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  • Binding Sites  (61)
  • DSC  (59)
  • American Association for the Advancement of Science (AAAS)  (61)
  • Springer  (59)
  • Elsevier
  • 2020-2024
  • 1995-1999  (120)
  • 1997  (120)
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  • American Association for the Advancement of Science (AAAS)  (61)
  • Springer  (59)
  • Elsevier
  • Wiley-Blackwell  (8)
Years
  • 2020-2024
  • 1995-1999  (120)
Year
  • 1
    ISSN: 1572-882X
    Keywords: cellulose alkyl esters ; poly(∈-caprolactone) ; blends ; miscibility ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulose alkyl esters, CELL- OCOCnH2n+1(n = 1 ∼ 6), were synthesized by a homogeneous reaction of cotton cellulose with different acyl chlorides in N,N-dimethylacetamide--lithium chloride solution. The miscibility of the esterified celluloses with poly(∈-caprolactone) (PCL) was investigated, mainly through thermal analysis by differential scanning calorimetry (DSC). A polymer pair, cellulose butyrate (CB)/PCL, showed the highest miscibility of all the binary blends examined here; this is usual when relatively high-substituted esters (DS ≥ 2.0) are used as the respective component. The butyl ester derivatives with DS ≤ 1.5 showed poor miscibility with PCL
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1017
    Keywords: Key words Phosphatidylcholine ; Phosphatidylglycerol ; DSC ; Phase diagrams ; Miscibility ; Nonideality parameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The miscibility of phosphatidylcholine (PC) and phosphatidylglycerol (PG) with different chain lengths (n = 14, 16) was examined by differential scanning calorimetry (DSC) at pH 2 and pH 7. The determination of the coexistence curves of the phase diagrams was performed using a new procedure, namely the direct simulation of the heat capacity curves as described recently (Johann et al. 1996, Garidel et al. 1997). From the simulations of the heat capacity curves first estimates for the nonideality parameters for nonideal mixing as a function of composition were obtained and phase diagrams were constructed using temperatures for the onset and offset of melting which were corrected for the broadening effect caused by a decrease in cooperativity of the transition. In most cases, the composition dependence of the nonideality parameters indicated nonsymmetric mixing behavior. The phase diagrams were further refined by simulations of the coexisting curves using a four-parameter model to account for nonideal and nonsymmetric mixing in the gel as well as in the liquid-crystalline phase. The mixing behavior of the systems was analyzed as a function of pH and chain length difference to elucidate the effect of these two parameters on the shape of the phase diagrams. At pH 7 the phase boundaries are much closer together and a narrower coexistence range is obtained compared to the corresponding phase diagrams at pH 2. For DPPC/DMPG at pH 2, the shape of the phase diagram and the strongly positive nonideality parameter ρ 1 for the liquid-crystalline phase indicates an upper azeotropic point. This indicates an unusual behavior of the system, namely more pronounced clustering of like molecules in the liquid-crystalline phase compared to the gel phase.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8943
    Keywords: DSC ; polyethylenes ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In thermal analysis polyethylenes can be characterized by their melting temperature. With the polyethylene mixtures studied, we obtained the best results during solidification. Crystallization temperature decreased in the order: high density PE, low density PE linear, radical low density PE. Calorimetric measurement of crystallization enthalpies allowed the determination of the composition of each of the polyethylenes, in regenerated and recycled mixtures in relation with the frame of the plastic waste valorisation process. The rate of crystallization obtained from X-ray diffraction spectra of these polymers is function of their volumic mass. A good agreement has been observed between these two techniques.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 79-85 
    ISSN: 1572-8943
    Keywords: cross-linking degree ; DSC ; enthalpy relaxation ; epoxy resins ; physical aging ; reactive diluent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy loss,δH, at an equivalent annealing temperatureT a=T g-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofδH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent activation energy,δh *. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length of cross-link onrrpd and δh* was studied.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 149-154 
    ISSN: 1572-8943
    Keywords: DSC ; heterogeneity in polymer network ; poly(methacrylic acid)-net-poly(oxytetramethylene) ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract TG and DSC were carried out on PMAA-net-POTM in order to elucidate the relation between the heterogeneity and the thermal changes; moreover, TG and DSC were carried out on PPOTMDM and PMAA to compare the results. The onset temperature in the last stage in the TG curve of PMAA-net-POTM increases as the concentrations of DMF and POTMDM in the polymerization decrease. This is explained in terms of plasticizers effects. A single peak due to fusion of POTM chains appears in the DSC curves of most copolymers. However, it is not seen in the DSC curves of copolymers with high heterogeneity. This is explained in terms of the freezing of POTM chains by frozen heterogeneous moieties.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 177-182 
    ISSN: 1572-8943
    Keywords: bismaleimide resin ; CTBN ; curing behaviour ; DSC ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bismaleimide resin (Compimide 353) was modified with the liquid elastomer carboxyl-terminated acrylonitrile butadiene (CTBN). The prereaction synthesis and curing of the CTBN-bismaleimide resin is discussed. The structure of the modified resin was identified by IR and NMR spectroscopy. The basic curing mechanism is also discussed. DSC and TG were used to study the curing behaviour and kinetic parameters, viz. the order of reaction, energy of activation and preexponential factor. Adhesive properties such as lap shear strength and peel strength at room temperature and elevated temperature were evaluated and are discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 343-349 
    ISSN: 1572-8943
    Keywords: double melting peak ; DSC ; fiber ; polyethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The multiple melting peaks observed on differential scanning calorimetry (DSC) of ultrahigh molar-mass polyethylene fibers (UHMMPE) are analyzed as a function of sample mass. Using modern DSC capable of recognizing single fibers of microgram size, it is shown that the multiple peaks are in part or completely due to sample packing. Loosely packed fibers fill the entire volume of the pan with rather large thermal resistance to heat flow. On melting, the fibers contract and flow to collect ultimately at the bottom of the pan. This process seems to be able to cause an artifact of multistage melting dependent on the properties of the fibers. A method is proposed to greatly reduce, or even eliminate, errors of this type. The crucial elements of the analysis of melting behavior and melting temperature are decreasing the sample size and packing the individual fibers in a proper geometry, or to introduce inert media to enhance heat transport.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 399-405 
    ISSN: 1572-8943
    Keywords: DSC ; polyimide fiber ; TMA ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A commercially available polyimide fiber was investigated as a possible precursor for the formation of carbon fibers. The thermal response of the fiber was thoroughly investigated using DSC, TMA and TG. These responses were dependent on the atmosphere and tension during scanning. The fiber was stabilized at high temperatures both in inert and oxidative environments and the effect of these stabilization treatments on the structure and properties of the fiber was carefully followed. During heating, the fiber showed shrinkage tendency at small tensions, but at higher tensions the fibers could be stretched. Among the two environments investigated, air was more effective than nitrogen in getting a more stable fiber.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 407-415 
    ISSN: 1572-8943
    Keywords: compatibility ; covulcanization ; derivative heat flow (δW/δT) ; DSC ; microheterogeneous
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Derivative heat flow curves give much more information about the phase heterogeneity of binary blends composed of NR, SBR and BR elastomers thanT g. In blend compositions, the areas under the derivative heat flow curves appear to be an additive function of the concentration of elastomers in the case of incompatible blends (NR/BR, NR/SBR). They are less than additive for either a partially compatible blend (uncured SBR/BR) or a compatible blend (covulcanized SBR/BR). In the case of 60/40 SBR/BR blends, a DSC (T 0.5) reveals a singleT g, in conformity with the earlier investigators, whereas the derivative heat flow curve shows two peaks (T p) indicating incomplete homogenization of the phases. This is a new observation not mentioned in the published literature. Thus, derivative heat flow traces are likely to provide a unique tool to determine compatibility of elastomers. The study also reveals the importance of sample contact with the DSC pan in quantitative determinations.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 449-454 
    ISSN: 1572-8943
    Keywords: DSC ; network ; polyethylene ; turbidimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Semicrystalline polymers are made of a crystalline phase and of an amorphous phase. Recently, NMR, Raman and FTIR experiments have identified a third phase comprised of defects such as tie-molecules, in the organization of chains. Our investigation of physical gels has led us to believe that by following the heat flow in a very slow temperature ramp (0.05 K min−1), phasechanges, unnoticed in the usual fast ramp, could be detected. These are associated to a physical network strained in the temperature ramp. In order to obtain more information on the network phase, the polymer has been crosslinked The characteristics obtained by slow calorimetry and turbidimetry of the original and modified materials are compared.
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