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  • Chemistry  (5,083)
  • 2010-2014
  • 1995-1999  (2,156)
  • 1985-1989  (2,927)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1401-1419 
    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 effect of blending various methacrylate copolymers on the physical and mechanical properties of poly(vinyl chloride) (PVC) has been investigated. Copolymers of methylmethacrylate with methylacrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate in 80:20 and 50:50 wit methylmethacrylate have been prepared and characterized by nuclear magnetic resonance spectroscopy. Polyblends of PVC and such polyacrylates have been prepared in 80:20 ratio by melt blending technique and characterized by thermomechanical analysis to study the glass transition behavior vis-à-vis the compatibility of these blends. Mechanical properties of these blends revealed a substantial increase in impact strength particularly when long chain acrylate polymers like butyl acrylate and 2-ethyl hexyl acrylates are used; however, there is a decrease in the yield stress and initial modulus. A shift from brittle failure to ductility has been observed in blends of PVC on incorporation of these acrylate copolymers. Scanning electron microscopic studies have been carried out to support these observations.
    Additional Material: 13 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1421-1437 
    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: Studies have been made on the melt rheological properties of poly(vinyl chloride) (PVC) with copolymers of methyl methacrylate (MMA) and methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), and 2-ethyl hexyl acrylate (EHA) at a blending ratio of 80:20. Effect of blend composition on shear stress-shear rate, melt viscosity, melt elasticity, and extrudate distortion have been studied. A significant decrease in the melt viscosity is observed on incorporation of low Tg, acrylate copolymers such as those with BA and EHA, thereby reducing the processing temperature. First normal stress and die swell ratio also decreases with an increase in the side chains of acrylate copolymer. PVC blended with P(MMA-co-BA) and P(MMA-co-EHA) is sensitive to both temperature and shear stress.
    Additional Material: 11 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 33 (1987), S. 2657-2667 
    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 emulsion polymerization of styrene in the presence of an amphoteric emulsifier of amino-acid type, N-lauroyl-N,N-dimethyllysine (DMLL), has been studied at pH 7.0. The polymerization rate increased exponentially with the concentration of DMLL. The concentration of latex particles was proportional to the DMLL concentration to the 0.6 power. The latex particle size decreased with increasing concentration of DMLL. The molecular weight of polystyrene latexes increased with an increase in DMLL concentration. Furthermore, the zeta potentials of latex particles were significantly dependent on the pH, and showed the existence of an isoelectric point at about pH 4.0.
    Additional Material: 6 Ill.
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  • 4
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aspen (Populus tremuloides) and black cottonwood (Populus trichocarpa) organosolv pulps produced in a wide range of solvent composition (between 30 and 70% by volume of methanol) and catalysts (H2SO4 and H3PO4) such that the cooking liquor pH ≤ 3 are easily digested by enzymes. The total yields of hydrolysis residues (pulps) are in the 40-60% range; the acid-catalyzed delignification followed by enzyme hydrolysis can generate 70-88% of the original six-carbon sugars contained in the wood. Glucomannan and arablnogalactan are dissolved into the pulping liquor in the pH range of 2-4.5. Lower pH (≤3) leads to additional solubilization of six-carbon sugars. These sugars may be fermented directly. From the insoluble hydrolysis residues, 36-41% conversions of wood into fermentable sugars were obtained after enzyme hydrolysis; the starting feedstocks contain 50.8 and 46.6% hexosans, respectively, for aspen and black cotton-wood. The kinetics of enzymatic hydrolysis of cellulose can be formally treated as two simultaneous pseudo-first-order reactions in which fast and slow hydrolyses of cellulose occur. Correlations between the glucan digestibility and the effect of the pretreatment have been made. The higher residual xylan content reduces the amount of the rapidly hydrolyzable glucan fraction and lowers the glucan digestibility. The proposed simple kinetic treatment is very helpful in assessing the effect of the pretreatment on pulp enzyme hydrolyzability.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1997-2007 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The inclusion of Re in Pt-Re-Al2O3 reforming catalysts to improve the lifetime is known, but how rhenium functions and how it is disposed in the catalyst remain unclear. These fundamental questions have been attempted in this study by the use of proton-induced X-ray emission and Rutherford backscattering spectrometry (together with electron microscopy and chemisorption studies) to characterize a commercial like catalyst for dehydrogenation of methylcyclohexane.
    Additional Material: 14 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 648-654 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 fillers like clay, silica, and carbon black on the rheological properties of 1,2 polybutadiene has been studied using a capillary rheometer. Silica filled compound exhibited the highest viscosity and clay filled compound the lowest viscosity at all shear rates. The effect of filler loading and temperature on the Theological behavior has also been studied. Smooth extrudates were obtained in most of the cases and die swell was lower for silica and carbon black filled compounds than for clay filled compounds. Rheograms of different 1,2 polybutadiene systems have been found to merge into a master curve using modified viscosity and shear rate functions that contain melt flow index as a parameter.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1329-1341 
    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 effect of electron beam irradiation at different radiation doses (2, 5, 10, 15, and 20 Mrad) on trimethylol propane trimethacrylol propane trimethacrylate (TMPTMA), ethylene vinyl acetate (EVA, 12% vinyl acetate content), and their blends (0.5, 1, 1.5, 2, 2.5, 3, and 5 parts/100 parts EVA) was investigated. An IR study showed some residual unsaturations retained in irradiated pure TMPTMA, while in blends all unsaturations were used up at a very early stage of irradiation. The concentration of the carbonyl group due to air oxidation increased in pure EVA and blends, but it reached a maximum at the 1.5-part TMPTMA level and 5-Mrad dose. some ether linkages were formed during irradiation in pure EVA and the blends, although in pure EVA the concentration of ether linkages reached a maximum at the 2-Mrad dose and then decreased and in the blends it increased with an increase in radiation dose. Gel content showed an increasing trend with an increase in radiation dose, but it increased marginally with TMPTMA level. A blend of EVA with 1 part TMPTMA produced more gel than pure EVA at the same irradiation dose. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 1-7 
    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: Polystyrene (PS) homopolymer is transparent but has low impact strength. High impact PS (HIPS), made by grafting on elastomer, has good impact strength but is not transparent. The operating parameters, namely, polymerization temperature and initiator concentration, during styrene homopolymerization (in suspension) can be modified such that 5-10% of benzene-insoluble PS gel is formed that remains dispersed as very fine to small discrete particles in the continuous PS phase. The resulting polymer retains transparency and impact properties comparable to those of HIPS. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 543-547 
    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: Jute fiber was grafted by acrylonitrile and methylmethacrylate monomers in raw and bleached condition. It was also noted that optimum grafting takes place after about 4 h of grafting. It was also noted that in bleached jute fiber, the grafting percentage is higher at all stages of grafting but the tenacity value at the highest add-on is practically the same as that of raw fiber with much less add-on. The crystalline orientation of the grafted jute fiber was correlated with the fiber tenacity. The moisture regain (%) of the fiber after grafting showed a decreasing trend with an increase in grafting percentage. No structural change of the fiber occurred due to grafting. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 42 (1998), S. 491-499 
    ISSN: 0021-9304
    Keywords: bone regeneration ; osteogenesis ; polymer ; bone morphogenetic protein ; biodegradable ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Drug delivery devices have received considerable interest in the field of tissue engineering due to the advent of proteins that can induce proliferation and differentiation of various cells to form specific tissues and organs, for example, bone morphogenetic protein (BMP-2) for osteogenesis. In this work the delivery of a clinically relevant bioactive factor, recombinant human rhBMP-2, was tested in vivo in a rat ectopic bone induction assay. Contact radiography and radiomorphometry showed significantly more radiopacity (1798 ± 183 mm2 versus 784 ± 570 mm2 radiopaque area/g scaffold) in the BMP scaffolds than controls (p 〈 0.002). De novo woven bone and abundant osteoid formation were confirmed from histological sections while controls contained minimal amounts of tissue. Histomorphometry revealed significantly more bone (124 ± 93 mm2 versus 7 ± 12 mm2) and osteoid (72 ± 43 mm2 versus 20 ± 21 mm2) in the BMP implants (p 〈 0.001). These scaffolds demonstrated the ability to deliver viable rhBMP-2 and to induce bone formation in an ectopic site. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 491-499, 1998.
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