Thermo-expandable microspheres strengthened polydimethylsiloxane foam with unique softening behavior and high-efficient energy absorption

Herein, a simple and controllable foaming method was used to prepare the polydimethylsiloxane (PDMS) foams with high compressive resistance and motion-energy absorption efficiency. The thermo-expandable hollow microspheres (TEHM) expanded in PDMS matrix to form the TEHM/PDMS foams, which exhibited strengthened mechanical properties with unique softening behavior and high energy absorption property. The compressive curves of the TEHM/PDMS foams under small, medium and large strain were investigated to evaluate the softening behavior. Specifically, the TEHM/PDMS (1:2) foams had a compressive modulus of 10.2 MPa and a compression strength of 0.8 MPa, while neat PDMS showed only 4.3 MPa in modulus and 0.5 MPa in strength at 10% strain. However, after the large compression of 70%, the modulus decreased from 10.2 MPa to 2.5 MPa, which only was 25% of the initial value. Furthermore, the high ideal efficiency of motion-energy absorption of 38.3% was obtained in the TEHM/PDMS (1:2) foams while neat PDMS only got 15.8% at 70% strain. The softening phenomenon and high motion-energy absorption were ascribed to the step-by-step broken of TEHMs. The softening performance endows the foams with good toughness and consumes the impacted energy efficiently, providing a new horizon to broaden the application in anti-impacted and damaged area.