CHEMICAL AGING EFFECTS ON THE PHYSIO-MECHANICAL PROPERTIES OF POLYESTER AND POLYPROPYLENE GEOTEXTILES

The influence of groundwater chemistry on the durability of geotextile s is important for the design of municipal and hazardous waste landfil ls, geotextile reinforcement of slopes and subgrades, and earth retent ion systems. A series of tests are described in this paper, which expl ore the effects of various pH and saline environments on geotextiles, thus contributing to an improved understanding of durability as a basi s for design. Accelerated aging was performed on polyester and polypro pylene geotextiles at room temperature and temperatures elevated to 95 -degrees-C for six months in saline (pH approximately 8), strong alkal ine (pH 10) and acidic (pH 3) media. Property changes as a result of a ging were studied using tensile testing, differential scanning calorim etry (DSC), thermogravimetric analysis (TGA) and intrinsic-viscosity ( I.V.) measurements. Scanning electron microscopy (SEM) was employed to study changes in the surface topography of the fibers upon aging. An Arrhenius model was used to extrapolate results of this short term stu dy to the actual lifetime of the geotextiles. Results indicate that po lyester undergoes hydrolytic degradation under both acidic and alkalin e conditions at and above the glass transition temperature, with the d egradation being more severe under alkaline conditions. The polypropyl ene geotextile, on the other hand, was relatively inert to the pH cond itions and showed no changes in strength. An increase in crystallinity in the initial period of aging was observed for both polyester and po lypropylene. In polyester, this was due to preferential attack on the amorphous regions whereas in polypropylene this may be due to nucleati on growth and lamellar thickening.