Building Of Epdm And Nbr Composite Insulations And Optimization Of Their Properties Of Surface And Interfaces

EPDM/NBR composite insulation layer（EPDM/NBR）is composed of EPDM and NBR insulation layer,which possess the bonding stability of nitrile matrix insulation layer and engine shell,and also integrates the low density,high filling coefficient and good compatibility with propellant of EPDM insulation layer.As a new type of internal insulation material matrix,EPDM/NBR composite insulation layer expands the application space for EPDM and NBR insulation materials,which is conducive to the development of high-performance solid rocket motor.In this paper,the co-vulcanization behavior of the vulcanization system between different substrates was explored by means of blending.The study showed that the vulcanization synchronization of the composite rubber could be improved when only sulfur（S）vulcanization was used with n-cyclohexyl-2-benzothiazole sulfonamide（CZ）as a promoter,and the tensile strength of the composite rubber reached 10.6 MPa with 62.8%co-vulcanization value.And with the increase of CZ contents,the tensile strength gradually became worse.The proportion of double continuous phase structure and island structure of composite rubber vary with the change of vulcanization systems,and the co-vulcanization performance could be significantly improved when DCP and S was used to vulcanizate.It was found that the composite vulcanization system using diisopropyl peroxide（DCP）with S vulcanization could significantly improve the co-vulcanization of the two phases.The influence of covulcanization behavior of EPDM/NBR composite rubber was explored by adding different compatibilizers,and the result shown that g-EPDM and BIIR can improve the compatibility of the blended adhesive.The g-EPDM have the effect of both volume enhancement and plasticization,and is beneficial to form compact structure inside the blended adhesive.The best effect was obtained when the contents was 6 parts.The covulcanization behavior and properties of EPDM/NBR composite rubber were also discussed when different ablation-resistant fillers and adhesive were added.It is found that fiber can improve the binding effect of EPDM phase and NBR phase,breaking the original phase and improving the compatibility.However,it is easy to produce defects,resulting in low mechanical properties.Boron-modified phenolic resin and flame retardant could produce acid,which influence the degree of covulcanization to some extent,and the flame retardant has a greater influence and obviously reduce the degree of covulcanization.The influence of the forming process of composite insulation layer on the performance of the interlayer interface is studied,and the influence of the interface performance under the ablation test is analyzed.The composite ablative insulation layers with different formulations and processes were prepared and the ablative performance were tested.The results shown that the composite insulation layers after vulcanizing of TMTD and CZ can maintain the stability of the interface during the ablative process.After adding g-EPDM and BIIR respectively,the composite insulation layer could all form a composite carbon layer without falling off during ablation with 0.0731 mm·s^-1 linear ablation rates,respectively.BIIR is more conducive to the interpenetration of the composite insulation layer interface,however,the influence on the interface interpenetration is limited when the holding temperature was increased merely.The use of nitrile thermoset phenolic adhesive can form a stable interface structure between the two insulation layers,and improve the interface and comprehensive performance.With the increase of g-EPDM contents,the ablation performance of materials is obviously improved.When the g-EPDM contents is 10 parts,the interlayer interface of the composite insulation layer is best,and the ablation performance is optimal with 0.0719 mm·s^-1 linear ablation rate.