancing the imidization reaction. Aging also results in the formation of slightly higher‐molecular‐weight polyimide chains after curing of the resin at 140 and 180°C. Bisnadimide (BNI) is observed as a major reaction product, regardless of resin age.
Glow discharge polymerization of trimethylvinylsilane and tetramethylsilane
Authors: Inagaki N. , Taki M.
Published: April 2003

Glow discharge polymerizations of trimethylvinylsilane (TMVS) and tetramethylsilane (TMS) were compared. Vinyl groups in TMVS slightly contribute the polymer‐formation process only when glow discharge polymerization was performed at the W/FM parameter less than 500 MJ/kg. Elemental compositions of the polymers prepared from TMVS, which are rich in carbon content, shows strong dependence on operational conditions, the W/FM parameter; but the polymers from TMVS consist of the almost same chemical structures as those from TMS. Slight differences between the starting materials in chemical structure does not reflect on bulk properties of the formed polymers but on surface properties such as surface energy and adhesion.
Processable heat‐resistant polymers. VII. Synthesis and characterization of polyamideimide from N‐(p‐carboxyphenyl) trimellitimide and p,p′‐di(aminocyclohexyl) methane
Authors: Maiti Sukumar , Ray Atanu
Published: April 2003

Polyamideimides were prepared either directly from N‐(p‐carboxyphenyl)trimellitimide and p,p′‐di(aminocyclohexy)methane (PACM‐20) by low temperature (<5°C) polycondensation in presence of thionyl chloride or by reacting the diacid chloride of N‐(p‐carboxyphenyl)trimellitimide and PACM‐20 at 30–70°C. The polymers were characterized by nitrogen analysis and IR spectra. The polymers are soluble in highly polar solvents such as DMF, DMAC, NMP, and m‐cresol. The solubility parameter was calculated from the Small's group contribution, which agrees well with the experimental value. The solution viscosity of the polymer is fairly stable against ageing. The Tg of the polymer calculated from the DTA curve is 270°C or even higher. Thermal analyses indicated that the polymer is fairly stable and only 5–6% weight loss occurs up to 350°C or 380°C. Dielectric constant, dielectric loss, and electrical conductivity of the polymer were also studied.
Effects of mineral oil on the rheological behavior of polystyrene melts
Authors: Bersted B. H.
Published: April 2003

The effects of mineral oil on the small strain rheological functions of polystyrene are shown to be simply related to the oil content and the rheological behavior for the neat material. Reduced variables, which are analogous to the effects of temperature, are found to successfully reduce the data for all levels of oil. The use and form of these reduced variables are shown to be predicted by the model of Bersted, which relates the rheological functions directly to the molecular weight distribution. The effects of the oil are argued to suggest that the mineral oil acts as a plasticizer for polystyrene.
Crystallization kinetics of poly(vinyl alcohol)
Authors: Peppas Nikolaos A. , Hansen Paula J.
Published: April 2003

The kinetics of crystallization of solvent‐free poly(vinyl alcohol) were investigated by isothermal crystallization at temperatures of 142–192°C, for up to 18 min. The crystallization isotherms were analyzed by Avrami's theory. The magnitude of the exponent n was almost constant (0.67–0.71) in the range of 142–182°C, increasing to 1.53 for crystallization at 192°C. Based on thermodynamic analysis of the isotherms and the crystallite growth rate, there are strong indications that crystallization of PVA is one‐dimensional. In the absence of water or other swelling agents, kinetic hindrances predominate due to the interactions of the hydroxyl groups. Therefore, the maximum attainable weight fraction of crystallized PVA is considerably lower than that of hydrated PVA samples. Additional parameters affecting the growth rate are discussed, including the degree of undercooling and the average chain length, as controlled by crosslinking.
Polymerization of butadiene with Co(acac)3–(i‐Bu)3Al–H2O catalyst
Authors: Yang W. L. , Hsu C. C.
Published: April 2003

The polymerization of butadiene in toluene using Co(acac)3–(i‐Bu)3Al–H2O catalyst system was studied. Presented are the effects of the addition order, aging time, and composition of catalysts on rates, polymer microstructure, and molecular weights. The polymerization was found to be initiated by the Co(acac)3‐hydrolized aluminum alkyl complex. The chain propagation proceeds according to a first‐order reaction with respect to monomer and active species and is a strong function of Al/H2O with an optimum ratio of 1.0, but independent of Al/Co. The nature of polymerization seems to change as Al/H2O increases from less than 1 to greater than 1. Transfer reaction is significant. From the kinetic data it was found that the termination reaction is most likely to be by combination.
On the curing kinetics of unsaturated polyesters with styrene
Authors: Cuadrado T. R. , Borrajo J. , Williams R. J. J. , Clara F. M.
Published: April 2003

The curing kinetics of a general purpose unsaturated polyester (UP) with styrene was studied by differential scanning calorimetry and dielectric capacitance measurements. Benzoyl peroxide was used as initiator. Results showed that there is a complete change in the phenomenological kinetics, in different temperature ranges. At low temperatures (70–90°C), the rate went through a maximum and then showed a first‐order decay. At high temperatures (100–160°C) a second‐order kinetics was suitable for all the conversion range. At T > 160°C another mechanism took place when the initiator amount was less than a critical value. From the changes in the dielectric capacitance it was inferred that the conversion rate of UP unsaturations followed a first‐order decay after a certain conversion, with an activation energy close to values reported for diffusion of UP radicals. Possible free radical mechanisms accounting for experimental observations are discussed.
Studies on moisture sorption in coir fibers (cocos nucifera L)
Authors: Kulkarni A. G. , Cheriyan K. A. , Satyanarayana K. G. , Rohatgi P. K.
Published: April 2003

Moisture desorption characteristics in coir fibers have been studied at several temperatures (53°C, 68°C, 86°C, and 105°C) as a function of time. Moisture absorption at room temperature after heating to 53°C, 68°C, 86°C, and 105°C are also reported. The results indicate that the relation between percentage moisture loss (A) (moisture loss is the ratio of the difference between initial moisture and final moisture to initial moisture) and temperature (T°K) is of the type A = Aoe−B/T in the range of intervals studied. The constants Ao and B are dependent on time, and they decrease with time. The fraction moisture loss/gain (w) is related to time (t) by the equation w = m/t + b0 at all temperatures investigated. The constant m decreases with temperature while b0 increases with temperature. The equilibrium moisture content (the condition reached by the sample when it no longer takes up moisture from or gives up moisture to the surrounding atmosphere) increases with increase in relative pressure and decrease in temperatures. As the moisture content in the fiber increases, the tensile strength (tenacity) decreases and the % elongation increases. The observed results are explained on the basis of structural rearrangement on heating/cooling of lignocellulosic material.
Synthesis and characterization of some new chelating amphoteric ion‐exchange resins
Authors: Kapadia R. N. , Vyas M. V.
Published: April 2003

Some new chelating amphoteric ion exchange resins have been synthesized by condensing catechol, 8‐hydroxyquinoline, hydroquinone, salicyclic acid, sulfosalicyclic acid, 3‐hydroxy‐2‐naphthoic acid, p‐hydroxybenzoic acid, β‐resorcylic acid, and anthranilic acid with epichlorohydrin employing diethylenetriamine as a cross linking agent in a nonaqueous medium, toluene. These resins are characterized by their physicochemical properties such as moisture retention ability, true density, apparent density, void fraction, concentration of ionogenic groups, volume capacity, total ion exchange capacity, copper exchange capacity, rate of ion exchange, pH titration curves, apparent pKa and pKb values, isoionic point values, oxidative degradation, thermal stability, the effect of temperature of equilibration on the capacity of the resin, swelling behavior in various solvents, and absorption specificity towards certain bivalent metal cations in ammonium acetate–dimethylformamide media.
The structural interpretation of DSC curve specificity of poly(caprolactam) fibers. I. The specificity of the element of the curve observed in the temperature range ∼40–65°C
Authors: Jeziorny A.
Published: April 2003

The index τ determined from the thermogram was correlated with the selected parameters of the amorphous material structure of polycaprolactam fibers. The investigated structural parameters were as follows: (a) the orientation factor determined by infrared absorption spectroscopy, based on the absorption band at 1130 cm−1; (b) the fraction of taut tie molecules calculated on the basis of the determined axial elastic modulus and volume crystallinity of the fiber. The occurrence of straight‐line relations between the values of the index τ and the values of the investigated structural parameters was found out. The conclusion was formulated that the specificity of the investigated element of the DSC curve reflects the entropy transition rate. That transition, stimulated by fiber heating during the DSC experiment, consists of the increase of the disorder of taut tie molecules. Probably, the rate of that transition changes relatively to the magnitude of the stress affecting taut tie molecules.
Anodic synthesis of sulfur‐bridged polyaniline coatings onto Fe sheets
Authors: Mengoli Giuliano , Musiani Marco M. , Pelli Beatrice , Vecchi Enrico
Published: April 2003

Sulfur‐bridged polyaniline coatings are obtained onto Fe anodes by electrolyzing a basic solution of one aniline and ammonium sulfide. Their sulfur content ranges from 7% to 17%, depending on the substituents on aniline. Variously substituted anilines may be polymerized in this way and coating pollution by azobenzene formed in a side reaction is almost completely avoided. Sulfur probably enters the polymer chains through a free radical mechanism. HS• intermediates being formed by both homogeneous and anodic oxidation of HS− anions. Coatings from N‐allylaniline, being thermally curable, show satisfactory physical properties.
Effect of copolymerization with methacrylonitrile on the dielectric relaxation of polyacrylonitrile
Authors: Gupta A. K. , Singhal R. P. , Bajaj P. , Agarwal V. K.
Published: April 2003

Dielectric relaxation in the glass transition region of polyacrylonitrile (PAN), polymethacrylonitrile (PMAN), and their random copolymers containing 6–46 wt % MAN has been studied in the frequency range 102–105 Hz and temperature range 40–160°C. Changes in the dielectric constant increment, relaxation temperature, and the loss peak amplitude with changing MAN content in the copolymers were observed. Dielectric constant increment and loss peak amplitude showed maxima around 6–12 wt % MAN content while the relaxation temperature increased continuously over the entire range. The results are discussed in terms of the possible structural differences arising from the effect of the introduction of MAN units on the dipolar interactions between the nitrile groups.
Hot rolling and quench rolling of ultrahigh molecular weight polyethylene
Authors: Kaito Akira , Nakayama Kazuo , Kanetsuna Hisaaki
Published: April 2003

The mechanical properties, the crystal orientation, and the microstructure of hot rolled and quench rolled ultrahigh molecular weight polyethylene (UHMW‐PE) were investigated. The tensile strength of hot rolled and quench rolled UHMW‐PE sheets increased with increasing draw ratio. The crystallographic axes a, b, and c of the rolled sheets tended to be oriented to the normal direction (ND), the traverse direction (TD), and the rolling direction (RD), respectively. The small‐angle X‐ray scattering patterns with incident X‐ray beam parallel to TD suggested the presence of inclined lamellar structure in the RD–ND plane. At the initial stage of rolling, partial breakup of crystallites along the (100) plane was observed. The lamellar structure is deformed by the slippage mechanism along the (100) plane in the chain direction.
Syntheses of photocrosslinkable polymer from modified poly(methyl vinyl ketone)
Authors: Kinoshita Akihiro , Namariyama Yoichi
Published: April 2003

Photocrosslinkable polymer is prepared from amorphous poly(methyl vinyl ketone) (A‐PMVK) obtained by anionic polymerization of methyl vinyl ketone. The reaction of A‐PMVK with cinnamoyl chloride proceeds in pyridine at 50°C. The photosensitivity of the polymer obtained is measured by infrared and Ultraviolet photometry. The polymer is of a crosslinkable type and forms cyclobutane linkage by ultraviolet irradiation. The polymer is coated on a lithographic aluminum plate and exposed to arc and high‐pressure mercury lamps. Development is with benzene, and standard inking by lithography is applied. The imaging area on the plate is stable and harder than poly(vinyl cinnamate), due to intra‐ and intermolecular cyclization of the main chain. Many good reproductions are produced in the lithographic proofing machine. The photosensitive polymer obtained by A‐PMVK is very useful in relief plates requiring etching.
Determination of the birefringence of an ideal polyester fiber (PET) with regard to the intermolecular interactions
Authors: WŁochowicz Andrzej , Rabiej Stanisław , Janicki Jarosław
Published: April 2003

Method of birefringence determination for an ideal polyester fiber has been described with regard to the interactions of surrounding macromolecules, Δn = 0.2360. Obtained results have been discussed in view of information given in the literature.
Water absorption in acrylic latex films
Authors: Šňupárek J. , Bidman A. , Hanuš J. , Hájková B.
Published: April 2003

Water absorption in acrylic latex films was investigated. Films from post‐stabilized latices exhibited low water uptake during a long‐time immersion in water; this was caused by easier extraction of water soluble materials into water. The extraction of secondary emulsifiers was estimated by liquid chromatography; the structure of film surfaces was investigated by electron microscopy.
The study on radiation grafting of acrylic acid onto fluorine‐containing polymers. IV. Properties of membrane obtained by preirradiation grafting onto poly(tetrafluoroethylene–hexafluoropropylene)
Authors: Hegazy El‐Sayed A. , Ishigaki Isao , Rabie Abdelgawad , Dessouki Ahmed M. , Okamoto Jiro
Published: April 2003

Some properties of the membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–hexafluoropropylene) (FEP) film have been investigated. Swelling behavior, dimensional change by grafting, electric conductivity, and mechanical properties of the grafted films were found to depend largely on the degree of grafting and to increase as the grafting proceeds. These properties were also found to be independent of the preparation conditions such as irradiation dose, grafting temperature, film thickness, and monomer concentration lower than 60 wt %. The electric conductivity of the membranes prepared at lower monomer concentration (lower than 60 wt %) is higher than that prepared at 80 wt % acrylic acid concentration. X‐ray microscopy of the grafted film revealed that the grafting proceeds from both surfaces of the film to the direction of center to give finally homogeneous grafting through the whole bulk of film. At lower monomer concentration the homogeneous grafting was achieved at a degree of grafting around 18%, while at 80 wt % acrylic acid it was achieved at a degree of grafting higher than 70%. The homogeneously grafted membranes show good electrochemical and mechanical properties which make them acceptable for practical uses as cation‐exchange membranes.
The influence of particle size and surface coating of calcium carbonate on the rheological properties of its suspensions in molten polystyrene
Authors: Suetsugu Yoshiyuki , White James L.
Published: April 2003

The rheological properties of polystyrene melts filled with 30 vol % of CaCO3 particles of varying particle size are described. The influence of surface coating the particles with stearic acid is considered. Generally, the compounds with the uncoated particles exhibit viscosities which increase at ever greater rates as the shear rates decrease. It appears that these compounds exhibit yield values. Elongational flow data also suggest the existence of yield values. Difficulties exist in measurement of normal stresses in compounds with sizeable yield values. The principal normal stress difference at fixed shear stress of the PS/CaCO3 compounds is lower than that of the PS melt. The magnitude of viscosity increases and yield values increase with decreasing particle size. Coating of particles with stearic acid results in major viscosity reductions and decreases in apparent yield values. The surface coating is most effective with the smallest particles. It presumably reduces interaction between particles and the extent of aggregation.
Tensile properties of fiberglass‐reinforced polyester foams
Authors: Masi P. , Nicolais L. , Mazzola M. , Snial  , Narkis M.
Published: April 2003

High‐density structural foams and their fiberglass‐reinforced versions have been characterized in tension, and the results were analyzed. The tensile modulus and strength of the nonreinforced foams can be described by the modified Kerner equation and a modified Nicolais–Narkis equation, respectively. The modulus of the reinforced foams can be predicted by using the concepts of the quasi‐isotropic laminate theory. The temperature sensitivity of the reinforced foams is markedly reduced and the impact failure in a falling ball test is localized, and energy absorption is accomplished by the formation of numerous small cracks. Fiber reinforcement of foams improves also the heat sag resistance and reduces the coefficient of thermal expansion.
Glass transitions of poly(bisphenol‐A carbonate)/ultraviolet light stabilizer blends by DSC and TOA
Authors: Shultz A. R. , Young A. L. , Alessi S. , Stewart M.
Published: April 2003

Glass transition temperatures are reported for poly(bisphenol‐A‐carbonate) plasticized by 0–12 wt % of the ultraviolet light stabilizers 2‐hydroxy‐4‐methoxy‐benzophenone, 2‐hydroxy‐4‐n‐octooxy‐benzophenone, and 2‐hydroxy‐4‐dodecyloxy‐benzophenone. Differential scanning calorimetry (DSC) and thermooptical analysis (TOA) were employed. The glass transition temperatures increased somewhat with shelf time for the room temperature air‐dried 1‐mil films drawn from methylene chloride solutions. A Bierbaum scratch hardness of 8.8 kg·mm−2 was observed for a 10‐mil poly(bisphenol‐A carbonate) film. The effect of load applied to the diamond point (Bierbaum scratch technique) on the shape of TOA transmitted light intensity vs. temperature curves for the resultant scratches was examined. Although the curve shapes are greatly affected, the characteristic TOA temperatures derived therefrom remain essentially unchanged. The glass transition regions are not quite as broad for these polymer/plasticizer blends as they are for compatible polymer/polymer blends. TTOA, the temperature at which birefringence disappears in the scratched films, is found identical to Tf (DSC), the temperature at which the specific heat transition is completed.
Proton spin–lattice and spin–spin relaxation times in isotactic polypropylene. II. Effects of stretching ratio and temperature
Authors: Tanaka Hiroshi
Published: April 2003

Proton spin–lattice, T1, and spin–spin, T2, relaxation times of uniaxially stretched polypropylene film were measured at 40°C using a wide line pulse spectrometer operating at 19.8 MHz. T1l, the longer T1, increases almost linearly with increasing stretching ratio, and T2a, T2 of the amorphous region, decreases gradually as the stretching ratio is increased. These results can be interpreted in terms of the increased constraints to molecular motion in the amorphous region. The fraction of the rigid protons in the sample, Fc, increases with increasing stretching ratio, while the crystallinity calculated from the density, Xd, does not change largely. The difference between Fc and Xd, therefore, increases as the stretching ratio is increased. This indicates that the physical structure of the highly stretched sample is far from the ideal two‐phase model. The influence of the stretching temperature was also investigated. There are only slight increases in T1l and in Fc for the samples stretched in a temperature range from 80°C to 150°C, whereas the considerable increase in T2a occurs. The most notable change introduced at a high temperature stretching is the increase in the chain mobility in the amorphous region.
Highly deacetylated chitosan and its properties
Authors: Mima Seiichi , Miya Masaru , Iwamoto Reikichi , Yoshikawa Susumu
Published: April 2003

A preparative method has been established for obtaining chitosan products which have a desired degree of deacetylation of up to virtually 100%. Effective deacetylation was attained by intermitently washing the intermediate product in water two or more times during the alkali treatment. The weight average molecular weight (M̄w) of the product, which was measured by gel permeation liquid chromatography, was about 5 × 105 at the highest deacetylation of nearly 100%, and the degradation of the molecular chain was not so significant. Tensile strength of the wet film increased markedly with increasing degree of deacetylation, while the dry film did not show a corresponding significant increase of the tensile strength. In the infrared spectra of chitosan film new sharp bands appeared especially at the high degree of deacetylation. This was attributed to increased “crystallization” brought about by high deacetylation.
Thermal and biological properties of tin‐modified cellulosic material derived from cotton
Authors: Carraher Charles E. , Burt W. R. , Giron David J. , Schroeder Jack A. , Taylor Michael L. , Molloy H. Michael , Tiernan Thomas O.
Published: April 2003

Thermal and biological properties of tin‐modified cellulose derived from cotton are described. The inception temperature of degradation for tin‐modified cellulosic products is inferior to that of cotton itself, but the heats of degradation in air are less than that of cotton consistent with the modified products being superior in this respect. Degradation of the modified materials in helium as monitored by coupled thermogravimetric analysis–mass spectroscopy shows that degradation occurs through a series of complex steps with the evolution of products characteristic of both the tin‐containing and cellulose materials. The tin‐modified cellulose was tested against five fungi using disk and protein assays. The fungi tested are typical and widespread, and these tests provide a good indication of the applicability of such products as retarders of fungi‐related rot and mildew. Most of the tested samples showed good inhibition of the tested fungi.
Deformation and failure of polymeric matrices under swelling conditions
Authors: Cohn Daniel , Marom Gad
Published: April 2003

Polymers in which the diffusion mechanism was characterized by a sharp advancing boundary between the swollen shell and the core showed a highly anisotropic swelling response. The anisotropy of the swelling strains was caused by the mechanical constraints exerted mutually by the two regions of the specimen. The swelling stresses developing during the process eventually led to fracture of the polymer specimen. An analytical model which explained the modes of failure of the polymer under the swelling stresses was developed. The proposed approach was based on the general analogy existing between the studied swollen specimens and composite materials. A model for the prediction of the anisotropic hygroelastic response of the swollen systems was also proposed.
Stress–relaxattion of natural rubber under compression—depenndence on oxygen concentration
Authors: Stenberg B. , Dickman O.
Published: April 2003

The compression–relaxation was studied for unfilled TMTD‐vulcanized natural rubber cylinders (height = diameter = 20mm). The samples have been treated prior to compression in different oxygen media from an inert medium to pure oxygen at 2.0 MPa. Activation energies were calculated from compression–relaxation measurements made at different temperatures, and from these results conclusions were drawn concerning the diffusion control of the relaxation.
Comparison of polystyrene, poly(styrene/acrylonitrile), high‐impact polystryrene, and poly(acrylonitrile/butadiene/styrene) with respect to tensile and impact properties
Authors: Yokouchi Mitsuru , Seto Shinichi , Kobayashi Yasuji
Published: April 2003

The tensile behaviors of polystyrene (PS), poly(styrene/acrylonitrile) (SAN), high‐impact polystyrene (HIPS), and poly(acrylonitrile/butadiene/styrene) (ABS) were examined systematically in the wide range of strain rate, 1.7 × 10−4–13.1 m/s. When glassy and brittle PS was a criterion, the incorporation of a polar group (SAN) only strengthened the hardness, and the fracture mode was the same as for PS. The introduction of dispersed rubber particles (HIPS) weakened the hardness a little but offered a new deformation mechanism, i.e., microcrazing (whitening), and contributed to the improvement of impact strength. In the heterogeneous system, the enhancement of matrix strength [e.g., preorientation or blending with poly(phenylene oxide) for HIPS] makes possible another deformation mechanism, i.e., shear band formation (cold drawing), which is superior to microcrazing for achieving higher impact strength. ABS, which incorporates concurrently two factors (polar group to matrix phase and dispersed rubber particles), can be regarded as an enhancement of the matrix strength of HIPS. In spite of the remarkable magnitude of its impact strength compared with that of the other three polymers, the deformation mechanism of ABS was limited to microcrazing. This indicated that only the introduction of a polar group (as nitrile group) could not strengthen the matrix as much as preorientation or blending with poly(phenylene oxide).