Synthesis of Novel Benzoxazines Containing Sulfur and Their Application in Rubber Compounds

Abstract

This work reports the synthesis and successful use of novel benzoxazines as reinforcing resins in polyisoprene rubber compounds. For this purpose, three new dibenzoxazines containing one (4DTP-fa) or two heteroatoms of sulfur (3DPDS-fa and 4DPDS-fa) were synthesized following a Mannich condensation reaction. The structural features of each benzoxazine precursor were characterized by 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and Raman. The new precursors showed well suited reactivity as characterized by differential scanning calorimetry (DSC) and rheology and were incorporated in rubber compounds. After the mixing, the curing profiles, morphologies and mechanical properties of the materials were tested. These results show that the structural feature of each isomer was significantly affecting its behavior during the curing of the rubber compounds. Among the tested benzoxazines, 3DPDS-fa exhibited the best ability to reinforce the rubber compound even compared to common phenolic resin. These results prove the feasibility to reinforce rubber compounds with benzoxazine resins as a possible alternative to replace conventional phenolic resins. This paper provides the first guide to use benzoxazines as reinforcing resins for rubber applications, based on their curing kinetics.

Self-Polymerization Promoting Monomers: In Situ Transformation of Disulfide-Linked Benzoxazines into the Thiazolidine Structure

“…The filtrate was dried over anhydrous sodium sulfate and filtered before drying under vacuum to obtain cystamine (7.9 g; 61% yield) as a pale-yellow oily liquid. FTIR−ATR (diamond crystal/ν cm −1 ): 3242−2392, 1599, 1591, 1458, 1402, 1242, 1141, 1094, 1064, 925, 811, 768, 732, and 640; 1 H NMR (400 MHz, CDCl 3 , δ ppm): 2.5 (t, 2H, S−CH 2 ) and 2.8 (t, 2H, N−CH 2 ); 13 C NMR (100 MHz, CDCl 3 , δ ppm): 40.2 and 42.1. 1 H and 13 C NMR images are provided in Figure S1.…”

“…FTIR−ATR (diamond crystal/ν cm −1 ): 3242−2392, 1599, 1591, 1458, 1402, 1242, 1141, 1094, 1064, 925, 811, 768, 732, and 640; 1 H NMR (400 MHz, CDCl 3 , δ ppm): 2.5 (t, 2H, S−CH 2 ) and 2.8 (t, 2H, N−CH 2 ); 13 C NMR (100 MHz, CDCl 3 , δ ppm): 40.2 and 42.1. 1 H and 13 C NMR images are provided in Figure S1.…”

“…Yield: 85%. FTIR−ATR (diamond crystal/ν cm 13 C, and HSQC NMR images are provided in Figures S2 and S3.…”

“…The structure of monomer PH-cys Me (3) was confirmed by NMR spectroscopy. Figure S4a,b shows 1 H and 13 C NMR spectra with characteristic oxazine signals at 4.9 and 4.0 ppm and 82.6 and 51.0 ppm due to O−CH 2 −N and N−CH 2 −Ar, respectively.…”

“…Ring-opening polymerization (ROP) of the oxazine ring results in the formation of polybenzoxazines (PBzs). The past decade has witnessed significant progress in the field of PBzs and their upcoming role in various applications by structural engineering at a molecular level. , Incorporation of an additional reactive functionality − in the benzoxazine monomer dictates structural interactions and is known to modify the properties of the polymer. These functionalities can either react with themselves or with the oxazine ring during polymerization, thus tailoring the rigidity of the PBz network.…”