National Repository of Grey Literature 37 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Functional foams with densit ygradient
Svatík, Juraj ; Figalla, Silvestr (referee) ; Jančář, Josef (advisor)
Vycházíme-li z lehčených přírodních materiálů, lze od porézních materiálů s gradientem porozity očekávat mechanické vlastnosti nadřazené konvenčím polymerním pěnám, a to díky jejich specifické architektuře. Tyto vlastnosti umožňují použití lehčených materiálů jako strukturních prvků. V této práci je popsaná příprava gradientních porézních materiálů pomocí laminování a/nebo 3D tisku. Provedeny byly statické a dynamické mechanické testy na obou kvazi homogenních a gradientně porézních pěnách poskytující experimentální podklad pro hypotézu deformační odezvy plynoucí ze strukturní architektury. Data se interpretovala užitím zavedených teoretických modelů. Naše výsledky vedly k závěru, že tyto teoretické modely odvozené od pěn s pravidelnou strukturou není vhodné aplikovat pro pěny s gradientem porozity, protože prokazují podstatně lepší mechanické vlastnosti než homogenně porézní pěny.
Preparation and characterization of unsaturated bio-polyester resins
Žůrek, Michal ; Petrůj, Jaroslav (referee) ; Figalla, Silvestr (advisor)
The theoretical part of this work is devoted to the selection of suitable components for synthesis of a branched oligoester and their structural arrangement. Further, oligomers of lactic acid esterified with crotonic acid branched by erythritol or pentaerythritol are discussed. Crosslinking of prepared oligoesters is accomplished by free radical mechanism using vinyl acetate as reactive diluent and 2,2'-azo-bis-isobutyronitrile as initiator. Resin was cured by vinyl acetate in different mass ratios. Results show that there in an optimal ratio for curing between oligoester and reactive diluent. Using less vinyl acetate results in insufficient crosslink density or, on the contrary, using considerable excess of vinyl acetate causes rapid polymerization, that also results in lower density of crosslinking. The crosslink density was determined indirectly by extraction of the soluble part to acetone after curing and drying of the product.
Preparation of Poly(3-hydroxybutyrate) based acrylic monomer
Liška, Marek ; Přikryl, Radek (referee) ; Figalla, Silvestr (advisor)
The main aim of this thesis is to research and prepare acrylic (methacrylic) monomers derived from poly(3-hydroxybutyrate). The monomers were prepared in two-step syntheses. In the first step P3HB was depolymerised with selected alcohols and afterwards, products of those syntheses were used as substrate and mixed with polymethylmethacrylate to produce their methacrylic derivates. The selected alcohols for the alcoholysis were ethanol and ethylene glycol. In total, four substances were prepared. Products of alcoholysis were ethyl-3- hydroxybutyrate, 2-hydroxyethyl-3-hydroxybutyrate and their methacrylic derivates. Significant part of this thesis is aimed towards the analysis of prepared substances and the analysis of reactions. In the process, titrations and instrumental methods, such as gel permeation chromatography (GPC), infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetry (TGA) and differential scanning calorimetry (DSC) were used. This work describes preparation and analysis of polymers prepared from methacrylates from the mentioned syntheses. Cross-linked polymers, because of their low glass-transition temperature are elastomers.
Study of poly(lactic acid) foams preparation
Svatík, Juraj ; Petrůj, Jaroslav (referee) ; Figalla, Silvestr (advisor)
The bachelor thesis focuses on the processing of expanded poly(lactic acid) (PLA) or polylactide and on studying of some of its properties. The theoretical part deals with several ways of processing of PLA, its properties and methods of degradation. Furthermore, this part focuses on various processing methods of expanded PLA and the phenomena affecting the expansion, such as dissolving of gases in PLA. At the end of this part, it focuses on strength properties of PLA foams. The experimental part deals with specific way of processing of expanded PLA; that is dissolving of the physical blowing agent in PLA and subsequent foaming. Specific conditions within the processing of PLA foams are investigated there, such as pressure of gas needed, size of PLA particles. Further, this part focuses on distinct types of PLA foams differing in density or processing temperature. Last, it focuses on strength characteristics of PLA foams depending on their density and processing temperature.
Bio-based composites made from lactic acid resins
Smiřický, Jan ; Černý, Miroslav (referee) ; Figalla, Silvestr (advisor)
This bachelor thesis is about the synthesis of polyurethane glue, which is capable of gluing together sawdust, and about the testing of the mechanical characteristics of the glue and sawdust compostion. This glue is biodegradable and is created from renewable resources, this is why it could be an appropriate replacement for phenol formaldehyde, melamine, and urea formaldehyde resins. Another indisputable advantage is the absence of arenes in the macromolecule structure, which can be carcinogenic. In this synthesis, the compounds polylactic acid and hexamethylene diisocyanate were chosen, the former as the polyol and the latter as the isocyanate. In the theoretical section of the thesis, the used compounds are described in terms of their characteristics, their creation and the tests of the composites as well. In the experimental section, the conducted experiments are described.
Functionalization of Polyethylene by Grafting
Hofmann, Jan ; Figalla, Silvestr (referee) ; Petrůj, Jaroslav (advisor)
The bachelor thesis deals with functionalization of polyethylene by grafting. The theoretical part summarizes informations about types of copolymers, free radical grafting techniques and the factors, that affect properties of modified polymers as well as their biodegradability. The experimental part deals with modification of polyethylene in kneader under various conditions. The blends are composed of polyethylene, polylactic acid and another aditives (initiator, stabilizers). The torque and the temperature were monitored during the kneading. Some mechanical properties of new materials were tested on Zwick Z010 apparatus. Rheological properties of samples were investigated with melt flow indexes.
Polylactide chemical recycling to Lactide
Kučerová, Eliška ; Pospíšilová, Aneta (referee) ; Figalla, Silvestr (advisor)
This diploma thesis deals with chemical recyclation polylactide to lactide. In the theory is summarized actual state of knowledge about chemical recyclation of polylactides, their properties, preparations a possibilities of characterization. Experimental part of work verify ethanolysis of PLA withthe samples of granulate, waste filaments and textiles. In the experimental work is suggested an optimalization of alcoholysis to direct yield of oligomer suitable for depolymerization to lactide. This method was verified for 5 different samples of PLA, which 4 of them was made of waste PLA. The time needed for depolymerization was evaluated and the effect of catalysis. Lactide and PLA recyclates was further analyzed by NMR, FTIR, DSC and GPC.
The study of using lactic acid esters for preparing lactides and PLA
Vida, Mikuláš ; Figalla, Silvestr (referee) ; Petrůj, Jaroslav (advisor)
This diploma thesis deals with use of lactic acid esters for preparation of lactides and PLA. In the theoretical part, it has been processed literature review focus on manufacturing technologies and properties of lactic acid and its esters (especially ethyl ester and lactides). In the experimental part, it has been designed and realized functional laboratory apparatus for preparation of cyclic dimer of lactic acid – lactides. On this apparatus, there were carried out principal laboratory experiments leading to optimization of lactides yields using various catalysts.
New Processes of Lactid Acid Polymers Preparation
Figalla, Silvestr ; Svěrák, Tomáš (referee) ; Herink,, Tomáš (referee) ; Petrůj, Jaroslav (advisor)
The work focuses on new processes for the preparation of lactic acid derivatives. The main objective was to verify the feasibility of preparing high molecular weight polylactide using ethyl lactate as a precursor of lactide synthesis. Part of the work is devoted to the new ethyl lactate synthesis method. The experimental part of the thesis is divided into partial key steps on the way from the lactic acid to the high molecular polylactide. The preparation of anhydrous ethyl ester of lactic acid (EtLA) was solved in an innovative way using alcoholysis of the oligomeric lactic acid. A kinetic model for isothermal alcoholysis and equimolar reactants ratio was derived from this method. The ethyl lactate was oligomerized by transesterification into the low and high molecular weight oligomer with the help of newly found catalysts suitable for the reaction medium. Stannous lactate was used as catalyst for oligomerization of the low molecular weight polymer suitable for the preparation of lactide (Mn 1000 g.mol-1). Experimental polymerization of ethyl lactate into high molecular weight product in tens of kDa has been investigated with newly synthesized tetraethyllactoyl titanate, Ti(EtLA)4. The laboratory method was derived for the depolymerization of the oligomer into lactide. Optimal conditions found for lactidation are as follow: temperature 225 ° C, pressure 2 kPa, catalysis 0,05 mol% of stannous lactate (with respect to oligomer lactate units). The prepared lactide was refined to polymer grade purity by distillation and subsequent recrystallization from ethyl acetate and toluene. The method for the preparation of high molecular weight PLA through ROP polymerization of lactide has been optimized. By optimization, suitable catalyst concentration was found in combination with the polymerization temperature and the polymerization length. An equimolar mixture of Tin 2-ethylhexanoate and 1-decanol was used as the catalytic system. The optimal ROP conditions for achieving the maximum molecular weight and suppressed polymer coloration (yellowing) are: catalyst concentration 0,01 mol%, temperature 160 °C, and polymerization length 4 hours. PLA with molecular weight Mw= 447 ± 7,8 kg.mol-1 was prepared at these conditions and good repeatability of the result was achieved. The effect of naturally occurring lactide contaminants and their influence on the course and ROP result was experimentally verified on the optimized polymerization system. The purpose was to explore the effect of lactide contamination with water and ethanol as natural lactide contaminants. The results clearly confirm the orderly lower sensitivity of the polymerization system for the presence of ethanol as compared to water contamination. In the case of the presence of water, the course and the result of the polymerization in terms of both the conversion and achieved molecular weights are negatively affected, even when the water content is in the order of 0,001%. Conversely, the presence of ethanol has a positive effect on lactide conversion and polymer polydispersity. Lactides with an alcohol content of about one-tenth of a percent are suitable to reach molecular weights of PLA similar to commercially available products. This difference shoves a significant advantage in the proposed technology of preparing PLA from ethyl lactate, especially for easier purification of crude lactide into polymer grade purity.
EPDM addition influence on SBR/NR mixtures ozone resistance
Hofmann, Jan ; Figalla, Silvestr (referee) ; Petrůj, Jaroslav (advisor)
The diploma thesis deals with the EPDM addition influence on ozone resistance of NR/SBR mixtures. The theoretical part summarizes knowledge about rubber processing, additivation and effects of ozone on vulcanized rubber. The experimental part aims on preparation of rubber blends and measurement of its mechanical, physical and rheological properties in dependance on their composition.

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