Assessment of Recovered Carbon Black Obtained by Waste Tires Steam Water Thermolysis: An Industrial Application

Nearly 300 Millions of waste tires have to be managed in Europe. The main industrial ways to treat this kind of waste are incineration for energetic valorization and tires milling in chips or granulates for material valorization in construction industry. Steam water thermolysis (SWT) of tires, a hybrid of pyrolysis and solvolysis, is a good alternative to valorize waste tires. Recovered carbon black (rCB), which can be reintroduced in rubber industry as reinforcing filler (circular economy concept), is a more economical added value material than shredded tires. Physical and chemical characterizations on SWT-rCB were performed following ASTM analytical standards. A comparison between furnace carbon black (N330) and rCB from pyrolysis (commercial products) was carried out. Oil Absorption Number (ASTM D2414) and nitrogen adsorption (ASTM D6556) measurements demonstrate that rCBs structure and specific surface area are comparable to a furnace carbon black N330. According to data issued from ASTM standards, the behavior of rCBs reinforcement in rubbers is then expected to be equivalent to a N330 carbon black. Rubber compounds were produced with a homemade formula and mechanical characterizations were carried out in order to assess reinforcement properties of SWT-rCB. Comparisons in terms of mechanical properties have been established between rubbers reinforced with 100% of SWT-rCB, rubbers reinforced with furnace carbon blacks (N330, N550 and N772), and mixtures of SWT-rCB and furnace carbon blacks. The results clearly show that rCBs reinforcement properties are lower than those of N330 carbon black. However, for a same rubber formula, SWT-rCB filled rubbers properties are close or slightly better than N550 and N772 filled rubbers.