Fabrication And Performances Of Fabrics Reinforced Elastomeric Insulations

EPDM is an ideal material for the insulation of solid rocket motors.It is generally necessary to add fibers,tackifying resins and functional fillers to EPDM to improve its application properties.Conventional chopped fiber reinforced ablation resistant composites have poor lateral properties,low interlaminar shear strength,and insufficient impact resistance.The ablative fabric can improve the mechanical properties and ablation resistance of the material due to its lateral and longitudinal orientation in rubber matrix.Especially for engines with long flight times,2D or 3D fabric can effectively resist the long-term erosion of high-energy particles and gases.Fiber surface treatment has a direct impact on the fiber-matrix interface and the properties of the composite.It is especially important for fiber modification.Firstly,the effects of three kinds of fabrics(PI,F-12 and CF)and fiber surface modification methods on the bonding properties between EPDM and fabric are discussed.After ultrasonic and surface etching of fiber,its specific surface area and surface energy increased,and the mechanical interlocking effect between fabric and EPDM was enhanced;Coupling agent has bridging effect between EPDM and fabric.The surface pretreatment of fiber before coupling agent can further improve the peel strength.After PI was treated with NaOH and 1.0%KH550,the peel strength between 4045 and PI reached 3.7 N/mm,and the failure mode was destruction of rubber;Adhesive could diffuse,adsorb and co-crosslink between fabric and rubber matrix.It can significantly improve the bonding performance.TDI grafting and alkali etching pretreatment of F-12 and PI before the adhesive treatment can improve active groups in surface,and the adhesive bonding effect is more obvious.Peel strengths of 4045/F-12 and 4045/PI reached 6.5 N/mm and 4.2 N/mm,respectively.Considering the bonding performance and processing property of each modification method,the fabric was modified by suitable modification method.Fabric-reinforced elastomer insulation material was prepared by vacuum bag forming.The effects of fiber type and surface modification on mechanical properties,ablation resistance and carbon layer structure of composite thermal insulation materials are discussed.After F-12 was treated by BK-40,mechanical properties were further improved,and tensile spline was not broken.Ablation performance was improved(0.108mm/s),and rubber matrix remained in the carbon layer;After PI fiber was treated by alkali etching,the imide ring was hydrolyzed,and heterocyclic resonance effect was weakened.The mechanical properties and ablation resistance were weakened.However,Adhesion properties were improved,and matrix residues were present in EPDM/PI ablated carbon layer;After PI was impregnated with BaF/4045 latex,the mechanical properties(43.1 MPa)was improved and ablative resistance(0.073 mm/s)was slightly lower.There was rubber matrix residue in EPDM/PI ablated carbon layer;CF,an inorganic fiber,has the disadvantage of large brittleness.It is easy to break during processing,so EPDM/CF tensile strength is relatively low(31.9 MPa).In addition,CF has the advantages of high temperature resistance,low density,high strength,high modulus,good anti-erosion and carbon fixation properties,so EPDM/CF has the lowest ablation rate(0.020 mm/s).However,its adhesion to EPDM is weak,there is no rubber matrix remains in the EPDM/CF ablated carbon layer.