Search results for "ANNIHILATION LIFETIME"

showing 3 items of 3 documents

Study of the Curing Process of DGEBA Epoxy Resin Through Structural Investigation

2015

In this work, a multi-scale approach with different analytical methods is applied to study the curing process and the structural properties of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin. This monomer, thermally cured using 4,4′-diaminodiphenilsulfone (DDS) as hardener, is analyzed after 10, 45, 90, and 120 min of reaction time at 180 °C to obtain information on samples with different cross-linking densities. Samples are also characterized after extraction in acetone in order to obtain structural information on the insoluble parts. For this purpose, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), solid-state nuclear magnetic resonance (ss-NMR),…

Bisphenol AMaterials scienceDiglycidyl etherEpoxy resins solid-state nuclear magnetic resonance (ss-NMR) positron annihilation lifetime spectroscopy (PALS)Polymers and PlasticsOrganic ChemistryEpoxyDynamic mechanical analysisCondensed Matter Physicschemistry.chemical_compoundMonomerDifferential scanning calorimetrychemistrySolid-state nuclear magnetic resonancevisual_artPolymer chemistryMaterials Chemistryvisual_art.visual_art_mediumSettore CHIM/07 - Fondamenti Chimici Delle TecnologiePhysical and Theoretical ChemistryThermal analysis
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Positronium as a probe in natural polymers: decomposition in starch

2009

Ortho-positronium (o-Ps) is used as a probe in positron annihilation lifetime spectroscopy (PALS) experiments, to characterise the behaviour of free volumes in natural starch samples, as a function of temperature (T). Up to about 540 K, the o-Ps intensity, I(3), remains constant at 26.2% while its lifetime, tau(3), is found to increase linearly. Both parameters undergo a decrease above this T, due to the onset of decomposition, which results in a shrinking of the sample pellets. The results indicate that the glass transition temperature should be above 501 K. Data from thermal gravimetry analysis (TGA) measurements are well described by supposing a first order process for the survival proba…

GLASS-TRANSITIONAnalytical chemistryGeneral Physics and AstronomyElectrons02 engineering and technologyActivation energy01 natural sciencesPositroniumNuclear magnetic resonance0103 physical sciencesPhysical and Theoretical ChemistrySpectroscopyThermal analysisBiological Products010304 chemical physicsChemistrySpectrum AnalysisTransition temperatureTemperatureStarchFREE-VOLUME021001 nanoscience & nanotechnology[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry[ CHIM.POLY ] Chemical Sciences/PolymersThermogravimetry[CHIM.POLY]Chemical Sciences/PolymersThermogravimetry[ CHIM.THEO ] Chemical Sciences/Theoretical and/or physical chemistryVolume fraction0210 nano-technologyGlass transitionANNIHILATION LIFETIMEPhysical Chemistry Chemical Physics
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Polypropylene/polyhedral oligomeric silsesquioxane nanocomposites – study of free volumes, crystallinity degree and mass flow rate

2016

Nanokompozyty polipropylen/poliedryczne oligomeryczne silseskwioksany (PP/POSS) przygotowano metodą mieszania w stanie stopionym polimeru. Wpływ struktury oraz ilości zastosowanych nanonapełniaczy POSS na objętości swobodne w polipropylenie określono z zastosowaniem spektroskopii czasów życia pozytonów (PALS). Ustalono zależności pomiędzy parametrami PALS: czasem życia o-Ps (τ3) i natężeniem (I3) składowej o-Ps oraz wartościami stopnia krystaliczności (Xc ) i masowego wskaźnika szybkości płynięcia (MFR) badanych materiałów. Obecność nanonapełniaczy POSS wpłynęła na liczbę i rozmiary objętości swobodnych w polimerze, co spowodowało zmianę mikrostruktury osnowy polipropylenowej. Wraz ze zwięk…

poliedryczne oligomeryczne silseskwioksany (POSS)Materials sciencePolymers and PlasticsGeneral Chemical Engineering02 engineering and technology010402 general chemistry01 natural sciencesDegree (temperature)chemistry.chemical_compoundCrystallinitymass flow ratenanocompositesMaterials ChemistryMass flow rateComposite materialnanokompozytyPolypropyleneNanocompositepositron annihilation lifetime spectroscopy (PALS)masowy wskaźnik szybkości płynięciacrystallinity degreestopień krystaliczności021001 nanoscience & nanotechnologySilsesquioxane0104 chemical scienceschemistryspektroskopia czasów życia pozytonów (PALS)polipropylen0210 nano-technologypolypropylenepolyhedral oligomeric silsesquioxanes (POSS)Polimery
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