Radiation, thermo-oxidative and storage induced changes in microstructure, crystallinity and dielectric properties of (un)oriented isotactic polypropylene

Effect of microstructure tuning by rapid heat cycle molding on the photodegradation behavior of isotactic polypropylene

“…In contrast, Yoshii et al 21 found that PP containing β ‐nucleating agents exhibited poor radiation stability due to the smaller spherical size and shorter linked molecular chains. Moreover, studies have also reported the promotion and inhibition effects of molecular orientation 6,22 on polymer degradation, which again suggests that the microstructure has an important effect on the photodegradation.…”

“…4 The unstable tertiary hydrogen atoms in iPP molecular chains are prone to occur a series of complex photodegradation under the UV light. 5 This will cause the breakage 4 and cross-linking 6 of molecular chains, which eventually change the microstructure of iPP and lead to deterioration of the surface quality of products. 3,7 Therefore, it is important to investigate the photodegradation mechanism of iPP for slowing down the photodegradation rate and prolonging the service life of its products.…”

“…Since photodegradation occurs first in the amorphous region and iPP with higher crystallinity has lower oxygen diffusion coefficient and segmental mobility, crystallinity plays an inhibitory role on the rate of photodegradation. 6,9 On the other hand, the higher recrystallization probability with increasing crystallinity also plays a suppressive role in the photodegradation. Besides, Liu et al 10 demonstrated that the ability of crystals to scavenge radicals increased with increasing crystallinity.…”

“…At present, both inhibition and promotion effects of crystallinity on the photodegradation rate have been reported. Since photodegradation occurs first in the amorphous region and iPP with higher crystallinity has lower oxygen diffusion coefficient and segmental mobility, crystallinity plays an inhibitory role on the rate of photodegradation 6,9 . On the other hand, the higher recrystallization probability with increasing crystallinity also plays a suppressive role in the photodegradation.…”