Oxygen uptake by isotactic polypropylene of different morphological structure

Abstract

Oxygen uptake by isotactic polypropylene was studied at temperatures below melting point, on samples of various degrees of crystallinity and spherulite size. Diffusion coefficients and activation energy of diffusion were calculated. It is suggested that the dependence of the rate of oxygen uptake on the morphological structure of polymer samples can result from different values of the interspherulitic amorphous phase fraction, which is more easily accessible to oxygen than the interlamellar fraction.

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

“…On the contrary, it has also been suggested that high crystallinity leads to the formation of more taut molecules, which preferentially become sites of chain breakage during photodegradation due to the overloading of the amorphous regions. 11 As for the crystal size, some studies have found that iPP exhibits higher resistance to photodegradation with increasing crystal size, which is related to the inhibition of oxygen diffusion, 12,13 as well as the reduction of crystal interfaces and chromophores. 14 Similarly, it has also been reported that the photodegradation stability increases with decreasing the crystal size.…”

Diffusion of antioxidants in sheets and plates of isotactic polypropylene measured by isothermal differential-thermal-analysis

“…shows that the diffusion coefficient of iPP-sheets is 4 times higher than the diffusion coefficient of iPP-plates at 120 ~ The differences are caused by processing -extrusion and compression-moldingbecause both materials, the film strips and the plates, are of the same grade of iPP-powder.Moisan [243 and Mucha[25] have studied the influence of the morphological structure to diffusion processes. Both have measured that diffusion coefficients decrease with the degree of cristallinity.The degrees Of cristallinity of the iPP-sheets and iPP-plates are 41% respectively 42 % -both determined by dynamic DTA.This minimal difference of 1% cristallinity cannot be the reason for such a great differen@e of diffusion coefficients.…”