bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of heat setting on the structure and mechanical properties of poly(ethylene terephthalate) fiber. I. Structural changes
Authors: Gupta V. B. , Kumar Satish 
Published: April 2003

AbstractWe report structural changes in commercial multifilament poly(ethylene terephthalate) (PET) yarn when it is heat set in silicone oil over a range of temperatures between 100 and 220°C for times ranging from 1 min to 1 hr, while the yarn was (1) free to relax, and (2) held taut at constant length. In one case, viz., a sample heat treated for 1 hr, the cooling time was also varied to study the effect of rate of cooling. The free‐annealed and taut‐annealed samples showed considerable differences. The predominant role of the temperature of heat setting on structure is discussed in detail. There are considerable changes in the amount and orientation of the amorphous phase, and these will be shown to have important influence on mechanical properties in subsequent reports.
Mechanical properties and superstructure of high‐modulus and high‐strength PET fiber prepared by zone annealing
Authors: Kunugi Toshio , Suzuki Akihiro , Hashimoto Minoru 
Published: April 2003

AbstractThe relationships between mechanical properties and superstructure of the poly(ethylene terephthalate) fiber prepared by a new annealing method called zone annealing method were investigated. The effectiveness of zone annealing was compared with three other annealing methods, namely, annealing under release, annealing at constant length, and annealing under tension. The very high modulus and strength of the zone‐annealed fiber were directly attributed to the large number of tie molecules connecting the crystallites and to the high orientation of the amorphous region.
Some theoretical aspects of bromine‐containing triazine flame retardants
Authors: Chance Leon H. 
Published: April 2003

AbstractWe studied flame retardancy of cotton fabric treated with five diaminotriazines containing bromine—three compounds with the bromine on aliphatic groups and two with the bromine on phenyl groups. Flame retardancy, as measured by oxygen index and FF3‐71 flammability standards, was better on the fabrics containing aliphatic bromine than on the fabrics containing aromatic bromine. Thermogravimetric analyses (TGA) and differential thermogravimetric analyses (DTG) were obtained on the fabrics, results of which supported the theory that HBr liberated during burning lowers the ignition temperature and decomposition point of the cellulose causing a reduction in flammable gases and an increase in residual char. Since CH and CBr bond strengths are stronger on aromatic groups than on aliphatic groups, our results agree with the theory that flame retardancy increases as the CBr bond strength decreases. In other words, since bromine inhibits oxidation reactions in the gas phases, the heat evolved is expected to become less as the CBr bond strength decreases.
Diffusion and induced crystallization in polycarbonate
Authors: Ware Robert A. , Tirtowidjojo Steven , Cohen Claude 
Published: April 2003

AbstractThe study of the effect of thickness on the mass uptake is shown to be quite helpful in the understanding of the complexities of polymer/organic penetrant sorption behavior. Isothermal diffusion results for methanol, acetone, and carbon tetrachloride in polycarbonate plates and films of various thicknesses ranging from 12 mils (0.030 cm) to 1/4 in. (0.633 cm) are presented. The diffusion is purely Fickian only in the case of methanol, which is a poor solvent for polycarbonate and has a low level of saturation in it (0.06 g/g). Methanol does not lead to a detectable swelling or any appreciable crystallization of the polymer during the diffusion process. Acetone and carbon tetrachloride are much better solvents and lead to much higher saturation levels; they crystallize polycarbonate, and their mass uptake is anomalous. The diffusion of carbon tetrachloride exhibits initially a case II diffusion behavior followed for thicker plates by an intermediate behavior between case II and Fickian diffusion. The anomalous diffusion in the case of acetone appears to be associated primarily with surface effects.
H2O2‐induced graft polymerization of acrylic acid on poly(ethylene terephthalate) fibers
Authors: Hebeish A. , Shalaby S. E. , Bayazeed A. M. 
Published: April 2003

AbstractGraft polymerization of acrylic acid to poly(ethylene terephthalate) fibers using H2O2 as initiator was only possible in benzyl alcohol as reaction medium. The effect of initiator and monomer concentrations, reaction time, and temperature as well as addition of metallic salts to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing H2O2 concentrations up to 100 mequiv/L and then decreased upon further increase in initiator concentration. The same held true for acrylic acid concentration of up to 10%, but above this concentration grafting leveled off. Raising the polymerization temperature from 85 to 115°C favored grafting at lower H2O2concentration. The reverse was the case at higher H2O2 concentration (more than 25 mequiv/L). Addition of copper sulfate to the polymerization medium decreased the rate of grafting, and no leveling off of grafting could be achieved even after 5 h. The ferrous ammonium sulfate functioned similarly but to lesser degree, and leveling off of grafting occurred after 4 h. This contrasted with grafting in the absence of metallic salts where grafting leveled off after 1 h. Action of initial graft formation as diffusion barrier is believed to account for this.
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

AbstractThe 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

AbstractSome 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

AbstractThe 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

AbstractSeeded 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

AbstractA 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

AbstractNew 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

AbstractStudies 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

AbstractPrevious 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

AbstractA 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

AbstractThe 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

AbstractRates 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

AbstractWe 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractNew 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

AbstractRubber 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

AbstractChanges 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.