Shengjun Zheng,Chengcheng Zeng,Jianhu Zhang,Yajun Luo,Feiyan Gong,Fude Nie
Improving the interfacial interaction between explosive crystals and the polymeric binder was essential for enhancing the mechanical properties of polymer bonded explosives (PBXs). In this study, the surface of the 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) crystal was initially coated with a polydopamine (PDA) layer, which served as an active platform for anchoring the 2-bromoisobutyryl bromide as an ATRP initiator; then, the co-polymer chains composed of Acrylonitrile(AN), 2-Hydroxyethyl methacrylate (HEMA) and 2-(Dimethylamino)ethyl methacrylate (DMAEMA) were grown through surface-initiated atom transfer radical polymerization (SI-ATRP) from the surface of TATB modified with ATRP initiator. The formation of the PDA, ATRP initiator and polymer brush coating layer on the surface of TATB was confirmed through SEM, TEM, XPS and contact angle tests. After incorporating a rigid-flexible gradient interface structure composed of PDA and polymer brush layer, the PBXs exhibited enhanced mechanical strength and creep resistance. Compared with the pristine TATB-based PBXs, the static mechanical properties, including tensile and compressive strength, of TATB@PDA@PAN-co-PHEMA-co-PDMAEMA based PBXs were increased by 36.7% and 23.9%, respectively. The maximum creep strain decreased by 39.4% at 30 °C and 14.6% at 75 °C. Additionally, the coefficient of thermal expansion decreased by 8.37%. This study presents an universal method for enhancing the mechanical properties of PBX by integrating PDA chemistry with SI-ATRP.
Xian-zhi Zhou,Cheng-cheng Zeng,Zi-jian Li,Gang Li,Sheng-jun Zheng,Fu-De Nie
Interfacial strength is a key factor affecting the mechanical properties of materials. This study aims to enhance the mechanical properties of energetic polymer bonded explosives (PBXs) by modifying 1,3,5-triamino-2,4,6-trintrobenzene (TATB) crystals—a typical energetic material—using 2-ureido-41H-6-methyl-pyrimidinone (UPy) derivatives with strong hydrogen-bonding interactions. Specifically, strongly adhesive polydopamine (PDA) was employed to graft UPy-functionalized molecules with isocyanate groups (–NCO) and hydroxyl groups (–OH). Scanning electron microscopy (SEM) images indicate that TATB crystals became rougher after being coated with PDA, while the introduction of UPy did not affect the surface morphology. The presence of urethane bond peaks in the samples indicates that UPy-NCO was successfully grafted onto the PDA. UPy is essentially nonpolar and is prone to bind with binders, having the potential to improve the creep resistance of PBXs. Due to the strong interfacial enhancement by UPy and PDA, the tensile strength and compressive strength of the sample grafted with 1 wt% UPy significantly increased by 35.6 % and 26.5 %, respectively. Theoretical calculations indicate interfacial enhancement by UPy introduction, where the strong hydrogen bonding may produce a positive impact. The successful introduction of UPy modified the nature of TATB and improved its interfacial strength, finally enhancing the mechanical properties of the PBXs. The conditions for the grafting reaction in this study are mild and universal and thus can be applied to other compositions.
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