Synthesis and Characterization of A Novel Macromolecular Hindered Phenol Antioxidant and Its Thermo-Oxidative Aging Resistance for Natural Rubber

Abstract

A novel macromolecular hindered phenol antioxidant with high antioxidative efficiency, polyhydroxylated polybutadiene (PHPB)-bound 2, 2′-thiobis (4-methyl-6-tert-butylphenol) (PHPB-b-TPH), was prepared by binding 2, 2′-thiobis (4-methyl-6-tert-butylphenol) (TPH) onto PHPB with isophorone diisocyanate (IPDI), using dibutyltin dilaurate (DBTDL) as catalyst, via a two-step nucleophilic addition reaction. The PHPB was first synthesized from hydroxyl-terminated polybutadiene (HTPB) and 2-mercaptoethanol via a thiol-ene click reaction. The PHPB-b-TPH was characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (¹H-NMR), gel permeation chromatography (GPC), and thermal gravimetric analysis (TGA). The thermo-oxidative aging resistance of natural rubber (NR) with PHPB-b-TPH was evaluated by an accelerated thermal aging test and the oxidation induction time (OIT). The results showed that the −OH groups of PHPB first reacted with highly active secondary −NCO groups of IPDI at 35°C to form the adduct PHPB-NCO, and the PHPB-b-TPH was successfully obtained by one of the phenolic −OH in TPH reacting with the primary −NCO groups of PHPB-NCO at 70°C. The PHPB-b-TPH had better thermal stability and thermo-oxidative aging resistance for NR than TPH.

Keywords:

• 2
• 2′-Thiobis (4-methyl-6-tert-butylphenol)
• 2-Mercaptoethanol
• hindered phenol
• hydroxyl-terminated polybutadiene
• macromolecular antioxidant
• thiol-ene click reaction