Combining polybenzoxazines and polybutadienes: Via simultaneous inverse and direct vulcanization for flexible and recyclable thermosets by polysulfide dynamic bonding

In this work, we report a novel approach to combine two structurally diverse polymers, namely polybenzoxazine and polybutadiene by simultaneous inverse and direct vulcanization. The process is based on mixing elemental sulphur, mono-functional benzoxazines and polybutadienes (PB) in various ratios, and heating up to 180 °C. Inverse vulcanization between sulphur atoms and oxazine rings triggered ring-opening polymerization of benzoxazines and vulcanization of PB proceeded concomitantly. Flexible films were cast in Teflon molds by using PB in high amounts in formulations. These films were cut into pieces and subjected to a recycling process at 180 °C for up to 5 cycles through polysulfide dynamic bonding. The extent of recovery of the films was quantified by tensile tests. Spectral characterization and thermal behavior of the films were also investigated before and after the recycling process.