Comparison of the Material Parameters of Polyethylene Grades with the Test Performance Behaviour of Packagings for the Transport of Dangerous Goods in Relation to the Pre-Storage Time with 55% Nitric Acid

摘要

The material parameters melt flow rate (MFR), density (D), notched impact strength (NIS) at -30℃, 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℃ and 23℃ on the marginal drop heights in drop tests at -18℃, 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℃ and for six months at 23℃. The tests showed that the NIS values at -30℃ of polyethylene grades were not comparable with marginal drop heights determined in drop tests at -18℃. Pre-damage with 55% nitric acid for 21 days at 40℃ 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℃ 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℃.