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Modification of polymer blends based on polyhydroxybutyrate and their properties
Melčová, Veronika ; Tocháček, Jiří (referee) ; Přikryl, Radek (advisor)
Teoretická část této diplomové práce popisuje vlastnosti a možnosti modifikace poly(3-hydroxybutyrátu) (PHB) a amorfní poly(mléčné kyseliny) (PLA) a jejich směsí. V experimentální části je studována reaktivita Joncrylu, Raschigu a fosfitových činidel trifenylfosfitu, tris(nonylfenyl) fosfitu a difenylisodecylfosfitu s čistým PLA a PHB. Raschig, oligomerní aditivum na bázi polykarbodiimidu, prokázal v množství 2hm. % zvýšení viskozity taveniny obou polymerů, a proto byl použit k přípravě směsí o pěti hmotnostních poměrech PHB/(PHB+PLA). Vzorky s Raschigem a odpovídajícími nereaktivními vzorky byly studovány pomocí reologie, gelové permeační chromatografie a modulované diferenční kompenzační kalorimetrie. Výsledky naznačily reakce Raschigu v PHB/PLA směsích vedoucí k rozvětveným strukturám. Rychlost reakce však není nedostatečná ke kompenzaci poklesu viskozity v důsledku degradace při zpracování. Následně zůstává nezreagované množství Raschigu v matrici. Na základě těchto zjištění se dospělo k závěru, že Raschig se chová spíše jako relativně účinný stabilizátor reologických vlastností, než jako činidlo pro záměrnou modifikaci struktury směsí PHB/PLA. Za účelem studia mechanických vlastností těchto směsí byly ve dvoušnekovém extrudéru připraveny vzorky plastifikovány acetyltributylcitrátem.
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Technology of waste polylactide recyclation for 3D print
Kecíková, Alžbeta ; Tocháček, Jiří (referee) ; Přikryl, Radek (advisor)
This bachelor thesis deals with the recycling of waste polylactide from the production process and its subsequent use in 3D printing. To optimize the recycling process of polylactic acid, it was recycled with the addition of various additives such as poly(3-hydroxybutyrate), talc, limestone and chain extenders Joncryl 4368-CS and Raschig Stabilizer 9000. These materials were also investigated with the addition of the acetyl tributyl citrate plasticizer. Samples of the mixtures were prepared on a twin-screw extruder and subsequently a filament was obtained using a single-screw extruder, which was then used for 3D printing by fused deposition modelling (FDM) technology. Temperature towers were printed to obtain optimal processing temperatures for 3D printing. The effect of the additives on the characteristic temperatures and the degree of crystallinity of the PLA was determined by differential scanning calorimetry. The effect of the processing on the molecular chain of selected samples was observed by gel permeation chromatography. Furthermore, in the experimental part of the bachelor thesis, the influence of additives on mechanical properties such as modulus of elasticity, tensile strength and elongation was investigated. The molecular weight was increased due to the chain extenders. Of the particle fillers for the PLA matrix, talc had better mechanical properties than limestone. The greatest effect of the plasticizer was in a mixture with poly(3-hydroxybutyrate).
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Biocomposites based on polyhydroxybutyrate for 3D printing
Horálek, Matyáš ; Tocháček, Jiří (referee) ; Přikryl, Radek (advisor)
The submitted diploma thesis deals with preparation and characterization of biocomposite based on poly-3-hydroxybutyrate. Biocomposites were fabricated with respect to later use in 3D printing. The methodology for testing different kinds of materials and their suitability for 3D printing as well as evaluation of mechanical and thermal properties was established. The first part of this work was focused on the experiments with print temperature and the material flow rate and its influence on the look of 3D printed object and on the material tendency to warp during 3D printing. The design of the experiment method was used for the analyzing of obtained data. It was proven that the amount of kaolin and tributyl citrate has positive influence in reducing warping. By optimization of the biocomposite recipe it was achieved improvement in tensile modulus of elasticticity, ductility, tensile strength, notched and unnotched toughness.
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The influence of detergents on time to failure of high density polyethylene by full notch creep test performed in corrosive bath
Kotoučková, Simona ; Tocháček, Jiří (referee) ; Bálková, Radka (advisor)
The thesis deals with the study of the influence of concentration and different types of surfactants (Igepal CO-520, Arkopal N110, Igepal CO-890, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, dodecyltrimethylammonium bromide and Dehyton PL) on the environmental stress cracking resistance of high-density polyethylene by means of Full Notch Creep Test. Furthermore, the influence of ligamental stress (3,5; 4,0 a 4,5 MPa), pH of the prepared active environment and type of the water used as a solvent for the surfactants on the time to failure was monitored. An accelerating effect was observed at increased concentration, stress and molecular weight. Faster failure was achieved after exposure to ionic types compared to nonionic. The rate of the notch opening was determined. The brittle and ductile behavior during the process of failure was evaluated by microscopic analysis of the morphology of the fracture surfaces. Based on the pH change after the test, the stability of the active environment was evaluated. Deteriorating quality of surfactant solutions was observed. Raman spectroscopy and Fourier transform infrared spectroscopy were used to detect the surfactant on the surface of the test specimen after the test.
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Properties of fibers based on polyhydroxybutyrate
Štulrajterová, Lujza ; Tocháček, Jiří (referee) ; Přikryl, Radek (advisor)
Táto práca sa zaoberá zvlákňovaním biopolymérov z taveniny. V teoretickej časti sú zhrnuté doterajšie poznatky o zvlákňovaní poly(3-hydroxy butyrátu) (PHB) a poly(mliečnej kyseliny) (PLA). Následne boli zvláknené polymérne zmesi na báze PHB s rôznym zložením, čo umožnilo štúdium vplyvu PLA, zmäkčovadiel a ich množstva na vlastnosti pripravených vlákien. Boli použité tri komerčné zmäkčovadlá (ATBC, PEG, A6) a dva experimentálne syntetizované. Zvláknenie bolo prevedené na troch rôznych zvlákňovacích linkách. Konvenčné zvlákňovacie linky s odťahovými rýchlosťami nad 150 m/min sa preukázali ako nevhodné pre spracovanie našich zmesí. Kvôli nedostatočnej pevnosti taveniny sú potrebné nízke odťahové rýchlosti. Boli pripravené vlákna s dĺžiacim pomerom 6,4; ktoré boli následne analyzované pomocou GPC, MDSC a ťahovej skúšky. Na základe nameraných teplôt skelného prechodu zmäkčovadlá ATBC a PEG vykázali lepšiu schopnosť zmäkčiť skúmané PLA/PHB zmesi. Vlákna obsahujúce A6 vykazovali najvyššiu pevnosť v ťahu (250 MPa) a modul pružnosti (2,7 GPa). Nakoniec bol skúmaný vplyv starnutia, tepla a vriacej vody na mechanické vlastnosti týchto vlákien.
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Morphology of Polyamide 12 and Polyamide 11 formed at overpressure and underpressure
Bělašková, Marie ; Tocháček, Jiří (referee) ; Bálková, Radka (advisor)
In this master thesis it was studied morphology of polyamide 12 (PA12), polyamide 11 (PA11) and their blends in the percent ratios 95/5, 75/25, 50/50, 25/75 and 5/95 formed at pressure 7 MPa in a calorimeter both after continual heating and cooling and after annealing and isothermal crystallization. Neat polyamides and blends were further characterized by thermogravimetric analysis, differential scanning calorimetry at atmospheric pressure, Fourier-transform infrared spectroscopy in attenuated total refection, and X-ray diffraction analysis. The increased pressure improved level of polyamide chains ordering in crystal lamellae. Thermal annealing improved especially ordering of PA12, isothermal crystallization led to considerable increase of crystallinity, whereas PA11-rich blends supported perfection of PA12 crystals. Partial transformation of - to -structure occurred in case of neat PA12 at high pressure, the change of the chain conformation into the closer one occurred in neat PA11 without transformation of the type of crystal structure.
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Weathering and accelerated aging of high density polyethylene mixtures with regranulate
Bruzl, Dominik ; Tocháček, Jiří (referee) ; Bálková, Radka (advisor)
This master thesis deals with the effect of multiple extrusion (1, 2, 3) and the addition of 30, 60 and 90 % of this recycled material on the weathering and accelerated ageing of high density polyethylene (HDPE) copolymer. The weathering lasted 9 months and the accelerated ageing 1000 h at 65 °C. The degree of material degradation was assessed from changes in mechanical and physical properties and compositional changes using dynamic mechanical analysis and tensile testing, differential compensation calorimetry, thermogravimetric analysis and infrared spectrometry in the full attenuated reflection mode. The measurements showed that repeated extrusion as well as the addition of recycle material to the original one (R0) slightly slows down the photo-oxidative degradation during first month, but after that it does not have a negative or significant positive effect on the progress and rate of overall material degradation. A certain exception was the recycled material after the 3rd extrusion (R3), where the original properties comparable to R0 did not change much during ageing. The mechanical properties of the blends were better or comparable to R0 during ageing, but after months 6 and 9 the breaking strength of most of them decreased substantially as a result of the shortening of the chains. Accelerated ageing caused significant embrittlement in all samples, resulting in a reduction in yield strength by about half and almost immediate failure.
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Controlled life-time polypropylene
Demková, Eva ; Petruš, Josef (referee) ; Tocháček, Jiří (advisor)
The master´s thesis is focused on the characterization of degradation process of polypropylene and polypropylene with statistic copolymer into which manganese (II) stearate and cobalt (II) stearates were added at 0.05, 0.10 and 0.20 wt.% loadings. The aim of the thesis was to prepare the controlled life-time polypropylene. The degradation was studied at varying temperatures and prodegradant loadings. The prodegradants were synthetized and characterized using the FTIR and DSC techniques. Thermooxidation of the tested samples induced the changes in crystallinity, melting points and melt-flow indexes. Tensile strength and other mechanical properties were determined by means of the tensile test. The carbonyl index was determined using FTIR, the thermooxidation stability test was used to determine the activation energies of reactions. The changes in morphology of degraded samples were observed by SEM analysis.
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Effect of radiation cross-linking of PA on its thermomechanical properties
Mikel, David ; Tocháček, Jiří (referee) ; Jančář, Josef (advisor)
The influence of ionizing radiation on thermomechanical properties of polyamide reinforced by glass fibers was studied in this bachelor thesis. Ionizing radiation caused reduction of crystallinity, melting and crystallization temperature of polyamide. Tensile strength and tensile modulus increased due to irradiation, meanwhile elongation at break decreased. Notched and unnotched impact strength at laboratory and lower temperature increased with dose of radiation and after reaching the maximum it decreased for higher doses of radiation. Heat deflection temperature increased significantly with dose of radiation and after reaching the maximum it decreased for higher doses of radiation, too. Based on measured properties of investigated material was chosen optimal dose of radiation. Radiation rosslinking is an appropriate technology for increasing dimensional stability at elevated temperatures of polyamide reinforced by glass fibers.
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Kinetics of non-isothermal crystallization of polylactide with selected agents
Červený, Ľuboš ; Tocháček, Jiří (referee) ; Bálková, Radka (advisor)
The aim of submitted diploma thesis is the study of non-isothermal crystallization kinetics of polylactide (PLA) with selected agents (1 %) and observation of the emerging crystalline structure under polarizing optical microscope. The agents were talc, a mixture of organic salts with the addition of amorphous SiO2 (HPN 68L) and zinc stearate (HPN 20E) and LAK-301 (potassium salt of 5-dimethylsulfoisophtalate), which is a nucleating agent developer for PLA. The PLA matrix served as a reference. Non-isothermal crystallization took place on a differential scanning calorimeter at cooling rates () 0,3; 0,5; 0,7; 1; 1,5; 2 °C/min After non-isothermal crystallization, the crystalline fraction (Xc) od PLA was evaluated from X-ray diffraction analysis, and the supramolecular structure was observed after chemical degradative etching using confocal laser scanning microscope. The crystallization kinetics were evaluated by the methods of Jeziorny and Mo and the activation energy of the crystallization was determined according to the Friedmann method. All prepared materials were amorphous (Xc 40 % for up to 1,5 °C/min). However, for LAK-301, Xc decreased to 30 % already at the = 2 °C/min and it can be assumed that with increasing its nucleation activity will decrease. A spherulitic structure was observed in all samples, but the number and size of spherulites decreased with increasing and the appearance varied according to the type of agent. Both kinetic models proved to be unsuitable for materials with low Xc and the highest because the rate of crystallization did not change. With the Jeziorny method, it was possible to evaluate the kinetics only for the relative crystallinity Xt = 29–50 % and with the Mo method it was not possible to evaluate the data for the highest for PLA matrix and sample with HPN 68L. The samples with LAK-301 and HPN 68L showed the lowest activation energy.
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