Study On The Anti-aging Performance Of Polypropylene Fibers For Geotextile

Aging of geotextile attracted a great deal of attention in recent years, because it is very important to the stability of the whole work, and geotextile are used widely as reforcing medium in structures. Especially, the prediction of geotextile's aging-time has become one of the focuses nowadays. However, most of the studies are on plastics, and few are on fibers.In this paper, systematic investigations on the aging-time of polypropylene fibers at different temperatures have been made. This research has laid particular emphasis on how to build up the equation of geotextile's aging-time, which was based on Arrhenius equation (K=A e-E/RT). By means of oven accelerated aging test, the experiments were carried out at 120℃, 125℃, 130℃ and 135℃, respectively. Then the lifetime of the fibers at normal temperature could be calculated according tothe equation. where τ f is the final durability period; K is compositive multiplication coefficient; τ r is reference durability period; τr is reference temperature, 150℃; τi is using temperature (K); Kj is multiplication coefficient at τi; Fi is time fraction of ℃i, Fi=1.Moreover, the effects of changing critical value on the equation were elucidated. Furthermore, the effect of soil's acidity (pH=5) and basicity (pH=9), pure water and copper ion in the water on the aging-time was discussed.The results showed that acid and alkali made the fiber's lifetime decrease about 13% and water make the fiber's lifetime decrease about 20%, while copper ion shorten the aging-time of the fiber more than 54%. Acid, alkali, metal ion wouldshorten the lifetime of PP fiber, and the effect of metal ion is the biggest, the effect of water is the second, acid and alkali is the smallest. Under the pressure the aging rate of PP geotextile would be accelerated.This study also indicated that fiber grade anti-aging PP chip could be spun at conventional temperature; plastic and flat fiber grade would be spun at high temperature. However, high spun temperature would make the antiager consume and decompose, which will shorten the geotextile's lifetime. Therefore, the antiager and the spinnability of resin were very important.As there are different effect factors in different environment, experiment should be done based on particular natural conditions.