bluuebunny/crossref_metadata_2025 huggingface dataset:
A new approach for the production of cellulose acetate: Acetylation of mechanical pulp with subsequent isolation of cellulose acetate by differential solubility
Authors: Barkalow D. G. , Rowell R. M. , Young R. A.
Published: April 2003

A heretofore uninvestigated approach to the production of cellulose acetate, the acetylation of whole wood pulp with subsequent isolation of the cellulose derivative by differential solubility, is described. The mechanical pulp used was produced by refining aspen wood chips with a disc refiner. Two conventional acetylation techniques, the fibrous and solution process, were employed to acetylato all components of the pulp. The cellulose acetate was isolated from the acetylated lignin and hemicellulose by dissolving in dichloromethane/methanol (9:1, v/v). The advantage of this new approach is that the high cost involved in using an extensively purified dissolving pulp are avoided. Both acetylation techniques yielded a product that was about 84% cellulose acetate. The remaining acetylated components were lignin and hemicellulose. The yield of cellulose acetate, based on the cellulose content of the original pulp and the product, was 75–80%.
Chemical modification of poly(substituted‐acetylene). IV. Pervaporation of organic liquid/water mixture through poly(1‐phenyl‐1‐propyne)/polydimethylsiloxane graft copolymer membrane
Authors: Nagase Yu , Mori Shigehiro , Matsui Kiyohide
Published: April 2003

Poly(1‐phenyl‐1‐propyne)/polydimethysiloxane (PPP/PDMS) graft copolymer membranes having various PDMS content were prepared by solvent casting method, and the permeation characteristics at pervaporation were examined upon the aqueous solutions containing organic liquids such as alcohols, acetone, dioxane, acetonitrile, pyridine, and DMF. At pervaporation of ethanol/water mixture, preferential permeation of ethanol was observed for all the copolymer membranes, although PPP membrane showed water permselectivity. The permselectivity of the copolymer membrane also depended on operation temperature, but was independent on the thickness of the membrane. Furthermore, an excellent permselectivity of organic liquids was observed at the pervaporation of several organic liquid/water mixtures except in the case of DMF/water mixture. Observed high selectivity is thought to be due to the depression of the membrane swelling and the high solubility of the liquids into the membrane.
A solid solvent as processing aid for polystyrene
Authors: Chung C. I. , Cao M. Y. , Liu C. , Min K. J.
Published: April 2003

Many polymers suffer from excessive heat generation during processing due to high viscosity, and reduction of viscosity is desired to control the melt temperature during processing. The concept of solid solvent was recently proposed based on thermally reversible compatibility between a polymer‐additive pair. Benzenesulfonamide was found to be virtually a perfect solid solvent for polystyrene, and this finding clearly proves that solid solvents can be used as processing aid for polymers to effectively reduce the viscosity.
Preparation of high‐strength poly(vinyl alcohol) fibers by crosslinking wet spinning
Authors: Fujiwara Hiroshi , Shibayama Mitsuhiro , Chen Jing Hui , Nomura Shunji
Published: April 2003

High‐strength poly(vinyl alcohol) (PVA) fiber was obtained by the crosslinking wet‐spinning technique, which is an improved technique of the conventional non‐crosslinked type wet‐spinning of PVA. High tensile strength as well as high Young's modulus was achieved by introduction of the borate ion‐aided crosslinks during the coagulation process. The drawability of the as‐spun fiber greatly depends on the fiber thickness. The thinner the fiber, the higher the drawability. Since thinner fiber is subject to a very high shear rate on extrusion, the crosslinks introduced are believed to maintain topological memory of the oriented chains, which have a low density of entanglements. This allows drawing the fiber to a higher draw ratio. The strength and Young's modulus of the resultant highly drawn PVA fiber were achieved to be 22 g/d (2.3 GPa) and 430 g/d (50 GPa), respectively. The mechanism of the spinning was discussed and the spinning condition was carefully examined in order to optimize the final mechanical properties of the PVA fibers.
Sorption and transport of CO2 in poly(ethylene terephthalate) crystallized by sorption of high‐pressure CO2
Authors: Hirose Takuji , Mizoguchi Keishin , Kamiya Yoshinori , Terada Katsuhiko
Published: April 2003

Sorption and permeation of CO2 in poly(ethylene terephthalate) crystallized by sorption of high‐pressure CO2 were examined below 1 atm at temperatures from 15 to 65°C. A large solubility and a high permeability of CO2 in this specimen were observed compared to poly(ethylene terephthalate) crystallized by thermal annealing to a similar degree. A large unrelaxed volume is expected to be left in the specimen after removal of high‐pressure CO2 compared to the data of other PET samples. The thermal history during the measurements up to 65°C, which causes relaxation of the specimen, was shown to decrease CO2 solubility. On the other hand, permeation data after annealing show not only decreased permeability but also increased apparent diffusivity. The results mean a lower mobility of gases sorbed in the unrelaxed volume than that of ordinarily dissolved gases, which corresponds to the partial immobilization model.
Free radical copolymerization of poly(n‐butyl methacrylate) onto polychloroprene
Authors: Srinivasan K. S. V. , Radhakrishnan N. , Pillai M. Kuttalam
Published: April 2003

Graft copolymerization of n‐butyl methacrylate onto polychloroprene was carried out in toluene using benzoyl peroxide as an initiator. The polychloroprene‐g‐poly(n‐butyl methacrylate) was isolated from the copolymerization product by extracting with hexane. Infrared (IR) spectra and nuclear magnetic resonance (NMR) of graft copolymer showed the occurrence of grafting. Percentage of grafting and grafting efficiency calculated under different experimental conditions were discussed. The mechanism of grafting seems to occur by chain transfer, as evidenced by a decrease in chlorine content during the experiment.
X‐ray‐induced reactions and resist features of polydibutylgermane
Authors: Ban Hiroshi , Deguchi Kimiyoshi , Tanaka Akinobu
Published: April 2003

Polydibutylgermane undergoes oxidation reaction and chain scission under X‐ray exposure. These reactions are the same as those observed for ultraviolet irradiation. Positive resist patterns can be fabricated by X‐ray lithography.
Stabilization of poly(vinyl chloride). X. Synergisms between epoxidized polybutadienes and metal soaps on the stabilization of poly(vinyl chloride)
Authors: Iida Takeo , Kawato Junji , Tanie Sachiko , Gotō Kuio
Published: April 2003

Effects of epoxidized 1,2‐ or 1,4‐polybutadienes on the zinc stearate/calcium stearate synergetic soap‐induced thermal stabilization of poly(vinyl chloride) (PVC) were investigated by colorimetry. The remarkable stabilization effects of epoxidized polybutadienes could not be observed on the PVC films without synergetic soaps, while the stabilization of PVC was markedly enhanced by combined use of epoxidized polybutadienes with synergetic soaps. Excessive coloration of cool color‐producing zinc chloride‐polyene complexes that were the source of abrupt discoloration of stabilized PVC was retarded by using epoxidized polybutadienes together with synergetic soap. The synergism of epoxidized polybutadienes was enhanced with increasing epoxy contents. Moreover, the effect is also clearly dependent on degree of dispersion of epoxidized polybutadienes in PVC. Further colorimetries, infrared (IR), and X‐ray photoelectron spectroscopies on the various PVC‐containing epoxidized polybutadienes and zinc chloride indicated that the epoxy groups capture the zinc chloride. The synergistic effect between epoxidized polybutadienes and metal soap was ascribed to epoxidized polybutadienes serving as acceptors for the excessive cool color‐producing zinc chloride produced by zinc stearate to retard the abrupt discoloration of stabilized PVC. The plate‐out phenomenon appeared during the molding process of PVC‐containing epoxy compounds was considerably retarded by epoxidized polybutadienes which modified polyols. The polyol‐modifying epoxidized polybutadienes also exhibited a marked effect on PVC stabilization with metal soap.
Syntheses and properties of pentaerythritol‐containing urethane prepolymers and crosslinked films
Authors: Yang Chin‐Ping , Lee Lung‐Ta
Published: April 2003

Two series of polyhydroxyl urethane‐prepolymers (Pre‐PU) were synthesized from pentaery‐thritol (PETH), toluene diisocyanate (TDI), and polyglycols (PG). One is a single molecular type of PETH‐(TDI‐PG)n‐TDI‐PETH Pre‐PU (S‐Pre‐PU). The other is a mixture of (PETH‐TDI)n‐PETH and S‐Pre‐PU. The Pre‐PU mixed with an equivalent triisocyanate regenerator (Desmodur AP‐Stable, a crosslinking agent) were baked to form the crosslinked PU films. The mechanical properties such as tensile strengths, elongation at break, and viscoelasticities of PG‐modified crosslinked films were studied.
Crystallization of PP in PP/Ni composites and its correlation with tensile properties
Authors: Maiti S. N. , Mahapatro P. K.
Published: April 2003

The effect of nickel (Ni) powder on crystallization of polypropylene (PP) in PP/Ni composites is studied through differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction techniques. Interpretation of crystallization exotherm peaks in terms of nucleation and growth rates of crystallization, crystallite size distribution, and crystallinity indicated differences in the morphology of PP in all the composites. Crystallinity and tensile behavior decreased on nickel addition. There is a good qualitative agreement in the crystallinity determined by X‐ray diffraction and DSC exotherms, and the variation in both cases, with the volume percent of filler is similar. An attempt has been made to correlate the various tensile properties with the crystallization parameters such as the crystallinity and crystallite size distribution.
Preparation of hydrophilic polyethylene foam of open cell type by radiation grafting of acrylic acid
Authors: Kaji Kanako , Hatada Motoyoshi , Yoshizawa Iwao , Kohara Choji , Komai Kuniaki
Published: April 2003

Hydrophilic polyethylene foam was synthesized by radiation grafting of acrylic acid onto polyethylene foam of open cell type using monomer solution containing Mohr's salt which inhibits homopolymerization of the monomer. The graft foam was easily dyed by cationic dyes and showed excellent moisture regain. The wicking properties were also excellent and were almost the same as those of commercially available PVA foam. The surface resistivity of 1016 ohm of the original foam decreased to 106 ohm and half decay time of surface charge decreased from 8000 s to 1 s by the grafting, indicating that the grafted foam has excellent antistatic properties.
Kinetics for the tensile strength degradation of nylon and kevlar yarns
Authors: Auerbach I.
Published: April 2003

The tensile strength degradation of nylon 66 and Kevlar 29 yarns was studied at elevated temperatures and over a broad range of relative humidities. The degradation rates for nylon are initially slow but increase rapidly, suggesting the depletion of an inhibitor. Kevlar showed no evidence for similar inhibitor action. The effect of relative humidity on degradation can be very large, especially at values in the 90–100% range and at elevated temperatures. Degradation is governed by thermal‐oxidative and moisture‐induced mechanisms. At the very high humidities and elevated temperatures, the moisture‐induced degradation predominates. Rate relationships were developed in which contributions from each mechanism were considered. Calculated degradation from these relationships agrees well with observed degradation over a broad range of temperatures and humidities.
Large scale preparation of melamine‐based superplasticizing admixtures. II. Pilot plant studies
Authors: Dairanieh I. S. , Lahalih S. M. , Absi‐Halabi M. , Dashti A.
Published: April 2003

The standard procedure for preparing sulfonated melamine–formaldehyde (SMF) resins was slightly modified to prepare an effective more concentrated resin. SMF resins were prepared on a 200‐L pilot plant reactor according to the standard, optimized and slightly modified procedures. In all cases, properties of resins prepared were similar to those which were prepared in a small scale equipment. The scaling up from the 10‐ to the 200‐L reactors was based on a constant agitator tip speed.
Cellulose molecular weights determined by viscometry
Authors: Evans Robert , Wallis Adrian F. A.
Published: April 2003

The equation suggested in the standard method SCAN C15:62 for the estimation of the degree of polymerization (DP) of a cellulose sample from its intrinsic viscosity ([η]) in cupriethylenediamine hydroxide (cuene) solution, P0.905 = 0.75 [η]/mL g−1, where P is an indeterminate average DP, is incorrect. Although differences between the experimental results from several laboratories need to be resolved, a tentative replacement (PV = 1.65 [η]) is suggested, based upon the pooled data and a conversion from the intrinsic viscosity of cellulose tricarbanilate (CTC) in tetrahydrofuran (THF) to that of cellulose in cuene. The treatment of statistical errors in Mark–Houwink–Sakurada parameters, and the nonlinearity of the log[η]−log Pv correlation are discussed.
Attenuated total reflectance (ATR) study of polymer blend films
Authors: Popli R. , Dwivedi Anil M.
Published: April 2003

Variable angle ATR was used to obtain a compositional depth profile of films cast from the blend solutions. Blend solutions were prepared from a colloid of high molecular weight styrene–acrylate–methacrylic acid copolymer, an alkali‐soluble styrene–acrylic acid resin neutralized with ammonia and a colloid of copolymer of propylene. Films obtained from drying the blend solutions show a nonhomogeneous distribution of three polymers through the film thickness. This inhomogeneity cannot be explained solely on the basis of sedimentation effects due to density differences between three polymers. Experimental results of ATR using germanium and KRS‐5 crystals are compared to provide estimates of the distance over which nonhomogeneous composition occurs.
Investigation on multiphase polymeric systems of poly(vinyl chloride). I. PVC–chlororubber‐20‐gp‐styrene–acrylonitrile (2 : 1) blends
Authors: Singh Y. P. , Singh R. P.
Published: April 2003

A graft copolymer [chlororubber‐20‐gp‐styrene–acrylonitrile (2 : 1)] has been synthesized by a solution precipitation polymerization technique grafting styrene and acrylonitrile onto chlororubber‐20 main chain. The graft copolymer has been characterised by elemental analysis, IR spectroscopy, and viscometry. It has been blended with PVC by melt mixing using a Brabender plasticorder and extrusiograph. The mechanical properties such as flexural and tensile strengths and impact strength of the blends have been studied to evaluate its performance as an impact modifier. The behavior of PVC–chlororubber‐20‐gp–styrene‐acrylonitrile (2 : 1) blends has also been compared with PVC–chlororubber‐20 and PVC–KM‐365B (a commercial acrylate modifier) blends. The thermal behavior of these blends has also been studied. It has been found that PVC–chlororubber‐20‐gp‐styrene–acrylonitrile (2 : 1) blends have higher impact strength than PVC–chlororubber‐20‐gp blends though the PVC–KM‐365B blends have the highest impact strength. Based on the authors' previous compatibility studies along with present X‐ray diffraction studies and the morphological investigation of the fractured surface by scanning electron microscopy, the mechanical behavior of these blends have been explained in the framework of existing theories. A model has been proposed to account for the optimum dispersion and adhesion of graft polyblends of chlororubber‐20 in PVC matrix.
Estimation of polymer crystallinity by dynamic mechanical techniques
Authors: Khanna Y. P.
Published: April 2003

Dynamic mechanical techniques can be used for a rapid estimation of polymer crystallinity with an accuracy of better than ±20%. The advantage of our proposed procedure is that it is absolute and the crystallinity can be instantaneously estimated when the dynamic mechanical analysis (DMA) data is available. A serious limitation is its applicability to crystallizable polymers (e.g., a quenched nylon 6) where higher values are obtained due to crystallization during the DMA experiment. Another limitation is that our technique cannot be applied to as polymerized samples, e.g., powders or pellets; only fabricated products such as films, fibers, or plaques are suitable for this determination using DMA. Using a variety of polymer systems, the underlying principle, advantages, disadvantages, and recommendations on crystallinity evaluation by DMA are presented. At present we consider this method to be more of a different approach rather than value it as a crystallinity measurement technique, especially for quenched polymers.
Photodegradation of rigid PVC formulations. II. Spectral sensitivity to light‐induced yellowing by polychromatic light
Authors: Andrady Anthony L. , Searle Norma D.
Published: April 2003

The wavelength sensitivity of a compounded extruded rigid poly(vinyl chloride) formulation to yellowing under exposure to filtered xenon radiation is determined using a cut‐on filter technique. Spectral sensitivity of the formulation in the absence and the presence of 2.5 phr of rutile titanium dioxide was examined, and the results were compared to those previously reported for the yellowing of an identical vinyl formulation exposed to monochromatic light. Maximum in the activated spectrum for yellowing under exposure to filtered xenon radiation was found to be in the wavelength region 300–320 nm for both types of samples. The results agreed qualitatively with those previously obtained in the study of the same material exposed to monochromatic light.
Interaction of dyes with chitosan derivatives
Authors: Seo Toshihiro , Hagura Shigeki , Kanbara Takaki , Iijima Toshiro
Published: April 2003

The states of water in N‐acylated, both aliphatic and aromatic, chitosan gels were investigated by DSC technique. The amounts of two states of water, freezable and nonfreezable water, were found to depend on the chemical and physical structure of the gels. The interaction between these hydrophobic gels and the dyes which have been designed and prepared to carry the ionic, hydrophilic, and hydrophobic nature was determined in detail. The dyes having OH, N(C4H9)2, and naphthalene nucleus show a remarkable increase of the equilibrium sorption to compare with that of methyl orange. The contribution of the electrostatic, hydrophobic, and hydrogen bonding interaction in the sorption was discussed. The predominant contribution of the hydrophobic interaction in the systems of butyl orange/N‐octanoyl chitosan gels has been made clear by means of the temperature dependence of the sorption.
Fatigue fracture of reaction injection molded (RIM) nylon composites
Authors: Martin D. C. , Novak G. E. , Wyzgoski M. G.
Published: April 2003

This study was undertaken to determine how milled glass fibers affect the fatigue resistance of reaction injection molded (RIM) nylon 6. Specifically the effects of glass content, fiber length, orientation, and surface treatment were investigated. The fatigue crack growth rates for unfilled and glass‐filled samples were observed to follow the well‐known Paris equation in terms of dependence on cyclic stress intensity factor. For the unfilled nylon a line shaped zone was observed in advance of the crack tip. Fractography results suggest that the zone was the projection of the actual crack tip profile through the thickness of the sample rather than a distinct plastic or deformation zone. The fatigue fracture surface exhibited a patchy type structure with features 50–150 μm in size, suggesting a void coalescence type of mechanism as has been reported for injection molded nylons. A diffuse damage zone, several millimeters in size, was observed at the crack tip for the glass‐filled RIM nylon 6. The zone was observed to pulsate with the applied oscillating load. The growth of the damage zone volume with increasing crack length (and thus increasing stress intensity factor range) followed the Paris law, as did the crack growth rate data. The damage mechanism is attributed to void formation and microcracking at the fiber–matrix interface. The results of this study show that, for milled glass‐reinforced RIM nylon 6, the crack growth rates were much more rapid than observed for injection‐molded nylon 6 containing chopped glass fibers. This difference is attributed to the greatly reduced glass fiber lengths for the milled glasses.
A kinetic study of benzoyl peroxide decomposition in graft copolymerization bath
Authors: Sójka‐Ledakowicz J. , Ledakowicz S.
Published: April 2003

The rates of decomposition of benzoyl peroxide have been studied in water alone and in the presence of the components of graft copolymerization bath, viz. diphenyl and acrylic acid, in the temperature range of 363–403 K. Kinetic parameters such as reaction order for the peroxide, preexponential factor, and activation energy were evaluated from experimental data. The implication of these results to the initiation of graft copolymerization of acrylic acid onto polyester fabrics is discussed.
ESR and DSC study of the radiation crosslinking effect on macroradical decay in poly(vinylidene fluoride)
Authors: Klimová M. , Szöcs F. , Bartoš J. , Vacek K. , Pallanová M.
Published: April 2003

The decay of polyenyl macroradicals in irradiated poly(vinylidene flouride) and its dependence on radiation crosslinking was studied by the ESR method. The decay rate constants were found to decrease in the lower temperatures region but they show some anomaly at higher temperatures with respect to radiation dose. Temperature dependences of kinetic constants are correlated with thermodynamic parameters from DSC measurements and are interpreted as a result of the steric hindrances changes on molecular mobility due to structural changes caused by radiation crosslinkings and phase transition in a semicrystalline matrix.
Measurement of diffusion of antioxidants in isotactic polypropylene by isothermal differential thermal analysis
Authors: Schwarz T. , Steiner G. , Koppelmann J.
Published: April 2003

The diffusion of the phenolic antioxidant 1,3,5‐tris(3,5‐di tert‐butyl‐4‐hydroxybenzyl)mesitylene (IRGANOX 1330) in extruded sheets of isotactic polypropylene (iPP) was investigated over the temperature range from 80 to 120°C by isothermal differential thermal analysis (DTA). The measurements showed a clear relation between oxidation induction time and oxidation maximum time (both determined by isothermal DTA) and the concentration of stabilizer. It was possible to calculate the diffusion coefficients and the activation energy of diffusion of IRGANOX 1330 in iPP by measuring the oxidation maximum times across stacks of isotactic polypropylene sheets.
Crosslinking structure of keratin. II. Intermolecular and intramolecular crosslinks in potassium‐cyanide‐treated wool fibers
Authors: Arai Kozo , Sakamoto Munenori , Naito Sachio , Takahashi Toshie
Published: April 2003

The crosslinking structure of keratin fibers has been investigated. The reaction of wool with aqueous KCN was studied by means of chemical and physical methods. Quantitative conversion of disulfide (SS) groups of the cystine (Cys) residues into stable thioether (S) linkages was confirmed. In terms of mechanically effective and noneffective crosslinkages, the amounts of intermolecular and intramolecular crosslinks in the KCN‐treated wools were determined from the analysis of the corresponding amino acids and mechanical experiment in which the shear modulus of swollen, rubberlike samples is determined from the relation between equilibrium stress and strain for simple extension of the fiber in a diluent. A modified elastic equation of state was used for the calculation of the number of intermolecular crosslinks. The front factor in the equation used was determined by combining the results obtained from purely chemical kinetics and the values of shear modulus of the swollen wools. The ratio of the number of intermolecular and intramolecular SS crosslinkages in the Lincoln wool, was found to be 64:36. The reactivity of the former is much higher than that of the latter, and these two types of SS crosslinks form substantially the same type of S crosslinks. The fraction of the Cys residues accessible to cyanideions depends mainly on the reaction temperature.
Separation of poly(styrene–methyl methacrylate) block copolymers by liquid adsorption chromatography
Authors: Mori Sadao
Published: April 2003

Block copolymers P(S‐b‐MMA) prepared by using polymeric peroxide as an initiator were separated into three peaks using silica gel as an adsorbent and a mixture of chloroform and ethanol as the mobile phase. The first peak included both polystyrene homopolymer and P(S‐b‐MMA), the second peak appeared to be P(S‐b‐MMA), and the third consisted of P(S‐b‐MMA) and poly(methyl methacrylate) homopolymer. These results suggest the presence of three different block copolymers in composition and/or in structure. By removing the two homopolymers, it was found that the P(S‐b‐MMA) sample prepared in this work consisted of two components of equal amount: One was a block copolymer having a smaller MMA content and smaller molecular weight averages and the other having a higher MMA content (similar to the monomer feed ratio) and higher molecular weight. Besides these two components, one minor copolymer, which might be different from these two components but rather similar to the first one in both composition and molecular weight, appeared between these two peaks in a liquid adsorption chromatogram. These three components had both composition and molecular weight distributions.
Dielectric properties of halar, an alternating copolymer of ethylene and chlorotrifluoroethylene
Authors: Khanna Y. P. , Taylor T. J. , Chandrasekaran S.
Published: April 2003

Dielectric properties of Halar, a predominantly alternating 1 : 1 copolymer of ethylene (E) and chlorotrifluoroethylene (CTFE), have been obtained as a function of temperature (−100 to +175°C), frequency (102–106 Hz), and thermal history. The dielectric loss index (ε″), related to heat dissipation in electrical applications, shows no major change between 25 and 175°C. However, a significant increase in (ε″) between +25°C and −100°C is not considered detrimental for the applications. Activation energies (δE) for the three major relaxations (α‐, β‐, and γ‐) in both mechanical and dielectric experiments are similar, thus suggesting a similar phase origin of the molecular relaxations in the two techniques. In dielectric analysis, the lowest temperature γ‐relaxation is the strongest while it is the weakest in mechanical technique. It is proposed that, in dielectric experiments, only the CTFE groups participate and due to restricted mobility at low temperatures (i.e., γ‐relaxation), the dissipation factor or relaxation strength is maximum.
Test methodology for the determination of optimum fusion welding conditions of polyethylene
Authors: Saint‐Royre D. , Gueugnaut D. , Reveret D.
Published: April 2003

The fusion welding behavior of a medium density polyethylene resin has been studied for a wide range of heating rates using a recently developed test methodology. With this method, the thermal and physical phenomena occurring at the interface of two thin polyethylene pieces assembled by fusion can be studied. It consists of a thermal welding phase and a phase of mechanical separation of the welded assembly. For the mechanical phase, an adaptation of the T‐peel test was used. These conditions make it possible to determine the thermal welding parameters (temperature, time) for optimal mechanical quality of the joint, according to a criterion established by optimization of the peel test used. The variations in minimum temperature required for an optimum weld, as a function of heating rate, can be simulated with a numerical model based on the concept of macromolecular interdiffusion. Consistent with the experimental behavior, the numerical model involves two parameters characteristic of the diffusion behavior of the polyethylene resin. Thus, these parameters characterize the weldability of the polyethylene resin under study.
Insoluble poly(akylarylphosphine)siloxanes and their application as supports for catalytic transition‐metal complexes
Authors: Ejike E. N. , Parish R. V. , Jideonwo A.
Published: April 2003

Light induced addition of diphenylphosphine (DPP) to methylvinylcyclotetrasiloxane (MVS) yielded poly(2‐diphenylphosphinoethyl) cyclotetrasiloxane (DPPS). Similar treatment of allyldiphenylphosphine (ADPP) with linear poly(methylhydrogenosiloxane)‐co‐hexamethyldisiloxane (PMS) led to formation of poly(3‐diphenylphosphinopropyl)methylsiloxane‐co‐hexamethyldisiloxane (PPMS). DPPS and PPMS were condensed by acid treatment to give insoluble rubbery phosphine bearing materials P1 and P2, respectively. Iridium and rhodium complexes were immobilized on P1 and P2. The ability of a high molecular weight substrate (PMS) to migrate to active catalytic centers within support matrix was examined. The effect of varying metal: phosphine ratio and total percentage metal on the support were examined during catalysis of O‐silylation of ethanol with PMS and triethoxysilane (TES).
Laminar and turbulent flow continuous interfacial polycondensations of nylon 66
Authors: Griskey Richard G. , Patel C. A.
Published: April 2003

The interfacial polycondensations of nylon 66 in a continuous reaction system have been studied. An experimental stirred flow reactor was used to determine both yield and intrinsic viscosity (molecular weight) as functions of reactant ratio (adipoyl chloride/hexamethylene‐diamine), and Reynolds number from laminar to turbulent flow. It was found that mass transfer was the controlling factor in the reaction system. The yield as a function of Reynolds number was found to directly correlate with the behavior of the combination of mass transfer coefficient and interfacial area. Intrinsic viscosity had maximum values in the same reactant ratio range as for batch and continuous cascade systems studied earlier. Intrinsic viscosity behavior was shown to relate to interfacial area behavior.
Thermoplastic composties of polystyrene: Effect of different wood species on mechanical properties
Authors: Maldas D. , Kokta B. V. , Daneault C.
Published: April 2003

Both softwood (spruce) and hardwood (aspen and birch) species in the form of different pulps (e.g., sawdust, chemithermomechanical pulp, explosion pulp and OPCO pulp) have been used (10–40 wt% composite) as reinforcing fillers for thermoplastic composites of polystyrene. Mechanical properties, are examined, e.g., tensile modulus, tensile strength at maximum point, and the corresponding elongation and energy as well as impact strength of compression molded composites. To improve the compatability of wood fibers which are hydrophilic and the polymer matrix which is hydrophobic, poly[methylene(polyphenyl isoeyanate)] (2 and 8 wt % of polymer) was used as a coupling agent. The mechanical properties of the treated composites are improved up to 30% in fiber content whereas a downward trend for untreated composites was observed when an increase in fiber content occurred. The overall improvements in mechanical properties due to the addition of isocyanate can be explained by the linkage of isocyanate molecules with fiber matrix through the chain of covalent bonds and the interaction of π‐electrons of benzene rings of polystyrene as well as isocyanate. As a result, poly[methylene(polyphenyl isocyanate)] forms a bridge between fiber and polymer on the interfaces. This result is instrumental for efficient stress transfer between cellulose fibers and thermoplastics. The performance of different pulps of various wood species as reinforcing fillers for thermoplastic composites is also examined.
Permeation of propane and propylene thrugh cellulosic polymer membranes
Authors: Ito Akira , Hwang Sun‐Tak
Published: April 2003

Cellulosic polymers were tested by measuring their permeabilities of propane and propylene. High permeabilities and selectivities were obtained with ethyl cellulose membranes. Hollow fibers coated with ethyl cellulose were made through a solution coating method. Microporous polypropylene hollow fibers were used as base material. A dense layer of ethyl cellulose about 6–10 μm in thickness was formed on the microporous hollow fiber. The performance of a coated membrane column was tested for the separation of propane and propylene mixture gas. It was concluded that ethyl cellulose membranes have a good potential for the separation of olefins form saturated hydrocarbons.
The morphology of fracture surfaces and mechanical properties of composites of polypropylene with glass fibers having different interface adhesion
Authors: Sova Miloš , Pelzbauer Zdeněk
Published: April 2003

For composites polypropylene–short glass fibers having different interface adhesion, correlation has been proved to exist between the morphology of fracture surfaces, the temperature dependence of impact strength, and the deformational and fracture behavior in tensile loading. The results are interpreted in terms of the mechanism of distortion plasticity for unfilled PP and for filled PP having weak interface adhesion, and on the basis of dilatation plasticity for filled polypropylene with a higher interface adhesion. The transition from the distortion to the dilatation mechanism can be seen in fracture surfaces after tensile destruction in composites possessing a higher interface adhesion.
A method for the calculation of compositions of radical‐chain copolymerizations
Authors: Kuo Jen‐Feng , Chen Chuh‐Yung , Luo Shieh‐Huang , Pan Ting‐Chung
Published: April 2003

In this article the straight‐line relationship between In A and B, where A and B denote the concentrations of the two types of monomers in any reaction period, is examined to exist in the radical copolymerizations of 1.02 ≥ r1r2 ≥ 0.25. Utilizing this observation, we propose an easy‐to‐use compositions calculation method in which a single empirical parameter is included. The method is derived without involving the constant monomer reactivity ratios assumption. The copolymerizations of styrene–methyl methacrylate vinyl chloride–vinyl acetate, methyl methacrylate–vinyl acetate, acrylic acid–acrylamide, methacrylic acid–methacrylamide, and sodium methacrylate–methacrylamide are investigated. The instantaneous and cumulative copolymer compositions and the residued monomer compositions computed by this proposal are in very good agreement with the experimental data.
Gas transport in poly[bis(trifluoroethoxy)phosphazene]
Authors: Hirose Takuji , Kamiya Yoshinori , Mizoguchi Keishin
Published: April 2003

The gas transport parameters of 14 gases in poly[bis(trifluoroethoxy)phosphazene] were determined at temperatures ranging from about 12 to 45°C by the time‐lag method. The phosphazene polymer demonstrated a high diffusivity; rather high crystallinity was expected, though. The permeation data determined were between polydimethylsiloxane and low‐density polyethylene. The most interesting characteristic shown over the course of experimentation is that poly[bis(trifluoroethoxy)phosphazene] has significantly high solubility for CO2, as compared to other gases. The polar side groups—i.e., the electron‐withdrawing trifluoroethoxy parts—which should contribute specific interaction with CO2, were shown to be stronger than their interaction with the polar N2O molecule. The sorption behavior is compared with those of other rubbery polymers, while phosphazene polymer characteristics are also discussed.
Dielectric relaxations in poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate)
Authors: Ribelles J. L. Gómez , Dueñas J. M. Meseguer , Pradas M. Monleón
Published: April 2003

A comparative study is undertaken of the dielectric relaxation spectra of poly(methyl acrylate), poly(ethyl acrylate), and poly(butyl acrylate), taking into consideration the spectra of the corresponding polymers in the series of the polymethacrylates. The three polymers, PMA, PEA, and PBA, present an α relaxation zone clearly separated from the secondary relaxations. Its shape is not altered with temperature, and it is possible to construct a master curve. With increasing length of the side chain, its distribution of relaxation times broadens and the temperature of the maximum of the relaxation decreases. A β relaxation with decreasing intensity as the length of the side chain increases is clearly perceptible in PMA and PEA, but almost not perceptible at all in PBA. In PEA this relaxation appears split into two peaks. Computer simulation of restricted motions of the side chain discard an origin similar to that of the γ relaxation in PPA or PBA for the lowest temperature component of the relaxation, and suggests the conjunction of two rotation mechanisms in this relaxation for the polyacrylates. For the experimental temperatures of our tests a γ relaxation shows up only in PBA. Its apparent activation energy, higher than in related polymers of the polymethacrylate series, suggests that the tighter packing of monomeric units in polyacrylates leads to a significant increase in the intermolecular contribution to the potential energy barrier responsible for the relaxation.
Ultrafiltration membranes obtained by grafting hydrophilic monomers onto poly(vinyl chloride)
Authors: Vigo Fernando , Uliana Claudio
Published: April 2003

The grafting of vinylacetate (VAc) or hydroxyethylmethacrylate (HEMA) onto poly(vinyl chloride) (PVC) has been performed by means of γ‐rays or chemical initiators. The grafted polymer so obtained has been separated by selective extraction and submitted to IR spectroscopy in order to check the amount of grafting. The grafting percentage was measured as a function of the grafting conditions. Using the above‐mentioned polymer, dissolved again in DMF, asymmetric ultrafiltration membranes have been prepared by the phase inversion technique. The membranes have been tested with Dextran solutions. Their performances have been studied as functions of the grafting amount. The values of rejection and permeating flux demonstrated the effectiveness of the treatment in enhancing the performances of PVC ultrafiltration membranes.
The preparation of small polystyrene latex particles
Authors: Brouwer W. M.
Published: April 2003

The effects of several variables in the preparation of small‐sized polystyrene latex particles are described. A semicontinuous preparation using microlatexes obtained by microemulsion polymerization as a seed is compared with a batchwise preparation employing the same ingredients. The particles in the batch products prove to be slightly larger in size but are more narrowly distributed. Furthermore, the effects of both the surfactant type and the ionic strength on the particle size in the batchwise emulision polymerization of styrene are reported. The systems do not obey the linear Smith–Ewart relationship with respect to the micellar surfactant concentration, although in the microemulsion polymerization of styrene the Smith–Ewart relationship is found to be valid with respect to the initiator concentration. Surfactants with a low critical micelle concentration increasingly promote the formation of smaller particle sizes. Salt is found to decrease the particle size when using a strong adsorbing surfactant. However, in the case of a weak adsorbing surfactant, an increase in particle size has been observed above a certain salt concentration.
The supermolecular structure of poly(vinyl chloride)–poly(methyl methacrylate) blends
Authors: Włochowicz Andrzej , Janicki Jarosław
Published: April 2003

Investigations of the supermolecular structure of PVC/PMMA blends, covering a wide range of composition, are presented. It was found that a transition layer exists between PVC and PMMA phases. The thickness of the transition layer is independent of blend composition. The scattering intensity distribution function for blends is characteristic of isotropic, amorphous systems with a completely random distribution of phases. It was shown that scattering intensity distribution function may be used for calculation of a distribution, which corresponds a two‐phase system with sharp phase boundaries. Values of correlation lengths, inhomogeneity lengths, and specific surfaces were then calculated. A model of the supermolecular structure of PVC/PMMA blend was finally proposed.
Synthesis and some properties of anthracene and anthraquinone incorporated poly(vinyl chloride) and the ion exchange resin therefrom
Authors: Biswas Mukul , Majumdar Amitava
Published: April 2003

Poly(vinyl chloride) has been modified by chlorine displacement reaction with 2‐anthrol and anthraquinone‐2‐ol. The condensates (PVC‐ACOL and PVC‐AQOL) are insoluble in all solvents common to PVC and have been characterized by elemental and IR spectra analysis. The initial decomposition temperature of these condensates follow the trend: PVC‐AQOL (250°C) > PVC‐ACOL (200°C) > PVC(190°C) and the overall thermal stabilities beyond 60% decomposition follows the same trend. Permittivity and dielectric loss of these condensates sharply fall with increasing applied frequency (10–1.3 ×107 Hz) to a limiting constant value. In contrast, for unmodified PVC these values are low and remain independent of frequency in the same range. Sulfonation of these PVC condensates affords a weak acid resin with COOH and OH ionogenic groups, but no strong sulfonic acid groups due presumably to oxidative degradation of the PVC matrix.
Radiopaque miscible systems composed of poly(methyl methacrylate) and transition and nontransition metal salts: Spectroscopic, thermal, and radiographic characterization
Authors: Cabasso Israel , Smid Johannes , Sahni Suresh K.
Published: April 2003

The preparation of miscible systems containing poly(methyl methacrylate) and cupric nitrate, manganese chloride, praseodymium chloride, and uranyl nitrate is described. The salt was dissolved in the monomer, which was subsequently polymerized. The heavy metal salts impart radiopacity to these plastics and this renders them useful for X‐ray imaging in applications such as medical implants. The polymer–salt systems are characterized on the basis of their infrared spectra, thermal, and radiographic properties, and the formation of complexes between the cations and the carbonyl function of the polymer is discussed. The glass transition temperatures of the salt‐containing polymers are higher than those of the salt‐free polymers, the elevation being dependent on the nature and concentration of the metal salt. Miscible PMMA–uranyl nitrate systems are transparent, glassy plastics and approximately 11 wt % of uranyl nitrate hexahydrate imparts a radiopacity equivalent to that of aluminum.
A comprehensive approach to the stereochemical and physical factors in nucleophilic substitution on PVC in the melt
Authors: Mijangos C. , Gómez‐Elvira J. M. , Martínez G. , Millán J.
Published: April 2003

The nucleophilic substitution reactin of poly(vinyl chloride) (PVC) with sodium benzenethiolate (NaBT) has been studied in the melt with the aim of determining whether a conformational mechanism is applicable under conditions that would apply in the polymer processing. The evolution of unreacted syndio, hetero, and isotactic triads content, and of the apparent molecular weight has been followed by 13C‐NMR and GPC, respectively. The kinetic behavior was defined by choosing appropriate mixing conditions of temperature, shear stress, load, and amount of plasticizer. In all cases the kinetic curves attain a plateau after a rather fast reaction period has elapsed. The conversion at the plateau, that is, the reaction efficiency, proved to depend linearly on the amount of nucleophile and is hardly influenced by the mixing conditions for a given stoichiometric composition. The mixing conditions have been found to affect markedly the kinetics but to be quite inoperative on the evolution of both the content of unreacted tactic triads and the apparent molecular weight with degree of conversion. The results are discussed by taking into consideration those previously obtained in solution.
Halogen‐induced chemical copolymerization of pyrrole with N‐methylpyrrole
Authors: Neoh K. G. , Kang E. T. , Tan T. C. , Tan K. L.
Published: April 2003

Simultaneous chemical copolymerization and oxidation of pyrrole and N‐methylpyrrole by bromine an iodine has been carried out. The composition of the copolymes can be effectvely controlled by varying the monomer feed ratio. From elemental analysis the copolymer composition and the monomer reactivity ratios have been determined. As the copolymer composition changes, the IR absorption spectra show changes in the intensity of certain bands. In bromineinduced polymerization, the electrical conductivity, the electrical conductivity, thermal stability, and bromine content of the copolymer complex decrease with increase in N‐mthylpyrrole fraction. X‐ray photoelectron spectroscopy data suggest that a fixed fraction of bromine is incroporated as covalent bromide in the copolymer complex. When iodine is used the halogen content do not show substantial differences among the copolymers but the electricdal conductivity and thermal stability of the copolymers also decrease with increase in N‐methylpyrrole fraction.
Polyaramides containing arylene sulfone ether linkages
Authors: Idage S. B. , Idage B. B. , Vernekar S. P.
Published: April 2003

Polyamides containing arylene sulfone ether linkages were synthesized from 4,4′[sulfonybis (p‐phenyleneoxy)] dibenzoyl chloride (SPCI), 3,3′‐[sulfonylbis (p‐phenyleneoxy)] dibenzoyl chloride (SMCl) and various aromatic diamines (ARD), by solution and interfacial polymerization techniques. In solution polymerization, the effect of various acid acceptors such as propylene oxide (PO), lithium hydroxide (LiOH) in the presence of lithium chloride (LiCl), and triethylamine (TEA) on teh molecular weight of the olyamides was studied. The effect of structure of studied. The effect of structur of various aromatic diamine sof molecular weight and thermal properties of polyamides was also studied. The polyamides prepared were characterized by solution viscosity, elemental analysis thermo‐gravimetric analysis, differential scanning calorimetry, and x‐ray diffraction. Physical and thermal properties of polyamides prepared from SPcl and Ard were compared with the polyamides prepared from SMCl and ARD.
Synthesis, characterization, and propellant binder studies of new polyurethanes
Authors: Kothandaraman H. , Venkatarao K. , Thanoo B. Chithambara , Krishnamoorthy V. N.
Published: April 2003

Hydroxy‐terminated ether‐ and ester‐based prepolymers more suitable for propellant binder applications were prepared from tetrahydrofuran, propyleneoxide, and various discarboxylic acids. Polyurethanes were prepared from these prepolymers with various diisocyanates such as hexamethylenediisocyanate, toluene diisocyanate, and diphenylmethanediisocyanate, and the mechanical properties such as hardness, tensile strength, and elongation of these polyurethane elastomers were compared. The thermal degradation study of these polyurethanes was studied in the atmosphere of oxygen. Composite propellants were formed using these prepolymers as binder resins, toluene diisocyanate as the curing agent, ammonium perchlorate as the oxidizer, and aluminum as the fuel. Propellants having two different solid loadings (85 and 82%) were made and compared with respect to their unloading slurry viscosity and mechanical properties. The tensile strength, elongation, and ballistic performance parameters (theoretical) of these new propellant systems were promising.
Characterization of the isothermal crystallization of poly(ethylene terephthalate) by microhardness measurements
Authors: Pastor J. M. , González A. , De Saja J. A.
Published: April 2003

The two‐stage isomerization isotherms of poly(ethylene Terephthalate) have been followed through microhardness analysis. A great variation in microhardness values seems to prove the increase of the strength and stiffness of the samples produced by the secondary isomerization. A smaller variation is observed for the primary isomerization.