Fabrication of polyurethane binders grafted with functional reactive plasticizers by a catalyst‐free click reaction

Abstract

The design of nonmigratory energetic plasticizers with low sensitivity and high performance is of great significance but challenging. Herein, two nonmigratory norbornanebased reactive plasticizers (NRPs) are attached covalently to poly(glycidyl azide-co-tetrahydrofuran) (PGT)-based polyurethanes (PUs), offering a reliable, self-stable, and alternative energy source originating from ring strain, while mitigating the dangers to the environment by preventing migration. A binary mixture of PGT and NRPs is thermodynamically miscible up to 50/50 w/w. The catalyst-free click reactivity of the NRPs toward PGT evaluated by the activation energy is verified by calculating the frontier molecular orbital energy levels.The absent weight loss of the pure NRPs evident from the measured thermal stability of the NRP/PGT-based PU binders indicated that the NRPs react completely with the PGT matrix. The tensile properties of the PGT-based PU binder by the inclusion of NRPs increased with increasing NRP content because of the increased number of triazole groups and the norbornane moiety.

Simultaneous Enhancement of the Mechanical Properties, Performance and Insensitivity of an Energetic Elastomeric Polyurethane Binder by Kinetically Grafting Reactive Spiranes

“…This difference is in good agreement with the predicted results of approximately 100 kJ mol −1 of 1,1-dimethylcyclobutane [36,38]. On the other hand, the predicted RSE of RGS decreased with an average of approximately 10 kJ mol −1 for the two building blocks independent of n. The observed reduction in RSE could be attributed to stabilization by the neighboring substituents [36,39,40]. A similar decrease in the propargyl and 3-butynyl species suggested that the extent of the stabilization of cyclics appeared to be mainly dependent on the neighboring substituents.…”

“…This phenomenon was also observed in a previous study [11]. One explanation for this is that the increased chain length from n = 1 to n = 2 results in high free volume [39,42,43]. The degree of compatibility between RGS and uncured GAP in terms of the configuration of the building blocks can be ranked as SH > DSD.…”

“…The miscibility study revealed the better molecular chain flexibility of the BDSDC@GAP binary mixture, resulting in a softer and more flexible nature for the BDSDCincorporated PUs than the PDSDC-incorporated ones. The appreciable enhancement in tensile characteristics can be explained by the higher amount of triazole groups formed through the annulation of alkyne by azide increasing the resistance to the movement of the polymer skeleton and imparting higher strength [39]. The structure of the cyclic building blocks was also found to be another unneglectable factor in the enhancement of the mechanical characteristics.…”

A review: Multidimensional internal plasticization of molecular structure in energetic polymer

“…29 In 2020, Kwon attached two norbornane-based reactive plasticizers (NRPs) to poly (Glycidyl Azide tetrahydrofuran) based polyurethane, preventing the harm from migration. 71 In the study, reactive monocyclic plasticizers (RMCPs) were chemically incorporated into GAP to reduce the instability of cured polymer adhesive. 70 After adding RMCPs, the tensile properties and impact sensitivity of GAP-based polyurethane adhesive were enhanced due to the transformation of azide into triazole groups.…”