214 M.Rjeb et al Physica A358(2005)212-217 3.Results and discussion TG curves corresponding to the naturally aged PP samples,during 80 days,named NA80(c).and 60 days,named NA60 (b),are shown in Fig.1.as well as the one corresponding to the nonexposed sample,named NE (a).The samples degrade in a single step from 275 to about 425C for the unaged sample,and to about 443C for the samples aged during 60 and 80 days. These curves represent the percentage of mass loss as a function of the tempe one n otices that the material that is more aged degrades all the m rapidly, and thus the end of degradation te mperat ase during the aging th e pe of the corr ng mas n or (Fig.(1) ang poncd e ge of mass loss,the corresponding temperature is a decreasing function Fig.1(2)shows the effect of the artificial aging on the PP sample.The same behavior observed in the case of the natural aging is present in that of the artificial aging(samples named AA60 and AA80 for the artificial aging during 60 and 80 days, respectively). Table I illustrates the diminution of the end of degradation temperatures observed for the two aging types. A comparative study of the influence of the duration of exposition on the degradation and therefore on the type of the PP aging,for the same duration,60 and (a) -40 (b) 60 300 350 400 450 1) 2 Tceofthethm deompPp amp ()andifc Table 1 End of degradation temperatureC of different PP samples:aged during 60,80 days and new sample Reference PP aged naturally PP aged artificially NE 60days 80 days 80 days 452.0 443.8 441.9 435.8 433.83. Results and discussion TG curves corresponding to the naturally aged PP samples, during 80 days, named NA80 (c), and 60 days, named NA60 (b), are shown in Fig. 1, as well as the one corresponding to the nonexposed sample, named NE (a). The samples degrade in a single step from 275 to about 425
C for the unaged sample, and to about 443
C for the samples aged during 60 and 80 days. These curves represent the percentage of mass loss as a function of the temperature; one notices that the materialthat is more aged degrades allthe more rapidly, and thus the end of degradation temperatures decrease during the aging process. Indeed, for the same temperature, the percentage of the corresponding mass loss is an increasing function of duration (Fig. (1)), and conversely, for the same percentage of mass loss, the corresponding temperature is a decreasing function (Fig.1(1)). Fig. 1(2) shows the effect of the artificialaging on the PP sample. The same behavior observed in the case of the naturalaging is present in that of the artificial aging (samples named AA60 and AA80 for the artificial aging during 60 and 80 days, respectively). Table 1 illustrates the diminution of the end of degradation temperatures observed for the two aging types. A comparative study of the influence of the duration of exposition on the degradation and therefore on the type of the PP aging, for the same duration, 60 and ARTICLE IN PRESS 275 300 325 350 375 400 425 450 475 -100 -80 -60 -40 -20 0 Mass loss (TG %) Temperature (˚C) 300 350 400 450 -100 -80 -60 -40 -20 0 (a) (a) (c) (b) (b) (c) Mass loss (TG %) Temperature (˚C) (1) (2) Fig. 1. TG curves of the thermal decomposition of PP: samples aged naturally (1) and artificially, (2) during 80 days, (c) 60 days (b) and new sample (a). Table 1 End of degradation temperature
C of different PP samples: aged during 60, 80 days and new sample Reference PP aged naturally PP aged artificially NE 60 days 80 days 60 days 80 days 452.0 443.8 441.9 435.8 433.8 214 M. Rjeb et al. / Physica A 358 (2005) 212–217