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  • 1
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper describes the cationic polymerization of 3-isopropenyl-α,α′-dimethylbenzyl isocyanate (TMI) and its copolymerization with isopropenylbenzene (IPB) in order to synthesize materials with varying amounts of NCO side groups. These polymers were characterized by FTIR, 1H-NMR, elemental analysis and DSC. Their structure showed an essentially random incorporation of TMI. Preliminary reactions of the copolymers with cellulosic fibers are also reported.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-882X
    Keywords: surface modification ; oligomeric reagents ; polymeric reagents ; anhydrides ; isocyanates ; Fourier-transform Infrared Spectroscopy ; elemental analyses ; scanning electron microscopy ; X-ray photoelectron spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The surface modification of various cellulosic materials was studied in heterogeneous conditions using different grafting agents bearing anhydride or isocyanate reactive groups. Some of these reagents were oligomeric, others polymeric and most were chosen so as to provide a non-polar character to the surface of the fibres in view of their possible use as reinforcing agents in composites based on polymeric matrices. The success of these chemical modifications was assessed by Fourier-transform Infrared Spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and elemental analysis. The accessibility of the superficial OH groups varied as a function of the coupling agent in terms of both molecular size and chemical nature and ranged between 1 and 3% of the total hydroxy groups borne by the initial cellulose sample.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 1519-1527 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric permittivity and loss of Bisphenol-A-polycarbonate (PC) was measured over the frequency range 100 Hz to 200 kHz and temperature range 77-383 K. One sub-Tg relaxation peak is observed which rapidly broadens with a decrease in temperature. This is attributed to a progressive separation of the γ and β peaks, which at high temperatures are merged to form one peak of high strength. The strength of the sub-Tg relaxations decreases on physical aging of PC but is increased if the sample is quenched from a temperature above its Tg. Slowly cooled PC has a lower strength of its sub-Tg relaxation than a quenched specimen. The thermal history of PC affects the magnitude of its sub-Tg relaxation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Structural relaxation of glassy poly(methyl methacrylate) (PMMA) was studied with several techniques: differential scanning calorimetry (DSC), volumetry by thermomechanical analysis (TMA) and mechanical spectroscopy. A theory is proposed in order to interpret the data in a unique theoretical framework. This theory is developed on the basis of two main physical assumptions: (i) the existence in amorphous polymers of quasipunctual defects whose concentration decreases during structural relaxation, and (ii) the occurrence of hierarchical correlation effects conditioning molecular mobility. As a first approximation a self-consistent semiquantitative description of the results is obtained, i. e., the experimental results obtained for the different quantities on PMMA can be accounted for employing always the same set of model parameters. However, it seems that a significant difference exists between the relaxation times associated with the different experimental techniques.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 285-290 
    ISSN: 1042-7147
    Keywords: polymer films ; thermomechanical properties ; emulsion polymerization ; functional and crosslinkable monomers ; rubber elasticity ; 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: Batch emulsion polymerization was used in order to obtain latexes from a mixture of butyl acrylate (ca. 90% mole), and a hydrophobic crosslinkable functional monomer called N-isobutoxymethyl acrylamide (ca. 10% mole). Films were then cast from these latexes, and their thermomechanical properties were studied before and after a heat treatment intended to provoke crosslinking of the functional groups. The differential thermal analysis and the dynamic mechanical analysis of the film samples proved that the functional monomer copolymerized with butyl acrylate; the dynamic mechanical analysis revealed also that crosslinking took place after the heat treatment. Different kinds of high strain experiments (among which there were stress relaxation tests) were carried out in a tensile testing machine Important differences were thus shown to appear between the “as-dried” and “annealed” samples. In the case of stress relaxation experiments, simple mechanical models were used in order to fit the experimental data, both during the stretching experiment and the stress relaxation following it. The analysis of the high-strain experiments and their simulation led to the conclusion that the films contained high molecular weight polymers having a broad molecular weight distribution, and that their crosslinking enhanced the entropic elastic behavior, even though a viscoelastic, large relaxation time contribution was kept; the hypothesis of its coming from a trapped-entanglement effect was proposed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 296-300 
    ISSN: 1042-7147
    Keywords: polymer films ; thermomechanical properties ; emulsion polymerization ; coalescence ; scanning electron microscopy ; small angle neutron scattering ; 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 two-stage emulsion polymerization procedure was used in order to obtain core-shell polymer particles having a core of polystyrene (PS), covered by a shell of either pure poly(butyl acrylate) (PBA) or a methacrylic acid-functionalized PBA. Films were then cast from these latexes, and their properties were studied without further treatments (“as-dried” films), as well as after a 3 hr heat treatment intended to provoke the coalescence of PS domains (“annealed” films). “As-dried” and “annealed” film samples were studied by dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and small angle neutron scattering (SANS). DMA and SEM results, as described in previous works, showed that for unfunctionalized films, the percolated PS domains coalesced under the annealing treatment, while for the functionalized films, they did not. On the other hand, SANS results presented here showed that even in the case of functionalized films, the presence of coalescence could be detected. It was concluded that while DMA and SEM reveal large-scale modifications provoked by the heat treatment, SANS is capable of detecting very smallscale changes which do not have a direct effect on the bulk physical properties of the samples.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2211-2224 
    ISSN: 0887-6266
    Keywords: starch ; mechanical properties ; percolation ; clustering ; diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The use of starch microcrystals as biodegradable particulate filler is evaluated by processing composite materials with a weight fraction of starch ranging from 0 to 60%. In a previous work [Macromolecules, 29, 7624] the preparation technique of a colloidal suspension of hydrolyzed starch and the processing of composite materials by freeze drying and molding a mixture of aqueous suspensions of starch microcrystals and synthetic polymer matrix were presented. Starch microcrystals with dimensions of a few nanometers were obtained from potatoes' starch granules, and it was found that this filler produces a great reinforcing effect, especially at a temperature higher than Tg of the synthetic matrix. Classical models for polymers containing nearly spherical particles based on a mean field approach could not explain this reinforcing effect. The morphology of these nanocomposite systems is discussed in light of aggregate formation and percolation concepts. The sorption behavior of these materials is also performed. Starch is a hygroscopic material, and it is found that the composites absorb more water, as the starch content is higher. The diffusion coefficient of the penetrant is predicted from modified mechanical three branch series-parallel model based on a percolation approach. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2211-2224, 1998
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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