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Polymerization of Lactides in the Melt
Horkel, Ondřej ; Tomala, Libor (referee) ; Petrůj, Jaroslav (advisor)
This bachelor thesis deals with the problematics of Lactide polymerization in the melt. Theoretical part summarizes properties of lactic acid, lactides and polylactides as well as currently used methods of their preparation. In experimental part, a set of three experiments was designed, namely dependance of viscosity average molecular weight on catalyst concentration, polymerisation temperature and polymerisation time. This was achieved by measuring cinematic viscosity using Ubbelohde viscosimeter. As a result of these experiments, it was found that one of posssible combinations of conditions resulting in high molecular weight polymers is the following: concentration ratio of catalyst towards lactide 110–4, polymerisation teperature 160 °C and polymerisation time 3 hours.
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Crystallization of binary polylactide blends and their morphology
Debnáriková, Michaela ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
Master thesis deals with the influence of polyvinylacetate, polycaprolactone, poly(butylene-adipate-co-terephtalate) and talc, ethylenevinylacetate, polyethylene glycol and monosodium citrate on the flow properties, mechanical properties and crystallization ability of PLA. The flow properties were studied using the melt flow index and mechanical properties were studied using a tensile test. The crystallinity was studied by differential scanning calorimetry and on a polarization optical microscope equipped with hot stage. Isothermal crystallization was performed at 95 and 105 °C for 3 h and non-isothermal crystallization was performed with a calorimeter at two cooling rates (1 and 10 °C/min). Upon the isothermal crystallization at 95 °C, the formation of denser crystalline structure was observed and the content of crystalline phase increased in most of the samples. The formation of spherulitic structure was observed at 105 °C in samples with 30 % PVAc, 30 % EVA and PEG. Reducing the cooling rate to 1 °C/min at non-isothermal crystallization had nearly no effect on the crystallization process of the most samples; the content of crystalline phase increased in the samples containing PBAT and PEG, which revealed double melting peak during subsequent heating. The crystalline fraction was the most significantly affected by the addition of PEG. All added polymers except PVAc affected the mechanical properties; PBAT, PCL, EVA and PEG increased the strain and decreased the strength and modulus of elasticity. The samples containing monosodium citrate showed unsatisfactory mechanical properties and could not be measured. The samples containing higher concentration of EVA copolymer showed the phase separation.
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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.
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Determination of Hydroxyacids including their Low- and High Molecular Derivatives
Lysáková, Klára ; Mravcová, Ludmila (referee) ; Čáslavský, Josef (advisor)
This bachelor thesis deals with the determination of hydroxy acids and their low and high molecular polymers. The theoretical part deals with their properties, production and utilization. The polymers of these substances are used as biodegradable plastics and as absorbable sewing materials. The experimental part is focused on the determination of the total component and on the composition and amount of impurities of selected samples of ethyl lactate, lactides and polylactide. Analysis was performed by gas chromatography (GC) and tandem techniques using GC/MS and Head-Space-GC/MS analysis.
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PLA Synthesis in Solution
Svítil, Jan ; Zdeněk, Přikryl (referee) ; Petrůj, Jaroslav (advisor)
This thesis is studying PLA syntheses using polymerization of lactides in solution. Theoretical part deals with properties and production of lactic acid, lactides and polylactides. In the experimental part, possibilities of lactides polymerization in solution has been summerised and verified. Syntheses were performed via “solvothermal” method using 7 solvents (toluene, chloroforme, 1,2-chlorobenzene, acetone, tetrahydrofurane, cyclohexane and hexane). Using hexane as solvent, at concentration ratio catalyzer/lactide 1 : 1 000, polymerization temperature 160 °C and reaction time 20 h, polylactide of viscosity average molecular weight 179 000 gmol–1 was synthetized from the lactide.
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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.
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Functionalization of polyolefins by grafting
Paulenka, Igor ; Petruš, Josef (referee) ; Petrůj, Jaroslav (advisor)
The theoretical part of the diploma thesis is focused on the funcionalization of polyolefins in order to accelerate their degradation and to increase their carbon content from renewable resources with focus on hydroxyacids. The experimental part is focused on preparing samples and studying the properties of the polypropylene and polyethylene blends with the polylactide with different contents of the initiator and the maleic anhydride. Samples were evaluated by determining the degree of conversion maleic anhydride, differential scanning calorimetry, infrared spectroscopy, melt flow index and mechanical properties.
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Mineralised polylactide and polycaprolactone soft foams with hierarchical micro-macro porous structure for tissue engineering
Beran, M. ; Berková, E. ; Musílková, Jana ; Sedlář, Antonín ; Slepička, P. ; Fajstavr, D.
The purpose of the study was development of soft foams from resorbable polymers with unique micro-macro porous interconnected hierarchical structure specially designed as scaffold for engineering of soft tissues. The foams have been prepared by freeze-drying of solutions of polylactide (PLA) and polycaprolactone (PCL) in 1,4-dioxane. The foams prepared by freeze-drying had interconnected porous aerogel characteristics. The hierarchical structure with bimodal micro-macro pore size distribution were obtained after addition of sucrose or NaCl porogens with defined crystal size distributions to the solutions before freeze-drying and leaching the porogen crystals from the freeze-dried foams with demineralised water. Polyethyleneimine was chemically conjugated to the alkali-treated foams followed by conjugation of citric acid using carbodiimide chemistry. Finally, they were mineralised by immersing and incubating in a simulated body fluid with ionic concentration similar to that of human blood plasma, to obtain tissue engineering scaffolds. To verify their biocompatibility, the scaffolds were seeded with adipose-derived stem cells (ASC) and sarcoma osteogenic-2 (SaOs-2) human osteoblast-like cells. Morphology of the cells attached to the scaffolds was evaluated and their viability was verified by a metabolic test. Biocompatibility and usability of the scaffolds was successfully verified by incubation with adipose-derived stem cells and SaOs-2 human osteosarcoma cell line. Mineralised scaffolds are more suitable growth supports for both the cell types than unmineralized collagen scaffolds. The scaffolds have been specially designed for engineering of soft tissues, but they can be used in other categories of tissue engineering, too.
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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.
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Crystallization of binary polylactide blends and their morphology
Debnáriková, Michaela ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
Master thesis deals with the influence of polyvinylacetate, polycaprolactone, poly(butylene-adipate-co-terephtalate) and talc, ethylenevinylacetate, polyethylene glycol and monosodium citrate on the flow properties, mechanical properties and crystallization ability of PLA. The flow properties were studied using the melt flow index and mechanical properties were studied using a tensile test. The crystallinity was studied by differential scanning calorimetry and on a polarization optical microscope equipped with hot stage. Isothermal crystallization was performed at 95 and 105 °C for 3 h and non-isothermal crystallization was performed with a calorimeter at two cooling rates (1 and 10 °C/min). Upon the isothermal crystallization at 95 °C, the formation of denser crystalline structure was observed and the content of crystalline phase increased in most of the samples. The formation of spherulitic structure was observed at 105 °C in samples with 30 % PVAc, 30 % EVA and PEG. Reducing the cooling rate to 1 °C/min at non-isothermal crystallization had nearly no effect on the crystallization process of the most samples; the content of crystalline phase increased in the samples containing PBAT and PEG, which revealed double melting peak during subsequent heating. The crystalline fraction was the most significantly affected by the addition of PEG. All added polymers except PVAc affected the mechanical properties; PBAT, PCL, EVA and PEG increased the strain and decreased the strength and modulus of elasticity. The samples containing monosodium citrate showed unsatisfactory mechanical properties and could not be measured. The samples containing higher concentration of EVA copolymer showed the phase separation.
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