Biobased Polybenzoxazine Containing Acetal Structures: Adhesion, Rebonding, and Degradation Properties

A degradable biobased polybenzoxazine with strong adhesion property was fabricated through incorporating of acetal structures. A main-chain type benzoxazine precursor (DVEA-dad) was prepared from a diacetal derived from vanillin and erythritol, 1, 10-diaminodecane and paraformaldehyde. The structure and curing behavior of DVEA-dad were investigated in detail. The cured polybenzoxazine (PDVEA-dad) possessed a glass transition temperature (T_g) of 154 °C according to the result of dynamic mechanical analysis (DMA). When utilized as adhesives for metal sheets, PDVEA-dad exhibited high lap shear strength up to 9.4 ± 0.9 MPa for steel sheets. The dynamic exchange of acetal bonds enabled PDVEA-dad to have rebonding and reprocessing properties. Additionally, the results of chemical degradation experiments revealed that PDVEA-dad could be degraded completely under acidic conditions through the cleavage of acetal bonds. This work provided an effective solution to promote the development of biobased polybenzoxazine adhesives.