National Repository of Grey Literature 42 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Determining the compression behaviour of celluloses.
Ondrejček, Pavel ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
Mechanical resistance of tablets is usually described by crushing force, or by tensile strength. Method used in this thesis records crushing force and path of crushing. This force-path record can be used to calculate crushing energy. Crushing force, crushing path and crushing energy can be used to calculate other parameters that characterize tablet properties. This thesis uses crushing force, volume crushing force, tensile strength, crushing energy, volume crushing energy and crushing energy related to tablet weight to describe tablets compressed of powdered cellulose, microcrystalline cellulose, hydroxypropylcellulose and lactose monohydrate. Results of this thesis shows descent of tensile strength in this order: microcrystalline cellulose Avicel PH-112, microcrystalline cellulose Avicel PH-101, hydroxypropylcellulose, powdered cellulose and lactose monohydrate. Kinetic characteristics of tablets descent in this order: hydroxypropylcellulose, microcrystalline cellulose Avicel PH-101, microcrystalline cellulose Avicel PH-112, powdered cellulose and lactose monohydrate.
Determining the plasticity of calcium hydrogen phosphate
Hořínková, Pavla ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
The essential condition for a compaction of materials are their viscoelastic properties. There are many methods how to determine them. During a compaction process we can obtain elastic and plastic energies or energy of particle friction from a force-displacement record. After compaction the Young's modul of elasticity can be calculated from the tablet dilatation's values. The stress relaxation test is used for working out the plasticity of a compacted material. Using this test we get values of the methods FminA, FminB, Fpl and parameters of first order equation describing the pressure decrease during the stress relaxation. The viscoelastic properties of calcium hydrogenphosphate dihydrate were evaluated in this work by above mentioned methods except for energies. The results obtained by these methods were 288,080 MPa for the Young's modul of elasticity and 700,5167 MPa.s for the total plasticity Pc. The greater this value is, the better compaction properties the material has.
Determining the plasticity of microcrystalline celulose
Skálová, Marie ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
Important properte of pressed (compacting) materials is their energy and plasticity. For their calculation is used several methods. One of values elasticity or plasticity energy from record power-line, in another metod is used elastic recovery, which is used for calculation of Young's elastic modul and the third one value stress relaxation of tenseness. In this analyze we can get parameters as FminA, FminB, Fpl and also characterization of ralation dependence compression in the time. In this dissertation is valueted one of the most common excipient microcrystaline celulose by all these methods. Basic characteristic is Young's elastic modul ,which is 253,794MPa and total plasticity is 995,48. We can say, that values of total plasticity means good compressible material and that plasticity increases with increasing of total plasticity.
Determining the plasticity of mannitolum
Votava, Jakub ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
The visco-elastic characteristics and knowledge of them are the important factors that influence pressability of materials. These characteristics differ for every material and it is possible to determine them by variety of methods. In our thesis (chapter Experiments) we evaluated the relationship "force - travel" and determined elasticity and plasticity of materials. The test of relaxation of tense is another way to determine plasticity of materials. The results are parameters of FminA, FminB, FPL and parameters of single-parametric equation that describes decrease of preassure in a tablet during the relaxation period. These parameters and their evaluation are the goal of this thesis. We determined the Young's modulus of elasticity from the tablet dilatation measure restults. The value of Young's modulus of elasticity for mannitol is 413,36 MPa. The value of total plasticity Pc is 91,34177 MPa.s. Generally: increasing value of total plasticity determines increase of tablet material pressability.
Determining the compression behaviour of fillers and magnesium stearate
Szwedová, Lenka ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
1 Abstract The energy of tablets compaction is obtained from the force-distance record. The aim of this work was to determine accumulated energy in a tablets (plastic energy), to determine energy released from a tablet after compaction (elastic energy) and summation of these two energies. Mixtures of magnesium stearate 0%, 0,5% and 1% were prepared in a blending cube. The T1 - FRO 50 compacting machine was used for compacting tablets (weight of each tablets was 500 mg). Compacting forces were 5, 10 and 15 kN. In the first procedure the compaction was ceased after reaching the maximal compaction force, in the second procedure the upper punch was stopped when the maximal compaction force was reached and during 180 s dwell time of decreasing compacting force was recorded while the tablet height was kept constant. The results show that increasing concentration of lubricant leads to a decrease of accumalated energy in a tablet and on the contrary it leads to an increase of energy released from a tablet. The 180 s dwell time with a tablet height kept constant increases plastic energy because of forming more bonds. Microcrystalline cellulose is characterized by higher plastic and lower elastic energy than lactose monohydrate.
Determining the compression behaviour of microcrystalline celluloses.
Coufal, Libor ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
Coufal Libor, diploma paper, June 2009 Tablets are a very expanded dosage form. All new investigation in their technology are worth. While in pharmacopoeial method of measurement of mechanical strength of tablets evaluate by means of the strength at which the tablet breaks. This paper is based on the strength - course record. From this record, it is possible to ascertain other parameters of crushing process, such as the course of crushing, the crushing force and deformation energy. The radial strength, the volume deformation energy and deformation energy related to tablet weight are calculated from them. Tablets prepare from microcrystalline celluloses, hydroxyehylcelulose, powdered lactose monohydrate and substance called PharmDry (maltodextrine) were evaluated by means of these parameters. Results of this thesis shows descent of tensile strength in this order: microcrystalline cellulose Avicel PH-200, microcrystalline cellulose Avicel PH-102, maltodextrine, hydroxyethylcellulose and powdered lactose monohydrate. Kinetic characteristics of tablets descent in this order: microcrystalline cellulose Avicel PH-102, hydroxyethylcellulose, maltodextrine, microcrystalline cellulose Avicel PH-200 and powdered lactose monohydrate. Key words: strength - course record, course of crushing, crushing force,...
Viscoelastic properties of microcrystalline cellulose and lactose
Sosvorová, Lucie ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
The aim of this work was to evaluate the use of creep test during the compaction of microcrystalline celluloce Avicel PH 102, lactose FlowLac 100 and their mixtures in rates of 75:25, 50:50 and 25:75. Individual substances or mixtures were compressed by compression forces 0,25; 0,5; 1; 2; 3; 4; 5; 7,5; 10 and 15 kN. After the compression of each tablet a report describing the process of compression was procured. These dates were obtained by software connected with compression machine. Obtained relation bethween displacement and time was transfered to the relation bethween parameter J (creep compliance) and time. This relation was finally characterized by four basic parameters: E1 (immediate elasticity), E2 (retardet elasticity), P1 (plasticity) and FP (factor of plasticity). From the results we can see that microcrystalline celluloce Avicel PH 102 compared to lactose FlowLac 100 has lower elasticity and higher plasticity. With the decreasing value of microcrystalline celluloce Avicel PH 102 in the mixture the elasticity is inceased and plasticity decreased. Further was proved, that creep test method is usable in praxis for evaluation of pharmaceutical supplementary substances (fillers) used in the tablet manufacture. This test clearly valued the elasticity and plasticity by way of concrete numerical...
Viscoelastic properties of microcrystalline cellulose of Avicel PH 200
Skálová, Marie ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
In this dissertation the viscoelasticity of the most common excipient microcrystaline celulose was valuated and viscoelasticite parametres were compared to three substances. Viscoelasticity was valuated by two methods..The first method is Creep test. In this analyze the compression force is constant and hold for 180s. During this time height of the tablet was lowered. The diffrences of tablet height was noted and used for calculation in Crčel test. Parameters of elasticity got by this method are FCT1,FCT2 and parameters of plasticity are PCT1,FP. When the parameters of elasticity increase the elasticity decrease. When the parameter FP increases the plasticity increases too. The higher the value of PCT1 is the lower is the plasticity. Stress relaxation is the second method. In this analyze hight of tablet is constant and decline compression force is recorded. In this analyze we noted the decline for 180 sec. In this way we get parameters of elasticity ESR1, ESR2, ESR3 and parameters of plasticity PSR1, PSR2, PSR3. The plasticity increases when parameter P increases. Comparing three substances the elasticity increases in-line Emcompress, Avicel, Flowlac and the elasticity decreases in-line Emcompress, Avicel, Flowlac.
Determining the compression behaviour of hypromelloses.
Palounková, Zuzana ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
The diploma work is concerned with a study of mechanical resistance which is assessed through the tablet crushing force and tensile strenght.In this work there was used tablet measuring method resulting from the recording of force - path, while the crushing process is assessed not only by crushing strenght but also by the path of crushing. Using the crushing force, crushing path and tablet crushing force is possible to compute next parameteres of crushing process detailing tablet properties as are volume crushing force, volume crushing energy and weight crushing energy. Assessed tablets were compacted of microcrystalline cellulose, hydroxypropylmethylcelulos, lactose and calcium hydrogen phosphate. From the result of work follows that crushing force (possibly tensile strenght) is decreasing in assessed adjuvants microcrystalline cellulose Ceolus, hydroxypropylmethycellulose HPMC K4, hydroxypropymethylcellulose HPMC K100, calcium hydrogen phosphate Emcompress, lactose Tablettosa respectively. Tablet breakage kinetics parameteres were decreasing with used substances in order microcrystalline cellulose Ceolus, hydroxypropymethylcellulose HPMC K100, hydroxypropylmethycellulose HPMC K4, and the lowest results were registered with lactose Tablettossa and calcium hydrogen phosphate Emcompress.
Determining the plasticity of lactose
Patočková, Simona ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
The aim of this work was to take charakteristic of lactose and their influence on compressibility. Plastic properties ensuring better compressibility of material, whereas elastic properties make difficult for compressibility. Plasticity and elasticity are important characteristics of compacting materials. Several methods are commonly used for calculation of these parameters. One of the methods utilizes elastic recovery. On the base of relation between elastic recoveries and compression pressure, the Young's modul of elasticity is counted. Elastic and plastic energy is acquired from measurement force - displacement representing continuance of pressing process. Force - displacement curves are obtained from measurements of punch force and displacement. Energy is needed for the compression of material and formation of strong compacts. The properties of the compact are correlated with the energy input. The force - displacement profiles as such may be useful as a material charakteristic. Furthermore, the stress relaxation test is exploited for calculation of plasticity. By this test the parameters F min A, F min B, FPL and also characteristics of single parametric relation dependence of compacting pressure on time are counted. In this work, the lactose was evaluated by all mentioned methods. The basic...

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See also: similar author names
1 ŠPAČEK, Vladimír
3 Špaček, Vojtěch
4 Špaček, Václav
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