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Macromolecular antioxidant due to its low physical loss, high thermal stability, and good compatibility has been considered to be a promising candidate to inhibit polymer aging. In this study, thermo-oxidative aging resistance and antioxidative mechanism of a macromolecular hindered phenol antioxidant, namely, polyhydroxylated polybutadiene containing thioether binding 2, 2'-thiobis (4-methyl-6-tert-butylphenol) (PHPBT-b-TPH) for natural rubber (NR) vulcanízate was studied in detail by oxidation induction time and accelerated thermal aging tests. The results showed that the antioxidative efficiency of PHPBT-b-TPH was very high. When the amount of PHPBT-b-TPH was only 1 phr, the NR vulcanizate could exhibit excellent thermo-oxidative aging resistance, obviously higher than that of NR vulcanizate with low-molecular-weight antioxidant TPH. After aged at 100°C for 168 h, the retentions of tensile strength and elongation at break of NR vulcanizate with PHPBT-b-TPH were 43.6% and 58.6%, respectively. However, those of NR vulcanizate with TPH were 35.6% and 54.5%. In addition, it was found that both thioether and urethane groups in PHPBT-b-TPH had antioxidative ability and had synergistic effect with hindered phenol. Through our findings, new strategy to design and synthesize the macromolecular antioxidant with multi-antioxidative groups for rubber materials and other polymer materials could be developed. [ABSTRACT FROM AUTHOR]

ABSTRACT Due to low thermal stability, poor migration, and extraction resistances, the antioxidant with low molecular weight is easy to physically lose during processing and long-term service, and its applications are severely restricted. To increase the molecular weight of antioxidant is one of the promising methods to overcome such drawbacks. In this study, the extraction resistance of a macromolecular antioxidant, namely polyhydroxylated polybutadiene containing thioether binding 2,2′-thiobis(4-methyl-6- tert-butylphenol) (PHPBT- b-TPH), was investigated by extraction resistance test and equilibrium swelling experiment. The results exhibited that the PHPBT- b-TPH offered much better extraction resistance in natural rubber (NR) than the low molecular weight antioxidant TPH. In addition, the extraction resistance of hydroxyl-terminated polybutadiene (HTPB), polyethylene glycol (PEG), and polypropylene glycol (PPG) in NR were also compared to study the extraction mechanism of the PHPBT- b-TPH. It was found that the higher molecular weight of PHPBT- b-TPH and the co-vulcanization between PHPBT- b-TPH and NR were the main reasons for the excellent extraction resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44905. [ABSTRACT FROM AUTHOR]

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), andthermal 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. [ABSTRACT FROM PUBLISHER]