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- Polyethylene grades (2) (entfernen)
The material parameters melt flow rate (MFR), density (D), notched impact strength (NIS) at –30°C, stress crack resistance [determined with the Full Notch Creep Test (FNCT)] and resistance to oxidative degradation (Ox) have been selected for a comparison of polyethylene grades in the European standard EN 15507. These parameters have a relationship with design type tests of packagings for the transport of dangerous goods.
This paper presents the results of additional investigations to determine the impact of the pre-storage time of jerricans with 55% nitric acid at 40°C and 23°C on the marginal drop heights in drop tests at –18°C, on the MFR and on the tensile properties. Jerricans made of different polyethylene grades were pre-stored with 55% nitric acid for 21, 42 and 84 days at 40°C and for six months at 23°C.
The tests showed that the NIS values at –30°C of polyethylene grades were not comparable with marginal drop heights determined in drop tests at –18°C.
Pre-damage with 55% nitric acid for 21 days at 40°C led to an increase in the marginal drop heights of the jerricans. Altering the test regulations by increasing pre-storage time with 55% nitric acid to 42 days would be an alternative.
The test results demonstrated clearly that pre-storage of the jerricans for six months at 23°C caused a higher increase in the MFR and lower marginal drop heights for the jerricans when compared with pre-stored jerricans for 21 days at 40°C.
The aim of this work was to study the interaction between high-density polyethylene (HDPE) grades as material for dangerous goods packagings and biofuels such as E85 and biodiesel. Jerricans made of two polyethylene (PE) grades were filled with these fuels and exposed to temperatures of 20°C and 40°C for 1 year. Tensile properties (tensile strength, breaking elongation and elasticity modulus) and melt flow rate (MFR) were determined once a month, and Fourier transform infrared (FTIR) spectroscopy was used to evaluate changes in the chemical structure.
Measurements of the MFR and tensile properties of the PE grades after 1 year of exposure to E85 showed only a slightly damaging influence. An increase in the peak of 1585 cm-1 (C=C) stretching vibrations is visible in the FTIR spectra after the immersion tests with E85. Therefore, packagings made of HDPE grades are suitable for the transport of E85.
An increase in the MFR with immersion time of the grades in biodiesel was measured, in particular, after 1 year of exposure. The elasticity modulus of the PE grades was reduced with immersion time. The FTIR spectra showed a broadening of the CO peak of 1740 cm-1 and the appearance of the hydroxyl group at 3500 cm-1. Both results are explained by secondary degradation products of the PE decomposition process caused by increasing unsaturated fatty acid content in the biodiesel. In light of the above mentioned, it was concluded that HDPE grades are not suitable as packaging materials for the transport of biodiesel.