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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]

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]

Per-2,3-acetyl-β-cyclodextrin is first synthesized by selective modification and used as core molecule for preparing a star-shaped macromolecular antioxidant (β-CD-DBHMP) via a two-step method. β-CD-DBHMP is characterized by 1H-NMR, MALDI-TOF MS, and TGA. The performance of β-CD-DBHMP as antioxidant for natural rubber is determined by OIT and accelerated thermal aging test, and its extraction resistance is also investigated. The results show that β-CD-DBHMP with a Mn of 4.03 × 103 g · mol−1 is successfully obtained, and it possesses high thermal stability with an initial weight loss temperature of 290 °C. Moreover, β-CD-DBHMP is superior to DBHMP for the stabilization of NR against thermal oxidation, and exhibits better extraction resistance. Its possible antioxidative mechanism is also discussed. [ABSTRACT FROM AUTHOR]

A star-shaped macromolecular antioxidant (β-CD-DBHMP) was synthesized via a two-step method by binding 2,6-di-tert-butyl-4-hydroxy methyl phenol (DBHMP) onto per-2,3-acetyl-β-cyclodextrin (β-CD-core) using isophorone diisocyanate (IPDI) as linkage. FT-IR, 1 H –NMR, MALDI-TOF MS and GPC results confirmed the star-shaped structure of β-CD-DBHMP. Accelerated thermal aging test and water extraction test indicated β-CD-DBHMP could protect natural rubber (NR) against thermal oxidation and also exhibit good extraction resistance in NR matrix. [ABSTRACT FROM AUTHOR]