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  • 21
    Electronic Resource
    Electronic Resource
    Long chain branching in ethylene polymerization using constrained geometry metallocene catalyst (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2409-2416 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report an experimental investigation on long chain branching (LCB) in ethylene polymerization with the Dow Chemical's constrained geometry catalyst system, CGC-Ti/TPFPB/MMAO, using a continuous stirred-tank reactor (CSTR) at 140°C, 3.45 × 103 kPa, and a mean residence time (τ) of 4 min. The effects of the catalyst (CGC-Ti) and co-catalyst (TPFPB and MMAO) concentrations on the catalyst activity, polymer molecular weight, and shear thinning were systematically examined. The boron cocatalyst had a great influence on the CGC activity. Increasing the ratio TPFPB/CGC-Ti from 0.66 to 5 gave ethylene propagation rates from 1.65 × 103 to 1.36 × 104 L · mol-1 · s-1. The addition of MMAO appeared to be essential, most likely acting as an impurity scavenger. The LCB polyethylenes showed enhanced shear thinning properties. The melt flow index ratios I10/I2 were in the range of 6.96 to 23.4, with the I2 of 0.172 to 0.681 g/10 min. The weight-average molecular weight Mw was correlated to I2 using a power equation within narrow I10/I2 ranges. The exponential factors were in the range of 4.24 to 6.31. The experimental and calculated Mw's were in a good agreement.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 22
    Electronic Resource
    Electronic Resource
    Effects of spinning conditions on morphology and properties of polyethylene terephthalate fibers spun at high speeds (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 447-458 
    Details
    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: Fiber spinning of polyethylene terephthalate (PET) was studied at take-up speeds ranging from 2000 m/min to 7000 m/min under various spinning conditions. Effects of changes in process variables on the molecular orientation, crystallinity, and properties of as-spun PET fibers are reported. Conventional cross-flow quench in high-speed spinning yields fibers with undesirable crimp and asymmetric structure with respect to the fiber axis. Radial-flow quench eliminates these problems. Changes in other spinning conditions, such as extrusion temperature, throughput or take-up denier, and molecular weight, may also affect the development of PET fiber structure in the high-speed threadline.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440310
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  • 23
    Electronic Resource
    Electronic Resource
    Poly(ethylene terephthalate) melt spinning via controlled threadline dynamics (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 531-552 
    Details
    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: Fiber melt spinning of poly(ethylene terephthalate) (PET) was studied via modification of threadline dynamics. Several techniques were implemented in the high-speed spinning process for the judicious control of threadline dynamics. This included a thermal conditioning zone (TCZ) for controlling the threadline temperature profile and a dydraulic drag bath (HDB) for controlling the threadline spinning stress. Through controlled threadline dynamics, key factors affecting the structure development - namely, temperature, tensile stress, and crystallization time - were manipulated to favor formation of a highly oriented and transversely uniform structure in the spun fibers. This carries the implication that optimum or near-optimum processing conditions are being applied during the structure development period. More specifically, tensile stress in the threadline, independent of temperature, is substantially increased to many orders higher than that ordinarily attained in the normal high-speed spinning process. Concurrently, the temperature crucial to the structure development is being independently optimized and its duration extended to attain a highly oriented structural order. Properties of the spun fibers were found to be correlated with the threadline parameters including cooling profile, tension profile, and strain rate. PET fibers spun via the one-step process with the introduction of the TCZ and HDB possess superior mechanical performance. Structural characterization suggests that the spun fibers have a high amorphous orientation factor and a uniform radial structure distribution. Further on-line studies indicate that structure development in the threadline is completely different from that of the traditional high-speed spinning process. The attenuation profile of the threadline is observed to be dependent of TCZ temperature, residence time in the HDB, temperature of the HDB, and take-up speed. It is believed that for the melt spinning process with the TCZ and the HDB, the threadline dynamics is changed from one controlled by inertia and air drag forces to one controlled by the imposed hydraulic drag.
    Additional Material: 26 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460320
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  • 24
    Electronic Resource
    Electronic Resource
    Effects of water content on the properties of starch/poly(ethylene-vinyl alcohol) blends (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 353-363 
    Details
    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: The physical properties of unmodified starch, poly(ethylene vinyl alcohol), glycerol, and water mixtures are reported. Thermal and melt-flow properties of the preprocessed, physically mixed materials were determined along with the tensile properties and morphology of injection-molded microtensile samples. Melt-flow properties were measured by a capillary rheometer, and the water content was varied from 4 to 18%. The morphology, rheology, and tensile properties are all highly related to the percentage of water present. A transition in the tensile properties and morphology of the blends was observed at approximately 11% moisture content. © 1994 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520301
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  • 25
    Electronic Resource
    Electronic Resource
    Studies on permeation through polymer latex films, I. Films containing no or only low levels of additivesBased on a paper presented at the second meeting of the UK Polymer Colloids Forum 22-23 September 1994, Keele University, UK. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 1-12 
    Details
    ISSN: 0959-8103
    Keywords: polymer latex films ; permeability ; Eudragit® ; poly(methacrylate) ; 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: A range of permeation techniques were employed to investigate the transport mechanisms across polymer films cast from lattices containing either no or only low levels of water soluble leachates such as residual surfactant from polymerisation or added plasticiser essential to film formation. Hydrophilic pathways can provide a mechanism of transport, in addition to partition into and solution-diffusion in the polymer phase. Loss of porosity by low Tg polymers on drying highlights the value of solute probes in studying film morphology.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380101
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  • 26
    Electronic Resource
    Electronic Resource
    Studies on permeation through polymer latex films, III. Modification using soluble polymeric additives (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 23-32 
    Details
    ISSN: 0959-8103
    Keywords: polymer latex films ; film permeability ; Eudragit® ; soluble polymeric film additives ; 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: The influence of two distinct types of water leachable polymeric additives upon the transport properties across polymer latex films is considered. Hydroxypropyl methylcellulose, added as an aqueous solution, and a methyl methacrylate-methacrylic acid copolymer, added as latex particles, are both shown to be more effective than lower molecular weight rapidly water soluble additives, typified by sucrose, in enhancing solute transport and creating pathways for convective diffusion.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380103
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  • 27
    Electronic Resource
    Electronic Resource
    Studies on permeation through polymer latex films, II. Permeation modification by sucrose addition (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 13-22 
    Details
    ISSN: 0959-8103
    Keywords: polymer latex films ; permeability ; convective transport ; Eudragit® ; poly(methacrylate) ; sucrose ; film porosity ; 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 investigation of the effect of leachable sucrose on the permeability of polymer latex films showed that the additive can be used to vary the solute permeability in a systematic manner, as a result of increased free volume resulting from additive leaching. However, the extent of the permeability enhancement is dependent on both the glass transition temperature of the polymer and its ability to sustain porosity and prevent pore reduction by wet sintering and/or film drying, and also the compatibility of the sucrose additive with the polymer. The loading of additive dictates how readily it is leached and, hence, the presence, or not, of continuous porosity through the full thickness of film. Although continuous porosity can be conferred on the film by the sucrose leaching, the resulting porosity still greatly inhibits the permeation of electrolyte, and the film fails well before the level of porosity approaches that required for unimpeded transport.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380102
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  • 28
    Electronic Resource
    Electronic Resource
    Probing the surface chemical structure of some novel poly(ortho esters) prepared with N-methyl and N-phenyl ethanolamine by time-of-flight secondary ion mass spectrometry (ToF-SIMS) (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 293-301 
    Details
    ISSN: 1042-7147
    Keywords: Poly(ortho esters) ; Biodegradable polymer ; Surface chemical analysis ; Time-of-flight secondary ion mass spectrometry (ToF-SIMS) ; 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: The surface chemical structures of a series of novel poly(ortho ester) homopolymer and copolymer films prepared using N-methyl- and N-phenyl-ethanolamine (MDE and PDE) have been investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Systematic fragmentation patterns were observed within the ToF-SIMS spectra up to m/z = 1600, which were readily interpreted in terms of the polymer structures. Cations were detected which could be assigned to structures arising from the diols, the ortho ester species and diads, triads etc. of the monomer, from both the homopolymer and the random portion of the copolymer chains. The analysis of the proposed ion structures suggested two major mechanisms of fragmentation based on the cleavage of the ortho ester bonds involving either the exocyclic or the endocyclic alkoxy group. The Tof-SIMS peak area ratios for ions diagnostic of the diols and the ortho ester species reflected the bulk copolymer composition in a semi-quantitative fashion. The observation of such relationships for high mass cations (up to m/z = 500) is particularly noteworthy and has not been reported previously. These studies allow a dramatic insight into the surface chemical structure of these poly(ortho esters), information which has formed the foundation of current investigations on the mechanisms of the acid-catalysed surface degradation of these polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030603
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  • 29
    Electronic Resource
    Electronic Resource
    Utility of pulsed-field gradient - HMBC indirect detection NMR experiments for polymer structure determinationPresented at ‘MacroAkron '94, 35th IUPAC Symposium on Macromolecules’, Akron, Ohio, 11-15 July 1994. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 177-185 
    Details
    ISSN: 0959-8103
    Keywords: NMR ; pulsed-field gradient ; heteronuclear multiple bond correlation ; block copolymers ; 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: The utility of pulsed-field gradient (PFG)-heteronuclear multiple bond correlation (HMBC) 2D NMR experiments for characterizing polymer structure is demonstrated. Heteronuclear multiple quantum coherence (HMQC) and HMBC indirect detection experiments provide correlations indicating the presence of one-bond and two-or three-bond connectivities, respectively; this information is vital for polymer structure determination. When HMBC methods are combined with PFG techniques artifacts are eliminated which normally limit the utility of HMBC. The elimination of these artifacts lowers the detection limit by almost two orders of magnitude, making it feasible to detect signals from the small number of repeat units bonded to defect structures, chain ends, branch points and block junctions, despite the presence of much larger resonances from the main-chain repeat units. Spectra of poly(isobutylene-b-butadiene) diblocks and poly(isoprene-b-styrene) diblocks are used to illustrate these advantages.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360208
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  • 30
    Electronic Resource
    Electronic Resource
    The analysis of the surface chemical structure of biomedical aliphatic polyanhydrides using XPS and ToF-SIMS (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1597-1605 
    Details
    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: The surface chemical structure of a range of aliphatic polyanhydride films has been examined using XPS and ToF-SIMS. The XPS data confirms the purity of the surface, and the experimental surface elemental ratios are in good general agreement with the known stoichiometry of the polyanhydrides. The ToF-SIMS spectra of the polyanhydrides are shown to be significantly different. The SIMS data conforms to a systematic fragmentation, in both negative- and positive-ion SSIMS spectra, occurring throughout the entire series of polyanhydrides examined. Radical cations are observed in the positive-ion spectra. These results are discussed in terms of the general fragmentation patterns observed in the SIMS analysis of polymers. The combined use of ToF-SIMS and XPS is shown, to provide a detailed insight into the interfacial chemical structure of these polyanhydrides.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420613
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