Technology

  2010 MAR 23 - (VerticalNews.com) -- "Dynamic mechanical studies of Molecular dynamics have been performed for two ethylene-norbornene copolymers. The analysis of data indicates the existence of three relaxation processes: a primary (alpha) and two secondary (beta and gamma) ones," scientists writing in the journal Polymer report.

  "It was found that the secondary processes beta and gamma are connected with the local motions of ethylene and norbornene groups, respectively and that their rates follow the Arrhenius relation. Moreover, the beta process was recognized as the Johari-Goldstein process acting as the precursor of the cooperative structural alpha-relaxation. Contrary to gamma and beta processes, the motional rate of alpha-one follows the Vogel-Fulcher-Tammann equation indicating the cooperative nature of motions involved in this process. An increase in norbornene content in copolymer slows down the molecular dynamics of both norbornene fragments and whole chains, and in consequence shifts these relaxation Processes into higher temperatures," wrote M. Makrockarydzyk and colleagues, Adam Mickiewicz University ...read more

  2010 MAR 23 - (VerticalNews.com) -- "Well architectured polyurethanes containing fluorine are expected to be applied in medical devices as well as other fields. A telechelic polyurethane end-capped with perfluoropolyether segments was prepared from polyether glycol as a soft segment, 4, 4'-methylene-bis-(phenylisocyanate), and mono-functional perfluorinated oligomer," scientists in Beijing, People's Republic of China report.

  "The telechelic polyurethane was studied by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TCA), X-ray photoelectron spectroscopy (XPS), contact angle and atomic force microscopy (AFM). XPS results indicated that the surface of the fluorine containing polyurethane was enriched with fluorine component. It exhibited a hydrophobic property with a water contact angle of 113 degrees. The polyurethane terminated with perfluoropolyether segments showed a better thermal stability. A mechanism was proposed to explain thermal decomposition of polyurethanes," wrote Q.Z. Zhu and colleagues ...read more

  2010 MAR 23 - (VerticalNews.com) -- "A novel triptycene type diacrylate cross-linker, triptycene hydroquinone diacrylate (THDA) was synthesized from the reaction of triptycene hydroquinone with acryloyl chloride and characterized. The photocuring behaviour and the reaction kinetics of the synthesized cross-linker were investigated by means of photo-differential scanning calorimetry (photo-DSC) experiments," investigators in Istanbul, Turkey report ...read more