Tear strength theory of semicrystalline polymers

A theroretical model describing how the tear strenght of semicrystalline polymers depends upon the interaction of the crystalline and amorphous phases is presented. It is based upon the “freevolume“ theory and a “Hooke's law -lattice energy” treatment. The strength T_M is hypothesized to be partitioned between the crystalline Q_c and amorphous Q_a phases. Therefore T_M∝? Q_c. Q_a, T_M = T_o.Q_c.Q_a, where Q_c = NKTE/bY² and e^?v/vf =G/G_oτ. Proof of this theory is obtained by measuring the oxygen transmission rates of 11 polyethylene film samples varying in tear strenght. Good agreement exists between T_M (experimental) and T_M (theroetical) for 9 of the polyethylene samples. The other 2 Samples differ from the theory by factor of 2. One explantion of this departure is the τ varies from unity.