ABSTRACT Conventional thermosetting phenolic resins are difficult to recycle after curing. To overcome this limitation, straight‐chain phenolic resins containing aldehyde groups (MPR) are synthesized by introducing aldehyde functional groups on the benzene rings of straight‐chain phenolic resins. Subsequently, a dynamic imine‐bonded (–C=N–) crosslinked network is constructed through the Schiff base condensation reaction of these aldehyde groups with the 1,6‐hexanediamine (HMDA) to obtain recyclable thermosetting phenolic resins. Due to the unique structure of phenolic resins, there is an inherent limitation on the number of aldehyde groups that can be introduced, resulting in a decrease in mechanical and thermal properties after curing. Therefore, in this system, hexamethylenetetramine (HMTA) is introduced as a co‐curing agent to enhance the properties while maintaining recyclability. Four imine‐phenolic crosslinked polymers with different HMDA/HMTA molar ratios are designed to systematically investigate their comprehensive performance and recyclability. The results show that all polymers exhibit high glass transition temperatures (110°C–150°C), toughness (elongation at break 3.5%–4.0%), high tensile strengths (26.3–32.8 MPa), and recyclability. Furthermore, the basalt fiber composites prepared with this imine phenolic resin can be completely degraded under weak acidic conditions, enabling non‐destructive recycling of basalt fibers.
Luo et al. (Mon,) studied this question.