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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986), S. 81-88 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The modelless (ML) and micropore (MP) methods for the pore structure analysis of porous particles have been studied. Concerning the ML method, it has been shown that the Kiselev equation can only be used to describe condensation and evaporation in capillaries, but cannot be used to describe the increase and decrease of the thickness of the adsorption layer. Strictly speaking, therefore, the ML method is not modelless even for the pore core size distribution. A comparison between the ML method and methods using an equivalent pore model is given. The results of using the ML method in conjunction with a certain pore model are little less accurate than those obtained by adopting the equivalent pore model straightaway. The parameters required for the calculation of both the pore core size and the pore size distribution as well as the conversion between these two calculations are given.Concerning the MP method, it has been shown that the three types of v-t curves, the theoretical foundation of the MP method, are not in one to one correspondance to the three kinds of adsorption mechanism. From the viewpoint of accuracy, the MP method has no advantage over the methods which are based on the condensation mechanism, both have their own merits.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 160-165 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dual gas flow chromatographic method is proposed. In this method, two different gas streams are introduced separately, one as the carrier gas and the other as the gas for creating the adsorption equilibrium. The thermodesorbed absorbate is eluted by a pure carrier gas. The complete curve of adsorption isotherm can be determined easily; therefore, both the specific area and the pore size distribution can be obtained at ordinary pressure. In addition, this method can be easily changed into the continuous flow method given by Nelsen and Eggertsen [1]. The relationship among R (rate) - V (volume) - A (area) - α (ratio) in elution chromatography are investigated, and the volume of desorbed gas can be obtained from Vd = KRAd directly with K = (αV)/(RA). The standardization for peak area is simplified and more convenient for the treatment by a microcomputer. Some results of specific surface area and pore size distribution by this method, and their comparison with those from other methods are given altogether, and the coincidence is good.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986), S. 20-25 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Starting from Wheeler's composite theory, which takes both the multilayer adsorption and the capillary condensation into consideration, and assuming the equivalent cylindrical model, we have deduced a strict and relatively simpler formula for the calculation of pore size distribution by solving the integral equation directly. The formula is more convenient for application because of its recursion form. Following the same line of reasoning and using the mean value theorem of definite integrals under different conditions, we have unified the equations of Barrett-Joyner-Halenda, Dubinin, Cranston-Inkley, Dollimore-Heal and Roberts. A table of parameters which is required in the calculation is given. Besides the adsorption of nitrogen, the adsorption with water vapor as the adsorbate is investigated and the corresponding empirical equation of adsorption thickness is given.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 3243-3252 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Stable monolayers of a novel side-chain liquid crystalline polysiloxane (PI) and its monomer (MI), both having low transition temperatures, are formed at the air/water interface at 20°C. In monolayer films mesogens are packed closely and their long axes are titled slightly to the water surface. Monomer molecules are thought to lie flat on the water surface when they are initially spread, and a possible model is presented to describe the conformational changes after compressing. Multilayer formations have been observed during isothermal compression of both the polymer and the monomer. Monomer monolayers cannot be deposited onto hydrophobic substrates, whereas polymer monolayers can be deposited at various surface pressures with Y-type or Z-type. UV-Vis spectra of PI Langmuir-Blodgett films indicate that H-aggregates are formed during film formation. The absorption of Langmuir-Blodgett films and cast films shows a distinct hypsochromic shift compared with that of PI chloroform solution.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 1221-1228 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolymerization of polypropene (PP) with maleic anhydride (MA) was carried out at 120°C in xylene with benzoyl peroxide (BPO) as initiator. The resulting product was identified as poly(propene-co-maleic anhydride) obtained by reaction of the double bond of maleic anhydride with free radicals created on the PP chain. In the next step this copolymer was reacted with functional poly(ε-caprolactone) (PCL) by a co-melting method to give rise to a graft copolymer. The optimum time for the second step was found to be around 6 h (at 120°C). X-ray diffraction measurements and DSC characterization of PP-g-PCL have shown that the melting point of the PP phase in the graft copolymers is lower than that of homopolypropene and that its glass transition temperature increases with increasing of PCL grafts.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0959-8103
    Keywords: hydrolysis ; drug release ; IPN ; gel ; swelling ; 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: This paper describes a novel hydrogel based on crosslinked chitosan with glutaraldehyde interpenetrating polyether polymer network. The gel can hydrolyse in acid at 37°C due to the cleavage of imine bonds within the network. At pH≥7, there is no hydrolysis. The pH-dependent release of cimetidine from the gel was also investigated.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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