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Influence of linear low density polyethylene on flow of recycled polyethylene
Křivánková, Eliška ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
The work deals with the study of rheological behavior of recycled polyethylene (rPE) and the influence of linear low density polyethylene (LLD). The addition of LLD, which is added into rPE in order to set melt flow index and processing conditions, was 5–20 %. The received rPE was characterized by Thermogravimetry and Differential Scanning Calorimetry. Rheological measurements were performed on a reometer with plate-plate geometry in oscillatory mode (deformation of 0.25%, frequency range 0.01–100 Hz and temperature of 140, 170, 180 and 190 °C) and in flow mode (shear) at 190 °C and the shear rate 0,001–100 1/s. The recycled material contained low density polyethylene and LLD in a range approx. 1 : 1 and small amount of chalk and polypropylene. Complex viscosity and complex shear modulus together with their components were evaluated from oscillatory measurements of rPE, blends and neat polymer components. The change of microstructure, molecular weight and its distribution was evaluated as well. The melt stability in time was evaluated from flow measurements together with zero shear viscosity and melt elasticity. Miscibility of melt blends was evaluated from both type of measurements. It was found that the addition of 5–15% of LLD shifted rheological behavior of rPE into that of LLD but rheological behavior of the blend with the addition of 20% of LLD is the same as that of rPE. The reason is not different content of short and long branches but specific interaction of macromulecules. This knowledge may facilitate to set proper conditions of further processing of rPE regarding its composition.
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Characterization of blowing films from softened polylactide
Kubíček, Václav ; Tocháček, Jiří (referee) ; Bálková, Radka (advisor)
The master's thesis focuses on preparation of blown films from polylactid acid (PLA) which was blended with selected polyesteres – poly(butylene adipate-co-terephtalate) (PBAT), polycaprolactone (PCL) and polybutylene succinate (PBS) – and thermoplastic starch (TPS) in amount of 30% in order to soften PLA films. The influence of the aditives on static and mechanical tensile properties, on structure, morphology and thermal properties of the films was determined and the obtained parameters were compared to properties of films prepared from neat PLA and high density polyethylene (HDPE). The results showed that the additives increased crystalinity of PLA and thus significantly influenced the properties of the films. In contrast to the film from neat PLA, softening in terms of lowering glass transition temperature occured only by adding PBS and TPS, in terms of increasing ductility only by adding PBAT. All PLA films showed nearly constant elastic modulus up to the beginning of glass transition enabling their potential application till 50 °C. Preparation of the film with TPS was problematic and the film showed the worst mechanical properties. Preparation of other films was without any problems. The most promising additive from the tested ones was PBAT which showed comparable mechanical properties as the film from HDPE.
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Sublethal effects of pesticide mixtures on crayfish
HOVORKOVÁ, Anna
Prometryn, a triazine herbicide, was banned in Europe in 2004. Metazachlor, a chloracetamide used to treat mainly oilseed crops, is one of the herbicides still in use. Individual pesticides or their metabolites can cause adverse effects in the aquatic environment, and the resulting mixtures of pesticides that can form in the environment are another issue in terms of adverse effects in the environment. The aim of this study was to assess the effect of mixtures of pesticides mixed from selected concentrations (0.01 mg.l-1, 0.1 mg.l-1, 1 mg.l-1). Pesticides were also tested individually at selected concentrations. The biochemical profile of hemolymph and antioxidant biomarkers and oxidative stress biomarker in hepatopancreatic, muscle and gill tissues of marbled crayfish were determined. Toxicity was assessed using a subchronic toxicity test performed over a period of 8 days. Metazachlor concentrations (0.1 and 1 mg.l-1) caused decreasing ALT, Cl-, Mg2+ and Ca2+ levels and increasing NH3 levels in hemolymph. The effect of all tested mixtures was observed on the increase of GLO, ALT and NH3 levels, here a synergistic effect of the mixtures was observed. The activity of antioxidant biomarkers was affected only in CAT for prometryn (0.01 mg.l-1) and metazachlor (0.01 and 1 mg.l-1). LPO levels were affected by metazachlor (0.01 mg.l-1). There was no effect of pesticide mixtures on LPO levels and antioxidant enzyme activities.
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Matrix computations for mixtures and solutions
Voborníková, Iveta ; Duintjer Tebbens, Erik Jurjen (advisor) ; Bernhauerová, Veronika (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of Biophysics and Physical Chemistry Candidate: Iveta Voborníková Thesis supervisor: doc. Dipl.-Math. Erik Jurjen Duintjer Tebbens, Ph.D. Title of diploma thesis: Matrix computations for mixtures and solutions In this work, we determined drug concentrations from mixtures using multicompo- nent analysis without separating them. The condition was the knowledge of the molar absorption coefficients of individual drugs for certain wavelenghts. To do this, we used tools from matrix calculations, especially the Moore-Penrose inverse, and we were in- terested in whether we would achieve more accurate results using standard, square systems or overdetermined systems of linear equations. Based on the results, we came to the conclusion that there is no dependence between the accuracy of the results and the number of wavelengths used. Only in some cases did the results appear to be more accurate when using overdetermined systems with a higher number of wavelengths. Keywords: mixtures, solutions, linear systems, least squares problems, Moore-Penrose pseudoinverses 1
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Characterization of blowing films from softened polylactide
Kubíček, Václav ; Tocháček, Jiří (referee) ; Bálková, Radka (advisor)
The master's thesis focuses on preparation of blown films from polylactid acid (PLA) which was blended with selected polyesteres – poly(butylene adipate-co-terephtalate) (PBAT), polycaprolactone (PCL) and polybutylene succinate (PBS) – and thermoplastic starch (TPS) in amount of 30% in order to soften PLA films. The influence of the aditives on static and mechanical tensile properties, on structure, morphology and thermal properties of the films was determined and the obtained parameters were compared to properties of films prepared from neat PLA and high density polyethylene (HDPE). The results showed that the additives increased crystalinity of PLA and thus significantly influenced the properties of the films. In contrast to the film from neat PLA, softening in terms of lowering glass transition temperature occured only by adding PBS and TPS, in terms of increasing ductility only by adding PBAT. All PLA films showed nearly constant elastic modulus up to the beginning of glass transition enabling their potential application till 50 °C. Preparation of the film with TPS was problematic and the film showed the worst mechanical properties. Preparation of other films was without any problems. The most promising additive from the tested ones was PBAT which showed comparable mechanical properties as the film from HDPE.
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Influence of linear low density polyethylene on flow of recycled polyethylene
Křivánková, Eliška ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
The work deals with the study of rheological behavior of recycled polyethylene (rPE) and the influence of linear low density polyethylene (LLD). The addition of LLD, which is added into rPE in order to set melt flow index and processing conditions, was 5–20 %. The received rPE was characterized by Thermogravimetry and Differential Scanning Calorimetry. Rheological measurements were performed on a reometer with plate-plate geometry in oscillatory mode (deformation of 0.25%, frequency range 0.01–100 Hz and temperature of 140, 170, 180 and 190 °C) and in flow mode (shear) at 190 °C and the shear rate 0,001–100 1/s. The recycled material contained low density polyethylene and LLD in a range approx. 1 : 1 and small amount of chalk and polypropylene. Complex viscosity and complex shear modulus together with their components were evaluated from oscillatory measurements of rPE, blends and neat polymer components. The change of microstructure, molecular weight and its distribution was evaluated as well. The melt stability in time was evaluated from flow measurements together with zero shear viscosity and melt elasticity. Miscibility of melt blends was evaluated from both type of measurements. It was found that the addition of 5–15% of LLD shifted rheological behavior of rPE into that of LLD but rheological behavior of the blend with the addition of 20% of LLD is the same as that of rPE. The reason is not different content of short and long branches but specific interaction of macromulecules. This knowledge may facilitate to set proper conditions of further processing of rPE regarding its composition.
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