Enhanced Creep Resistance and Mechanical Properties for CL‐20 and FOX‐7 based PBXs by Crystal Surface Modification

Abstract

Interfacial strength between energetic crystal and polymeric binder is of a great significance to the mechanical strength and other performances of polymer bonded explosives (PBXs). In this paper, hexanitrohexaazaisowurtzitane (CL‐20) and 1,1‐diamino‐2,2‐ dinitroethylene (FOX‐7) were chosen to study the thermal and mechanical properties of corresponding PBXs. The energetic crystals were firstly modified with polydopamine (PDA) and further coated with the hyperbranched polymer (HBP). The results showed that CL‐20@PDA achieved a noticeable retardation of 11 °C for the phase transition, due to the constraint of PDA shell, and the thermal decomposition of CL‐20 was slightly delayed. The storage modulus of CL‐20 based PBXs were improved. In addition, the tensile strength and compressive strength were increased by 22.9 % and 25.4 %, respectively. Concomitantly, the fracture failure temperature of FOX‐7 based PBXs composites after surface coating were increased, with its tensile and compressive strength increased by 33.1 % and 15.2 %, respectively. Moreover, the creep resistance of the two PBXs composites with surface modification was obviously enhanced.

Study on Mechanical Improvement of CL‐20 Energetic Co‐Crystals Based PBX by Surface Modification

“…The preparation of CM was reported detailly in the previous works [26][27]. The specific steps of coating CM with dopamine can refer to the literature [18], with a coating time of 6 h, and the CM-P was named to represent CL-20@PDA. NBA and Estane need to be dissolved into acetone solution and dichloromethane solution re- spectively before use.…”

“…Meanwhile, dopamine has characteristic of strong adhesion, forming "physical anchor" and π-π bond to enhance the interfacial strength [19]. The surface modification mainly focused on TATB and HMX in the past few years, and some literatures studied that PDA coating can postpone phase transformation of CL-20 to increase stability [20][21][22][23]. Accordingly, for CL-20 series co-crystals, the focus mainly lied in synthesis route, molecular structure characterization, simulation calculation and so on.…”

“…However, as small organic molecules, low surface energy of explosives is difficult to be completely wetted by binders, thus low interfacial work may affect the mechanical properties of PBX. In the early stage, it is verified that the introduction of NBA or biomimetic coating has many advantages in enhancing the interface bonding between explosive and binder [17][18]. NBA carrying specific functional group plays as a "bridge", which can effectively enhance the wetting and spreading of binder on the surface of explosive crystals, so as to improving the mechanical strength.…”

The Auto‐Ignition Behaviors and Thermal Safety of the Composite Modified Double Base Propellants under Rapid Heating

“…When CMDB including RDX or HMX is subjected to external stimulus, there is still a high risk of unexpected ignition or explosion in production, transportation, storage, and application [12]. Therefore, a novel material, 1,1-diamino-2,2-dinitroethene (FOX-7), whose detonation performance is similar to RDX but sensitivity towards impact and fraction matches 2,4,6-trinitrotoluene (TNT) attracted considerable attention [13][14][15]. In order to improve the sensitivity of CMDB including RDX, FOX-7 can be added.…”

Preparation of PDA@AP composite particles by two‐step method and its application in glycidyl azide polymer‐energetic thermoplastic elastomer propellants

“…Since then, PDA has been used more and more to modify explosives. Gong and her team used PDA to coat HMX, 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB), 1,1‐diamino‐2,2‐ dinitroethylene (FOX‐7), and other nitramine explosives and used them in PBXs, significantly improving the mechanical properties of PBXs 9–14 . Qu et al 15 used PDA to coat RDX, and then loaded lead atoms on the surface of PDA and used it in solid propellant, which successfully improved the burning rate of propellant.…”