Screening Of The Thermal Endurance Of Spacecraft Materials By Kinetic Modelling
- PDF / 791,138 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 64 Downloads / 203 Views
NN5.1.1
Screening Of The Thermal Endurance Of Spacecraft Materials By Kinetic Modelling M. Moser, S. Heltzel, C.O.A. Semprimoschnig, G. Garcia Martin Materials Physics and Chemistry Section, Materials and Processes Division, ESA/ESTEC, Postbus 299, Noordwijk, The Netherlands ABSTRACT Future science missions of the European Space Agency (ESA) to the inner part of the solar system will require the use of materials at an extreme radiation and temperature environment. A major concern regarding the selection of these materials is the thermal behaviour and the thermal stability. In this paper ways are shown to assess the thermal endurance of polymers by kinetic modelling. Two commonly used kinetic models, the one following the ASTM E 1641 and ASTM E 1877 standards and the other following the Model Free Kinetics (MFK) approach, are presented and compared to each other with the given example of two competing polyimide films, Kapton HN® of DuPont and Upilex S® of Ube Industries1, which were tested within ESA’s critical materials technology program. INTRODUCTION The European Space Agency (ESA) is currently planning missions to the inner part of the solar system. These missions will require materials that withstand an environment in which parameters such as heat input, UV and soft X-ray radiation, e- and p+, can play an important role. A major concern regarding the selection of the materials is the behaviour and the stability of external surfaces that will receive heat inputs above 10 kW/m2. When polymers are exposed to such heat inputs they can lose mass due to evaporation, decomposition and chemical reactions. The thermal stability i.e. mass loss versus temperature and time can be examined by running long-term isothermal Thermo Gravimetric Analyses (TGA) tests [1]. In this paper a faster way to screen the thermal endurance of polymers by running TGA temperature scans followed by kinetic modelling is presented on the given example of two polyimide foils, Kapton HN® from DuPont and Upilex S® from Ube Industries. KINETIC MODELS As mentioned above mass loss occurs due to chemical or physical processes. With a mathematical description of these processes as a function of time and temperature models can be made describing the course the reaction is expected to follow. Thus, the thermal stability of a material at elevated temperatures can be calculated and lifetime predictions can be made. The two models that are presented in the following, the ASTM E 1641 [2] and ASTM E 1877 [3] calculation method and the method of Model Free Kinetics (MFK) [4] [5] are capable of describing these processes and thus allow a lifetime prediction for polymers. Both models are based on at least three TGA runs at different heating rates as shown in Figure 1. 1
Kapton HN ® is a trademark of DuPont, USA and Upilex S ® is a trademark of UBE, Japan.
NN5.1.2
100 90 80
Mass [%]
70 60 50 40 Kapton@1 K/min Kapton@2 K/min Kapton@5 K/min Kapton@10 K/min Upilex@1 K/min Upilex@2 K/min Upilex@5 K/min Upilex@10 K/min
30 20 10 0 200
300
400
500
600
700
80
Data Loading...
