Poly(caprolactone) Enabled Ultralight and Recyclable Poly(butylene adipate-<i>co</i>-terephthalate) Foams for Thermal Insulation Application

Biodegradable thermal insulation foams are drawing widespread attention due to the growing environmental pollution and thermal energy waste. Polymer-based foams characterized by flexibility, recyclability, and excellent thermal insulation, hold immense promise for application domains aimed at decreasing thermal energy waste. Poly(butylene adipate-co-terephthalate) (PBAT) has been widely employed in terms of its superior mechanical properties and acknowledged biodegradability. However, owing to the poor foamability and inherent shrinkage of PBAT, it is still challenging to prepare high-performance PBAT foams with excellent thermal insulation. Herein, the biodegradable polycaprolactone (PCL) crystalline particles were introduced into the PBAT matrix. High mechanical strength and recyclable multifunctional PBAT foams were prepared by the physical foaming process. The presence of PCL can improve the crystallization and promote the formation of open-cell structures. Thanks to the heterogeneous nucleation and special open-cell structure, the achieved PBAT/PCL foam shows ultralow density (0.04 g/cm3), restricted shrinkage ratio (<5%), enhanced thermal insulation capacity (32.5 mW/m·K), and good hydrophobicity (106.0°). More importantly, compared with other degradable polymer foams, PBAT/PCL foam shows superior degradation ability in soil. Our method offers a novel alternative for producing environmentally friendly, recyclable, multifunctional thermal insulation foams, without the worries regarding biodegradability that are linked with nondegradable materials.