CHARACTERIZATION OF POLYPROPYLENE PIPES DURING ACCELERATED AGING IN AIR AND WATER

Commercial polypropylene pipes for water transport were aged in air at 135 degrees C and in water at 95 degrees C for up to 3000 and 4000 h respectively. The protection effect of the antioxidant in the polymer was investigated by measuring the oxidation induction time (OIT) and b y determining the chemical changes in the aged polymer by infrared spe ctrometry (FT-IR). A slight increase of crystallinity, melting tempera ture, crystallite dimensions with aging was observed via FT-IR, small angle light scattering (SALS) and differential scanning calorimetry (D SC). Tensile tests of two different pipes showed dramatic decay of mec hanical properties with the conditioning time in air for the product l ess protected from thermal oxidation.