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  • Polymer and Materials Science  (11)
  • Chlorophylls
  • Surface physics, nanoscale physics, low-dimensional systems
  • 1990-1994  (11)
Collection
Keywords
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Activation energy for urethane-linkage formation. An improved calculation from the differential scanning calorimetry data (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1579-1592 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differential scanning calorimetry (DSC) has been utilized in several studies on polymerization kinetics, at different heating rates. However, there are several factors affecting the precision of kinetic parameters. In this work, the activation energy of urethane-bond formation between 2,6-tolylene diisocyanate and diethylene glycol is reported, the latter being in excess in order to minimize problems such as thermal transitions and incomplete reaction in the final step. The DSC technique was applied at different heating rates. Both the equal conversion and equal conversion rate options of the method are discussed. The latter appears to be a more adequate option for the system studied here. The results obtained show a good agreement with the model used.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280623
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical, thermal, and photo properties of poly(phenylene vinylene) precursors: I. Laser-induced elimination reactions in precursor polymer films (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 959-970 
    Details
    ISSN: 0887-6266
    Keywords: laser-induced processes in conducting polymer precursors ; interaction of dyes with polyelectrolytes ; lithography ; microelectronics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The elimination reaction of polyelectrolyte films of poly(phenylene vinylene) precursor polymers into the fully conjugated chain was induced by irradiation with an Ar+ laser emitting at 514.5 nm. The experiments were conducted using as cast precursor polyelec-trolyte films of both the unsubstituted poly(phenylene vinylene), H-PPV, and its 2,5-dimethoxyphenylene derivative, DMEO-PPV. Precursor polymer films impregnated with an azosulfonic dye, which had a strong absorption at the laser emission wavelength, were also irradiated. The elimination reaction was followed by comparing the elemental analysis and the infrared and visibleultraviolet spectra of the irradiated and nonirradiated areas. With the unsubstituted PPV film no elimination was detected even at power fluence levels up to approximately 350 W/cm-2, but elimination and conversion to the conjugated polymer could be observed at 10 W/cm-2 when the dye was present. For DMEO-PPV the elimination reaction occurred with or without dye impregnation, and similar marking threshold values were measured in both cases. The molecular mechanism used to explain such observations and the possible application in the area of microelectronics are also discussed. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310806
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  • 3
    Electronic Resource
    Electronic Resource
    Poly(vinyl alcohol)/poly(acrylic acid) blends: Miscibility studies by DSC and characterization of their thermally induced hydrogels (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 777-792 
    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: Binary blends of poly(vinyl alcohol) (PVA) with poly(acrylic acid) (PAA) and polyacrylamide (PAAm) were characterized by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and infrared spectroscopy (IR). Molecular weight, blend composition, and heating time at 150°C were the variables used. Results obtained by DSC indicated that PAA/PVA blends are miscible in the full range of composition. Similarly, TGA traces showed that thermal stability was higher for blends than for pure polymers. Blends of PVA with high molecular weight PAA exhibited a hydrogel behavior after drying at relatively low temperature (100°C), whereas blends containing low molecular weight PAA behaved as hydrogels only after they were heated at 150°C. Hydrogel character was increased for these two PVA/PAA blends with the heating time at higher temperature (150°C). IR spectra revealed that esterification took place in these blends after thermally treated at this temperature. In contrast, addition of glyoxal in combination with heating was necessary to produce hydrogels from PAAm/PVA blends. Furthermore, the crosslinking degree of these hydrogels was estimated from their absorbency values by applying the Flory-Rehner equation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070500505
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation and characterization of hydrogels obtained by grafting of acrylonitrile onto cassava starch by ceric ion initiation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 53-59 
    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: Graft starch-polyacrylonitrile copolymers have been obtained from cassava starch (yucca starch or tapioca), which was pre-heated at 65 and 95°C for different lengths of time. The copolymerization was carried out by using ceric ion as initiator at different concentrations (2.0 to 8.0 mmol/L) and also varying both the length of time of copolymerization and the ratio of monomer to starch. The composition, or grafting parameters, of all the obtained copolymers was determined by weight difference after they were extracted with dimethylformamide and hydrolyzed with an acidic solution. Samples of these copolymers were also hydrolyzed with an aqueous solution of potasium bydroxide to produce the corresponding hydrogels, and its absorbency in water was determined. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070470108
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  • 5
    Electronic Resource
    Electronic Resource
    Coconut husk lignin. III. Reactivity of alkaline extracts with formaldehyde (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 37-44 
    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: In this article we report results of the evaluation of the reactivity of polyphenolic extracts of coconut husk with formaldehyde in both acidic and alkaline media. The objective of this evaluation was to determine if the extracts could be used in the preparation of phenol-formaldehyde-type resins. Extracts were obtained using aqueous solutions of NaOH (with and without anthraquinone) and NH4OH. Because of their low Stiasny's Number values, these extracts are not suitable for phenol-formaldehyde resin preparation in acidic conditions unless they are mixed with phenol or phenolic derivatives. Nevertheless, extracts obtained with NaOH, especially at 100 and 120°C, showed sufficient reactivity with form-aldehyde in basic conditions and may therefore be considered suitable for resin preparation in an alkaline medium. The resins were characterized using infrared spectroscopy (IR), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). A transition temperature prior to decomposition was not detected; their thermal stability was similar to phenol-formaldehyde-type resins. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070470106
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  • 6
    Electronic Resource
    Electronic Resource
    Coconut husk lignin. II. Characterization by infrared and nuclear magnetic resonance spectroscopy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 645-653 
    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: Results of the characterization of coconut husk lignin by infrared (IR) and proton nuclear magnetic resonance (H-NMR) spectroscopy are presented. Lignin was extracted with both alkaline and organosolv liquors. The IR spectra of dioxane lignin were very similar to those reported for hardwood lignins. Furthermore, these results combined with those obtained from the H-NMR studies suggest that coconut husk lignin can be classified into the Lm-type lignins. These lignins are characteristic of the monocotyledon class, of which the coconut palm is a member. The H-NMR studies showed that anthraquinone significantly inhibited the occurrence of lignin condensation during the alkaline extraction with sodium hydroxide solutions. This inhibition was more intense in the lignin extracted at 150°C than in that extracted at 100°C.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450411
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  • 7
    Electronic Resource
    Electronic Resource
    Mechanical properties of acrylate networks formed by visible laser-induced polymerization. I. Dependence on photopolymerization parameters (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 931-937 
    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 mechanical properties of network molecular systems, prepared through visible (Ar+) laser-induced polymerization of multifunctional acrylates, were studied as a function of some of the photopolymerization parameters. The properties investigated were the Young's modulus of elasticity and the stress-at-break, both derived from the stress versus strain test of dogbone-shaped photopolymerized samples. The parameters studied included the dye and co-initiator concentrations, and the laser power. We also compared the mechanical properties of samples made using different types of fluorone dyes and using two different amines as co-initiator. Better polymers are formed by the dyes with low fluorescence quantum yield. The three photopolymerization parameters modify the mechanical properties in a very similar way: they initially tend to increase both the Young's modulus and the stress-at-break but have a deleterious effect on the material strength if used in excess. N-phenylglycine, NPG, was shown to form stronger polymers (higher Young's modulus) than if N,N-dimethyl-2,6-diisopropylaniline, DIDMA, was used as co-initiator. We discuss the possible molecular mechanisms for such observations. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510515
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  • 8
    Electronic Resource
    Electronic Resource
    Dielectric constant, optical transmission, and thermal diffusivity monitoring of iodine-impregnated polystyrene films (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 1361-1373 
    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: A simple method for the iodine doping of atactic polystyrene films is described. The marked changes in the physical properties of the polystyrene films, such as dielectric constant, optical absorption coefficient, and thermal diffusivity, are presented as a function of the doping time. The results show strong evidences of the onset of an order-disorder transition as a function of the doping time.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070390612
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  • 9
    Electronic Resource
    Electronic Resource
    Coconut husk lignin. I. Extraction and characterization (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 633-644 
    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: Recently lignin has been the object of a renewed interest because of the need to use raw materials from renewable resources. One such resource is coconut husk, a material usually discarded during the copra extraction process. Due to its high lignin content, coconut husk has been recognized as having a variety of applications. Therefore, it is important to know the approximate structure of coconut husk lignin and those variations introduced by different isolation methods. This work reports a general characterization of coconut husk lignin. Results are given of the contents of hydroxyl and noncondensed guaiacyl units, the extractability of the lignin in alkaline and “organosolv” media along with thermal properties of the extracted lignins. The extraction system of NaOH-anthraquinone at 150°C was most conveniently based on the relatively low amount of condensed lignin generated.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450410
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  • 10
    Electronic Resource
    Electronic Resource
    Blends of cellulosic esters with poly(caprolactone): Characterization by DSC, DMA, and WAXS (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 1141-1159 
    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: Binary blends of poly(caprolactone) (PCL) with cellulosic esters [cellulose diacetate (CDA), cellulose acetate-butyrate (CAB), and cellulose triacetate (CTA)] were studied by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and wide-angle X-ray scattering (WAXS) techniques, and qualitative comparison was made with the results obtained by polarizing optical microscopy. The PCL-CAB system was proved to be partially miscible, whereas PCL-CDA and PCL-CTA appeared to be immiscible. A double-melting behavior was showed for PCL-CAB and PCL-CTA blends. As these peaks did not shift by varying the heating rate of DSC runs, this behavior can be due to melting of two populations of crystals of PCL, which may be different in size. On the other hand, blends of PCL containing a low amount of CAB or CDA seem to develop more crystallinity for the PCL than this polymer alone. The solvent seems to have a certain influence on the thermal and morphological behaviors of the as-cast blends of these three systems, affecting the extent of crystallinity of PCL, as well as its Tm and ΔHf. This finding is discussed in the light of WAXS and polarizing optical microscopy results. © 1994 John Wiley & Sons, Inc.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540818
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