|
|
Durability of Polyehtylene Ribbons from Netwrap
Huljak, Pavel ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
This diploma thesis deals with the measurement of mechanical properties and accelerated aging of monoaxially stretched polyethylene strips coming from three types of polymeric mesh, which serves to pack hay on baling machines. The strength of the strips is evaluated from two points of view. The first one is static tensile strength measured before and after accelerated aging at 23 °C and 40 °C, the second one determines the strength as the weight that causes the strip failure on a simple machine at 23, 40, 60 and 80 ° C. The results show that the smallest static strength has the least stabilized strip, which, on the other hand, revealed the highest strength in a dynamic loading. The change of supermolecular structure was evaluated by calorimetric measurements. The data shown only very little change of inner structure due to the average response of the whole crystalline phase comprising relatively wide distribution of crystallites. It is more than probable that supermolecular structure had been changed but the method is not sensitive to see the change of orientation of lamellae and macromolecular chains in them.
|
|
|
Influnce of chemical composition on mechanical properties of LLDPE stretch film
Vojáček, Jakub ; Tocháček, Jiří (referee) ; Poláček, Petr (advisor)
Thesis summarizes the problems of production and use of stretch film. The change of strength, ductility and relative relaxation effect in different times of drawing from role in three weeks was observed. Further, change of strength and ductility due to changes in the rate of deformation, exposure to accelerated aging in a UV chamber and changes in the loading direction were observed. Mechanical tests were realized on a tensile tester, relaxation tests on DMA and crystallinity changes were observed on the DSC. Relationship between chemical composition of stretch film and mechanical and thermomechanical properties were studied. It was found that chemical composition essential for stretch film properties. However, due to the impossibility to distinguish effects of chemical composition and process parameters was impossible to find clear relation describing this relationship.
|
|
|
Tack of textile coated with rubber blend
Mahel, Jindřich ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
The theoretical part of the diploma thesis describes basic composition of the rubber stock and the methods used for its processing. It summarizes current knowledge about building tack. The experimental part of the thesis deals with the methods of accelerated aging proposal, which have been used for testing UV radiation, ozone, temperature and humidity effect on tack. After bringing two samples together by defined pressure, the tack was determined by T-peel test. Surfaces of the samples were characterized by scanning electron microscopy and infrared spectroscopy. The aditivation of the rubber stock was done in order to compare the effects of tackifiers on accelerated aging.
|
|
|
Durability of Polyehtylene Ribbons from Netwrap
Huljak, Pavel ; Poláček, Petr (referee) ; Bálková, Radka (advisor)
This diploma thesis deals with the measurement of mechanical properties and accelerated aging of monoaxially stretched polyethylene strips coming from three types of polymeric mesh, which serves to pack hay on baling machines. The strength of the strips is evaluated from two points of view. The first one is static tensile strength measured before and after accelerated aging at 23 °C and 40 °C, the second one determines the strength as the weight that causes the strip failure on a simple machine at 23, 40, 60 and 80 ° C. The results show that the smallest static strength has the least stabilized strip, which, on the other hand, revealed the highest strength in a dynamic loading. The change of supermolecular structure was evaluated by calorimetric measurements. The data shown only very little change of inner structure due to the average response of the whole crystalline phase comprising relatively wide distribution of crystallites. It is more than probable that supermolecular structure had been changed but the method is not sensitive to see the change of orientation of lamellae and macromolecular chains in them.
|
|
|
Influnce of chemical composition on mechanical properties of LLDPE stretch film
Vojáček, Jakub ; Tocháček, Jiří (referee) ; Poláček, Petr (advisor)
Thesis summarizes the problems of production and use of stretch film. The change of strength, ductility and relative relaxation effect in different times of drawing from role in three weeks was observed. Further, change of strength and ductility due to changes in the rate of deformation, exposure to accelerated aging in a UV chamber and changes in the loading direction were observed. Mechanical tests were realized on a tensile tester, relaxation tests on DMA and crystallinity changes were observed on the DSC. Relationship between chemical composition of stretch film and mechanical and thermomechanical properties were studied. It was found that chemical composition essential for stretch film properties. However, due to the impossibility to distinguish effects of chemical composition and process parameters was impossible to find clear relation describing this relationship.
|
|
|
Tack of textile coated with rubber blend
Mahel, Jindřich ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
The theoretical part of the diploma thesis describes basic composition of the rubber stock and the methods used for its processing. It summarizes current knowledge about building tack. The experimental part of the thesis deals with the methods of accelerated aging proposal, which have been used for testing UV radiation, ozone, temperature and humidity effect on tack. After bringing two samples together by defined pressure, the tack was determined by T-peel test. Surfaces of the samples were characterized by scanning electron microscopy and infrared spectroscopy. The aditivation of the rubber stock was done in order to compare the effects of tackifiers on accelerated aging.
|
guest ::
