Characterization of Solid Propellant and its Connection to Aging Phenomena

Abstract

Solid propellant characterization has been performed with the use of three Fourier transform infrared (FT-IR) techniques: FT-IR-microscopy (FT-IR-mic), attenuated total reflectance/FT-IR (ATR/FT-IR) spectroscopy, and desorption/gas chromatography/FT-IR (D/GC/FT-IR) spectroscopy as well as thermogravimetric analysis (TGA). Emphasis was placed on examination of the content and behavior of plasticizer (bis-2,2-dinitropropyl acetal/formal, BDNPA/F) in propellant samples characterized over a 300-day period. Levels of residual solvent and other desorbable materials were examined as well. The following conclusions were made: there are significantly higher levels of both plasticizer and polymeric binder at extruded surfaces than in the interior of propellant grains; the rate of plasticizer migration in binder alone depends on the CAB:NC (cellulose acetate butyrate: nitrocellulose) ratio; and plasticizer evaporation and diffusional migration are negligible for all but one of the samples analyzed, suggesting that plasticizer is probably not responsible for observed aging phenomena. Levels of residual solvent and other minor components were observed to decrease with time under both ambient and accelerated aging conditions and may be related to aging phenomena.

Diffusion and sorption of nitroplasticizers in vinyl copolymer elastomer and its composites

“…Upon examination the isotherm curve of 100% VCE at ∼22°C, the NP sorption gives a two‐stage process, as shown in Figure (a). The similar behavior of NP adsorption by other types of polymer was reported by Pesce‐Rodriguez et al The authors were not sure whether this was due to the fact that the plasticizer was composed of two molecules, or a reflection of time‐dependent boundary condition, or both. Our results suggest that the addition of the filler into the polymer domain significantly impacts the isothermal behavior of the NP sorption.…”

Thermal stability of filler‐based ethylene/vinyl acetate/vinyl alcohol terpolymer in nitroplasticizer oxidative environment

“…Plasticizer migration is commonly encountered when it is used inside binder materials. [ 10,29–31 ] Since plasticizers are often small molecules, they display exudation even under moderate storage condition through evaporation. According to diffusion theory, for a homogeneously distributes semi‐infinite double‐sided slab of thickness l , the evaporative rate of loss of a volatile liquid can be estimated by Equation (1) [ 32 ] : where W t is the volatile content of the solid at time t , W i is the initial volatile content, W e is the volatile content in equilibrium with environment, D is the diffusivity (cm 2 /sec), t is the experiment time (sec), and l is the thickness (cm).…”

“…Plasticizer migration is commonly encountered when it is used inside binder materials. [10,[29][30][31] Since plasticizers are often small molecules, they display exudation even under moderate storage condition through evaporation. According to diffusion theory, for a homogeneously distributes semi-infinite double-sided slab of thickness l, the evaporative rate of loss of a volatile liquid can be estimated by Equation (1) [32] :…”

Theoretical Investigation of the Bond Dissociation of Hydroxyl Terminated Polybutadiene Binder and Effect on Mechanical Properties

“…超声、NMR 成像、X 射线、微观力学测试、无损探测 等方法 [6,7] , 这些方法对一些基本老化现象能给出部分 的解释. 比如, Pesce-Rodriguez 等 [8] 使用红外和热重分 析方法研究固体推进剂的老化; de la Fuente 等 [9] 通过 DSC 方法测量丁羟推进剂样品的玻璃化转变温度进行 长时间等温老化行为的分析, 以及通过动态力学方法研 究了其热老化问题 [10] ; Harris 等 [11] [12～16] , 前期我们也 对这类体系开展了弹性力学性质模拟方面的计算研 究 [17] , 而本文是从分子水平的角度对老化问题涉及的 复杂微观机理开展的又一项研究. 由于聚氨酯的热稳定 性取决于化学键的强度 [18] , 但从实验的角度研究键能 存在诸多困难, 所以通过 HTPB-TDI 交联网络的简化分 子结构模型研究化学键能及化学键断裂造成分子结构 变化对弹性力学性质的影响是另一种可行方法.…”