RHEOLOGICAL STUDIES ON TESTING METHODS OF RUBBERLIKE POLYMERS

(PART VI) TEAR RESISTANCE

Abstract

Results of tear tests with the sample specimens of JIS-A (ASTM-B) and-B types (ASTM-C) were studied rheologically by comparing them with these reported in ref. (8) in the text.
The shape of the sample specimen is first approximated for each type to a rectangular ribbon with an appropriate dimension which gives the closest stress-strain relationship to that of the former. The corresponding cut length, C is then assumed for each type of specimen which brings on the same value for thestress concentration coefficient, kγ as that of a rectangular ribbon with a cut. Thus we have
kγ_A-1=mγC_A
kγ_B-1=mγC_B
Here mγ represents the stress eoncentration factor which identical with that defined in ref (8) The tear resistance, (F/t), which is defined both in JIS and ASTM, is further correlated with those quantities above and others, and the following equation is obtained :
(F_B/t_B) / (F_A/t_A) ≅C_A/C_B
The experimental data on several typical rubber vulcanizates agreed well with those obtained from above equations. It was found that the values of C_A andC_Bare both affected little by the material quality but are fairly sensitive on the curvature at the tip.