Lightweight phenolic resin aerogel with excellent thermal insulation and mechanical properties via an ultralow shrinkage process

•Phenolic resin aerogel is synthesized from linear and boron phenolic resin.•The ultralow shrinkage attributes to the strong B-O bond in boron phenolic resin.•Thermal conductivity of aerogel with a density of 0.105 g/cm3 is 0.0352 W/(m·K).•Aerogel shows excellent mechanical stability and resilience capacity. Lightweight phenolic resin aerogel with excellent thermal insulation and mechanical properties is an attractive material for thermal engineering applications. However, to synthesize such material, generally, a significant volume shrinkage would occur during the aerogel formation and the processing time is long. To conquer such issues, the lightweight phenolic resin aerogel with excellent thermal insulation and mechanical properties was synthesized by an elaborately designed process, where linear thermoplastic phenolic resin (LPR) and boron-modified thermosetting phenolic resin (BPR) were used as the raw materials. It was found that the shrinkage rate and the processing time of the phenolic resin aerogel were significantly reduced. By optimizing the synthesis process, the aerogel with a density of 0.105 g/cm3 and a thermal conductivity of 0.0352 W/(m·K) was achieved.