Reparation Of Epdm Insulations And Adaptation To Engineering Application Performance

EPDM insulations is a kind of high temperature resistant particle erosion material prepared by mixing EPDM as the matrix,adding other fillers such as ablation resistant fibers and flame retardants.It is widely used in solid rocket motors due to its advantages of good performance and large filling factor.However,EPDM thermal insulation materials still have disadvantages in application,for example: 1)The optimum molding process conditions for some epoxy resin composites are 140～150°C,which is not suitable for traditional EPDM vulcanization temperature(160°C).The performance of EPDM has a certain influence,that is,the macroscopic performance of EPDM thermal insulation material is under-vulcanization;2)EPDM is a non-polar material and has poor adhesion between polar metal shells;3)The carbon layer formed by the EPDM insulation after being impacted by high temperature particles is not compact and easy to fall off.This paper explores the vulcanization system of EPDM insulations,adjusts the types of vulcanizing agents,accelerators and co-crosslinking agents,so that EPDM insulation can be fully vulcanized at 140 ℃ and meet the conditions of using.Experiments show that the peroxide vulcanization system has problems such as vulcanization slowly and low vulcanization degree.The EPDM insulations with S and DCP as the composite vulcanizing agent and TRA as the accelerator has better performance.And based on this formula,the grades of EPDM are optimized.The results show that the S501 A has the best performance,the tensile strength,shore hardness,density;linear ablation rate reach16.4MPa;56A;1.09g/cm;0.055mm/s respectively and the elongation at break is close to 600%To improve the poor adhesion caused by the non-polar characteristics of EPDM,EPDM was grafted and polarized by polar monomer in internal mixer and fellow by a single screw extruder processing.The modified EPDM(g-EPDM)with different grafting ratios were prepared,and the effects of g-EPDM on properties of EPDM insulations were studied.The results shows that the increase of the grafting rate of g-EPDM or the increase of its addition could improved the bonding strength of EPDM insulation materials.When the addition of g-EPDM is 30 phr,the grafting rate of g-EPDM is 3.05‰,the EPDM insulation has shown excellent processing performance,and its bonding performance with aluminum sheet is 3.8 MPa,which is 79.2% higher than that of EPDM insulation without any modification of g-EPDM.When the addition amount of 3.05‰-g-EPDM is 15 phr,the tensile strength,elongation at break,bonging strength with aluminum sheet,and linear ablation rate reach 11.4 MPa;523%;3.06 MPa and0.058mm/s,respectively.The effects of different types of fibers,flame retardants,silicates,and their additions on the properties of EPDM insulations were investigated.Experiments show that in the system of AF and PI-pulp compound,with the increase of PI-pulp addition,the mechanical properties of EPDM insulations are enhanced,from the EPDM insulation.Considering the comprehensive performance and cost,a compound system with 4 parts of PI-pulp and 6 parts of AF is selected.Flame retardants and silicates can reduce the linear ablation rate of EPDM insulation materials when they reach a certain amount,and the bonding performance between EPDM insulations and steel sheets with MH and wollastonite respectively has been significantly improved,reached 5MPa and 4.8MPa,respectively.