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Author: Walenta, E. ×

Publications Search Results

Now showing 1 - 8 of 8
  • Patent
    Verfahren zur Herstellung von Cellulosefasern und die mit diesem Verfahren hergestellten Fasern
    ( 2005)
    Fink, H.P.
    ;
    Weigel, P.
    ;
    Walenta, E.
    ;
    Remde, H.
    ;
    Frigge, K.
    Production of flexible cellulose fibres involves spinning cellulose solutions through spinnerets through an air gap into an aqueous and/or alcoholic coagulation bath containing amine oxide and then drying. The novelty is that, before drying, the moist spun fibre is passed through after-treatment bath(s) containing water and water-miscible alcohol(s), diol(s) and/or triol(s) and washing bath(s) containing water, an alkanol, a diol or a triol. Also claimed are cellulose fibres made by this method, which have an initial modulus < 1500 cN/tex. Preferably the after-treatment bath is alkaline and especially consists of a mixture of alkanol and aqueous sodium hydroxide (NaOH) solution, more especially ethanol (EtOH) and 1-30% aqueous NaOH solution. The washing bath contains EtOH. ADVANTAGE - The orientation, modulus, brittleness and tendency of the fibres to fibrillate are all reduced compared with the usual fibres spun from solutions in amine oxides, especially N-methylmorpholine N-oxide (NM MNO), or aqueous NMMNO.
  • Publication
    Structure-property relationships in extruded starch. 1 supermolecular structure of pea amylose and extruded pea amylose
    ( 2001)
    Walenta, E.
    ;
    Fink, H.P.
    ;
    Weigel, P.
    ;
    Ganster, J.
    Separated amyloses with different molecular weight distributions were obtained enzymatically from wrinkled pea starch and processed in a multi-zone twin-screw extruder. The crystalline polymorphs, crystallinity and crystallite dimensions of amylose (unbranched molecular starch component) and films extruded from it were investigated by wide-angle X-ray scattering. The starting amylose materials exhibit a crystalline V-A structure with rather large crystallites (9-25 nm) and a degree of crystallinity ranging from 30 and 40%, depending on the history of the amylose sample. The extruded films, on the other hand, recrystallized in the B-type with a slightly higher degree of crystallinity and significantly smaller crystallite dimensions (3-7 nm). In one case, V-H-type crystals were observed. The mechanical properties of the extruded materials were determined in tensile tests. The amylose with the highest molar mass produces films with the highest mechanical performance. As compared with cellulose or synthetic polymer films, the mechanical properties of the amylose films appear to be fundamentally limited by the lack of preferred molecular orientation.
  • Publication
    Structure-property relationships of extruded starch. 2 Extrusion products from native starch
    ( 2001)
    Walenta, E.
    ;
    Fink, H.P.
    ;
    Weigel, P.
    ;
    Ganster, J.
    ;
    Schaaf, E.
    The supermolecular structure and morphology of extruded flat films from several native starch materials of A an B crystal type were investigated by wide-angle X-ray scattering and scanning electron microcopy. The degree of crystallinity and crystallite dimensions of both the different starting materials and the extruded films were determined and a scheme of the lattice transformations resulting from extrusion was established. The conditions of structure formation of the extruded starch films were varied in relation to plasticizer composition and extruder zone temperatures. The mechanical properties and biodegradability of the films were also measured. The extruded starches crystallized in the V-H polymorph with crystallinities between 33 and 41% and crystallite sizes of up to 35 nm. An increase in crystallite size was found for all starches (sometimes a doubling) with increasing extruder middle zone temperatures from 120 up to 210 degreesC. For extruded potato and maize starches a steep rise in strength and modulus and a drop in elongation was observed about 190 degreesC. Purified amylopectin from maize showed after extrusion the crystalline A-type and small amounts of B polymorph with small crystallites (up to 3 nm) and the best mechanical performance with strengths and moduli of about 20 MPa and 1500 MPa, respectively, for the present extrusion conditions. Native starch films that include 20 to 30% plasticizer biodegrade rapidly in 25 d consuming 90% of the oxygen needed for complete degradation, as analyzed by the Sapromat test.
  • Publication
  • Publication
    Wide angle X-ray and solid state 13C-NMR studies of cellulose alkalization
    ( 1995)
    Fink, H.P.
    ;
    Walenta, E.
    ;
    Kunze, J.
    ;
    Mann, G.
  • Publication
    Untersuchungen zur Fadenbildung aus Cellulose-NMMNO-Lösungen
    ( 1994)
    Remde, H.
    ;
    Walenta, E.
    ;
    Weigel, P.
    ;
    Fink, H.P.
    ;
    Zachmann, H.G.