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- Bi-oriented films (1)
- Capillary discharge (1)
- Drop test (1)
- Dynamic rheology (1)
- Finite element (1)
- Flame retardance (1)
- Functionalization of polymer (1)
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A guided drop test was performed to achieve a defined and reproducible impact orientation of jerrycans. The drop heights where 50% of the jerrycans experienced a failure from a crack where fluid can escape (50% failure drop height) were compared among jerrycans made of four different materials, in their original state and preconditioned with standard liquids. To analyse the impact of only elevated temperatures, the packages were preconditioned for 21?days at 40°C without the use of chemicals.
The 50% failure drop height was compared by using Young's modulus; the notched impact strength (NIS) of specimen cut from plates which were manufactured by compression moulding and the notched tensile impact strength of specimen cut-outs of the jerrycans' side walls. The NIS depends highly on the thermal preconditioning of the plates being manufactured by compression moulding. A trend can be seen that a higher Young's modulus, a higher NIS and a higher notched tensile impact strength result in a higher 50% failure drop height, but the values are spread. The influence of the wall thickness cannot be neglected.
The change of the 50% failure drop height in regard to the preconditioning at 40°C with and without nitric acid was compared in terms of their resistance to molecular degradation, density and degree of crystallinity. The conditioning at elevated temperature causes post-crystallization. It was shown that the resistance to molecular degradation determined on pressed plates correlates with the change of the 50% failure drop height after pre-storage with nitric acid.
The effect of the wall thickness variation of blow-moulded bodies made of high-density polyethylene on an internal pressure test after prestoring the packaging with standard liquids was evaluated in experiments and simulations. The objects of the investigation were jerrycans used for the transportation and storage of dangerous goods.
The wall thickness was determined using two alternative methods to the magnetostatic measurement. These alternative methods are used for research purpose to get a volumetric model of the jerrycan wall as a geometric model for the simulation. The comparison of the experiments and the simulations of the internal pressure test were performed using the digital image correlation method. The integral strain and deformation of the whole jerrycan was detected by measuring the total mass of the jerrycan being filled with water during the internal pressure test. This is a suitable alternative to the optical measurements of local deformation by the digital image correlation method. Prestorage at 40°C without the influence of chemicals strengthens the jerrycan, whereas the swelling effect of butyl acetate and hydrocarbon mixture softens the jerrycan. The comparison with the experiment is necessary to verify the accuracy of the simulation. It shows that the deformation can be simulated more precisely by using the actual measured geometry. The weakening of the high-density polyethylene caused by a hydrocarbon mixture can be simulated using the Arrhenius equation. The aim of the simulation was to discover whether it is possible to use specimens to predict the behaviour of a packaging both after the influence of standard liquids.
Combinations of different common flame retardants in wood–plastic composites (WPCs) are tested to identify synergistic or antagonistic effects with the goal of improving the fire performance of WPCs. Flame retardants investigated are expandable graphite (EG), ammonium polyphosphate (APP), and red phosphorus (RP) and combinations of two of them are used. The fire behavior is studied by cone calorimetric measurements. Additional thermogravimetry is used for further investigations. The fire tests show that EG has the highest potential for flame retardancy, but due to its expansion it cracks the formed residue layer. Combinations of EG with RP or with high amounts of APP are able to suppress this cracking.
Among new types of plasma processes, the underwater plasma is one of the most attractive methods for functionalization of polymer surfaces. The interesting features of plasma solution system are that the material surfaces to be modified remain in contact with the plasma-moderated solution. The role of plasma-moderated liquids, allows the reach of the reactive species through solution onto the geometrically hindered sites. The UV radiation produced in plasma formation helps in generating additional excited, ionized, and dissociated molecules and species in the reaction solution. An interesting feature of the technique is its flexibility to use a wide variety of additives as or in solution system. This allows us to create a selective or monotype functionalization of material surfaces. Such system was studied for the selective hydroxyl functionalization of polypropylene surface. The oxidation of polymer surfaces and the introduction of O-containing functional groups by underwater plasma was found to exceed concentrations typically achieved in oxygen low-pressure gas discharge plasmas up-to two-folds (maximal 56 O/100 C). The fraction of OH groups among all O-containing moieties amounts from 25 to 40% in comparison to that in the gas plasma of about 10% OH groups. Addition of hydrogen peroxide into this same system increases the fraction of C—O bonds up to 75% (27-OH/100 O). A study was focused to optimize the role of hydrogen peroxide on the efficiency of oxidation and selectivity with chemical derivatization with respect to the formation of mono-sort hydroxyl functionalities, calculated using a chemical derivatization technique.
Study of carboxylic functionalization of polypropylene surface using the underwater plasma technique
(2009)
Non-equilibrium solution plasma treatment of polymer surfaces in water offers the possibility of more dense and selective polymer surface functionalization in comparison to the well-known and frequently used low-pressure oxygen plasma. Functional groups are introduced when the polymer surface contacts the plasma moderated solution especially water solutions. The emission of ions, electrons, energy-rich neutrals and complexes, produced by the ion avalanche are limited by quenching, with the aid of the ambient water phase. The UV-radiation produced in plasma formation also helps to moderate the reaction solution further by producing additional excited, ionized/dissociated molecules. Thus, monotype functional groups equipped polymer surfaces, preferably OH groups, originating from the dissociated water molecules, could be produced more selectively. An interesting feature of the technique is its flexibility to use a wide variety of additives in the water phase. Another way to modify polymer surfaces is the deposition of plasma polymers carrying functional groups as carboxylic groups used in this work. Acetic acid, acrylic acid, maleic and itaconic acid were used as additive monomers. Acetic acid is not a chemically polymerizing monomer but it could polymerize by monomer/molecular fragmentation and recombination to a cross linked layer. The other monomers form preferably water-soluble polymers on a chemical way. Only the fragmented fraction of these monomers could form an insoluble coating by cross linking to substrate. The XPS analysis was used to track the alterations in -O-CO- bond percentage on the PP surface. To identify the -COOH groups on substrate surface unambiguously, which have survived the plasma polymerization process, the derivatization with trifluoroethanol was performed.
Blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) were processed into biaxially drawn films, and samples taken from the bi-oriented films were then investigated by dynamic rheology experiments in the melt state. Storage modulus G and loss modulus G were determined in the frequency range of 10-2-102 rad/s at temperatures between 260 and 300°C. Although the time-temperature superposition (TTS) principle was found to hold in the high frequency regime, a breakdown of TTS was observed at low frequencies, and the terminal behavior of the storage modulus G of the blends departs drastically from the terminal behavior observed for the blend components. This is caused by interfacial surface tension effects. The results indicate that despite the effect of transesterification reactions, the PET/PEN blend systems investigated consist of a microseparate phase of PEN platelets in a matrix of PET. This morphology is produced when the blends are processed into biaxially oriented PET/PEN films, and droplets of PEN are deformed into a lamellar structure consisting of parallel and extended, separate layers. The large interfacial surface area of the bi-oriented PET/PEN blends leads to remarkably strong interfacial tension effects in dynamic rheology measurements.