Working-life effects on the properties of plastic thermopipes

Mechanical properties and morphological studies of polypropylene thermopipe s manufactured in Jordan and usually used in heating system networks, have been investigated. Samples were chosen to represent new and different worki ng periods (1,3.5 and 6y). The flow resistance of water inside the pipes sh owed a slight decrease in the first year followed by an increase after the second year of use. A decrease in resistance was observed with increasing w orking temperature and Reynold's number. The stress-strain tests exhibit pr operty changes towards brittleness and glassy behaviour, observed after 6y working service. Evidence of deformation was seen by scanning electron micr oscopy (SEM). Deterioration and cracks on the internal surfaces of aged the rmopipes were also noticed. (C) 1998 Kluwer Academic Publishers.