Study On Toughening Of RP5 Nitramine Premix Material By Three-arm PEG/THF Block Star Copolyether

Aiming at improving the impact resistance of nitramine propellants,RP5 nitramine premix material were used as the raw material,adding separately with three-arm PEG/THF block star copolyethers of different number average molecular weights,for example,the number-average molecular weight are10243,12150,and 13892 separately,as toughening agents.The alcohol and acetone solvent 1:1 was used as the solvent.Then,a RP5 sample containing different molecular weights and different contents of three-arm PEG/THF block star copolyethers was prepared by a kneader kneading method,and then using the basically same pressure press them into pipes.After that,make them dried uniformly.The dropped weight impact test and pendulum impact test method were used to the propellant samples to figure out the impact strength of RP5 samples with different molecular weights of three-arm PEG/THF block star copolyethers under different temperatures.The impact strength was measured both in the radial direction and in the axial direction.The contact angle measurement method was used to study the surface energy change at room temperature.The impact resistance test of RP5 specimens was analyzed by several toughening mechanisms to find the suitable toughening mechanism for RP5 specimens.The main findings of this paper are as follows:(1)During the process of compressing the pharmaceutical material,the macromolecule chains will be oriented along the direction of the force,so the test results of the radial and axial mechanical properties of the propellant samples showed different results changing.(2)In the radial pendulum impact test of the RP5 sample,the good toughening effect is shown at-40? and 20?,respectively.The impact resistance of RP5 samples with three different molecular weights and different contents of three-arm PEG/THF block star copolyethers was significantly improved at-40?.In the pendulum tests at-40?,when the polyether molecular weight is 12150 and the content is 2%,the sample has greater impact strength and toughening effect.At 20?,when the polyether molecular weight is 10243 andthe content is 2%,the sample has greater impact strength and toughening effect.When choosing the toughening agent,both the molecular weight of the toughening agent and the content added affect the mechanical properties of the propellant.A suitable toughening agent can improve the mechanical properties of the propellant.(3)In the axial drop impact test of the propellant sample,the axial volumetric impact energy of the sample gradually decreases with the increasing temperatures,which means that the impact strength of the propellant increases as the temperature increases.At the temperature of-40? and 20?,when the molecular weight of the three-arm PEG/THF block star copolyether is 10243,the toughening effect of the RP5 sample is comparatively good,and the impact strength of the propellant is enhanced greatly.At 50?,when the molecular weight of the three-arm PEG/THF block star copolyether is12510,it was added to the RP5 sample and the content was 2%,the axial impact strength of the propellant reached the maximum figure,and the toughening effect is the most significant one.(4)The surface energies of three-arm PEG/THF block copolymers RP5 sample with different molecular weights and different contents were calculated by measuring the contact angles.Compared with the drop hammer impact test results at 20?,the result showed that the surface energy of the RP5 sample has the same trend as the volumetric impact energy curve of the dropping hammer impact tests----as the surface energy of the RP5 sample matrix decreases,the volume impact energy of the RP5 sample decreases as well.At this temperature,with the increase of the polyether content,the surface energy of RP5 sample of same molecular decreased,so did the the volume deformation impact work of the RP5 sample,meaning the impact strength increased.(5)Through analysis of the toughening mechanism of several rubber toughened polymer systems on the impact resistance of RP5 specimens,it was found that the multiple silvering theory,the shear yield theory and the shear yielding-craze theory can be more appropriate to explain the toughening effect of 3b-copolyether on RP5 specimens.