bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and thermal behavior of nylon‐6/polytetrahydrofuran triblock copolymers obtained via anionic polymerization
Authors: Petrov P. , Mateva R. , Dimitrov R. , Rousseva S. , Velichkova R. , Bourssukova M. 
Published: August 2002

AbstractThe structure, crystallization, and phase behavior of nylon6‐b‐polytetrahydrofuran‐b‐nylon6 triblock copolymers synthesized via activated anionic polymerization have been studied. The composition, molecular weight of polytetrahydrofuran (PTHF) soft block, and type of polymeric activators (PACs) have been varied. Differential Scanning Calorimetry (DSC), Wide‐Angle X‐ray Diffraction (WAXD), Transmission Electron Microscopy (TEM), and Polarized Light Microscopy (PLM) experiments have revealed that in triblock copolymers only the nylon‐6 component crystallizes while PTHF segments are amorphous. The soft blocks do not alter the spherulitic crystalline structure of nylon‐6 and hard blocks crystallize in the α‐modification. The degree of crystallinity decreases with increasing PTHF concentration. The phase behavior has been investigated by Dynamic Mechanical Thermal Analysis (DMTA). Two different glass transition temperatures (Tg) for all samples have been observed. This indicates that nylon‐6 and PTHF segments are not molecularly miscible and the copolymers are microphase separated. The mechanical properties of the copolymers synthesized have been evaluated. Nylon‐6 copolymers with soft block concentrations up to 10 w/w %, exhibit improved notched impact strength in comparison to the nylon‐6 homopolymer, retaining relatively high hardness and tensile strength. All copolymers possess low water absorption and good thermal stability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1448–1456, 2002; DOI 10.1002/app.10448
Formation of hydrophilic starch coatings on polyethylene films
Authors: Fanta George F. , Felker Frederick C. , Shogren Randal L. , Salch John H. 
Published: August 2002

AbstractThin starch coatings were deposited onto polyethylene (PE) film surfaces when PE films were immersed in 1% jet cooked starch solutions and the hot solutions were allowed to cool. Normal cornstarch, waxy cornstarch, high amylose cornstarch, and solvent‐extracted normal cornstarch (to remove native lipid) were used in these experiments. Amounts of adsorbed starch varied from about 0.03–0.05 mg per cm2 of PE, and these starch coatings imparted hydrophilic properties to film surfaces, as evidenced by contact angle measurements. Although starch could be removed by gently rubbing water‐wet PE surfaces, air‐dried coatings were more firmly attached, and did not separate from the PE surface when films were bent or flexed. SEM images of starch‐coated film surfaces showed that starch was deposited as particles less than 1 μm in diameter, and also as aggregates of these submicron particles. Despite the fact that some starch samples contained only very small amounts of amylose and native lipid, surface‐deposited starch in all experiments contained 90–100% amylose; and exhibited the same Vh X‐ray diffraction pattern, indicative of helical inclusion complex formation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1781–1788, 2002; DOI 10.1002/app.10589
Studies on plasma polymerization of hexamethyldisiloxane in the presence of different carrier gases
Authors: Fang Jianglin , Chen Hong , Yu Xuehai 
Published: August 2002

AbstractPlasma polymerization of hexamethyldisiloxane(HMDSO) in the presence of different carrier gases such as H2, He, N2, Ar, and O2 was carried out using an inductively coupled electrodeless glow discharge. The polymerization kinetics showed that the monomer HMDSO plasma‐polymerized at different rates from low to high for the carrier gases H2, He, N2, Ar, and O2 in that order. The products were studied using FTIR, electron spectroscopy for chemical analysis, and elemental analysis. The results indicated that HMDSO molecules underwent different degrees of fragmentation in plasma polymerization for different carrier gases and radio frequency (RF) powers. The polymer deposition rate and the structures of products were mainly dependent on molecular fragmentation, which varied with carrier gas and imposed RF power. O2 and H2 gases can incorporate in the plasma polymers to form products containing more oxygen or hydrogen components, while other gases such as N2 have no detectable component in products. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1434–1438, 2001
Atomic force microscopy study on structure and properties of irradiation grafted silica particles in polypropylene‐based nanocomposites
Authors: Zhang Ming Qiu , Rong Min Zhi , Zeng Han Min , Schmitt Stefan , Wetzel Bernd , Friedrich Klaus 
Published: August 2002

AbstractNanosilica particles treated by irradiation grafting polymerization can effectively improve the strength and toughness of a thermoplastic polymer at a rather low filler content. A detailed investigation on the modified nanoparticles in the absence and presence of a polypropylene matrix is carried out by using atomic force microscopy. The results indicate that the loosen agglomerates of the untreated SiO2 became more compact due to the linkage between the nanoparticles offered by the grafting polymer. In addition, the molecules of the polypropylene matrix are able to diffuse into the modified nanoparticle agglomerates during the melt processing. Entanglement between the molecules of the grafting polymer and the matrix is thus available, which in turn facilitates a strong particle–matrix interfacial interaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2218–2227, 2001
Preparation and characterization of siliconized epoxy/bismaleimide (N,N′‐bismaleimido‐4,4′‐diphenyl methane) intercrosslinked matrices for engineering applications
Authors: Ashok Kumar A. , Alagar M. , Rao R. M. V. G. K. 
Published: August 2002

AbstractNovel hybrid intercrosslinked networks of hydroxyl‐terminated polydimethylsiloxane‐modified epoxy and bismaleimide matrix systems have been developed. Epoxy systems modified with 5, 10, and 15 wt % of hydroxyl‐terminated polydimethylsiloxane (HTPDMS) were developed by using epoxy resin and hydroxyl‐terminated polydimethylsiloxane with γ‐aminopropyltriethoxysilane (γ‐APS) as compatibilizer and dibutyltindilaurate as catalyst. The reaction between hydroxyl‐terminated polydimethylsiloxane and epoxy resin was confirmed by IR spectral studies. The siliconized epoxy systems were further modified with 5, 10, and 15 wt % of bismaleimide (BMI). The matrices, in the form of castings, were characterized for their mechanical properties. Differential scanning calorimetry and thermogravimetric analysis of the matrix samples were also performed to determine the glass‐transition temperature and thermal‐degradation temperature of the systems. Data obtained from mechanical studies and thermal characterization indicate that the introduction of siloxane into epoxy improves the toughness and thermal stability of epoxy resin with reduction in strength and modulus values. Similarly the incorporation of bismaleimde into epoxy resin improved both tensile strength and thermal behavior of epoxy resin. However, the introduction of siloxane and bismaleimide into epoxy enhances both the mechanical and thermal properties according to their percentage content. Among the siliconized epoxy/bismaleimide intercrosslinked matrices, the epoxy matrix having 5% siloxane and 15% bismaleimide exhibited better mechanical and thermal properties than did matrices having other combinations. The resulting siliconized (5%) epoxy bismaleimide (15%) matrix can be used in the place of unmodified epoxy for the fabrication of aerospace and engineering composite components for better performance. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 38–46, 2001
Curing kinetics and thermal properties of diglycidylether of bisphenol A with various diamines
Authors: Hwang Seok‐Ho , Jung Jae‐Chang 
Published: August 2002

AbstractTo prepare a high‐performance epoxy, we synthesized three types of diamines {N,N′‐(4,4′‐diphenylether)‐bis(4‐aminophthalimide), 4,4′‐bis(p‐aminophenoxy)dibenzalphentaerythriol, and 2,2′‐bis[4‐(p‐aminobenzoyl)phenyl]propane} as epoxy curing agents with a two‐step reaction sequence. The structures of the synthesized diamines were confirmed with Fourier transform infrared and nuclear magnetic resonance spectroscopy. The curing kinetics and thermal stability of the cured epoxy resin with diglycidylether of bisphenol A were estimated with differential scanning calorimetry and thermogravimetric analysis under a nitrogen atmosphere. The kinetics parameters were determined with the Ozawa and Kissinger equations. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 279–284, 2001
Time–temperature–transformation diagram for reactive processing of polyamide 12
Authors: Luisier A. , Bourban P.‐E. , Månson J.‐A. E. 
Published: August 2002

AbstractIn order to describe the different events occurring during the anionic polymerization of polyamide 12 (PA12), a general concept of a time, temperature, and transformation (TTT) diagram was established and related to reactive processing conditions. Polymerization kinetics were established, and it was found that the reaction was best described by an autocatalytic expression. Polymerization temperatures above and below the final polymer melting temperature were considered. Furthermore, the variation of the melting temperature and viscosity were followed as a function of the polymerization time and degree of conversion. It was shown that monomer–polymer phase separation and crystallization may occur during PA12 polymerization. The results could be adapted for use during liquid molding of PA12 polymers and their composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 963–972, 2001
Thermooxidative stability of different polyurethanes evaluated by isothermal and dynamic methods
Authors: Fambri L. , Pegoretti A. , Gavazza C. , Penati A. 
Published: August 2002

AbstractTwo methods for the evaluation of resistance to the thermooxidation of different classes of polyurethane films (PURs) throughout thermogravimetric analyses were used. Normal and waterborne polyurethanes were characterized using either isothermal or dynamic heating. In the isothermal method, the times required to reach degradations of 0.025, 0.05, and 0.10 were determined at several temperatures in the interval of 190–250 °C. In the dynamic method, heating rates of 0.5, 1, 2, 5, and 10 °C/min were used in the range of 30–500 °C, and degradations of 0.025, 0.05, 0.10, 0.20, and 0.40 were considered. From the Arrhenius plots, activation energies were evaluated ranging between 130 and 230 kJ/mol for normal PURs and between 80 and 170 kJ/mol for waterborne PURs depending on the method, temperature interval, and degree of degradation. Advantages and disadvantages of the two methods were compared. The isothermal method requires a preliminary test, and it was more useful for degradation studies up to 0.05. The dynamic method offered evidence for the presence of different degradation processes, and it was more suitable for the evaluation of kinetics parameters at higher degrees of degradation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1216–1225, 2001
Gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene, polyethylene/polyamide, and polyethylene/modified polyamide bottles
Authors: Yeh Jen‐Taut , Chen Chin‐Her , Shyu Wei‐De 
Published: August 2002

AbstractAn investigation of the gasoline permeation resistance of the as‐blow‐molded and annealed polyethylene, polyethylene (PE)/polyamide (PA), and polyethylene/modified polyamide (MPA) bottles is reported. The gasoline permeation resistance improves dramatically after blending PA and MPA barrier resins in PE matrices during blow‐molding, and the order of barrier improvement corresponds to the order of barrier improvement of the barrier resins added in PE. Somewhat unexpectedly, the gasoline permeation rates of the annealed PE and/or PE/PA bottles annealed at 90°C or higher temperatures increase significantly with the annealing temperature and time. On the contrary, the gasoline permeation resistance of the annealed PE/MPA bottles increase significantly as the annealing temperature and/or time increase. For instance, the gasoline permeation rate of the PE/MPA bottle annealed at 120°C for 32 h is about 190 times slower than that of the as‐blow‐molded PE bottle. Further investigations found that, after blending the MPA and PA barrier resins in PE matrices, the relatively nonpolar hydrocarbon components present in the gasoline fuels were significantly blocked, without permeation during the permeation tests, in which the as‐blow‐molded PE/MPA bottle inhibited the permeation of hydrocarbon components more successfully than did the as‐blow‐molded PE/PA bottle. In contrast, the amounts of polar components that permeated through the as‐blow‐molded PE/PA and PE/MPA bottles were very small and about the same as the amount that permeated through the as‐blow‐molded PE bottle. Possible mechanisms accounting for these interesting behaviors are proposed in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2827–2837, 2001
Mercapto‐modified copolymers in polymer blends. III. The effect of functionalized ethylene‐propylene‐diene rubber (EPDM) on curing and mechanical properties of NBR/EPDM blends
Authors: Oliveira Marcia G. , Soares Bluma G. 
Published: August 2002

AbstractEthylene‐propylene‐diene with ethylene norbornene as the diene (EPDM) samples functionalized with thioacetate (EPDMTA) or mercapto groups (EPDMSH) were employed as compatibilizing agents for nitrile rubber (NBR)/EPDM blends. The cure rate of the blend was affected by the presence of a small portion of these compounds. EPDMTA decreases the cure rate of the blends, whereas EPDMSH was able to decrease the scorch time and increase the cure rate when employed in a proportion as high as 5.0 phr. The compatibilization effect was influenced by the nature of the EPDM employed in the blends. Blends consisting of an EPDM sample with lower viscosity display better dispersion of the EPDM phase inside the NBR matrix and also better mechanical performance with the compatibilization. The compatibilization with EPDMSH is reactive, with the formation of chemical bond between the mercapto groups of the compatibilizing agent and the double bond of the diene rubber. The compatibilization with EPDMTA is also considered to be reactive because the vulcanized blends containing this functionalized copolymer contain a higher amount of cross linked material, as indicated by the lower weight loss after swelling experiments. A scanning electron micrograph demonstrated that these functionalized copolymers led to a finer phase morphology, mainly in NBR/EPDM57C blends. The compatibilization increases the dynamic elastic modulus without affecting the damping. An improvement of thermal aging resistance of the studied blends was also achieved with the presence of the functionalized copolymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 38–52, 2001
Sequence analysis of poly(ethylene terephthalate)/poly(butylene terephthalate) copolymer prepared by ester‐interchange reactions
Authors: Kim Joon Ho , Lyoo Won Seok , Ha Wan Shik 
Published: August 2002

AbstractThe molecular structure of the copolyester formed through the interchange reaction in poly(ethylene terephthalate)/poly(butylene terephthalate) blends was investigated with 13C‐NMR spectroscopy. The molar fractions of heterolinkage triads in the copolyesters were lower than the values calculated by Bernoullian statistics; this indicates that the sequence of heterolinkages was far from a random distribution at the initial stage of the interchange reaction. However, the randomness increased and the number‐average sequence length decreased with reaction time. The solubility of the blend decreased with increasing sequence length, resulting from the formation of block copolymers with long sequence lengths at the initial stage of the interchange reaction. The solubility of the copolyester formed by a dibutyltin dilaurate (DBTDL)‐catalyzed reaction was higher than that of the copolyester formed by a titanium tetrabutoxide‐catalyzed reaction; this is related to the fact that alcoholysis prevailed in the DBTDL‐catalyzed reaction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 159–168, 2001
Electrical and thermal properties of composite of liquid crystalline polymer filled with carbon black
Authors: Wong Y. W. , Lo K. L. , Shin F. G. 
Published: August 2002

AbstractThe electrical resistivity and thermal conductivity of a liquid crystalline polymer (LCP) filled with a commercial carbon black (CB) of various volume fractions (ϕ) is investigated. The percolation threshold (ϕc) is found at about 3%, and the resistivity (ρ) as a function of (ϕ − ϕc) satisfies the exponential function. Although the pure LCP is highly anisotropic in thermal and mechanical properties after processing, the composite samples exhibit no preferential direction for electrical conduction. Samples of ϕ below ϕc exhibit a negative temperature coefficient of resistivity while those above ϕc show almost no temperature dependence from room temperature to 200°C. In addition, the samples at lower ϕ have higher thermal conductivity in the LCP flow direction than those measured in the transverse and thickness directions, and they approach the same value at higher ϕ. This result indicates that preferential molecular alignment of the matrix LCP is responsible for the behavior of the thermal conductivity of the composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1549–1555, 2001
Effect of emulsion polymerization conditions of vinyl acetate on the viscosity fluctuation and gelation behavior of aqueous poly(vinyl alcohol) solution
Authors: Lyoo Won Seok , Lee Sung Min , Koo Kang , Lee Joon‐Seok , Ghim Han Do , Kim Jae Pil , Lee Jinwon 
Published: August 2002

AbstractPoly(vinyl alcohol) (PVA) was prepared by emulsion polymerization of vinyl acetate (VAc) at 40, 50, and 60°C. PVAs of various molecular parameters were dissolved in water at concentrations of 3, 5, and 7% (g/dL) and aged at 30 and 60°C. The effects of the molecular weight and polymerization temperature on the viscosity fluctuation and gelation behavior of aqueous PVA solutions were investigated. Viscosity was increased with increasing molecular weight when other parameters were held the same. PVA of superior molecular regularity due to the lower polymerization temperature of VAc had higher relative viscosity. Viscosity and its fluctuation of PVAs with aging time varied with the polymerization temperature of the precursors, concentration of the aqueous solutions, and aging time. For PVA with a number‐average degree of polymerization of 2800 prepared from poly(vinyl acetate) polymerized at 40°C, a sharp increase in viscosity was observed after 500 min of aging at a concentration of 7%. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1897–1902, 2001
Block copolymer molecular weight determination via gel permeation chromatography: Choosing a combining rule
Authors: Sebastian John M. , Register Richard A. 
Published: August 2002

AbstractWe present a method for accurately determining the true molecular weights of narrow‐distribution block copolymers, using only a basic gel permeation chromatograph (GPC) equipped with a refractive index detector and calibrated with polystyrene standards. Our approach is based on the well‐known observation that GPC calibration curves for different homopolymers in good solvents are essentially parallel, allowing the curves for different polymers to be described by simple hydrodynamic equivalence ratios rB versus polystyrene. We present values of rB, in both toluene and tetrahydrofuran, for various polydiene and hydrogenated polydiene homopolymers commonly incorporated into commercial styrenic block copolymers. These values of rB must be combined to yield the hydrodynamic equivalence ratio of the block copolymer, from which the block copolymer's true molecular weight can be determined. Three combining rules proposed in the literature are tested against a series of symmetric polystyrene–polybutadiene diblock copolymers of varying molecular weight. A simple linear combining rule accurately represents the results. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2056–2069, 2001
Diet of blue cod, Parapercis colias, living on undisturbed biogenic reefs and on seabed modified by oyster dredging in Foveaux Strait, New Zealand
Authors: Jiang Weimin , Carbines Glen 
Published: August 2002

Abstract
Little has been done to assess the potential impact of habitat modification by bottom fishing gear on the feeding habits of demersal fishes. An analysis is presented of the diet of blue cod in Foveaux Strait, southern New Zealand, based on the gut content of fish taken in winter 1999 from two sites where each site consisted of both undisturbed biogenic reefs and reefs modified by oyster dredging.
Of the 420 guts collected, 13% were empty. The overall mean wet weight of gut content was <4 g. No significant habitat or site effects were detected for the proportion of empty guts or the amount of food consumed.
A pattern was detected that blue cod on dredged habitats generally fed on more crustaceans than those on undistributed habitats. Blue cod from undisturbed habitat also displayed a more diverse diet than those taken from dredged habitat. These results suggest that long‐term disturbance of seabed habitat by the oyster fishery in Foveaux Strait has caused changes to the diet of blue cod. The findings also suggest that actions should be taken to protect the biogenic reefs from further damage if the blue cod fishery and related resources are to be effectively managed.
Changes in prey diversity with increasing fish size were also found, with prey diversity (Shannon–Wiener index) increasing from 0.83 to 1.35 over a range of fish size from <25 cm to larger than 34 cm. A total of 52 prey taxa were identified in the diet of blue cod. Crustaceans were the main component, followed by mollusca and polychaeta. Fish, echinodermata and ‘other’ were less important in the diet.
Copyright © 2002 John Wiley & Sons, Ltd.
Mechanics of venom expulsion in Crotalus, with special reference to the role of the fang sheath
Authors: Young Bruce A. , Blair Michael , Zahn Krista , Marvin Jessica 
Published: August 2002

AbstractA combination of anatomical and experimental preparations were used to explore the function of the venom delivery system in rattlesnakes (Crotalus). The distal end of the venom duct is compressed near the point where it empties into the venom chamber, a space surrounding the fang defined by the fang sheath. Within the venom chamber, the inner fang membrane lies obliquely over the base of the fang at least partially occluding the entrance orifice. When the fang is retracted the combination of the compressed venom duct and the spatial position of the inner fang membrane serve to inhibit or block venom flow. As the fang is erected beyond approximately 60° (relative to the roof of the mouth) localized compression of the fang sheath decreases the size of the venom chamber, relieves the compressive force from the venom duct, and displaces the inner fang membrane away from the entrance orifice of the fang. Pressure recordings taken at different locations along the venom delivery system demonstrate that the venom gland produces suction during relaxation of the extrinsic glandular musculature. These findings suggest that the venom delivery system of Crotalus is both more flexible and more regulated than previously assumed. Anat Rec 264:415–426, 2001. © 2001 Wiley‐Liss, Inc.