Physico-Mechanical, Solubility and Thermodynamic Studies of Natural Rubber – Neoprene Blends

ABSTRACT In this study NR and CR were blended as follows. NR/CR (100/0), NR/CR (80/20), NR/CR (60/40), NR/CR (40/60), NR/CR (20/80) and NR/CR (0/100). The samples were vulcanized before subjecting them to physic-mechanical, swelling and thermodynamic studies. The results of the physico-mechanical tests carried out on the vulcanizates revealed modulus in the range of 3.22MPa to 1.79 MPa from absolute neoprene composition to absolute natural rubber composition, hardness in the range of 16.8 to 14.3 (Shore A) from absolute CR to absolute NR and ultimate tensile strength in the range of 4.17 to 2.83 MPa from absolute CR to absolute NR. The results of swelling revealed that the blends with higher neoprene content showed better resistance to petrol, kerosene and hexane compared to blends with lower neoprene contents. The order of increasing permeability of the solvents regardless of sample composition was; kerosene > hexane > petrol. The results of the thermodynamic studies of three selected blends (samples B, C and F) showed the sensitivity of reaction towards temperature as higher mass uptake values of the blends were recorded as temperature was increased in the order 30 0C, 50 0C and 70 0C. The activation energy of the swelling process was in reverse order of the permeability of the solvents. The solvent with the least permeability (petrol) had the highest activation energies in all the selected blends. The order of increasing activation energies of the solvents in the three blends was; Petrol> hexane> kerosene. The studies showed that solvent resistance of NR can be enhanced by blending with CR in appropriate ratio. Keywords: rubber, vulcanizate, vulcanization, compounding, activation energy, thermodynamics.