Efficiency of maleic anhydride-modified polystyrene/natural rubber blends as sand aggregate binder

In this work natural rubber (NR) was blended with polystyrene (PS) at various weight ratio: 10:0, 9:1, 8:2, 7:3, 6:4, 5:5 and modified using maleic anhydride (MA: at constant concentration of 7 php, per hundred polymer), and sand aggregate binder, using reflux technique in toluene solution. After solvent evaporation and drying under vauum at 60°C to constant weight, the mixtures were compression moulded to form filmt specimens based on ASTM D638-4. Mechanical testing of the film specimens at optimum condition showed tensile strength of 12.81 MPa, when used weight ratio of 6:4, due to grafting of MA in PS/NR matrix. This was supported by FTIR analysis of the specimen after exhaustive washing in acetone-methanol solvent, which showed absorption peak of maleic carbonyl (>C=O) group at 1710 cm-1. Efficiency of the PS/NR-grafted MA (PS/NR-g-MA) as binder for sand aggregate was estimated by mixing of the binder matrix with sand aggregate using mechanical stirrer in toluene at various weight ratio (3:7, 4:6, 5:5, and 6:4). The mixtures were then compression moulded to 3-point bending test specimens according to ASTM D790-2, and then drying under vacuum at constant temperature 60°C. It was found that at optimum composition (weight ratio of matrix to aggregate: 3:7), in which modulus of elasticity (MoE) was 15895.9 MPa and modulus of rupture (MoR) of 19.85 MPa. This was due to improved adhesion of MA-grafted PS/NR matrix on the sand aggregate surface. Thermal analysis of the optimum specimen (PS/NR-g-MA/Sand) showed no substantial difference on decomposition temperature (465°C), when compared to that of matrix without sand aggregate (PS/NR-g-MA).