Investigation of mechanical and self-healing properties of hydroxyl-terminated polybutadiene functionalized with 2-ureido-4-pyrimidinone

Abstract

Hydroxyl-terminated polybutadiene (HTPB) resin is the most widely used material for producing polyurethane elastomers due to its ability to maintain elastomeric properties at very low temperatures. Moreover, its high solid-loading capacity makes it an ideal binder for composite manufacturing. Replacing this resin with a self-healing HTPB resin, in addition to the aforementioned properties, can increase the service life of components and reduce potential damage to parts fabricated with this resin. In this study, thermal and mechanical properties of self-healing HTPB resin are compared with those of conventional HTPB resin. Low-temperature differential scanning calorimetry (DSC) analysis indicates that the elastomeric properties of the resin have not changed significantly, and glass transition temperature (T_g) increased only about 5°C. Additionally, both resins exhibit similar and predictable thermal behaviour in thermogravimetric analysis (TGA). Tensile testing reveals a 45% increase in tensile strength and a 75% increase in Young’s modulus, while elongation at break decreases by 64%. Viscosity changes show a three-fold increase compared to the original resin, and finally, the quantitative self-healing efficiency obtained through tapered double cantilever beam (TDCB) testing is ~96% after 24 h.

Graphical abstract

Self-healing hydroxyl-terminated polybutadiene (HTPB) resin, in addition to exhibiting excellent elastomeric properties and high solid loading, possesses the ability to repair cracks and scratches that may form within its structure. Intrinsic self-healing process commences immediately upon crack initiation, and over time, the resin gradually reverts to its original state, with up to 96% of the damage being repaired within 24 h.