Preparation of anti‐migration transition layer and its application in cast‐in‐case solid rocket motors

Abstract

The polyester‐based transition layers were first synthesized with poly (diethylene glycol adipate), glycerin, and toluene diisocyanate. Then they were coated between the propellant and the liner to improve the bonding performance of the charge and inhibit the migration of the energetic plasticizer in the propellant. The effects of R value (the ratio of the quantity of isocyanate functions NCO with respect to the quantity of hydroxyl functions OH) on migration resistance and bonding performance were also studied. The overall performance was optimized at R = 1.5: after the transition layer was applied, the binding strength was greatly increased from 0.14 to 0.64 MPa, which had good application prospects. Meanwhile, due to the strong interactions between the polar ester groups and N‐butyl‐N‐nitratoethyl nitramine (NENA) in the transition layers, the portion of NENA migrating into liners were reduced from 7.6% to 6.0% (reduced by 21%), indicating that the introduction of polyester transition layers could significantly improve the anti‐migration effect. The activation energies of migration for NENA in the transition layers were about 66.3 ~ 94.3 kJ/mol, which were equivalent to the value of strong hydrogen bonding.

Influence of the Binder Structure on the Interfacial Adhesion and Antimigration Properties of the Propellant Charge

“…We have confirmed that the interaction between NENA and the polar sites of the polyester matrix is a stronger migration driving force than the concentration gradient. 20 Therefore, for the NENA migration results of the 62, 64, and 66 "homologous" polyester transition layers, our expectation is that as the content of polar groups increases, the amount of NENA migrating into the corresponding layers will gradually increase. However, the experimental result is completely in contrast to expectations.…”

“…The molar ratio of -NCO/-OH of the reactants in all transition layer formulations was 1.5 (in the polyurethane industry, the ratio is usually named R value, that is, R = 1.5) and the molar ratio of toluene diisocyanate/glycerin = 3, which is the optimized result of our previous work . When preparing the transition layer film, first, stoichiometric amounts of the polyester binder and glycerin (AR, Sarn Chemical Technology Co., Ltd.) were added to the beaker, and stirred well at 60 °C.…”

“…The adhesives should be dewatered in a vacuum drying oven at 60 °C for more than 12 h. The molar ratio of -NCO/-OH of the reactants in all transition layer formulations was 1.5 (in the polyurethane industry, the ratio is usually named R value, that is, R = 1.5) and the molar ratio of toluene diisocyanate/glycerin = 3, which is the optimized result of our previous work. 20 When preparing the transition layer film, first, stoichiometric amounts of the polyester binder and glycerin (AR, Sarn Chemical Technology Co., Ltd.) were added to the beaker, and stirred well at 60 °C. Then, a stoichiometric amount of toluene diisocyanate (TDI, Tianjin Guangfu Fine Chemical Research Institute) and 0.3 wt % catalyst (dibutyltin dilaurate/triphenylbismuth = 1:2, both diluted with dioctyl sebacate (DOS) to a solution with a concentration of 0.5% in advance; dibutyltin dilaurate and triphenylbismuth were obtained from Beijing Chemical Plant and DOS was from Luoyang Liming Chemical Research Institute) were added, stirred manually with a glass rod for 3 min, and then placed in a homogenizer, and vacuum degassed at 3000 r/m for 180 s. After the defoaming was completed, the transparent and clear transition layer slurry was poured into a polytetrafluoroethylene mold and placed in a 60 °C thermostat to cure for 7 days.…”

Enhancing the Anti-Migration Performance and Mechanical Properties of EPDM Insulation through Functionalized GO

“…Accordingly, the improvement of anti-migration properties is urgently needed. Numerous efforts have been put into hindering the migration of plasticizers [ 10 , 11 , 12 ]. Some scholars [ 10 ] tried to reduce the diffusion coefficient by adding a barrier layer.…”

Improvement in Migration Resistance of Hydroxyl-Terminated Polybutadiene (HTPB) Liners by Using Graphene Barriers

“…In order to avoid interfacial debonding, the liner is required to have certain mechanical properties, such as tensile properties and bonding properties. Zhang et al [ 28 ] used poly (adipic diethylene glycol), glycerol and toluene diisocyanate to synthesize a polyester-based transition layer, which was applied between the propellant and the liner layer. This substantially improved the bonding properties between the interfaces and effectively inhibited the migration of high-energy plasticizers.…”