Anja Geburtig

Polypropylene Numerical Photoageing Simulation by Dose–Response Functions with Respect to Irradiation and Temperature: ViPQuali Project

The aim of the joint project ViPQuali (Virtual Product Qualification) was to describe a component’s ageing behaviour in a given environment, by numerical simulation.

Combined impact of UV radiation and nitric acid on HDPE containers during outdoor exposure

Abstract Unpigmented HDPE jerrycans filled with nitric acid (55 wt.-%) and water respectively had been exposed to outdoor conditions for one Berlin summer season. As both liquids underwent equal temperature progression, exposure effects of UV radiation and nitric acid as well as of the combination of both can be separated and compared. On the basis of various property changes after these exposures, synergistic action is evaluated and compared to a damaged Intermediate Bulk Container (IBC) from a transport accident. It is found that carbonyl formation accompanies lightness increase in color measurement due to microcracking and with a worsening in mechanical behavior, all of them showing the synergistic effects of UV and nitric acid exposure. By contrast, embedding nitrogen compounds accompanies yellowing of the material but cannot be correlated to oxidation. The reason for intensified damaging is the decomposition of the 55-percent nitric acid and the formation of nitrogen oxides even at ambient temperatures, caused by UV radiation. Thus, damaging effects become similar to those caused by fuming nitric acid exposure at temperatures above 60 °C, resulting in strong oxidative degradation of the polyethylene. By contrast, exclusive exposure to the 55 wt.-% nitric acid at 40 °C does not cause any failure. It can therefore be assumed that the damaged IBC too had been exposed to both UV radiation and nitric acid, probably outdoors.

Chemiluminescence Detection: Principles, Chances and Limitations for the Shortening of Weathering Tests

Improvements in the stabilization of polymeric materials mean that the duration of weathering tests increases. At the same time, however, an increasing number of new developments in ever-shorter development cycles brings about greater demands to shorten the test duration. Apart from accelerating the degradation rate by enhancing exposure parameters, another approach to increasing the test throughput consists in using more sensitive means of detecting degradation effects in earlier stages of the degradation process. The degradation process begins on a molecular level before it starts to spread over higher proportions of the polymer. The effect of degradation on the material builds up until macroscopic properties begin to change, either showing an abrupt threshold behavior or a more gradual response to increasing degradation on a molecular level. From a theoretical point of view, a detection of the earlier stages of the degradation process can be expected by switching from the established, more macroscopic properties in the evaluation of effects to more microscopic ones. While both physical processes and chemical reactions contribute to the degradation of materials, chemical reactions usually are more dominant since their effects tend to be irreversible. Within these chemical reactions, oxidation reactions with oxygen usually are of Chapter 21