National Repository of Grey Literature 52 records found  beginprevious36 - 45next  jump to record: Search took 0.01 seconds. 
Vinyl prepolymers - methods of preparation and application
Černý, Miroslav ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
The theoretical part of this thesis is focused on bulk radical polymerization of styrene, methylmethacrylate, vinyltoluene and paramethylstyrene. It summarizes actual informations about kinetics and performance possibilities of bulk polymerization. Experimental part deals with polystyrene prepolymers preparation by bulk polymerization. The aim is to find optimal conditions for prepolymers preparation. Prepolymers should be usable for subsequent polymerization nearly up to 100% conversion. Conversion values were gravimetrically determined and molecular weights were obtained by viskosity measurements, which were realized by Ubbelohde viscometer. In the experimental part, there were performed simulations targeted on conversion dependence on time. The purpose was a prediction of monomer conversion at a given time during polymerization. Differences between reality and simulation were low in most of cases and the found form of kinetic behavior calculations provides satisfying results. In the conclusion of this thesis was suggested a new procedure for polystyrene prepolymers preparation.
Reactions of HDPE in the melt initiated by peroxides
Hampapa, Břetislav ; Kučera, František (referee) ; Petrůj, Jaroslav (advisor)
The thesis deals with HDPE modification by crosslinking. In the theoretical part, data available in the literature were reviewed. Modifications of the selected HDPE copolymer grade were carried out in a kneading device Brabender using 25 ml chamber size. After having optimized process conditions, there were performed a series of experiments in dependence on concentration of the initiator. Reological properties of polymer samples were investigated by melt flow indexes measured under different conditions. Changes in crystallinity and melting temperatures were evaluated from DSC heat flow measurements. The samples meeting characteristics supposed were selected for measuring complex viscosity on the Rheometer AR-G2 TA and for testing some mechanical properties on the device Zwick.
Blends of PLA with thermoplastics
Petruš, Josef ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
Diploma thesis deals with preparation of polymer blend of polymer A and polymer B. Knowledge of polymer blends forming, thermodynamics and function of compatibilizer is contained in the theoretical part. Polymer blend A/B of weight ratios 75/25, 50/50 and 25/75 wt% were prepared by physical compatibilization. Concentration of compatibilizer was 5 wt%, in the case of A/B 50/50 wt% concentration of compatibilizer was 10 and 30 wt%, respectively. Blending was achieved with twin-screw extruder at 230 °C and 100 rpm. Second method used for A/B blending was based on reactive compatibilization which was achieved with Brabender kneader at 230 °C, 50 rpm and reaction time 10 minutes. Concentration ratios of A/B were 75/25, 50/50 and 25/75 wt%. Itaconic acid anhydride and maleic anhydride 0.5 and 5 wt% were used as monomer. 2,5-dimethyl-2,5-bis(tert-buthylperoxy)hexan was (Luperox 101) used as an initiator. Difference between compatibilized and noncompatibilized blends was characterized by scanning electron microscopy, tensile test, differential scanning calorimetry, melt flow index measuring, acid-base titration and FT-IR spectroscopy.
Practical approach to bulk polymerization of styrene
Pukančíková, Andrea ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
The diploma thesis deals with radical bulk polymerization of styrene. Recent knowledges about mono- and multifunctional initiators of radical polymerization and coordination polymerization of styrene with metalocene initiators are summarized in theoretical part. Experimental part of diploma thesis is focused on relationship between polymerization conditions and conversion, molecular mass and distribution of molecular mass. Experiments carried out with monofunctional initiators (dibenzoylperoxide, dilauroylperoxide, tert-butylperbenzoate) and with bifunctional initiators (Luperox 101 and Luperox 256). Polymerizations took place at temperatures from 80 to 134 °C, reaction time was from 1 to 24 hours, and pressure was 100 and 500 kPa. Conversion of monomer was determined by gravimetry and infrared spectroscopy. Molecular mass and indexes of polydisperzity were measured by gel permeation chromatography in solutions of polystyrene with tetrahydrofurane at temperature 23 °C.
Radical grafting of PE/PP copolymer
Šido, Jiří ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
Diploma thesis deals with preparation and characterization of block copolymer PP/PE grafted with itaconic anhydride in melt. Experimental part deals with free radical iniciated grafting of polar monomers onto polyolefins and with potencial applications of grafted polyolefins. Samples of PP/PE grafted with itaconic anhydride were prepared under various conditions in the experimental part. 2,5-dimethyl-2,5bis(tert-buthylperoxy)hexane (Luperox 101) was used as radical iniciator. Grafting was performed in Brabender mixer under conditions: temperature 190-230°C, concentration of monomer 0,25-1 weight percent, concentration of iniciator 0,025 – 2 weight percent, screw speed 30 rpm. The influence of certain parameteres: iniciator concentration, monomer concentration and temperature upon conversion of monomer, value of MFI and homopolymerization of monomer extent was of interest. Presence of anhydride bonded to the polymer backbone was confirmed by FTIR spectroscopy. Concentration of grafted anhydride and conversion of monomer was determined by acid-base titration and confirmed by FTIR spectroscopy.
Application of thermochromic compounds in polymeric materials
Slánská, Petra ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
V textilním průmyslu je v dnešní době veliká konkurence. Každá novinka může znamenat velký zisk. Tato diplomová práce se bude zabývat aplikací termochromních přísad (látka reagující na teplotu změnou své barvy) do polymerní matrice, konkrétně polypropylenu, a jeho další zpracování u výrobce technického polotovaru - výroba vláken. Po výrobě vzorků bude provedeno jejich testování. Porovnají se vlastnosti polypropylenu s a bez termochromních přísad a zhodnotí se, nakolik tyto přísady ovlivňují vlastnosti polypropylenu. Ze získaných výsledků se stanoví možnost využití termochromních přísad v textilním průmyslu.
Tha synthesis of syndiotactic polystyrene using monocyclopentadienyl titanium complexes
Svačina, Zdeněk ; Petrůj, Jaroslav (referee) ; Hermanová, Soňa (advisor)
A series of four novel halosilylsubstitued monocyclopentadienyl titanium complexes; [Si(CH3)2FCp]TiCl3 – FSiTTC, [Si(CH3)F2Cp]TiCl3 F2SiTTC, [Si(CH3)Cl2Cp]TiCl3 - Cl2SiTTC, [Si(CH3)2ClCp]TiCl3 - ClSiTTC was tested as catalytic precursors for polymerization of styrene in toluene. The maximum polymerization activity was achieved after polymerization period of 20 minutes. Activity decreased in order FSiTTC/MAO > F2SiTTC/MAO > Cl2SiTTC/MAO > ClSiTTC /MAO. Prepared polystyrenes were characterized using 13C NMR spectroscopy and DSC analysis. Syndiotacticity index of obtained PSs was determined by means of Soxhlet extraction with butan-2-one as solvent. Syndiotacticity indexes of PSs obtained by investigated catalysts possessed higher values then those obtained by standard catalysts (CpTiCl3 a Cp*TiCl3) at comparable polymerization conditions.
Manufacturing of micro-structures by two-photon polymerization
Skalický, Jiří ; Petrůj, Jaroslav (referee) ; Richtera, Lukáš (advisor)
Utilization of focused laser beam for photo-polymerization represents an elegant and fast method how to manufacture microstructures in dimensions from hundreds of nanometres to tens of micrometres. Two-photon photo-polymerization is used with advantage to manufacture microstructures with sub-micrometre details. In this case the laser wavelength is about two times longer comparing to the spectral region of the highest photoresist sensitivity and the two-photon photo-polymerization is initiated only in the positions of sufficient optical intensity. Precise and controlled positioning of the photoresist with respect to the laser focus ensures only illumination of areas of future microstructure and initialization of photo-polymerization here. Fine details of manufactured microstructures depends, except the laser beam focusing, also on the chosen photoresist and quenching of polymerization in non-illuminated areas.
Comparing Physical Properties and Industrial Applications of Some Lactic Acid Esters
Paulenka, Igor ; Omelka, Ladislav (referee) ; Petrůj, Jaroslav (advisor)
The bachelor thesis deals with characterization of lactic acid esters on the basis of their physicochemical properties. Methyl, ethyl, 2-ethylhexyl, n-propyl, isopropyl lactate were selected. These esters are biodegradable and they are therefore considered as replacement for more toxic and dangerous solvents for industrial use. Antoine equation and Hildebrand solubility parameter was calculated from vapour pressure measured by isoteniscope.
Influence of catalysts on polyurethane formation
Chadima, David ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
The bachelor thesis deals with the influence of catalysts on polyurethane formation. The theoretical part includes basic knowledge of polyurethane chemistry complemented by a literature review contains information about catalysis and reaction mechanism of polyurethane formation. In experimental part were studied effects of catalysts N,N,N',N' tetramethylethylenediamine, Stannous octoate, 1,4-Diazabicyclo[2.2.2]octane and Dibutyltin dilaurate at the rate of synthesis of the polyurethane resin. The measurement was based on measuring the time for which the reaction mixture reaches the maximum temperature. Effective concentrations of catalysts use were calculated. By additional measurement was performed simplified calculation of the activation energy for the demonstration of the effect of temperature on the observed reaction.

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2 Petrůj, Jakub
2 Petrůj, Jan
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