Preparation of environmental-benign castor oil-derived polyurethane thermal conductive structural adhesives with superior strength

Thermal conductive structural adhesives offer a robust solution for injection into the battery core of power battery packs in new energy vehicles, effectively providing filling, protecting, and facilitating timely heat dissipation. In this work, a series of castor oil (CO)-based polyurethane prepolymers with different isocyanate (NCO) contents were synthesized by a solvent-free method, which designated as Component B (curing agent) for the CO-based polyurethane (CIPU) adhesives. Polyaspartic acid ester (PAE) resin compounded with poly (tetramethylene ether glycol) (PTMG) of different molecular weights, constituted Component A of the CIPU adhesives. The effect of mass ratio of PAE to PTMG (M value) on mechanical performance of the CIPU adhesives under different curing agent conditions was investigated. The results indicated optimal overall performance for the CIPU adhesive with an M value of 3, exhibiting a tensile strength of 10.25 MPa, an elongation at break of 107.14%, and a steel-steel tensile shear strength of 4.7 MPa. Subsequently, a series of CIPU thermal conductive structural adhesives were prepared by introducing thermal conductive fillers into the optimized CIPU adhesive formula. The introduction of a 35% Boron nitride content yielded a CIPU thermal conductive structural adhesive with a thermal conductivity of 0.64 W/m·K, and a steel-steel tensile shear strength of 6.97 MPa. These innovative CIPU thermal conductive structural adhesives prepared herein are expected to be applied in the new energy automotive and electronics industries.