Modeling the Hardness and Mechanical Properties of Moulded Natural Rubber Pad

Abstract

The Shore A hardness, tensile stress at specified elongation (100, 200, and 300%), and compression stress at given strain (20 and 40%) of moulded natural rubber pads were modeled as function of ingredient proportions. Nine ingredients of the rubber pad were chosen as factors and varied at two levels of proportions. A 29-5 fractional factorial design of experiment was utilized during rubber compounding. Results show hardness of rubber pads is significantly increased when proportions of carbon black, tetramethylthiuram disulfide (TMTD), and stearic acid are increased in the formulations; hardness is decreased when process oil, paraffin wax, and antidegradant are increased. The same effect of carbon black, process oil, paraffin wax, and TMTD is observed on tensile properties of rubber pads. Compression properties are improved when carbon black, zinc oxide, and antidegradant are increased; properties are lowered when process oil and paraffin wax are increased. Analysis of variance shows the variation of response with ingredient proportion is significantly linear. The derived empirical models show good agreement with experimental data.