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Effects of .gamma.-irradiation on rheological properties of ultra-high molecular weight polyethylene melts
Mikešová, Jana; Nevoralová, Martina
2005 - English
Ultra-high molecular weight polyethylene is widely used as material in orthopaedic implants. Melt rheology was used to evaluate the result of simultaneous crosslinking and chain scission process in the polymer, .gamma.-irradiated in the solid state. The predominant mechanism in the process was strongly influenced by irradiation dose and dose-rate. An important result was obtained for the polymer irradiated with the sterilization dose 25 kGy and stored in nitrogen when no significant degradation of the polymer was observed. Klinické problémy pacientů způsobené částicemi ultravysokomolekulárního polyethylenu uvolněnými do organismu z kloubních implantátů, vyvolaly zájem o radiační síťování tohoto polymeru. V polymeru po ozáření dochází jak k síťování tak i degradaci. Převahu jednoho z procesů je možné pozorovat meřením reologických vlastností taveniny polymeru. Testovány byly vlivy různých dávek záření a rychhostí ozařování. Důležitým závěrem práce bylo zjištění, že v polymeru ozářeném sterilizační dávkou 25 kGy a uchovávaném v dusíkové atmosféře nebyla pozorována degradace.
Keywords:
rheology; UHMWPE
Available at various institutes of the ASCR
Effects of .gamma.-irradiation on rheological properties of ultra-high molecular weight polyethylene melts
Ultra-high molecular weight polyethylene is widely used as material in orthopaedic implants. Melt rheology was used to evaluate the result of simultaneous crosslinking and chain scission process in ...
Hydrophilic polymer systems in capillary electrophoretic separations
Guryča, Vilém; Novotný, M. V.; Michálek, Jiří; Pacáková, V.
2005 - English
The present work deals with preparations of polymeric stationary phases/coatings for separations of biologically active compounds such as glycoproteins and glycans. Práce pojednává o přípravě polymerních stacionárních fázích/filmech, které slouží pro kapilárně elektroforetické separace biologicky aktivních sloučenin, jako např. glykoproteinů nebo glykanů.
Keywords:
analytical glycobiology; capillary electrochromatography; hydrophilic acrylamide monoliths
Available at various institutes of the ASCR
Hydrophilic polymer systems in capillary electrophoretic separations
The present work deals with preparations of polymeric stationary phases/coatings for separations of biologically active compounds such as glycoproteins and glycans....
Preparation and characterization of molecularly imprinted monolithic columns
Širc, Jakub; Bosáková, Z.; Michálek, Jiří; Guryča, Vilém
2005 - English
By in situ polymerization prepared molecularly imprinted polymer rods were characterized by porosimetry, scanning electron microscopy and by separation of standard hydrophobic solutes and enantiomer pairs. Byly připraveny monolitické kolony na principu vtištěných polymerů a charakterizovány pomocí rtuťové porozimetrie, skenovací elektronové mikroskopie. Jejich separační vlastnosti byly sledovány na dělení směsi hydrofobních standardů a optických izomerů.
Keywords:
molecular imprinting; in situ polymerization; chiral separation
Available at various institutes of the ASCR
Preparation and characterization of molecularly imprinted monolithic columns
By in situ polymerization prepared molecularly imprinted polymer rods were characterized by porosimetry, scanning electron microscopy and by separation of standard hydrophobic solutes and enantiomer ...
Modification of isotactic polypropylene
Ličko, M.; Jeníková, Z.; Rybníček, J.; Horník, J.; Steidl, J.; Raab, Miroslav
2005 - English
Injection moulded samples of polypropylene were used to study the effect of trigonal .beta.-phase and ethylene propylene rubber on mechanical-physical properties in respect to microstructure. The results were compared with pure isotactic polypropylene, .beta.phase induced by 0.33 weight percent of a nucleation reagent and 20 weight percent of EPM rubber increases the toughness of iPP. A substantial increase in toughness was observed by combining both additives resulting in spherolite refinement and reduction in amorphous content. However, the improvement in toughness was at the expense of the yield strength and modulus of elasticity. Vliv trigonální .beta.-fáze izotaktického polypropylenu na mikrostrukturu a mechanicko-fyzikální vlastnosti byl sledován u zkušebních vzorků připravených technologií vstřikování.
Keywords:
isotactic polypropylene
Available at various institutes of the ASCR
Modification of isotactic polypropylene
Injection moulded samples of polypropylene were used to study the effect of trigonal .beta.-phase and ethylene propylene rubber on mechanical-physical properties in respect to microstructure. The ...
Polypropylene/aspen/liquid polybutadienes composites: Maximization of impact strength, tensile and modulus by statistical experimental design
Kokta, B. V.; Fortelný, Ivan; Kruliš, Zdeněk; Horák, Zdeněk; Michálková, Danuše
2005 - English
A systematic study of the effect of concentration of maleated polypropylene MAPP, dicumyl peroxide DCP, polyisobutadiene isocyanate PBNCO and fiber content on the mechanical properties of ASspen-PP composite was undertaken with the objective to protect or increase the impact strength without losing tensile strength reinforcement. Using STAGRAPHIC Plus, the central composite design it was possible to determine the optimum concentration of additives and to maximiye both the impact as well as tensile properties well above that of pure polypropylene. Systematicky byl studován vliv koncentrace maleovaného polypropylenu, dikumyl peroxidu, polyisobutylen-isokyanátu a obsahu vláken na mechanické vlastnosti kompozitů osika-polypropylen s cílem udržet nebo zvýšit jejich houževnatost bez ztráty ztužení. S použitím STAGRAPHIC Plus – the central composite design bylo možné určit optimální koncentrace aditiv a maximalizovat současně houževnatost a tahové vlastnosti, oboje nad vlastnosti čistého polypropylenu.
Keywords:
polymer composites; polypropylene; cellulose
Available at various institutes of the ASCR
Polypropylene/aspen/liquid polybutadienes composites: Maximization of impact strength, tensile and modulus by statistical experimental design
A systematic study of the effect of concentration of maleated polypropylene MAPP, dicumyl peroxide DCP, polyisobutadiene isocyanate PBNCO and fiber content on the mechanical properties of ASspen-PP ...
Molecular current switch: principles and characterization of the model system
Weiter, M.; Vala, M.; Nešpůrek, Stanislav; Toman, Petr
2005 - English
The kinetics of the reversible photochromic reaction merocyanine - spiropyran, which manifested the annihilation of the dipolar species, was studied using the optical and impedance methods. Kinetika reverzibilní fotochromní reakce merocyanin - spiropyran, která vykazuje anihilaci dipolárních částic, byla studována optickými a impedančními metodami.
Keywords:
photoconductivity; photochromism; charge transport
Available at various institutes of the ASCR
Molecular current switch: principles and characterization of the model system
The kinetics of the reversible photochromic reaction merocyanine - spiropyran, which manifested the annihilation of the dipolar species, was studied using the optical and impedance ...
TEM imaging and SERS spectral probing of one particular single dimer and small aggregate of molecularly-bridged Ag nanoparticles
Vlčková, B.; Moskovits, M.; Pavel, I.; Šišková, K.; Sládková, M.; Šlouf, Miroslav
2005 - English
Temporally fluctuating SERS (Surface-enhanced Raman Scattering) signals originating from a single specific dimer of 4,4'-diaminoazobenzene -bridged and a single specific small aggregate of 4,4''-diaminoterphenyl bridged Ag nanoparticles are reported. Práce prezentuje časově fluktující SERS (povrchově zesílený Ramanův rozptyl) signály vznikající z jediného konkrétního dimeru spojeného 4,4'-diaminobenzenem a jednoho určitého malého agregátu spojeného 4,4''-diaminoterfenylem stříbrných nanočástic.
Keywords:
Ag nanoparticle dimers; small Ag nanoparticle aggregates; SERS signal blinking
Available at various institutes of the ASCR
TEM imaging and SERS spectral probing of one particular single dimer and small aggregate of molecularly-bridged Ag nanoparticles
Temporally fluctuating SERS (Surface-enhanced Raman Scattering) signals originating from a single specific dimer of 4,4'-diaminoazobenzene -bridged and a single specific small aggregate of ...
Switching in molecular systems
Nešpůrek, Stanislav; Wang, Geng; Sworakowski, J.
2004 - English
A general approach to electrical and optical switching based on molecular materials is put forward, namely, switching based on photochromism, redox reactions, photoconductivity and charge carrier trapping. The physical and chemical background on a novel type of a switch, based on charge-dipole interactions, is discussed in details. Obecný přístup k elektrickému a optickému přepínání založeném na fotochromismu a redoxních reakcích fotovodivosti. Fyzikální a chemické základy nového vypínače založené na interakcích náboj, dipol.
Keywords:
poly[3,4-(ethylenedioxy)thiophene]; electrical conductivity; charge carrier transport
Available at various institutes of the ASCR
Switching in molecular systems
A general approach to electrical and optical switching based on molecular materials is put forward, namely, switching based on photochromism, redox reactions, photoconductivity and charge carrier ...
Preparation and characterization of isometric gold nanoparticles with pre-calculated size
Šlouf, Miroslav; Kužel, R.; Matěj, Z.
2004 - English
We prepared and characterized Au particles with different sizes in solution by UV/vis spectroscopy and in solid state by TEM and powder diffraction. Připravili a charakterizovali jsme Au částice s rozdílnou velikostí a to v roztoku UV/VIS spektrometrií a v pevném stavu.
Keywords:
Au nanoparticles; powder X-ray diffraction
Available at various institutes of the ASCR
Preparation and characterization of isometric gold nanoparticles with pre-calculated size
We prepared and characterized Au particles with different sizes in solution by UV/vis spectroscopy and in solid state by TEM and powder diffraction....
Charge carrier photogeneration in polymer nanocomposites
Pfleger, Jiří; Pavlík, Martin; Vohlídal, J.
2004 - English
Polymer nanocomposites seem to be promising systems for solar cell application with polythiophene acting as photosensitizer and charge transport medium. The electrophoretic deposition proved to be suitable method for preparation nanostructured core/shell functional layers. The simplicity, fast operation rate and the possibility of covering surfaces of irregular shape, as well as a good quality of prepared films are the major advantages of the method. Polymerní nanokompozity se zdají být slibnými systémy pro aplikace v solárních článcích, v nichž polythiofen je fotosenzitizátor a nosič náboje. Elektroforetické nanášení se jeví být vhodnou metodou pro přípravu vrstev s nanostrukturou: jádro - obal. Jednoduchost, rychlost a možnost pokrývat povrchy s nepravidelným tvarem a dobrá kvalita připravených filmů představují hlavní výhody použité metody.
Keywords:
nanocomposites; conjugated polymers; photoconductivity
Available at various institutes of the ASCR
Charge carrier photogeneration in polymer nanocomposites
Polymer nanocomposites seem to be promising systems for solar cell application with polythiophene acting as photosensitizer and charge transport medium. The electrophoretic deposition proved to be ...
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