Aging effects of polypropylene used in heating systems

The ageing effects of polypropylene targets used in heating systems were investigated using the nuclear reaction analysis (NRA) technique. Deuterium beams of energies 900, 1200 and 1500 keV, supplied from the University of Jordan Van de Graaff accelerator, were employed. Different working times between 1 and 6 years were investigated in addition to a new fresh sample which was considered as standard. The reactions resulting from 12C(d,p)13C, 16O(d,p1)17O and 14N(d,α1)12C were monitored. The oxygen and nitrogen concentrations data reveal similar behaviour for both elements. The initial concentration of both quantities resulting from fusion, processing and storage times decreases and then gradually increases to reach higher levels than those initially, as the working time is increased. A model, based on mass transfer of air-oxygen and nitrogen and solubility of polypropylene to both elements, was proposed to explain our observation. The uptake of these light impurities and their presence at high concentration levels in the thermopipes material, in addition to microstructural effects, are responsible for the degradation of many of its observed properties. The main effect was demonstrated by the influence of several parameters on strength and embrittlement. (Author)