Development and testing of dicyclopentadiene based solid composite propellants

Dicyclopentadiene (DCPD) is a polymer that undergoes ring opening metathesis polymerization to form a strong, highly cross-linked polymer with a high fracture toughness and low elasticity. While these characteristics differ from modern propellant binders, this research shows that DCPD is highly susceptible to favorable changes in mechanical properties through the addition of both plasticizers and copolymers. Gumstock DCPD was tested to determine appropriate inhibitor levels to accurately predict the pot life of propellant mixtures. A variety of plasticizers and copolymers were tested to determine how their addition would affect not only mechanical properties, but combustion characteristics as well. While 2-ethylhexyl acrylate showed excellent plasticizing capabilities, poor aging qualities necessitated the switch to the less effective dioctyl phthalate plasticzer. The low viscosity of DCPD allows for quick and easy wetting and mixing of solid particles. Changes in the solid oxidizer distribution from previous work has lead to the successful implementation of 85% solids with compelling results indicating the possibility of higher loadings. The use of modern casting techniques has lead to a higher level of propellant casting quality, providing a low void homogeneous final product. Strand burn experiments and ballistic motor firings show that DCPD burning rates are double that of identically loaded hydroxyl terminated polybutadiene based propellants, this is achieved through a relatively high pressure exponent term. The addition of dioctyl phthalate as a plasticizer effectively reduces the pressure exponent while at the same time increasing the burn rate at pressures below 1250 psi. The high burning rate of DCPD coupled with the ability to tailor mechanical and burn rate properties, makes it exceptionally versatile for use in a variety of propulsion systems. Despite decreases in strength at higher solids loadings, the ease of processing makes DCPD a viable composite binder alternative