The effect of sodium bicarbonate ratio for the mechanical properties of underarm pads rubber for crutches

Abstract

Research on the effect of the ratio of sodium bicarbonate on the mechanical properties of underarm crutch pads from natural rubber SIR-20 has been carried out. The ratio of sodium bicarbonate used was 1.00 phr; 1.50 phr; 2.00 phr; and 2.50 phr. The rubber compound for underarm crutch pads was made by the compounding process using an open rubber mixing mill and vulcanization at a temperature of 120 ºC for 11 minutes. The best formula for curing characteristic rheometer test results at a temperature of 150 ºC was URC-04 with Smax= 4.95 kg/cm, Smin = 0.44 kg/cm, DS = 4.51 kg/cm, t90 = 6.57 min and ts2 = 4.13 min. The mechanical test result showed the hardness test before aging and after aging of 31 Shore A, and 32 shore A, tear strength of 8.50 kN/m, elongation at the break before aging and after aging of 300%. The results of the identification of functional groups by FTIR for infrared absorption in each sample generally showed the same pattern with one another. SEM analysis result showed the distribution of materials and the formation of pores by sodium bicarbonate was not evenly distributed with an average diameter of 5 microns.