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In this investigation, MgO was employed as a secondary cure activator to decrease the rubber curing temperature. To study the curing kinetics at various temperatures, the moving die rheometer (MDR) measurement technique was utilized, and Coran kinetic models of accelerated sulfur vulcanization were adopted. Results from the curing studies revealed that the inclusion of MgO, along with ZnO as the primary cure activator in the traditional vulcanization system, substantially reduced the optimal curing time. The diminished scorch safety time indicated that MgO accelerated the decomposition of accelerator and sulfur, leading to the rapid formation of zinc-based active sulfurating compounds. These compounds contributed to an improved vulcanization rate with lower activation energies. Even when used as the sole cure activator, MgO exhibited higher activation energies for crosslinking but achieved a reduced optimum cure time due to the accelerated decomposition of curatives, resulting in swift formation of final cross-links. A small quantity of 1 phr (per hundred grams of rubber) MgO in the conventional vulcanization system effectively lowered the vulcanization temperature to the boiling point of water, accompanied by an increased vulcanization rate and reduced activation energies of vulcanization reactions. This low-temperature vulcanization approach opens possibilities for critical structures previously challenging to vulcanize through simple molding processes, ushering in a new era in rubber vulcanization. [ABSTRACT FROM AUTHOR]

Stretchable devices and magneto-rheological elastomers (MREs) are together studied in the present work. The device based on composites generates an impressive ~ 8.5 V, and the composites based on iron oxide (Fe2O3) act as a catalyst for magneto-sensitive behavior. The composites were prepared by solution mixing of room-temperature vulcanized silicone rubber (RTV-SR), multi-wall carbon nanotube (MWCNTs), Fe2O3, molybdenum disulfide (MoS2), and their hybrid. From the experimental results, the hybrids were exhibiting a synergistic effect in properties and MWCNT at as low as 2 per hundred parts of rubber (phr) shows the robust increase in properties of the composites. The higher properties of MWCNT were proposed due to its high aspect ratio of 65, tube shape morphology which is easy to disperse, and higher cross-link density in the composites. This work provides insight to readers on a way to obtain robust properties of composite that are good for high-performance applications in MREs and remarkable piezo-electric energy harvesting. [ABSTRACT FROM AUTHOR]

In present work, magneto-rheological elastomers (MREs) based on iron oxide (Fe2O3), carbon black (CB) and their hybrid were prepared using room temperature vulcanized silicone rubber (RTV-SR) as host matrix. The rubber composites based MREs were prepared by solution mixing technique. The tests show that the mechanical performance tunes with presence and absence of magnetic field. The mechanical properties such as compressive modulus, tensile strength and fracture strain were higher for hybrid composites than CB or Fe2O3. It was also found that Fe2O3 based MREs specimen shows high magnetic response and stress relaxation than hybrid composites which shows higher mechanical properties. The multi-hysteresis measurement shows that hybrid with higher reinforcing properties exhibit higher heat build-up losses which are a demerit. These demerits can be overcome by improving stress transfer in composite which can be achieved by enhancing interfacial interaction in composite and will be performed in our future work. [ABSTRACT FROM AUTHOR]

Rubber composites deliver unsatisfactory mechanical performance if the rubber matrices, such as natural rubber, lack appropriate dispersion of fillers such as silica. This study explored the dispersion and reinforcement performance of binary fillers in natural rubber. Graphite powder was used as a solid lubricating silica filler in the rubber matrix, and shear force was applied using a conventional two-roll mixing mill. The curing, mechanical, and morphological properties were studied to evaluate the mechanism of binary filler dispersion in the rubber matrix. Binary fillers comprising silica and graphite offered better mutual dispersion, which was observed by scanning electron microscopy and mechanical testing and confirmed by atomic force microscopy. Better filler dispersion in natural rubber improved the mechanical and age resistance properties. The modulus at 100% strain and stress at break of unfilled rubber were increased by nearly 110% and 15%, respectively, when 20 phr (per hundred gram of rubber) of binary filler in a 1:1 weight ratio was used, and the composite exhibited better aging resistance and mechanical properties, compared to those of composites with single-filler systems, which may be attributable to the excellent filler dispersion in the rubber matrix. [ABSTRACT FROM AUTHOR]

In this study, the synergistic activities of the novel bis -(N-phenyl piperazino) thiuram disulfide (PPTD) and bis -(N-ethyl piperazino) thiuram disulfide (EPTD) with N-Cyclohexyl-2-benzothiazole sulfenamide (CBS) in the vulcanization of natural rubber was investigated. A comparison was made between the safe TDs/CBS systems and unsafe TMTD/CBS combinations in terms of their synergisms on curing and tensile mechanical properties. It was found that novel TDs have synergistic activity very effectively with CBS. The results indicated that EPTD/CBS has better scorch safety, cure rate index and mechanical properties compared to that of the unsafe TMTD during the vulcanization of rubber. Moreover, alkyl, instead of aryl substitution, on piperazine can enhance the reactivity of the synthesized thiuram disulfide. At 6:3 mM ratio of EPTD to CBS could be an effective accelerators system to replace the unsafe TMTD from the vulcanization of rubber with similar curing time, improved scorch safety, and better mechanical properties. [ABSTRACT FROM AUTHOR]