Temperature dependent amphoteric behavior of Bis[3-(triethoxysilyl)propyl]tetrasulfide towards recycling of waste rubber: A triboelectric investigation

Here, we have examine the efficacy of bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69) for physic-chemical recycling of waste rubber tyre (WRT) at two different operating temperatures (i.e., 170 °C and 190 °C). The reclaimed rubbers (RR) have been used to fabricate devices similar to the single electrode triboelectric nanogenerator (SETNG) to realize its future applicability. Sol content, crosslink density, Moony viscosity, and rheology of the RR samples have been investigated to understand the effect of operating temperatures on the reclamation (alias regeneration) process. Although very low content of Si69 (i.e., 1g) reclaims the WRT at both the temperatures, with increasing the concentration (i.e., ≥ 3g), it shows coupling behavior (i.e., re-vulcanization) at 190 °C and reclaiming behavior (i.e., de-vulcanization) at 170 °C. Hot-pressing at 170 °C and 190 °C reproduced the similar observations. SETNG made of RR at 170 °C produced more output voltage than that of the 190 °C, and exhibits distinct tactile sensation towards different objects viz., human finger, latex rubber glove, cotton glove and PTFE sheet. The tactile sensing capability is further visualized by exploiting the principal component analysis (PCA). This work represents a low-cost, low-temperature, time-resolved way for regeneration of eco-hazard waste rubber and its future applicability towards development of tactile sensing materials, energy harvester, etc. Also, the response of TNG can be utilized to know the degree of regeneration.