bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fine‐tuning the mechanical properties of hydroxyl‐terminated polybutadiene/ammonium perchlorate‐based composite solid propellants by varying the NCO/OH and triol/diol ratios
Authors: Hocaoğlu Özgür , Özbelge Tülay , Pekel Fikret , Özkar Saim 
Published: August 2002

AbstractChanges in the mechanical properties of hydroxyl‐terminated polybutadiene/ammonium perchlorate‐based composite solid propellants were studied during the curing period with respect to variations in the crosslink density, which was predominantly determined by the equivalent ratio of diisocyanate to total hydroxyl (NCO/OH ratio) and the equivalent ratio of triol to diol (triol/diol ratio). For this purpose, 16 propellants were prepared in different compositions through changes in the NCO/OH ratios (0.81, 0.82, 0.83, and 0.85) for each triol/diol ratio (0.07, 0.09, 0.11, and 0.13) and were tested for their mechanical properties immediately after curing. The propellants with an NCO/OH ratio of 0.82 had minimum stress, modulus, and hardness with maximum strain capability, whereas the propellants with an NCO/OH ratio of 0.85 showed just the opposite behavior. Variations in the isocyanate level seemed to have more effect on the mechanical properties at higher triol/diol ratios. It was also concluded that the propellants with triol/diol–NCO/OH combinations of 0.11–0.83, 0.11–0.85, 0.13–0.81, 0.13–0.83, and 0.13–0.85 were not acceptable for upper stage case‐bonded rocket applications because of either high tensile strength or high modulus. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2072–2079, 2002; DOI 10.1002/app.10605
Synthesis and characterization of oligosalicylaldehyde‐graft‐oligoaniline and its beginning oligomers
Authors: Kaya İsmet , Vilayetoǧlu Adalet R. 
Published: August 2002

AbstractConjuge bonding oligosalicylaldehyde‐graft‐oligoaniline (OSA‐graft‐OA) was synthesized from the polycondensation reaction of oligosalicylaldehyde (OSA) with oligoaniline (OA). There were various functional groups such as OH, NH and CHN in the structure of the graft cooligomer. The physical properties of graft‐co‐oligomers such as melting temperature and solubility were studied: number‐average molecular weight, mass‐average molecular weight, and a polydispersity index of OA, OSA, and fractions of the graft cooligomers [(OSA‐graft‐OA)‐I] and [(OSA‐graft‐OA)‐II] were found to be 740, 780 g mol−1,1.05; 3700, 5990 g mol−1, 1.62; 990, 2770 g mol−1, 2.80 and 1300, 4100 g mol−1, 3.15, respectively. The FTIR and UV‐Vis spectra of the graft cooligomer were compared with those of beginning oligomers. The spectral analyses results showed that the OSA‐graft‐OA synthesized from the polycondensation reaction of aromatic amine with aldehyde that have long oligophenol macromolecule bonded each other with an azomethine bridge through oligophenylamine side chains. The thermal stability of the graft cooligomer and oligomers were measured by thermogravimetric analysis (TG) under an air atmosphere. According to TG analyses, the carboneous residues of the [(OSA‐graft‐OA)‐I) (soluble in ethanol) and (OSA‐graft‐OA)‐II) (soluble in toluene)] were 23 and 40%, respectively, at 1000°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 218–226, 2002
Synthesis, characterization, and properties of amphiphilic poly(ethyl acrylate) with uniform polyoxyethylene grafts
Authors: Xie Hong‐Quan , Liu Yan 
Published: August 2002

AbstractAmphiphilic copolymers of ethyl acrylate (EA) with uniform polyoxyethylene (PEO) grafts were synthesized by copolymerization of EA with methacrylate terminated PEO macromer in benzene using azobisisobutyronitrile as the initiator. The effects of the molecular weight of the macromers, the charging weight ratio of the macromer to EA, the total monomer concentration, and the amount of initiator on the grafting efficiency (GE) were reported as was the molecular weight of the copolymers. The highest GE reached to above 90% and the molecular weight of the copolymers varied from (5–15) × 104. The reactivity ratio of EA with the macromer was determined to be 0.83. The graft copolymers were purified with extractions and the purified products were characterized with IR, 1H‐NMR, gel permeation chromatography, differential scanning calorimetry, and membrane osmometry. The average grafting number of the copolymer varied from 2 to 11. The glass‐transition temperature of the poly(EA) in the copolymer was increased because of the partial compatibility of the two components. The crystalline property, emulsifying property, and dilute solution viscosity of the graft copolymers, as well as ionic conductivity of their complexes with alkali metal salts, were studied. The emulsifying volume decreased with the increasing molecular weight of the PEO grafts. The addition of NaOH to the emulsion affected the emulsifying volume only slightly, whereas the addition of HCl changed the oil in water type emulsion into a water in oil type. The conductivity of the LiClO4 complex of the copolymer with an oxyethylene/Li ratio of 20 reached 3.7 × 10−5 S/cm at 27°C. The lower the crystallinity of the complex, the higher was the conductivity. The dilute solution viscosity showed the existence of intramolecular microphase separation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 903–912, 2001
Effects of nitrolignin on mechanical properties of polyurethane–nitrolignin films
Authors: Zhang Lina , Huang Jin 
Published: August 2002

AbstractPolyurethane‐nitrolignin (PUNL), a new network polymer, was synthesized from a castor oil based–polyurethane (PU) prepolymer and nitrolignin (NL) with a weight‐average molecular weight of 20.6 × 104 and a content of 1.4–10%. The structure and miscibility of PUNL films prepared by solution casting were investigated by infrared spectroscopy and transmission electron microscopy. The results indicated that PUNL2 film, which had a 2.8% NL content, was the most miscible, and its tensile strength (σb) and breaking elongation (ϵb) were 2 times higher than that of PU film. The crosslink densities of PUNL films increased with the increase of NL content until about 3%, similar to the variety of the mechanical properties. Thermogravimetric analysis revealed that the thermal stability of PUNL films was slightly higher than that of PU. Covalent bonds occurred between PU prepolymer and the NL in the PUNL films, forming crosslink networks, which resulted in the enhancement of mechanical properties and thermal stability. NL has a far higher reactivity with PU than nitrocellulose. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1213–1219, 2001
Ionomer. I. The effect of woven glass mat reinforcement on tensile properties
Authors: Shonaike Gabriel O. , Sugahara T. , Murakami A. 
Published: August 2002

AbstractAn investigation was conducted on ionomer polymer. The ionomer pellets were molded into a thin sheet before fabrication into composites. The reinforcing agent used was woven glass mat. Before fabrication, the woven glass mat was treated with the following: 1. silane coupling agent for 5 min and dried at room temperature; 2. silane coupling agent for 5 min and dried in the oven at 110°C for 15 min; 3. Ultraviolet radiation for 5 min; and 4. silane (oven dried + ultraviolet). The composites were fabricated at various pressure, time, and temperature. An ideal processing condition was established, i.e., pressure = 5 MPa, temperature = 180°C, and the impregnation time = 30 min. The void contents of the composites were estimated using the ignition method and the tensile properties were measured. The results revealed that good impregnation of the matrix ionomer into the reinforcing agent can be achieved at 180°C. This was confirmed by low void content as compared with other test temperatures. Further clarification was through the tensile properties, which were higher than those at lower temperatures (120 and 150°C). The effect of fiber orientation was checked, and both 0 and 90° had identical strengths and moduli irrespective of the various fiber treatments. Apart from the void contents, the degree of impregnation was also checked based on the tensile strengths in 45, 25, and 60° fiber orientations. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1395–1400, 2001
Preparation of aminopropyl polysiloxane‐based heat‐curable silicone rubber
Authors: Wu Yongzhong , Feng Shengyu , Bei Yiling , Liu Peng 
Published: August 2002

AbstractBy using polysiloxane containing aminopropyl groups as a base gum and polysiloxane containing epoxy groups as a crosslinker, we prepared a new type of addition‐curable silicone rubber and investigated in detail the effect of various factors on the silicone rubber. Better technical conditions were determined and the vulcanizates with fine mechanical properties were obtained. The tensile strength, tear strength, elongation at break, and hardness of the vulcanizates reach 8.1 MPa, 19.4 kN/m, 420%, and 64 ShA, respectively. To analyze the crosslinking statue, we measured their crosslinking density by toluene‐swelling methods. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2341–2346, 2001
Preparation and physical properties of konjac glucomannan–polyacrylamide blend films
Authors: Xiao Chaobo , Lu Yongshang , Zhang Lina 
Published: August 2002

AbstractThe blend films of konjac glucomannan (KGM) and polyacrylamide (PAAm) were prepared by using the solvent‐casting technique. Transparent blend films were obtained in all blending ratios. The physical properties of the films were investigated by Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and by measurement of mechanical properties. The results indicated the occurrence of intra‐ and intermolecular interactions of the pure components, as well as the intermolecular interactions between KGM and PAAm through hydrogen bond formation. The thermal stability and mechanical properties of both tensile strength and elongation at break of the films were improved by blending KGM with PAAm. It was worth noting that the blend film had the greatest tensile strength when the KGM content in the blend films was around 30 wt %. Surface morphology of the films observed by SEM was consistent with the above‐noted results. Furthermore, the water absorbability of the blend films was also investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 882–888, 2001
Modification of aqueous polyurethanes via latex AB crosslinked polymers
Authors: Lee Jeong Sam , Kim Byung Kyu 
Published: August 2002

AbstractA series of Latex AB crosslinked polymers have been synthesized from polyurethane (PU) (polymer A) and polystyrene (PS) (polymer B). The effect of PU/PS composition, crosslinking density in the PS domain, as well as in PU has been studied in terms of dispersion size, TEM morphology, mechanical, dynamic mechanical properties, in addition to swellability in water and toluene of the dispersion cast film. An inverted core (PS)‐shell (PU) morphology with very fine (tens of nanometers) dispersion was obtained, and the film properties were well controlled by the Latex composition and crosslinking density of both phases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1315–1322, 2001
Novel organic/inorganic nanocomposite of polyethylene. I. Preparation via in situ polymerization approach
Authors: Rong Junfeng , Li Hangquan , Jing Zhenhua , Hong Xiaoyu , Sheng Miao 
Published: August 2002

AbstractA novel methodology for the preparation of polyethylene/palygorskite, “in situ coordinated polymerization,” was proposed. A Ziegler–Natta catalyst was first supported on the surface of nanoscale crystal fibers of palygorskite and subsequently used to initiate ethylene polymerization on the surface of the fibers. The palygorskite was encapsulated by polyethylene and became reinforcement fibers of the composite. The palygorskite fibers were heat‐treated to remove water, to ensure that the supported titanium species possessed proper activity for the polymerization of ethylene. The effect of the conditions of heat‐treating, titanium‐supporting, and other factors such as temperature and type and amount of the cocatalyst on the initiation activity of the palygorskite fibers were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1829–1837, 2001
Investigation of the melting behavior and morphology development of polymer blends in the melting zone of twin‐screw extruders
Authors: Potente H. , Krawinkel S. , Bastian M. , Stephan M. , Pötschke P. 
Published: August 2002

AbstractThe melting behavior and the morphology development that runs parallel to it play central roles in the processing of polymer blends. We studied the impact of speed, melt throughput, continuous‐phase viscosity, screw configuration, and disperse‐phase content on the melting behavior and morphology development in the melting zone of a twin‐screw extruder. The polymer blend used incorporated polyamide‐6 (PA6) as its disperse phase and a high‐viscosity or low‐viscosity polypropylene as the matrix phase. The melting behavior of the polymer blend was investigated with press plates. A qualitative assessment was made of the processes, on basis of the optical impression gained from the transilluminated press plates. One key result was that the PA6 granules melted very rapidly in the polypropylene melt. We took samples over the length of the melting section to permit a quantitative assessment of the morphology. The results show a finely dispersed morphology already at the start of the melting section. This did not undergo any essential change as the blend passed through the extruder, and only a limited correlation was evident with the process parameters. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1986–2002, 2001
Phosphate‐containing flame‐retardant polymers with good compatibility to polypropylene. II. Effect of the flame‐retardant polymers on polypropylene
Authors: Chiang Wen‐Yen , Hu Howard C.‐H. 
Published: August 2002

AbstractTwo kinds of flame‐retardant polymers prepared from the phosphorylation of poly(vinyl acetate) were employed to reduce the flammability of polypropylene (PP). The two flame‐retardant polymers had very different effects because of the differences in their chemical structure. Effects on flame retardancy, thermal properties, mechanical properties, and phase morphology were investigated. Under a certain molecular design, the flame‐retardant polymers were able to offer good flame retardancy, good mechanical properties, and good PP matrix compatibility. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2399–2403, 2001
The tensile and compressive deformation of polymer and carbon fibers
Authors: Northolt M. G. , Baltussen J. J. M. 
Published: August 2002

AbstractAn outline of the continuous chain model for the description of the tensile and compressive deformation of polymer fibers below the glass transition temperature is presented. The basic mechanism is the contraction of the chain orientation distribution as a result of elastic, plastic, and viscoelastic shear deformation. The deformation of the fiber is calculated for finite strains and arbitrary values of the orientation parameter. The model explains the yield and the compressive strength of polymer fibers. The tensile curve, including yielding, is described in terms of the modulus for shear between the chains, the chain modulus, the chain orientation distribution, and a yield parameter. The response to complex time‐dependent loading schemes can be calculated by introduction of the Eyring reduced time model. The elastic tensile deformation of carbon fibers is described in terms of the classical series aggregate model. It is shown that the modulus for shear between the graphitic planes and the orientation distribution of these planes govern the tensile and compressive properties of carbon fibers. The high values of the shear modulus are attributed to some covalent bonding between the graphitic planes. A survey of the various models for the strength of polymer fibers is presented and a new model is discussed, which explains the failure envelope of polymer fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 508–538, 2002
Dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate: Synthesis and characterization
Authors: Cho M. S. , Yoon K. J. , Song B. K. 
Published: August 2002

AbstractDispersion polymerization of acrylamide (PAM) has been successfully carried out in aqueous ammonium sulfate media by using poly(acryloyloxyethyl trimethylammonium chloride) (PAOTAC) as the polymeric stabilizer and 2,2′‐azobis(2‐methyl propionamidine) dihydrochloride (AIBA) as the initiator. The polymerization behaviors with varying concentrations of acrylamide, PAOTAC, AIBA, and ammonium sulfate were investigated. The reaction conditions for stable dispersion were concentrations of 5–10% for acrylamide, 0.6–1.8% for the stabilizer, 0.92–1.84 × 10−4 mol/L for the initiator, and 24–30% for the salt. The resulting conversion–time curves were S‐shaped, as is typically observed in polymerization. Polydisperse spherical particles were formed in the system. An image analyzer photographed the size of the dispersed particles and their distribution was measured. The mechanism and kinetics for the dispersion polymerization were discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1397–1405, 2002
Retinoic acid administration is associated with changes in the extracellular matrix and cardiac mesenchyme within the endocardial cushion
Authors: Yan Min , Sinning Allan R. 
Published: August 2002

AbstractRetinoic acid has been associated with a number of cardiac defects, some of which seem to be related to changes in the endocardial cushions. Studies in mice and older chick embryos have suggested that these defects may be associated with a decrease in mesenchymal cell formation within the cushion. In a previous report we showed that retinoic acid lowered the number of mesenchymal cells in a culture bioassay of mesenchyme formation and that this response was due to retinoic acid modifying the production of particulate matrix from the myocardium. In this study, we have extended these observations to the embryo by implanting a retinoic acid coated bead into the embryo and examined the effect on cardiac mesenchyme formation and in the production of the particulate matrix. In all cases the addition of retinoic acid resulted in a decrease in the number of mesenchymal cells invading the endocardial cushions. In addition retinoic acid increased the production of hLAMP‐1 and fibronectin but not transferrin, confirming our earlier report. Finally, we measured the volume of the cushion and calculated the cell density of both the inferior and superior cushions. The results suggest that the superior cushion is more sensitive to retinoic acid treatment than the inferior cushion. Collectively, these results support our earlier work that suggests that the mechanism of retinoic acid cardiac abnormalities involves a disruption in the production of particulate matrix from the myocardium and a subsequent decrease in cardiac mesenchyme cells that results in a malformed cardiac cushions. Anat Rec 263:53–61, 2001. © 2001 Wiley‐Liss, Inc.
Communicating science: From the laboratory bench to the breakfast table
Authors: Hendrix Mary J.C. , Campbell Paulette W. 
Published: August 2002

AbstractIf we are to maintain public appreciation and support for our scientific enterprise, we need to pay more attention to translating the benefits and grandeur of science into the language of broader society. Both educators and journalists have a role to play in communicating the achievements of science, but scientists must recognize that we have a responsibility to increase the availability and salience of science to the public.
Changes of protein tyrosine phosphorylation in third instar larval integument of the Mediterranean fruit fly, Ceratitis capitata
Authors: Zervas Christos G. , Katsoris Panagiotis G. , Marmaras Vassilis J. 
Published: August 2002

AbstractDevelopmental analysis of the tyrosine protein phosphorylation levels in larval integument and partial characterization of the endogenous protein tyrosine kinase activity (PTK) in Ceratitis capitata are described in this study. Larval integument contains high levels of PTK activity at the early stages of the third instar, which progressively declines to low levels in the white pupal stage. An integumental 90‐kDa polypeptide was identified to have prominent endogenous PTK activity and follow a similar developmental pattern. The major integumental phosphotyrosine‐containing polypeptides have apparent molecular weights of 30, 41, 44, 46, and 54 kDa, respectively. Polypeptides with molecular weights of 62 and 73 kDa were identified as Ser/Thr‐containing phosphoproteins and were shown to exhibit high levels of phosphorylation at the middle stage of larval development. These differences are likely to be due to the higher activation state of the protein tyrosine kinase(s) at the early stages of larval development. Arch. Insect Biochem. Physiol. 50:9–20, 2002. © 2002 Wiley‐Liss, Inc.
Stimulation of trehalose efflux from cockroach (Periplaneta americana) fat body by hypertrehalosemic hormone is dependent on protein kinase C and calmodulin
Authors: Garcha D. Sun, K. , Steele J.E. 
Published: August 2002

AbstractProtein kinase C and calmodulin play key roles in cockroach fat body during activation of phosphorylase and trehalose efflux by HTH‐II. The data support the view that an increase in cytosolic Ca2+ is prerequisite for enhanced activity of protein kinase C and calmodulin. Chelation of Ca2+i with BAPTA blocks HTH‐II‐induced trehalose efflux from the fat body whereas thapsigargin, which raises [Ca2+]i to the same level as HTH‐II, produces only a small, yet significant increase in trehalose efflux. Sphingosine, an inhibitor of protein kinase C, inhibits HTH‐II‐induced trehalose efflux in a concentration‐dependent manner. Trehalose efflux is not activated by the protein kinase C activators OAG or PMA alone but in the presence of thapsigargin both agents increase trehalose efflux to a level comparable to that obtained with HTH‐II. Thapsigargin has only a moderate activating effect on phosphorylase but in combination with OAG produces an activation indistinguishable from that provoked by HTH‐II. Each of the structurally different calmodulin inhibitors, trifluoperazine, W‐7, and calmidazolium, blocks completely the action of HTH‐II on trehalose efflux, thus confirming the importance of calmodulin in HTH‐II initiated trehalose efflux. Arch. Insect Biochem. Physiol. 50:41–51, 2002. © 2002 Wiley‐Liss, Inc.