Self‐foaming polyurea foams reinforced by nano SiO₂ via a non‐isocyanate route

Abstract

The feedstocks for conventional polyurea foams (PUrFs) are limited but they have more choices in urea route as discribed in this work. Urea, ternary amine T403 and diaminodecane DA‐10 were used for the construction of self‐foaming PUrFs, in which the byproduct ammonia performs as a foaming agent. The influence of nano SiO2 content and feeding ratio of T403 to DA‐10 on the pore morphology and the properties of PUrFs were investigated. A feeding amount of 3 wt% nano SiO2 is found to be able to significantly improve the nucleation performance of PUrFs. If the nano SiO2 loading is higher (5 wt%) the melt strength will increase, which is not benefit for the foaming. An appropriate feeding ratio of T403 to DA‐10 (1/1, sample PUrF‐3‐50) can improve the crystallinity thus promoting the nucleation in foaming process. The comprehensive performance of PUrF‐3‐50 is found to be the highest, with an average pore size at 429 μm, an apparent density at 298 kg/m3, and a compressive strength (75% strain) at 3.2 MPa. It is worth noting that the hysteresis of PUrF‐3‐50 is high (>90%) and stable. This work provides a new strategy for the preparation of PUrFs and broadens the applications of urea‐based polymers.