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  • 1
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0959-8103
    Keywords: poly(esterurethane) ; copolyamide segments ; thermal and mechanical properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Thermoplastic polyurethane elastomers (TPUs) from diol-terminated poly(ethylene adipate) (PEA), 1,4-butanediol (BD) and 4,4′-diphenylmethane-diisocyanate (MDI) were modified by copolymerizing with diamine-terminated nylon-6/6,6 copolyamide (CPA) oligomers. The effects of content and molecular weight of CPA segments on the thermal and mechanical properties of TPU were studied. PEA segments showed enhanced crystallization when some of the hard segments were replaced by CPA segments, showing weaker CPA-PEA interaction. The crystallinity of the hard segments was reduced, probably due to some interaction and phase mixing between hard and CPA segments. The modulus of TPU also decreased, more markedly with CPA segments of higher molecular weight.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 1042-7147
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Small-angle neutron scattering studies have been used to clarify several aspects of the internal structure of latexes and subsequent film formation modes. This paper reviews work both around the world and at Lehigh University on those subjects. Two points have been made clear: (1) The appearance of core-shell phenomena in latexes depends on the size of the polymer chain to that of the latex particle; the phenomenon is most marked when the radius of gyration of the chain is about one fifth as big as the latex radius. (2) Strength build-up during film formation depends on the extent of interdiffusion of the chains. For moderate molecular weights, interdiffusion distances of one radius of gyration yield maximum strength. For both moderate (250,000 g/mol) and high (2,000,000 g/mol) molecular weights, full strength was achieved in two hour's annealing time at 144°C.
    Additional Material: 11 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 187-200 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental study has been carried out to investigate the effects of spinning conditions on the shape of fibers spun through noncircular spinnerette holes, namely, rectangular holes, trilobal holes, and round holes with lugs. For the study, bench-scale apparatuses of wet spinning and melt spinning were used which had been constructed in connection with an earlier study by Han. In the wet-spinning experiment, the spin dope used was an aqueous solution of polyacrylonitrile (PAN) consisting of approximately 10% polymer and 40% sodium thiocyanate (NaSCN), and the spin dope was spun into aqueous solutions of NaSCN. In the melt-spinning experiment, polystyrene was used. The variables investigated were: size and shape of the spinnerette hole, coagulating bath concentration, throughput rate, and jet stretch. It has been found in wet spinning that, for a given shape of spinnerette hole, the fiber shape is most strongly affected by jet stretch and relatively little by the bath concentration and throughput rate. Also determined in the wet-spinning experiment was the maximum jet stretch at which thread breakage occurs. It has been found that the maximum jet stretch decreases as bath concentration is increased.
    Additional Material: 13 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 3257-3276 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blown-film extrusion experiments were carried out to investigate the elongational flow behavior of viscoelastic polymer melts at different melt temperatures. Materials chosen for study were high-density polyethylene, lowdensity polyethylene, and polypropylene. In the study, isothermal blown-film extrusion experiments were carried out in which the molten blown film traveled upward through a heated chamber of about 13 in. in length maintained at the same temperature as the melt. Axial tension was measured at the take-up roller, the axial profiles of bubble diameter were determined by a photographic technique, and, from the samples collected, the variation in the film thickness along the axial direction was found. These measurements were used later to determine the elongational viscosity, using the force balance equations. It was found, in the experiment, that a careful control of the pressure difference across the thin film permitted one to maintain the bubble diameter constant, and, therefore, depending on the choice of the extrusion conditions, either a uniaxial or biaxial elongational flow was made possible. The experimental results show that, depending on the materials, elongation rate, and melt temperature tested, the elongational viscosity may decrease or increase with elongation rate, and may also stay constant independent of elongation rate. It was observed that the data of elongational viscosity obtained under uniaxial stretching in blown film extrusion is consistent with the data of elongational viscosity obtained earlier by use of the melt-spinning operation.
    Additional Material: 18 Ill.
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  • 6
    ISSN: 0887-6266
    Keywords: polystyrene, chain scission in fracture of ; fracture of glassy polymers, energy consuming micromechanisms ; chain scission mechanism in fracture of polystyrene ; glassy polymers, chain scission and fracture of ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The number of chain scissions per unit area that occur during the fracture of partially annealed latex films from Mn ≃ 180,000 g/mol polystyrene particles of about 275 Å radius were measured and correlated to annealing times. A curve with four regimes was found. At short annealing times the curve is nearly flat, in what is called the chain pull-out regime. In the second regime, the number of chains broken per unit area increases with a 0.8 power of annealing time as entanglement of the diffusing polymer chains increases in neighboring host particles. This is in good agreement with Wool's theory which predicts a 0.75 power dependence. Then, after reaching a peak, the number of scissions decreases in the third regime, indicating a change in fracture mechanism. The number of chain scissions increases again in the fourth regime, as final healing of the film interface takes place. Fracture surface analysis reveals a rough surface for short annealing times and a smooth surface for longer annealing times. The number of polymer chain scissions per unit area of fracture surface showed no dependence on initial molecular weights for t ≫ τr where t and τr are annealing and relaxation times, respectively. The number of chain bridges crossing a unit area of interface was suggested as the basic molecular property. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 7
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polymerization of N-isopropylacrylamide (NIPAAm) was performed in the presence of β-cyclodextrin (β-CD) [or hydroxypropyl-β-cyclodextrin (HOP-β-CD)]. The formation of an inclusion complex between PNIPAAm and β-CD was confirmed by FT-IR, 1H NMR and 2D-NOESY NMR. It was found that the cloud point (CP) of poly(N-isopropylamide) (PNIPAAm) in the PNIPAAm/β-CD complex in aqueous solution increased up to about 57°C whereas that in the PNIPAAm/β-CD blend is about 33°C. The CP of PNIPAAm in the PNIPAAm/β-CD complex is higher than that in the PNIPAAm/HOP-β-CD inclusion complex. IR and NMR results suggest that PNIPAAm chains are included in CD cavities.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 13 (1994), S. 201-205 
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A rheological technique of determining molecular weight distribution (MWD) of ultra high MFR polypropylene (PP) is presented. The development of this new technique was needed for two reasons. First, the advent of high activity catalyst made possible the direct polymerization and thus the commercialization of very high MFR PP. Secondly, the polydispersity index (PI) measurement based on crossover modulus from G′ and G″ curves, which was developed by Zeichner and Patel in 1981, was proven to be inapplicable to resins with MFR higher than about 40, due to instrument limitations. This new technique utilizes G′ and G″ data at low frequencies which are obtained from a dynamic frequency sweep test at 200°C. PI values, a measure of MWD, determined by this method are proven to have an excellent correlation with those obtained by gel permeation chromatography (GPC). This method has been very useful in determining MWD of melt brown fiber resins whose MFR is normally between 30 and 1000. It has also been used as a quality control tool during the resin production in a commercial plant. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: alkoxyallene monomers ; cationic photopolymerization ; isomerization of propargyl ethers ; diaryliodonium salts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of cationically polymerizable mono-and difunctional alkoxyallene monomers have been prepared via the straight forward base catalyzed isomerization of the corresponding propargyl ethers. Rate studies conducted using real-time infrared spectroscopy showed that these monomers exhibit high reactivity in photoinitiated cationic polymerization. Monomers bearing a single alkoxyallene group undergo rapid polymerization to yield crosslinked polymers indicating that both double bonds react during polymerization. A mechanism has been proposed that explains this observation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 183-190 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational free energy calculations using an empirical potential ECEPP/3 (Empirical Conformational Energy Program for Peptides, Version 3) were carried out on angiotensin II (AII) of sequence Asp-Arg-Val-Tyr-Ile-His-Pro-Phe to find the stable conformations of the free state in the unhydrated and the hydrated states. A conformational analysis of the unhydrated state was carried out using the buildup procedure. The free energy calculation using the hydration shell model was also carried out to obtain the stable conformation of the hydrated state. The calculated stable conformations of AII in both states have a partially right-handed α-helical structure stabilized by short- and medium-range interactions. The similarity between the lowest free energy conformations of the unhydrated and hydrated states suggests that the hydration might not be important to stabilize the overall conformation of AII in a free state. The absence of any intramolecular interaction of the Tyr side chain suggests the possible interaction of this residue with the receptor. In this study, we found that the low free energy conformations contain both the parallel-plate and the perpendicular-plate geometries of the His and Phe rings, suggesting the coexistence of both conformations. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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