Study of the Effect of Natural Rubber-graft-maleic Anhydride (NR-g-MA) on the Compatibility of NR-NBR Blends Using the Ultrasonic Technique

The grafted copolymer of natural rubber (NR) and maleic anhydride (MA) was synthesized in a solution state by using ultraviolet radiation. The NR-g-MA was characterized using infrared (IR) technique. The prepared NR-g-MA was added to a 50/50 blend of NR and acrylonitrile-butadiene copolymer (NBR) as a compatibilizer. The effect of compatibilizer (NR-g-MA) concentrations in the range of 2, 4, 5, 6, 8, and 10 wt.% on the ultrasonic velocity, attenuation coefficient, and ultrasonic viscosity was studied in order to study the compatibility of the 50NR-50NBR blend. Ultrasound pulse echo method was used to measure both the ultrasound velocities and attenuation coefficient at a frequency of 2 MHz. Testing for elastic constant, Poisson's ratio, cross-link density, and microhardness was carried out in different percentages of the blend components to study the degree of the compatibility of the blend. The structure of the blend system was established by differential scanning calorimetry. The addition of NR-g-MA to the blend showed improvement of compatibility in certain concentration ranges and deterioration of compatibility in other ranges.