bluuebunny/crossref_metadata_2025 huggingface dataset:
Accelerated hydrothermal weathering of silicone rubber, EPDM, and their blends
Authors: Kole S. , Srivastava S. K. , Tripathy D. K. , Bhowmick A. K.
Published: April 2003

Hydrothermal weathering of the peroxide vulcanized specimens of silicone rubber, EPDM rubber, and their 50 : 50 blend carried out for various durations at different temperatures reveals that silicone is very susceptible to degradation. For example, the modulus, the strength, and the elongation at break consistently fall with aging period. For 72 h of aging at 210°C, it practically loses its rubberiness (elongation < 50%); while EPDM and the 50 : 50 blend maintain more than 100% elongation at break during the times and temperatures. While hydrolytic chain scission is the main degradation mechanism for silicone, EPDM undergoes a predominantly crosslinking reaction. The kinetics study reveals that the better retention of properties of the blends over silicone is due to an increase in the activation energy of degradation in the presence of EPDM rubber, and this protection effect is higher in liquid‐phase weathering than in steam‐phase weathering. © 1994 John Wiley & Sons, Inc.
Gas permeation and sorption in brominated poly(1‐trimethylsilyl‐1‐propyne) membrane
Authors: Nagai Kazukiyo , Higuchi Akon , Nakagawa Tsutomu
Published: April 2003

Brominated poly(1‐trimethylsilyl‐1‐propyne) (Br–PMSP), which was prepared by immersing a poly(1‐trimethylsilyl‐1‐propyne) membrane in bromine water, had a new endothermic peak between 70°C and 80°C in its DSC curves. After storage in air at room temperature,the endothermic peak shifted to the low temperature side with time, and occurred between 30°C and 40°C. A distinct change in slopes near the endothermic temperature determined by the DSC analysis was observed in the Arrhenius plots of the permeability coefficients for various gases in all Br–PMSP membranes. However, the slope's change did not clearly appear with storage under the same conditions. The Br–PMSP membrane had a pressure‐dependence of the permeability coefficients not only below the endothermic temperature, but also above one. The sorption behavior for propane in the Br–PMSP membrane was similar to that for other glassy polymers, and there was little change in the sorption behavior with time. In the case of carbon dioxide, a different behavior was observed at first; that is, the same isotherm shape in glassy polymers appeared below 20 atm, but it showed an upward curve above that. After storage in air, the upward behavior disappeared, and the isotherm showed the general shape in glassy polymers. © 1994 John Wiley & Sons, Inc.
Synthesis of core‐shell emulsion copolymer of poly(butyl acrylate)/α‐methyl styrene‐co‐methyl acrylate, with application as processing aid of poly(vinyl chloride)
Authors: Li Zhiting , Gao Jungang , Deng Kuilin , Zhu Hong Guo
Published: April 2003

The core‐shell grafting copolymer of α‐methyl styrene‐methyl acrylate on poly(butyl acrylate) was synthesized. The particle morphology of latex and core‐shell grafting polymerization was investigated as a function of: (a) reaction temperature; (b) initiator concentration used in the secondary polymerization; (c) monomer to polymer ratio; (d) emulsifier concentration. The compatibility of this copolymer with poly(vinyl chloride) (PVC) was determined by the method of solubility parameter and scanning electron microscopy. The rheological behavior of the blend of this copolymer with PVC was investigated. The mechanical properties of the blend were determined. The results show that this copolymer can be used as processing aid for PVC. © 1994 John Wiley & Sons, Inc.
Dynamic simulation of primary particle‐size distribution in vinyl chloride polymerization
Authors: Kiparissides C. , Achilias D. S. , Chatzi E.
Published: April 2003

In the suspension polymerization of vinyl chloride, colloidally stable primary particles are formed inside the polymerizing monomer droplets. The nucleation, growth, and aggregation of these particles are responsible for the formation of the internal particle morphology and associated properties, such as pore‐size distribution, specific surface area, and plasticizer uptake. In the present investigation, a population balance model is derived describing the time evolution of the primary particle‐size distribution in the polymerizing monomer droplets. The resulting integrodifferential equation accounts for the coalescence rate of electrically charged colloidal primary particles through the use of the Fuchs modification of the extended Smoluckowski coagulation equation. Simulation studies were carried out to determine both the effects of the model parameters and to afford a direct comparison of model predictions with experimental measurements of the time evolution of the primary particle‐size distribution. The dependence of the total number and of the mean diameter of the primary particles on several process variables (i.e., the ionic strength of the medium, total particle charge, temperature, initial initiator concentration, and agitation rate) is quantitatively analyzed. Finally, the predictive capability of the present model is demonstrated by a direct comparison of model predictions with the experimental data of Willmouth et al. and Törnell and Uustalu. © 1994 John Wiley & Sons, Inc.
Attempted synthesis of multiblock copolymers of butadiene, styrene, and α‐methylstyrene: Effect of polar additives on copolymerizations
Authors: Wang L. S. , Phalip P. , Favier J.‐C. , Sigwalt P.
Published: April 2003

Owing to the low Tg of polystyrene, the mechanical properties of polystyrene‐block‐poly‐butadiene‐block‐polystyrene (SBS) thermoplastic elastomers drop steeply above 60°C. To overcome this behavior, many research groups have considered the replacement of styrene (S) by α‐methylstyrene (MS). We also attempted the synthesis of copolymers with a central polybutadiene (poly B) block and rigid blocks consisting of polystyrene (poly S) and poly(α‐methylstyrene) (poly MS) blocks. Starting from a dilithium initiator, difunctional poly B's with low 1,2 content (10%) were prepared and toluene was added. After addition of a small amount of styrene, MS was added in the presence of a 15% (in vol) of THF at T ≤ −40°C. The copolymers did not have the expected structure and poor mechanical properties resulted, which were, however, still measurable at 120°C. These results probably resulted from secondary reactions involving the MS carbanions. To identify these reactions and to control the polymer structure, the synthesis of multiblock copolymers was carried out with a monofunctional polybutadienyllithium to which were added successively S and MS (in a mixture of hexane and benzene as solvent). MS was added at low temperature in the presence of small amounts of THF or at room temperature after addition of TMEDA. These attempts were unsuccessful, the copolymer being always multimodal as a result of unwanted coupling reactions involving terminal double bonds. The synthesis of elastomers using a coupling reaction of poly MS–poly S–poly B was also considered but the yield in poly B was low since termination reactions involving the polar additive occurred. © 1994 John Wiley & Sons, Inc.
Spherulite nucleation in blends of isotactic polypropylene with isotactic poly(butene‐1)
Authors: Bartczak Z. , Galeski A. , Pracella M.
Published: April 2003

The phase morphology and the influence of composition on the primary nucleation of isotactic polypropylene in isotactic polypropylene/isotactic poly(butene‐1) (iPP/iPB) blends were investigated by electron and light microscopy and small‐angle light scattering. It was found that iPP and iPB are miscible but the thermal treatment induces partial phase separation of components and the formation of iPP‐rich and iPB‐rich phases. The complete phase separation needs high temperatures and/or a long time of melt annealing. In samples crystallized isothermally at low undercooling the heterogeneous primary nucleation in blends is depressed as compared to plain iPP. In blends the less active heterogeneities lose their activity because of an increase of the energy barrier for critical size nucleus formation due to phase separation of blend components during crystallization. For the same reason the rate of homogeneous nucleation in blends decreases, as observed in samples crystallized at very high undercooling. At very high undercooling iPP and iPB are able to crystallize with similar rates, which results in the formation of a fraction of iPB spherulites in addition to iPP spherulites. Consequently the number of spherulites in the blend is larger than that in plain iPP, in spite of the decrease in the homogeneous nucleation rate of iPP in the blend. © 1994 John Wiley & Sons, Inc.
Temperature dependence of pH for solubilized collagen solutions
Authors: Matsushita Satoru , Deki Shigehito , Mizuhata Minoru , Sugita Masami , Kanaji Yukio
Published: April 2003

The temperature dependence of the pH for an acid‐soluble collagen in solution was measured, so that the pH largely increased in the temperature region including ca. 40°C of the thermal denaturation temperature. As the changes of the optical rotation, αD, and the electrical conductivity, σ, were observed in this temperature region, the change of the pH is due to the thermal denaturation of collagen. The differential curve of pH vs. t gave clear deflection points and a large peak at ca. 40°C. The thermal denaturation temperature, td, could be estimated from the peak temperature. The td obtained by the measurement of the αD, tdαD, decreased with the decrease in the heating rate and with the increase in the concentration of collagen. However, the td obtained through the measurement of the pH, tdpH, was independent of the variations of the heating rate and the concentration of collagen. These measurements were carried out for different kinds of collagens prepared by various methods. Some of them had one kind of peak; others had two kinds of peaks. The tdpH correlated with the tdαD for different kinds of collagen preparations. Therefore, the measurement of the temperature dependence of the pH was useful for the determination of the td. © 1994 John Wiley & Sons, Inc.
Electrical properties of diphenyldiacetylene annealed under elevated pressure
Authors: Kojima Yoshitsugu , Matsuoka Takaaki , Takahashi Hideroh
Published: April 2003

A unique class of conjugated compounds composed of the derivative of condensed polycyclic aromatic compound with the phenyl group and diphenyldiacetylene oligomer was synthesized by annealing of diphenyldiacetylene under elevated pressure. The effect of annealing pressure on the conductivity of the compounds was studied. The total conductivity of the compound decreased with a decrease of frequency, approaching a constant value (dc conductivity: Cdc). The dc conductivity of the compound increased from below 10−15 to 10 S cm−1 with increasing annealing pressure. The dc conductivity of the oligomer was below 10−15 S cm−1 and that of the derivative increased from 10−8 to 10 S cm−1 with decreasing H/C (H/C:0.45–0.04). The conduction of the conjugated compound was electronic. The temperature coefficient of those dc conductivities was positive, with an approximately linear relation between In (CdcT0.5) and (1/T)0.25, where T is the temperature. The ac conductivities Cac were proportional to temperature and frequency f and had the following equation Cac = TfS, S = 0.67–0.75. These results showed that the conduction mechanism can be explained by the hopping in a manifold of states at the Fermi level. © 1994 John Wiley & Sons, Inc.
Thermally stimulated current and effect of annealing on the electrical properties of cellulose nitrate
Authors: Amin M. , Darwish K. A. , Mounir M. , Elez M. Abu
Published: April 2003

The investigated samples were of cellulose nitrate CA‐80‐15. The dc conductivity (σ) and the dielectric permittivity decreasd with increasing time of annealing. The activation energy is 0.46 eV in a temperature range from 298 to 385 K. The thermally stimulated current (TSC), JD, was measured. The maximum value of the TSC (Jm) increases with increasing the rate of heating and shifts slightly toward higher values of temperature. The activation energy (0.25 eV) is independent of the variation of the rate of heating. In addition, the peak positions for the constant rate of heating were unaffected by increasing the polarization time, but the maximum value of the current increases and the activation energy decreases. The dipolar relaxation time was calculated theoretically and studied as a function of temperature. © 1994 John Wiley & Sons, Inc.
Plasma polymerized membranes from organosilicon compounds for separation of oxygen over nitrogen
Authors: Matsuyama Hideto , Shiraishi Tomoyuki , Teramoto Masaaki
Published: April 2003

Plasma polymerized membranes were prepared from octamethyltrisiloxane for the purpose of separation of O2 over N2. The obtained membrane consisted of plasma prepared polymer layer on top of a porous polyproplene substrate. The membrane polymerized under the mild plasma condition (low power input and high monomer flow rate) showed the high permeation rate. Selectivity, however, was hardly affected by the plasma conditions. The selectivity and permeation rate obtained were 2.6 and 2.5 × 10−10 kmol/(m2·s·Pa) (=7.5×10−4 cm3/(cm2·s·cmHg)), respectively. This high permeation rate was attributed to the use of the monomer with the long, flexible siloxane chain and the mild plasma condition. Moreover, the membranes were prepared from a series of monomers with different siloxane chain lenghts (methoxytrimethylsilane, hexamethyldisiloxane, and octamethyltrisiloxane), and from those with different alkyl chain lenghts (methoxytrimethylsilane, propoxytrimethylsilane, and hexyloxytrimethylsilane). As the siloxane chain lenghts of the starting monomers increased and the alkyl chain lengths decreased, the permeation rates of the corresponding polymers increased. The selectivities were nearly constant regardless of the difference in the starting monomer structures. The structures of the plasma prepared polymers were analyzed by XPS and IR measurements, and discussed in relation to the membrane efficiencies. © 1994 John Wiley & Sons, Inc.
Dynamic properties of short fiber–EPDM matrix composites as a function of strain amplitude
Authors: Ibarra L.
Published: April 2003

The dynamic properties of composite materials consisting of an ethylene–propylene rubber matrix (EPDM) and short polyester polyethylene‐terephthalate (PET) fiber vary with dynamic stress amplitude applied to the material. These variations support the statement that fiber treatment with 1,4‐carboxy‐sulphonyl‐diazide, which acts as a bridge between the fiber and the matrix and hence enhances the strength of the interface enabling it to resist greater strain applied to the composite and, as a consequence, yielding greater retention values of the storage modulus, measured longitudinally to preferential fiber orientation, E′L. By means of transversal measurements of the storage modulus, E′T, of these materials it is possible to determine a parameter b, which eventually indicates the degree of matrix–fiber bonding and which is consistently higher for materials filled with surface‐treated fiber. This enhanced phase adhesion is further confirmed by higher equivalent interfacial thickness values, ΔR, which, in addition, vary less with increasing dynamic strain amplitude. Finally dissipated energy variation or mechanical energy loss, Eloss, is studied as a function of fiber content and strain amplitude. Experimental findings show Eloss to increase with fiber content and strain amplitude, when measured at constant strain amplitude ϵ0, and to yield higher values for treated fiber samples. © 1994 John Wiley & Sons, Inc.
Polylactide. II. Discontinuous dry spinning–hot drawing preparation of fibers
Authors: Horáček I. , Kalíšek
Published: April 2003

The mechanical properties and morphology of poly(L‐lactide) fibers, prepared by the dry spinning–hot drawing process using different nonsolvent/chloroform spinning solutions, were studied in relation to fiber in vitro degradability. Acetone, methanol, ethanol, and cyclohexane were used as nonsolvents in the spinning mixture with as‐polymerized PLLA, i.e., PLLA containing 10% of residual L‐lactide. The tensile strength, structure, and degradability of obtained fibers were mainly governed by the nonsolvent volatility. Generally, the higher the volatility, the higher the strength, and the faster the degradation. The acetone/chloroform spinning system produced fiber with an increased degradation rate in comparison to the pure chloroform spinning system. © 1994 John Wiley & Sons, Inc.
Solid‐phase oxidation of polyethylene coatings on metals
Authors: Lin Dmitry G.
Published: April 2003

The paper considers the problem of solid‐phase oxidation for cases of polyethylene coatings applied onto active (copper) and passive (aluminum) substrates. Oxidation of PE coatings on copper, unlike that of PE coatings on aluminum, is shown to develop in two stages separated by a time period of autoinhibition. During this time period the concentration of carboxyl groups does not in fact change. In a similar manner copper‐containing compounds accumulate in the coating, which fact supports the relation between metal transfer and polymer oxidation processes. © 1994 John Wiley & Sons, Inc.
Influence of water uptake on the mechanical properties of jute fiber‐reinforced polypropylene
Authors: Karmaker A. C. , Hoffmann A. , Hinrichsen G.
Published: April 2003

Jute fiber‐reinforced polypropylene composites have been produced and characterized in order to investigate the influence of water on their mechanical properties. Being hydrophilic, jute fibers absorb a high amount of water causing swelling of fibers. On the other hand, the thermal shrinkage of polypropylene melt leaves some gaps between jute fibers and matrix material. We investigated whether these gaps could be filled by the swelling of wetted fibers. The fillup of these gaps would result in a higher shear strength between fibers and matrix during fracture. Our results suggest that swelling of jute fibers in a composite material can have positive effects on mechanical properties. © 1994 John Wiley & Sons, Inc.
Synthesis, properties, and morphology based on polyurethane and polymethyl methacrylate AB‐crosslinked copolymers
Authors: Zhang Liucheng , Pan Mingwang , Tai Huiwen , Li Xiucuo
Published: April 2003

The AB‐crosslinked copolymer was prepared as a transparent material from toluene diisocyanate (TDI) or hexamethane diisocyanate (HDI), triethylene glycol (TEG), hydroxyethyl methacrylate (HEMA), and methyl methacrylate (MMA). The optical transmission, impact resistance, thermal mechanical properties, and morphology of the copolymer were studied. The results indicate that this material has a microheterogeneous structure with the dispersed phase size no more than 0.1 μm. © 1994 John Wiley & Sons, Inc.
Thermal and structural analysis of heparin–PEO–PDMS–PEO–heparin pentablock copolymers
Authors: Kim Yong Joo , Sung Yong Kiel , Piao Ai Zhi , Grainger David W. , Okano Teruo , Kim Sung Wan
Published: April 2003

ABCBA‐type amphiphilic block copolymers comprising polydimethylsiloxane (PDMS), poly(ethylene oxide) (PEO), and heparin segments were synthesized by coupling reactions between end‐functionalized oligomers. These multiblock copolymers were characterized to examine bulk properties using 1H‐NMR, FTIR, end‐group analysis, and sulfur elemental analysis. Block copolymers were further characterized in bulk using differential scanning calorimetry and X‐ray diffraction measurements. The PDMS glass transition remains unchanged with increasing PEO content, indicating coexistence of pure PDMS with mixed phases. Furthermore, endothermic melting of the block copolymers shifts to higher temperatures and becomes more intense with increasing PEO molecular weight. Additionally, the crystallinity of the PEO segment in the block copolymers increases with increasing PEO molecular weight. The PEO melting endotherm peak shifts from near 318 to 323 K with annealing. In the cooling thermogram, the block copolymers exhibit two crystallization exotherms, one near 303 K and the other near 193 K, attributed to PEO and PDMS recrystallization and nucleation, respectively. © 1994 John Wiley & Sons, Inc.
Preparation of new synthetic hydrogels containing galactose, applicable in affinity chromatography
Authors: Alvarez C. , Bertorello H. , Strumia M.
Published: April 2003

New biospecific affinity chromatography adsorbents were prepared from epoxy reactive matrices with subsequent coupling of galactose as the ligand and were afterward characterized. Their usefulness in the sorption of peanut lectin, a protein specifically retained by the galactose residue, is reported. © 1994 John Wiley & Sons, Inc.
Composition control in emulsion copolymerization. I. Optimal monomer feed policies
Authors: Canu Paolo , Canegallo Stefano , Morbidelli Massimo , Storti Giuseppe
Published: April 2003

The problem of producing polymers with constant instantaneous composition in semibatch reactors has been addressed in the most general terms. A rigorous procedure for determining a priori the monomer feed policy that allows one to produce, with a minimum reaction time, a given amount of polymer, with constant instantaneous composition and complete monomer depletion, has been developed. The procedure involves the knowledge of only the monomer reactivity ratios and the interphase partition laws. Its practical implementation needs the on‐line monitoring of conversion. The reliability of the theoretical approach has been tested by comparison with the optimal policies obtained in the literature, for three different binary systems, as the result of various experimental iterative procedures. © 1994 John Wiley & Sons, Inc.
Compatibility and morphology studies of PPO multicomponent blends
Authors: Liang Borun , Pan Lihua
Published: April 2003

The compatibility and phase morphology of poly(phenylene oxide) (PPO) multicomponent blends with poly(ethylene terephthalate) (PET) and polystyrene (PS) were studied using differential‐scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM) methods. The effect of glycidyl methacrylate–styrene copolymer (GMS), as a compatibilizer, on the morphology of the PPO blends has also been studied in detail. The influence of the molecular weight of PET and the synergetic effect of the compatibilizers of GMS and phenoxy (PN) on the morphology were examined. The DSC and DMA results show that two distinct glass transitions corresponding to PET and PPO existed; however, the Tg of PPO shifts toward lower temperature region due to the addition of GMS and PS. The SEM results reveal that PET component exists as dispersed phases in the PPO matrix, while PS is miscible in the PPO matrix. A significant improvement of the compatibility was achieved for the PPO multicomponent blends because of the synergetic effect of GMS and phenoxy. © 1994 John Wiley & Sons, Inc.
Studies on a new water‐soluble sulfur‐containing cellulose derivative
Authors: Zeng Huiyang , Li Wei , Li Zhuomei
Published: April 2003

A new sulfur‐containing cellulose derivative, carboxymethyl cellulose (CMC) xanthate (CMCX), has been prepared by the reaction of CMC with CS2 in 10–15% NaOH solution for 1 h. Degree of esterification (DE) of the product, determined by UV, may reach 3.3% by mole (or about 1.1% by weight). The product was water soluble. The stability of CMCX has been studied by UV, DSC, and TGA, and it was found that CMCX was more stable in the solid state than in solution. The precipitation of gold ion in dilute solution (10 μg Au · mL−1) by CMCX was very rapid, and the recovery efficiency of gold could reach 96% or higher. The optimum dosage was about 0.1 g CMCX for 10 mL 10 μg Au · mL−1 solution. © 1994 John Wiley & Sons, Inc.
Heat‐resistant polyimides and polyamides prepared from 2, 7‐diamino‐9‐dicyanomethylene‐fluorene
Authors: Diakoumakos Constantinos D. , Mikroyannidis John A.
Published: April 2003

9‐Fluorenone was nitrated with fuming nitric acid to yield 2,7‐dinitro‐fluorenone (1). It was condensed with malononitrile in the presence of glacial acetic acid and a catalytic amount of piperidine to afford 2,7‐dinitro‐9‐dicyanomethylene‐fluorene (2). It was catalytically hydrogenated to the corresponding diamine (3). The latter was used as starting material for the preparation of new polyimides and polyamides bearing dicyanomethylene units. In addition, a bismaleimide was synthesized from the reaction of 3 with maleic anhydride and subsequent cyclodehydration of the intermediate bismaleamic acid. The FTIR spectra of polymers were in agreement with those of the synthesized model compounds. The polymers and bismaleimide yielded crosslinked resins upon curing at 300°C for 40 h in the presence of a catalytic amount of 4,4′‐diaminodiphenylmethane. They were stable up to 355–430°C in N2 or air and afforded anaerobic char yield of 52–57% at 800°C. © 1994 John Wiley & Sons, Inc.
Interpenetrating polymer networks. I. Photopolymerization of multiacrylate systems
Authors: Kaczmarek H. , Decker C.
Published: April 2003

The light‐induced polymerization of a triacrylate monomer (TMPTA) has been carried out in a polymer matrix to generate a semi‐interpenetrating polymer network (IPN). The reaction kinetics was followed by IR spectroscopy for the various polymer binders studied: poly(vinyl chloride) (PVC), poly(methyl methacrylate), polystyrene, and crosslinked polyurethane. Under intense illumination, crosslinking occurred extensively within a fraction of a second, with formation of a hard and highly resistant polymer material. These semi‐IPNs were found to be essentially insoluble in the organic solvents, thus indicating that the acrylate network is grafted onto the polymer matrix, probably because of an efficient chain transfer process. The monomer and photoinitiator concentration, as well as the light intensity were shown to have a great influence on both the rate of polymerization and the final degree of conversion. By using an acylphosphine oxide photoinitiator, PVC–;TMPTA blends have been cured within a few minutes in an accelerated QUV‐A weatherometer, which emits low‐intensity UV radiation similar to sunlight. © 1994 John Wiley & Sons, Inc.
Sorption, desorption, diffusion, and permeation of aliphatic alkanes into santoprene thermoplastic rubber
Authors: Aminabhavi Tejraj M. , Phayde Hemant T. S.
Published: April 2003

The molecular transport characteristics of Santoprene rubber in the presence of n‐alkanes, cyclohexane, 2,2,4‐trimethylpentane, and 1,2,3,4‐tetrahydronaphthalene at 25, 40, 55, and 70°C have been studied using a sorption gravimetric technique. From the sorption and desorption studies, the diffusion coefficients have been calculated and used in the discussion of the transport results. It was observed that these data depend on the size of the penetrants. Furthermore, efforts were made to evaluate the permeation coefficients, molar mass between crosslinks, and the kinetic rate constants. These data showed a systematic dependence on the penetrant size. Activation parameters for the process of diffusion and permeation have been calculated from the temperature dependence of the transport coefficients. © 1995 John Wiley & Sons, Inc.
Characterization of copolymeric poly(2‐vinylimidazoline)
Authors: Hurndall Margaret J. , Spies Hendrik S. C. , Sanderson Ronald D.
Published: April 2003

Copolymeric poly(2‐vinylimidazoline), comprising the ring‐closed 2‐imidazoline and ring‐opened linear amide repeat units, was characterized by 13C‐NMR spectroscopy. This was facilitated by the 13C‐NMR analyses of the model compound forms of the copolymer's repeat units, 2‐ethylimidazoline and N‐propionylethylenediamine. Quantitative determinations were made for the percentages of ring‐opened, linear amide, repeat units and residual ethylenediamine present in different batches of the poly(2‐vinylimidazoline) copolymer. © 1995 John Wiley & Sons, Inc.
Influence of spinning velocity on mechanical and structural behavior of PET/nylon 6 fibers
Authors: Aslan S. , Laurienzo P. , Malinconico M. , Martuscelli E. , Pota F. , Bianchi R. , Di Dino G. , Giannotta G.
Published: April 2003

Influence of spinning velocities on the mechanical and structural properties of polyethylene terephthalate (PET)/nylon 6 blend fibers have been reported. Fibers of PET/nylon 6 containing a small percentage of nylon (5% by weight) have been melt‐spun at 3 different spinning velocities (2,900; 3,200; 3,600 m/min). The fibers have been characterized by thermal, morphological, structrual, and mechanical analysis. Various techniques such as SEM, DSC, X‐ray diffraction, hot water shrinkage (HWS), viscosity, and birefringence have been used. SEM analysis revealed that in the blend, nylon 6 is well‐dispersed as spheres in the PET matrix. The blend shows a marked decrease in the melt‐flow index, which in turn leads to a beneficial effect on the rheological properties of the PET without negatively influencing its mechanical characteristics. This finding results in a saving on energetical requirements of the processing, as both temperature and pressure of spinning can be decreased. © 1995 John Wiley & Sons, Inc.
Dependence of dynamic mechanical behavior of DGEBA/DDM stoichiometric epoxy systems on the conditions of curing process
Authors: Sanz G. , Garmendia J. , Andres M. A. , Mondragon I.
Published: April 2003

Dynamic viscoelastic properties of diglycidyl ether of bisphenol A (DGEBA) cured with diaminodiphenylemethane (DDM) have been studied. The relaxation spectra of stoichiometric mixtures have been investigated as a function of the casting procedure and the thermal history during curing. Variations on the temperatures of the loss peaks and also on their magnitude have been observed when a solvent was employed to cast the mixtures. These variations have been attributed to the existence of high crosslinked regions formed at the earlier stage of curing inside the overall matrix. The results obtained from mixtures cured with different thermal histories underline the importance of adequate selection of curing conditions in order to obtain the optimum properties for these materials. Differences in crosslink density amongst the mixtures cured at different conditions have been correlated to the extent of reaction obtained by infrared measurements. © 1995 John Wiley & Sons, Inc.
Hydrolytic aging of polycarbonate. II. Hydrolysis kinetics, effect of static stresses
Authors: Ghorbel I. , Akele N. , Thominette F. , Spiteri P. , Verdu J.
Published: April 2003

Plaques of bisphenol A polycarbonate (PC) were exposed to a water‐saturated atmosphere at temperatures ranging from 40 to 90°C for up to 7 months. Certain samples were exposed under tensile load at 60 and 90°C, 100% RH with stresses ranging from 3.7 to 8.7 MPa. The PC molecular weight was determined by steric exclusion chromatography, and the kinetic parameters for hydrolytic chain scission were determined. It appears clearly that in the presence of tensile stresses, the hydrolysis rate is increased (at both temperatures under study) by a factor of about 10. The stress effect cannot be represented by the Eyring‐Zhurkov relationship because the activation volume appears as an increasing function of the temperature and a decreasing function of time. Some possible causes of the observed stress effects are discussed © 1995 John Wiley & Sons, Inc.
Epoxy resins based on trimethylolpropane. I. Determination of chemical structres
Authors: Pellín M. Pazos , Regueira L. Núñez , Gándara J. Simal , Losada P. Paseiro , Lamela C. Pérez , Abuín S. Paz
Published: April 2003

The chemical structure of an aliphatic epoxy resin was studied by using gel permeation chromatography (GPC), Fourier transform infrared (FTIR), FTIR‐TGA (thermogravimetric analysis), mass spectrometry in fast atom bombardment (FAB) mode, and wet analysis. We found that when trimethylolpropane is used as starting monomer, only two OH groups are epoxidized. The resin and its different fractions have a functionality of two. Under the conditions of synthesis used by the supplier, three main products were found with masses of 246,339, and 430. No trifunctional product was detected. © 1995 John Wiley & Sons, Inc.
Preparation of polypyrrole–polyurethane composite foam by vapor phase oxidative polymerization
Authors: He Feifeng , Omoto Mitsuru , Yamamoto Toshihiro , Kise Hideo
Published: April 2003

Conductive polypyrrole–polyurethane composite foam was prepared by vapor phase polymerization of pyrrole on polyurethane foam using mixtures of FeCl2 and FeCl3 as oxidants. With increase in the FeCl2/FeCl3 ratio, the conductivity of the composite foam increased in spite of the decrease in polypyrrole content in the composite foam. Both conductivity and polypyrrole content increased with increase in the oxidant content in polyurethane. The conductivity of the composite foam is also a function of reaction temperature, and lower reaction temperatures were preferable for higher conductivity. The composite foam exhibited tensile strength and elongation comparable to those of pristine polyurethane foam. © 1995 John Wiley & Sons, Inc.
Mechanochemical polymerization of methyl methacrylate initiated by the grinding of inorganic compounds
Authors: Hasegawa Masahiro , Akiho Yasushi , Kanda Yoshiteru
Published: April 2003

The polymerization of methyl methacrylate mechanochemically initiated by the grinding of several inorganic compounds was attempted using a vibrating ball mill. The inorganic compounds used were quartz, quartz glass, marble, limestone, feldspar, and talc with the particle size range of 149–210 μm. The results demonstrated that all compounds used in these experiments had the activity for mechanochemical polymerization of methyl methacrylate, and that the degree of the activity at the same grinding time remarkably differed with the kind of compound. The existence of the induction period, which is the time until the polymerization started, was also confirmed in all of the compounds. The molecular weight distributions of the polymer formed were unimodal and somewhat broad in the case of any compound, and the number‐average molecular weight was similar to that formed by ordinary radical polymerization. It was suggested that there were two types of the initiation mechanism in the mechanochemical polymerization of methyl methacrylate initiated by the grinding of inorganic compounds. © 1995 John Wiley & Sons, Inc.
Permeability control of poly(methacrylic acid)–poly(ethylenimine) complex capsule membrane responding to external pH
Authors: Yoon Nam Sik , Kono Kenji , Takagishi Toru
Published: April 2003

Previously, permeability of partly crosslinked poly(acrylic acid)–poly(ethylenimine) complex capsule membranes has been shown to be controlled responding to external pH [K. Kono, F. Tabata, and T. Takagishi, J. Membr. Sci., 76, 233 (1993)]. In order to improve pH‐dependent permeation behavior of the polyelectrolyte complex capsule membranes, poly(methacrylic acid), which has hydrophobic side groups, was used as a polyanion component instead of poly(acrylic acid). The polyelectrolyte complex capsules composed of poly(methacrylic acid)–poly(ethylenimine) with a diameter of 5.2 mm were prepared. Permeation of phenylethylene glycol, which was used as a permeant, through the capsule membrane was quite limited at pH between 4 and 8. The permeation of the permeant across the capsule membrane in these pH regions was much less than that of poly(acrylic acid)–poly(ethylenimine) complex capsule membrane. However, the permeability constant was drastically increased in the order of 1 or 2 above pH 8 and below pH 4, depending on temperature. The Arrhenius plot for the permeation of phenylethylene glycol through the capsule membrane showed that the activation energy for the permeation is almost constant in the pH region between 4.5 and 8, but greatly decreases below pH 4 and above pH 8.8, suggesting occurrence of a significant change of the capsule membrane structure near these pH regions due to dissociation of polyelectrolyte complex. When environmental pH of the capsule was changed, release rate of phenylethylene glycol from the capsule was altered quickly and reversibly under acidic condition. © 1995 John Wiley & Sons, Inc.
Studies on applications of natural polyphenol–phenol–formaldehyde copolymer based cation exchange resins
Authors: Mitra N. C. , Banerjee R. S. , Sarkar A.
Published: April 2003

Naturally occurring polyphenol(condensed tannin)‐phenol‐formaldehyde copolymer matrix based cation exchange resins have been successfully used as a solid catalyst (in H+ ion form) in the inversion of sucrose and hydrolysis of methyl acetate. Apart from the normal advantages of the solid catalyst over the acid catalysts in the solution phase, the values of the activation energy, entropy, and enthalpy of activation of the reactions involved reveal that the resins prepared acted as a catalyst with characteristics comparable to those of the commercially available resins based on a styrene–DVB matrix. The resins have also been successfully used for softening of hard water and enrichment of metal ion concentration from very dilute solutions. © 1995 John Wiley & Sons, Inc.
Investigations into the micellization and conductance behavior of cerium soaps in a benzene–DMF Mixture
Authors: Mehrotra K. N. , Chauhan Mithlesh , Shukla R. K.
Published: April 2003

Conductivity measurements were employed to determine the critical micelle concentration (CMC), degree of dissociation and dissociation constant of dilute solutions of cerium soaps in 50% benzene and 50% N‐N‐dimethyl formanide (DMF) mixture (v/v). The results show that the soaps behave as weak electrolytes below the CMC. The various thermodynamic parameters were also evaluated for both dissociation and association process. © 1995 John Wiley & Sons, Inc.
Concentration effect of stearic acid on scorch behavior of epoxidized natural rubber
Authors: Poh B. T. , Tang W. L.
Published: April 2003

The effect of stearic acid on Mooney scorch time of epoxidized natural rubber (ENR 25 and ENR 50) and one grade of unmodified natural rubber (SMR L) was investigated in the concentration range of 0.5 to 14.5 phr. Other parameters, namely accelerator systems, temperature, and fillers (carbon black and silica), on the scorch property of ENR 25 in the presence of excess loading of stearic acid were also studied. Results indicate that scorch time increases with stearic acid loading for all the rubbers investigated, the rate of increase being fastest in ENR 50, followed by ENR 25 and SMR L. Mooney scorch time of ENR shows strong dependence on stearic acid loading for delay‐action accelerators and at lower temperature of vulcanization. For a fixed filler loading, the dependence of scorch time on stearic acid concentration is similar to that of gum stock. The retardation effect exhibited by excess stearic acid on the vulcanization of ENR may be attributed to complex formation of chelates and the reduction in activation of adjacent double bonds in ENR resulting from interaction between stearic acid and the epoxide group of ENR. © 1995 John Wiley & Sons, Inc.
Functionalization and metallization of fluoropolymer surfaces through reduction1,2
Authors: Hung Ming‐H. , Burch Robert R.
Published: April 2003

Fluoropolymer films, such as Teflon™‐TFE [poly(tetrafluoroethylene)], Teflon™‐FEP [copolymer of tetrafluoroethylene and hexafluoropropylene], Teflon™‐PFA [copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether)], and PCTFE [poly(chlorotrifluoroethylene)], are reduced by the mild reducing agent benzoin dianion/DMSO, while Teflon™‐AF [copolymer of tetrafluoroethylene and perfluoro‐2,2‐dimethyl‐1,3‐dioxole] is unreactive. The reduction makes the films adherable toward epoxy resins, the adhesive strength decreasing in the order PCTFE>PFA≥FEP>PTFE. Surprisingly, Teflon™‐AF films are totally inert except when the TFE content is high, and in these cases the adhesive strength of Teflon™‐AF is close to that of PTFE. The surfaces of PTFE, FEP and PFA films are further modified by first treating these films with the benzoin dianion/DMSO reagent and then with an excess of sodium salts of mercaptans. Reactive PTFE films that are light colored with a metallic luster are formed rather than the dark, metallic color typical of PTFE surface reduction without mercaptan treatment. These films have poor adhesion toward epoxy resins but good adhesion toward gold applied by sputtering. FEP and PFA films behaved similarly. These results are attributed to the incorporation of sulfur onto the reduced surface. Unreduced fluoropolymer films reacted with only sodium mercaptan fail to show C—S bond incorporation. This newly developed method can be used to selectively metallize the fluoropolymer film surface with gold layers and affords very high conductivity of the metallized regions. © 1995 John Wiley & Sons, Inc.
The morphology and mechanical properties of phenoxy/liquid crystalline polymer blends and the effect of transesterification
Authors: Choi Gi Dae , Kim Seung Hyun , Jo Won Ho , Rhim Moo San
Published: April 2003

Morphological, rheological, and mechanical properties of poly(hydroxy ether of bisphenol A) (phenoxy) and a Vectra liquid crystalline copolyester (LCP) blends were investigated. Scanning electron micrographs of fracture surfaces of injection‐molded samples show that the LCP forms an elongated fibrous dispersion in the phenoxy matrix. As the mixing time increases, the tensile strength and modulus increase while the elongation at break remains almost constant. These improvements are attributed to the formation of LCP‐grafted phenoxy by the interchange reaction between phenoxy and LCP. The interchange reaction was identified by DSC, a rheometer, and a FTIR spectrometer. The graft copolymer gives better adhesion between the two phases and thus improves mechanical properties of the blends. © 1995 John Wiley & Sons, Inc.
Semibatch emulsion copolymerization of methyl methacrylate and butyl acrylate
Authors: Chern C. S. , Hsu H.
Published: April 2003

The concentration of sodium lauryl sulfate (SLS) in the initial reactor charge is the most important parameter in determining the particle size of a semibatch emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). The number of particles formed is proportional to the concentration of SLS to the 0.5–1.2 power and it is proportional to the concentration of the nonyl phenol–40 mol ethylene oxide adduct to the 0.014–0.72 power. The number of particles is almost independent of the concentration of the initiator. The solubility of monomer in water has an important effect on the nucleation mechanism according to the literature. However, the ratio of MMA to BA does not show any significant effect on the latex particle size in our laboratory. The particle size also increases with increasing ionic strength or agitation speed. Experimental data of particle‐size distribution and molecular weight distribution support the coagulative nucleation mechanism when the concentration of SLS is way below its critical micelle concentration (CMC). © 1995 John Wiley & Sons, Inc.
Hydrogels based on hydrophilic side‐chain siloxanes
Authors: Künzler J. , Ozark R.
Published: April 2003

Methacrylate end‐capped diethylene glycol propyl methyl ether, 5‐hexyl‐1,2‐diol, and 3‐propyloxy‐1,2‐propane diol side‐chain siloxanes were evaluated for potential use as hydrogels for contact lens application. The preparation of the methacrylate end‐capped ether, hexane diol, and propane diol side‐chain siloxanes was accomplished in two relatively simple synthetic steps: The first step consisted of the acid‐catalyzed co‐ring opening polymerization of octamethylcyclotetrasiloxane, tetramethylcyclotetrasiloxane, and 1‐3‐bis‐methacryloyl‐butyltetramethyldisiloxane, followed by a platinum‐catalyzed hydrosilation with (in separate experiments) diethylene glycol allyl methyl ether, trimethylsilyl protected 3‐allyloxy‐1,2‐propane diol, and trimethylsilyl protected 5‐hexene‐1,2‐diol. The trimethylsilyl protecting groups was removed using a 10% 0.1N HCl solution in 2‐propanol. Radical polymerization of the methacrylate end‐capped ether, hexane, and propane diol side‐chain siloxanes with hydrophilic monomers, such as dimethylacrylamide, and a strengthening agent, isobornylmethacrylate, resulted in transparent hydrogels possessing a wide range of water contents, high oxygen permeability, and a low modulus of elasticity and, for the propane diol side‐chain siloxanes, excellent hydrolytic stability. The ether side‐chain siloxane‐based hydrogels exhibited poor hydrolytic stability. © 1995 John Wiley & Sons, Inc.
Performance improvement of MgCl2/dioctylphthalate/TiCl4 catalyst in propene polymerization by employing external base pair
Authors: Yang C. B. , Hsu C. C.
Published: April 2003

The individual roles of three different types of external Lewis bases, namely t‐butylmethyl ether (TBME), 2,2,6,6,‐tetramethyl piperidine (TMPIP), and dimethoxydiphenyl silane (DMDPS), in propene polymerization using MgCl2/dioctylphthalate (DOP)/TlCl4 catalyst were studied. The role of TBME was found to be distinctly different from others. More active sites were believed to be activated in the presence of TBME, whereas the others seemed to play a role of converting atactic sites into isotactic ones. That difference made it possible to improve both catalyst activity and isotacticity by employing TBME together with one of the others as the external base pair. Due to the differences in the coordination strength of these bases with the catalyst, the order of addition of the two bases became important in achieving good results. © 1995 John Wiley & Sons, Inc.
A new copolymerization equation
Authors: Zhou Changren , Lin Shangan
Published: April 2003

A new copolymerization equation is suggested for the calculation of copolymer composition. The new equation is independent of reactivity ratios, so we can obtain the copolymer composition from experimental data when the reactivity ratios are unknown. The new equation has been verified by experimental data (styrene/methyl methacrylate, methyl methacrylate/vinyl chloride, and styrene/acrylonitrile systems). The results of the comparisons suggest that the new equation is satisfactory. © 1995 John Wiley & Sons, Inc.
Water‐based polymers as pressure‐sensitive adhesives—viscoelastic guidelines
Authors: Yang Henry W. H.
Published: April 2003

Water‐based polymers have been widely used as pressure‐sensitive adhesives (PSAs). This article addresses the fundamental viscoelastic parameters that govern PSA performance. The viscoelastic behavior of polymers before and after resin tackification is investigated. Commercial acrylic, CSBR, natural rubber emulsion polymers, and low MW petroleum‐based hydrocarbon resins with various softening points are used to demonstrate the tackification effects. Basic guidelines for selecting the appropriate polymer/resin system to achieve the target performance are given. © 1995 John Wiley & Sons, Inc.
The effect of extruder temperature and maleated polypropylene on polypropylene/nylon‐6,6 blend: A small angle X‐ray scattering study
Authors: Lin J. S. , Sheu Eric Y. , Jois Y. H. R.
Published: April 2003

A series of small‐angle X‐ray scattering measurements were performed to study the polypropylene/nylon‐6,6 polymer blends with or without the compatibilizer: maleated polypropylene. The blends were made at various temperatures using a venting conical twin‐screw extruder with a constant extruding flow rate. The X‐ray scattering results show that the dispersion of nylon‐6,6 in polypropylene is improved for temperature above the melting point of nylon‐6,6 (265°C) when the compatibilizer involved is not used. As the compatibilizer is incorporated, the dispersion is significantly improved, even at the temperature below 265°C. With the compatibilizer, the dispersed nylon‐6,6 particle size and shape in the blends are independent of blending temperature, suggesting that the temperature effect is overwhelmed by the effect of the compatibilizer. © 1995 John Wiley & Sons, Inc.