Threshold tear strength

Threshold Tear Strength of Some Molecular Networks... 

Table I. Threshold Tear Strength T0 of Randomly—linked and Endlinked Elastomers of Varying Mc...

Table II. Effect of Swelling with m-Xylene on the Threshold Tear Strength of PDMS... 

Values of Mc calculated from the small-strain tensile modulus, i.e., using C- + C2 in equation 2 in place of Cj, were, of course, smaller than those obtained from Ci values. However, the general form of the dependence of threshold tear strength upon Mc and the relative values obtained for different polymers at the same Mc were not significantly affected by this alternate procedure for calculating the mean molecular weight of network strands. 

The threshold tear strength of elastomeric molecular networks does not appear to depend strongly, if at all, upon the uniformify of network strand lengths. It is found to be proportional to Mc where Mc is the mean molecular weight of the strands, in accordance with the theory of Lake and Thomas (3). However, it is considerably smaller for Si-0 networks than for C-C networks at equal Mc values. This is attributed to differences in strand length and extensibility. 

At low rates of tearing, about 10 m/s at 7g, the contribution from viscous losses becomes vanishingly small and the tear strength is reduced to the small threshold value, Gq. As the tear rate increases, the tear strength rises, approximately in proportion to until it becomes about 1000 x Go ... 

Far above T, under threshold conditions9 the tear strength depends 1 ... 

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