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Waste rubber is a polymeric material containing 50% of rubber and is generally referred to as waste tyre rubber. The main purpose of this research is to study ultrasonic devulcanisation of waste rubber utilising deep eutectic solvent (DES) of ZnCl2:Urea by improving process parameters such as sonication time, reaction temperature and rubber: DES mass ratio by effectively cleaving cross-link sulphur bonds. DES was created and prepared by mixing ZnCl2 with urea at 2:7 and 1:4 molar ratios respectively. Physicochemical properties of the prepared DES was measured using DSC, KFT and TGA analysis to find the freezing point, moisture content and degradation temperature, whereby their freezing point below 60°C, moisture content lower than 3.0 wt.% and 200°C degradation temperature average. Rubber to DES mass ratio was varied at 1:20, 1:30 and 1:40 and sonicated for 15 minutes inside ultrasonic water-bath. Samples were placed onto hot plate whereby heating temperature was varied at room temperature, 130°C, 150°C, and 180°C for 15 minutes. Samples were filtered, washed with distilled water and dried in oven for 24 hours. Once dried, samples were taken for analysis using TGA, EDX, FESEM, FTIR and Gel content. Under TGA analysis, most samples have an average degradation temperature of 200°C, hence justifying a successful devulcanisation. EDX analysis shows two occurrences during devulcanisation process which is bond reformation and cleavage. Furthermore, it is determined that heating temperature of 130°C is an important parameter as it is the optimum temperature for ZnCl2:Urea. Under FTIR analysis, it shows that disulphide bond, S-S is the only bond that is being broken while the rest still remains the same. Gel content analysis showed that samples have a lower soluble fraction after devulcanisation process. Finally, FESEM proves that at 130°C and 15 minutes is the optimum temperature and time which is illustrated by the smooth surface at that particular point.

Background: Deep eutectic solvents (DESs) are new types of tunable solvents that have attracted a large scientific community due to their versatile applications and attractive physical properties. Ammonium‐based solvents are widely used in desulfurization processes, but they are toxic and expensive. Thus, to replace the conventional ammonium‐based solvents, this work aims to synthesize novel ammonium–ethylene glycol (EG)‐based ternary DESs (TDESs). The thermophysical properties, such as viscosity, density, acidity, stability, degradation point, melting point, conductivity, refractivity and miscibility, were measured in this study. Results: The TDESs were prepared using varying molar ratios ranging from 1:3 to 1:5 by combining a hydrogen bond donor (EG) with ZnCl2 and three ammonium‐based hydrogen bond acceptors, namely ethylammonium chloride, diethylammonium chloride and diethylethanolammonium chloride. It was found that most properties are significantly superior to those of the constituent components of the TDESs. Arrhenius and linear equation fittings with respect to temperatures ranging from 20 to 100 °C predict R2 values close to unity. The viscosity, pH and density decrease while electrical conductivity increases with increasing temperature. Conclusion: Such interesting observations are mainly caused by the particles' excitation phenomena that increase their kinetic energy and volume. Furthermore, the lower melting point of TDESs compared to the constituent components is attributed to the charge delocalization through hydrogen bonding between donor and acceptor molecules. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]