D. Dimitrova et al., Durability of polypropylene under stress: The effect of draw ratio and molecular orientation, POLYM SCI B, 43(3-4), 2001, pp. 101-104
Durability of oriented PP films at 20-110 degreesC was studied as a functio
n of tensile stress, and comparison with the data obtained for the other am
orphous-crystalline polymer films and fibers was performed. As was shown, t
here is almost a single correlational dependence between the structural coe
fficient gamma in the Zhurkov durability equation and the draw ratio lambda
(gamma = gamma (0) + C/lambda). The activation energy of fracture U-0 was
found to be constant and independent of the polymer draw ratio. The data ob
tained for a modified PP suggest that the addition of CaCO3, TiO2, and a pl
asticizing agent exerts no effect on U-0, that is, on the strength of chemi
cal C-C bonds but has an effect on the coefficient gamma. As a result of th
e latter trend, the durability of films increases by an order of magnitude.