The effect of reactive plasticizer on viscoelastic and mechanical properties of solid rocket propellants based on different types of HTPB resin

Abstract

Conventional plasticizers deteriorate mechanical and viscoelastic properties of the propellants due to their migration upon aging and long-term storage, which affects reliability and safety properties during exploitation. To address this issue, conventional plasticizer, dioctyl adipate (DOA), is replaced by reactive one, castor oil (CO). In addition, three different types of HTPB were used to obtain propellants with designed viscoelastic and mechanical properties. The CO increased propellants viscosity, without a significant impact on the propellant processability, regardless to the type of prepolymer. Conversely, mechanical properties were different depending on the type of resin, which were further analyzed by gel permeation chromatography (GPC). Addition of CO formed a denser polymer network and shifted Tg to higher values, compared to the compositions with DOA. The tensile strength of CO-containing propellants was lower at +20 °C and +50 °C compared to the reference compositions, while the strain at maximum load and strain at break were significantly increased with pronounced plastic deformation, especially for samples at −30 °C. The inclusion of CO in the propellants composition gives more room for adjusting a wide range of mechanical properties.

Keywords

• HTPB-based composite propellants
• Castor oil
• Reactive plasticizer
• Gel permeation chromatography
• Sol-gel analysis
• Mechanical and viscoelastic properties