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Reduced Viscosity (reduced + viscosity)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Degradation of aramid fibers under alkaline and neutral conditions: Relations between the chemical characteristics and mechanical properties

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010
G. Derombise
Abstract Aramid fibers are high-performance materials that have been used in various applications such as heat and cut protection, composites, rubber reinforcement, ropes and cables, and fabrics; today their use is proposed in geotextiles for alkaline ground reinforcement, and they have been used in cables for marine applications for a few years. However, there is a lack of experience with the long-term behavior of aramid fibers in wet and alkaline environments. Aging studies were therefore performed on Twaron 1000 fibers under different conditions (sea water, deionized water, pH 9, and pH 11). Hydrolytic degradation was evaluated with Fourier transform infrared and viscosimetry measurements, which were correlated with tensile test measurements. The tensile strength followed a logarithmic evolution with the aging time, whereas the modulus remained constant. A linear relation between the tensile strength and the reduced viscosity of the hydrolytically aged fibers is highlighted. Aging indicators are proposed that allow the hydrolytic degradation to be quantified. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Study on the long-term thermal-oxidative aging behavior of polyamide 6

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
Ying Shu
Abstract The long-term thermal-oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Comparison of specific interactions in P4VP/PSCA and PS4VP/PSCA blends and complexes

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008
Naima Bouslah
Abstract The compatibilization of an immiscible polymer system polystyrene/poly(4-vinylpyridine) has been induced by the introduction of carboxylic acid groups within the polystyrene chains. Poly(styrene- co -cinnamic acid), PSCA, copolymers were used to prepare blends and complexes with poly(4-vinylpyridine), P4VP, and in a second time with poly(styrene- co -4-vinylpyridine), PS4VP, copolymer in order to reduce the density of the interacting groups. The miscibility of the systems has been ascertained by DSC, which revealed that both blends and complexes exhibit a single glass transition temperature indicating their single phase nature. The Tgs of the complexes of PS4VP with PSCA15, containing 15 mol % of cinnamic acid content, were higher than those of the corresponding blends indicating that stronger interpolymer interactions were developed in the complexes. Furthermore, the application of the Kwei equation suggested that P4VP interacts more strongly with PSCA15 than does PS4VP. FTIR spectra revealed the development of hydrogen bonding within the PS4VP/PSCA system and both hydrogen bonding and ionic interaction in the P4VP/PSCA blends whereas the same interactions were expected in both systems. This observation confirmed the stronger ability of P4VP to interact with PSCA copolymer. The viscosimetric study showed both positive and negative deviations of the reduced viscosity of the blends from the additivity law confirming the presence of specific interactions within the blend solutions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Synthesis of azobenzene-functionalized two-arm, three-arm and four-arm telomers using polyfunctional chain transfer agents

POLYMER INTERNATIONAL, Issue 11 2009
Md Zahangir Alam
Abstract BACKGROUND: Star-shaped polymers are very attractive because of their interesting properties such as reduced viscosity, good solubility, low glass transition temperature and fast response to external stimuli. The incorporation of azobenzene moieties in star-shaped polymers could significantly widen their potential applications in various optical devices. One of the most important properties of the azobenzene chromophore is its reversible trans,cis photoisomerization induced by UV or visible light. Photoisomerization induces conformational changes in azopolymer chains, which in turn lead to macroscopic variations in chemical and physical properties of the surroundings and media. RESULTS: This study reports the synthesis of azobenzene-functionalized two-, three- and four-arm telomers via free radical telomerization using the di-, tri- and tetrafunctional chain transfer agents 1,2- and 1,4-benzenedimethanethiol, trimethylolpropane-tris(2-mercaptoacetate) and pentaerythritol-tetrakis(3-mercaptopropionate), respectively, in the presence of azobisisobutyronitrile. Azotelomers were characterized using gel permeation chromatography and 1H NMR and Fourier transform infrared spectroscopy. Thermal phase transition behaviors were investigated using differential scanning calorimetry and polarized optical microscopy. Azotelomers synthesized in this study showed reversible photoisomerization and a fast generation of birefringence. CONCLUSION: Considering the photoisomerization behavior and birefringence of the two-, three- and four-arm azotelomers, it can be concluded that they could be potential candidates for use in various optical devices. Copyright © 2009 Society of Chemical Industry [source]