Development of robust and rapid self-healing polymers for the repair of microcracks in energetic composite materials

doi:10.21203/rs.3.rs-2955346/v1

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Development of robust and rapid self-healing polymers for the repair of microcracks in energetic composite materials

https://doi.org/10.21203/rs.3.rs-2955346/v1

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Adhesives with superior toughness and self-healing properties are critical for the practical application of energetic composite materials (ECMs). However, most self-healing polymers exhibit low creep resistance and toughness, which makes simultaneous optimization a challenge. To overcome this, we introduced asymmetric alicyclic and bent biphenyl ring structures into the hard domain units of soft polymers, which resulted in adhesives with robust mechanical properties. The synergistic effect of dynamic disulfide and hydrogen bonding in the adhesive allows for excellent self-healing efficiency. We then conducted a comprehensive investigation into the structure, thermal stability, self-healing, mechanical properties, rheology, and adhesion properties of the synthesized disulfide bond-containing self-healing polyurethanes (PUDS). Our study demonstrates that PUDS films can achieve a toughness of 20.93 MJ m^− 3, and when cut in half and reassembled, they recover to more than 90% of their original toughness within 20 minutes, showcasing impressive mechanical properties and self-healing efficiency. Our experimental measurements and molecular dynamics simulations reveal that the interfacial interaction with 1,3,5-trinitro-2,4,6-triaminobenzene (TATB) is stronger when the hard segment content of the adhesive is higher. Furthermore, even after accidental mechanical damage, cracked ECMs can be effectively healed within 24 hours at 60℃. Self-healing and highly resilient adhesives offer promising avenues for enhancing the safety and longevity of energy-containing composites, with potential military and civil applications.

Self-healing polymers

Disulfide metathesis

Hydrogen bonds

Energetic composite materials (ECMs)

Microscale regulation

Energetic composite materials (ECMs), comprised of energy-containing compounds and polymer adhesives, are exposed to a range of external stimuli throughout their life cycle, with microcracking or interfacial debonding commonly occurring in response to factors such as thermal or mechanical stresses[1]. Such defects render ECMs more prone to detonation upon exposure to various stimuli such as impact or friction, posing a serious risk to the weapon system's service life, functionality, and safety, potentially resulting in substantial economic losses, environmental damage, and human casualties[2]. The multi-component nature of polymer adhesives and their ease of functionalization make them essential components of energy-containing composites [3–5]. Thus, designing a highly efficient self-healing adhesive capable of rapidly repairing cracks caused by external stimuli not only improves the service life and safety of the weapon system but also enhances the self-healing ability of the high solids content of ECMs[6–8].

The aerospace and military industries have an urgent need for polyurethane elastomers with exceptional mechanical strength, toughness, and self-healing ability [9–14]. However, achieving these properties has proven challenging due to the conflicting requirements of high mechanical strength and self-healing [15–17]. Nature has inspired the incorporation of supramolecular reversible structures [18, 19], including hydrogen bonds [20–26], metal-ligand interactions [27–30], and π-π interactions [31], and the reversible exchange of dynamic covalent bonds [18, 32], such as Diels-Alder reactions [33, 34], imine bonds [35], and disulfide bonds [36, 37], to repair mechanical damage in polymeric matrices. While previous studies have shown that supramolecular materials can enable reversible dissociation and self-healing without external stimuli, these materials often exhibit lower mechanical properties (e.g. toughness < 10 MJ m^− 3), poor creep resistance, and temperature sensitivity [25, 38–42]. Moreover, the introduction of a large number of fillers in ECMs reduces adhesive interfacial contact and hinders the healing process, requiring demanding healing conditions [43]. Therefore, designing a polymer with excellent mechanical properties for self-healing to occur under mild conditions is necessary. Disulfide bonds are known to be activated by exchange reactions at the right temperature or other different stimuli and offer significant advantages in terms of self-healing [10, 44, 45]. Several research groups have investigated the use of disulfide bonds in self-healing elastomers. For example, Li [46]et al. prepared self-healing ECMs with 95 wt% filler using this approach but were only able to achieve a 74.3% self-healing efficiency and 2.1 MPa mechanical strength after conducting the Brazilian test. In another study, Ding[47] et al. developed an ECMs composed of 72.4% filler and a self-healing thermoplastic elastomer featuring disulfide bonds. After applying compressive stress to significantly increase the ECMs interfacial contact effect and then heat treatment for 24 hours, the ECMs demonstrated a self-healing efficiency of 92.8% and high mechanical strength of 3.21 MPa. Additionally, Jing[48] et al. reported on a self-healing polyurethane that contained multiple active hard segment structures. This material fully regained its original properties within 5 hours at 60°C. However, in the case of the ECMs containing 80% solid filler, only 83% of the tensile strength could be recovered when heat treated at 70°C after the material had fractured. These findings indicate that aromatic disulfide bond exchange reactions, which have low bond dissociation energies and stable radicals, hold promise for obtaining desirable self-healing materials[49, 50]. Building on this property, we believe that further improvements in the mechanical and self-healing properties of adhesives can be achieved by regulating the dissociation/conjugation rate of dynamic covalent bonds. Specifically, we propose that a microphase structure consisting of hard and soft segments can be precisely designed to control the viscoelasticity of the polymer and integrate seemingly contradictory properties into a single elastomer [51], thus avoiding inherent trade-offs. In this study, we synthesized elastomers with a unique two-phase morphology by employing a molecular design approach. Specifically, we used polycaprolactone diol as the soft segment and an ortho-substituted 2-Aminophenyl disulfide with a bent structure and an asymmetric alicyclic structure of Isophorone diisocyanate as a hard segment. We adjusted the hard segment content to balance the mechanical properties and healing efficiency of the elastomers.

Our self-healing disulfide-bonded polyurethane elastomer (PUDS) exhibited excellent toughness due to the synergistic effect of the dual dynamic network of disulfide and H-bonds. Scratches on the surface of PUDS healed rapidly within 20 minutes after gentle heating. In addition, PUDS demonstrated excellent compatibility and adhesion properties with ECMs, making it a promising structural material for use in the field of ECMs. We also used PUDS as an adhesive to bind together with explosive crystalline 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) to prepare ECMs, which showed excellent crack healing ability, maintaining their morphological integrity within 24h at 60°C. In conclusion, our findings offer a comprehensive understanding of the relationship between molecular structure, rheological behavior, and self-healing performance in PUDS adhesives. These insights could facilitate the rational design and optimization of self-healing adhesive materials with specific properties that are expected to have broad applications in the field of ECMs, advancing the development of sustainable and high-performance materials.

2.1 Materials

Polycaprolactone diol (Mn = 2000g/mol), Isophorone diisocyanate (IPDI, 99%), and Ditin butyl dilaurate (DBTDL, 95%) were obtained from Macklin Inc. 2-Aminophenyl disulfide (2-AFD, 98%) was purchased from Aladdin Inc. N, N-Dimethylacetamide (DMAc, 99.5%) was obtained from Energy Chemical Inc. 1,3,5-triamino-2,4,6-trinitrobenzene (TATB, technical grade) was provided by China Gansu Yinguang Chemical Co. All chemical reagents were used without further purification in this work.

2.2 TPU synthesis

We synthesized self-healing adhesive PUDS via a two-step approach. To prepare PUDS-1, first placed 12 g (6 mmol) of PCL-diol in a round-bottomed flask equipped with a mechanical stirrer and dried it in an oil bath at 100°C under vacuum for 2 h to remove moisture. Then cooled the flask to 85°C for the next step of the synthesis. We dissolved 3.08 g (13.86 mmol) of IPDI and DBTDL (0.2% of the total mass of raw materials) in 10 mL of DMAc, added the mixture dropwise to the flask, and kept stirring for 2 h under N₂ atmosphere. Next, we dissolved 1.79 g (7.2 mmol) of 2-AFD in DMAc to form a solution with a concentration of 40%, which was slowly added dropwise to the above system. The reaction continued for 2 h in an oil bath at a constant temperature of 65°C to allow for optimal polymerization. The resulting mixture was poured into PTFE molds, dried in a vacuum oven at 50°C for 2 h to remove air bubbles, and then dried in an oven at 60°C for 48 h to obtain a self-healing polyurethane film with a thickness of 0.5–1.5 mm (Fig S1). We followed the same procedure to prepare different PUDS polymers, as summarized in Table S1.

2.3 Preparation of ECMs

2 g of adhesive was dissolved in ethyl acetate and prepared as a dilute solution with a mass fraction of 5%, and 8g of TATB was then dispersed in ethyl acetate to form a suspension. The prepared adhesive and TATB are mixed and stirred vigorously at 60°C until most of the solvent has evaporated to form a slurry mixture, and then dried in an oven at 65°C for 24 hours.

2.4 General characterization

We conducted ¹H nuclear magnetic resonance (NMR) spectroscopy tests on an AVANCE NEO 400 MHz spectrometer (Bruker, Germany), using CDCl₃ as the solvent. To determine the molecular weight distribution, we used a PL-GPC50 device (Agilent, USA) equipped with a refractive index detector. The eluent was dimethylformamide (DMF), and the flow rate was set to 1.0 mL·min^− 1. The average molecular weight (Mn), weight average molecular weight (Mw), and polydispersion index (PDI) were calculated relative to a linear polystyrene standard. Infrared spectroscopy was conducted using an INVENIO S spectrometer (Bruker, Germany) equipped with an attenuated total reflection (ATR) accessory. All films were scanned 16 times at a resolution of 4 cm^− 1. X-ray diffraction (XRD) analysis was carried out using a DX-2700 X-ray diffractometer (Dandong Hao yuan Corporation, China) equipped with copper Kα radiation (λ = 0.154 nm) and tested over an angle range of 5–50°. Thermogravimetric analysis of the samples was conducted using a TGA-2 instrument (Mettler Toledo, Switzerland) with a heating rate of 10°C/min from 40 to 500°C under N₂ atmosphere. Differential scanning calorimetry (DSC) was tested on a DSC 214 polyma apparatus (NETZSCH, Germany) at temperatures ranging from − 80 to 100°C in N₂ atmosphere and a heating rate of 10°C min^− 1. We performed atomic force microscopy (AFM) measurements using a tapping mode on a Bruker Dimension ICON scanning probe microscope (Bruker, Germany). Small-angle X-ray Scattering (SAXS) was conducted on a SAXS point 2.0 device (Anton Parr, Austria) equipped with and Cu Kα radiation source (λ = 0.1541 nm). The compatibility of the samples was assessed according to Chinese Military Standard GJB772A-97 using an IDEA Science STABIL VI vacuum stability tester (USA).

2.5 self-healing, and tensile testing

The self-healing ability of the elastomer was evaluated through a scratch self-test. Initially, the films were scratched using a Swann-Morton sterile scalpel and subsequently placed on a heated platform maintained at 60°C. The self-healing progress of the scratches was monitored at regular intervals using an LSM-900 laser scanning microscope (Carl Zeiss, Germany). The mechanical and self-healing properties were tested using a Dual Column Table 68TM-30 test machine (Instron, America) equipped with a 1 kN transducer, and the specimens were tested in tension at 100 mm/min at room temperature (25°C). The results for each sample correspond to the average of the results of five individual tensile tests. To evaluate the self-healing efficiency of the elastomer, the sample was cut down the middle and the fractured surfaces were brought into full contact without applying external force, and then tensile tests were carried out on samples with different self-healing times. The toughness of the specimens was calculated from the integration of the area under the stress-strain curve and the self-healing efficiency was defined as

$$Healing Effciency\left(\%\right)=\frac{toughness of healing sample}{toughness of original sample}\times 100\%$$

Cyclic stretching tests were also conducted to shape the recovery abilities of the elastomer in the short term. The samples were loaded and unloaded five times at a fixed stretching rate of 100 mm/min and a maximum strain of 100%. The specimens were then left for 60 minutes before being stretched again.

2.6 Rheology

The rheological properties of the adhesives were assessed using an oscillating rheometer MCR 302 (Anton Paar, Austria) equipped with a 25 mm parallel plate measuring system. The samples were prepared to a thickness of approximately 0.6–0.8 mm. The stress relaxation modulus test was performed at a strain rate of 5%, and a test period of 1000s with logarithmic sampling times. Temperature-sweep tests were conducted in the range of 25–100°C at a set angular frequency of 1 rad s-1 and a shear strain of 1%. Frequency sweep tests were performed by collecting data at 15°C intervals within the range of 30–90°C, with a shear strain of 1% and an angular frequency of 0.01 to 1000 rad s^− 1. The activation energy (${E}_{a}$) for the relaxation process was calculated using Eq. 1[52]:

$$\tau ={A}_{0}\text{e}\text{x}\text{p}(-\frac{{E}_{a}}{RT})$$

where ${A}_{0}$ is the prefactor; $\tau$ is the characteristic relaxation time(s); and R is the gas constant (kJ/mol·K). The yield stress provides the minimum value required for the internal structure to collapse, which was obtained by performing calculations using a modified Casson model. As shown in Eq. 2[53]:

$${G}^{{\prime }{\prime }1/2}={G}_{yield}^{{\prime }{\prime }1/2}+{c}^{1/2}·{\omega }^{1/2}$$

in which, ${G}_{yield}^{{\prime }{\prime }}$ is the yield stress, Pa; and $c$ is a constant.

2.7 Interfacial adhesion measurement

The interfacial adhesion properties of the adhesive to the energetic compound were evaluated using uniaxial tensile tests. To this end, TATB pellets were bonded to a 'T-shaped' support using epoxy resin adhesives that were cured for approximately 10 minutes. The PUDS adhesives, cut to a size of 25mm×25mm×1mm, were then placed between the two TATB pellets and wetted with a drop of ethanol at the interface to repel air. The entire structure was subsequently pressed against 200g weights for 5 minutes while ensuring that the fixtures remained aligned. Tensile tests were conducted using a 68TM-30 apparatus at a strain rate of 1 mm·min^− 1, and load-displacement curves were recorded until the contact parts cracked. The adhesive strength was calculated by dividing the maximum load by the initial overlap area.

3.1 Molecular design and structure characterization

We synthesized a range of PUDS with varying mechanical properties using the synthetic route outlined in Fig. 1a, in which PCL-diol served as the soft chain and IPDI and 2-AFD acted as the hard chain. Notably, the presence of disulfide bonds within the PUDS molecular chain enabled exchange reactions with neighboring molecular chains, while hydrogen bonding in both the soft and hard segments facilitated the reorganization of the molecular network, promoting self-healing capabilities (Fig. 1b and 1c). Elastomers were synthesized with varying molar ratios of hard to soft segments, and their properties were optimized, with hard segment and disulfide content presented in Table S1. The Mn, Mw, and PDI were determined by GPC and listed in Table S2. For the PUDS range of polymers, the PDI ranged from 1.67 to 1.99, demonstrating a narrow molecular weight distribution. NMR spectroscopy (Fig. S2 and S3) confirmed the structure of the adhesive and demonstrated a gradual increase in the hydrogen of the imino group on the IPDI and the benzene ring on the 2-AFD as the hard segment content increased. ATR-FTIR spectroscopy (Fig. S4) characterized the final product, with the peaks at 3366 and 1644 cm^− 1 assigned to the -N-H and -C = O stretching vibrations of the urea bond, respectively. The disappearance of the characteristic peak of the -NCO stretching band at 2269 cm^− 1 provided compelling evidence that the -NCO group reacted with the amino group of the chain extender to form the urea group at the end of the reaction.

To further investigate the intermolecular hydrogen bonding behavior, we employed a Gaussian function to fit the stretching vibrational region of the C = O group, revealing three absorption peaks (Fig. 2a): the stretching vibrational of the free hydrogen bonded C = O group at 1734 cm^− 1, the disordered hydrogen bonded C = O group at 1720 cm^− 1, and the ordered H-bonded C = O group at 1693 cm^− 1. The percentage of hydrogen bonding content in the PUDS samples was quantified and plotted in Fig. 2b. As the hard segment content increases, the degree of ordered hydrogen bonding in the system gradually increases, promoting an ordered structure. The enhanced hydrogen bonding interactions offer a strong driving force for microphase separation. The microstructure of the PUDS sample was further investigated using XRD. The XRD pattern displayed only a broad amorphous peak centered at approximately 20°, indicating that the polymer chains assume a loosely packed conformation, precluding crystallization in the system (Fig. 2c)[24, 54]. SAXS analysis revealed with the period length gradually increased as the hard segment content increased indicating fuller micro-phase separation within the material (Fig. 2d). The AFM phase diagrams provide a visualization of the microphase separation in the PUDS samples, with dark and bright regions indicating soft and hard domains, respectively (Fig. 2e and S5). The diagrams reveal a significant microphase separation structure and a loose hard domain arrangement that becomes more pronounced with increasing hard segment content. This achievement enables the microscopic modulation of the polymer hard domains. Due to the relatively high content of ether oxygens in the PUDS-1 system, a large number of hydrogen bonding sites are provided for the hard domains to form weak hydrogen bonds. This interaction between the two phases can lead to incomplete microphase separation. Quantum chemical calculations revealed the binding energies (ΔE) relative to the monomer, providing evidence of hydrogen bond aggregation and multiphase hydrogen bonding within the system. These findings, as illustrated in Fig. S7-S9 and Table S4, demonstrate a graded strength of the hydrogen bonds. ATR-FTIR analysis was utilized to investigate the hydrogen bonding interactions in PUDS within the temperature range of 25–95°C, as depicted in Fig. S10. As the temperature increased, the stretching vibrations of N-H at 3366 cm^− 1 and the N-H bending vibrational band at 1537 cm^− 1 shifted towards lower wave numbers (red-shift), indicating an increase in bond length and a decrease in stretching vibrational frequency. In contrast, the stretching vibrational band of C = O (urethane) at 1725 cm^− 1, C = O (urea) at 1644 cm^− 1, and -O- (PCL) at 1160 cm^− 1 displayed a blue shift, indicating that reversible hydrogen bond dissociation was taking place within the PUDS network.

To adapt the adhesive to the environment in which the ECMs are to be used and stored, a qualitative assessment of the thermal stability of the adhesive is usually performed. As shown in Fig. 2f, the DSC curve of PUDS from − 80 to 100°C indicated that the glass transition temperature (Tg) of the adhesive is around − 42°C, which is attributed to the excellent low-temperature properties of PCL. Furthermore, the thermal weight loss curves of self-healing polyurethanes with varying disulfide levels were studied by TGA (Fig. S11). The PUDS series adhesives exhibited good thermal stability, with an initial decomposition temperature greater than 220 ℃. At approximately 450°C, all weight was lost, and higher disulfide content resulted in greater weight loss.

3.2 Self-healing performance and mechanical properties

Integrating self-healing properties into adhesives is an effective approach to enhancing material performance and prolonging service life. We evaluated the self-healing performance of the PUDS series adhesives through scratch recovery experiments, as shown in Fig. 3a and S12. The width of the approximately 80um scratch on the surface of the PUDS-3 sample gradually decreased and became almost flat after 10 minutes at 60°C without external forces. This self-healing ability is related to the mobility of free radicals on the fracture surface. Molecular chains can effectively promote the exchange reaction of disulfide bonds under heating conditions, contributing to the rapid healing of scratches. To provide a more visual demonstration of self-healing, a rectangular film with a cut area of 5mm*1mm was reassembled and, after 10 minutes of recovery at 60°C, the two films bonded well enough to withstand manual pulling, demonstrating excellent self-healing ability, as shown in Fig. 3b.

Further mechanical properties and self-healing efficiency of the PUDS samples were evaluated through tensile tests using a universal testing machine, as shown in Fig. 3c. The initial ultimate tensile strength (UTS), strain at break, and toughness are listed in Table S5, with UTS increasing from 2.79 MPa to 9.01 MPa with increasing hard segment content. We cut the PUDS film completely in half and then reattached it at 60°C at different times to obtain stress-strain curves, as shown in Fig. 3d and S13. The self-healing efficiency, defined as the ratio of the toughness of the healed material to that of the original material, was assessed to evaluate the self-healing properties of the PUDS films (Fig. 3e). The self-healing efficiency of PUDS-1 reached 97%, which is much higher than that of the other samples. As the healing time continued, the mechanical properties of all samples gradually increased, and the final healing efficiency remained above 90%. Increasing the disulfide content facilitated the formation of more compact and robust physical cross-linking, enhancing the mechanical strength of the adhesive. However, it also resulted in the formation of regular hydrogen bonds between the molecules, which could reduce the mobility of the molecular chains and impede the self-healing effect. The structures of PUDS-1 and PUDS-5 were determined using all-atom molecular dynamics (MD) simulations, as depicted in Figs. 4a and 4b. The hard segments of both polymers aggregate and form a structure consisting of separate soft and hard phases due to hydrogen bonding cross-linking. While the H-bonding sites on both polymer chains are identical, PUDS-5 forms a denser array of hydrogen bonds with 3.5 H-bonds formed on each hard segment, compared to only 2.8 H-bonds formed on each hard segment in PUDS-1.

The recovery properties of the adhesive are of great importance for its use under various loads. In Fig. 4c, the cyclic stretching curve of PUDS-3 is presented at a maximum strain of 100%. The stress-strain curve exhibits significant hysteresis in the first cycle, indicating that the breakage of disulfide and hydrogen bonds during the stretching process consumes a considerable amount of energy, and these bonds cannot be reconnected quickly. Therefore, the tensile stress decreases as the number of cycles increases. However, after five cycles and 60 minutes of recovery, the sample was stretched again, and the cyclic stretching curve largely overlapped with the original curve, indicating excellent mechanical recovery. The rapid rearrangement of hydrogen and disulfide bonds is a prerequisite for the recovery of deformation. Moreover, the PUDS-3 spline can withstand approximately 5,500 times its weight without tearing (Fig. 4d), and after removing the weight, it largely restored its original state within 10 minutes, demonstrating its high toughness and rapid recovery from deformation. The results of the time-aging mechanical test show that after 180 days of exposure to air, the tensile properties of the PUDS-3 film remained consistent (Fig. 4e), and the self-healing properties of the polymer chains exhibit little change. A high concentration of dynamic bonding aids in the recombination of broken regions but also results in more hydrogen bonding interactions between molecular chains. Therefore, adjusting the proportion of hard segments is a feasible approach to achieving a reasonable configuration of mechanical and self-healing properties. Compared to the relevant references reported so far (Fig. 4f), the PUDS system designed in this work not only exhibits excellent toughness but also demonstrates better self-healing capacity at moderate temperatures.

3.3 Rheological Properties

A rheological perspective can provide further insights into the dynamic behavior of the adhesive and the crack self-healing mechanism, as illustrated in Fig. 5a. PUDS-1 exhibits a low-stress relaxation in the same period, with the relaxation modulus decreasing rapidly with time and gradually approaching zero stress. As the hard segment content increases, the physical connection network becomes more complex, resulting in a gradual increase in relaxation time [64]. Additionally, the sample's relaxation modulus exhibits clear temperature dependence, as illustrated in Fig. 5b. Specifically, relaxation of the PUDS system occurs more quickly at 60°C than at room temperature, due to the weakening of intermolecular hydrogen bonds and the promotion of exchange reactions among dynamic bonds, which accelerates the relaxation rate.

We also investigated the temperature-dependent loss factor (tan δ) of the PUDS system in the range of 25–100°C (Fig. 5c). The PUDS-3/4/5 sample exhibited a tan δ value lower than unity (tan δ = 1) across the entire temperature range, indicating a solid-like behavior. This behavior is attributable to an increase in the hard segment content, which can partially immobilize the dynamic bonds and leave the material in an elastic state, thereby adversely affecting the self-healing performance of PUDS. Moreover, a frequency sweep of PUDS within the linear viscoelastic region (Fig. 5d and Fig. S14) revealed increased values of both G' and G" with increasing hard segment content. This effect was attributed to the formation of minute crystalline domains within the benzene ring structure of the molecular chain, which enhances the molecular cohesion of PUDS, imparting a more solid-like character to the material and resulting in an increase in the G' value. On the other hand, intermolecular hydrogen bonding enhances the entanglement of PUDS chains and the energy dissipation due to deformation, leading to a gradual increase of the G'' value. The lower the test temperature of the PUDS series samples, the more frequency at which G' and G'' intersect (ωcross) tends to occur at lower frequencies, as at that time, the molecular chains have stronger interactions with each other as well as lower kinematic activity. Conversely, higher temperatures facilitate the dissociation of physical networks and reversible disulfide bonds in the material. The cross point of G' and G'' appears when the scanning temperature of the PUDS-3 sample exceeds 60°C, indicating that a significant disulfide exchange reaction has occurred in the system. The reciprocal of the corresponding ωcross indicates the characteristic relaxation time ($\tau =1/\omega$)[52, 65], which represents the timescale for the stresses in a material caused by cracking to return to their initial state[66]. PUDS-1 exhibits a lower τ than other adhesives over the entire frequency range at the same temperature. We obtained the apparent activation energy (Ea) of the relaxation process by linearly fitting Lnτ and 1/T at different temperatures according to the Arrhenius equation, and the Ea values for PUDS-1/2/3 were 99.6 kJ/mol, 100.2 kJ/mol, and 124.4 kJ/mol, respectively (Fig. S15). Ea increases with the increase of hard segment content, indicating that the mechanical strength of the sample is strengthened at room temperature while ensuring sufficient self-healing ability after increasing a certain temperature. At 60°C, PUDS-5 shows high yield stress and low Cole-Cole slope values, further indicating that it is a relatively hard system (Fig. 5e and S16)[53, 67].

Overall, the results of our study demonstrate the importance of the hard segment content in determining the mechanical and self-healing properties of PUDS adhesives. The increase in hard segment content leads to a higher degree of physical crosslinking, which enhances the mechanical strength and rigidity of the material but also limits its deformation ability and self-healing performance. On the other hand, a lower hard segment content results in a more flexible and deformable material with faster disulfide exchange kinetics, but at the expense of reduced mechanical strength and stability. PUDS-3, with an intermediate hard segment content, exhibits a good balance between these properties, making it a promising candidate for further development as a self-healing ECMs.

3.4 Adhesive properties and fracture healing ability of ECMs

When the interfacial bond between the energetic material and the adhesives is weak, air trapped at the interfaces can increase the thermal resistance of the ECMs system, resulting in a higher risk of explosions. However, a strong adhesive bond can effectively dissipate energy and prevent debonding, reducing the vulnerability of ECMs during production, transportation, and storage [68]. To investigate this effect, we performed tensile tests on PUDS adhesive films sandwiched between two TATB pellets (Fig. 6a) to measure the interfacial bond strength between the film and the energy-containing compound. We hypothesize that the presence of -NH₂ and -NO₂ groups on the TATB molecule creates strong interfacial forces between TATB and PUDS, as shown in Fig. 6b where possible interfacial hydrogen bonding interactions are illustrated. The bond strength increased with increasing disulfide content, with PUDS-5 exhibiting the highest adhesion strength of 186.2 kPa (Fig. 6c and S17). The interfacial bonding strength between particles and the polymer matrix in the interfacial region can be directly assessed by the interaction energy (Einter) [69]. In this study, interfacial models of TATB and PUDS chains were constructed using molecular dynamics (MD) simulations. The optimized interfacial adhesion structure yielded a trend of Einter that aligns with the results obtained from tensile tests, suggesting that hydrogen bonding interactions effectively enhance interfacial adhesion (Fig. 6d and S18).

In consideration of the comprehensive properties required for ECMs, including self-healing ability, mechanical strength, and adhesion, PUDS-3 emerges as a highly promising polymer. To explore its potential application in ECMs systems, we prepared ECMs containing 20 wt% PUDS-3 and 80 wt% TATB using the slurry method. Compatibility is a crucial factor in ensuring the safety and reliability of explosives. According to the compatibility assessment criteria outlined in Table S6, we performed a pressure transducer method (VST) test, and the result showed a net increment of 0.041, indicating that PUDS is compatible with TATB. The resulting ECMs powder was then compacted using the press-fitting technique to obtain a sample strip measuring 30 mm × 5 mm × 2 mm, the original σ and ε values of the specimen were 3.84 MPa and 13.03%, respectively. To investigate the effects of initial damage and healing on the mechanical behavior of ECMs, samples with scratches (width: 0.25 mm, depth: 0.5 mm) were allowed to self-heal at 60°C for varying periods, as shown in Fig. 6e. It was found that the maximum tensile strength of freshly scratched samples was only 36% of the original value. However, after 6 hours, the samples recovered to 64% of their maximum tensile strength, and after 24 hours, more than 96% recovery was achieved, demonstrating the excellent self-healing efficiency of PUDS-3. The self-healing of cracks in ECMs is primarily dependent on the self-healing ability of the adhesive and the thermal movement of its chains[7]. However, the less plastic crystal structure of TATB explosives restricts the movement of polymer chains in the ECMs system, which impedes the rearrangement of the polymer network. Consequently, it takes time for the molecular chains to come closer spatially, enabling the disulfide bond exchange reaction and H-bonding at the fracture interface, which ultimately facilitates the self-healing effect. Compared to currently reported ECMs with crack healing ability [6, 43, 46, 70–72], this ECMs not only exhibits high self-healing efficiency but also possesses exceptional mechanical properties. Finally, we evaluated the storage stability of ECMs placed at room temperature for 180 days and found that it retained a tensile stress of 3.83 MPa and 13.19% elongation at break, indicating good stability (Fig. S19).

In addition, we used confocal laser scanning microscopy to observe the recovery of scratches in the longitudinal plane. Three-dimensional surface and depth profiles of ECMs with microcracks quantitatively demonstrate the self-healing process of the notches (Fig. 6f and Fig. 6g), which gradually decrease in depth with time after being heated at 60°C for 12 h until they become flat again after 24 h. This process is achieved through the migration of adhesive molecular chains and internal tension, effectively healing the damaged interface and maintaining good structural integrity. We then evaluated the self-healing efficiency of ECMs at different temperatures, as shown in Fig. 6h. The gap size was 0.5 mm deep and the rate of self-healing was defined as follows:

Self-healing speed = notch depth/self-healing period

The self-healing rate increased with increasing temperature and reached a maximum of 41.67 mm/h at 80°C, which was higher than that at 60°C. This is due to the increased energy stimulating molecular relaxation and conformational transitions, and breaking more dynamic disulfide bonds. The broken short chains migrated and diffused more readily than the long chains, thus increasing polymer chain activity and promoting crack healing [46]. Figure 6i shows the dissolution recovery characteristics of the ECMs sample, where TATB in the sample can be fully recovered after heating in DMAc at 60°C for 12 h. Dynamic disulfide bonding not only provides ECMs with healing ability but also degrades in solvents at high temperatures, thus bringing significant economic benefits and reducing the recovery cost of ECMs.

In summary, this work successfully synthesized a series of novel amorphous self-healing polyurethane systems using ortho-substituted 2-AFD with a bent structure and an alicyclic isocyanate with an asymmetric structure. The rational molecular design and microphase control of the PUDS system conferred excellent healing and reprocessing properties while maintaining its exceptional mechanical properties. At 33.4% hard segment content, the polyurethane has a toughness as high as 20.93 megajoules per cubic meter and promotes the exchange reaction of aromatic disulfide bonds and the rearrangement of hydrogen bonds at medium temperature to achieve self-healing at the crack interface (60°C, 20 min). Moreover, the strong adhesion of PUDS with energetic materials in this work makes it a promising application for ECMs. PUDS was used together with TATB to prepare ECMs and showed excellent crack healing ability under mild conditions, offering a novel approach to improve the safety and service life of ECMs.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

Thanks the Shanxi engineering technology research centre for ultrafine powder for providing platform.

Funding information

This work was supported by the 18th postgraduate science and technology project (No. 20221860).

Author information

Authors and Affiliations

School of Environment and Safety Engineering, North University of China, Taiyuan Shanxi, 030051, PR China

Wangjian Cheng, Dongjie Liao, Chenhe Feng, Fubing Gao, Minjie Li, Xiawei Zhang, Lingyu Deng

Shanxi Engineering Technology Research Centre for Ultrafine Powder, North University of China, Taiyuan Shanxi, 030051, PR China

Chuanhao Xu, Baoyun Ye, Chongwei An

Corresponding authors

Correspondence to Chongwei An

Author contributions

Wangjian Cheng：Methodology, Funding acquisition, Project administration, Writing - Original Draft. Dongjie Liao：Investigation, Data curation, Visualization, Formal analysis. Chenhe Feng：Investigation, Data curation. Fubing Gao: Investigation. Minjie Li:Investigation. Xiawei Zhang: Investigation. Lingyu Deng: Investigation. Chuanhao Xu：Writing - Review & Editing. Baoyun Ye：Writing - Review & Editing. Chongwei An：Writing - Review & Editing.

Yadav A., Pant C. S.,Das S. J. P., Explosives, Pyrotechnics, (2020) Research advances in bonding agents for composite propellants. 45 (5): 695-704.
Tao J., Wang X.,Zhao S. J. J. o. E. M., (2017) The cracks formation mechanism of an aluminized polymer-bonded explosive under tensile stress. 35 (2): 172-178.
Wang B., SongqiXu, XiweiLi, QiongYu, TaoWang, ShengYan, ShifengLiu, YanlinZhu, Jin %J ACS Sustainable Chemistry,Engineering, (2020) High-Performance, Biobased, Degradable Polyurethane Thermoset and Its Application in Readily Recyclable Carbon Fiber Composites. 8 (30).
Patrick J. F., Robb M. J., Sottos N. R., Moore J. S.,White S. R. J. N., (2016) Polymers with autonomous life-cycle control. 540 (7633): 363-370.
Jarosz T., Stolarczyk A., Wawrzkiewicz-Jalowiecka A., Pawlus K.,Miszczyszyn K. J. M., (2019) Glycidyl azide polymer and its derivatives-versatile binders for explosives and pyrotechnics: tutorial review of recent progress. 24 (24): 4475.
Huang X., Huang Z., Lai J.-C., Li L., Yang G.-C.,Li C.-H., (2018) Self-healing improves the stability and safety of polymer bonded explosives. Composites Science and Technology, 167 : 346-354.
Zhang Y., Chen J., Zhang G., Xv J., Xv J., Hu Y., Guo H., guo F., Fu J.,Jiang W., (2021) Mechanically robust, highly adhesive and autonomously low-temperature self-healing elastomer fabricated based on dynamic metal − ligand interactions tailored for functional energetic composites. Chemical Engineering Journal, 425 : .
Guo Y., Lan Q., Han C., Chen P., Liu R. J. M.,Design, (2020) Microstructural characterization of pressure-induced cracking in melamine/F2311 composites and crack-healing behavior via thermal-pressure aging treatment. 189 : 108538.
Khatib M., Zohar O., Saliba W., Srebnik S.,Haick H. J. A. F. M., (2020) Highly efficient and water‐insensitive self‐healing elastomer for wet and underwater electronics. 30 (22): 1910196.
Guo H., Han Y., Zhao W., Yang J.,Zhang L. J. N. C., (2020) Universally autonomous self-healing elastomer with high stretchability. 11 (1): 2037.
Pena-Francesch A., Jung H., Demirel M. C.,Sitti M. J. N. m., (2020) Biosynthetic self-healing materials for soft machines. 19 (11): 1230-1235.
Self J. L., Sample C. S., Levi A. E., Li K., Xie R., De Alaniz J. R.,Bates C. M. J. J. o. t. A. C. S., (2020) Dynamic bottlebrush polymer networks: self-healing in super-soft materials. 142 (16): 7567-7573.
Xiong C., Li M., Zhao W., Duan C., Dai L., Shen M., Xu Y.,Ni Y. J. C. E. J., (2020) A smart paper@ polyaniline nanofibers incorporated vitrimer bifunctional device with reshaping, shape-memory and self-healing properties applied in high-performance supercapacitors and sensors. 396 : 125318.
Cao C., Yi B., Zhang J., Hou C., Wang Z., Lu G., Huang X.,Yao X. J. C. E. J., (2020) Sprayable superhydrophobic coating with high processibility and rapid damage-healing nature. 392 : 124834.
Wang D., Liu D., Xu J., Fu J.,Wu K. J. M. H., (2022) Highly thermoconductive yet ultraflexible polymer composites with superior mechanical properties and autonomous self-healing functionality via a binary filler strategy. 9 (2): 640-652.
Zhang Y., Yu Y., Zhao X., Yang X., Yu R., Zhang Y.,Huang W. J. M. R. C., (2021) A High Strength but Fast Fracture‐Self‐Healing Thermoplastic Elastomer. 42 (14): 2100135.
Wu H., Liu X., Sheng D., Zhou Y., Xu S., Xie H., Tian X., Sun Y., Shi B.,Yang Y. J. P., (2021) High performance and near body temperature induced self-healing thermoplastic polyurethane based on dynamic disulfide and hydrogen bonds. 214 : 123261.
Wang S.,Urban M. W. J. N. R. M., (2020) Self-healing polymers. 5 (8): 562-583.
Li C. H.,Zuo J. L. J. A. M., (2020) Self‐healing polymers based on coordination bonds. 32 (27): 1903762.
Zhang Z., Ghezawi N., Li B., Ge S., Zhao S., Saito T., Hun D.,Cao P. F. J. A. F. M., (2021) Autonomous self‐healing elastomers with unprecedented adhesion force. 31 (4): 2006298.
Xu J., Chen J., Zhang Y., Liu T.,Fu J. J. A. C. I. E., (2021) A fast room‐temperature self‐healing glassy polyurethane. 60 (14): 7947-7955.
Li Y., Li W., Sun A., Jing M., Liu X., Wei L., Wu K.,Fu Q. J. M. H., (2021) A self-reinforcing and self-healing elastomer with high strength, unprecedented toughness and room-temperature reparability. 8 (1): 267-275.
Sun H., Liu X., Liu S., Yu B., Ning N., Tian M.,Zhang L. J. C. E. J., (2020) Silicone dielectric elastomer with improved actuated strain at low electric field and high self-healing efficiency by constructing supramolecular network. 384 : 123242.
Yang J., Zhang G., Wang J., Hao Y., Hao G., Xiao L., Chen J., Zhou B., Fu J.,Jiang W., (2021) Parthenocissus-inspired, strongly adhesive, efficiently self-healing polymers for energetic adhesive applications. Journal of Materials Chemistry A, 9 (29): 16076-16085.
Wang D., Xu J., Chen J., Hu P., Wang Y., Jiang W.,Fu J. J. A. F. M., (2020) Transparent, mechanically strong, extremely tough, self‐recoverable, healable supramolecular elastomers facilely fabricated via dynamic hard domains design for multifunctional applications. 30 (3): 1907109.
Yang Y., Ye Z., Liu X.,Su J. J. J. o. M. C. C., (2020) A healable waterborne polyurethane synergistically cross-linked by hydrogen bonds and covalent bonds for composite conductors. 8 (15): 5280-5292.
Zhang L., Wang D., Xu L.,Zhang A. J. P. C., (2021) A supramolecular polymer with ultra-stretchable, notch-insensitive, rapid self-healing and adhesive properties. 12 (5): 660-669.
Hu P., Xie Q., Ma C.,Zhang G. J. C. E. J., (2021) Fouling resistant silicone coating with self-healing induced by metal coordination. 406 : 126870.
Zhu M., Jin H., Shao T., Li Y., Liu J., Gan L., Long M. J. M.,Design, (2020) Polysaccharide-based fast self-healing ion gel based on acylhydrazone and metal coordination bonds. 192 : 108723.
Li Y.-h., Guo W.-j., Li W.-j., Liu X., Zhu H., Zhang J.-p., Liu X.-j., Wei L.-h.,Sun A.-l. J. C. E. J., (2020) Tuning hard phase towards synergistic improvement of toughness and self-healing ability of poly (urethane urea) by dual chain extenders and coordinative bonds. 393 : 124583.
Chen L., Feng W., Li M., Jin Z., Zhang Y., Cheng Z., Liu Y.,Wang C. J. A. F. M., (2022) A stiff yet rapidly self‐healable elastomer in harsh aqueous environments. 32 (1): 2107538.
Aguirresarobe R. H., Nevejans S., Reck B., Irusta L., Sardon H., Asua J. M.,Ballard N. J. P. i. P. S., (2021) Healable and self-healing polyurethanes using dynamic chemistry. 114 : 101362.
Xie J., Yang M., Liang J., Hu J., Li Q.,He J. J. J. o. M. C. A., (2021) Self-healing of internal damage in mechanically robust polymers utilizing a reversibly convertible molecular network. 9 (29): 15975-15984.
Li Y.-b., Zhao X., Luo Y.-j., Yang Z.-j., Pan L.-p., Zeng C.-c., Lin C.-m.,Zheng X. J. D. T., (2022) Self-healed microcracks in polymer bonded explosives via thermoreversible covalent bond and hydrogen actions. : .
Hu J., Mo R., Sheng X.,Zhang X. J. P. C., (2020) A self-healing polyurethane elastomer with excellent mechanical properties based on phase-locked dynamic imine bonds. 11 (14): 2585-2594.
Rao Q., Lu Y., Song L., Hou Y., Zhan X., Zhang Q. J. A. a. m.,interfaces, (2021) Highly efficient self-repairing slippery liquid-infused surface with promising anti-icing and anti-fouling performance. 13 (33): 40032-40041.
Zhang L., Chen L., Rowan S. J. J. M. C.,Physics, (2017) Trapping dynamic disulfide bonds in the hard segments of thermoplastic polyurethane elastomers. 218 (1): 1600320.
Kang F., Yang Y., Wang W.,Li Z. J. E. P. J., (2023) Self-healing polyester elastomer with tuning toughness and elasticity through intermolecular quadruple hydrogen bonding. 184 : 111794.
Ji S., Cao W., Yu Y.,Xu H. J. A. M., (2015) Visible‐light‐induced self‐healing diselenide‐containing polyurethane elastomer. 27 (47): 7740-7745.
Yan X., Liu Z., Zhang Q., Lopez J., Wang H., Wu H.-C., Niu S., Yan H., Wang S.,Lei T. J. J. o. t. A. C. S., (2018) Quadruple H-bonding cross-linked supramolecular polymeric materials as substrates for stretchable, antitearing, and self-healable thin film electrodes. 140 (15): 5280-5289.
Park J., Murayama S., Osaki M., Yamaguchi H., Harada A., Matsuba G.,Takashima Y. J. A. M., (2020) Extremely rapid self‐healable and recyclable supramolecular materials through planetary ball milling and host–guest interactions. 32 (39): 2002008.
Yang J., Zhang G., Wang J., Hao Y., Hao G., Xiao L., Chen J., Zhou B., Fu J.,Jiang W. J. J. o. M. C. A., (2021) Parthenocissus-inspired, strongly adhesive, efficiently self-healing polymers for energetic adhesive applications. 9 (29): 16076-16085.
Jing T., Heng X., Guifeng X., Ling C., Pingyun L.,Xiaode G., (2021) Highly stretchable, high efficiency room temperature self-healing polyurethane adhesive based on hydrogen bonds – applicable to solid rocket propellants. Polymer Chemistry, 12 (31): 4532-4545.
Azcune I.,Odriozola I. J. E. P. J., (2016) Aromatic disulfide crosslinks in polymer systems: Self-healing, reprocessability, recyclability and more. 84 : 147-160.
Xiang H., Yin J., Lin G., Liu X., Rong M.,Zhang M. J. C. E. J., (2019) Photo-crosslinkable, self-healable and reprocessable rubbers. 358 : 878-890.
Li Y., Yang Z., Ding L., Pan L., Zhang J., Zheng X.,Lin C., (2019) Feasible self-healing CL-20 based PBX: Employing a novel polyurethane-urea containing disulfide bonds as polymer binder. Reactive and Functional Polymers, 144 : .
Ding S., Zhu G., Zhao S., Wu W., Jin P., Jiao Y., Zhai W., Zhou L.,Luo Y., (2022) Simultaneously optimized healing efficiency and mechanical strength in polymer composites reinforced by ultrahigh loading fillers based on interfacial energy and dynamic disulfide bonds. Polymer, 251 : .
Jing T., Heng X., Guifeng X., Li L., Li P.,Guo X. J. M. C. F., (2022) Rapid self-healing and tough polyurethane based on the synergy of multi-level hydrogen and disulfide bonds for healing propellant microcracks. 6 (9): 1161-1171.
Matxain J. M., Asua J. M.,Ruipérez F. J. P. C. C. P., (2016) Design of new disulfide-based organic compounds for the improvement of self-healing materials. 18 (3): 1758-1770.
Li T., Xie Z., Xu J., Weng Y.,Guo B.-H. J. E. P. J., (2018) Design of a self-healing cross-linked polyurea with dynamic cross-links based on disulfide bonds and hydrogen bonding. 107 : 249-257.
Xie F., Zhang T., Bryant P., Kurusingal V., Colwell J. M.,Laycock B. J. P. i. P. S., (2019) Degradation and stabilization of polyurethane elastomers. 90 : 211-268.
Bose R. K., Hohlbein N., Garcia S. J., Schmidt A. M.,Van Der Zwaag S. J. P. C. C. P., (2015) Connecting supramolecular bond lifetime and network mobility for scratch healing in poly (butyl acrylate) ionomers containing sodium, zinc and cobalt. 17 (3): 1697-1704.
Eom Y., Kim S. M., Lee M., Jeon H., Park J., Lee E. S., Hwang S. Y., Park J.,Oh D. X., (2021) Mechano-responsive hydrogen-bonding array of thermoplastic polyurethane elastomer captures both strength and self-healing. Nat Commun, 12 (1): 621.
Kim G., Caglayan C.,Yun G. J., (2022) Epoxy-Based Catalyst-Free Self-Healing Elastomers at Room Temperature Employing Aromatic Disulfide and Hydrogen Bonds. ACS Omega, 7 (49): 44750-44761.
Cao P. F., Li B., Hong T., Townsend J., Qiang Z., Xing K., Vogiatzis K. D., Wang Y., Mays J. W.,Sokolov A. P. J. A. F. M., (2018) Superstretchable, self‐healing polymeric elastomers with tunable properties. 28 (22): 1800741.
Jia X. Y., Mei J. F., Lai J. C., Li C. H.,You X. Z. J. M. R. C., (2016) A highly stretchable polymer that can be thermally healed at mild temperature. 37 (12): 952-956.
Ye T., Fei L., Chen X., Yin Y., Wang C. J. A. A. M.,Interfaces, (2023) Mechanoluminescent Device: In Situ Renewable Carbazole Derivatives Sandwiched by Self-Healing Disulfide-Containing Polyurethane for Mechanical Signals Detection. : .
Jin C., Sinawang G., Osaki M., Zheng Y., Yamaguchi H., Harada A.,Takashima Y. J. P., (2020) Self-healing thermoplastic polyurethane linked via host-guest interactions. 12 (6): 1393.
Huang J., Gong Z.,Chen Y. J. P., (2022) A stretchable elastomer with recyclability and shape memory assisted self-healing capabilities based on dynamic disulfide bonds. 242 : 124569.
Wang X., Zhang H., Yang B., Wang L.,Sun H. J. N. J. o. C., (2020) A colorless, transparent and self-healing polyurethane elastomer modulated by dynamic disulfide and hydrogen bonds. 44 (15): 5746-5754.
Hu Y., Tang G., Luo Y., Chi S.,Li X. J. P. C., (2021) Glycidyl azide polymer-based polyurethane vitrimers with disulfide chain extenders. 12 (28): 4072-4082.
Zhang C., Yang Z., Duong N. T., Li X., Nishiyama Y., Wu Q., Zhang R.,Sun P. J. M., (2019) Using dynamic bonds to enhance the mechanical performance: from microscopic molecular interactions to macroscopic properties. 52 (13): 5014-5025.
Wu D., Liu L., Ma Q., Dong Q., Han Y., Liu L., Zhao S., Zhang R., Wang M. J. J. o. C.,Science I., (2023) Biomimetic supramolecular polyurethane with sliding polyrotaxane and disulfide bonds for strain sensors with wide sensing range and self-healing capability. 630 : 909-920.
Prakash R.,Maiti P. J. P., (2022) The effect of chemical tagging of graphene oxide in thermoplastic polyurethane on gelation behavior. 253 : 124999.
Cai Y., Zou H., Zhou S., Chen Y.,Liang M., (2020) Room-Temperature Self-Healing Ablative Composites via Dynamic Covalent Bonds for High-Performance Applications. ACS Applied Polymer Materials, 2 (9): 3977-3987.
Menyo M. S., Hawker C. J.,Waite J. H. J. S. M., (2013) Versatile tuning of supramolecular hydrogels through metal complexation of oxidation-resistant catechol-inspired ligands. 9 (43): 10314-10323.
Yoon J. H., Kim S. M., Eom Y., Koo J. M., Cho H. W., Lee T. J., Lee K. G., Park H. J., Kim Y. K., Yoo H. J., Hwang S. Y., Park J.,Choi B. G., (2019) Extremely Fast Self-Healable Bio-Based Supramolecular Polymer for Wearable Real-Time Sweat-Monitoring Sensor. ACS Appl Mater Interfaces, 11 (49): 46165-46175.
Lin C., Wen Y., Huang X., Yang Z., Gong F., Zhao X., Hao S., Pan L., Ding L.,Li J. J. C. P. B. E., (2020) Tuning the mechanical performance efficiently of various LLM-105 based PBXs via bioinspired interfacial reinforcement of polydopamine modification. 186 : 107824.
Zhang W., Deng X., Sui G.,Yang X. J. C., (2019) Improving interfacial and mechanical properties of carbon nanotube-sized carbon fiber/epoxy composites. 145 : 629-639.
Jing T., Heng X., Jingqing T., Haozhe L., Li L., Pingyun L.,Xiaode G., (2023) Construction of a strong, fast self-healing adhesive for propellants based on the synergy of weak hydrogen bond array reorganization and disulfide exchange reactions. Polymer, 265 : .
Li Y., Yang Z., Zhao X., Zhang J., Ding L., Pan L., Lin C.,Zheng X. J. P. f. A. T., (2021) Practicable self‐healing polyurethane binder for energetic composites combining thermo‐reversible DA action and shape‐memory effect. 32 (11): 4223-4232.
Li Y., Yang Z., Zhang J., Ding L., Pan L., Huang C., Zheng X., Zeng C.,Lin C. J. P. T., (2019) Novel polyurethane with high self-healing efficiency for functional energetic composites. 76 : 82-89.

No competing interests reported.

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Development of robust and rapid self-healing polymers for the repair of microcracks in energetic composite materials

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Abstract

Figures

1. Introduction

2. Experimental section

2.1 Materials

2.2 TPU synthesis

2.3 Preparation of ECMs

2.4 General characterization

2.5 self-healing, and tensile testing

2.6 Rheology

2.7 Interfacial adhesion measurement

3 Result and discussion

3.1 Molecular design and structure characterization

3.2 Self-healing performance and mechanical properties

3.3 Rheological Properties

3.4 Adhesive properties and fracture healing ability of ECMs

Conclusions

Declarations

References

Additional Declarations

Supplementary Files

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