The phenolic cured butyl rubber reclamation using different de-crosslinking agents

Abstract

The cured rubber-made bladder used for curing the green tire because, it is thermally stable, and has low gas permeability. The bladder is made with the cured butyl rubber as a base rubber under a phenolic curing system. To save the resources and also, the environmental protection, it should be de-crosslink to gum rubber. A commercial source waste bladder rubber compounded with different de-crosslinking agents, including TMTD, DPDS, DCBS, MBTS, MBT, and TBBS. To do de-crosslinking, the prepared compounds were heated in a laboratory heating oven at different temperatures. The de-crosslinking parameters including the sol fraction and de-crosslinking percent measured using traditional rubber swollen tests. The Fourier transform infrared spectroscopy (FTIR) graphs showed the existence of the phenolic resin in the structure of waste bladder butyl rubber powder. Efficient de-crosslinking was observed for all studied de-crosslinking agents. It evidenced by the scanning electron microscope micrographs and also, the measured crosslink densities of the reclaimed rubbers. The highest and the lowest de-crosslinking percents belonged to the compounds with 4 phr DPDS in recipe at 220 [Formula: see text] and 4 phr DCBS at 180 [Formula: see text], respectively. Based on the obtained de-crosslinking parameters, the DPDS was selected as a suitable de-crosslinking agent for used waste rubber. In accordance with Horikx analysis, the oven heating broke down the crosslinks and rubber main chains simultaneously. Increasing the oven temperature had a positive effect on de-crosslinking process with similar effects on the crosslink and main chain break down.