Research On Rheological Properties Of GAP-based ETPE Propellant

The rheological properties of composite propellant is closely related to the forming process of composite propellant.As the"heart"of the propellant,the binder makes different solid loadings combine closely,which endows the propellant with certain plasticity.Therefore,the rheological properties of the binder are also closely related to the forming process of the propellant.The rheological properties of composite propellant and its binder can provide theoretical basis for the propellant forming process.It can be used for designing formulation of propellant,the optimum processing conditions of composite propellant,the design and improvement of the forming process equipment.Glycidyl azide polymer based energetic thermoplastic elastomer polyurethane?GAP-ETPE?as a kind of binder was prepared in this work.The binder was modified with nitrocellulose?NC?and energetic plasticizer butyl ethyl nitrate nitramine?Bu-NENA?to obtain ETPE/NC and ETPE/NC/NENA binder systems.The RDX and Al were introdued into the modified binder.Finally the ETPE/NC/NENA/Al,ETPE/NC/NENA/RDX model propellant and?ETPE/NC/NENA?/Al/RDX propellant were obtained.Then the basic properties of the prepared binders and propellants were tested,and their rheological properties were studied by dynamic rheological method.?1?The effects of hard segment content on the basic properties of GAP-ETPE and the linear,non-linear and heat reological behavior of ETPE were investigated.It was found that with the increasing of hard segment content in ETPE,the physical crosslinking density,the maximum tensile strength,the storage modulus?G??,loss modulus?G??and complex viscosity??*?of ETPE increased,while the elongation at break and the critical shear strain decreased.It was found that G?of ETPE increased rapidly in the low frequency region and increased slowly in the high frequency region in the master curve of G?of ETPE obtained by the time-temperature principle.It was also found the"second platform"in the low frequency region,which is usually exsited in filled polymer.The results also showed that the viscous flow activation energy of ETPE obtained by Arrhenius equation increased with the increasing of hard segment content of ETPE.?2?The basic properties and rheological properties of ETPE/NC binder were investigated.The results showed that the physical crosslinking density,mechanical strength,G?,G?and?*of ETPE/NC binder increased with the increasing NC content.But it was found a peak value when the content of NC is 10%.Moreover,it also found that the phase of ETPE/NC binder changed from dispersed phase to co-continuous when NC content is 30%.And the fiber NC was found in binder.It was also found that the viscoelastic behavior of ETPE/NC binder can be well fitted two-phase model.?3?The basic properties and rheological properties of modified ETPE/NC/NENA biner were studied.It was found that the physical crosslinking density,mechanical strength,G?,G?,?*and the glass transition temperature of ETPE/NC/NENA binder decreased significantly with the increasing of NENA content.By constructing the master curve,the viscous flow activation energy obtained by the Arrhenius equation and zero shear viscosity obtained by Cross equation of binder decreased with the increasing of NENA content.The results also showed that compatibility of ETPE and NC become well with the increase of the content of NENA and then change significantly when the content of NENA is 25%.ETPE and NC can not be distinguished on the brittle fracture surface of binder when the content of NENA increased 25%.?4?The effects of RDX and Al on the properties of ETPE/NC/NENA/RDX and ETPE/NC/NENA/Al model propellants were investigated.It was found that with the increasing of the content of RDX and Al and the decreasing of the particle size,the crosslinking density of the composite increased.With the addation of Al,the mechanical properties of the model propellants became well,while the RDX had a negative effect on the mechanical properties of the model propellant.It was also found that the G?,G?and?*of Al based model propellants increased with the increasing of Al content and decreasing of size of Al particle.So was the RDX based model propellants.But with a little addation of RDX,the G?,G?and?*of RDX based model propellants decreased after 100°C.The linear viscoelastic behavior of model propellants can be described well by the two-phase model.Compared with RDX based model propellant,the strain amplification factor A_f and the elastic contribution value^?₁)??of Al based model propellant were high.The A_f and^?₁)??of model propellants increased exponentially with the increasing of sold loadings.?5?The basic properties and rheological properties of GAP-ETPE propellant with ETPE/NC/NENA as binder,RDX and Al as loadings were studied.The results showed that with the increasing of the solid loading content,the maximum tensile strength of the propellant increased,the broken elongation of the propellant decreased.When the content of binder is fixed,the maximum tensile strength of the propellant decresed the increasing of Al content.It was found that all the propellant exhibited pseudoplastic fluid characteristics at60¹00°C,and the viscosity of the propellant was above 10⁴ Pa s.The viscosity or stress of propellant decreased with the increasing of temperature,and increased with the increasing of solid loading content.At low shear rate,the viscosity of propellant had a high sensitivity to the solid loading content of propellant.And the higher the solid loading content was,the more sensitive of the propellant viscosity to the force was.The viscous activation energy of the propellant was decreased with the increasing of the solid loading content.When the binder content was greater than 25%,the viscosity and stress of the propellant decrease obviously.When the content of binder is fixed,the viscosity of the propellant increased by the increasing of Al content.While the activation energy of the viscous flow was not mostly changed hardly promoted.Compared with RDX,the effect of the same content changing of Al on the viscosity and stress of propellant was more obvious.