|
|
Biodegradable plastics
Schifferová, Zuzana ; Jan, Vít (referee) ; Molliková, Eva (advisor)
The aim of this bachelor theses is to discuss the process of biodegradation occurring with biodegradable polymers including factors affecting this process. The theses also introduces some types of biodegradable plastics including their properties. At last it discusses waste management of these plastics and their ecological impact.
|
|
|
Influence of selected agents on crystallization power of polylactide
Kurakin, Yuriy ; Přikryl, Radek (referee) ; Bálková, Radka (advisor)
The influence of seven additives on the crystallization ability of polylactide (PLA), melt flow index (MVR) and mechanical tensile properties was studied. Pressed plates with a thickness of 0.8 mm were tested. Selected additives added in amounts of 0.5 and 1.0% were as follows: talc, sodium benzoate, mixtures of organic salts with amorphous SiO2 and zinc stearate, metal salt, phosphate salt, and potassium salt of 5-dimethylsulfoisophthalate (LAK-301 - nucleating agent developed for PLA). Non-isothermal crystallization measurements were performed at different cooling rates (0.3; 0.5; 0.7; 1.0 and 1.5 ° C). All nucleation agents increased the MVR of PLA except talc; the largest increase (9-fold and 24-fold) was the addition of metal salt. The additives did not fundamentally change the mechanical properties. All samples were rather brittle (the most brittle with LAK-301), the modulus of elasticity was around 1.2 GPa for all samples, the strength of PLA was increased the most by the addition of 1% talc (by 12%) and the elongation at break was increased by organic salt with SiO2. All samples with nucleating agents content of 1% were amorphous (crystalline content did not exceed 2%). Thus, the addition of reagents did not support the crystallization process during rapid cooling, even in the case of LAK-301. However, LAK-301 was acting as an excellent nucleating agent at slow cooling rates (1.5 °C / min and below). The nucleation activity of the additives decreased in the following order: LAK-301, organic salt with zinc stearate, talc, organic salt modified with amorphous SiO2 and phosphate salt. Samples with sodium benzoate and metal salt were crystallizing on cooling in several steps and it was not possible to use the method of Dobrev and Gutzow to evaluate the nucleation activity.
|
|
|
Study of Electric Properties of Electrochemical Transistors with Ionic Liquids
Blahut, Jan ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
This bachelor’s thesis is focused on preparation of organic electrochemical transistors and following characterization of electric properties of these systems. Two types of electrode systems were used for preparation – glass substrates with steamed oxide of indium and tin and polylactic acid substrates with admixture of carbon soot. Three methods were tested for creation of PEDOT channel. Materiál printing, spin-coating and manual application. The measurement shows, that voltage applied to gate electrode has no effect switching of transistor. Size and polarity of current between source and drain electrodes has a major influence here.
|
|
|
Biodegradation of polyesters and other polymers in soil and compost
Papala, František ; Smilek, Jiří (referee) ; Obruča, Stanislav (advisor)
This diploma thesis studies the biodegradation of polyhydroxybutyrate (PHB) and polylactic acid (PLA) within soil and compost environments. The experimental part of this work is concerned with the differences in degradation across environments and the effects of degraded polymers on the environment itself. Experiments revealed that higher temperature and potentially also higher humidity substantially affect the rate of biodegradation. A significant degradation of all the polymers was observed in the compost medium, while polymers within the soil medium did not demonstrate any visible change nor change in mass after the 8th week of experiment. Even though SEM images revealed slow microbial degradation of soil PHB, this was not seen in any of the soil-incubated PLA samples. This might indicate primarily abiotic mechanism of PLA degradation. Germination and grow tests, which used the prepared polymer-enriched compost as a substrate and fertilizer, respectively, did not in most cases reveal any significant differences between individual plants across substrates. This seems to imply that neither the examined polymers nor their degradation products generated during composting are phytotoxic.
|
|
|
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.
|
|
|
Composting of biodegradable polymers
Hollá, Tereza ; Smilek, Jiří (referee) ; Obruča, Stanislav (advisor)
This master’s thesis deals with the study of composting of polyhydroxybutyrate (PHB) and polylactic acid (PLA). The experimental part focuses on the composting test based on the IS/ISO 20200 standard, in which biopolymers were degraded within 8 weeks. The advantage of the composting test was the unique use of bags for polymer granules, which simplified the handling of samples. The placement of the polymers ensured an even load of compost, which simulated the landfill environment, which also made this experiment exceptional. The use of different methods of analysis ensured the investigation of the influence of compost on the degradation of polymers, but also the influence of polymers on the compost microbiome. In the compost environment all of the studied polymers degraded. After 8 weeks the weight loss of approximately 40 % was detected in PHB. Amorphous PLA degraded completely in the 5th week of experiment, while semicrystalline PLA lost approximately 70 % of its weight in 8 weeks. Using SEM images and SEC analysis, we conclude that PHB degradation was predominantly biological. Degradation of PLA samples was found to be predominantly abiotic. Analysis of compost samples revealed that the enzymatic activity of esterases increased in composts with polymers compared to compost without polymers. The effect of polymers on the microbiome in compost was analyzed using Biolog EcoPlates™. Compost with PHB showed a high ability to adapt to various substrates and microbiome expanded during composting. In the case of a sample with semicrystalline PLA, it was found that in the last week of composting, the ability of microorganisms to adapt and use substrates decreased, which indicates a possible negative effect of this polymer on compost development.
|
|
|
Biodegradation of bioplasts in compost environment
Vodička, Juraj ; Kovalčík, Adriána (referee) ; Obruča, Stanislav (advisor)
This master’s thesis focuses on biodegradation of polyhydroxybutyrate (PHB) and polylactic acid (PLA). The theoretical part discusses an origin, properties and applications of investigated biopolyesters, and so the enzymology of their biodegradation. The experimental part deals with biodegradation of these polymers in liquid medium using several pure thermophilic bacteial strains and controlled composting of these bioplastics. Amongst six tested thermophilic bacterial strains only one showed PHB-biodegradation activity – strain Schlegelella thermodepolymerans. No degradation degree of amorphous or semi-crystalline PLA was observed. Mainly disintegration of both forms of PLA articles was observed in compost environment, thus the abiotic mechanism of its decomposition was indicated. After 4 weeks of composting, the relative weight loss of 99 % and 63 % was detected in amorphous and semi-crystalline PLA respectively. On the contrary, the weight loss of PHB after 4 weeks of composting reached 36 %, moreover, a half decrease of molar mass was observed using SEC. The surface erosive mechanism of PHB-biodegradation was stated using SEM. By monitoring of esterase, lipase and protease activities, no influence on the compost by polymer presence was concluded at statistical significance.
|
|
|
Study on biotechnological potential of thermophilic gram-positive bacterium Brevibacillus sp. Bz
Filimonova, Anastasiia ; Obruča, Stanislav (referee) ; Pernicová, Iva (advisor)
Předmětem předložené diplomové práce je studium biotechnologického potenciálu termofilní grampozitivní bakterie Brevibacillus borstelensis BZ. Teoretická část obsahuje obecnou charakterizaci termofilních organismů a jejich termozymů. Popisuje také adaptivní molekulární mechanismy, které zajišťují termostabilitu těchto proteinů. Závěr teoretické části je věnován biodegradaci odpadních substrátů a polymerů na bázi přírodních a fosilních zdrojů. První část experimentální práce se zabývá produkcí hydrolytických enzymů na různých původních zdrojích a odpadních substrátech. Díky intenzivní enzymatické produkci na původních zdrojích je Brevibacillus borstelensis BZ považován za velmi slibného producenta termostabilních enzymů, konkrétně xylanáz a celuláz. Testovaný bakteriální kmen BZ byl schopen produkce termostabilních enzymů i na odpadních substrátech. Na vybraných substrátech kmen BZ přednostně produkoval xylanázy. Díky tomu byla xylanázám věnována zvláštní pozornost, kdy bylo testováno teplotní a pH optimum. Závěrem experimentální práce byla testována schopnost bakterie Brevibacillus borstelensis BZ degradovat vybrané polymery na bázi přírodních a fosilních zdrojů. Kmen BZ poskytl nový pohled na biologický rozklad polyethylentereftalátu (PET), amorfní frakce kyseliny polymléčné (PLA), semikrystalické PLA a polyhydroxyalkanoátů (PHA). Pozorováním povrchu PET fólie skenovacím elektronovým mikroskopem (SEM) se potvrdilo zdrsnění materiálu, přítomnost rýh a naprosté pronikání bakterie skrz fólii. Pokud jde o polymery na bázi přírodních zdrojů, PHA granule byly zcela degradovány. Studiem morfologie povrchu obou zmíněných PLA bylo prokázáno jasné zhoršení jejich struktury přítomností jam a trhlin na povrchu polymerů.
|
|
|
Employment of thermophilic bacteria for biodegradation of synthetic and natural polymers
Csölle, Eduard ; Sedlář, Karel (referee) ; Obruča, Stanislav (advisor)
This bachelor’s thesis deals with the employment of thermophilic bacterium Schlegelella thermodepolymerans for biodegradation of selected polymers, namely poly(3-hydroxybutyrate) (PHB), polylactic acid (PLA), and poly(butylene adipate-co-terephthalate) (PBAT). The theoretical part focuses on the properties and origin of these bioplastics, the characteristics of the studied bacteria, and the general course of the biodegradation process. The experimental part discusses the twenty-day cultivation of three tested strains in the presence of the mentioned polymers and the subsequent evaluation of the degradation rate of these materials. The greatest increase in biomass content was observed by spectrophotometry for strain DSM 15344 when cultured on PHB. With blank samples (without polymers), it was shown that for significant growth, the bacteria had to truly utilize the polymers present. Gravimetric analysis of biomass content confirmed that PHB was the most suitable substrate for cultivation. The highest mass losses were recorded for PHB and were around 30 % across all three strains. For strain LMG 21645, the mass has decreased by almost 33 %. The weight losses of PLA and PBAT were considerably lower. Nevertheless, the most significant molecular weight loss was observed by SEC-MALS for PLA, reaching approximately 80 % for strain DSM 15264. SEM analysis of the polymer surface confirmed that the biodegradation of PHB occurs by enzymatic surface erosion. In contrast, the PLA and PBAT samples did not show any signs of biodegradation.
|
|
|
Biodegradation of 3D printed composites based on poly(3-hydroxybutyrate)
Gazdová, Nikol ; Menčík, Přemysl (referee) ; Melčová, Veronika (advisor)
This bachelor thesis deals with the biodegradation of 3D printed bodies composed of poly(3- hyroxybutyrate), polylactic acid, bioceramics and plasticizer. These components were selected for their biocompatibility and properties that could be used in tissue engineering as a temporary, absorbable bone tissue replacement. The main objective was to investigate the effect of the individual constituent bodies on the biodegradation itself. Biodegradation was carried out at 37 °C in a solution simulating the ionic concentration of blood plasma. Samples were sequentially withdrawn at monthly intervals for five months. To evaluate the results, 2 methods were used, weight change and compression test, where the strength of each body was evaluated. From the evaluation of the data it was not possible to reach a uniform result on which substance influences biodegradation the most, because it always depended on the ratio of the other substances. To investigate the effect of poly(3-hydroxybutyrate) and polylactic acid on the rate of biodegradation, mixtures of RP9, RP10 and RP15 were compared. It showed that a higher polylactic acid and lower poly(3-hydroxybutyrate) content had a significant positive effect on the biodegradation rate, as the difference between the weight loss for the RP9 blend with the highest poly(3-hydroxybutyrate) content and the RP10 blend with the highest polylactic acid content was 8.37% for solid bodies and 4.13% for porous bodies. For strength, the difference was 73.32% and 73.65% for the solid and porous bodies, respectively. Observing the effect of bioceramic content on the RP11, RP12 and RP15 mixtures, we concluded that this effect was almost negligible on the biodegradation rate The difference in weight loss between the RP11 mixture with the lowest bioceramic content and the RP12 mixture with the highest bioceramic content was only 1, 68 % for solid bodies and 0.99 % for porous bodies, while mixture RP15 showed the highest biodegradation rate despite having a medium value of bioceramics in the mixture. For the mechanical properties, this then amounts to a difference of 10.4% for the solids and 7.57% for the porous bodies. When comparing the effect of plasticizer for mixes RP13, RP14 and RP15, the effect was more on the strength drop, where the difference in strength drop for mix RP13 with the lowest plasticizer content and RP14 with the highest plasticizer content was different by 20.3% and 18.16% for the solid and porous body, respectively. The decrease in weight was then different by 4.1 % and 0.83 % for the solid and porous body, respectively. Finally, bioceramics from different companies emerged as an important element for the biodegradation rate. Hydroxyapatite from Applichem was the best biodegraded and hydroxyapatite from CN Lab was the worst. The difference for weight loss was 17.35% for the solid and 5.93% for the porous body. The strength loss was then different by 55.6% for the solid body and 33.38% for the porous body.
|
guest ::
