High‐performance thermoplastic polyureas via a non‐isocyanate route from urea and aliphatic diamines

Abstract

Polyureas (PUrs) with excellent properties have been applied widely in many fields. These days attention has been turned to non-isocyanate routes for PUr preparation due to the toxicity and the high cost of isocyanates. Urea is a green chemcial which can be either from urine or from recycled carbon dioxide and ammonia. Here we introduce a urea-based route to prepare PUrs, by melt polycondensation of urea and 1,10-diaminodecane (DA-10) or/and 1,6-diaminohexane (DA-6) without catalyst, solvent, and high pressure. It is difficult to synthesize such thermoplastic PUrs from diisocyanate without any solvent since the melting point of PUr is normally higher than 170 C at which isocyanate is able to react with urea group to form biuret. The thermoplastic PUrs obtained in this study exhibit excellent mechanical and thermal properties. Furthermore, the properties can be adjusted by changing the feed ratio of diamines (DA-6/DA-10). The compression-molded PUrs show even better mechanical properties than ultra-high molecular weight polyethylene (UHMWPE). The values of Young's modulus, strength at break and elongation at break are found to be 230-300 MPa, 40-60 MPa and 200%-400%, respectively (except for PUr-6). Therefore, this facile, non-isocyanate approach provides a viable alternative to the current industrial process for highperformance PUrs.

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

“…The peak at about 3450 and 1640 cm −1 are ascribed to stretching vibrations of NH and CO, respectively. Due to the existence of flexible polyether segments and the crosslinking structures in the backbone, the NH and CO are less hydrogen bonded, compared with regular PUrs 35 . The poorer crystallinity can also be illustrated through XRD diffraction peaks.…”

“…Due to the existence of flexible polyether segments and the crosslinking structures in the backbone, the N H and C O are less hydrogen bonded, compared with regular PUrs. 35 The poorer crystallinity can also be illustrated through XRD diffraction peaks. In comparison with linear PUrs, the diffraction peak becomes broader and the position shifts to a smaller degree.…”

“…In our previous study, PUrs can be prepared via urea aminolysis in which ammonia is released continuously. 34,35 It is well fitted with the characters of condensation self-foaming system and could be utilized in the fabrication of PUrFs. Furthermore, urea aminolysis is able to avoid the limited choice of feed stocks, compared with the isocyanate route.…”

“…In our previous study, PUrs can be prepared via urea aminolysis in which ammonia is released continuously 34,35 . It is well fitted with the characters of condensation self‐foaming system and could be utilized in the fabrication of PUrFs.…”

Synthesis, Structure and Properties of Polyester Polyureas via a Non-Isocyanate Route with Good Combined Properties

“…Isocyanates and their precursor, phosgene, are highly toxic and harmful to human health and the environment [4]. As isocyanate is also highly reactive, it is very hard to preserve and control its reaction [5]. In addition, it is a significant challenge to process polyureas because the melting temperature of polyureas with isocyanates is close to their decomposition temperature due to strong intermolecular hydrogen bonding [6].…”