bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase equilibria and fractionation of linear homopolymers in solution: A thermodynamic numerical interpretation
Authors: Terán C. Chuquilín , Macchi E. M. , Figini R. V.
Published: April 2003

A numerical procedure is described for the quantitative interpretation of experimental fractionations by successive precipitations. The analysis is based on a thermodynamic relationship (mp″/mp′ = A·Bp) between the masses of a polymeric component with degree of polymerization, p, distributed between two liquid phases in equilibrium (mp″ and mp′) and the parameters A and B, which are independent of the degree of polymerization but functions of the thermodynamic variables. An individual pair of A and B parameters corresponds to every individual fraction. The numerical procedure, which is iterative in nature, provides the means for calculating the molecular‐weight distribution of the individual fractions. The procedure requires data from the experimental fractionation (number‐average degree of polymerization and total mass fraction of each fraction) and knowledge of the molecular‐weight distribution function of the whole, starting polymer. The procedure was applied to the analysis of the results of two experimental fractionations of polyamide 11, whereby covergence was quickly reached after a few iterations in the calculations of every set of A and B parameters.
Optimizing polyimide cure using infrared spectroscopy and a factorial design
Authors: Baise A. I.
Published: April 2003

The cure of a polyimide derived from pyromellitic dianhydride (PMDA) and oxydianiline (ODA) has been studied using infrared spectroscopy. A factorial experimental design, combined with regression analysis, was used to find the optimum curing conditions. It was shown that five micron films can be cured by heating at 230–250°C for times of five minutes or longer, while samples cured initially at 150°C did not cure completely when heated to higher temperatures.
Morphological, structural, and interfacial changes produced in composites on the basis of polypropylene and surface‐treated sepiolite with organic acids. III. Isothermal and nonisothermal crystallization
Authors: Acosta J. L. , Ojeda M. C. , Morales E. , Linares A.
Published: April 2003

Two kinetics studies with regard to isothermal and nonisothermal crystallization were conducted on composites samples containing polypropylene and sepiolite surface‐treated with isobutyric acid. Comparison of both studies allows us to demonstrate that isobutyric acid‐treated sepiolite incorporated to the polypropylene at different ratios acts as an effective nucleating agent and, due to its surface activity, generates two different crystalline structures, one of which is attributable to the formation of a mesophase on the periphery of the sepiolite particle.
Sound attenuation of interpenetrating polymer network foams
Authors: Klempner D. , Wang C. L. , Ashtiani M. , Frisch K. C.
Published: April 2003

Interpenetrating polymer networks (IPNs) composed of polyurethanes and epoxies were prepared by the simultaneous technique. Modifications of the polymer structures resulted in a series of IPNs exhibiting semimiscible behavior, as evidenced by broad glass transitions in the dynamic mechanical spectra. Since this indicates materials with potentially good sound attenuation properties as a function of temperature and frequency, foams were prepared from these IPN systems. Enhanced sound absorption occurred in these foams when measured using the impedance tube method.
Determination of the density distribution of suspension poly(vinyl chloride) by the density titration method
Authors: Ševčík S. , Kolínský M.
Published: April 2003

A dynamic method of density titration for the characterization of powders of suspension poly(vinyl chloride) (PVC) and of their fractions obtained by sieve analysis is described. The method is based on the distribution of PVC particles in variously concentrated aqueous solutions of sodium nitrate according to their specific weight. Separated phases are determinated volumetrically. The method makes possible characterization of various types of PVC powders and of their anomalies.
Tetrachlorophthalic anhydride‐based flame‐retardant chloropolyesters for inhibition of double‐base propellants
Authors: Agrawal J. P. , Kulkarni K. S.
Published: April 2003

Seven unsaturated chloropolyesters based on tetrachlorophthalic anhydride (TCPAn) maleic anhydride (MAn), and propylene glycol (PG) (designated as CP‐1) and TCPAn, MAn, and polyethylene glycol molecular weight 200 (PEG‐200) (designated as CP‐2), and TCPAn, MAn, and mixed glycols (PG & PEG‐200 in different molar proportions) and designated as CPM‐2, CPM‐4, CPM‐6, etc. (depending upon molar proportions) have been synthesized. The flameretardant characteristics have been assigned by measuring heat resistance (loss in weight) and flame retardance (burning rate), and it is found that in these chloropolyesters thermal stability increases as chlorine percentage increases. In addition, these chloropolyesters have been characterized for gel time, exotherm peak temperature, tensile strength, percentage elongation and bond strength, nitroglycerine absorption, and cross‐link density. Based on these properties, CPM‐9 with 30% styrene (designated as CPM‐9s) has been selected for inhibition and static evaluation trials, after conditioning at ambient, cold (−40°C), and hot (+50°C) temperatures. The nature of pressure–time profiles indicate the suitability of “CPM‐9s” for the inhibition of double‐base (containing 2‐NDPA) propellants.
Preparation of vinylpyridine irradiation‐grafted poly(4‐methyl‐pentene‐1) membrane for oxygen enrichment
Authors: Lai J. Y. , Wei S. L.
Published: April 2003

By adjusting the casting conditions, the oxygen permeabilities of poly(4‐methyl‐pentene‐1) (TPX) membranes prepared in this study are in the range of 2.91–7.14 × 10−9 cm3(STP) cm/cm2 s cm Hg and permeability ratio of O2/N2 between 2.7 and 4.4. To increase O2N2 selectivity, the vinylpyridine is γ‐ray irradiation‐grafted onto the substrate–TPX membrane. The factors that affect the structure and performance of the grafted membrane considered are: tightness of substrate, kind of solvent for grafting monomers, irradiation conditions, total irradiation dose, and operating temperature and pressure. The O2/N2 selectivities of grafted TPX membranes are significantly improved comparing to that of nongrafted TPX membranes. For example, an O2 permeability of 35.6 × 10−10 cm3(STP) cm/cm2 s cm Hg and an O2/N2 permeability ratio of 7.5 for the grafted membrane can be obtained.
Some aspects of plasticizer migration from poly(vinyl chloride) sheets
Authors: Papaspyrides C. D.
Published: April 2003

Long‐term migration data, by radioactivity measurements, are presented for the systems poly(vinyl chloride) (PVC)/labelled dioctyl phthalate (DOP)/methanol, n‐propanol, or n‐butanol. At equilibrium, migration levels determined exceed 85% for methanol and reveal complete removal for the higher alcohols. Migration kinetics failed to be described by the long‐term Fickian approximation with a diffusion coefficient independent of concentration. Nevertheless, qt/q∫, where q∫ the amount migrated at infinite time and qt the amount lost up to time t, increases linearly with (time)1/2/(thickness) during the initial stages of the process and then a linear also relationship appears, but with severely reduced slope. Similar data concerning the systems PVC/DOP/petroleum oils confirm the behavior observed.
An infrared microspectroscopy method for determining deterrent penetration in nitrocellulose‐based propellant grains
Authors: Varriano‐Marston E.
Published: April 2003

Infrared microscopy was used to determine di‐n‐butyl phthalate, dinitrotoluene, and methyl centralite diffusion profiles in cross sections of nitrocellulose‐based propellant grains. Absorbance of marker functional groups was determined at 25–50 µm intervals from the edge to the center of the sections. Comparison of IR and light microscopical data indicated that the optically visible boundary does not define the entire depth of deterrent penetration into propellant grains.
Photochemistry of polymeric systems VII. Photo‐cross‐linking of liquid polysiloxanes including cinnamic groups
Authors: Lemaitre Etienne , Coqueret Xavier , Mercier Régis , Lablache‐Combier Alain , Loucheux Claude
Published: April 2003

Cinnamoyloxymethyl dimethyl vinyl silane was synthesized and bound to a series of commercial polydimethylsiloxane‐type copolymers bearing variable amounts of SiH functions through a hydrosilylation reaction. This reaction was controlled in order to avoid side reactions between the photosensitive unsaturated moiety and the SiH groups.

The photosensitivity of polymeric films was studied by a photoresist test described in previous papers. The results emphasize the role of the molecular weight of the starting copolymer and the percentage of pendant photosensitive groups.
Synthesis and characterization of vegetable tannin‐vinyl graft copolymers part I. Cutch‐poly(methyl acrylate) graft copolymers
Authors: Vasantha R. , Rao K. Panduranga , Joseph K. Thomas
Published: April 2003

New graft copolymers were synthesized by grafting methyl acrylate onto cutch, a vegetable tanning agent, in acetic acid medium with hydrogen peroxide as the initiator. The graft copolymers were characterized by infrared spectroscopy and thermogravimetric analysis. The dependence of the percentage of grafting, monomer conversion, efficiency of grafting and rate of grafting on the concentrations of initiator, acetic acid, and cutch were investigated. The optimum experimental conditions for grafting were obtained. A probable mechanism of grafting was also proposed.
Uniaxial compaction behavior of filled polymer powders
Authors: Bhateja S. K. , Gilbert J. R. , Andrews E. H.
Published: April 2003

A simple method is described to obtain rheological data on filled polymeric materials in the form of powders. The powder is compacted in a cylindrical chamber by a plunger driven by the cross‐head in an Instron testing machine and the load‐displacement curve is recorded. Further information is obtained by compressing the powder to a fixed load and measuring the load decay with time (stress‐relaxation). The tests are illustrated by application to “monocomponent toner” powders used in dry copying or nonimpact printing processes. It is shown that compaction and stress‐relaxation data are able to differentiate between different toners and facilitate the prediction of their relative performances in terms of pressure fusing. A mechanical spring‐dashpot‐slider model is effective in describing the rheological behavior of these powders and its dependence on the loading of a hard filler (magnetic pigment). The latter affects the “slider” yield stress in the model but has no influence on the relaxation times.
Electron beam effects on polymers: Structure–property behavior of radiation‐cured bis‐GMA
Authors: Thompson Danny , Song Joo Hae , Wilkes Garth L.
Published: April 2003

Structure–property relationships were investigated for the diglycidly methacrylate derivative of bisphenol‐A crosslinked by electron beam irradiation. This material, commonly called bis‐GMA, is a viscous liquid at room temperature which crosslinks to form a glassy network. The major parameters which were systematically varied in this study were radiation dosage, dose rate, aging time after irradiation, and post‐cure annealing at higher temperatures. Measurements were conducted to quantify the crosslinking reaction and to characterize the physical properties of the resulting networks. Solvent extraction was done to determine the relative degree of network formation through the equilibrium swelling and the gel weight fraction after drying. Another method utilized FTIR to monitor the disappearance of double bonds as the crosslinking reaction proceeded. To characterize the thermal and physical properties, differential scanning calorimetry (DSC) and dynamic mechanical spectroscopy were utilized. Network density was found proportional to the irradiation dosage, with an upper limit reached above some critical dosage. Over the range of dose rate studied, this variable was not found to influence the degree of cure greatly. The crosslinking reaction became diffusion limited as vitrification occurred. These phenomena were discussed in terms of the well‐known time–temperature–transformation diagram. Free radicals trapped in these reacting networks due to vitrification exhibited a finite lifetime. Post‐curing could be achieved by annealing at a temperature above the Tg of the initially cured network, as shown by the increase of the glass transition temperature from both DSC and dynamic mechanical results.
Accelerated heat age testing of phenolics: Morphological changes
Authors: Stransky Paul D. , Johnson Julian F. , Yates W. Ross
Published: April 2003

The morphological changes that occur in molded phenolic specimens during long‐term heat aging tests have been observed in optical and scanning electron microscopy. The changes in morphology include shrinking and the formation of both cracks and charred zones in the phenolic matrix. The relationship of these morphological changes to weight losses and flexural strength losses was demonstrated.
Changes of non‐Newtonian behavior of carboxylated acrylate dispersions during alkalinization
Authors: Quadrat Otakar
Published: April 2003

Changes of flow curves of the carboxylated acrylate latex dispersions during alkalinization were described in terms of parameters of the Cross theory of aggregation of disperse particles. It was found that the dependence of viscosity on pH has a maximum at pH ≃ 9.3 where a yield stress appears.
Study of the curing process giving the rigid polyurethane foam by dynamic viscoelastic method
Authors: Nabata Yoshiyuki , Mamada Akira , Yamasaki Harumasa
Published: April 2003

Dynamic viscoelastic properties of the rigid polyurethane foam, which is used in Japan as a thermal insulator for refrigerators were studied during the curing process using the RDS‐7700 Dynamic Spectrometer. The curing process, in which large volume expansion and heat evolution occurred, was easily analyzed by this method. The apparent storage modulus (G′app), the apparent loss modulus (G″app), and the apparent loss tangent (tan δapp) were measured as a function of cure time. The effects of the curing temperature and the amine catalyst on the curing process were investigated. It was found that the curing process proceeded through three stages: logarithm of G″app (log G″app) increased with increasing cure time in the first stage, log G″app increased with increasing logarithm of cure time in the second, and the change of G″app cannot be expressed simply in the final. Curing behavior can be estimated from changes of rheological parameters during the curing. The fluidity of reaction mixture can be also predicted from the peak time of tan δapp.
Viscoelastic properties of (cellulose oligo‐oxymethylene ether) acylates with bulky side chain
Authors: Morooka Toshiro , Norimoto Misato , Yamada Tadashi , Takuma Satoshi , Okamura Keizo
Published: April 2003

A series of (cellulose oligo‐oxymethylene ether) acylates (COAs) are characterized by the presence of the micro‐Brownian motion of the side chain (β process) which appears separately from that of the main chain (α process). Both the alpha; and β processes are largely affected by the kind of acyl groups introduced in the side chain. To clarify the effect of the acyl group on these processes, we investigated the dynamic mechanical properties of newly prepared COAs with acyl side chain, bulky in chemical structure (iso‐butyrate, privalate, and benzoate) in relation to those for COAs with linear acyl side chain (acetate, butyrate, and valerate). By substituting bulky acyl isomer for linear acyl group in COAs, we observed that the temperature region of both the α and β processes moved to higher temperature. Furthermore, with an increase in molecular size of bulky acyl group, the β region shifts were much larger than the α region, indicating that the mobility of the side chain became comparable to that of the main chain. Finally, when such a large bulky group, for example, benzoate was introduced, the micro‐Brownian motion of the side chain prior to that of the main chain ceased. The apparent activation energy for a third process (γ) due to the motion of the oligo‐oxymethylene parts in the side chain was estimated to be 10.3 kcal/mol.
Surface tension of polytrifluoropropylmethylsiloxane
Authors: Owen Michael J.
Published: April 2003

Surface tension studies of the most common fluorosilicone, poly(3,3,3‐trifluoropropylmethylsiloxane) (PTFPMS), give unexpected results. Compared to polydimethylsiloxane (PDMS), the liquid surface tension is higher, the critical surface tension of wetting similar, and the solid surface tension, determined by water and methylene iodide contact angles and the method of Owens and Wendt, considerably lower. As the outermost surface of the lowest energy materials are comprised of close‐packed perfluoromethyl groups and as a flexible polymer backbone should aid in the adoption of the lowest surface energy configuration, fluorosilicones could in principle be the lowest surface energy polymers. In practice, other groups such as the ethylene link between the perfluoromethyl group and the siloxane backbone in PTFPMS are required to produce a stable material. This introduces factors such as bulkiness of side chains, unresolved fluorocarbon/hydrocarbon dipoles, and fluorine/silicon coordination effects. The results are discussed in these terms and compared with PDMS and two fluoropolymers, polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE). PTFE shows similar trends to PTFPMS whereas PCTFE behaves rather like PDMS.
Synthesis and properties of bismaleimide resins containing ether bonds
Authors: Takeda Shinji , Akiyama Hiromi , Kakiuchi Hiroshi
Published: April 2003

New bismaleimides containing ether bonds were prepared. The thermal properties of the bismaleimides were investigated by differential scanning calorimetry (DSC). The effects of structure of the bismaleimides and curing conditions on the thermal and mechanical properties of the cured resins such as initial decomposition temperature (Td), glass transition temperature (Tg), and flexural strength were studied. The introduction of ether bonds to bismaleimide resins decreased the brittleness of the resins without reductions in their heat‐resistant properties.
Linear polyesters products of interfacial polycondensation of bis(4‐hydroxyphenyl)ether with some aliphatic acid dichlorides
Authors: Podkościelny Wawrzyniec , Wdowicka Danuta
Published: April 2003

New polyesters were obtained by interfacial polycondensation of bis(4‐hydroxyphenyl)ether with succinyl, adipolyl, suberoyl, or sebacoyl chlorides. To define the optimal conditions of the process, the polyesters of diol and adipoyl or sebacoyl chlorides were chosen as a model system. Yield for all reaction products and reduced viscosity were found. The following factors were studied: organic phase, contribution of catalyst, concentration and molar ratio of reagents, rate of addition of acid chloride, temperature of reaction and concentration of hydrochloride acceptor. The structure of all polyesters was determined by means of elementary analysis, infrared spectra, and X‐ray. Initial decomposition and initial intensive decomposition temperatures were defined by the curves of thermogravimetric analysis. Thermal and electrical properties of polyesters from diol and adipoyl or sebacoyl chlorides were studied. The molecular weights for these polymers were also determined by gel chromatography.
Synthesis of sulfone‐modified poly(vinyl alcohol) and its application for permselective membrane of sulfur dioxide
Authors: Imai Kiyokazu , Shiomi Tomoo , Tezuka Yasuyuki , Takada Matsunori
Published: April 2003

The Michael type addition reaction of poly(vinyl alcohol) (PVA) with a series of vinyl sulfones, namely methyl vinyl sulfone, ethyl vinyl sulfone, and t‐butyl vinyl sulfone, was performed with NaOH as catalyst to produce 2‐(alkylsulfonyl)ethyl PVA derivatives. The high permselectivity of sulfur dioxide against nitrogen and oxygen was achieved through these sulfone‐modified PVA membranes.
Melt transcrystallization of polyethylene on high modulus polyethylene fibers
Authors: He Tianbai , Porter Roger S.
Published: April 2003

A polytheylene composite was prepared and tested. It was consisted of a high‐density polyethylene (HDPE) matrix and uniaxial gel‐spun high‐modulus PE fiber. Aided by the similarity between matrix and fiber, transcrystallization of HDPE melt on the PE fiber surface was generated. Nucleating agents were not employed. The transcrystalline growth of HDPE on the PE fiber surface was found to consist of an inner and an outer zone. The inner zone, 2–3 μm thick, is composed of HDPE crystals nucleated on the PE fiber surface. Photomicrographs showed a well‐defined region of row‐nucleated HDPE on the surface of PE fiber. This means the fibrils of HDPE were found to grow out from the PE fiber axis and HDPE crystallites are oriented in planes perpendicular to the PE fiber axis. The fiber in the composite induced the transcrystalline growth of HDPE on the PE fiber surface at higher temperature than on cooling the melt. For 36 wt% fiber, the increase was 2.5°C, also resulting in ∼ 10% more crystals. Crystallization of a composite with 50 wt% fiber at 124°C involved two steps: The first a fast transcrystallization of HDPE on the PE fiber surface followed by the bulk crystallization of the HDPE.
Water–ethanol permseparation by pervaporation through photocrosslinked poly(vinyl alcohol) composite membranes
Authors: Hirotsu Toshihiro , Ichimura Kunihiro , Mizoguchi Kensaku , Nakamura Eiichiro
Published: April 2003

Water–ethanol permselectivity was investigated by pervaporation through composite membranes which were prepared by coating photocrosslinkable poly(vinyl alcohol) containing pendant styrylpyridinium group (0.86–3.93 mol %) on porous films. These membranes were water‐permselective, and the selectivity was dependent on the state of membranes; namely, incorporation ratio of styrylpyridinium group on poly(vinyl alcohol), molecular weight of the base polymer, coating thickness of a photopolymer, etc. Photocrosslinkable styrylpyridinium group showed, of course, the ionic character by a pyridinium moiety to work on permseparation of water effectively as well as preventing the dissolution of membranes by crosslinking. Membranes based on the higher molecular weight poly(vinyl alcohol) (P = 1700) gave the higher permselectivity of water in general than those of lower molecular weight (P = 500) one. Swelling of the polymers reached 160%, and permeation rate through the membranes increased with the increase of swelling. Selective diffusion of water was found to take place in swelling, and to play a part in the water‐permseparation through the membranes.
The effect of spinning speed and drawing temperature on structure and properties of poly(ethylene terephthalate) yarns
Authors: Huisman R. , Heuvel H. M.
Published: April 2003

From an industrial point of view, it is effective to have a relation between process conditions and resulting product properties. In practice there are many possible process conditions, whereas properties are generally interrelated in a complex way. Thus, there is a strong need for a physical understanding of the product properties in terms of process settings. This comprehension should also allow one to predict possible consequences for the properties when new process conditions become available. To obtain that physical understanding for the development of production processes of PET yarns, use has been made of a simple two‐phase model of crystalline and amorphous regions. As process parameters the spinning speed and the drawing temperature were chosen. As the drawing temperatures are only known as machine‐setting values, they are simply referred to as “low” and “high.” As mechanical properties the shrinkage, modulus, tenacity, and dynamic mechanical behavior are discussed.
Lyotropic liquid crystalline solutions of hydroxypropyl cellulose in water: Effect of salts on the turbidity and viscometric behavior
Authors: Suto Shinichi , Nishibori Wataru , Kudo Kazuhisa , Karasawa Mikio
Published: April 2003

Effect of addition of salt on the viscometric behavior of the dilute or concentrated aqueous solution of hydroxypropyl cellulose (HPC) was determined by means of an Ubbelohde or a cone‐plate viscometer. That effect on the turbidity of the dilute system was also determined. As salts, NaCl, LiCl, and thiourea were chosen. The turbidity and viscometric behavior for the dilute system, and the viscometric behavior for the concentrated system were greatly affected by salt type and concentration. With increasing NaCl or LiCl concentration, the cloud point decreased, [η] showed a maximum, Huggins' constant k′ showed a minimum, and the shear viscosity for concentrated isotropic solutions showed a maximum. The 45 wt % solution with no salt showed a viscometric behavior which was characteristic of lyotropic liquid crystals; however, with increasing NaCl concentration, a critical temperature at which the shear viscosity showed a maximum with respect to temperature shifted to lower temperature. This behavior was due to an increase in the turbidity, not due to a phase transformation. On the other hand, an addition of thiourea did not affect so greatly the turbidity and viscometric behavior as an addition of NaCl or LiCl did. We speculated different actions of NaCl and thiourea.
Kinetics studies of solvent‐induced crystallization of drawn poly(ethylene terephthalate) by the in situ density measurement
Authors: Im Sung Soon , Lee Hyung Sick
Published: April 2003

The effect of draw ratios on the solvent‐induced crystallization (SINC) of poly(ethylene terephthalate) (PET) films was investigated. Dimethyl formamide (DMF) and dioxane were used as strongly interacting solvents. A newly devised in situ density measuring apparatus was applied to directly examine solvent peneration kinetics in PET. In this article, the density of PET films, which had a linear relation with crystallinity, was estimated rather than the degree of crystallinity. The solvent‐penetrated PET film was divided into three regions: a surface‐cavitated, a crystalline‐swollen, and an unpenetrated region, to determine the specific characteristics of the respective regions. It was found that the density in the internal region and the fraction of the surface‐cavitated region had a larger dependence on draw ratio than on treatment temperature. Also, the diffusion coefficients for the crystalline swollen region were calculated at various draw ratios and the morphological structure of the PET films was described.
Monitoring the cure of unsaturated polyester resins by pressure DSC and FTIR‐PLC
Authors: Yang Y. S. , Lee L. James , Lo S. K. Tom , Menardi P. J.
Published: April 2003

A high pressure differential scanning calorimeter (DSC) and a Fourier transform infrared (FTIR) spectrometer with a prism liquid cell (PLC) were used to monitor the reaction kinetics of styrene‐unsaturated polyester resins at elevated curing temperatures and pressures. The thermal method is easy to perform but provides only an overall reaction exotherm. The spectroscopic method can detect the detailed reaction mechanism of copolymerizations. It is, however, less quantitative and the calculation is much more time‐consuming compared to the thermal analysis. Reactions of two unsaturated polyester resins with different molecular structure were measured by these two methods. Results showed that applying cure pressure on unsaturated polyester resins reduced the reaction rate but increased the final conversion. The styrene reaction was enhanced more than the polyester reaction at high curing temperatures.
Kinetics of multimonomer emulsion polymerization. The pseudo‐homopolymerization approach
Authors: Storti G. , Carrà S. , Morbidelli M. , Vita G.
Published: April 2003

By generalizing the Smith–Ewart theory, a system of polymer particle population balances is developed for describing the kinetics of emulsion polymerization processes involving any number of monomer species. Each population is characterized by the number of active radicals of each type present inside each particle, and described through a size distribution function. An approximation procedure is proposed for reducing the original system to that typical of homopolymerization processes, thus characterizing each population‐only through the overall number of radicals, without any significant loss of accuracy. The reliability of such “pseudo‐homopolymerization approach” is tested by comparison with polymer composition vs. monomer conversion experimental data for the ternary system acrylonitrile–styrene–methyl methacrylate.
Degradation mechanism and morphological change of PET by PEG–diamine
Authors: Kim Kap Jin , Ko Sohk Won
Published: April 2003

The aminolysis mechanism and morphological change were investigated with NMR, IR, GPC, density, and other physicochemical methods when the biaxially drawn PET film was aminolyzed with PEG–diamine at 130°C. By the aminolysis reaction, the PET chain end was capped with PEG chain as the following equation:
magnified image
Molecular weight showed a rapid decreasing tendency in the initial stages of the aminolysis reaction. The crystallinity, measured by density and IR methods, increased with the reaction time mainly due to the recrystallization of the amorphous PET chain promoted by better chain mobility of the PEG‐terminated PET. The fold period of the chain‐folded lamellar crystal formed through recrystallization was the same as that of the original PET lamellar crystal. It was found that 74% of all the capped PEG chains were located in the amorphous region, 18.4% at the initial point from which the recrystallized lamellar crystal began to grow, and the rest in the lamellar crystalline lattice.
A study on viscosity of suspensions
Authors: Chiu Wen‐Yen , Don Trong‐Ming
Published: April 2003

From a simple kinetic viewpoint for the formation and rupture of links among primary particles, the pseudoplastic behavior of suspensions can be well described. At steady state, the formation and rupture of links reach a dynamic equilibrium, and the viscosity of suspension is proportional to the state of aggregates. It is assumed that the formation of links is due to the surface forces over particles, including van der Waals' force, and is independent of shear rate. The rupture of links is proportional to ṙm. Finally we get a very simple equation to predict the viscosity of suspension. With this simple kinetic viewpoint, the pseudoplastic behavior of suspensions composed of binary blends of monosize particles is also predictable.
Properties of bound water in poly(acrylic acid) and its sodium and potassium salts determined by differential scanning calorimetry
Authors: Haldankar Gautam S. , Spencer H. Garth
Published: April 2003

The thermal transitions occurring in poly(acrylic acid) and its sodium and potassium salts were investigated over a large range of water content using differential scanning calorimetry at temperatures below the normal melting temperature of water. The bound water was identified as nonfreezing (type I), freezing with a constant melting temperature (type II), and freezing with a melting temperature dependent on the water content (type III). The transition temperatures of the freezing states of the water were determined. Two constant melting temperatures were observed for the type II water in the sodium and potassium polyacrylates, while a single transition of this type was observed for poly(acrylic acid). The sodium polyacrylate absorbed more water in the nonfreezing state than the potassium polyacrylate, and both polyelectrolytes absorbed about three times as much water in this state as the nonionic poly(acrylic acid). The effects of water content on the occurrence of an exotherm at low temperature in the melting scans of the polyelectrolytes are described.
Homogeneous and heterogeneous copolymerization of styrene and sulfur dioxide using the (CH3)3COOH/SO2 redox system
Authors: Ali Sk. A. , Tsonis C. P. , Wazeer M. I. M.
Published: April 2003

Styrene was copolymerized with sulfur dioxide in the presence of tert‐butyl hydroperoxide under homogeneous and heterogeneous conditions. The rate of copolymer formation decreases in the order emulsion, suspension, organic–aqueous, and organic solution. The rate also depends on reaction time, temperature, solvent, and initiator concentration. Several physical methods used to characterize these copolymers, including IR, 13C‐NMR, elemental analysis, viscosity, softening point, and isothermal aging. Analysis of the composition of the resulting copolymers revealed that there are on the average about two molecules of styrene per SO2 present on the copolymer chain. 13C‐NMR suggests that these copolymers are made up mostly of the MSM, SMM, and MMS triad monomer sequences whereas the SMS and MMM are present in small amounts. Characterization of polystyrene homopolymers shows that there is lack of stereoregularity in both homogeneous and heterogeneous polymerization systems.
The characterization of a poly(ethylene terephthalate)–poly(tetramethylene ether) multiblock copolymer via cross fractionation and size exclusion chromatography
Authors: Zhonge Xu , Ping Yuang , Jingguo Zhong , Erfang Jiang , Meiyan Wu , Fetters Lewis J.
Published: April 2003

A poly(ethylene terephthalate)–poly(tetramethylene ether) multisegment block copolymer has been characterized by cross fractionation, where the individual fractions were then analyzed via size exclusion chromatography. The use of dual detectors (refractive index and ultraviolet) allowed both the compositional heterogeneities and molecular weight distributions to be evaluated. The SEC based molecular weights were supplemented by osmometric based molecular weights.
Properties of syndiotactic‐rich poly(vinyl alcohol) thin film in water. VII. Elastic behavior of swollen film in water through heating/cooling or cooling/heating cycles
Authors: Yamaura Kazuo , Watanabe Junko , Tanigami Tetsuya , Matsuzawa Shuji
Published: April 2003

The thermoelastic behavior for highly swollen films of syndiotactic‐rich poly(vinyl alcohol) (s‐PVA) was ascertained under loads in water through heating/cooling or cooling/heating cycles (in the range of 25–70°C). The s‐PVA films kept at the high temperature of 70°C behaved as a perfect elastomer through the cooling/heating cycle and had very low Young's modulus, 2–3.5 × 106 dyn/cm2. When highly swollen s‐PVA films were kept at lower temperatures below about 50°C for a long time, microcrystals were formed or propagated in the s‐PVA films and plastic deformation occurred in addition to elastic deformation through heating process. The microcrystalline growth and propagation at lower temperatures were supported by an increase in Young's modulus and a decrease in the molecular weight between junctions.
Acetylation of jute: Effects on strength, rot resistance, and hydrophobicity
Authors: Andersson Mona , Tillman Anne‐Marie
Published: April 2003

Jute cloth was acetylated with a limited amount of liquid acetic anhydride at 120°C. Weight gains of up to 20% were obtained. At a weight gain of 11%, achieved after a reaction time of 2 h, resistance to fungal attack was greatly improved. The cloth was also even in color, and the reduction in strength was minor. Tests on equilibrium moisture content and water uptake showed that the acetylated jute was much more hydrophobic than the unmodified material. It also shrank less when leached in water. Hence, dimensional stabilization was obtained.
Residual porosity in polymeric latex films
Authors: Balik C. M. , Said M. A. , Hare T. M.
Published: April 2003

Solubility and diffusivity measurements of a probe gas (CO2), which has an inherently low solubility in the polymer, have been used to characterize residual porosity in polymeric latex films. Sorption isotherms resembling those of a glassy polymer were obtained, even though the glass transition temperature of the polymer was 1°C, about 30°C below the experimental temperature. Solvent cast films of the same polymer exhibited much lower solubilities, and followed the expected Henry's law behavior. CO2 solubility and diffusivity were found to decrease with aging time for the latex films, but did not quite reach the values of the solvent cast films, even after 75 days at room temperature. The sorption data could be described by the dual‐mode sorption model, which is commonly employed in the analysis of glassy polymer sorption isotherms. Estimates of the amount of porosity were made from the sorption data, and values ranging from 0.6–0.03% were obtained for latex films aged from 62 h to 75 days, respectively. Our results suggest that permeability differences noted by others for latex and solvent cast films of the same polymer are due to the substantial solubility differences for low‐solubility penetrants in these two types of films.
Oxidation of cellulose by ceric ion
Authors: Graczyk Tomasz
Published: April 2003

Dissolving pulp was oxidized by ceric ammonium sulfate in sulfuric acid medium under oxygen‐free argon. Initial rapid oxidation was followed by first‐order consumption of ceric ion. The rate of cellulose oxidation (−RCe) which was taken at the beginning of the first order consumption period, levelled off with an increase in the concentration of ceric ion. It was found that the −RCe was dependent on the concentration of cellulose in the second power. The rate of ceric ion consumption was a function of the available surface area of cellulose.
Effect of flow rate and temperature on crystallization kinetics, crystallinity index, and elastic modulus of PEEK
Authors: Mishra Ajit Kumar , Schultz Jerold M.
Published: April 2003

Dynamic, in situ wide angle X‐ray scattering (WAXS) studies of the melt crystallization of injection‐molded poly(ether ether ketone) (PEEK) have been carried out using an X‐ray diffractometer and a position‐sensitive detector. A test cell has been fabricated to fit inside the diffractometer and yet work as a complete injection molding apparatus. The rate of crystallization has been shown to increase with decreasing crystallization temperature and/or increasing flow rate in the mold. The crystallization rate decreases dramatically with increase in melt soak time at 400°C. The crystallinity index, which affects the stiffness, toughness, and fracture behavior of PEEK, has been measured under various processing conditions, by wide angle X‐ray scattering, so as to optimize the process parameters: molding time, mold temperature, melt temperature, soak time at melt temperature, and flow rate. It has been shown that the crystallinity and hence the elastic modulus increase with increase in crystallization temperature and/or flow rate. Chain orientation has been shown to be absent in the bulk of the injection‐molded specimens under normal molding conditions.
Transport models for swelling and dissolution of thin polymer films
Authors: Papanu J. S. , Soane (Soong) D. S. , Bell A. T. , Hess D. W.
Published: April 2003

Fundamental models have been developed to describe swelling and dissolution of glassy polymer thin films. The models account for solvent penetration by either Fickian or Case II diffusion mechanims. The convective flux due to local swelling as the solvent penetrates is included. Chain disentanglement at the polymer‐developer solution interface is scaled with the local solvent concentration and polymer molecular weight using reptation theory. The effective surface concentration during dissolution is estimated by applying thermodynamics of swollen networks to the entangled polymer. Swelling and dissolution of thin polymer films have direct application to microlithography. Various molecular and processing parameters affect the outcome of resist development. The utility of the models for selecting appropriate developer solvents, minimizing resist swelling, and providing a better understanding of the swelling and dissolution of resists is demonstrated.
The effect of hot‐wet draw ratio on the coefficient of friction of wet‐spun acrylic yarns
Authors: Gupta B. S. , El‐Mogahzy Y. E. , Selivansky Dror
Published: April 2003

A series of wet‐spun poly(acrylonitrile‐co‐vinyl acetate) yarns that were hot‐wet stretched to a draw ratio range of 2.0 × −7.0 × were made for study of surface morphology and frictional characteristics. These yarns show an increase in draw ratio. The fiber to fiber coefficient of friction, measured parallel (line contact), and perpendicular (point contact), increases with draw ratio, giving an excellent correlation between orientation and friction. The effects of hot‐wet draw ratio on the surface structure and its frictional behavior are discussed.
Interaction of cation‐exchange membrane with polycation. II. Poly(N‐alkyl‐4‐vinylpyridinium halides)
Authors: Ohmura Nobuhiko , Kagiyama Yasuhiro , Mizutani Yukio
Published: April 2003

The effect of the hydrophile–lipophile balance (HLB) of poly(N‐alkyl‐4‐vinylpyridinium halides) (PAVP) on the interaction between PAVP and the cation‐exchange membrane was elucidated by using various alkyl groups: methyl, ethyl, octyl, and so on. In the electrodialytic concentration of sea water by using the membrane on which PAVP has been adsorbed or ion‐exchanged, the ratio of monovalent cations to total cations in the concentrated brine, β (Na+K), is almost same at the initial stage in species of PAVP. However, the deterioration ratio of β(Na+K) is smaller with decreasing HLB. In order to obtain the large value of β(Na+K), poly(N‐methyl and dodecyl‐4‐vinylpyridinium chloride) (PMDVP), was investigated. PMDVP, of which the ratio of pyridinium groups quaternized with 1‐bromododecane to total pyridinium groups (Qd) is about 40%, shows high initial value of β(Na+K) and its good durability.
Investigation of structure of polyacrylonitrile–polyprorole composite film
Authors: Bhat N. V. , Sundaresan E.
Published: April 2003

The structure of polyacrylonitrile–polypyrrole composite film, prepared using pyrrole in vapor and FeCl3 as catalyst, was investigated using IR spectroscopy, DTA/TGA, and resistivity measurements. The films showed improved thermal stability and electrical conduction. The strength of the composite film decreased as compared to pure PAN and the growth structures of polypyrrole could be seen.
Further experimental evidences of the compatibility of poly(vinyl acetate) with poly(ethyl methacrylate) and its dependence on the ratio of the molecular weight of the two homopolymers
Authors: Olayemi J. Y. , Yusuf A. K.
Published: April 2003

Using various fractions of poly(ethyl methacrylate) (PEMA) and poly(vinyl acetate) (PVAc) of very narrow molecular weight distribution, a very wide range of 2–120 of molecular weight ratio M¯ν PEMA/M¯ν PVAc, (M¯ν)r was obtained. Studies of some tensile mechanical properties of films of the blends produced from solution on mercury confirmed strong dependence of the improvements of PVAc properties for blend with 18% PEMA on (M¯ν)r, especially in the range 5 ≤ (M¯ν)r < 100. The density of the films of the blend was much higher than those of the individual polymers and increased monotonically with (M¯ν)r. Optical micrographs of the films of the blends showed interactions between the two polymers with 18% PEMA composition, which appears to be more intimate as (M¯ν)r increases, as further evidence of compatibility and miscibility of the two polymers.
A cubic equation of state for high‐pressure phase equilibria of mixtures containing polymers and volatile fluids
Authors: Sako Takeshi , Wu Albert H. , Prausnitz John M.
Published: April 2003

Generalized van der Waals theory is used to obtain a three‐parameter cubic equation of state which is applicable to fluids containing small or large molecules, including polymers. The necessary parameters are obtained from a minimum of experimental information. Upon extension to mixtures, the equation of state is used to calculate high‐pressure phase equilibria for the ethylene–polyethylene system. The relatively simple equation may be useful for engineering‐design calculations for fluid mixtures containg polymers, especially when very few experimental data are available.
Model approach to dielectric‐thermal analysis of wood modified with polymer
Authors: Hoffmann Grzegorz , Poliszko Stefan , Hilczer Tadeusz
Published: April 2003

The modeling of dielectric properties of wood–polymer composite, considered as a multicomponent layered system, was performed. The obtained solutions were used to determine temperature dependences of real and imaginary parts of complex dielectric permittivity characterizing the wood component in the natural and polystyrene‐modified wood in the directions parallel and perpendicular to the fibers. The analysis of the calculated dependences proved that the structural changes of wood depended on the applied method of modification. The main effect attributed to the styrene polymerization occurring in wood placed in a hydrophilic heating medium was an increase in the ordering degree of the mesomorphous regions of cellulose. As a consequence, a part of the polar, functional groups distinguished by particularly high activation energies (i.e., low probability of a dipole jump to an adjacent site) was eliminated from participation in the relaxation processes. The application of a hydrophobic heating medium during modification procedure resulted in a permanent swelling effect of the wood component of the composite. Within the applied investigation method it was found that the changes in increment of dielectric permittivity referring to the β‐relaxation process in wood substance can be the specific criterion of structural changes in wood modified with polystyrene. The distribution functions of relaxation times for natural and modified wood substance were determined.
Melt rheology of plasticized poly(vinyl chloride)/epoxidized natural rubber miscible blends
Authors: Varughese K. T.
Published: April 2003

A study of the melt rheological behavior of miscible blends of plasticized poly(vinyl chloride) (PVC) and epoxidized natural rubber (ENR) was carried out with a capillary rheometer. Melt viscosity and melt elasticity behavior was determined and surface characteristics of the extrudate was examined by using a scanning electron microscope. Melt viscosity of plasticized PVC increased with ENR content at higher processing temperatures. The melt elasticity parameters such as die swell ratio, principal normal stress difference, and recoverable shear strain at a particular shear stress increased with temperature up to a 50 wt % composition of ENR in blends. For high ENR blends the die swell ratio and recoverable shear strain decreased with temperature, and the principal normal stress difference and elastic shear modulus remained independent of temperature for all values of shear stress. It was noted that the nature of deformation in the surface layer was linear for a smooth extrudate and nonlinear for a distorted extrudate. Moreover, recoverable shear strain was found to have a correlation with the extrudate distortion of the melts.
Application of the percolation model to gelation of an epoxy resin
Authors: Serrano Daniel , Peyrelasse Jean , Boned Christian , Harran Daniel , Monge Philippe
Published: April 2003

The percolation model has been applied to the study of gelation of the TGDDM‐DDS system (tetraglycidyldiaminodiphenylmethane–diaminodiphenylsulfone) at a mass concentration of 100–30. For each temperature the experimental viscosity curves are satisfactorily described by a percolation law. Using the degree of chemical reactions, X, as a variable, a very clear change in the reaction mechanism with temperature can be shown. Then a rate of advancement of effective reactions, Y, is defined. This value only takes intermolecular‐type reactions into account, and is probably the only variable on which viscosity depends in a percolation law: η = B(1 − Y/Yc)−p. We obtain Yc= 0.45 and p= 2.0. Comparing Xc and Yc at the gel point, we obtain information on the proportion of intramolecular reactions with temperature. It is also demonstrated that the critical percolation threshold agrees closely with the gel point determined experimentally on log G″= f(t) curves.