Tough and transparent polyurethane networks with self-healing capability at mild temperature conditions were successfully prepared in a 1-pot procedure. The self-healing ability of synthesized polyurethane comes from the covalent disulfide metathesis and non-covalent H-bonding.The mechanical testing indicates that disulfide metathesis reforms the covalent bonds on a longer time scale, while H-bonding gives rise to a healing efficiency of around 46% in the early healing processing. The compromise between mechanical performance and healing capability is reached by tailoring the concentration of disulfide. The tensile strength of the sample with 100% self-heal efficiency can get to 5.01 MPa, which can be explained by higher mobility of polymer chain under ambient temperature from creep testing. In order to increase the tensile strength of self-healing elastomer, the hydrogen bonding effect received attention. H-bonding is a kind of noncovalent self-healing trending force; the supermolecular selfhealing elastomer based on H-bonding interaction was firstly developed by Leibler and colleagues. 16,17 Other researchers also have similar reports. 18,19 Although the self-healing effect of H-bonding is limited, the contribution to the self-healing cannot be ignored.This work focuses on obtaining a material with good mechanical properties and self-healing in 1-pot method by adapting the disulfide concentration. The self-healing contribution of disulfide metathesis and H-bonding effect of this system were investigated. To the best of our knowledge, disulfide self-healing assisted H-bonding selfhealing materials have not been systematically studied.2 | EXPERIMENTAL | MaterialsPolytetramethylene ether glycol (PTMEG) with a number average molecular weight of 2000 g·mol −1 was provided by Aladdin IndustrialCorporation and was degassed for more than 3 hours at 90°C.

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[a] 1IntroductionThermites are is widely used in gas generators [1],m icropropulsion [2],w elding [ 3],electric igniters [4],a mmunition primers [5],a nd high energetic additives in both explosives and propellants [6,7],d ue to theirh igh adiabatic flame temperatures, flame propagation velocity,a nd energy density.T he energetic materials composed of individual fuel and oxidizer particles with nano-scale dimensions are named as metastable intermolecular composites (MICs). Compared with conventional thermites, MICs have higher flame propagation velocity and loweri gnition temperature owing to the effective reductiono ft he diffusion distance, heat-up time and the increase of specific surface area [8][9][10].However,f abricatingp olymer binders with high mass fractions of nanoscale thermite is still ag reat challenge due to the rapid increase in viscosity upon the addition of high surface area nano thermites, whichs ignificantly hindert he application of nano thermite [11,12].T he reaction performance of nano thermite depends on several factors, including naturep roperty of fuel and oxidizer,e quivalence ratio, particle size and distribution, contract area and diffusion distance betweenf uel and oxidizer particles [13][14][15][16][17][18]. Recently,Z achariaha nd co-workers [19,20] found that precombustion sinteringp rocess before the redoxreactions ignificantlyh indered the energy releasing, leading to much lower released energy than as excepted. Designing an ew architecture with large interfacial contacta rea can greatly improve the reactivity between fuel and oxidizer.M any new methods have been explored to enhance the ignition and combustion property of nano thermite and the processing of fuel-rich propellant formula, such as agglomera- In this paper,apollen-like porous Fe 2 O 3 was synthesized by at wo-step approach and subsequently, high-energy Fe 2 O 3 /Al micrometer-sized thermites with increased contact areas were obtainedb ya ssembling Al-NPs into the as-synthesizedp orous Fe 2 O 3 by using home-made vacuum apparatus. Al-NPs were embedded in different pores of the porous Fe 2 O 3 ,w hich can inhibit the pre-combustion sintering of Al-NPs and improvet he reaction efficiency and energy releasing.F urthermore, the micrometer-sized Fe 2 O 3 sphere particlesc an mitigate highm ass loading constraints during the casting processing of af uel-rich propellant. For comparison, pollen-like Fe 2 O 3 /Al thermites were as well prepared by ultrasonic mixing,and physical mixing. Additionally,c ommercial Fe 2 O 3 /Al thermite was prepared by ultrasonic mixing. Thermal properties of the samples were evaluated by TGA/DSC. Compatibility of obtainedt hermite and the main components of solid propellant (NC,G AP,R DX, HMX, and Cl-20) were evaluated by using DSC method for sample safety during preparation, transportation, usage, and storageo fthermite contained propellants [23,24].

The correlation of diisocyanate structure with hydrogen bonding and microphase separation and further their influence on mechanical property was investigated in high soft segment (about 90 wt%) energetic poly(bis‐azidomethyl oxetane/tetrahydrofuran) polyurethane binder. The hydrogen bonding analysis from Fourier transform infrared spectroscopy demonstrated that the limited intersegmental hydrogen bonding can occur in the hard domain, and small‐angle X‐ray scattering results also showed that the absence of high‐order peaks in synthesized high soft segment polyurethanes. However, coplanar and symmetric diisocyanate and its inner benzene ring are favorable to ordered arrangement of hard segment, and further mircophase seperation enhance the tensile strength. POLYM. ENG. SCI., 59:724–729, 2019. © 2018 Society of Plastics Engineers