Behaviour of Nitrile Rubber-Based Mixtures to Composting Tests

The paper presents the behavior of some samples based on nitrile rubber reinforced with inorganic and organic type of filler, respectively, to composting. The organic filler used was obtained as waste in the leather and footwear industry. Before use, the waste was ground and then functionalized with potassium oleate in order to improve compatibility with the polymer matrix. The samples of rubber mixtures were obtained on a Brabender mixer, the vulcanization agents were added on a laboratory roller, and the vulcanization of the samples was performed in a hydraulic laboratory press, at 165°C, with a pressing force of 300 kN. The aerobic composting test was performed at laboratory scale, using solid, standardized and homogeneous synthetic waste. After a thermophilic incubation period of 42 days (at 58°C), followed by a period of mesophilic incubation (at the room temperature) of 42 of days, a decrease of some physico-mechanical properties was noticed (hardness, 100% modulus, tensile strength), of the gel fraction, and of the crosslinking densities, the largest decrease of these characteristics being observed in the sample with the highest content of organic filler. The results obtained may indicate that the biodegradation of the rubber samples is favored by the organic fillers.