Browsing by Author "Herzog M."

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Item
    An investigation on the possibility of fiberglass manufacture using a matrix obtained from water diluted mixtures of unsaturated lyester and polyurethane resins
    (2017-01-01) Matev A.; Velev P.; Herzog M.
    Four types of matrices obtained from a mixture of unsaturated polyester resins diluted by water and a waterdispersible polyurethane-acrylate oligomer ((Bayhydrol® UV 2317) of different percentage (20 %, 40 %, 60 %, 80 %) are used for production of glass reinforced composites. Then composites are obtained from the matrices mentioned above and glass fabric of a weight of 81g/m2 and 163 g/m2. The physical properties of the composites prepared are investigated by ATR- FTIR. Some mechanical properties, such as tensile strength, elongation at break and thermal properties of the composites are measured. Specific matrices are selected as they are suitable for composites preparation. The latter can be used for fiberglass production. Future study is required aiming to decrease the styrene emissions during lamination and curing.
  • No Thumbnail Available
    Item
    Methylcellulose/SiO2 hybrids: Sol-gel preparation and characterization by XRD, FTIR and AFM
    (2011-03-21) Rangelova N.; Radev L.; Nenkova S.; Salvado I.M.M.; Fernandes M.H.V.; Herzog M.
    Methylcellulose (MC)/SiO2 organic/inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO2. AFM depicts surface roughness which depends on the silica precursor and MC content. © Versita Sp. z o.o.
  • No Thumbnail Available
    Item
    Nanoscale particle reinforcement by oligourea particles in polyurethanes - A concept to control mechanical properties
    (2014-01-01) Peshkov V.; Herzog M.; Behrendt G.
    We report on a concept to obtain high properties of nanocomposites by incorporating into the polymer matrix nanoscale reactive species to reinforce the structures already at low concentrations. The materials used to study the effect of reactive organic nanofillers on properties of organic-organic nanocomposites were poly(urethane ureas) in which the urethane part consisted of long chain polyether alcohols reacted with 4,4'-diphenylmethane diisocyanate (MDI) and the urea part of oligourea particles produced either by solvolysis of flexible polyurethane foams or by a new method in which a isocyanate prepolymer is reacted with appropriate reagents with simultaneous cleavage of the pre-formed urethane bond. The combination of two polymer networks-a urethane and a urea one-result in extraordinary synergy in mechanical properties. The properties can indeed be tailored by changing the volume fraction, shape, and size of the filler particle.
  • No Thumbnail Available
    Item
    Polycarbonate diols to produce elastic polyurethane foams - A method of immobilization of carbon dioxide into a polymer structure
    (2017-01-01) Dimitrov K.; Todorova D.; Nenkova S.; Herzog M.
    Using carbon dioxide as feedstock for polymers is a big challenge and a chance for our sustainable future. It has an immense potential for the coming decade, which comes much faster than expected. Scientists are very active lately in carbon dioxide chemistry research, especially in the field of carbon dioxide based chemicals and polymers. We report here on the stability of higher molecular weight polycarbonate diols and the formation of specialty polyurethanes such as UV stable elastomers, semi-rigid foams, and elastic sealants. These polyurethanes are produced from polycarbonate diols (ETERNACOLL®) and aromatic 4,4'-diphenyl-methane diisocyanate, from aliphatic hexane-1,6-diisocyanate, or the trimer, diisocyanates. We use butane-1,4-diol or pentane-1,5-diol as a chain extender. The thermal and mechanical properties of the polyurethanes obtained are determined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The data obtained show no phase segregation or any type of crystallinity. Any possible changes in the molecular mass distribution of the samples are investigated with the application of gel permeation chromatography (GPC). It is evidenced that only heat treatment brings about molecular mass distribution shifts to lower values.
  • No Thumbnail Available
    Item
    Shape memory polyurethanes based on recycled polyvinyl butyral II. mechanical and shape memory properties
    (2014-01-01) Tsonev T.; Nenkova S.; Herzog M.
    Shape memory polyurethanes (SMPUs) based on recycled polyvinyl butyral and 4,4'-diphenylmethane diisocyanate, hexane-1,6-diol, and polypropylene glycol of varying hard segment content were investigated. Their mechanical properties and shape memory effect in particular were examined defining the amorphous soft segment domain as a reversible phase, while the crystalline hard segment domain as a frozen phase. Effects of hard segment content (30-45 %) and maximum strain on the cyclic tensile and mechanical properties below (25°C) and above (70°C) material glass transition temperatures were studied. The properties reversibility observed on repeated deformation was improved by decrease of the deformation magnitude and the increase of the hard segment content.
  • No Thumbnail Available
    Item
    Shape memory polyurethanes based on recycled polyvinyl butyral. I. Synthesis and morphology
    (2013-10-17) Tsonev T.; Herzog M.; Nenkova S.
    Shape memory polyurethanes (SMPUs) were synthesized by 4,4′- diphenylmethane diisocyanate (MDI), hexane-1,6-diol (HD), polypropylene glycol (PPG), and recycled polyvinyl butyral (PVB). Dynamic mechanical analysis, differential scanning calorimetry and Fourier transformation infrared attenuated total reflection spectroscopy was used to characterize the poly (vinylbutyral-urethanes). Micro-phase domain separation of hard and soft segments and phase inversion were investigated. Increasing the hard segment content, i.e., average hard segment molecular weight, leads to an increase in the degree of micro-phase separation, hard domain order and crystallinity. The crystalline hard segment structures combined with the elastic nature of soft segment matrix provide enough physical and chemical crosslinks to have shape memory effect. © 2013 Versita Warsaw and Springer-Verlag Wien.