Study of plasticizer diffusion in a solid rocket motor's bondline

Abstract

This work aims to determine the diffusion coefficient of the plasticizers dibutyl phthalate (DBP), dioctyl phthalate (DOP) and dioctyl azelate (DOZ) on the internal insulating layer of solid rocket motors. These plasticizers are originally present in the layers of rubber, liner and propellant, respectively. This species are not chemically bonded and tend to diffuse from propellant to insulating and vice versa. A computer program based on the mathematical model of Fick's second Law of diffusion was developed to perform the calculus from the concentration data obtained by gas chromatographic (GC) analyses. The samples were prepared with two different adhesive liners; one conventional (LHNA) and the other with barrier properties (LHNT). A common feature of both liners was that they were synthesized by the reaction of hydroxyl-terminated polybutadiene (HTPB) and diisocyanates. However, a bond promoter was used to increase the crosslink density of the LHNT liner and to improve its performance as barrier against the diffusion. The effects of the diffusion of the plasticizers were also investigated by hardness analyses, which were executed on samples aged at room temperature and at 80ºC. The results showed an increase trend for the samples aged at room temperature and an opposite behavior for the tests carried out at 80ºC.

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

“…Since there is no covalent bond between the plasticizer molecules and the binder system, they will migrate from the inside of the propellant to the outside under the driving force of concentration gradient, 21,22 polar interaction 23 and chemical potential gradient 24–27 . In this article, the immersion method and the sandwich method were both used to monitor the migration behavior of NENA in the DEG transition layer with different R values.…”

Influence of time on bond characteristics between extruded PVC tube and cast HTPB/IPDI rocket propellant

“…Results of investigation of freshly prepared and aged specimen showed the softening of the propellant on the layer located at 3 mm from the bondline. The changes can cause damages mainly to the bondline, thereby affecting the performance and security of the rocket motor [24].…”

Anti‐migration performance of EPDM composite improved by octadecylamine‐functionalized graphene oxide

“…The use of insulation enables the motor case from erosion by high‐temperature particles and gas flow generated during propellant burning 1 . In order to increase the flexibility of insulation and improve the mechanical properties of propellants, 2,3 plasticizers are used. Most of these plasticizers are esters compatible with nitroglycerin (NG) and nitrocellulose (NC), such as dioctyl phthalate (DOP), dioctyl adipate (DOA), dibutyl phthalate (DBP), and so forth 2 .…”